Addendum No. 6 to Request for Proposals No. SWD001-11 … SWD001-11 - Addendum 6.pdf · Page 1 of...

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December 6, 2010

to Addendum No. 6

Request for Proposals No. SWD001-11

Closure and Post-Closure Plan Preparation for Ordot Dump

This Addendum No. 6 to RFP No. SWD001-11 includes additional documents available for review.

Parties interested in this RFP should monitor the Receiver’s Website at http://www.guamsolidwastereceiver.org/documents-RFP-SWD001-10.html for additional RFP addenda. All addenda issued for RFP No. SWD001-11 will be posted on this Website.

ADDITIONAL DOCUMENTS AVAILABLE FOR REVIEW

The additional documents available include EPA comments to the Ordot Final Closure Plan and Post-Closure Plan prepared in 2005.

• USEPA letter to the Government of Guam - Department of Public Works, dated October 26, 2005 with two enclosures:

o Technical Memorandum by CH2M Hill dated October 4, 2005 o Technical Memorandum No. 7 by CH2M Hill dated October 18, 2005

These documents are attached to this Addendum due to their small size and have been made available to interested parties on the Receiver Website indicated above. These documents were recently made available to the Receiver and update our response to Question No. 3 in Addendum No. 5.

http://www.guamsolidwastereceiver.org/documents-RFP-SWD001-10.html�

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RFP SWD001-11, Addendum No. 6

SFO/C:\DOCUMENTS AND SETTINGS\CLUND\LOCAL SETTINGS\TEMPORARY INTERNET FILES\CONTENT.OUTLOOK\V0G7L7JL\ENCLOSURE 1 GENERAL COMMENTS TECHNICAL MEMO.DOC 1

T E C H N I C A L M E M O R A N D U M

General Comments on the 100% Design Submittals for Ordot Dump

PREPARED FOR: Lance Richman/USEPA/Region 9

PREPARED BY: CH2M HILL

COPIES: Rick Sturm/CH2M HILL/SFO Shannon Wright/CH2M HILL/SAC File/CH2M HILL/SFO

DATE: October 4, 2005

This technical memorandum has been prepared as part of the work effort set forth in the Work Plan for Ordot Landfill Superfund Site Remedial Design Oversight under Contract No. 68-W-98-225/WA No. 185-ROBE-09A7 under Subtask 7.01, Review of PRP RD/RA Submittals. The EPA WAM requested that CH2M HILL provide an initial general review of the 100% Design submittal and provide any major comments. The documents for general review included Design Drawings and the Design Report.

Shannon Wright, Project Engineer, of CH2M HILL conducted this initial general document review. Comments are highlighted below.

General Comments

There is a bench along the west/southwest area of the final cover grades (approx. elevation 220 ft - 250 ft) that does not have access at all (foot or driving). This will be very difficult to maintain.

There are still several areas along the southerly facing slopes of the final grades that are 1.5:1 (horiz:vert). There are two primary issues that should be addressed or further evaluated, and are summarized below:

With this steep of slope, it will be difficult to place and maintain a 6” soil cover over existing waste prior to placement of geosynthetic materials. A foundation must be in place over these slopes due to the fact that, based on actual field observations, there are visible protrusions (glass, metal, concrete, wood, etc.) that will damage (puncture) the proposed geosynthetic cover materials. A veneer stability anaysis must be performed to demonstrate that the proposed soil materials (foundation soils and cover materials) will maintain stability (FS ≥ 1.5) when placed over 1.5:1 slopes. In addition, a veneer stability analysis (typical for landfill cover system geotechnical analyses) will determine whether the proposed cover system will remain stable over all proposed slopes (2:1 or less included).

The geotechnical analysis performed does not appear adequate to fully demonstrate that the global stability of the slopes is adequate. Typical industry practice on landfills this high with such steep slopes is to do an extensive/random search for the most critical potential circular or wedge/block slip surface. Once determined, a more rigorous

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COMMENTS ON CLOSURE-RELATED DOCUMENTS-ORDOT DUMP

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evaluation is performed on the actual identified critical slip surface. It does not appear that this was performed, and therefore the most critical circular or wedge/block slip surface was not identified.

As discussed above, it would appear that, in general, the geotechnical evaluation does not adequately demonstrate the landfill will remain stable at the critical sections (general global stability appears adequate, however critical failure surfaces have not been identified and evaluated). There should be a veneer stability analysis performed to demonstrate the liner system will not fail (such as analysis of 2:1 slopes with soil over the top of geosynthetics). There are still several questions unanswered. Does the geosynthetic material need to be textured to increase friction angle between the liner materials? What are the friction angles between proposed materials? Will the cover soil over the geocomposite remain stable on 2:1 slopes? Will the foundation layer material remain stable with the overlying geosynthetic/ soil materials? It is recommended that further analyses be performed to demonstrate adequacy of proposed final cover system materials.

While controlling stormwater at one point source will allow for monitoring of surface waters and collection of silt, this may not be the best option when considering the existing wetlands that are to remain. These wetlands depend on runoff from the landfill, and may still require runoff to exist. A biologist should be contacted, such as biologist that delineated the wetlands. In addition, this should be addressed in the wetlands mitigation plan for the site.

There are few necessary analyses missing from the design report. These are:

Sizing of the leachate collection tank. A quick review and rough calculation based on information presented in the design report indicates that the proposed tank is insufficient to adequately contain the potential leachate generated from the landfill.

Annual average leachate generation from report, without cover (A-1_L1): 119.4 gpm Peak leachate generation from report, without cover (A-1_L1): 278.0 gpm Annual average leachate generation from report, without cover (A-1_L2): 25.23 gpm Peak leachate generation from report, without cover (A-1_L2): 386.15 gpm (computed from model results consistent with methodology presented in A-1_L1).

Designing for only one day’s storage, and not taking into account trucks used to remove leachate (scenario where trucks are unavailable, such as weekends, typhoons, etc.), you would need the following capacities:

Annual average, without cover: 171,900 gallons Peak, without cover: 400,300 gallons Annual average, with cover: 36,300 gallons Peak, with cover: 556,100 gallons

Even assuming a BEST case scenario where there would only be an annual average flow (no peaks), you would need at least 37,000 gallon capacity. Generally the design would be based on something that could literally be expected, such as three days to a week down-time for trucks (which could happen due to weather), and would be based on the peak daily generation. You can see that the tanks start to get very large. In addition, if you are using a 4,000 gallon water truck to haul leachate to the WWTP,

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even with the low leachate generation number of 37,000 gallons, there will be up to 10 trips per day to the WWTP that will be needed every day for the entire year. It would appear the tank (or tanks) should be much larger to account for potential down time, and be designed to a worst- to reasonable-case scenario.

Calculations for stability of the tank. The tank requires both a geotechnical evaluation to confirm adequacy of underlying soils as well as a structural analysis to confirm the adequacy of the proposed concrete foundation and any tie-downs that may be necessary to account for potential wind/seismic/etc. loads.

Calculations for stability of the blower/flare system. The blower/flare system requires both a geotechnical evaluation to confirm adequacy of underlying soils as well as a structural analysis to confirm the adequacy of the proposed concrete foundation and any tie-downs (for flare) that may be necessary to account for potential wind and/or seismic loads.

It is unclear as to how the leachate tank would be drained. Is there a pump station associated with the leachate storage tank location that would be included to allow pumping into a truck? Where is the paved truck loading area with secondary containment in the event there is a spill?

The response to comments indicated that the designer was going to contact a landscape architect, biologist, agronomist, or other expert that could confirm whether or not the proposed vines would cover the slopes by growing downslope only (literature indicates the proposed vines do not grow long enough to cover an entire slope length). This evaluation is not included in the submittal.

The sizing of the pumps for the leachate pump station included in the appendices does not appear adequate to account for potential peak discharge. The analysis indicates that the peak discharge for the covered landfill is 25 gpm. This discharge is actually the average annual discharge (see Appendix A-1_L2), and does not represent the peak (see above). Therefore, the pumps do not appear to adequately handle the potential peak discharge from the landfill, leading to a backup in the system and subsequent discharge to the Lonfit River.

Please note that these comments are general and do not constitute a detailed review of the 100% design. If there are any questions regarding the comments presented above, please feel free to contact Shannon Wright at (916) 286-0417.

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BAO/COMMENTS ON 100% DESIGN 1

T E C H N I C A L M E M O R A N D U M 7

Comments on the 100% Draft Final Design Documents for Ordot Dump Closure

PREPARED FOR: Lance Richman/USEPA/Region 9

PREPARED BY: CH2M HILL

COPIES: Rick Sturm/CH2M HILL/SFO Shannon Wright/CH2M HILL/SAC File/CH2M HILL/SFO

DATE: October 18, 2005

This technical memorandum has been prepared as part of the work effort set forth in the Work Plan for Ordot Landfill Superfund Site Remedial Design Oversight under Contract No. 68-W-98-225/WA No. 185-ROBE-09A7 under Subtask 7.01, Review of PRP RD/RA Submittals and its continuation under Option Period 2 WA 285-ROBE-09A7. The EPA WAM requested that CH2M HILL review and comment on the 100% draft final design document submittals. The documents included a Design Report, Geotechnical Analysis, a Construction Quality Assurance Plan, an Operations Plan, a Closure Plan, a Post Closure Maintenance Plan, the 100% technical specifications and the 100% Design Drawings.

Caroline Ziegler, Project Manager, Rick Sturm, Project Hydrogeologist and Shannon Wright, Project Engineer, of CH2M HILL conducted this document review. Comments for each document are highlighted below.

Design Report

1. There should be an analysis that shows design for the thickness of the geomembrane. The wind uplift analysis simply uses the proposed 80-mil HDPE thickness to verify it is adequate without considering other thicknesses in the calculations.

2. The veneer stability of the liner system was not included in the design report. This must be performed to determine interface friction angles and adequacy of the liner system components.

3. There should be an analysis for sizing of pump to discharge from tank. This pump is part of the leachate control system, and is not part of leachate disposal. The tank has to be pumped out regardless of whether the leachate is disposed of or not.

4. There should be analyses of culvert ring deflection and determination of minimum cover depths for culverts around the site. This was not included in the Design Report.

5. The HELP model analysis should only state the comparisons between two alternatives, the proposed alternative and the regulatory required prescriptive design. The current design does not show equivalency to the regulatory prescriptive design, and therefore cannot be considered as equivalent until it is shown, at a minimum, through modeling.

6. It is unclear where the anchor trenches, as designed and presented in the design report, are utilized. The design presented appears to be for anchor trenches placed on benches or top decks, not parallel to the slopes as presented in the design. In addition, if there is

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0-feet run out length, the top edge of the anchor trench between the trench and the slope face will fail. With no run out length, the wedge that would be created by the interface between the slope and the anchor trench would likely shear.

Geotechnical Analysis

The extremely steep slopes and the choice of material strengths is of concern for the following reasons:

1. The site seems to be covered with a layer of clayey silt, 5 to 12 feet in thickness, according to the report. In the calculations for the temporary stability of the MSW cut slope required during construction of the permanent MSE wall, it is suggested that a cohesion of 950 psf be used, which originates from the Geotechnical Summary Report (URS, 2005). In addition, there is an attached reference from Carter and Bentley which is a chart used to predict undrained shear strength in kN/m3 from an SPT n value. A CH material was used on the chart while the text describes that the upper native material is silt. The prediction from the chart is that the undrained shear strength (C) would be 200 kN/m3 (4,200 psf) and suggested using 3,000 psf. From the average value of the silt line on the chart, it would appear that the actual prediction would be C=50 kN/m3 (1,000 psf) which agrees with the 950 psf value given in the 2005 URS geotechnical report.

2. A cohesion value of 3,000 psf was used in all stability analyses for the native material. In addition, the analysis does not appear to consider the drained case for long term stability in any of the calculations.

3. Global stability checks have been provided using the high value for cohesion of the native soil beneath, however it does not appear there are any calculations checking the stability of the 1.5H:1V benched slopes. The steep slopes will have (from top to bottom) geogrid, 80-mil liner, geocomposite drainage layer, and 6 inches of daily cover. How will 6 inches of daily cover be placed and compacted (layer is very thin)? Is the interface friction between the cover materials capable of remaining stable on 1.5:1 slopes?

Construction Quality Assurance Plan

1. Suggest a procedure for bounding nonconforming rolls of geosynthetic materials, providing a definitive method for rejection of rolls instead of leaving it up to the CQA personnel. Rejection of rolls can be a potential for claims if the method for identifying nonconforming rolls is not clearly and specifically defined.

2. Suggest giving the CQA personnel the ability to test destructive samples as an alternative to sending destructive samples to a laboratory. Several qualified CQA consultants have their own calibrated and certified tensiometer and qualified personnel that can do the testing themselves. It could be much less expensive and not as time consuming as compared to sending off-island to either Hawaii or the US mainland.

3. Nondestructive seam testing of geotextile also includes spark testing. 4. Geocomposite testing should include transmissivity. 5. It is not the CQA personnel’s responsibility to request repair techniques on geotextile,

geocomposite, or geogrid. Good CQA consultants will not accept the liability for making these types of decisions. Their role is to simply verify that the construction was performed in accordance with the plans and specifications, and report their findings to the permitting agency following construction in order to obtain official closure of the landfill. These procedures should be clearly spelled out in the specifications, with the CQA personnel simply verifying the repairs were performed in accordance with the

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specifications. 6. There should be a section on reporting and recordkeeping (typical for CQA Plans). This

section details where the CQA personnel keep their records, where duplicates are stored in case of emergency (such as break-ins and fires), the types of forms they are to use, daily inspection report requirements, who is responsible for keeping the as-built drawings up-to-date, etc.

Operations Plan

1. The biggest item missing is a procedure for placement of daily cover, either soil or alternative. There should be an entire section specifying how much soil should be placed over the waste each day (typically minimum of 6 inches), or what type of alternative daily cover may be used. There is discussion within the text, but nothing that provides a clear definition of what must be done.

Closure Plan

1. Section 4 indicates that cover sideslopes will not exceed 1H:1V. These slopes would not be advisable, and have not been shown as stable in any evaluation presented in the design report.

2. Section 4 indicates that roads will be surfaced with crushed aggregate, while the design is calling for AC. This should be reconciled.

3. Please check the statements made within the Closure Plan against the most current design. There are several items that have changed in the current design and still need to be addressed. In addition, there are comments to the current design that should be addressed and incorporated in the closure plan as well.

Post Closure Maintenance Plan

1. No comment. Looks good.

100% Technical Specifications

1. Section 1350 requires odor control if detected within 100 feet of source. The existing conditions around the site far exceed 100 feet from the source. The Contractor will not be able to mitigate odors within 100 feet of the source. If this is enforced, it will add appreciable costs to the closure of the landfill while being generally unobtainable.

2. Section 1350, may consider putting in a no smoking section to emphasize this requirement, and assure it is a part of the Contractor’s H&S Plan.

3. Section 1500 states that the Contractor is responsible for providing an office and equipment for the Construction Manager. This is not standard industry practice when performing landfill construction of this magnitude. First, there will be several CQA personnel when the cover system is being constructed, which will overwhelm a Contractor’s trailer. Second, there will be constant communication from the CM’s office, from faxing to telephone communications, which will overwhelm a Contractor’s communications system. On typical landfill construction projects, the Construction Manager, being an entirely independent party (particularly when it comes to CQA), is responsible for their own office and equipment, which may include testing equipment, faxes, archive space (both soil and liner material), etc. The Contractor cannot know the Construction Manager’s needs for a project this size better than the Construction Manager and their CQA representatives, therefore the Contractor should not be

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responsible for providing any office and/or equipment for the CM. The CM’s office setup is typically a part of their independent contract with the Owner. For convenience, the Contractor could simply be responsible for providing a trailer (could possibly get a discount from the local trailer rental office when renting two or more trailers).

4. Section 02072 specifies a 6 oz/sy geotextile for a filter material (primarily around infiltration layer). There should be an analysis contained in the design report showing that the filter fabric AOS is adequate for the proposed cover materials (the fabric will not clog).

5. There are statements within the specifications that indicate approval of items by the Construction Manager. The Construction Manager should only provide approval of whether or not the items meet the requirements of the Construction Documents. Since the Construction Manager is not the Engineer-of-Record, and is not being held legally responsible for the design and overall function of the landfill liner system, the CM should not approve items that are out-of-compliance with the construction documents. In addition, it may be difficult for DPW to retain a CM that is willing to share this type of liability. However, if the Engineer-of-Record is willing to accept the CM’s design change decisions, and any and all consequences that may result from those decisions, then references to the CM approving items could remain.

6. Section 02075, it is unclear where this is being used around the landfill (see comments to drawings).

7. Section 02230, should strongly consider providing an option in the specification to allow the Contractor to mulch and stockpile green waste for use later when erosion control measures are required. This would be environmentally responsible, is a very effective BMP, and would save costs in erosion control materials.

8. Section 02340, Geocell, only provides one manufacturer. There are several manufacturers available with similar characteristics to the specified manufacturer. Suggest, at a minimum, adding “or approved equivalent.”

9. Section 02370 Erosion and Sedimentation Control, strongly suggest adding mulch to allow the Contractor to utilize native, inexpensive mulched green waste as an option to erosion control blanket.

10. Section 02370 Erosion and Sedimentation Control, what does Part 2.15 Odor Neutralizer and Part 3.06 Odor Control have to do with erosion and sedimentation control?

11. Section 02373 only suggests one manufacturer of ABM. There are several that provide equivalent properties to those specified. Suggest, at a minimum, adding “or approved equivalent.

12. In general, there are several parts of the specifications that call out only one manufacturer of materials. Typically government specifications within the US are not allowed to call out specific manufacturers or at a minimum must list several possible manufacturers in order to obtain the best value possible. Please verify that the Government of Guam does not have similar requirements that require competitive bidding of construction materials.

13. Section 02376, should require that the straw be certified weed-free. Requiring the certification is common practice, and helps reduce the risk of introducing intrusive species over the landfill. Certified weed-free is not synonymous with agricultural straw. Agricultural straw may contain intrusive species of noxious weeds.

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100% Design Drawings

General Comments

1. There is a bench that runs along the entire western side and turns for a brief distance along the south side that does not have access (approx El 250 to 220 on grading plans).

2. There are still several 1.5H:1V slopes that remain along the southern side of the landfill. It would appear that several of these can be modified to shallower slopes since they haven’t been constructed yet.

3. After reviewing the geotechnical stability, it would appear that there was not an evaluation regarding veneer stability (stability of the liner system). This must be performed to demonstrate that the 6” of subgrade soils can safely be constructed on 1.5H:1V slopes as well as remain stable under static and seismic conditions. These foundation soils will become saturated due to the amount of leachate seeping from the sideslopes of the landfill and may create difficulties both during construction and in maintaining this soil on the 1.5H:1V slopes.

4. There should be further work on the line types and thicknesses. Some of the linetypes are similar (such as stormwater ditch, surface water conveyance pipe, existing versus proposed, etc.)

5. Check all callouts to make certain they are correctly cross-referenced. There are several that aren’t called out at all, or are referencing the wrong sheets (for instance, several details/sections reference C-5, however C-5 has now been split into different sheets that now call out those details/sections).

6. Check patterning against details and sections to confirm scale/linetype/line weights are in conformance with the legend.

7. It would appear that the site cannot be permitted or constructed prior to approval of a wetlands mitigation plan. This should be addressed, and approval obtained from all appropriate parties noted in previous response to comments.

8. Check for text conflicts and correct. There are several sheets where text is unclear due to conflict with other graphics.

9. Check spelling. There are a few misspelled words throughout the document.

Specific Comments

Sheet G-4

1. There is a dark line running around the mid area of the landfill that is unidentified. It would appear it is the break between the projected “existing” grades and the existing 2004 grades. Should make it clear what this line represents (such as adding a callout to Note 3).

Sheet G-5

1. There’s a bench at El 260 that does not have any access. This could cause access problems later (see Note 1 under General Comments).

Sheet G-6

Erosion and Sediment Control Notes-General 1. Note 4, it is unclear which plan views show the clearing limit. Please make certain this

limit is clearly shown on the plans so it can be flagged.

Wet Season Requirements

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1. Note 4, an asphalt paved road appears to be unnecessary. This road will be constantly damaged and will require frequent maintenance and replacement, adding additional cost to the project. Suggest a stabilized gravel road (geotextile beneath gravel). Gravel can always be added to the road at a relatively inexpensive cost when areas settle (additional gravel can be stockpiled on site and used as necessary).

Additional Requirements for Stockpiles 1. Suggest giving a compaction specification to Note 3. How will it be compacted? The

Contractor could simply wheel-walk the area, track-walk, or roll with an actual compactor. As the note stands, they could do any of the above, but wheel walking or track walking might not be enough.

2. Why do the stockpiles have minimum 3H:1V? Could likely be 2H:1V, or allow “angle of repose”, thus increasing the capacity of the stockpile and reducing the space needed.

Sheet G-7

1. Note 6. Suggest graphically showing where you anticipate check dams to be placed within the North Run-on Control Ditch.

2. The silt fence along the eastern edge of the site will be relatively ineffective. Typically silt fence is placed parallel to the contour of a slope to be effective in removing silt. However, there are several portions of the silt fence along the eastern side that run roughly perpendicular to the slope contours.

3. Based on the existing contours shown, it would appear that the perimeter drainage will short-circuit at the steep drainage depression located roughly in the middle of the southerly side of the site (near southern check dam), and will not make it to the siltation basin as shown.

Sheet G-8

1. Note 2 indicates sponge gourd will be planted. Suggest an agronomist, botanist, or landscape architect be consulted to verify that sponge gourd will grow long enough to cover the entire exposed slope, with results presented in the design report.

Sheet G-9

1. Detail 2, will the Quarry Spalls crush the CPE? What size of CPE? Suggest having geotechnical engineer evaluate ring deflection of pipe to demonstrate it will not crush during construction. In addition, detail should mention minimum burial depth. If burial depth will be an issue, consider using lengths of steel pipe (6”, 1’, etc.) so crushing is not a concern.

Sheet C-1

1. This sheet should show all existing conditions, including existing wells, items to be demolished, etc.

2. There are still very steep (1.5H:1V) slopes shown along the southern side of the site. Suggest reducing this slope while the operator still has the ability to do this.

Sheet C-2

1. Should show the existing waste limit, primarily along the western edge, so contractor can judge how much waste should be removed.

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Sheet C-3

1. There is a bench located along the western face and a portion of the southern face that does not have access (see note under general comments). Should modify grading to allow for access.

2. Grades at top of landfill should be modified to show the access road. 3. Grades at top of landfill should include a bench. Typically there is a bench every 30

vertical feet for both cut and fills steeper than 3H:1V (per UBC). 4. Note 2 indicates existing facilities shall remain undamaged. This sheet does not call out

existing facilities (fences, buildings, etc.) that shall remain undamaged.

Sheet C-4

1. Note 1 indicates the drawing is finished grades following completion of closure construction. This does not appear to be the case since the contours correspond with the grading plan. This may be the final cover contours following placement of geosynthetic liner, but does not reflect placement of cover soils over the top deck, 2.8H:1V or less slopes, or on benches, which are part of the closure construction.

Sheet C-6

1. Suggest adding a typical detail (on detail sheets) for the stilling basins showing how the channels and chutes tie in.

2. Regarding 36” diameter culvert along northerly side (North Run-On Control Ditch), the ditch looks to be 48” deep, leaving only 12” of cover over the culvert to match adjacent grades. In order to obtain 30” of cover over the culvert, there will have to be an 18” mound of soil over the culvert, leaving access over the culvert relatively difficult.

3. There are 1.5V:1H slopes shown above the MSE wall. Suggest laying these back to 2:1 following construction of the wall. This should be possible since the waste will be replaced once the MSE wall is constructed.

4. The match lines do not line up with the match lines shown on the other sheets.

Sheet C-7

1. Regarding 36” diameter culvert along northerly side (North Run-On Control Ditch), the ditch looks to be 48” deep, leaving only 12” of cover over the culvert to match surrounding grades. In order to obtain 30” of cover over the culvert, there would have to be an 18” mound of soil over the culvert, leaving access to the other side relatively difficult.


3. Will 12” of cover over the culverts along the northeast ditch (2 total) be adequate to eliminate potential for crushing, particularly since this is the main access to the haul road? Should evaluate and include analysis in design report.

4. There should be an actual grading design shown for the southerly drainage channel. There could be a substantial amount of fill that could be required.

5. The match lines do not line up with the match lines shown on the other sheets.

Sheet C-8

1. Should have actual grading design for drainage channels running along perimeter. There are areas that could have a substantial amount of fill.

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3. It would appear that high flows at the overflow could divert either to the east or south. Suggest adding a berm along the southerly flow path to assure drainage is diverted to the east.

Sheet C-9

1. Sponge gourd is a climbing vine that, per literature, grows anywhere from 6 to 20 feet. If this is meant to cover the sideslopes, it may not grow long enough to cover the exposed geosynthetics. Suggest an agronomist, landscape architect, or botanist confirm that the vines will cover the entire sideslope, with results included in the Design Report.

2. Grading should be the final grade contours. 3. It would help to screen the areas requiring different treatment. This will help the

Contractor determine the areas needed for each plant type.

Sheet C-12

1. Note 1, is 6-inches of daily cover soil adequate to protect against possible protrusions from the waste mass? In addition, how will 6-inches of daily cover remain stable over 1.5V:1H slopes (see notes above)?

2. How will the exposed geomembrane be protected from the potential abrasiveness of the ABM? Suggest a geotextile beneath the ABM to protect the geomembrane.

3. Note 5, how will geomembrane be anchored on each bench during welding at the midpoint of each bench?

4. How is the drainage from the sideslopes going to be directed into the drainage channel if there is a lip?

5. Where is Detail 5, strip drain, used?

Sheet C-14

1. Note 1, is 6-inches of daily cover soil adequate to contain possible protrusions from the waste mass? In addition, how will 6-inches of daily cover remain stable over 1.5V:1H slopes?

2. Why use an AC pavement section? It is a flexible pavement under normal live loads (such as a typical roadway activity), but will crack and degrade, will require greater maintenance, and will require replacement due to differential settlement. An aggregate base road will work, would require much less maintenance, and would be less expensive both to construct as well as maintain.

3. Where is the guard rail located with respect to the typical road section? How far from the outer edge will it be placed?

4. What are the dimensions for the anchor trench shown on Section B? 5. Based on the control points (centerline of channel, Section B), there will be a substantial

amount of fill required over the final cover system and existing grades. An actual grading design should be shown on the drainage plans, with the control points adjusted accordingly.

Sheet C-15

1. Detail 1 is ambiguous. While I believe I understand what you are trying to convey, I do not believe the detail accurately represents this concept (suggest extending the

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“overlying geomembrane panel” and “underlying geomembrane panel” to top of detail instead of terminating at the bottom of the anchor trench; stop the anchor trench at the geomembrane “cut” line instead of at the bottom of the cap strip). In addition, it would help to show the toe of slope relative to the anchor trench termination for reference.

2. How will the anchor trench be installed on 1.5H:1V slopes? This will be very difficult to construct.

Sheet C-17

1. Detail 2 shows HDPE boot installed over the geogrid instead of beneath.

Sheet C-18

1. Detail A, it would appear there is a slip plane introduced adjacent to the MSE wall (geosynthetics). Did the MSE wall geotechnical evaluation consider this plane?

2. Detail A, it is unclear where the Control Points for the MSE wall are referenced to. This note applies in general to the MSE wall design drawings as well.

Sheet C-19

1. Profile indicates a 24” culvert, but the plan view shows 36” culvert.

Sheet C-22

1. Detail C appears to be looking downstream, contrary to what is shown on the plan sheets.

Sheet C-23

1. Note 1, it is unclear which channels are lined with riprap. The note should reference TRM as well.

2. Note 2 should include depth for channels lined with TRM as well.

Sheet C-24

1. It is unclear how the edges of the cover soil will terminate at either side of the culvert. Suggest showing a detail on terminations at each end.

2. Should show dimensions on the culvert (what Db and Wb refer to in the table). 3. It would appear that the gravel surrounding the infiltration pipe simply terminates at

the channel. Suggest wrapping the termination with geotextile to reduce the potential for the gravel to slump into the adjacent chute.

Sheet C-27

1. Sections A and B, how far upstream and downstream will the quarry spalls be placed on either side of the weir boulder?

Sheet C-28

1. It would appear that anchorage is necessary for the exposed pond lining to limit the potential for pullout at the anchor trench. Suggest an analysis be performed to design anchorage, such as tires or sandbags.

2. The berms for the detention basin are over 10-feet high in some areas, which is a concern regarding stability. There should be a geotechnical evaluation demonstrating that the berms are adequate to remain stable when full, while meeting the required factors of safety as well as providing a specification for material and compaction to be used to

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construct the berm. It would appear that there is no federal jurisdictional limit, however the design should meet all US Bureau of Reclamation requirements for dams.

3. Suggest adding seep collars to the pipe running through the berm to prevent short circuiting.

Sheet C-29

1. Suggest a cushion geotextile beneath the drainage gravel on the floor of the detention basin. This will keep the geomembrane from being damaged by the gravel during silt removal operations.

Sheets C-32, 33, 34, 35, 36, and 37

1. It is unclear what these points actually control. In some instances (sheet C-33) they control the edge of waste/stormwater controls, in others the points do not appear to represent anything but a point in space. Should pick a reference, such as edge of liner, centerline of ditch, etc. In addition, it would be helpful to put a brief description of the control point in the table following each plan view.

Sheet C-38

1. Detail 5, where does the guardrail align with the edge of pavement?

Sheet L-1

1. It is unclear where the leachate will be removed from the tank. There should be a pad with a collection system to assure that leachate does not leave the site in the event of a spill. This should be designed and constructed at the same time since it is a vital part of the leachate collection and removal system.

Sheet L-2

1. There are a few areas of upgradient flow. This will lead to a relatively quick accumulation of solids, which will clog the system. The system should gravity drain along the entire profile, with no upgradient areas (see “Profile North” between roughly Sta 4+50 to Sta 6+00, and “Profile South” between roughly Sta 8+75 to 10+75).

Sheet L-3

1. Same comment as Sheet L-2.

Sheet L-4

1. Section A, it would appear that the leachate conveyance pipe only applies to Section B, and should be removed from this section.

2. Are there high points along the pressure line leading to the tank? If so, suggest adding air release valves at the high points of the line.

Sheet L-6

1. What are the minimum wall thicknesses for the prefab vault and manhole? 2. Where does the electrical physically tie in to the pump (i.e., how will it be anchored in

the pump station)?

Sheet L-7

1. Based on rough calculations, it would appear that the tank size is inadequate to handle

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the amount of leachate that could potentially be generated. An analysis for tank sizing should be included in the design report.

2. Where are the fasteners for the tank? Has there been a structural analysis performed to assure the tank does not fail during high winds? This analysis should be included in the design report.

Sheet L-8

1. Does the pipe simply end? How will this control leachate if there is no method for removing from the tank?

2. Based on these details, it is apparent that the system is inadequate to control leachate. Without a means to remove leachate from the tank, the tank will overflow, fill the secondary containment, and run offsite.

Sheet L-9

1. What are the subgrade compaction requirements beneath the pad? 2. How much fill, what type of fill, and/or how deep must the soil be scarified and

recompacted? Has there been a geotechnical evaluation to help determine the answer to these questions?

3. Has there been a structural analysis to demonstrate the pad is adequate to support the tank?

Sheet L-10

1. Where is the P&ID for the pump station and control panel? Need to have a way to control the pumps during low flow, high flow, and shutdown.

2. The alarm (alarm beacon) is located on the other side of the landfill opposite the maintenance building. How will maintenance personnel be notified of a shutdown? Suggest a SCADA system or a remote alarm be installed so the pumps can be addressed immediately to assure the pump station does not overflow and discharge leachate offsite. This needs to be shown in a P&ID, which should include control of the pumps.

Sheet LFG-1

1. There are several areas where additional gas wells (outside the radius of influence (ROI) presented in design report appendices, i.e., 300 ft on center, or ROI of 150 ft) should be placed. These include the north side, south side, and east side.

2. There should be gas probes located between the landfill and all adjacent structures to verify compliance with regulations.

Sheet LFG-4

1. The well head/valve station assembly should include a pitot tube or other method for measuring flow through each well. A way to measure flow is imperative to accurately balancing the system and reducing the potential for landfill fires.

Sheet LFG-8

1. Since this is LFG-specific, should leave out reference to the pump station. Another suggestion is to pull out all electrical from the drawings, and put them in a section of their own (typical).

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Sheet LFG-9

Several of the control points do not seem to correspond with the LFG system (e.g. 4011, 4013, 4012, etc.).

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Addendum No. 6 to Request for Proposals No. SWD001-11 … SWD001-11 - Addendum 6.pdf · Page 1 of...

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