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3 DESIGN CRITERIA

The design criteria section discusses the design parameters to be carried forward into final design.

3.1 Hydraulics Design

Flow rates used for preliminary design were obtained from the CSO Program InfoWorks hydraulic model. Flow rates within conduits were designed to maintain an average dry weather flow velocity of 2 ft/s to facilitate sediment transport.

Various locations were evaluated for construction of each diversion structure. The hydraulics of the system was considered for each location. Diversion structures are located to intercept flows contributing to the existing racks.

3.1.1 Existing Sewer Rehabilitation

The existing sewer system requires rehabilitation within selected areas to achieve the OCI Tunnel project requirements. Based on the CCTV inspections discussed in Section 2.6, preliminary rehabilitation recommendations for the areas in greatest distress were developed. Five areas were recommended for repair. Three of the repairs would be performed as part of another rehabilitation project. Repairs to be designed and constructed as part of the OCIT-2 final design consist of Cured-In-Place Pipe (CIPP) lining the two remaining segments. Repair of these segments is important to maximize flow conveyance through existing sewers intended to remain in use after the OCI Tunnel is constructed. Refer to the OCI Sewer Condition Assessment Report in PER Appendix M for more information.

An evaluation was performed on the OCI downstream of Rack 19 to see if the existing sewer could be abandoned up to its connection with the LCI. Access to this stretch of sewer is very difficult due to many manhole access locations being located within the Ohio Canal. The OCI between Rack 19 and the connection to the LCI contains five local sanitary connections and two storm sewer connections. As a result of O&M difficulties, the City would prefer that the existing OCI be abandoned and a parallel pipe be constructed outside of the Ohio Canal in order to convey the local service connections. Potential options for conveying the few remaining connections are listed below.

Abandon the existing OCI and construct a new smaller diameter sewer parallel to the Ohio Canal to convey the service connections.

Construct a new smaller diameter sewer within the existing sewer to convey the service connections.

Inspect the existing sewer after OCI Tunnel construction is complete. Flows from Racks 4, 16, 17, 18, 19, and 37 would be removed from the existing OCI and CCTV inspections may be easier. Inspection after OCI Tunnel construction is complete could result in different repair recommendations and lining extents. This would conflict with the Program Capacity, Management, Operations, and Maintenance (CMOM) requirement of inspecting the sewer once every five years. Service connections would continue to be conveyed in the existing sewer to the

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LCI. The existing sewer could also provide a channel for tunnel dry weather flows if maintenance is needed within the OCI Tunnel.

3.1.2 Rack Modifications

Existing rack structures should be modified during construction of the diversion structures. Racks 4, 16, 17, 18, and 37 should be modified to facilitate the addition of proposed diversion structures. The racks should be removed, sealed, and abandoned, and the downstream weir walls should be removed. Future maintenance should not be required at these locations.

Racks 4, 16, and 17 should be sealed to eliminate the existing OCI connection. Dry weather and wet weather flow would flow past the sealed rack and continue through the existing overflow pipe to a newly constructed diversion structure. Flows from Racks 16 and 17 would be combined at one diversion structure. Flows from Rack 4 and 37 should be intercepted in new diversion structures and should be conveyed into the OCI at new connection points. The underflow of Rack 18 should also be sealed from the OCI; however, the proposed diversion structure should be constructed upstream from the existing rack, so the remaining overflow pipe would convey overflow from the diversion structure, past Rack 19, and into the Ohio Canal Enclosure.

Rack 19 overflow would be relocated upstream of existing rack connection to the Ohio Canal. The new overflow connection is proposed to be located upstream of the existing Rack 19 connection to the Ohio Canal. Between these locations, the enclosure has a constant 0.1% slope. No adverse impacts are anticipated as the new connection would be subject to nearly the same hydraulic grade line. Existing Rack 19 underflow and outfall pipe can be abandoned up to the new connection along Market Street.

Racks 20/23/24 Overflow Eliminations

Racks 20, 23, and 24 could be eliminated from the existing combined sewer system. Flows contributing to these racks should be intercepted upstream of the racks and consolidated into a new system. The consolidated flows should be conveyed to the diversion structure at the end of the OCI Tunnel.

3.2 Vertical and Horizontal Tunnel Alignment

As a result of the tunnel alignment selection workshops, one preferred alignment corridor was selected. In general, the corridor extended from the Akron Children’s Hospital (ACH) parking lot at Exchange and Dart Streets, northeast under Dart Street, across S.R. 59 to Rand Street, past Market Street, north underneath the St. Vincent-St. Mary High School football field, and northwest to extend to existing City of Akron property north of Hickory Street and west of Maple Street. This corridor was preferred because it maximized the amount of rock cover over the tunnel, minimizes necessary land purchases, allowed for good shaft locations for future tunnel maintenance activities, and generally minimizes the required consolidation sewer lengths for Racks 4, 18, 19, 20, 23, and 24. The Rack 16-17 Consolidation Sewer distance was directly related to the preferred OCIT-3 shaft location. After the alignment corridor was selected, a tunnel alignment with a minimal number of curves was drawn. This alignment was then adjusted to avoid specific properties, maintain offsets from railroad bridges, avoid existing bridge footings and abutments, and facilitate access for long-term maintenance

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shaft locations. Figure 3-1 shows the constraints considered for adjustments made to the tunnel alignment.

The upstream end of the final tunnel alignment starts in the southwest corner of the ACH parking lot at the intersection of Exchange Street and Dart Avenue. The alignment heads straight from the shaft to the east edge of the Locust Street Bridge, crossing S.R. 59. The alignment follows a 1000 foot radius curve to the northwest in order to cross S.R. 59 and continues north along Rand Street to Market Street. The alignment then follows another 1000 foot curve to the west and crosses under St. Vincent St. Mary’s football field. After passing below the Wheeling and Lake Erie Railroad at a point about 50 feet west of the existing railroad bridge structure, the alignment continues in a straight line to the termination point at the selected EHRT Site north of Hickory Street.

The OCI Tunnel is approximately 6,136 feet long and should have an internal diameter of 27 feet. The downstream invert elevation of the tunnel must be constructed at elevation 800 or higher so the entire tunnel can be dewatered by gravity to either the future EHRT or the existing LCI. The tunnel slope is 0.15%, which should result in dry weather flow velocities of 2 feet per second or greater. As a result of the slope, the upstream invert elevation is approximately Elevation 810. Design drawings showing the plan and profile of the tunnel are included in the drawing package as part of PER Appendix A.

SR59

MAI

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RAND

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MAPLE

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400 0 400200

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LegendOCIT-4B

Location Constraints

Shaft Sites

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Ohio Canal Interceptor Tunnel

Alignment Constraints Figure 3-1

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Newly Developed Homes

Roadway Retaining

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DifficultProperty

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Wheeling and Lake Erie Railroad Bridge Abutment

Properties with existing leins

Market Street Bridge Abutment

Diamond Grill Restaurant

Importance tothe City

Future Redevelopment Site

ODOT S.R. 59 Bridge Abutments

Future ACH Expansion Site

St. Vincent St. Mary Football Field (above dump site - limits unknown)

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3.3 Near Surface Structures

Near surface structures would be constructed to intercept flows from existing rack structures, convey required flows to the OCI Tunnel, and to provide for overflow relief for flows greater than the design criteria. These structures are an integral part of the system. Diversion structures, junction chambers, and drop shafts are examples of near surface structures incorporated into the design. Each structure was evaluated with regards to location, constructability, conveyance, and feasibility.

3.3.1 Flow Conveyance Requirements

Racks 16, 17, 18, 19, 20, 23, and 24 are proposed to be controlled up to the 10-year 1-hour storm. To meet this design criterion, flow entering each rack structure up to the peak flow rate for the 10-year 1-hour design storm would be conveyed to the OCI Tunnel. Storms generating flow rates above this peak flow rate would continue to overflow at the existing Rack outlet or through a new outlet connected to the Ohio Canal. Racks 4 and 37 would be controlled to zero overflows based on the 1994 adjusted typical year flow. Storms generating flow rates greater than the peak typical year flow rate would continue to overflow to the Ohio Canal at Racks 4 and 37. Table 3-1 includes rack design flow rates for dry and wet weather.

Table 3-1 Rack Design Flow Rates

Rack DesignStorm

Wet Weather Flow Rate (MGD)

Dry Weather Flow Rate (MGD)

Rack 4 Typical Year 34 0.6 Rack 16 10-Year 285 3.3 Rack 17 10-Year 449 0.3 Rack 18 10-Year 477 13 Rack 19 10-Year 74 0.3 Rack 20 10-Year 40 0.08 Rack 23 10-Year 41 0.06 Rack 24 10-Year 325 1.65 Rack 37 Typical Year 12 0.8

The OCI Tunnel is currently designed to convey both dry and wet weather flows to the OCIT-1 site and capture and store a minimum of 25.6 million gallons of CSO during wet weather events. This storage volume is sufficient to fully capture overflow from the 8th largest storm during the typical year. As a result, larger storm events or sequential events would overflow to the Little Cuyahoga River from the tunnel. Overflows from the tunnel are expected to occur for seven or fewer events during a typical year.

The OCI Tunnel has been designed with a 0.15% slope. This slope would allow average dry weather flow from Racks 16 and 17, the most upstream contributing racks, to be conveyed at a velocity of 2 ft/s without modifications of the tunnel invert. Additional dry weather flow from Racks 18 and 19 would increase average flow velocity in the tunnel to 3 ft/s downstream of OCIT-2.

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3.3.2 OCIT-1 Area (Racks 20/23/24)

Dry weather and wet weather flow from Racks 20, 23 and 24 would be intercepted upstream of the existing rack structures and conveyed to the Hickory Street Junction Chamber. The junction chamber combines the three flows and directs it to the OCIT-1 Diversion Structure, which is located at the downstream end of the OCI Tunnel. Dry weather flow from Racks 20, 23 and 24 combines with other dry weather flow from the tunnel in the diversion structure and discharges to the LCI. Wet weather flows from Racks 20, 23 and 24 discharges to the OCI Tunnel.

Minimum design criterion is to intercept the peak 10-year 1-hour design storm flow. At this design level, the tributary collection system upstream of the racks is operating at nearly maximum capacity. Therefore, the new consolidation sewer system is designed to convey maximum full-flow delivery capacity of the collection system pipes tributary to the Racks. The sum of peak 10-year 1-hour flow rates from Racks 20, 23 and 24 is approximately 406 MGD. The sum of maximum full-flow total delivery capacity is 468 MGD.

For flows normally conveyed to Rack 20, a new 42’’ pipe would be installed along the south side of Hickory Street. The Hickory Street sewer would intercept flow at the intersection of Walnut and North Streets.

Flows normally conveyed to Rack 23 would be intercepted by a new 54-inch pipe and conveyed to the Hickory Street Sewer at STA 12+00. The combined Rack 20 and 23 flows would be conveyed west in a 66-inch pipe to a junction chamber to be built near the intersection of Hickory Street and the Cuyahoga Valley Scenic Railroad.

Flows normally conveyed to Rack 24 would be intercepted from the existing 63-inch brick sewer extending between Tarbell and Hickory Streets. Intercepted flows would be conveyed in a 108-inch inside diameter pipe to the new junction chamber discussed above and combined with flows from Racks 20 and 23. The 108-inch I.D. pipe would need to be tunneled under the Wheeling and Lake Erie Railroad tracks. Combined flows from the new junction structure would be conveyed through a proposed 120’’ pipe to discharge into the OCIT-1 Diversion Structure at the end of the OCI Tunnel.

Construction of the OCIT-1 consolidation sewers would need to be carefully sequenced with the OCI Tunnel construction because the current conveyance pipes conflict with the main tunnel bore. Figure 3-2 shows the consolidation sewers, junction chamber, and diversion chamber for the OCIT-1 area.

Figure 3-X

Ohio Canal Interceptor TunnelOCIT-1 Area Proposed Structures Layout

Figure 3-2

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3.3.3 OCIT-2 Area (Racks 18/19)

The OCIT-2 Consolidation Sewer area contains structures which collect and regulate dry and wet weather flows from CSO basin areas 4, 18, 19, 37, and 39. Although the current Racks 18 and 19 are both on the east side of S.R. 59, by utilizing two separate diversion structures on opposite sides of S.R. 59, the City should be able to minimize the size of the Rack 19 Consolidation Sewer. The Rack 19 Consolidation Sewer must cross underneath the existing Ohio Canal Enclosure and S.R. 59. Figure 3-3 shows the consolidation sewers, drop shafts, and diversion chamber for the OCIT-2 area.

Diversion structures in the OCIT-2 area would utilize a weir to direct both dry and wet weather flows to an orifice, which regulates the total flows sent to the OCI Tunnel. The diversion structures are designed to allow up to the 10-year, 1-hour storm flows to reach the OCIT-2 Drop Shaft. Excess wet weather flows would be diverted to an overflow connection to the Ohio Canal Enclosure. Rack 18 and Rack 19 Diversion Structures combined would convey flow up to 550 MGD of wet weather flow to the OCI Tunnel. Flows from Rack 18 and Rack 19 Diversion Structures would enter the OCIT-2 Drop Shaft by separate consolidation sewers and at different elevations.

Rack 18 Diversion Structure

Rack 18 Diversion Structure is designed to regulate flow from two (2) existing sewers contributing to Rack 18. The larger sewer is the Willow Run Trunk Sewer, which extends west to east along the south side of Glendale Avenue. The second contributing sewer is an existing 30-inch combined sewer extending north-south along the east side of Rand Street.

Rack 18 Diversion Structure would be built in line with the Willow Run Trunk Sewer. A new 36-inch sewer would be constructed to convey flow from the 30-inch sewer to the Rack 18 Diversion Structure.

Within the diversion structure, a weir would direct dry weather and wet weather flows up to the 10-year, 1-hour storm level into a 72” x 72” orifice. The orifice is designed to allow up to 477 MGD of flow to be discharged from the Rack 18 Diversion Structure, into a new 120-inch consolidation sewer, and into the OCIT-2 drop shaft.

Flows greater than 477 MGD would overflow the Rack 18 Diversion Structure weir and continue in the existing Willow Run Trunk Sewer. Flows would then be screened and discharge at the current Rack 18 overflow point on the Ohio Canal.

Rack 19 Diversion Structure and Drop Shaft

Rack 19 Diversion Structure would be designed to regulate flows from Rack 19 basin areas. Typical year flows from Racks 4 and 37 would join Rack 19 flows downstream of the diversion structure. Regulated flows would be directed to Rack 19 Drop Shaft, into a tunneled sewer extending beneath S.R. 59, and into the OCIT-2 Drop Shaft. The following paragraphs describe the Rack 19 Diversion Structure system in detail.

Rack 4 is located near the southwest corner of the Superblock parking garage on Mill Street. The existing rack is proposed to be disconnected from the underflow pipe to direct flows into the existing 60-inch overflow pipe. A new diversion structure is

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proposed on the existing 60-inch overflow pipe at a point downstream of the existing Rack location. The proposed Rack 4 diversion structure would convey dry weather and adjusted 1994 typical year storm flows (up to approximately 34 MGD) to a new 42-inch pipe connecting to the existing OCI. Flows greater than the adjusted typical year storm flow would continue west in the existing Rack 4 overflow pipe and into the Ohio Canal. Figure 3-4 shows the proposed Rack 4 diversion chamber and proposed connection to the OCI.

Rack 37 is located inside the Cascade parking garage between Rand and Main Streets. The existing Rack 37 drop connection to the OCI would be abandoned. To avoid impact to the parking structure, this new Rack 37 diversion structure would be constructed in Main Street upstream of the existing rack structure. The diversion structure would regulate flows to convey dry weather and adjusted typical year storm flows into a new pipe connection to the OCI. Overflows would continue through the existing combined sewer pipe and discharge into the Ohio Canal at the existing overflow point. Figure 3-5 shows the proposed Rack 37 diversion chamber and proposed connection to the OCI.

Rack 39 was abandoned in the year 2000 and dry weather flows are now conveyed into the OCI.

Racks 4 and 37 are proposed to be controlled to a minimum of zero overflows based on the adjusted 1994 typical year. Racks 4, 37, and 39 modifications described above should direct dry and wet weather flows up to the typical year into the existing OCI, approximately 45 MGD. Dry weather flow rates in the existing OCI remaining from Racks 4 and 37 are predicted to be approximately 1-1.5 MGD. Based on the slope of the existing sewer, the velocity is expected to not drop below 2.5 ft/s, which should prevent settling from occurring. The existing OCI would be capable of conveying the dry weather and adjusted typical year storm flow from these racks to the proposed Rack 19 Drop Shaft south of the W. Market Street Bridge in a new 36-inch pipe. Flows in an existing 15-inch sanitary sewer on the south side of W. Market Street would also be conveyed to the Rack 19 Drop Shaft. Construction of the Rack 19 Drop Shaft should be coordinated with the Rack 21 Sanitary Sewer Separation Project contractor since construction for both projects may overlap.

Flows in the existing Market Street Sewer would be intercepted upstream of Rack 19 and conveyed to the Rack 19 Diversion Structure in a new 90-inch pipe. The Market Street sewer would be abandoned downstream of the diversion structure to the proposed 90-inch pipe. This would allow the existing Rack 19 overflow point to be relocated (see following discussion).

Rack 19 Diversion Structure is designed with a weir wall to direct dry weather and wet flows into a 36” x 36” orifice in the base of the structure. The orifice is sized to control flows up to the 10-year, 1-hour storm which is a maximum of 74 MGD. Flows discharged from the Rack 19 Diversion Structure would be conveyed in a 48-inch pipe to the Rack 19 Drop Shaft. Flows discharging from the Rack 19 Drop Shaft (approximately 120 MGD) should be conveyed to the west in a new 72-inch pipe extending under the existing Ohio Canal enclosure and S.R. 59. This 72-inch pipe would connect directly into the OCIT-2 Drop Shaft located on the west side of Rand Street.

Flows greater than 74 MGD in the Rack 19 Diversion Structure would be screened and overflow the weir and be conveyed to a new 54-inch overflow pipe. The overflow pipe

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should connect to the Ohio Canal Enclosure at a new overflow point south of W. Market Street. The new connection would replace the existing Rack 19 overflow point, which would be abandoned as described above.

EXIST. OCI

PROP RACK 4

PROP RACK 37UPSTREAM OFTHIS POINT

PROP RACK 4CONNECTION

Figure 3-3

Ohio Canal Interceptor TunnelOCIT-2 Area Proposed Structures Layout

Figure 3-X

Ohio Canal Interceptor TunnelRack 4 Proposed Structures Layout

Figure 3-4

Figure 3-5

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3.3.4 OCIT-3 Area (Racks 16/17)

Dry weather and wet weather flows are proposed to be diverted to the OCI Tunnel at the OCIT-3 site. The underflow pipes of Racks 16 and 17 are proposed to be abandoned. Dry weather and wet weather flows would be conveyed through existing overflow pipes to the proposed Rack 16-17 Diversion Structure. The new diversion structure would be constructed at a location where the two overflow pipes are in close proximity, while limiting disturbance to Canal Park. The structure would be constructed partly within the banks of the existing Ohio Canal. Temporary flow control of the Ohio Canal would be necessary. The location of the Rack 16 - 96”x144” box overflow pipe was determined based on as-built drawings. The actual location of this structure should be field verified during final design. The diversion structure would utilize existing overflow sewers to allow flows in excess of the 10-year storm to be screened and discharge into the Ohio Canal.

The new diversion structure would direct dry and wet weather flow to a 96-inch sewer to a nearby junction chamber in the same parking lot. The junction chamber would include a 36” air jumper to convey air for odor control and influent sanitary flows from Canal Park. Dry and wet weather flow would be directed to the Rack 16-17 Drop Shaft and then tunneled under the Ohio Canal to the OCIT-3 Drop Shaft. Two tunnel bore diameters are provided as clearance between the bed of the Ohio Canal and the proposed consolidation sewer. Racks 16 and 17 consolidation sewer would convey a total 720 MGD of dry and wet weather flow. The consolidation sewer is designed to convey both combined sewer flows and air for odor control. Figure 3-6 shows the consolidation sewers, drop shafts, and diversion chamber for the OCIT-2 area.

Figure 3-6

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Rack 16-17 Consolidation Sewer location and layout was generally controlled by the following constraints:

Presence of the historic Howe House across the Ohio Canal from the diversion structure

Presence of both the Exchange Street and State Street bridge abutments and piers

Ohio Canal crossing clearance requirements

Existing steam utility lines and a pressure reducing station on the south side of Exchange Street

Desire to remain out from underneath Akron Children’s Hospital facilities

Desire to keep properties south of the current Akron Children’s Hospital Considine Building available for future development

Desire to avoid intermediate construction shafts along the consolidation sewer alignment

Feasible locations for the Rack 16-17 Diversion Structure

A minimum tunnel turning radius of 750 feet was assumed. The tunnel’s vertical alignment is deep enough to provide for two tunnel diameters of cover underneath the Ohio Canal, but no deeper so as to minimize the flow drop height at the Rack 16-17 diversion and to keep the entire alignment in a uniform soil condition (fine sands and silts).

3.3.5 Tunnel Discharge and Overflow

OCI Tunnel project area flows would be directed into a single diversion structure at the end of the OCI Tunnel. The structure would be constructed with an unobstructed dry weather flow channel plus two weirs in front of two separate flow outlet pipes.

Dry weather flows would be conveyed into a 60-inch I.D. pipe. An electrically-actuated sluice gate would be installed in the OCI Tunnel diversion structure at the 60-inch outlet to allow for isolation of the pipe and to serve as a redundant level of control in the event the plug valve discussed below is out of service. In order to prevent surcharging in the LCI, the dry weather flow would pass through a Control Valve Structure containing a 60-inch diameter plug valve. The hydraulically-actuated valve would be designed to close automatically as needed. The valve would be controlled based on the maximum allowable flow rate to the LCI, which is approximately 95 MGD. Alternatively, the valve may be controlled by active monitoring of the flows in the LCI. Remote control of this valve from the WPCS control room would also be important, as it may be desirable to limit flow from the OCI Tunnel diversion structure to the LCI based on other system flow concerns.

A magnetic flow meter for the 60-inch ductile iron pipe is proposed in a separate Flow Meter Structure, located downstream of the plug valve. This meter must be capable of

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measuring flows in partially-full and full pipe scenarios. The flow meter output can be used to adjust the upstream plug valve position based on a desired, adjustable flow set point.

The weir on the western side of the OCI Tunnel diversion structure would allow 340 MGD of wet weather flow to pass into a conduit leading to the future EHRT facility. After receiving treatment, these flows would be discharged to the Little Cuyahoga River through an overflow conduit not currently shown on the OCI Tunnel plans.

When the capacity of the EHRT is exceeded, a second weir in the OCI Tunnel diversion structure would allow excess flows, anticipated by the model to be as high as 1,340 MGD, to be diverted directly to a proposed overflow conduit. The proposed overflow conduit would consist of two 108-inch high by 144-inch wide box culverts. Culverts would be installed at an elevation over the existing LCI, and would extend to the edge of the Little Cuyahoga River. The culverts have been oriented to direct flow as far downstream as possible. However, further analyses are needed to determine optimum design to prevent potential negative impacts to the riverbanks and river flows. Figure 3-7 shows the proposed OCIT-1 Diversion Structure, LCI connection, and Little Cuyahoga River overflow pipe.

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3.4 Drop Shafts

Drop shafts for the OCI Tunnel may be designed to serve multiple purposes during the project lifecycle. The following criteria should be considered during final design:

Hydraulic Considerations

Dry Weather Flows – The shafts must be designed to efficiently convey both dry weather flows and wet weather flows. The Final Designer should consider adding a drop hole and possibly a vertical drop pipe through the baffles themselves to prevent dry weather flows from “ponding” on the baffle surfaces.

Wet Weather Flows – The proposed peak wet weather flow rates for Rack 16-17, OCIT-3, Rack 19, and OCIT-2 shafts are higher than baffle drop shaft systems built to date. However, extrapolation of modeling performed for a recent project in Canada suggested the baffle drop system can handle the flows. The Final Designer should perform both computational fluid dynamics (CFD) and physical modeling of the proposed shafts to confirm the system could successfully convey both the required wet weather and dry weather flows. The modeling should also confirm that the design would minimize aeration of the flow, and should prevent significant air release.

Surging / Burping / Air Movement - Preliminary design was based on the assumption that consolidation sewers and OCI Tunnel can operate with air movement in the tunnel to draw odors from public areas to the downstream outlet. Preliminary design surge analysis indicates surging and “burping” of shafts are not likely to occur in the OCI Tunnel. Therefore, the shafts have not been designed to provide surge relief. The Final Designer must perform transient flow analyses. If surge relief is needed, the final design should incorporate these needs into the hydraulic design of the baffle drop structures.

Passing of Debris Through Baffles – Preliminary design does not have bar racks or screens at the structures upstream of the drop shafts. As such, debris would be able to reach the baffle drops. An important part of the final design would be making provisions for removal of large debris caught on a baffle after a rain event has passed.

Structural Considerations

Erosion of Drop Structure Elements – The Final Designer should investigate the potential for erosion in the shafts due to flow drops and turbulence, and in associated approach and discharge pipes. High strength concrete is likely to be necessary in areas with significant drops, and where high velocities and flow transitions may occur.

Support of Large Baffles – Baffles shown in the preliminary design drop shafts are large and could require significant structural support. Typically, each baffle is designed to be supported only on the outside edge. Since the hydraulics of the baffle drop system are dependent upon the size of the opening between two baffles, adding a beam at the front edge of the baffle to provide additional structural support to the cantilevered edge would affect the hydraulic performance. The Final Designer must coordinate the structural design of the baffle with the hydraulic design of the shaft as a whole.

Uplift of Shafts – The Rack 16-17, OCIT-3, Rack 19, and OCIT-2 shafts would be founded in granular materials, and would have as much as 150 feet of groundwater head

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acting on the bottom of the shaft. This would be an issue during construction in the form of piping and heaving of the shaft excavation, and would be an issue for final design in the form of buoyancy when the tunnel is dry. Final design should account for buoyancy forces under a static groundwater table at the existing ground surface. If possible, the design should maintain water tightness of the structure by resisting uplift forces structurally, or with several redundant passive pressure relief systems outside the structure limits that do not compromise the CSO storage capacity of the tunnel and do not require maintenance.

Groundwater infiltration / soil piping – Fine sands and silts present in the OCI Tunnel horizon and along shaft sections would be highly susceptible to piping if groundwater infiltration occurs through either temporary or permanent shaft structures. Ground loss behind shaft walls can be catastrophic if ring compression is lost. Final design should include consideration for monitoring this type of ground movement during construction, and should include considerations for preventing ground loss in permanent structures. If permanent pressure relief is absolutely necessary around a shaft or tunnel lining, the final design should include redundant, no-maintenance systems that do not compromise the structures' water tightness or capacity for CSO storage.

Tunnel – Shaft Connection – The OCIT-3 shaft is currently designed online with the OCI Tunnel. Measuring along the inside face of the shaft, the OCI Tunnel opening requires removing nearly 40% of the shaft wall. The design would be further complicated by the presence of running ground outside the TERS walls. It may become necessary to extend the tunnel into the shaft (which may increase the final diameter of the shaft), to thicken the shaft walls (which may increase the TERS diameter), or to perform ground improvement outside the TERS limits to accommodate a structural transition zone outside the final shaft wall. The method of achieving this connection should be decided early in final design to facilitate hydraulic modeling of the drop shaft structure and design of the TERS.

Corrosion Resistance – The OCI Tunnel would be conveying both dilute combined sewage and concentrated sanitary flow. The Final Designer should consider possible corrosive effects on the shaft in combination with tunnel ventilation and cleaning requirements of the system as a whole.

Odor Considerations – OCI Tunnel preliminary design was prepared assuming that active odor control would not be needed. This was done by oversizing consolidation sewers to provide for active air flow, and by choosing a hydraulic drop system not requiring de-aeration of the dropped flows. The need for odor control should be evaluated during final design and after the system is put into operation. The Final Designer should coordinate with the odor control consultant for future addition of odor control equipment at critical locations.

Operations Considerations

Staff Entry – Shaft locations have been chosen in part because there is permanent and direct access for City of Akron Sewer Maintenance crews from existing public right-of-way. The final design should consider baffle drop shaft layout to facilitate the best access for operation and maintenance of the shafts and tunnel. As currently envisioned, shaft covers would be flush to grade, and man entry would be via a hatch. Entry into the

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tunnel at OCIT-2 Drop Shaft would be through the adit. Maintenance access should be evaluated in detail at this location.

Equipment Entry – OCI Tunnel drop shafts are likely to be the primary equipment entry points. For a tunnel this size, it is anticipated the City would need equipment access capable of accommodating at least a small front end loader or a man-lift. Although the OCIT-3 Shaft is a baffle drop, the shaft cover should be designed in a modular system to allow for retrieval and dropping of materials directly to the tunnel invert.

Baffle Access for Cleaning and Inspection – The recommended baffle drop uses 75% of the diameter of the shaft for flow, and leaves 25% of the diameter for a man access shaft. “Windows” or cut-outs in the divider wall between the flow area and manned entry area allow for visual inspection of the baffles. The Final Designer should consider providing means for baffle cleaning.

Safety and Security – Some of the proposed surface structures for this project are located in highly trafficked, public areas such as the Towpath Trail, Canal Park Stadium parking lot, and Akron Children’s Hospital parking lot. Protection from vandalism, as well as protection of the public from inadvertent injury at a site, should be an important design component. This protection extends to both construction conditions and long-term permanent conditions.

Construction Considerations

Shale Conditions – The OCIT-2 Drop Shaft would be founded in shale. The upper 10 to 20 feet of the shale could be highly fractured and weak. Upper and lower shaft TERS must be designed to accommodate the soil to shale transition zone, including anticipated high hydraulic permeability in the shale. Shale pre-grouting prior to shaft construction may be an appropriate approach to controlling groundwater flow to be considered by the Final Designer.

TBM Launching and Receiving for Multiple Bores – The OCIT-2 Shaft is a baffle drop structure currently designed with two flow inputs and one outlet, each of which is at a different invert elevation. Each of the three penetrations is deep enough that it would most likely be installed using trenchless methods. This would require coordination to properly plan construction sequencing to efficiently accommodate construction of three pipes.

Sequencing OCI Tunnel TBM Mining with Shaft Construction – The OCIT-2 shaft location is near the mid-point of the OCI Tunnel alignment. The Final Designer should determine if active construction access to this shaft would be needed by both the OCI Tunnel contractor and OCIT-2 contractor. The Final Designer should develop a construction sequencing approach to accommodate anticipated construction access needs and determine if joint or “shared” access is a feasible construction approach.

TBM Extraction – The OCIT-3 shaft could be used for the OCI Tunnel TBM extraction and would contain a baffle drop structure. The shaft would also receive flow from the Rack 16-17 consolidation Sewer. The Rack 16-17 consolidation sewer connects to the shaft at approximately Elevation 903, about 45 feet below existing ground surface and 92 feet above the shaft invert.

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The OCI Tunnel Final Designer should assume the OCIT-3 contractor may occupy the OCIT-3 shaft site prior to the OCI Tunnel contractor mobilization at this site. The OCIT-3 Consolidation Sewer could build a launch pit and complete the Rack 16-17 Consolidation Sewer tunnel before the OCI Tunnel contractor needs the site. The OCI Tunnel contractor could construct the OCIT-3 Drop Shaft TERS and make the final connections between the consolidation sewer and the shaft. The Final Designer should develop a construction sequencing approach to accommodate anticipated construction access needs and determine if joint or “shared” access is a feasible construction approach.

Lateral Shaft Movements During Construction – Drop shafts are located in close proximity to existing infrastructure, including roadways, bridges, railroads and significant utilities (e.g. water mains, fiber optics, etc.). Owners of those infrastructure elements would expect there to be no disturbance from shaft construction operations. The Final Designer should consider the risk of lateral movements and specify appropriate monitoring program requirements for each shaft. ODOT bridges and the Exchange Street Bridge structure should receive special attention.

3.5 Tunnel Design

The preliminary design has analyzed both construction methods and structural elements required to achieve the preferred vertical and horizontal tunnel profile. On this project, tunnel design was particularly impacted by the vertical alignment which provided optimal operational characteristics, namely dewatering of the OCI by gravity. In general, preliminary designs discussed below are conservative but necessary for a successful project given the current configuration and vertical alignment described herein.

3.5.1 Tunnel Portal Designs

Launching Portal

The OCI Tunnel crown would be above the existing ground surface north of Hickory Street. This condition presents significant challenges to the TBM operator such as poor ground conditions in the first several hundred feet consisting of loose sands, and some organic clays, and shallow cover over the TBM which would bore beneath Hickory Street, the Cuyahoga Valley Scenic Railroad, and North Street in quick succession after launching

It was assumed the TBM would be launched from a shallow trench supported by driven sheet piles. Test boring data collected during preliminary design indicates a highly variable depth of overburden soils. Therefore, the sheet pile walls are anticipated to be driven into rock, but additional investigation of the rock surface is recommended during final design. Preliminary design assumed a double sheet pile wall would be installed at the portal entry to allow for a “window” opening through which to launch the TBM.

Based on existing ground conditions at the tunnel launch point, ground improvement for the first 100 feet south of the tunnel launch face is recommended. The addition of engineered backfill or flowable fill on the south side of the sheet pile wall is recommended to provide cover for the TBM.

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While the OCI Tunnel mining site has sufficient area for pre-assembly of the TBM and its trailing gear prior to launching, the contractor would have to optimize the rail layout for mucking and supplies operations because the portal is relatively close to the proposed Otto Street temporary bridge location. For this reason, the preliminary design includes an alternate entrance design, starting on Hickory Street and extending down a new embankment parallel to Hickory Street.

Geotechnical data in the area of the tunnel portal and first few hundred feet of the OCI Tunnel indicate these structures would need to be constructed in unfavorable soil and groundwater conditions. Although existing infrastructure does not appear to be extremely sensitive, critical, or difficult to repair, there may be a risk of significant delays to the OCI Tunnel project and negative public perception. The Final Designer should obtain detailed information about this area and analyze the proposed construction methods in detail to confirm the concepts shown on the preliminary design drawings to achieve the design conditions.

OCIT-2 Adit

The OCI Tunnel would be mined adjacent to the OCIT-2 Drop Shaft, resulting in the need to construct an adit connection between the drop shaft and the tunnel. The invert of the shaft and OCI Tunnel would be constructed in hard gray siltstone layers with interbedded layers of hard shale. The adit connection would have 30 feet or more of shale and siltstone cover. In these conditions, and based on the short distance required (<20 feet), this adit would likely be mined by drill and blast or mechanical excavation methods. No special requirements are anticipated for the portal, other than protecting the crown from overbreak (slabbing of the shale and siltstone) and support for the OCI Tunnel concrete lining during the break-through. The OCIT-2 shaft would be supported by rock bolts and mesh at the depth of the adit. The OCIT-2 Drop Shaft final design should account for the adit penetration in the TERS design.

Rack 19 Consolidation Sewer Tunnel Portals

As currently envisioned, the Rack 19 Consolidation Sewer would be mined from the Rack 19 Drop Shaft, located on the east side of S.R. 59, to the OCIT-2 Drop Shaft on the west side of S.R. 59. The Rack 19 Consolidation Sewer would be a 72-inch I.D. pipe with a 0.4% grade and a total length of 466 linear feet. The tunnel would be launched from the Rack 19 Drop Shaft into a soft to soft dark gray shale layer with approximately 7 feet of rock cover over the tunnel crown. Based on conditions encountered in 2006 Advanced Planning Study test boring BH-6, the ground above the shale layer could be granular fill over till materials. A boulder was also encountered at the soil-shale interface, suggesting similar conditions could be encountered in the tunnel horizon. Groundwater seepage is not anticipated to be a challenge for launching of the Rack 19 Consolidation Sewer. The Rack 19 Drop Shaft TERS would need to account for the TBM launch, including the need for a reaction block at the back of the shaft and a portal through the shaft wall. Based on the soil and rock conditions listed above, a typical steel tunnel eye could be built onto the shaft wall to support the TBM launch.

At the end of the Rack 19 Consolidation Sewer tunnel, in the OCIT-2 Drop Shaft, the boring machine would likely exit through both layers of highly weathered, moderately hard shales and overlying hard clays. The mining machine may pass through cobbles, gravel, and possible boulders in this layer. The soil overburden would be silts, silty

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sands, and clayey sands. The receiving portal is not likely to require consideration for significant groundwater infiltration at OCIT-2. Based on the conditions described above, it is likely that the Rack 19 Consolidation Sewer contractor would be able to safely mine through the wall of the OCIT-2 shaft TERS without a gasketed tunnel portal. The shaft support system would need to be designed to allow penetration of the Rack 19 Consolidation Sewer TBM and associated casing and / or carrier pipes. The current OCIT-2 shaft TERS recommendation is a drilled secant pile wall. The OCIT-2 shaft final design would need to provide a section of wall for the TBM to break through. The Rack 19 consolidation sewer tunnel construction would need to provide a tunnel eye to support the opening. Depending upon groundwater conditions at the OCIT-2 soil-rock interface, temporary dewatering may be needed to facilitate the breakthrough and re-sealing of the shaft wall.

OCI Tunnel Receiving Portal

The OCIT-3 Drop Shaft receiving portal would require both temporary and permanent design considerations. For receipt of the TBM, the Final Designer should consider how the TBM could bore through the slurry wall panels without allowing groundwater and sands to flow in through the un-grouted annulus between the shaft and TBM. Common practice for these types of breakthroughs has been to either improve a block of ground outside the shaft so the tunnel liner can be installed and sealed prior to the TBM breaking through the shaft wall, or construction of a gasketed TBM portal through which the TBM and its shield can safely pass.

In addition to construction concerns, the Final Designer should design the final structural wall for the OCIT-3 Shaft to accommodate the OCI Tunnel opening. The tunnel opening is a substantial part of the shaft wall. Structural supports necessary to maintain this opening and transfer the shaft ring loads around the opening tend to be very large. The simplest design for this condition is to allow the tunnel lining system to extend into the shaft until the springline of the lining system has passed into the shaft. In this way, the tunnel liner itself can be utilized as a structural element. A disadvantage to this particular design is a squared-off tunnel face extending nearly to the centerline of the shaft. This configuration is often difficult to incorporate into the drop shaft design.

A second method of designing the tunnel / shaft connection is to thicken the walls of the shaft in a box or ring around the TBM lining system. In rock tunnels, this is easily done by excavating an enlarged cavern outside the shaft walls which allows for a thickened “collar” design. However, in the OCI Tunnel ground conditions, this would not be possible without substantial ground improvement. The Final Designer may consider enlarging the entire shaft to allow for thickened walls at the tunnel penetration.

Rack 16-17 Consolidation Sewer Receiving Portal

Similar challenges would be present for construction of the Rack 16-17 Drop Shaft, the connection of the Rack 16-17 Consolidation Sewer to the OCIT-3 Drop Shaft, and the OCIT-2 and Rack 19 Drop Shafts.

3.5.2 Tunnel Boring Machine Selection

Based on data collected in the preliminary design phase, the TBM type best suited for anticipated ground conditions along the preferred OCI Tunnel alignment is a single

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shield pressurized face machine with disc cutters on the cutterhead to accommodate reaches with a full face of rock. An EPB machine may be feasible for the OCI Tunnel alignment. Based on the limited data available during preliminary design, an EPB machine may not be appropriate for conditions along the proposed Rack 16-17 Consolidation Sewer alignment. The Final Designer should investigate the alignment in greater detail and determine if a slurry face machine or other technology is necessary to successfully complete the Rack 16-17 Consolidation Sewer construction.

PER Appendix Y includes documentation of a TBM Performance Study conducted by Jamal Rostami, PhD, PE, which is summarized below and in the following sub-sections. TBM production rate was estimated based on empirical analyses as well as historical data for similar tunnel projects. The OCI Tunnel TBM is anticipated to achieve an overall production rate of 6.5 feet per hour (ft/hr) in soft ground and mixed ground, and as much as 9 ft/hr in rock reaches. The average daily advance rate for the entire tunnel is anticipated to be around 45 feet per day (ft/day) (~16.6 m/day) and overall utilization would be approximately 28% for an EPB type TBM. Overall utilization is a reduction factor used to modify the maximum theoretical rate of TBM penetration to account for various delaying and non-productive factors, including maintenance shifts, time for the initial “learning curve,” labor skills, site management delays (e.g. muck handling), the mining / lining installation / grouting cycle time, slower mining rates while in curved alignments, use of a single shield machine in rock tunneling mode, and others. Estimated completion time is 400 shifts or about 27 weeks after the machine’s full assembly and start of the boring. The work schedule is assumed to be three 8 hour mining shifts per day, five days a week, with a maintenance shift on the weekend.

The OCI Tunnel TBM should be designed to deal with project specific conditions, including, but not limited to the following:

Low overburden at tunnel launch portal,

Alignment curves,

Structures above the TBM which could be affected by mining-induced groundwater dewatering,

Groundwater in sands flowing into TBM,

Boulders,

Mixed rock / soil face conditions with varying strength and quality shales,

Variations in rock quality within the TBM face,

Overbreak of rock materials in the crown of the bore,

Methane gas in shales,

Slaking of shales, and

Difficult tunnel termination into shaft at end of tunnel drive.

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Detailed discussions of TBM requirements and final design considerations are presented in the following sub-sections.

Potential Impacts of Existing Conditions on TBM Selection

For the purpose of TBM performance analysis, the tunnel is broken into 10 sections. (Table 3-2), where each section constitutes an area of different geology or requires use of different utilization factors. The seven reaches shown on Figure 2-11 are also utilized in this chart. For this project, the breakdown is primarily determined by curves and geology along the alignment.

Table 3-2 Tunnel Sections to Assign Machine Utilization

SectionNo.

Reach No.

StartingStation

EndingStation

Length(ft)

Description Notes Conditions

1 1 11+00 12+00 100 Soil and Improved Ground

Portal at STA 11+00 Surface excavation Retaining walls SP (70%)-Fill – should be improved

2 2 12+00 14+00 200 Soil Straight tunnel in soil o SP (70%)-Fill

3 3 14+00 19+00 500 Mix condition

Straight tunnel in mixed ground: o Shale (30%) o SP (60%) o ML (10%)

4 4-A 19+00 23+00 400 Rock Straight tunnel in shale 5 4-B 23+00 30+00 700 Rock Straight tunnel in shale

6 4-C 30+00 36+00 600 Rock Curvature with R= 1100 ft in shale

7 4-D 36+00 53+00 1700 Rock Straight tunnel in shale, start curvature at STA 51 +/-

8 5 53+00 61+00 800 Mix condition Curvature with R= 1100 ft in shale to STA 57 +/-

9 6 61+00 69+00 800 Soil Straight tunnel in soil ML 10 7 69+00 71+50 250 Soil Straight tunnel in soil, CL-ML

Borability of Shale Formations

OCI Tunnel shale formation borability was established using discrete rock sample laboratory testing. Borability is generally established by two index values, the Drilling Rate Index (DRI), and the Cutter Life Index (CLI). A total of five shale samples from the Preliminary Geotechnical Investigation were tested at the Pennsylvania State University rock laboratory. Test results indicate the maximum DRI of the shale samples average 81, with minimum and maximum values of 77 and 85, respectively. The CLI for the five samples averaged 84, with minimum and maximum values of 55.8 and 119.8, respectively. The DRI and the CRI indicated the rock expected to be encountered on the OCI Tunnel alignment should be easy to drill and bore and is likely to be gentle on rock cutting discs, resulting in minimum wear during rock mining.

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Shale formation structural characteristics should also be considered in TBM design. For example, bedding thickness, degree of joint weathering, and joint orientation should affect TBM performance. Review of the optical televiewer logs of borings OCI-15, OCI-19, and OCI-22 suggest there are two major horizontal/sub-horizontal discontinuities of fractures and bedding in formations along the tunnel alignment. Joint spacing is rather low (a couple of inches) in the tunnel horizon, except in OCI-15 and OCI-22, which do not show joint spacing in un-weathered rock sections. This setting of orientation is neutral or may somewhat slow down machine penetration.

Overbreak and Short Term Behavior of Shale Formations

Elastic inward radial deflection caused by stress relief, overbreak, ravelling, and slaking- induced squeeze caused by exposure to water are possible short-term behavioral traits expected while tunneling. These rock behavior characteristics may cause unanticipated friction or occasional lock up on the TBM exterior as elastic rock deflection or rock fragments fill annular space between the tunnel boring machine and tunnel bore. Tunnel support should be installed immediately behind the tail shield otherwise the tunnel crown may slab or ravel forming a triangular shaped dome above the tunnel bore.

For short-term excavation and support conditions, un-weathered shale bedrock is expected to behave as moderately to blocky, seamy rock, while the weathered bedrock may behave more like a completely crushed, but chemically intact rock. Blocky and seamy rock consists of chemically intact, or nearly intact, rock fragments that are separated but interlocked imperfectly. Bedding planes are horizontal or nearly horizontal.

The largest tunnel completed to date in the shale formations of Northeast Ohio was the Mill Creek Tunnel (MCT). The MCT-3 had a 20 feet finished diameter in Chagrin Shales, an older shale formation than the Cuyahoga Shale present on this project. Published tunnel mining reports stated crown overbreak was a significant event and cause for significant additional concrete to fill voids left in the tunnel ceiling after the mining pass. Overbreak was also reportedly a design concern with the 47.5-foot diameter Niagara Tunnel mined in the Queenstown shale. The Euclid Creek Tunnel (ECT) is currently being mined through Chagrin Shales in Northeast Ohio. The ECT is being lined with precast concrete segments immediately behind the TBM and two-part fast-setting grout is being injected from the tail shield to achieve nearly immediate, 360-degree grouting of the segments immediately after leaving the tail shield area.

Crown overbreak occurs when the crown of the tunnel is allowed to deform after mining to the extent the shale breaks in beam tension. Overbreak is typically a significant problem for two-pass lining systems because the shale must be supported in-between mining and final lining. However, concern also exists for tunnels mined using one-pass lining systems because large shale crown breaks could prevent proper placement of concrete segments, could prevent full grouting of the annulus between the liner and the shale surface, or could result in a point loading on the tunnel shield or the concrete segments.

Use of a single shield EPB TBM in the rock conditions described above could also be difficult because the tail shield would not allow for expansion of a tunnel lining system. Most likely method of addressing this is to require continuous grouting of the lining annulus with a two-part component grout or, if feasible, a pea gravel injection.

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Regardless, the annulus filling would likely need to be accomplished immediately behind the tail shield in order to prevent deformation of precast concrete liner segment rings. If the contractors plan to mine in “open face mode” in the shale formations, the TBM grouting system should also be designed to allow grouting of the lining without a significant risk of grout running forward into the cutter face.

Potential for Explosive Gas Intrusion

Methane gas is formed in soil and rock by anaerobic decomposition of organic matter by either bacterial or thermal processes. Rocks which produce prolific amounts of methane tend to be black shale and coal; however dark colored shale is thought to be capable of producing methane. Methane is an odorless, colorless, flammable gas. The lowest flammable methane concentration in air is five (5) percent (lower explosive limit, LEL). The highest flammable methane concentration (upper explosive limit, UEL) in air is 15 percent. While higher methane levels in air are not explosive, the level should be diluted before work can begin. This could result in methane concentrations passing through the explosive limits.

In general, during OCI Tunnel preliminary geotechnical investigations, normal atmospheric levels of oxygen (20.9 percent) were observed above the casing after each rock core sample was collected and no other detectable gasses were measured. However, similar projects bored through shales in Northeast Ohio encountered high methane levels. The Mill Creek Tunnel Contract MCT-3 experienced methane readings up to 195 percent of the LEL. As a result of this, the project experienced an eight month delay. Initial Mill Creek Tunnel ventilation system capacity was 50,000 cubic feet per minute (cfm). However, after four tunneling shutdowns due to high methane concentrations the contractor added an additional 30,000 cfm of ventilation, bringing the total ventilation to 80,000 cfm. Despite additional ventilation, methane levels still remained over allowable levels. Tunneling operation was stopped until methane levels could be lowered to allowable levels. To achieve this, the contractor installed 14 de-gassing wells, constructed a 14-foot diameter ventilation shaft with four 75-horsepower blowers, and installed baffles in the tunnel. It was later determined a ventilation system with a capacity of 300,000 cfm would have been required to keep gas inside the tunnel below allowable levels.

Trapped bodies of methane may travel along rock fractures or a permeable stratum toward the excavation. The most likely location of methane entering into a tunnel or excavation would likely occur at the excavation face. In rock tunnels, gas can also enter through discontinuities in the walls and can be released through porous rock. During shaft and shallow structure construction, gas is not expected to be encountered in the soil above the rock. However, methane gas could seep up through fractures in the rock or be drawn in with groundwater seepage. Once excavation reaches the shale, pockets of methane gas could be encountered. The contractor should be prepared to excavate and ventilate the shaft should methane gas be encountered. Regardless of the ventilation system used, the contractor should still expect pockets of methane potentially exceeding allowable levels causing delays in the tunneling operation.

As a result of the historical experience in Northeast Ohio shales similar to the Cuyahoga Foundation, the project area should be considered “potentially gassy” as defined in Federal OSHA Underground Construction Standard 29 CFR 1926.

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Groundwater In Shale Formations

Packer testing and slug testing results indicate shale bedrock hydraulic conductivity is relatively low, except at the soil-bedrock contact where bedrock is likely weathered and/or fractured and sand layers are present. Permeability values obtained by packer tests in the shale tunnel zone (in test borings closest to the preferred alignment) reached as high as 2.9 x 10-4 cm/sec at the north end of the alignment (in test boring OCI-15). However, permeability values decrease as the tunnel alignment is mined through more competent shale layers. The tunnel zone shale permeability values at test borings OCI-19 and OCI-22 ranged from 2.9 x 10-7 cm/sec to 8.0 x 10-5 cm/sec. Slug testing of monitoring wells screened in the shales indicated a similar trend. Wells sealed into competent shales (e.g. at OCI-22, OCI-18, and OCI-26) exhibited hydraulic conductivity values of 5 x 10-7 cm/sec, 1.1 x 10-7 cm/sec, and 1.6 x 10-6 cm/sec, respectively.

The groundwater levels in wells at OCI-22 and 25, both of which are screened in the shale layers, rise from Elevation 820 to 845 as the tunnel progresses south from STA 14+00 to STA 19+00. However, by the time the tunnel reaches test borings OCI-18 and 26 at approximately STA 33+00 and STA 40+75, respectively, the piezometeric groundwater surface in the shale is at Elevation 880.

Groundwater In Soil-Rock Transition Zone

One test well was installed across the soil-rock transition zone. OCI-31 is located approximately at STA 52+75, where the OCI Tunnel is anticipated to begin emerging from the full shale face condition. The well at OCI-31 exhibited a hydraulic conductivity value of 3 x 10-5 cm/sec. The groundwater level in the OCI-31 monitoring well stabilized at Elevation 910, approximately 30 feet higher than wells screened completely in the shale layers up-station.

Groundwater In Soil Layers

The groundwater table along the first 1000 feet of the OCI Tunnel (STA 10 to STA 20) is expected to rise with increasing distance from the Little Cuyahoga River. The maximum groundwater elevation measured during the 2-months of the Preliminary Investigation was at Elevation 853 at OCI-35. Hydraulic conductivity testing of the soil layers in this reach exhibited values of 2 x 10-5 cm/sec to 6 x 10-5 cm/sec.

At the south end of the tunnel, between approximately STA 53+00 and STA 71+00, the groundwater elevation in wells OCI-31 and OCI-10A ranged from Elevation 910 to Elevation 918. Slug testing in these two wells indicated the aquifers tested had mean hydraulic conductivities of 3 x 10-5 cm/sec and 2 x 10-5 cm/sec, respectively.

In general, the TBM contractor can anticipate higher groundwater tables and higher rates of groundwater inflows on the south end of the tunnel. While tunneling in competent shale layers at least 20 feet below the soil-rock interface, the contractor can expect less infiltration and recharge of groundwater due to both lower hydraulic heads and lower hydraulic conductivities.

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Presence of Boulders

During the Advanced Planning Study (2006) geotechnical investigation, a boulder was reportedly encountered in test boring BH-6. During preliminary engineering geotechnical investigation, cobble layers were confirmed, and investigators suspected boulders may have been encountered in test borings shown on Figure 3-8. Although boulders appear to be isolated, it is essential boulders are considered during machine selection and operational procedure development. During a 2012 visit to the Robbins TBM Headquarters in Solon, Ohio, the Robbins representative indicated a TBM with a face around 30 feet in diameter could likely ingest a boulder up to 1 meter in size into the screw conveyor, if the conveyor were designed properly. Mining in the shale formations should afford the contractor the ability to reach the mining face to break or blast significant boulders so they can be safely ingested.

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Tunnel Boring Machine Requirements

As mentioned earlier, the tunnel boring machine likely to be the best suited to handle anticipated ground conditions is a single shield EPB machine. This is due to the need to react to the pressurized soil face under the existing groundwater table. Soft ground or soil and mixed ground account for roughly 2800 ft (~854 m) of OCI Tunnel alignment. An EPB machine laced with disc cutters on the cutterhead can accommodate full face of rock.

The TBM recommendations provided below have been verified using historical data from similar case studies. Historical data details are presented in PER Appendix Y. However, information used in this report is based on OCI Tunnel preliminary investigations and design assumptions. Anticipated machine performance should be evaluated in final design if additional investigations and resulting baseline values differ from values used in this report.

As was discussed in Section 2.3, an EPB machine is likely to be able to accommodate tunnel soil and mixed ground portions with a proper soil conditioning system. The recommended general machine specification is summarized in Table 3-3. The machine should have a cutterhead with sufficient opening ratio for the soil section but laced with disc cutters to allow for full face rock excavation. A spoke-type cutterhead arrangement would be appropriate with back loading disc cutters. Rippers and soil spades/knives should be placed on the head to shear soil, but they would be recessed and lined up slightly behind the disc cutters to avoid direct contact with boulders and rock face.

To realize potential high daily advance rates, the machine should have higher power than normal soft ground EPB machines so it does not run power limited in the operation and can break out of standstill if face collapses are encountered. Estimated cutterhead installed power is 3000 kilowatts (kW) (4000 hp). This is based on a brief review of records of TBMs of this size, as described in PER Appendix Y. This is higher than typical cutterhead power for soft ground machines but in the range of common hard rock machines of this size (high end on the soft ground machines but mid range for hard rock machines). A dual mode machine with screw conveyor, as well as a face belt conveyor located at the center of the cutterhead, may be used to allow for machine operation in open mode in the rock portion if economically and operationally justified.

Table 3-3 Recommended General Specifications for OCI Tunnel TBM

Item Unit Value Notes (SI units) Diameter Ft 30 ~ 9.15 m

Disc cutter size in 17 432 mm Most common most likely to be used in this project

Cutter load capacity Kips 55 25 ton

Cutter tip width in 5/8 (0.625) 16 mm

Cutter spacing in 3.6 90 mm at the face lower spacing at the center and

gage No. of Cutters # 60

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Table 3-3 Recommended General Specifications for OCI Tunnel TBM

Item Unit Value Notes (SI units)

Cutterhead rotational speed

Rotations per Minute

(RPM) 0 - 4

Can be up to 5.8, but this range was selected

The head is bidirectional to accommodate soft ground excavation

Cutterhead Thrust Kips 3,300

1450 tons Delivered to the cutterhead for rock

cutting, this does not account for skin friction.

Propel Thrust Kips 11,500 ~ 5000 tons It could be up to 8000 tons based on

some manufacturer’s design Installed Cutterhead

Power Horsepower

(Hp) 4000 3000 kW

Operational Torque Foot-

Pounds (Ft-lbs)

4,200,000 5700 kN-m

Max Propel Speed Ft/hr 15 ~ 5m/hr

TBM Utilization and Estimated Advance Rates

Review of literature shows EPB machines in the range of approximately 30 ft (9 m) diameter advance/propel through soil at a rate of about 6-7 ft/hr (1.8-2 m/hr) when they excavate the face. This translates to about 1.2-1.4 in (30-35 mm) penetration per minute. At a cutterhead rotational speed of approximately 4 RPM, the penetration rate is 0.3-0.4 in/rev. (7-10 mm/rev). For estimating machine performance in this study, the higher end of the common range, or 6.5 ft/hr (2 m/hr), is recommended to develop a preliminary project schedule. This recommendation acknowledges the fact that EPB machines have become more common in the United States, and the level of expertise and machine technology has increased the production rates beyond what historical data would suggest.

Machine performance in a mixed ground condition (soil and shale rock) is similar to soft ground, except penetration per revolution should be checked to determine the likelihood of overloading the disc cutters if they encounter rock at the invert. For a given rock, there is a certain depth the disc cutter can penetrate in every pass without exceeding the disc nominal load limit. This can be checked by using a model for estimation of cutting forces acting on a disc cutter in a geological setting. Preliminary calculations, included in PER Appendix Y, show if the machine is operated at a constant propel rate of 0.3-0.4 inch/revolution, cutter loads would be in the range of 30-35 kips (140-150 kN), well below the 55 kip (250 kN) capacity of the cutters. Since rock encountered at the face within mixed ground conditions is likely to be highly weathered and generally weak, anticipated cutter loads should be lower and within the safe operating range of 17 inch (432 mm) diameter disc cutters.

Performance prediction results in rock materials show in a full face of rock, the machine should be able to reach a penetration rate of about 0.6 inch/rev (15 mm/rev) without exceeding its thrust and torque capacity. Using average cutter wear conditions and

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assuming 75% maximum new cutter performance, this translates to a rate of penetration of about 9 ft/hr (2.7 m/hr). The machine is likely to be torque/power limited before it reaches cutter load capacity limit or thrust limit.

Penetration rates described above are theoretical and generally based on TBM mining in a single subsurface medium (e.g. either rock or soil, not both). Actual rate of advancement for OCI Tunnel would likely be reduced in rock because the TBM would likely be a single-shield machine. Also accounting for lower utilization during the first few hundred feet of tunnel (the “learning curve”), and a slight discount to account for curves, the analysis shows the average daily advance rate for the entire tunnel could be around 45.4 ft/day and overall utilization could be approximately 28% for an EPB type of TBM.

Estimated rate of penetration in rock is higher than the machine propel rate in soil and mixed ground conditions. To realize the higher penetration rates in full face of rock, higher machine power is needed. The backup system should be designed to be able to handle additional muck produced at instantaneous penetration rates close to 11 ft/hr (3.3 m/hr) which is equivalent to approximately 300 cubic yards per hour (cy/hr) bank or 440 cy/hr (240 m3/hr bank or 340 m3/hr) assuming a swell factor of 40%. These values can be used to size the muck transportation system to prevent muck overruns.

Pertinent TBM Performance Risks

While there are precedents of tunneling in conditions similar to the proposed OCI Tunnel alignment, there are always inherent risks in tunneling projects and in operating tunneling machines. Some risks are due to the unknown ground nature always present, whereas there are some risks involved with selected means and methods, machine type and specification, site organization and management, and preparation level for unforeseen situations. There are various ways to register potential risks and mitigate or manage them. Following is a partial list of potential TBM performance risks likely pertinent to this project and related specifically to TBM selection and performance. These risks were identified as part of a TBM Performance Study, in PER Appendix Y, and have been incorporated into the OCI Tunnel Project Risk Register in PER Appendix Z.

Need for hyperbaric interventions to maintain TBM face,

Risks involved with encountering water bearing zone in shale if the EPB is operated in “open mode” as if it were an open face rock TBM,

Ground heave or loss at tunnel portal,

Risk of settlement or heave when pressure-face tunneling with less than two (2) tunnel diameters of cover,

Risk of damage to cutters in mixed grounds (esp. transition between rock and soil face),

Difficulty of steering in mixed ground,

Risk of overloading the cutters, unbalanced forces on the cutter head, or unbalanced forces on the thrust cylinders while mining in mixed ground,

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Risk of over-excavation in mixed ground,

Gassy ground and explosions in the TBM,

Boulders damaging the cutters,

Unintended dewatering of surrounding rock through the TBM face if the EPB is operated in “open mode” as if it were an open face rock TBM,

Machine-related failures due to mixed ground mining.

3.5.3 Tunnel Construction Issues

General construction issues for the OCI Tunnel mining operation are listed below and described in the following paragraphs:

Emergency shafts

Monitoring Program

Dump Site in St. Vincent football field area,

Dust control during shale mining

Muck Handling and Disposal

Emergency Shafts

The risk of needing an emergency shaft at an unplanned location is present in nearly every tunnel project. The risk is based on uncertainty in subsurface investigations that cannot be completely mitigated until the ground is excavated by the TBM. Pre-planning and pre-design of contingency plans might decrease the severity and probability of this risk. On the OCI Tunnel project, emergency shafts might become necessary due to machine failures, loss of TBM or tunnel water tightness (leading to flooding), presence of unbreakable boulders in flowing ground reaches, unexpected dips in bedrock surface topography, etc. Depending upon ground conditions and TBM depth, an emergency shaft could be anticipated to be 20 to 30 feet in diameter, and could be needed for several months to a year.

In the areas north of the Wheeling and Lake Erie railroad, the potential impact and difficulty of building an emergency shaft is relatively low. By comparison, an emergency shaft underneath the St. Vincent St. Mary property or Towell property would be not only expensive, but disruptive and damaging to the area and existing structures. It is anticipated an emergency shaft along S.R. 59, or even beneath S.R. 59, would be difficult because it would be built in primarily granular soils. Construction methods would have to include dewatering, ground freezing, or slurry type construction similar to the proposed OCIT-2 Shaft construction method. However, based on current traffic conditions, emergency shafts in these locations would have less of an impact, as traffic on S.R. 59, Rand, and Dart can be relatively easily re-routed.

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Monitoring Program

Public perception and possible effects on critical structures would necessitate a geotechnical monitoring program on this project. At a minimum, the program should include surface and structure monitoring at the following locations, also shown on Figure 3-9:

Cuyahoga Valley Scenic Railroad

North Street

Aetna Street substation property (First Energy)

Wheeling and Lake Erie Railroad rails

Wheeling and Lake Erie Railroad viaduct

St. Vincent St. Mary High School football field

Towell building

Diamond Grill building

Market Street

ODOT Market Street bridge over S.R. 59

West Mill Street bridges (2) near Rand Street ends

Ohio Canal Towpath Trail bridge near Rand Street end

Rand Street

S.R. 59 at tunnel crossing

W. Central Street bridge over S.R. 59 (formerly known as relocated Locust St. bridge)

State Street bridge over S.R. 59

Akron Children’s Hospital Locust Street parking structure

Buildings and residences along North Street, Hickory Street, and Tarbell Avenue

Building and residences along Exchange Street

OCI Tunnel and Consolidation sewer shaft locations

The Howe House

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A monitoring program is required by ODOT, based on discussions with ODOT District 4, as a condition of their permission to build beneath S.R. 59 and adjacent to the S.R. 59 bridges. Geotechnical monitoring should provide baseline data prior to construction, provide tunnel alignment monitoring at an increased frequency as the TBM approaches the area, and have specific action levels and action plans for each reading exceeding an acceptable amount of settlement (as defined by ODOT). Action plans may include confirmation of readings, revised mining procedures to potentially reduce the likelihood of additional movement, stabilization of the settled areas by ground treatment, or increased monitoring to protect public safety. A mitigation plan should also be prepared to discuss actions to be taken to repair or replace structures, including the ODOT bridges, if movement were to occur.

Figure 3 - 9

AREAS AND STRUCTURESRECOMMENDED FOR MONITORING

DURING CONSTRUCTION

DIAMOND GRILLBUILDING

TOWELL PROPERTY

ST. VINCENT ST. MARYFOOTBALL FIELD

WHEELING AND LAKE ERIERAILROAD VIADUCT

WHEELING AND LAKE ERIE RAILROAD

AETNA STREETSUBSTATION PROPERTY(FIRST ENERGY)

CUYAHOGA VALLEYSCENIC RAILROAD

WEST MARKETSTREET BRIDGE

W. CENTER ST.BRIDGE

STATE ST.BRIDGE

WEST MILL ST.BRIDGE (1)

WEST MILL ST.BRIDGE (2)

RICHARD HOWEHOUSE

ACH LOCUST ST.PARKING STRUCTURE

EXCHANGE STREET

SR 59

SR 59

MARKET ST

NORTH ST

RAND STOHIO CANAL TOWPATH TRAIL BRIDGE

HICKORY ST

TARBELL AVE

OCIT-2 DROP SHAFTLOCATION

OCIT-3 DROP SHAFTLOCATION

RACK 16-17 DROP SHAFT LOCATION

RACK 19 DROP SHAFTLOCATION

NOT TO SCALE

LegendOCI Tunnel Alignment

Consolidation Sewers

R 16/17 ConsolidationSewer

N

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Dump Site in St. Vincent Football Field Area

Preliminary design does not require excavation within the assumed limits of the former dump site under the St. Vincent St. Mary football field. However, if the contractor would need to install a temporary or emergency shaft during construction, the OEPA would likely place restrictions on the excavation operation. Special handling may be necessary during construction, and materials removed from the area may have to be landfilled. St. Vincent St. Mary High School obtained a Rule 13 agreement with OEPA during construction of their football field. A similar Rule 13 agreement may be needed for OCI Tunnel. Even if there are no planned excavations within 300 feet of the known limits of the dump site, OEPA should be contacted to determine whether special actions or precautions would be necessary while mining below the vertical limits of the St. Vincent dump site.

Mining Dust Control

Dust control would be important for both safety of the construction site and to prevent nuisance to the neighbors and community. Inside the tunnel, dust could be generated primarily by the shale muck if it is not condition prior to excavation. If shale dust is allowed to build-up in the tunnel, the dust can reach an explosive limit and be susceptible to even minor sparking. Shale dust can be controlled by selective wetting or misting systems over the conveyor or muck car, and by minimizing the amount of handling of the material.

Stockpiles of muck materials should also be monitored for dust escaping onto adjacent properties. The contractor should maintain a watering system during dry seasons to control muck dust. During transport off site, trucks should be covered and sealed as much as possible to prevent dust escape on the roadways.

Finally, shale dust is likely to contain silica particles, which can lead to silicosis of the lungs when inhaled. The contractor should implement a safety procedure to protect workers and visitors from exposure to silica dust.

Muck Handling and Disposal

Muck generated by mining operations may consist of conditioned ground or shale. Conditioned ground would be generated as the TBM is advanced in pressurized face mode. Ground conditioning may consist of water or a mixture of water and chemicals, such as foaming agents. The contractor should be allowed to plan how the muck is transported out of the tunnel. The contractor would need to either load the muck directly into haul trucks, or stockpile the materials on site until the material can be hauled away. The final design should contain limits on the proposed stockpile areas and volumes to prevent damage to adjacent properties, infrastructure, and the public. For example, stockpiles too close to the Little Cuyahoga River bank could cause instabilities and river bank failures. The final design should also provide for environmental controls to prevent the muck, runoff water, and dusts from impacting surrounding properties or sensitive water bodies. The City and Final Designer should decide if the muck disposal site location would be designated in the specifications or if the Contractor is free to locate an appropriate site.

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The muck generated by pressure face mining operations through soft ground conditions would likely not be suitable for reuse as engineered fill or even general fill material. During the mining process, various thickening and / or foaming agents may need to be added to the muck to efficiently transport it to the surface. The muck may be the consistency of fresh concrete when it comes through the TBM face and into the muck cars or conveyor. Although the material would dry over time, the material would likely be difficult to condition and compact due to the anticipated high silt and fine sand content. If utilized for non-structural purposes, such as landscaping berms, the material should be mounded with shallow side slopes (4H:1V or shallower), and internal drainage of the mound would be a significant consideration. The fine sands and silts are also unlikely to be acceptable for road borrow. The muck may be acceptable for daily cover at a landfill facility, although it is unlikely to meet permeability requirements for a landfill cap. The Final Designer should consider other uses for the material or identify a landfill operation willing to accept the material.

When the TBM is mining through the shale bedrock, and if ground conditioning agents are not utilized, the shale muck may be suitable for reuse as general fill. The excavated shale would likely consist of a wide range of particle sizes, ranging from dust to 3 to 4 foot long shale and siltstone slabs. The shale muck would generally contain significant amounts of gravel and silt, although higher clay shales may also be present. The material would likely have little to no plasticity. In the past, shales of this type have been used in mass filling operations. The shale fragments can be broken into smaller gravel-sized pieces using a sheep’s foot roller or disking machine. The gravel-sized pieces can then be compacted. Care should be taken to keep large shale pieces out of the fill stockpiles, as these pieces could bridge over voids during filling and cause problems in the future.

Depending upon the actual clay content of the shale pieces, some degradation of the shale would occur over time. The slake durability results provide some insight into the anticipated behavior.

3.5.4 OCI Tunnel Lining System

A circular precast concrete segment lining system (aka “concrete segments”) is likely to be the optimal temporary and permanent tunnel liner for the OCI Tunnel and Rack 16-17 consolidation sewer systems in the preliminary design. The precast concrete segments are one part of an integrated system designed to efficiently construct a 27-foot I.D. tunnel with two 1000-foot radius curves, and to minimize the risk of damaging surface structures and buried infrastructure. In addition to meeting the requirements listed above, precast concrete segments provide several other advantages to this project, including the following:

Concrete segments are cast in a controlled environment (precast concrete plant) and can be easily subjected to high quality control measures. The segments are cured under nearly ideal conditions and entirely visible prior to being placed in the tunnel.

Concrete segments are a one-pass system. They can be cast while the TBM is being manufactured, delivered, and assembled. Upon hole-out, the tunnel is fully lined.

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Concrete segments can help to reduce gas intrusion during construction,

For tunnels of this size, crown over-break in shales can be problematic for both mining and cast-in-place lining operations. Immediate segment placement and grouting can be used to mitigate this risk.

Two-pass lining systems are typically less stiff until the cast in place (CIP) lining is completed. Bending and / or movement of the lining can lead to surface settlements and damage to surface infrastructure.

Corrosion resistance of concrete segments can be improved in the casting plant by the addition and proper mixing of admixtures and / or fiber reinforcements. They can also be manufactured with corrosion protection systems embedded onto the inside face if desired.

The precast concrete segment design shown in the preliminary design drawings is referred to as a “Universal Ring.” Universal rings can be used for straight tunnel construction as well as curved tunnel construction in various directions. Each ring cast for the project has the same six segment pieces. The segment pieces themselves vary in shape so that, when assembled, each ring face has a slight taper. By placing the segment pieces in a planned pattern, and rotating each ring appropriately, each tapered ring fits tightly against the previous ring but the overall tunnel lining is a straight line. By changing the layout of the six segments, the ring face taper can be varied, and the tunnel can be “turned” to the left, right, up, or down. The preliminary design precast concrete segments for the OCI Tunnel were designed to allow for 1000 foot radius curves.

The following subsections describe the process, assumptions, codes and standards, and criteria utilized for design of the precast concrete segmental lining system shown on the Preliminary Design drawings in PER Appendix A. Due to the preliminary nature of the data available at the time of design, some of the parameters were developed from project data available at the time of this report, and some parameters were chosen based on experience and design best practices. The design calculations were performed in SI units. The parameters were converted to English units for the convenience of this report. If the parameters listed below are utilized for future designs, SI units should be utilized or the designer should perform their own conversions to choose conservative values in English units.

Design Input Parameters

Surcharge load: 418 pounds per square foot (psf) (20 kN/m2)

Steel reinforcement: Grade 60 steel (Grade 400 metric), with a yield strength of 60 kips per square inch (ksi) (400 MPa)

Characteristic strength of steel (bursting service limit state (SLS)): 30 ksi (200 MPa)

Width of segment: nominal 60 inches (1.5m)

Length of ram shoe: 40 inches (1044mm)

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Jacking pressure force: 400 kips (1780KN)

Design strength of concrete (28 days): 7000 psi (48MPa)

Poisson’s ratio of concrete: 0.2

Designed to meet the exposure class defined as “concrete subjected to moderate sulphate exposure”

7/8-inch (22mm) taper necessary to achieve a minimum tunnel centerline radius of 1000 feet (304.8m). This design criteria is based on an assumption of no packing and provides for no construction tolerance on the alignment

Ring build tolerance of 13/16 inches (20mm)

The final design should include checks for bolts and bolt holes, and an assessment of inserts such as grout valves, lifting eyes, etc

An un-factored primary grouting pressure of hydrostatic pressure plus 14.7 psi (1 bar)

Secondary grouting pressure: 10% of un-factored primary grouting

Design Criteria

Codes and Standards

Reinforced concrete design has been carried out in accordance with American Concrete Institute (ACI) requirements for concrete structures. Maximum crack allowances in the design were less than required by ACI 350 design standard for “normal environmental exposure” and “severe environmental exposure.”

Factors of Safety

Preliminary design was based on the following factors of safety:

Materials SLS Ultimate

Limit State (ULS)

Reinforced Concrete 1.0 1.25 Reinforcement 1.0 1.25 Loads SLS ULS Soil Pressure 1.0 1.5 Water Pressure (adverse) 1.0 1.5 Water Pressure (beneficial) 1.0 1.0 Self Weight 1.0 1.25 Primary Grouting 1.0 1.2 Secondary Grouting 1.0 1.2 Lifting and Handling 1.0 3.0 Stacking 1.0 1.5

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Design Methodology

The design of a segmental ring requires more than a structural analysis for ground loads and TBM ram loads applied to the segment. Design also requires consideration of the segment manufacturer’s process, the segmental lining storage methods, the segmental lining delivery system, segmental lining handling and erection loads, and the stress generated by bolt and sealing system.

Using the information provided in the Preliminary Design Geotechnical Data Report and design drawings, 13 critical sections were chosen along the preferred alignment (designated as “4B”) and 100 unique load cases were created. Table 3-4 lists the critical sections. The groundwater level varies for every load case because the groundwater table generally follows the existing ground surface profile. Load cases considered the effects of primary and secondary grouting, as well as build tolerances. A build deformation allowance of less than 1% of the external diameter was adopted for this design.

Table 3-4 Critical OCI Tunnel Lining Design Section

Case Station Closest SurfaceFeature Soil Type

Soil /RockElastic

Modulus

Depth Overburden Surcharge

(psi) (ft) (kPa)

1 71+50 OCIT 3 Shaft SandySilt/Silt 8,702 108 87% 418

2 68+50 Buchtel St. Clay/SiltyClay 7,251 112 85% 418

3 63+00 State St. Bridge Silt/SandySilt 8,702 125 82% 418

4 59+00 Locust St.Bridge

Sandy Silt /Silt 8,702 134 80% 418

5 53+50 East SideSR 59 Shale 1,269,080 139 100% 418

6 50+00 West SideSR 59 Shale 1,269,080 110 100% 418

7 39+50 W. Mill StreetBridge Shale 1,01, 264 108 100% 418

8 37+00 Market St.Bridge Shale 768,700 108 100% 418

9 26+00 W&LE Railroad Shale 1,551,904 59 100% 41810 25+00 W&LE Railroad Shale 1,551,904 95 100% 418

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Table 3-4 Critical OCI Tunnel Lining Design Section

Case Station Closest SurfaceFeature Soil Type

Soil /RockElastic

Modulus

Depth Overburden Surcharge

(psi) (ft) (kPa)

11 21+50Between

Railroad andNorth St.

Shale 1,551,904 48 100% 418

12 16+00 CVS Railroad Silty Sand 5,801 52 100% 418

13 12+00Between TBMPortal andHickory St.

Loose SiltySand 5,801 44 100% 418

Cross sections which governed segment reinforcement preliminary design were in the following tunnel reaches:

Between STA 11+00 (the tunnel launching portal) and STA 16+00, the geotechnical investigation indicates weak soils and mixed face conditions.

Sections adjacent to the Locust Street Bridge (approximately STA 59+00) and the State Street bridge (approximately STA 63+00).

Local stresses exceeded allowable stresses for critical sections 5 and 6, resulting in the need for additional steel to prevent localized edge crushing.

Preliminary structural design calculations included bursting stress calculations, handling and stacking load calculations, grouting pressure calculations, and build tolerance and oval-ing calculations. The segment design was analyzed by determining the structural actions imposed on circular tunnel linings at ultimate limit state, and by determining lining deformations at the liner’s serviceability limit state. The following subsections discuss each type of design calculation in more detail.

Structural Design using Closed Form Equations

The first design step utilized closed-form equations presented in technical papers by Muir-Wood A.M. (1975) and discussion by Curtis D.J and Morgan H.D. (1961). This approach uses a hole-in-a-plate theory which generally assumes the lining deforms into an elliptical shape. Specifically, the solutions are based on equilibrium equations for a hole in a pre-stressed plate. For each assumed loading, the lining resistance is considered when calculating the imposed maximum axial hoop loads and bending moment.

Bursting stresses

Segments were designed to have sufficient capacity to withstand local bursting stresses on the longitudinal joints of the segments (the joints between each of the segments in a

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single ring). Bursting stresses on the longitudinal joints are a result of the hoop forces in the ring, and are derived from the closed form equations discussed above.

Preliminary design consisted of an assessment of bursting stresses applied to the circumferential joints of the lining (the joint between two complete rings) based on assumed TBM jack ram compression forces. Later in the design project, the Final Designer should have better information regarding the likely TBM ram pressures, and should perform this check to confirm the current structural design is sufficient.

Handling and stacking loads

Each individual segment must have sufficient capacity to withstand stresses during handling, transport, stacking for storage, and installation. The Final Designer should have better information regarding these temporary conditions and should perform this check.

Joint Design

The segments in a single ring are held against their neighboring segment by pure ring compression and, in theory, experience no bending moments. The radial joint bolts and circumferential joint dowels are not designed to provide bending capacity. However, when the ring is loaded by various combinations of grout loads, ground loads, and / or ram loads, the segments can rotate at the joint. The calculated joint rotation when considered in combination with applied axial forces could cause the development of an asymmetric strain profile across the joint faces, with the greatest strain at the point of rotation. This pressure distribution in turn causes flexural bending within segments.

Segments are designed to resist this bending with reinforcement either in the form of steel fibers or conventional steel reinforcement bars. Segments are also designed to take into account the tensile bursting pressures accompanying segment-to-segment contact pressures. Preliminary segment design was based upon the use of conventional steel reinforcement. Additional analyses and alternate segment reinforcement designs should be considered during the detailed design stage.

General Design Considerations

The Final Designer should perform a check for seismic loading.

Gasket grooves shown on the drawings would be adjusted during detailed design and constructed to suit manufacturer’s requirements.

3.5.5 Rack 16-17 Consolidation Sewer Tunnel

The Rack 16-17 consolidation sewer would be constructed using a TBM equipped to operate with a pressurized face, likely be lined with precast concrete segments to support the ground, and provide a barrier to groundwater behind the TBM. A profile drawing of the proposed tunnel and available soils information is presented as Figure 2-14. Four test borings have been completed along this alignment. The boring spacing is approximately 450 feet for the east half of the alignment, but there are currently no borings between Locust and Dart Streets. Final Design investigation should consist of at

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least one additional boring in this stretch to confirm subsurface conditions. The investigation should also consist of several test borings at the east end of the alignment.

Based on the available data, the Rack 16-17 Consolidation Sewer TBM would be launched from the OCIT-3 shaft into medium dense fine to coarse sands, with possible thin layers of silty clay and course gravels. At the OCIT-3 shaft, the TBM would have approximately 30 feet of ground cover, and the groundwater table is anticipated to be less than 10 feet above the tunnel crown.

Proceeding east from OCIT-3 shaft, the TBM would remain in medium dense to loose, fine to coarse sand layers until reaching Locust Street. Through the stretch from OCIT-3 to Locust, the groundwater table is anticipated to increase to approximately 20 feet above the tunnel crown (about 1/2 bar of pressure), and the tunnel cover would increase to approximately 60 feet (4 tunnel diameters). From Locust Street heading east, the ground conditions would become more variable, consisting of interbedded medium dense sands, silts, clays, and gravel layers. The groundwater table and tunnel cover would generally decrease approaching the Ohio Canal.

While passing beneath the Ohio Canal, the TBM would have approximately 25 feet (about 2 tunnel diameters) of cover.

The Rack 16-17 Consolidation Sewer alignment consists of approximately 100 feet of straight bore, followed by approximately 900 feet of curve on a 750 foot radius, then another 140 feet of straight tunnel, followed by a reverse 750 foot radius curve extending 450 feet, and finally a straight segment approximately 400 feet into the Rack 16-17 Drop Shaft. The alignment was chosen to be bored without intermediate turning or jacking shafts, and to stay within the Exchange Street Right-of-Way. Finally, the east end of the alignment has been chosen to avoid the Exchange Street Bridge, Howe House, and a large number of utilities that cross the Ohio Canal at Exchange Street.

Portal Designs

The Rack 16-17 Consolidation Sewer would require a soft ground tunnel eye at the OCIT-3 shaft to facilitate TBM launching. The loose sand conditions at the OCIT-3 shaft location would most likely require that the TBM be launched into an area of “improved” ground (e.g. jet grouted soil). Localized dewatering along the alignment may allow for launching and sealing of the tunnel liner. Dewatering plans would have to consider potential effects on the adjacent ODOT bridges, which are supported on shallow foundations bearing on the granular layers.

Current plans call for the OCIT-3 shaft to be constructed using a slurry wall TERS. The Rack 16-17 tunnel invert would be approximately 45 feet below grade. The slurry wall panels would have to be built to accommodate this launching.

On the receiving side, the TBM would most likely arrive at the Rack 16-17 Drop Shaft in similar soil conditions. There is very little area available surrounding the shaft for ground improvements to receive the TBM. In addition, plans for dewatering at the east end of the alignment would have to consider potential effects on the Ohio Canal, Exchange Street Bridge, Canal Park Stadium, OCI, and Towpath Trail. This portal may need to be constructed as a gasketed entry eye.

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Boring Machine Selection and Performance

The Rack 16-17 TBM would have to navigate a nearly continuous curve along Exchange Street. The TBM would also have to provide excellent face control to reduce potential settlements underneath Exchange Street, which could also impact buildings adjacent to the tunnel. Although the groundwater pressure is relatively low (<1/2 bar), the ground conditions vary from coarse sands and gravels on the west end to silts on the east end. While it is reasonable to assume that at least an EPB machine would be necessary, additional grain size testing of the tunnel zone soils is necessary to determine whether a slurry face (SPB machine) is necessary.

The performance characteristics of the Rack 16-17 TBM are anticipated to be similar to the OCI Tunnel TBM operating in the soft ground conditions. Advancement rates are anticipated to be approximately 5 to 6 feet per hour.

Risks of TBM Tunneling

Similar to the OCI Tunnel discussion earlier, the risks for the Rack 16-17 tunneling are related to excessive ground loss or heaving at the surface due to conditions at the face, unintentional ground dewatering ahead and around the TBM, and the presence of cobbles and / or boulders, especially as the TBM reaches the project east end. However, the Rack 16-17 tunnel has several unique risks as follows:

Close proximity to existing buildings and sensitive facilities (e.g. Akron General Hospital and the Howe House),

Excavation of an “emergency” shaft to address conditions at the TBM face or to affect a “rescue” has the potential to have a much greater impact on the public. However, depending upon the exact location of the shaft in the Exchange Street Right-of-Way, the street is large enough that a few lanes could be closed for long periods of time without the impact.

The Rack 16-17 tunnel would pass below the Ohio Canal and the Ohio Canal Interceptor with little clearance. The sensitivity of these structures must be assessed during final design and a plan developed to protect the infrastructure.

Exchange Street contains a significant number of utilities, including buried steam, electric, water, and phone lines. Final design would need to assess utility sensitivity and prepare a plan to monitor the utilities for movement during and after tunneling activities.

Tunnel Lining System

Due to the multiple curves required for this alignment and the potential running ground conditions, a circular precast concrete segment lining system (aka “concrete segments”) would likely be the optimal temporary and permanent tunnel liner for the Rack 16-17 Consolidation Sewer. Precast concrete segments could be one part of an integrated system designed to efficiently construct a 12 foot (3.7 meter) I.D. tunnel with two 750 foot radius curves, and may minimize the risk of damaging surface structures and buried infrastructure.

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The Rack 16-17 precast concrete segment design shown in the preliminary design drawings is a “Universal Ring,” identical in concept to the segment design for the OCI Tunnel lining system.

The following subsections describe the process, assumptions, codes and standards, and criteria utilized for preliminary design of the Rack 16-17 precast concrete segmental lining system. The segment design is shown on the Preliminary Design drawings in PER Appendix A. Due to the preliminary nature of data available at the time of this analysis, some parameters were developed from project data and some parameters were chosen based on experience and design best practices. The design calculations were performed in SI units. The parameters were converted to English units for the convenience of this report. If the parameters listed below are utilized for future designs, SI units should be utilized or the designer should choose appropriate values in English units.

Significant Design Input Parameters

Surcharge load: 418 pounds per square foot (psf) (20 kN/m2)

Steel reinforcement: Grade 60 steel (Grade 400 metric), with a yield strength of 60 kips per square inch (ksi) (400 MPa)

Characteristic strength of steel (bursting service limit state (SLS)): 30 ksi (200 MPa)

Width of segment: nominal 40 inches (1.0m)

Length of ram shoe: 19 inches (493mm)

Jacking force: 215 kips (959 KN)

Design strength of concrete (28 days): 7000 psi (48MPa)

Poisson’s ratio of concrete: 0.2

3/8-inch (10mm) taper necessary to achieve a minimum tunnel centerline radius of 750 feet (228.6 m). This design criteria is based on an assumption of no packing and provides for no construction tolerance on the alignment

No specific checks for bolts and bolt holes, and an assessment of inserts such as grout valves, lifting eyes, etc

A factored primary grouting pressure of hydrostatic pressure plus 1 bar has been assumed.

Secondary grouting pressure: 10% of un-factored primary grouting

Design Criteria

Codes and Standards

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Reinforced concrete design was carried out in accordance with ACI 318-11 and ACI 350-06. Factored loads and material strengths were adopted using factors of safety based on ACI 318-11 and ACI 350-06. The British Standard, BS 8110, was used for some parts of the segment design.

Factors of Safety

Preliminary design was based on the following factors of safety:

Materials SLSUltimate

Limit State (ULS)

Reinforced Concrete 1.0 1.2 Reinforcement 1.0 1.2 Loads SLS ULS Soil Pressure 1.0 1.6 Water Pressure (adverse) 1.0 1.6 Water Pressure (beneficial) 1.0 1.0 Self Weight 1.0 1.2 Primary Grouting 1.0 1.2 Secondary Grouting 1.0 1.2 Lifting and Handling 1.0 3.0 Stacking 1.0 1.15

Design Methodology

Design of a segmental ring requires more than a structural analysis for ground loads and TBM ram loads applied to the segment. Design also requires consideration of the segment manufacturer’s process, the segmental lining storage methods, the segmental lining delivery system, segmental lining handling and erection loads, and the stress generated by bolt and sealing system. For preliminary design, some of these items are unknown, such as manufacturer’s process. As a result, these designs are considered conceptual and preliminary in nature.

Using the information provided in the OCI Tunnel Geotechnical Data Report and August, 2012 Draft PER design drawings, critical sections were chosen at 8 unique centerline stations along the alignment and 100 unique load cases were created. Sections were chosen based on the proximity of important infrastructure to the tunnel alignment and the ground condition. This pertains to different soil type conditions at the elevation of the tunnel excavation, different water table depths, maximum and minimum depth of overburden and surcharge at ground elevation. Table 3-5 lists the critical sections. The groundwater level varies for every load case because the groundwater table is assumed to generally follow the existing ground surface profile. Load cases considered the effects of primary and secondary grouting, as well as build tolerances. A build deformation allowance of less than 1% of the external diameter was adopted for this design.

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Table 3-5 Critical Design Sections for Rack 16-17 Consolidation Sewer Tunnel Liner

Case Station Soil Type

Soil /RockElastic

Modulus

Depth Overburden Surcharge

WaterHeightRelativeto TunnelSpringline

(psi) (ft) (kPa) (ft)

1 51+00 Silty Sand 20 36 100% 20 16.4

2 62+55 SandySilt/Silt 30 75.5 100% 20 16.4

3 69+30 Silt/SandySilt 40 34.4 100% 20 26.2

4 69+30 Silt/SandySilt 40 34.4 100% 20 3.3

5 69+50 Silt/SandySilt 40 31.2 100% 20 26.2

6 69+50 Silt/SandySilt 40 31.2 100% 20 0.66

7 69+80 SandySilt/Silt 40 24.6 100% 20 20.7

8 69+80 SandySilt/Silt 40 24.6 100% 20 7.3

Conclusions

Interaction diagrams for the closed form equation analyses showed that an approximate 9.8 inch (250 mm) thick reinforced concrete segment should be adequate. The section should also be adequate for shear and should not require any stirrup reinforcement or reinforcement for the radial and circumferential joints to prevent bursting or local crushing. Bursting stresses calculated at the radial joints may be less than design values due to the articulation of the tunnel lining, which would allow the moments in the ring to redistribute.

Each segment was checked for stacking and handling loads, and the calculations showed that the mean flexural tensile strength should exceed the maximum stress induced on the segments due to the self-weight and dynamic loads applied to the segment, and therefore the segment should be sufficient to withstand handling loads.

A similar calculation was carried out to check the allowable limit when stacking the segments. The result shows that the limit on stacking is likely to be a maximum of six (6) segments high.

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General Design Considerations

During detailed design, the following items should be addressed:

The Final Designer should perform a check for seismic loading.

Preliminary segment design was based upon the use of conventional steel reinforcement. Additional analyses and alternate segment reinforcement designs should be considered during the detailed design stage.

Final designer should provide checks for bolts and bolt holes, and an assessment of inserts such as grout valves, lifting eyes, etc. Cam and pockets may need to be considered for accuracy of segment installation.

Gasket grooves shown on the drawings would be adjusted during detailed design and constructed to suit manufacturer’s requirements.

3.6 Odor Control Considerations

Adequate air flow was determined to be the most efficient passive method of reducing potential for odors at surface structures associated with the storage tunnel and consolidation sewers. As currently designed, for events with less flow than the typical year storm, air would be conveyed through the system and exit at the downstream end of the tunnel. As is typical with storage tunnels, once the tunnel is filled, no air flow conveyance can be accommodated through the tunnel. Consolidation sewers have been designed to maintain air flow during storm events to reduce potential odor issues near sensitive areas such as Canal Park Stadium. The tunnel would fill and air flow would be restricted eight (8) times during a typical year. At these times, air conveyed in the consolidation sewers would be expelled at the OCIT-2 and OCIT-3 drop shafts. The Final Designer should coordinate with the Odor Control consultant to consider the need for odor mitigation measures at OCIT-2 and OCIT-3 drop shafts.

While the tunnel grade is adequate to convey most sediment, some isolated collection of sediment is likely to occur at some points in the system. The Final Designer should coordinate with the Odor Control consultant to consider the need and appropriate methods for flushing and cleaning the storage tunnel to prevent sediment decomposition and the potential for related odor generation.

To mitigate potential odor issues at the downstream end of the tunnel, the Final Designer may need to coordinate with the Odor Control consultant to incorporate additional measures, a ventilation system, or odor reducing / masking facilities.

3.7 Corrosion Considerations

Corrosion can be a serious issue in tunnels conveying dry weather flows. Hydrogen sulfide (H2S) gas can be generated in areas of turbulent flow. Special consideration should be given to areas near drop shafts OCIT-2 and OCIT-3. Sacrificial concrete, special concrete, or liners could be considered in these areas. The Final Designer should consider the likelihood of adverse corrosion impacts, and whether measures to reduce the potential for corrosion would be appropriate. The current liner designs shown in PER Appendix A do not account for sacrificial concrete.

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Sewage conveyance and storage structures of this type are often designed for at least a 50 year life. However, as evidenced by many of the existing brick, clay, and concrete sewers in use throughout the United States, the generally constant temperature and humidity levels in underground tunnels can help to extend the life expectancy of well-built sewers past the design life. For the OCI Tunnel, corrosion and surcharging forces are likely to be the primary degrading forces. Except catastrophic failures, occasional maintenance of the tunnel lining may be needed to maintain concrete coverage of reinforcing steel and to maintain the ring compression capacity of the concrete ring that is the tunnel liner. Maintenance may take the form of surface repairs, such as shotcrete and/or concrete patching. Assuming a localized shotcrete repair section that extends 3 inches into the tunnel beyond the existing tunnel face, there would be approximately 4% volume loss from the available tunnel cross section area in that area. If the entire tunnel were to be lined with this shotcrete, the tunnel could lose one million gallons in storage capacity. The City may choose to accommodate this worst case scenario by over sizing the tunnel by about 8 inches.

3.8 Construction Access and Staging Sites

Several OCI Tunnel work components may be in construction under separate project contracts performed simultaneously. Each contractor would require a staging and laydown area. Preliminary design drawings illustrate the proposed staging and laydown areas. The sites are discussed in the following sections and are shown on Figure 3-10.

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Figure 3-10

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OCI Tunnel Contractor – Available Mining Site and Staging Site

The OCI Tunnel contractor would likely require the largest laydown and staging area. The portal shaft entry would likely allow for TBM and trailing gear assembly on the site prior to launch. Staging areas would likely be required for muck storage; the square footage required may depend upon City-permitted trucking hours and noise ordinance curfews. Contractors may elect to build a precast concrete production plant to make the precast concrete lining segments.

The City has acquired property for two staging areas for the OCI Tunnel contractor to use for staging and support of mining operations: Hickory Street and Otto Street Sites. The first area is called the Hickory Street Site and is bounded by Hickory Street, Cuyahoga Valley Scenic Railroad, Ohio Canal Corridor next to the Little Cuyahoga River, and residential properties on the west side of N. Maple Street. The OCI Tunnel launch portal is near the east end of the available area, and the site extends about 650 feet west of the intersection of Hickory Street and the Cuyahoga Valley Scenic Railroad. This site is intended to be the OCI Tunnel mining site, the future site of OCIT-1 diversion structure for connection of the OCI Tunnel to the LCI.

The site currently has limited access, so access improvements are proposed as part of the OCI Tunnel project site. One option is to construct an earthen berm along Hickory Street and construct an access ramp onto the site. There is approximately 40 feet of vertical drop from Hickory Street to the site, so the access ramp may need to be 500 to 700 feet long to provide a reasonable road grade. This option would result in disturbance to the surrounding community due to continuous truck traffic for the duration of construction.

A second option for access to the Hickory Street Site is construction of a temporary bridge from Otto Street on the north side of the Little Cuyahoga River. This temporary bridge would likely be designed, built, used for construction access, and then removed by the OCI Tunnel contractor. Access via the bridge from Otto Street is preferred to limit impacts to the residents on Hickory Street. Ohio Edison high voltage power lines extend along the north bank of the Little Cuyahoga River. The bridge would need to be designed to provide appropriate clearance. Final Designer should also be aware that recent river bank erosion has caused Ohio Edison to plan for a slight relocation of the transmission tower near the proposed bridge.

The City has expressed interest in constructing the Hickory Street Site access bridge as a permanent structure for EHRT O&M access instead of a temporary structure. The OCI Tunnel contractor would construct the bridge for construction and then modify the structure after construction to be aesthetically pleasing for the surrounding area. The bridge would be used after OCI Tunnel construction to provide O&M access to the OCIT-1 Diversion Structure and EHRT site. The OPCC shown in PER Appendix AA shows the cost for a temporary bridge structure, so if a permanent structure is determined to be preferred during final design, the cost would need adjusted appropriately.

The second site available for the OCI Tunnel contractor to stage equipment is at the southeast corner of Otto Street and Cuyahoga Street. The City has acquired residences and buildings in the area bounded by Otto Street, Cuyahoga Street, Little Cuyahoga River, and N. Howard Street to make the property available. The City may demolish former residences in this area prior to the start of the OCI Tunnel project. A large

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warehouse facility currently exists on the staging area. The City may allow the contractor to utilize the warehouse facility if desired and then demolish the facility at the end of construction. Access to the site would be from Cuyahoga Street.

The Center Street Site would be provided to the OCI Tunnel contractor for staging area on the east side of the intersection of W. Center Street and Dart Avenue. Two buildings currently occupy the site. Demolition of these buildings could be done by the City prior to the OCI Tunnel contract or included in the contractor’s scope of work This site would not be available before January 1, 2015.

Finally, the Exchange Street site at the OCIT-3 drop shaft site would provide the contractor’s work in the westernmost area of the existing parcel at the corner of Dart and Exchange Streets. The OCI Tunnel contractor would likely remove the TBM from the shaft at this site. The OCI Tunnel contractor and the OCIT-3CS contractor may both need this site for construction staging.

OCIT-1CS Contractor Staging Site

The OCIT-1CS contractor will be responsible for consolidation sewer construction in the area of Hickory Street, North Street, and Tarbell Street. The City is acquiring property and easements at the southeast corner of N. Maple and North Streets for the OCIT-1CS contractor to utilize for staging and laydown. The staging area would be generally bounded by North Street, Maple Street, Wheeling and Lake Erie Railroad, and the existing First Energy electrical substation property. The City may demolish existing houses in this area prior to the OCIT-1CS contract. The area has significant topography variations on site and would need to be cleared, grubbed, and graded for the contractor’s use.

OCIT-2 Shaft Area Staging Areas

The OCIT-2CS contractor would likely be responsible for construction of consolidation sewers and drop shafts in contract area 2, except the OCIT-2 drop shaft and OCI Tunnel. The OCIT-2CS staging area could be a City-owned parking lot located on the south side of Glendale and about 100 feet west of Rand Street. The proposed construction staging area is a long area approximately 1 ½ acres in size. The OCIT-2CS contractor would also need access to the OCIT-2 drop shaft area discussed above.

OCIT-3CS Staging Areas

The OCIT-3CS contractor would likely be responsible for construction of the Rack 16-17 Consolidation Sewer (under Exchange Street) as well as structures at the Rack 16-17 Drop Shaft area. The OCIT-3CS contractor would likely utilize part of the temporary construction work area at the OCIT-3 drop shaft (ACH parking lot).

The City of Akron is acquiring property and easements for the OCIT-3CS contractor to utilize for staging area. The property bounded by Bowery Street, Exchange Street, Water Street, and the existing Considine Building site. This site is approximately 1 acre.

The OCIT-3CS would also need a work area in a City-owned parking lot south of the Canal Park Stadium. This area is currently used for parking by Canal Park employees and alternative parking would need to be provided. Alternate parking could potentially

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be provided in a lot south of the State Street Bridge in the Garden Alley access point to the stadium. Access to maintenance facilities for Canal Park is also through this parking area and would need to be maintained during construction.

3.9 Local Area Construction Impacts

The following sub-sections discuss anticipated impacts to local areas during construction of the OCI Tunnel projects.

3.9.1 Noise Impacts

Noise impact study results indicate OCI Tunnel project construction activities may create significant noise levels, exceeding the FTA Noise Abatement Category for the current land uses adjacent to the OCI Tunnel project. Final design should establish noise abatement criteria acceptable to the City and, at a minimum, meets the guidelines in FHWA guidelines described in the Preliminary Noise Analysis report, provided in PER Appendix V. Final design should, at a minimum, include additional analyses of potential impacted areas on the tunnel alignment, and specifically account for potential impact to residential neighborhoods around the Hickory Street Site, near the OCIT-1 construction staging area, Akron Children’s Hospital, and Canal Park Stadium area. Final analyses should account for construction sites, account for noise reductions due to existing buildings and terrain features, and be based on a more advanced understanding of construction methods likely to be used for the project. Predicted truck traffic volume should be confirmed, and special attention should be paid to areas with road grades with potential to cause construction trucks to generate greater acceleration or braking noise. The Final Designer should consider design mitigation strategies for areas which may be impacted by construction noise. Examples of mitigation measures are listed below:

Alter the design and layout of construction and staging areas to take advantage of natural terrain features with the potential to block sound propagation to nearby residences.

Designate specific areas of the contractor’s staging site for stationary equipment such as compressors and generators to keep them far from nearby residences as possible.

Develop construction work hour restrictions for specific areas and types of noise-generating work. Permit noisy equipment to operate only during the day when the majority of individuals would ordinarily be affected by the noise are either not present or are engaged in less noise sensitive activities.

Develop contract requirements which specify use of the lowest noise-generating methods possible. For example, piling or sheet piling may be vibrated in place or driven with a hydraulic hammer instead of a simple external combustion impact hammer.

Write muffler requirements into the OCI Tunnel contracts.

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Design temporary sound walls to block construction activity noises from sensitive areas.

3.9.2 Potential Blasting Vibration Effects

Based on planned shaft depth and rock excavation quantity required to construct the OCIT-2 shaft, contractor’s means and methods may likely consist of a form of blasting for rock excavation. Structures are present within 125 ft of the shaft site. Even assuming the contractor’s use of cautious blast covering and confinement methods described in this report, there is some risk damage could occur. If the City is going to allow blasting, consideration should be given in setting a PPV limit of 0.5 inches per second (ips) to reduce the likelihood damage would result from blast-induced vibration. Despite this control, some vibration damage claims could still occur.

In addition to the vibration limit, the City should also include the following requirements and steps in the specifications:

The specifications should require the contractor to retain a specialty engineer with expertise in blasting and soil and rock dynamics to design the blasting program and provide engineering calculations estimating the effect proposed blasting may have on adjacent facilities.

As part of the contractor’s submittal, the radial distance from the blast where the anticipated vibrations would be below 0.5 ips, should be submitted and approved by the City.

Specifications should require that the contractor perform a pre-blasting survey on structures within the blast radius of influence.

Contractors performing work in Ohio would have general construction permits issued by the State. The State of Ohio does not require licenses for construction blasters. However for this close-in blasting work with exposure to many structures, utilities and roadways it is common practice to specify Blaster(s)-In-Charge have a valid blaster's license issued by another state. The Blaster(s)-In-Charge should also have documented experience, supported by owner references, in performing construction blasting in urban areas on at least two projects comparable in size and complexity to the work. Blasters should also have a minimum total of five years direct experience with blasting, within the previous ten years.

Companies making, using, transporting, or having access to explosive materials must have specific licenses issued by the Federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). There are additional State of Ohio PUCO laws for commercial drivers who transport explosives. The contractor should be required to comply with applicable laws and regulations regarding those who make, use, transport, store, or have access to explosive materials.

The contractor should be required to perform vibration monitoring for every blast. See recommendations in PER Appendix W for proposed equipment and requirements. Vibration monitoring equipment capable of monitoring peak velocity and recording complete time histories of the blast “pulse” should be

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placed adjacent to the structure within the radius of influence. It is standard practice to specify 4-channel seismograph recorders be deployed to measure and record blast-induced particle velocity simultaneously along three mutually perpendicular axes (vertical, transverse and longitudinal). A 2-Hz response microphone is used to measure the intensity of air-overpressure on the fourth channel. Velocity transducers measure motion with a flat frequency response from 2 to 200 Hz. For this urban work, at least three seismographs should be used to monitor effects of blasts. Portable units would typically be setup at the closest structures and on the ground above selected utilities.

The City should consider retaining a specialist to perform independent vibration monitoring as a quality control measure on the contractor’s monitoring program.

Additional A or C-scale measurements of audible-only noise components created by construction activities can be measured with standard sound level devices if desired to confirm construction noise impacts. Note for compliance purposes, only 2-Hz response measurements done with standard compliance seismographs should be used to evaluate blast-induced noise because these instruments measure infrasonic (impulsive) noise that affects structures.

The City’s current Construction and Materials Specifications and construction contracts should be reviewed for their requirements and limitations on controlled construction blasting. The blasting limits may need to be updated to reflect current research and standard practice.

Due to the location of the excavations and potential blasting impacts to adjacent property, utilities, roads and railways, the City and Final Designer should implement an extensive outreach program

3.9.3 Settlement Effects

Ground movement is possible for excavation beneath the ground surface. The magnitude and extent of deformations for an internally braced retaining wall system, such as the OCIT-2 and OCIT-3 shafts, depends on deformed soils stress-strain properties, support system stiffness, excavation geometry, workmanship, construction sequencing, surcharge loading, and other criteria. As such, it is not possible to develop an exact magnitude and extent of ground movement prior to construction. However, the Final Designer should pay particular attention to large utilities adjacent to the shafts, such as steam or water lines. In granular soils such as those present at OCIT-3 drop shaft, limiting groundwater infiltration and soil loss can be nearly as important to prevent damage, as building a stiff wall system. Final Designer should also pay close attention to the Wheeling and Lake Erie Railroad and Cuyahoga Valley Scenic Railroad where they cross the OCI Tunnel alignment.

Ground surface settlement due to tunneling in soil is directly related to TBM performance and the lining method. Poor face control or incorrect compensation for mixed face conditions can lead to either taking in of too much ground for advancement (normally manifesting as a void or settlement trough at the surface), or taking in of not enough ground for advancement (normally manifesting itself as heaving ground over the TBM). For preliminary design purposes, relationships developed by Rankine (1988) and O’Reilly and New (1982) were used to develop ground surface settlement estimate due

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to tunneling operations. Figure 3-11 presents an estimate of the upper bound of expected ground surface settlement behavior due to tunneling in soft and mixed ground conditions. This estimate assumes 5% volume loss at the face of the TBM. With a well-designed TBM operated by a qualified contractor, actual settlement could be nearly an order of magnitude smaller than shown.

Figure 3-11 Theoretical Settlement above OCI Tunnel STA 58+50

Predicting ground surface settlement due to tunneling in rock is even more difficult. In theory, if the TBM is in a stable face of rock and the liner is properly grouted immediately after placement, there would be no settlement. However, a conservative estimate to account for overbreak, squeezing, etc. would be ½-inch total settlement at the centerline of the tunnel.

3.9.4 Maintenance of Traffic

Construction impacts to traffic are anticipated to be concentrated at the shaft and construction staging areas. In general, the Contractor should coordinate traffic maintenance with the following agencies:

City of Akron (City Streets, S.R. 18, Dart Avenue and Rand Street), and

Ohio Department of Transportation (ODOT) District 4 (S.R. 59 and associated ramps and bridges).

Summit County Engineer (Maintenance of Traffic and hauling routes)

The following paragraphs summarize the likely impacts for each of the three general areas of the OCI Tunnel project:

OCIT-1 Area (Cuyahoga St. / Otto St., and Hickory Street / E. North St. Areas)

Preliminary Design plans currently show two options for site access to the OCI Tunnel mining site. Assuming the contractor utilizes the proposed bridge in lieu

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of the Hickory Street access road option, the following streets would have an increase in construction traffic, including a substantial number of muck hauling trucks (estimated at 100 to 200 trucks per day):

o Otto Street

o Cuyahoga Street

o North Howard Street

o Dart Avenue

o Exchange Street

Depending upon load and height restrictions and the size of the loads being delivered, construction traffic may also utilize North Howard to Tallmadge Avenue heading east to S.R. 8. This increase in traffic could impact businesses on Cuyahoga Street by interfering with customer access and deliveries; it could affect residences on Cuyahoga and Otto Streets with noise and dust; it could affect the new residential condominium (Northside Lofts) by increasing congestion on North Howard Street and increasing traffic noise.

If deliveries and muck transport utilize the Cuyahoga Street – Tallmadge Ave. – S.R. 8 route, the traffic would affect more residential and commercial areas, including several school zones, church areas, and shopping centers. City bus stops are frequent on Tallmadge Avenue and N. Howard Street.

Preliminary design requires construction in the intersection of E. North Street and Hickory Street. This could require a temporary shutdown of the westbound lane and a detour for westbound traffic.

Proposed construction alongside Hickory Street would require temporary one-lane closures to accommodate excavating equipment, hauling trucks, and pipe material trucks. A detour may not be needed.

Relocation of the existing Rack 24 overflow pipe and the 36-inch water main (to allow construction of the OCI Tunnel) could require temporary shutdowns of Hickory Street. The shutdowns should be of short duration (measured in days) to accommodate excavation, installation, and temporary patching of Hickory.

The staging area for sewer installation along Hickory Street is at the southeast corner of E. North Street and N Maple Avenue. The E. North street traffic could be impacted by frequent truck and equipment traffic turning into the staging area.

OCI Tunnel project work would impact traffic in the areas along Hickory Street and North Street. The staging area for this work is anticipated to be at the southeast corner of North and Maple Streets, adjacent to the Aetna electrical substation.

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Tarbell Street would be affected by construction traffic for the construction of the Rack 24 consolidation sewer. This could affect access to the businesses on Tarbell. This work should not require the complete shutdown of Tarbell.

OCIT-2 Area (Market St. / Rand St. and Market St. / Dart Ave. Areas)

Staging areas for this work are anticipated to be located in the existing City parking lot and grassy areas located on the south side of Glendale Avenue, between Rand and Locust Streets. Current schedule estimates suggest this staging area may be needed for up to 2-1/2 years. This would require relocating the current parking customers for the entire period. There do not appear to be a significant number of businesses or residences in this area. However, the OCIT-2 shaft and related Rack 18 Diversion Structure and consolidation sewers are currently proposed to be built in a ¼-acre land area. This is a relatively small area. As a result, there could likely be significant construction traffic on Rand Street (to and from S.R. 59), Glendale Avenue (to and from the staging area), and Market Street (to and from S.R. 59). There is currently no traffic light at Market and Rand Streets, which means construction traffic waiting to turn could cause congestion. In addition, the Mill Street Bridge coming from the east side of S.R. 59 appears to be a route for downtown workers to get either to S.R. 59 west, Glendale Avenue, or Market Street.

Current plans require closure of Rand Street and likely the West Mill Street Bridge for construction of a 36-inch sanitary sewer. However, the pipe invert is 35 feet below grade, so this may be constructed using trenchless methods. The Rack 18 Diversion Structure could be constructed without road closures. The 120-inch Rack 18 Consolidation Sewer could be built by trenchless methods, or could require shutdown of Glendale Avenue.

Rand Street is anticipated to be closed intermittently between Mill Street and Market Street to facilitate construction of the OCIT-2 shaft. Traffic on Mill Street would be routed south to S.R. 59 or to Willis Avenue. Traffic on Market Street could be routed to South Maple and then to Glendale Avenue or Exchange Street.

On the east side of S.R. 59, construction could occur at the southeast corner of Market Street and Dart Avenue. Due to downtown office buildings proximity between Main Street and Dart Avenue, this is a heavily travelled part of Dart Avenue. In addition, the proposed project site is located across the street from the Federal Courthouse. Construction traffic, including equipment, personnel, and muck hauling trucks, could cause significant congestion at the intersection of Market Street and Dart Avenue. The traffic signal at Market Street could be modified to help alleviate some of the congestion. The City may want to consider restricting trucking hours in this area to reduce the impact to commuting traffic to and from downtown Akron.

Construction of the Rack 19 Drop Shaft system in this area could require closure of one or two lanes of eastbound West Market Street to construct the new Rack 19 Diversion Structure.

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There are several proposed tie-ins and changes to the Ohio Canal Interceptor and Ohio Canal Enclosure. The tie-ins are located generally on the east side of westbound S.R. 59, between the two West Mill Street Bridges over S.R. 59. The contractor could require a temporary shutdown of the S.R. 59 lane and shoulder, as well as the Dart Avenue ramp to S.R. 59 west, to facilitate some of this work.

For the Rack 37 modification, the contractor may require a shutdown of the southbound lanes of Main Street, between Bowery Street and University Avenue. This work is likely to be entirely open cut construction, and would require excavation, trenching, and pavement restoration. This work could be completed in approximately two (2) months.

Construction in the OCIT-2 project area could impact numerous downtown workers who utilize the underground parking garages located between Dart and Main Streets. The maintenance of traffic plan for Dart and Main Street should be designed to prevent congestion downtown during rush hour periods and downtown events.

OCIT-3 Area (Center St./Dart Ave. to Exchange St./Dart Ave. to Main St./Exchange St.)

The OCIT-3 work area begins at the intersection of West Center Street and Dart Avenue. A construction staging area would be located at the northeast corner of this intersection. The contractor could utilize this area for staging of materials and equipment. Traffic impacts are likely to be primarily material deliveries on Dart Avenue and Center Street.

Construction activities at the OCIT-3 Drop Shaft site (northeast corner of Exchange Street and Dart Avenue) could include the following:

o Construction of the OCIT-3 Drop Shaft for retrieval of the OCI Tunnel TBM (3 months)

o Retrieval and disassembly of the OCI Tunnel TBM (1 month)

o Launching and mucking operations from the Rack 16-17 Consolidation Sewer tunnel (approximately 9 months)

o Construction of final baffle drop structure

During construction of the OCIT-3 Drop Shaft, Exchange Street and Dart Avenue could see an increase in hauling truck traffic, on the order of 100 to 200 trucks per day. Once the shaft is completed, the site activity would likely be reduced until the Rack 16-17 contractor has a TBM to mobilize and /or the OCI Tunnel TBM arrives at the shaft. Once the OCI Tunnel TBM arrives at the shaft site, there would be TBM parts and trailing gear brought up and shipped out. Most of those items are expected to be transported via S.R. 59 without significant impact to Exchange Street.

Construction of the Rack 16-17 Consolidation Sewer should consist of significant equipment and muck hauling from the OCIT-3 drop shaft site for a period of approximately 4 to 6 months. Most haul trucks are anticipated to utilize

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Exchange Street, Rand Street, and S.R. 59 for destination access. This truck traffic could impact traffic movement at the intersection of Exchange and Rand Streets.

Construction of the Rack16-17 Diversion Structure, Consolidation Sewer, and Drop Shaft could increase congestion on Exchange Street, in areas surrounding the Akron Children’s Hospital, and areas around Main and Exchange Streets. Construction traffic to and from the Rack 16-17 Diversion Structure is anticipated to include materials delivery (concrete trucks, sheet piling, reinforcing steel) and muck hauling (drop shaft and diversion structure). The muck traffic is anticipated to be similar to a large sewer construction job and would likely be less than the traffic from tunnel mucking operations. Preliminary design currently does not require excavation or significant work in Exchange Street.

Construction of the Rack 16-17 Diversion Structure and Drop Shaft could require closure and detouring of the Towpath Trail. The anticipated total duration is 9 months, and may be split into two periods. The first period could be 6 months for construction of the diversion structure and shaft. The second period could begin after the TBM is retrieved and consist of finishing the Rack 16-17 Drop Shaft.

Other Pipe Rehab Areas

Preliminary design allows for rehabilitation work in sewers in the following areas:

o North Street near Hickory Street

o The Ohio Canal Interceptor in the parking garage adjacent to Quaker Street

o Market Street near Dart Avenue turning north towards the Ohio Canal.

Contractor could require lane closures at manhole or structure openings to access the sewers and perform the repairs. This could include installing cast-in-place lining systems, or spot repairs.

3.10 Sediment Control and Management

Sediment removal and disposal would occur at the WPCS and the future EHRT site. Therefore, consolidation sewers and tunnel design considered sediment transportation through the system.

Consolidation sewers allow sediment laden flow to pass through structures and pipes and continue to the OCI Tunnel. Consolidation sewer pipes have been designed with adequate slope to convey dry weather flows with enough velocity to keep sediment in suspension. Racks 16 and 17 consolidation sewer tunnel can convey the average dry weather flow of 3.6 MGD at a velocity of 3.1 ft/s. Similarly, Rack 19 consolidation sewer can convey the average dry weather flow of 1.8 MGD at a velocity of 2.4 ft/s.

If sediment deposits occur within the system, storm flows would likely re-suspend the sediment and carry it downstream to the OCI Tunnel and to the OCIT-1 Diversion Structure. Suspended sediment would be discharged to the LCI.

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3.10.1 Diversion Structures Sediment Control

Diversion structures have been designed to minimize sediment accumulation during low flow conditions. Structures have been designed to channel flow to the discharge location and keep sediment in suspension. Dry weather flow would be contained within the channelized area and allow sediment to be removed. Structure sediment accumulation can be reduced if they receive regular cleaning and maintenance and can function as designed.

3.10.2 Tunnel Sediment Control

Consideration was given to sediment transport within the tunnel during dry weather flow conditions and during tunnel dewatering. In each case, the flow velocity is high enough to convey suspended sediment to the discharge location.

The tunnel is designed with a 0.15% slope, which is able to convey sediment. Sediment is expected to remain in suspension when flow velocities are above 2 ft/s. During dry weather flow conditions, Racks 16 and 17 contribute 3.6 MGD of flow. Flow velocity within the tunnel is 2.0 ft/s under this extreme low flow condition. Likewise, a peak dry weather flow of 4.6 MGD produces an approximate flow velocity of 2.2 ft/s. Racks 18 and 19 contribute an additional 14.8 MGD of flow, thus increasing the velocity to 2.8 ft/s within the downstream tunnel segment.

Sediment deposits may occur within the storage tunnel during the filling and storage process but should be flushed out during the draining process. The downstream diversion structure regulates tunnel flow. Depending on WPCS capacity, the tunnel could be discharged at a rate as low as 55 MGD and result in velocities above 4 ft/s. This velocity should be large enough to re-suspend sediment and transport them to the WPCS.

3.11 Risk Analysis

A risk register for the OCI Tunnel was compiled with risks from similar tunnel projects and input from the City of Akron. The register displays risks, risk type, and risk lifecycles, as shown in PER Appendix Z.

The Program Management Team has developed and implemented a Risk Management Program Procedure Manual (PPM) that outlines the risk development and management process and defines Program guidelines in regards to risks. Refer to this Risk Management PPM on the SharePoint site for Program Risk guidelines.

Once the Preliminary Engineering Report is issued, a workshop should be conducted to evaluate each risk. Once the risks are evaluated, the Risk Management Committee would meet and determine which risks require a risk mitigation plan.

3.12 EHRT Future Integration

The LTCP Update requires an ActifloTM ballasted flocculation unit or an approved equivalent technology and disinfection to treat overflow from the OCI Tunnel. The required minimum sustained design capacity is 300 MGD. The achievement of full operation date provided in the LTCP Update is October 31, 2027, approximately nine

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years after the scheduled completion of the OCI Tunnel. For purposes of this PER, the use of ActifloTM is assumed. This EHRT system is a proprietary technology developed and patented by Kruger, a subsidiary of Veolia Water Solutions & Technologies.

The ActifloTM system is proposed to be operated by gravity influent and gravity effluent. Flow is proposed to be diverted from the OCIT-1 Diversion Structure to the system. The treated effluent would discharge by gravity to the Little Cuyahoga River. The tanks and residual solids generated by the EHRT would discharge by gravity to the existing LCI.

Space accommodations are provided at the Hickory Street Site to allow for future construction and integration of an ActifloTM system. The future locating requirements are based on a capacity of 340 MGD to be conservative. Major ActifloTM system components consist of the following:

Screens (both trash racks and fine screens)

Chemical injection and mixing

Maturation tank

Clarification

Hydrocyclones (for micro-sand/sludge separation)

Disinfection

The OCI Tunnel preliminary design of the disinfection system is based on using sodium hypochlorite as disinfectant with a maximum required contact time of 5 minutes. Contact basin size is directly proportional to contact time and disinfectant chemical dose; therefore, the amount of land needed for its construction is directly affected. Although 5-minute contact time is less than 10 States Standard for wastewater treatment, it is consistent with the high-rate disinfection concept widely employed in CSO applications where conventional, longer contact times are not practical. High-rate disinfection involves high-energy disinfectant chemical injection and typically higher chemical doses to achieve the required pathogen reduction using a shorter contact time.

If this high-rate disinfection concept cannot be used, either due to a change in regulations or other monetary or non-monetary factors, a larger footprint might be necessary to achieve the requirements provided in the LTCP Update. Since the OCI Tunnel is being built first, the City would have to buy more land west of the current site or consider using an alternate technology, such as ultraviolet light disinfection.

An access road would be required to allow system operators to gain access to both the OCI Tunnel Diversion Structure and future EHRT facility. The EHRT would likely require chemical deliveries as well as maintenance vehicle access.

The Hickory Street Site has been designed to allow for two alternate permanent access options – a bridge across Little Cuyahoga River from Otto Street and/or an access road from Hickory Street. Both of these access options are also under consideration for permanent access to the OCIT-1 Diversion Structure. Access to the future EHRT should

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be considered by the Final Designer as part of selection of permanent access in the OCI Tunnel contract.

The future construction of the EHRT system would require a discharge pipe to convey treated CSO flow to the Little Cuyahoga River. This discharge pipe is anticipated to cross over the existing LCI. However, the Ohio & Erie Canal Towpath Trail may need to be raised in this area to accommodate the discharge pipe vertical alignment.

Residual solids generated by the EHRT treatment system would be discharged to the LCI as dilute slurry. A holding tank for these residual solids may be required in the event the existing LCI does not have available capacity to receive the flow when the EHRT is in use.

3.13 Operations Considerations

The OCI Tunnel is one of many CSO control measures proposed for the City of Akron CSO service area. The controls provided for the OCI Tunnel would become part of a system-wide control strategy. In addition, the operational control of the OCI Tunnel directly impacts flow rates in the main interceptor, flow rates to the Cuyahoga Street Storage Facility (CSSF), and influent flow rates to the WPCS. The OCI Tunnel is the largest proposed CSO storage facility in the City’s combined sewer system. The combination of the OCI Tunnel and EHRT system assist in managing flows across the City’s collection system. In general, the tunnel outlet control was designed to be used to manage downstream flows as well to reduce the local CSO volume as one component of a system-wide control strategy.

3.13.1 Operation Control Strategy

The following tunnel outlet and overflow control structure operation considerations were assumed as part of the planning process:

The tunnel overflows no more than 7 times to the EHRT within the adjusted typical year.

The elevation of the gravity overflow to the EHRT facility was projected to be slightly lower than the upstream tunnel crown to allow the last portion of storage in the tunnel to be used as equalization to minimize peak EHRT flow in the 7 largest events.

To eliminate the need for additional controls at the CSSF location, the OCI Tunnel outlet control was assumed to be controlled by flows immediately upstream of the CSSF in the main interceptor. Outlet control is necessary to reduce the predicted number of overflows at the CSSF to 0 in the typical year.

Real-time inlet control is not proposed on diversion structures or consolidation sewers for the individual racks

The OCI Tunnel discharge would have a direct impact on the number of times in a typical year WPCS flows exceed secondary capacity and the overflow frequency at the CSSF. Therefore, real-time outlet control is proposed to limit overflow frequency at the CSSF to zero in the typical year and to meet secondary bypass activation limitations provided in the LTCP Update.

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Based on the above assumptions, the following preliminary operation control was developed for adjusted typical year modeling simulation purposes:

A maximum outlet discharge rate is assumed as 95 MGD.

When the flow rate upstream of the CSSF was less than 200 MGD, the outlet control allowed 50 MGD to discharge to the LCI.

When the flow rate upstream of the CSSF was greater than 200 MGD, the outlet control was restricted to 25 MGD, approximately the dry weather flow rate.

Note the only control point for the logic was flow rate upstream of the CSSF, although incorporating operation points at the WPCS as well as other locations in the post LTCP system (Northside Interceptor Tunnel, storage basins, etc…) could also be used to develop a more sophisticated operation control strategy to maximize treated flows and minimize the use of the EHRT and subsequent treated overflow volume. Coordination with other CSO control measures may help to influence the operation of the tunnel outlet, either raising or lowering the outlet flow rate to take advantage of reserve capacity in the remainder of the system.

3.13.2 Emergency Conditions / Failure Modes

During an event, a few potential failure modes should be addressed in final design:

Outlet control valve fails in the closed position - in the currently planned case, the tunnel would fill and overflow to either the Little Cuyahoga River by gravity or into the EHRT if it is online. Potential backup options for flow to be redirected to the interceptor could be examined to address this issue.

Outlet control valve fails in the open position – the planned maximum outlet discharge is able to be handled by the downstream sewer; however, if the maximum planned discharge continues during period of extreme wet weather, it is likely to cause an overflow at the CSSF. If the gate were to fail in the fully open position (uncontrolled outlet), then the flows could overwhelm the downstream interceptor and cause an overflow to occur. Analysis to check if the gate were to be fully open, the downstream flow could be successfully routed to another overflow location should be investigated. In addition, the isolation sluice gate on the OCIT-1 Diversion Structure could be automated for backup control in the event of a failure to the main control valve.

LTCP System Wide Control Strategy

As noted previously, the OCI Tunnel influences the performance of the CSSF and the WPCS. In addition, the OCI Tunnel is one of many CSO control measures proposed for the City of Akron CSO service area. The controls developed for the OCI Tunnel would be part of an overall LTCP system wide control strategy.

Supervisory Control and Data Acquisition (SCADA) Integration

The OCI Tunnel project should provide the instrumentation and controls necessary to integrate the tunnel control strategy into the City’s SCADA system. Regarding SCADA

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data collection, the OCI Tunnel outlet flow rate, tunnel flow depth, interceptor capacity, overflow frequency, and overflow volume are recommended to monitor within the SCADA system, at a minimum for hydraulic operation of the proposed system. Additional parameters may be identified to be integrated into a comprehensive control strategy for the entire collection system.

3.14 Shaft Site Best Management Stormwater Practice Considerations

This section addresses site restoration and stormwater management considerations at the three shaft site locations. Surface disturbance, incorporation of access drives, and shaft access at each site would likely increase impervious area after construction. When addressing site restoration and stormwater management at each of these sites, the goal should be to control increased stormwater runoff on the site and/or minimize additional runoff from entering the combined sewer system.

In general, Best Management Practices (BMPs) for consideration at each of the sites might include but not be limited to, bio-infiltration, porous pavements, and stormwater retention systems.

OCIT – 1

The Final Designer should assess runoff impacts from the Hickory Street Site. For completion of the stormwater design on this site the Final Designer should consider the following items:

Location of the Tow Path Trail

Utilize existing site grade, the site slopes from the tracks to the Little Cuyahoga River

Connect storm water outfall to the proposed tunnel outfall to minimize discharges to the river

Design of a water quality feature should be considered since roadways and maintenance access would be provided. It would be necessary to remove pollutants from the runoff prior to entering the river

Future integration of the EHRT facility should be considered so that water quality features are not destroyed by future construction.

OCIT-2

At the OCIT-2 shaft site, there would be construction on both sides of State Route 59. Consideration should be given for restoration at each location. For completion of the stormwater design on these sites the Final Designer should consider the following item:

These sites are located in the ODOT limited access; coordination with ODOT would be required

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OCIT-3

The construction of the OCIT-3 Drop Shaft would occur in the Akron’s Children’s Hospital parking lot. There is the opportunity on this site to coordinate restoration with Akron Children’s Hospital Master Plan. Upon completion of the tunnel, the site would require general access to the drop shaft for periodic inspections. The contractor staging areas can be converted to green space for run off control for a portion of the parking lot. In coordination with the City’s access requirements, there is opportunity to establish a park like setting at this location for use by ACH employees and even the public. The designer shall coordinate with the ACH Master Planning team and seek to optimize the potential control of runoff and development of green space for use by ACH and/or the public.

3.15 Green Infrastructure Opportunities

Portions of the watersheds for Racks 17, 18, and 19 were identified which may be candidates for green infrastructure. The purpose of green infrastructure is to divert stormwater into a retention and / or infiltration structure and reduce total inflows to the racks during an event. Five project areas were initially evaluated for potential the potential to use green infrastructure. Flow monitors were installed for three of the project areas (four flow meters) to quantify the amount of stormwater entering the sewer system in these areas. The flow meter data for these meters is provided in PER Appendix J. Table 3-6 below shows the tributary area in acres and percent pervious / impervious for the five project areas.

Table 3-6 Green Infrastructure Project Areas

Project Area No.

Tributary Area (acres)

Impervious %

Pervious %

Rack Located

Downstream Flow Meter

I.D.

1 22 55 45 Rack 18 285963 1 64 61 39 Rack 18 285957 2 40 66.4 33.6 Rack 17 731466 3 29 51 49 Rack 18 294211 4 38 58 42 Rack 19 NA 5 34 62 38 Rack 17 NA

The hydraulic model was calibrated with flow meter data at these entry points and run to evaluate the storm flow impact on the OCI Tunnel project. The model was run for the typical year storm event and the maximum volume of combined sewage discharged to the OCI Tunnel decreases by 40 MGD, or approximately 10%. Stormwater bio-retention basins were the selected type of green infrastructure because of their ability to treat relatively large drainage areas and the general lack of space within the project areas to construct more decentralized green infrastructure. Bio-retention basins were preliminarily sized for the expected storm volumes and discharge pipes were routed to the nearest body of water. A memorandum discussing the green infrastructure evaluation and bio-retention sizing is provided in PER Appendix DD.

A draft memorandum of the Green Infrastructure Evaluation was presented to the City for review and comment. After evaluating the memorandum, the City feels that there is

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not a large enough benefit from removing the storm water in the areas identified to warrant the additional cost. Also, many areas that were identified as potential project sites are currently identified as future development sites for the City. Therefore, it is recommended that these green infrastructure projects not be evaluated further in final design.

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4 PROJECT COSTS

The following sections discuss preliminary cost estimating steps taken for the OCI Tunnel Project.

4.1 Opinion of Probable Construction Costs

A preliminary opinion of probable construction cost (OPCC) was developed for the OCI Tunnel Project. To support the possibility of issuing the OCI Tunnel Project as four (4) separate bid packages, the OPCC was divided as follows:

one OPCC for construction of the main OCI Tunnel, the OCIT-1 Diversion Structure, OCIT-2 Drop Shaft, OCIT-3 Drop Shaft, and adits connecting directly to the OCI Tunnel (“OCI Tunnel Contract”);

one OPCC for construction of the Rack 20-23 Consolidation Sewer, the Rack 24 Consolidation Sewer, the Hickory Street Junction Chamber, the connection to OCIT-1 Diversion Structure, pipe rehabilitation throughout the OCI Tunnel Project, and modifications to Racks 4, 20, 23, 24, and 37 (“OCIT-1CS Contract”);

one OPCC for construction of the Rack 18 and Rack 19 consolidation sewers, Rack 18 and Rack 19 diversion structures, Rack 19 Drop Shaft, and modifications to Racks 18 and 19 (“OCIT-2CS Contract”); and

one OPCC for construction of the Rack 16-17 Consolidation Sewer, the Rack 16-17 Junction Chamber and diversion structure, the Rack 16-17 Drop Shaft, and modifications to Racks 16 and 17 (“OCIT-3CS Contract”).

The detailed OPCC’s, provided in PER Appendix AA, were developed based on the preliminary design plans provided in PER Appendix A. The cost evaluation generally meets the guidelines of the Association for the Advancement of Cost Engineering (AACE) Class 3/4 estimating methods and the City of Akron CSO Program Procedural Manual. Sage Timberline® construction estimating software was used to generate the OPCC. Costs were adjusted for regional factors.

4.2 Total Project Cost

The overall cost of the project consists of the PER Opinion of Probable Construction Cost, costs for engineering during construction, construction management and administration, design engineering, right-of-way acquisition, and preconstruction utility relocations. Odor control design and instrumentation and control design costs are included as a separate item and are considered overall project costs.

Engineering during construction was based on the total mid-point of construction cost. The percentages applied vary due to the overall cost of the individual contract. Construction Management and administration was based on the total mid-point of construction and varies based on the contract dollar amount. The overall construction cost was calculated using the mid-point of construction, engineering during construction and the construction management and administration.

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Other costs associated with the project include design engineering, right-of-way acquisition, utility relocation, preliminary engineering, I&C design, and odor control design. Design engineering is assumed to vary based on the contract price. Preliminary engineering cost is based on the previous project loan amount. Both the right-of-way and utility relocation costs are assumed to be lump sums at this time.

The overall total project costs are broken down into the individual divisions as illustrated in the Preliminary Design Drawings and the Draft OPCC. The engineering during construction and design engineering percentages are based on the total cost of the individual project and complies with the CSO Program Procedure Cost Estimating Manual table 2-2. The construction management and administration cost is assumed to be allocated to one construction management team thus the percentages are the same for each contract. Right-of-Way, Utility costs, odor control design, and instrumentation and controls are applied at the program level. Additional demolition costs are not assumed to carry any engineering during construction cost nor design engineering costs. Table 4-1 outlines the overall total project cost.

Table 4-1 Total OCI Tunnel Project Cost

Name

Project Cost Estimate

Construction Mid-Point of Construction

$ (MPoC)5

Engineering During Construction (EDC)3

Const Management & Administration

(CM&A) Total

Construction Stage

Estimate Est Basis Cont.

Rate1 Projection Total (MPoC) 2-8 % of Const2 EDC

CM=2-15% of Const2

CM&A

OCITunnel 104,045,481 30% 4yr @ 3% 189,055,390 2% 3,781,108 8% 15,124,431 207,960,929

OCIT-1CS 4,454,969 35% 4yr @ 3% 8,043,645 8% 643,492 8% 643,492 9,330,628

OCIT-2CS 5,183,074 30% 4yr @ 3% 9,404,763 8% 752,381 8% 752,381 10,909,525

OCIT-3CS 18,695,897 35% 4yr @ 3% 34,983,181 5% 1,749,159 8% 2,798,654 39,530,995

Demolition 323,000 NA 4yr @ 3% 482,415 0% 0 8% 38,593 521,008

Subtotal 132,702,421 varies 4yr @ 3% 241,969,394 varies 6,926,139 8% 19,357,552 268,253,085

Name

Design Engineering3,4

Subtotal Total

Construction Stage

Estimate

ProjectCost 6-13% of

Const2 DesEng Prelim

DesEng(credit)

OCITunnel 6% 11,343,323 (2,000,000) 9,343,323 207,960,929 217,304,252

OCIT-1CS 13% 1,045,674 NA 1,045,674 9,330,628 10,376,302

OCIT-2CS 13% 1,222,619 NA 1,222,619 10,909,525 12,132,144

OCIT-3CS 8% 2,798,654 NA 2,798,654 39,530,995 42,329,649

Demolition 0% 0 NA 0 521,008 521,008

Subtotal varies 16,410,271 (2,000,000) 14,410,271 268,253,085 282,663,356

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OCIT Project Related Costs7

Project Cost Total 282,663,356

Preliminary Engineering 6,032,632

Right-Of-Way 5,000,000

Utility Relocation6 500,000

Odor Control Design 1,000,000

I&C Design 80,000

TOTAL 295,275,988

Notes: (1) Per Table 2-4 in Program Cost Estimating Manual (rev. 6-25-2012) (2) Per Table 2-2 in Program Cost Estimating Manual (rev. 6-25-2012) (3) Based upon Mid-Point of Construction (4) Percentage of Design and CM Cost based upon Table 2-2 in the Program Cost Manual tempered with project characteristics such as uncertainty in project concept, size of contract, complexity of project, preliminary design being a separate effort and type of project. (5) Assuming 3% per year increase in construction costs (6) Utility relocations required prior to construction. Utility relocations required by the contractor are included in the OPCC. (7) Project umbrella costs for OCIT project.

4.3 Probable Construction Schedule

The OCI Tunnel project probable construction schedule is provided as Figure 4-1. The schedule has been prepared assuming the OCI Tunnel project is four (4) separate construction contracts. Where it appears feasible, the schedule allows multiple contractors to be working at the same time.

Activity Name RemainingDuration

Start Finish

Preliminary Engineering Report 814 03-Sep-14 16-Oct-17

Ohio Canal Interceptor Tunnel 814 03-Sep-14 16-Oct-17

OCI Tunnel Project (Main Tunnel) 683 03-Sep-14 16-Apr-17Notice To Proceed 0 03-Sep-14General Submittals 123 03-Sep-14 03-Jan-15Utility Relocations 62 04-Jan-15 06-Mar-15Mobilization and Site Preparation (Includes Launching Trench & Ground Improvement) 93 07-Mar-15 07-Jun-15Construction of OCIT-2 Drop Shaft TERS 32 08-Jun-15 09-Jul-15Construction of OCIT-3 Drop Shaft TERS 62 08-Jun-15 08-Aug-15Fabrication / Delivery of TBM and Segment Molds / TBM Assembly 458 03-Nov-14 03-Feb-16TBM Plant Assembly 28 07-Jan-16 03-Feb-16Main Tunnel Construction 189 04-Feb-16 10-Aug-16TBM Plant Disassembly 14 11-Aug-16 24-Aug-16TBM Disassembly 28 11-Aug-16 07-Sep-16Construction of OCIT-2 Drop Shaft Lining/Baffles 93 11-Aug-16 11-Nov-16Construction of OCIT-1 Diversion Structure and Outfall(s) 93 11-Aug-16 11-Nov-16Construction of OCIT-3 Drop Shaft Lining/Baffles 154 11-Aug-16 11-Jan-17Demobilization 32 12-Jan-17 12-Feb-17Delay for Coordination with Other Contracts 63 13-Feb-17 16-Apr-17

OCIT-1 Consolidation Sewer Project (Racks 20/23/24) 339 12-Nov-16 16-Oct-17Notice to Proceed 0 12-Nov-16General Submittals 62 12-Nov-16 12-Jan-17Utility Relocations 32 12-Dec-16 12-Jan-17Mobilization and Site Preparation 31 12-Jan-17 11-Feb-17R20-23 Consolidation Sewer 32 12-Feb-17 15-Mar-17Hickory Street Junction Chamber 32 16-Mar-17 16-Apr-17R24 Consolidation Sewer 31 17-Apr-17 17-May-17Connector to OCIT-1 Diversion Structure 60 18-May-17 16-Jul-17Demobilization 32 17-Jul-17 17-Aug-17Delay for Coordination with Other Contracts 60 18-Aug-17 16-Oct-17

OCIT-2 Consolidation Sewer Project (Racks 18/19) 844 03-Sep-14 24-Dec-16Notice to Proceed 0 03-Sep-14General Submittals 92 03-Sep-14 03-Dec-14Mobilization and Site Preparation 62 03-Nov-14 03-Jan-15Utility Relocations 63 03-Dec-14 03-Feb-15R18 Diversion Structure 62 04-Jan-15 06-Mar-15Sewer Rehab Work 123 04-Dec-14 05-Apr-15Rack 4 Modification 93 04-Jan-15 06-Apr-15Connect to Sewers on West Side of SR59 93 04-Jan-15 06-Apr-15R18 Consolidation Sewer 32 07-Mar-15 07-Apr-15Rack 37 Modification 62 07-Apr-15 07-Jun-15Connect to Sewers on East Side of SR59 32 08-Jun-15 09-Jul-15R19 Diversion Structure 29 10-Jul-15 07-Aug-15R19 Drop Shaft 123 08-Aug-15 08-Dec-15R19 Consolidation Sewer, Tunnel Construction (to OCIT-2 Drop Shaft) 75 09-Dec-15 21-Feb-16Demobilization 123 22-Feb-16 23-Jun-16Delay for Coordination with Other Contracts 184 24-Jun-16 24-Dec-16

OCIT-3 Consolidation Sewer Project (Racks 16/17) 578 03-Sep-14 18-Nov-16Notice to Proceed 0 03-Sep-14General Submittals 66 03-Sep-14 07-Nov-14Mobilization and Site Preparation 32 03-Dec-14 03-Jan-15Utility Relocations 32 03-Jan-15 03-Feb-15R16-17 Diversion Structure 93 03-Jan-15 05-Apr-15R16-17 Drop Shaft 31 06-Apr-15 06-May-15Fabrication / Delivery of TBM and Segment Molds 274 03-Nov-14 03-Aug-15TBM Plant Assembly 28 07-Jul-15 03-Aug-15Construct Tail Tunnel/Launch Face at OCIT-3 Drop Shaft 92 09-Aug-15 08-Nov-15R16-17 Consolidation Sewer, Tunnel Construction 40 09-Nov-15 18-Dec-15TBM Plant Disassembly 14 19-Dec-15 01-Jan-16TBM Disassembly 28 19-Dec-15 15-Jan-16R16-17 Drop Shaft Completion 91 19-Dec-15 18-Mar-16Demobilization 60 19-Mar-16 17-May-16Delay for Coordination with Other Contracts 185 18-May-16 18-Nov-16

Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct3, 2014 Qtr 4, 2014 Qtr 1, 2015 Qtr 2, 2015 Qtr 3, 2015 Qtr 4, 2015 Qtr 1, 2016 Qtr 2, 2016 Qtr 3, 2016 Qtr 4, 2016 Qtr 1, 2017 Qtr 2, 2017 Qtr 3, 2017 , 2017

1

1

16-Apr-17, OCI Tunnel Project (Main TunnNotice To Proceed

1Notice to Proceed

24-Dec-16, OCIT-2 Consolidation Sewer Project (Racks 18/19)Notice to Proceed

18-Nov-16, OCIT-3 Consolidation Sewer Project (Racks 16/17)Notice to Proceed

Remaining WorkCritical Remaining Work

MilestoneSummary

Ohio Canal Interceptor TunnelProbable Construction Schedule / Page 1 of 1 / REV 10 25 12

Figure 4-1

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The preliminary areas of potential conflict between possible multiple construction contracts appear to be at the OCIT-1 Diversion Structure and the OCIT-2 Drop Shaft. Specifically, the OCIT-1 Consolidation Sewer contractor cannot make final tie-ins and flow switchovers until the OCIT-1 Diversion Structure is completed, which in turn is dependent upon completion of the OCI Tunnel mining. Also, OCIT-2 Drop Shaft cannot be completed until after the Rack 19 Consolidation Sewer tunnel is mined into the shaft.

The OCI Tunnel project schedule as a whole was based on two LTCP Update milestones as follows:

Bidding of the control measure by April 30, 2014.

Achievement of full operation by December 31, 2018.

The OCI Tunnel construction contract schedule is based on the following assumptions:

Notice to Proceed (NTP) received by September 3, 2014.

The tunnel boring machine submittal would be approved in the first two (2) months and the TBM can be fabricated, delivered, and assembled on site 15 months after submittal approval.

The average daily advance rate for the entire tunnel would be around 45 ft/day (~16.6 m/day). The estimated completion time is 400 shifts or about 27 weeks after the machine’s full assembly and start of the boring. This assumes 24-hours of mining per day, 5 day work week, and a maintenance shift on the weekend.

The USACE would allow construction of the new OCI Tunnel outfall structure in the Little Cuyahoga River between August and November, 2016.

Construction of the shaft final linings occurs after the TBM mining is completed.

The OCI Tunnel contractor’s schedule would include up to 3 months of float to account for coordination of activities at sites shared with other OCI Tunnel contracts.

The OCIT-1CS Contract (Racks 20/23/24) schedule is based on the following assumptions:

Construction of the OCIT-1 Diversion Structure and outfall(s) is complete before the OCIT-1CS contract receives NTP.

The OCIT-1CS contractor’s schedule would include up to 3 months of float to account for coordination of activities at sites shared with or structures built by other OCI Tunnel project contractors.

The OCIT-2CS Contract (Racks 18 and 19 structures) schedule is based on the following assumptions:

NTP received by September 3, 2014.

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The OCIT-2CS contractor can construct the Rack 18 Diversion Structure and consolidation sewers without interference from the OCI Tunnel contractor’s activities.

The OCIT-2CS contractor would tunnel the Rack 19 Consolidation Sewer starting from the Rack 19 Drop Shaft and proceeding from east to west.

The OCIT-2CS Drop Shaft is partially built and ready to receive the Rack 19 Consolidation Sewer TBM within 16 months of NTP.

The OCIT-2CS contractor’s schedule would include up to 6 months of float to account for coordination of activities at sites shared with or structures built by other OCI Tunnel contractors.

The OCIT-3CS Contract (Racks 16 and 17 structures) schedule is based on the following assumptions:

NTP received by September 3, 2014.

The tunnel boring machine submittal would be approved in the first two (2) months and the TBM can be fabricated, delivered, and assembled on site 9 months after submittal approval.

The OCIT-3 Drop Shaft TERS could be partially constructed and utilized as a TBM launching shaft and mining shaft. Later, the OCI Tunnel contractor would finish the shaft and construct the baffle structure.

The contractor would have unrestricted access to the south parking lot of the Canal Stadium between January and March 2015 for construction of the diversion structure, junction chamber, and TBM retrieval shaft.

The TBM retrieval shaft can be left open during summer and fall of 2015 until the Rack 16-17 Consolidation Sewer is mined.

The USACE would allow construction of the new Rack 16-17 Diversion Structure in the Ohio Canal between January and May, 2015.

The OCI Tunnel contractor’s schedule would include up to 6 months of float to account for coordination of activities at sites shared with other OCI Tunnel contracts.

4.4 Construction and Design Contract Coordination

The current plan for the OCI Tunnel project is to engage up to four (4) design consultants to prepare bid documents, and to bid up to four (4) construction contracts. Likely delineation between both the design and construction contracts is where the consolidation sewers penetrate the drop shafts connected to the OCI Tunnel. If this is the case, several of the large drop shaft sites would have proposed structures designed by different consultants, and built by different contractors. The following is a partial list of potential conflicts to be addressed during Final Design. Additional potential design and

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construction conflicts are very likely to be identified as Final Design proceeds, and should be brought to the City’s attention quickly.

Rack 37 Modifications: Except for the existing rack underflow abandonment and final closure of the weir wall in the new diversion structure, Rack 37 modifications can be completed before the OCI Tunnel is online because the dry weather flows stay in the OCI and the wet weather flows can still reach the overflow point on the Ohio Canal Enclosure. OCIT-1CS designer should provide for a temporary opening in the diversion structure weir wall and note the Rack 37 rack abandonment should not be performed until the OCI Tunnel is online. OCIT-1CS contractor could either delay this work until the OCI Tunnel is online, or the final work could be done by the OCI Tunnel contractor.

Rack 4 Modifications: Provided that a temporary orifice is placed on the new Rack 4 Diversion Structure, Rack 4 modification scope can be constructed before activation of the OCI Tunnel. Restriction is necessary because the OCI is unable to receive and convey typical year flows from Rack 4 until the Rack 16-17 flows are diverted out of the OCI.

OCIT-1CS Connection to OCIT-1 Diversion Structure: OCIT-1CS designer should coordinate with the OCI Tunnel designer to develop a connection detail of the 120-inch consolidation sewer to the OCIT-1 diversion structure. In addition, Racks 20, 23, and 24 would need to remain active until the OCIT overflow conduit is completed.

OCIT-2 Drop Shaft and OCIT-2CS Structures: OCIT-2 Drop Shaft and OCI Tunnel would likely be designed by the same designer and built by the same contractor. The OCIT-2CS designer should coordinate with the OCI Tunnel designer to accommodate construction of the new 72-inch I.D. sewer crossing beneath S.R. 59, assuming mining begins at the OCIT-2 Drop Shaft. Timing of the OCI Tunnel and OCIT-2 Drop Shaft should also be considered during design and construction to ensure the tunnel and shaft do not conflict.

OCIT-3 Drop Shaft and OCIT-3CS Tunnel: OCIT-3CS tunnel designer should coordinate with the OCI Tunnel designer to make sure the OCIT-3CS sewer contractor has sufficient work area for mining and installation of the 12-foot I.D. consolidation sewer. The OCIT-3CS tunnel contractor would need a launching pit and mucking area for the duration of mining.

Hydraulic Modeling: Current plans are for the OCI Tunnel designer to begin work immediately, and the OCIT-1CS, 2CS, and 3CS designers to begin later in 2013. OCI Tunnel designer would be performing surge analyses and designing the downstream diversion chamber and overflow conduit based on the most current hydraulics data provided by the Program Management Team. As the consolidation sewer designers begin work, they would need to be informed of the hydraulic conditions utilized for OCI Tunnel design, and told their design should produce the same condition so as to not change the OCI Tunnel design. As a result of this design sequence, some of the consolidation sewer designs could be somewhat inefficient.

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4.5 20 Year Operations and Maintenance Costs

A present worth operations and maintenance (O&M) cost estimate has been developed for maintenance of proposed facilities on the OCI Tunnel project. A planning duration of 20 years was considered. The primary items considered in this estimate are as follows:

Inspection of OCI Tunnel,

Inspection of tunnel drop structures,

Inspection of near-surface sewers and structures, and

Inspection, operation, and maintenance of mechanical equipment.

Cost estimates for each O&M item were based on assumed frequencies of recurrence and are reported in 2012 dollars. Table 4-2 summarizes the present worth 20-year operation & maintenance cost estimate, frequency, and cost per cycle assumptions. Additional calculation details and assumptions are provided in PER Appendix BB.

Table 4-2 20-year Operations and Maintenance Present Worth Cost

Item FrequencyCost/Cyclewith 30%

Contingency

Present WorthTotal for 20

Years with 30%Contingency

OCI TUNNEL 5 year cycle $91,000 $241.241OCI Tunnel inspection $91,000 $241.241

STRUCTURAL INSPECTION 5 year cycle $259,923 $689,057Structures 5 year cycle $32,240 $85,468Tunnel Drop Structures 5 year cycle $11,960 $31,706Near Surface Structures 5 year cycle $20,280 $53,762

Sewer Pipe Inspection 5 year cycle $227,683 $603,588Sewer Pipe 18" DIA 5 year cycle $930 $2,464Sewer Pipe 30" DIA 5 year cycle $6,406 $16,983Sewer Pipe 36" DIA 5 year cycle $5,265 $13,958Sewer Pipe 42" DIA 5 year cycle $31,873 $84,496Sewer Pipe Between 48" and 66"DIA 5 year cycle $11,170 $29,611

Sewer Pipe Between 72" and 96"DIA 5 year cycle $27,369 $72,555

Sewer Pipe Greater than 96" DIA 5 year cycle $144,671 $383,521

EQUIPMENT MAINTENANCE 3 month cycle $234,536Control Valve in OCI Tunnel Contract 3 month cycle $3,606 $204,978Maintenance Labor 3 month cycle $2,340 $133,006

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Item FrequencyCost/Cyclewith 30%

Contingency

Present WorthTotal for 20

Years with 30%Contingency

Maintenance Equipment 3 month cycle $195 $11,084Maintenance Material 3 month cycle $130 $7,390

Hydraulic Power Electrical5 days during wet

weather $30 $1,700

HVAC Electrical3 month cycle 24 hours a

day $911 $51,799

Sluice Gate in OCI Tunnel Contract yearly $2,080 $29,558Maintenance Labor yearly $1,560 $22,168Maintenance Equipment yearly $130 $1,848Maintenance Material yearly $65 $924Electric Operator yearlyFlow Meter Calibration yearly $325 $4,619

EQUIPMENT REPLACEMENT 20 year cycle $962,000 $483,886Control Valve 20 year cycle $780,000 $392,340Flow Meter 20 year cycle $117,000 $58,851Sluice Gate 20 year cycle $65,000 $32,685

GRAND TOTAL $1,648,720

Structural inspection costs were based on pipe and structure inspections. The inspection cost estimates were based on a 5-year cycle to meet the City’s CMOM requirements.

Structure costs were developed based on a three (3) person crew inspecting each structure. Inspection costs were increased for the four (4) deep drop structures due to utilizing a crane to lower the crew in a man-cage for inspection.

Cost estimates for tributary collection sewer pipe to the OCI Tunnel were developed based on pipe size per linear foot. The OCI Tunnel inspection cost estimate was based on similar tunnel project inspection costs.

Equipment maintenance contains a cost analysis for the control valve and sluice gate at the outlet of the OCI Tunnel. The control valve costs were based on a 3-month maintenance cycle four (4) times a year. The sluice gate is based on a 1-year maintenance cycle. Factors contributing to the cost estimate were labor, equipment, materials, electricity, and calibration.

The average life assumed for equipment was 20 years with no salvage value. The equipment replacement costs for the control valve, flow meter, and sluice gate were estimated. Installation costs were assumed to equal the equipment replacement cost.

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Tunnel, pipe, and structure rehabilitation, such as cured-in-placed pipe lining and concrete patching, are assumed to be beyond the 20-year planning duration of this estimate.

Overall, the total present worth 20-year operation and maintenance cost was estimated at approximately $1,648,720.

4.6 Financing Considerations

The OCI Tunnel project would most likely be funded using low interest rate loans from the State of Ohio Water Pollution Control Loan Fund (WPCLF). The WPCLF is a revolving fund designed to provide low interest rate loans and other forms of assistance for water resource protection and improvement projects. The State of Ohio offers below-market interest rate loans for qualified wastewater treatment works projects (including planning, design, and construction) which would be owned by public entities. The City should submit a nomination form for the OCI Tunnel Project in the Fall of 2012, requesting funding in the 2014 WPCLF program year.

The WPCLF loan cannot be used to fund land and easement acquisition for the OCI Tunnel project. Land Acquisition would be funded separately by the City.

4.7 Disadvantaged and Small Business Opportunities

OCI Tunnel project design and construction projects are most likely to be funded by loans obtained through the USEPA Water Pollution Control Loan Fund (WPCLF). The OEPA is responsible for receiving nominations, selecting projects, and managing the distribution of the loans in the State of Ohio. As a condition of receiving capitalization grants from U.S. EPA, OEPA negotiates “fair share” Disadvantaged Business Enterprises (DBE) objectives with U.S. EPA. “DBE” is an inclusive term including Minority Business Enterprises (MBE), Women Business Enterprises (WBE), Small Business Enterprises (SBE), Small Business in Rural Areas (SBRA), HUBZone Small Business, Labor Surplus Area Firms (LSAF), and other entities defined as socially and/or economically disadvantaged.

While the WPCLF and Water Supply Revolving Loan Account (WSRLA) strongly encourage participation by disadvantaged groups, specific participation goals are negotiated with USEPA only for Minority Business Enterprises and Women’s Business Enterprises. As of March 1, 2011, negotiated goals for construction related activities on WPCLF / WSRLA funded projects were 3.0% of contracts to MBE’s and 3.7% of contracts to WBE’s. The Ohio EPA WPCLF website lists required actions and reports the City and the Prime Contractor must provide to Ohio EPA in order to comply with WPCLF loan DBE program requirements.

Ohio DBE program information, including a current list of DBE firms registered in Ohio, is available at the Ohio DBE Unified Certification Program website (www.ohioucp.com) and the Ohio Department of Transportation DBE site (http://www.dot.state.oh.us/divisions/contractadmin/contracts/pages/dbe.aspx).

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5 RECOMMENDED FUTURE ANALYSES

The preliminary analysis and design was based on preliminary investigations and data. The Final Designer should gather additional detail and complete detailed analyses during contract bid document preparation. The following items should be considered and addressed during final design:

Geotechnical-Related Items

Investigate and define mixed face (soil / rock) tunneling zone limits.

Add “fill-in” borings along the tunnel and sewer alignments as appropriate to meet the Standard of Care for detailed design and construction plans.

Investigate subsurface conditions along the TBM alignment for boulders and cobbles.

Further integrate historical geotechnical data from the St. Vincent St. Mary football field construction project into the geotechnical profile. Additional information would likely be necessary to address OEPA concerns for impacting the dump site (discussed below).

The St. Vincent St. Mary football field and visitor seating stands were built on a former dump site. During a meeting in July, 2012, the Principal and a Board of Representatives indicated that the school has an agreement with OEPA on how to handle excavation and materials in the landfill areas during the stadium construction. In October, 2012 the City obtained a copy of the Rule 13 documents for the football field construction. After an initial contact was made, OEPA indicated that any work within 300 feet of a known landfill is subject to OEPA review and may require permitting. The Final Designer should review the agreement, map the known lateral and vertical limits of the dump site onto contract drawings, and assist the City preparing an engineering analysis showing there would be no impact to the dump site due to mining and permanent presence of the tunnel.

The OCI Tunnel portal trench is currently shown as a steel sheetpile supported excavation. However, the depth to rock varies significant between two close borings (OCI-24 and OCI-38). For the purpose of developing an updated OPCC, additional geotechnical investigations on the OCI Tunnel mining site could confirm feasible excavation support systems for the site.

Based on preliminary data, it appears the majority of the large shafts would require secant pile, slurry wall, or frozen ground-supported TERS. However, based on the excavation depths and sizes, alternate TERS systems may be feasible for the structures in the OCIT-1CS contract. For the purpose of developing an updated OPCC, additional geotechnical investigations should be performed near OCIT-1CS structures to confirm feasible excavation support systems.

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The Ohio Department of Transportation has given concurrence to the preliminary OCI Tunnel alignment through an email to the City on August 6, 2012. However, ODOT would be reviewing design drawings and relevant calculations to “…help insure that work in and around the S.R. 59 limited access right-of-way would have no detrimental effects on S.R. 59 pavement or bridges.” The Final Designer should prepare detailed potential settlement estimates for ODOT bridge footings and pavements and a monitoring program with proposed action levels and associated corrective actions (e.g. re-leveling of bridge deck). If ODOT is not satisfied the risks to their facilities are acceptable, the Final Designer may need to present options for further protecting ODOT structures by actions taken before, during, and / or after tunneling occurs.

Shaft TERS and portal support systems may need to provide protection for surrounding homes, roadways, and other infrastructure. The Final Designer should investigate areas around each TERS and prepare a clear specification to limit the risk of ground loss and / or ground movement related to the shaft construction (including the potential for piping). A geotechnical monitoring program and plan with action levels and corrective action plans should also be prepared in final design.

The OCIT-2 Drop Shaft and possibly Rack 19 Drop Shaft may extend into and be founded on bedrock. Specific investigations of these shales should be performed to determine if they would require pre-grouting to mitigate risk of groundwater inflows and /or hazardous gas conditions during shaft excavation.

Additional rock and soil conditions investigation in the first 500 lineal feet of the OCI Tunnel alignment should be performed to confirm rock surface along the alignment and overburden soil strengths.

Additional geotechnical investigations should be performed to confirm the TBM recommendations and estimated production rates contained in the preliminary engineering report.

Additional geotechnical investigations should be performed to confirm the “potentially gassy” designation recommended in the preliminary design report.

Geotechnical data in the area of the tunnel portal and first few hundred lineal feet of the OCI Tunnel alignment indicate these structures would need to be constructed in very unfavorable soil and groundwater conditions. Although existing infrastructure does not appear to be extremely sensitive, critical, or difficult to repair, there may be a risk of significant delays to the OCI Tunnel project and negative public perception. Final Designer should obtain detailed information about this area and analyze the proposed construction methods in detail to confirm the concepts shown on the preliminary design drawings.

The OCI Tunnel and drop shafts are expected to generate over 150,000 cubic yards of spoils. The Final Designer should research common conditioning agents that may be used on this project and determine how they might affect disposal and beneficial reuse opportunities.

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The OCIT-3 Consolidation Sewer alignment evaluations and preliminary designs were based on very limited geotechnical data. The tunnel alignment would pass within 100 feet of existing structures and public areas, and would have very little cover at the ends of the alignment. In addition, the alignment is almost a continuous curve until reaching Perkins Park. The Final Designer should perform additional test borings and laboratory testing to better characterize the soil and groundwater conditions present in the tunnel profile. The Final Designer should assess the risks of damaging existing facilities along the alignment and make recommendations for mitigating or reducing risks. Use of a pressurized slurry face tunnel boring machine may help to reduce risk. If necessary and feasible given the new soils information, the Final Designer may consider a recommendation to lower the tunnel to increase soil cover.

Hydraulics

IIHR physical modeling and design criteria was used for this evaluation. However baffle drops shown in the preliminary design drawings are larger than other constructed baffle drop shafts built to date. In addition, the 75/25 configuration recommended for this project has not yet been built into a drop structure. The Final Designer should perform both Computational Fluid Dynamics and physical drop shaft modeling to confirm their performance under OCI Tunnel project design flows. Physical modeling should also be used to investigate shaft performance under 100 year or higher storms and to investigate OCIT-1 Diversion Structure performance.

The City of Akron is currently designing a sewer separation project for areas tributary to Rack 21. They anticipate some portion of the flows may not be controlled by Rack 21. The Final Designer should meet with the City designer and determine if the uncontrolled flows can be directed into the Rack 19 Diversion Structure and into the OCI Tunnel system.

Transient flow modeling in the OCI Tunnel could confirm that special considerations for surging and air flow issues are not necessary. If surge relief is necessary, and shafts are utilized for relief, the surge relief design elements should be included in the physical modeling study.

The Rack 19 shaft is currently shown as a baffle drop due to the high design flow rates and the need for air flow down the shaft to decrease the potential for odor issues. However, the drop is relatively shallow and alternate hydraulic structures may be feasible. The Final Designer should investigate alternate drop configurations for Rack 19 shaft. Alternate designs should place a high priority on minimizing potential odor issues due to the proximity of recreational and commercial facilities.

The OCI Tunnel system for Racks 16, 17, 18, and 19 is designed to convey the 10 year storm flow to the endpoint. However, the Final Designer should analyze the system for larger storms in order to confirm fail-safe mechanisms are in place to prevent damage to the system.

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Further dry and wet weather flow velocities evaluation could confirm flushing systems are not necessary. Findings should be incorporated into the final operations and maintenance design.

The preliminary design is based on a conservative assumption that incoming consolidation sewers are conveying maximum capacity flows to drop shafts at the same time. The hydraulic model should be reviewed to determine if there is enough confidence that the timing of peak flows entering the shafts would support designing the drops for a lower peak design flow. Recommendations related to timing of peak flows should be accompanied by a cost-benefit-risk analysis justifying the recommendation.

At the OCIT-3 Drop Shaft location, an existing 45-inch combined sewer extends north to south across the property. Sewer flows in this pipe contribute to the Rack 18 basin, which could be conveyed to the Rack 18 Diversion Structure and to the OCIT-2 Drop Shaft. Depending upon the final drop shaft size and location and construction shafts needed for the Rack 16-17 Consolidation Sewer, this sewer may need to be relocated and flows directed into the OCIT-3 Drop Shaft.

Final Designer should perform a detailed analysis of anticipated flow velocities in the OCI Tunnel overflow conduit to the Little Cuyahoga River. This information would be necessary to determine the need and for detailed design of energy-dissipation devices at the outlet. In addition, Final Designer should consider whether river bank modifications for the outlet structure could be incorporated into a more significant river restoration effort.

Final Designer should evaluate the 64-inch plug valve located in the OCIT-1 area control structure for cavitation potential. Consideration should be given to using two plug valves instead of one 64-inch valve.

The proposed diversion structures for Racks 16-17 and 18-19 could experience flows exceeding 500 to 700 MGD during maximum design storm events. The Final Designer should perform both Computational Fluid Dynamics and physical modeling of these structures to confirm their performance under OCI Tunnel project design flows, and identify possible efficiencies for these structures, both from a hydraulic and structural design perspective.

Final Designer should evaluate the reconfiguration potential of Rack 37 consolidation sewer and diversion structure.

Drop Shafts

The Final Designer should consider the addition of independent drop structures inside or outside the baffle drop shafts, or possible modifications to the baffles to efficiently convey dry weather flows through the shaft.

The Final Designer should consider potential for long term erosion of the baffles and the shaft inverts due to hydraulic flows, grit, and turbulence.

The Final Designer should perform a structural analysis of the large baffle drop slabs early in the design process to confirm they could support the static and

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dynamic loadings and still have acceptable performance with regards to hydraulics and air entrainment.

The OCI Tunnel penetration into the OCIT-3 shaft could be a complex structural design, and it should be prepared early in the final design so the shaft wall can be designed appropriately. Final Designer should prepare early on in the project a philosophy for design of permanent tunnel eyes in shafts.

The physical modeling of the shafts should account for maintenance access.

A preliminary design assumption is the OCI Tunnel TBM can make entry into the OCIT-3 Drop Shaft through a sealed wall penetration. The final design should confirm this assumption and incorporate requirements into the specifications which would prevent ground loss and potential damage to the shaft during TBM entry.

Final Designer may wish to consider construction of two (2) separate baffle or vortex drop structures in a single location for redundancy and lower flow rates. Provide a cost/benefit justification if two shafts are recommended.

If baffle drop structures are confirmed for this project, the following items should be integrated and addressed in detail during final design:

o Odor control,

o Ventilation requirements,

o Hydraulic surge,

o Adit design and adit/tunnel connection design,

o Corrosion potential,

o Dry weather flows, and

o Potential for damage due to large debris

Final Designer should perform a cost benefit analysis of vortex versus baffle drop structures during final design.

Conceptual dry weather flow drop structures shown on Preliminary Design Drawings currently include gratings to protect the drop pipe from large debris, but only one is accessible directly from the surface. The Final Designer should specifically consider O&M impacts associated with this grating for the Rack 19 Drop Shaft 36-inch consolidation sewer.

Shaft Temporary Earth Retention Systems (TERS)

Final Designer should consider the possibility of using project shafts for multiple construction contracts. For example, the OCIT-3 drop shaft could be partially constructed and used by the Rack 16-17 Consolidation Sewer contractor as a

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launching and mucking shaft. The OCI Tunnel contractor could later complete the shaft and utilize it for receiving the OCI Tunnel TBM. This type of coordination could provide savings for the City of Akron.

Final Designer should complete test borings at final shaft locations to confirm the generalized soil and rock conditions discussed above. Once additional geotechnical and hydro geologic data is available, the Final Designer should revisit these recommendations and perhaps perform in situ permeability tests or full-scale pump tests to determine the effectiveness and area of influence zone of a dewatering system. The designer may also consider ground modification in lieu of dewatering. In particular, at OCIT-3, the Final Designer should investigate the apparent clay till layer near Elevation 775 for possible use as a seal for the bottom of the TERS.

Permits / Coordination

In a meeting with the National Park Service (NPS), NPS indicated a National Environmental Policy Act (NEPA) analysis would not be required. The Final Designer should closely coordinate with the CVSR at the start of final design and at 60% design to confirm a NEPA analysis is not needed.

The Final Designer should confirm the OEPA would not require special construction procedures for tunneling beneath the abandoned dump under the St. Vincent St. Mary football field.

A records search and field survey of historical and architecturally significant buildings along the OCI Tunnel alignment was completed as part of preliminary design. The findings have not been sent to the Ohio Historic Preservation Office (OHPO) yet for comment. The Final Designer should incorporate requirements of the OHPO into the final design.

The current access options for the OCI Tunnel mining site include a long embankment-supported ramp on the south side of the site, with access to Hickory Street, or a bridge structure over the Little Cuyahoga River at Otto Street. There are short term and long term reasons for both access points. The Final Designer would need a decision for the City’s preferred long term access requirements in order to develop design parameters for the bridge. The Final Designer must also coordinate with the City in applying for USACE permits.

The City and preliminary designers have initiated studies relating to endangered species on the project site. The Final Designer should incorporate comments from USFWS into the design.

The Final Designer would finalize the OCI Tunnel overflow conduit discharge structure design and determine if a 401 Water Quality Certification is needed.

Initial contact has been made with First Energy with regards to building a temporary bridge across the Little Cuyahoga River for access to the OCI Tunnel mining site. First Energy indicated they would require plans and profiles showing the proposed structure and its foundation systems, as well as minimum clearances from existing overhead power lines. Coordination with First Energy

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should be added to the project design schedule. First Energy requirements and timing of reviews should be accounted for in the Final Design schedule.

Utilities

Final Designer should meet with utility owners soon after the start of work to identify utility relocations and land acquisition needs for utility relocations.

The Final Designers would need to meet with individual utilities with the final design and obtain markups.

Tunneling contractors on the OCI Tunnel project would likely need temporary electrical power in excess of permanent facility needs to operate the TBM and underground equipment. First Energy should be contacted as early in detailed design as possible to assess the timeframe and process for providing power to tunnel mining areas of the project. The Final Designer should include the City in these discussions, as it may be necessary to pay for First Energy design and permitting services during design in order to prevent delays during construction.

During initial discussions to acquire property for the OCIT project, First Energy requested information about the tunnel and its potential impact on local facilities. Final Designer should clarify this request prior to issuing drawings for utility agency review.

Odor Control

The preliminary design was based on the strategy that odor control should be controlled by air flow provisions in the tunnel. Odor control should be further evaluated during final design. The Final Designer should coordinate with the odor control consultant during final design.

Contract Break-Up

Analyze project elements and recommend most efficient means of breaking the OCI Tunnel project into multiple bids to maximize opportunities for local businesses.

Prepare estimate of allowance needed to design and construct temporary power substation for TBM. Coordinate with Ohio Edison and confirm the schedule to design and install temporary power drop would not result in delays to the project.

Determine if shafts may be needed by multiple contractors for tunneling, and coordinate contract conditions and specifications to prevent conflicts.

Community Impacts

The final design should incorporate language into the specifications and contract documents restricting the Contractors from unnecessarily closing or significantly affecting the Towpath Trail. A trail detour plan should be developed as well. The Final Designer should also identify significant events on the trail when the Contractor must make accommodations to open the trail. Of particular concern

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are the Trail segments adjacent to the OCI Tunnel mining site and Canal Park Stadium.

The construction schedule and contract documents should include a requirement to accommodate activities at the Canal Park Stadium. The final design should incorporate language into the specifications and contract documents restricting the Contractors from significantly affecting the operation of the stadium unless the City agrees to the plan.

The addition of Rack 21 flows discussed above could result in significant work in the Market Street right of way. The Final Designer would need to prepare the connection design and identify the likely duration and extent of impacts to traveling public.

O&M

The Final Designer should incorporate provisions into the drop shaft structural designs to clean debris from inside the drop shafts, including debris accumulating on the baffles.

Evaluate the two alternate OCI Tunnel Mining site entrance roads with respect to permanent operations and maintenance of the OCI Tunnel system. Specifically, review proposed road grades for large vehicle access.

The current operation plan does not utilize bar racks or screens upstream of the baffle drop shafts into the tunnel. The Final Designer should evaluate the advantages and disadvantages of adding bar racks. Consider the operational preferences of the City and the potential risk of damage to the baffle structures if large debris were to be conveyed to the shafts.

The Final Designer should analyze of the operational control strategy for OCI Tunnel, with the goal of creating a system for an efficient operation both during and following the completion of the LTCP. This may require coordination with the Program Management Team.

Final design scope should include specific considerations relative to maintenance access into new structures, access for cleaning equipment, connections designed to minimize head-loss, vehicular access to maintenance and inspection points, and minimizing traffic control requirements during maintenance activities.

Final Designer should verify with the City the preference to add facilities to screen overflows after completion of the OCI Tunnel project. Although the Preliminary Design drawings do not account for the facilities, the Final PER OPCC includes a cost allocation.

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Overflow Abandonment

The OCI Tunnel preliminary design could allow for the abandonment of overflow points from Racks 19, 20, and 23. The Final Designer should confirm the City’s preferences before proceeding with abandonment design.

Tunnel Lining System

The preliminary design of the OCI Tunnel lining system is based on a one-pass system which utilizes steel-reinforced concrete segments. The final design should include an analysis of the potential savings and risks for using fiber-reinforced concrete segments.

The final analysis and design of the tunnel lining system should evaluate the risk of fines piping through cracks and liner joints during the tunnel life.

CCTV Inspection Pre and Post Construction

Final Designer should address pre and post construction CCTV inspections for the following areas/sewers:

o Sanitary sewers that cross the OCI Tunnel alignment to document sewer movement

o The 42” combined sewer that cuts across the Akron Children’s Hospital Parking lot adjacent to the OCIT-3 Drop Shaft

o LCI in the vicinity of mining site limits, including the apparent dip in sewer grade at the west end of the mining site.

o The existing sewer between the proposed Rack 37 Diversion Structure and the existing Rack 37 structure

Final Designer should coordinate with the City during final design for other miscellaneous CCTV inspections that may be needed.

Structural

The currently proposed OCI Tunnel overflow conduits would pass vertically less than 10 feet from the existing 87-inch LCI. The Final Designer should assess the condition of the LCI in the area of new construction, assess the risk of the interceptor being damaged during construction, assess the possible impacts of both construction and permanent loads, and incorporate improvements to the LCI as necessary to continue operation of this facility.

Ground Movement

The tunnel reaches between STA 11+00 and STA 25+00 have less than two diameters of tunnel cover and could require pressurized face tunneling. The Final Designer should review these areas for potential heaving or ground loss as a result of tunneling operations, and either design a mitigation plan or incorporate

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requirements into the contract documents for means and methods that would reduce the potential for heave and settlement to acceptable levels.

Corrosion

Consider corrosive effect of undiluted sanitary flows in shafts / tunnel during design and O&M planning.