TOWNSHIP OF CRANFORD Engineering Department

Interoffice Memo

DATE: July 20, 2012

TO: Philip J. Morin, III, Esq.

Township Attorney

CC: Eric Mason, Township Administrator

Leonard Dolan, Fire Chief

D/Lt. Edward Davenport, Police-Traffic Safety

Kevin Campbell, Township Commissioner

Richard Belluscio, Building Sub Code Officer

FROM: Richard A. Marsden Jr., P.E.

Township Engineer

RE: Engineering Department Review of

“Preliminary & Final Site Plan and Application for Flood Hazard Area Individual Permit

Cranford Residential Redevelopment 215 & 235 Birchwood Avenue

Township of Cranford, Union County, New Jersey

Block: 291 – Lot: 15.01, Block: 292 – Lot 2, Tax Maps 63 & 64”

The Cranford Engineering Department has reviewed the referenced application site plans, last

revised June 4, 2012, (containing 25 sheets), engineering report, last revised June 4, 2012, and

the Stormwater Management Maintenance Plan, dated January 2012 prepared by Michael E.

Dipple, NJPE Lic. # 4081200, of L2A Land Design, LLC, 650 Grand Avenue, Englewood, NJ,

07631. The Engineering Department has also reviewed the architectural drawings, last plotted

June 04, 2012, and prepared by a registered architect, Steven T. Moriak, NJRA Lic. #18934,

(containing nine (9) sheets.) The following are my observations and comments that have to be

addressed:

1. SITE PLANS – SHT. C-02: Gate valves are not shown on the field verified enlargement

window. This is important to note, because it would control the outflow of the existing

parking lot stormwater storage. Note, that the engineering report (discussed later) will

show that these gate valve restrictions are not even considered in the existing storage

calculations.

2. SITE PLANS – SHT. C-02: The floodway limit line established in the stream cross

section area located approximately between 100 and 200 feet downstream of the

centerline of Birchwood Avenue, (same cross section that contains two existing

buildings,) does not appear to follow the existing geographic features of this area. The

floodway in this section is located much closer to the existing stream then any of the

other floodway section lines on this plan. The other floodway lines follow the existing

contours more closely, as they should. If you consider the existing structure, like the

building in this section area, the section becomes the most constrictive cross section area

along the stream, and the floodway line should be located much farther away from the

stream. If the existing building is not considered in the cross section equation, then the

manmade mound created by the grass islands and the high point across the driveways

(These elements were created for the driveway to provide surface drainage and access to

the building and prevent ponding in the driveways.) should not be considered in the

section, which should be the case. This section of the floodway line should be located

much more inline with the pre-existing contour lines, along contour elevation line 67, as

is the case with the other floodway section lines. This will pull the floodway line

approximately sixty feet farther away from the stream, making the floodway more

parallel to the contours in the area and the floodplain limit line. However, it will put the

proposed Building “A” in the floodway. Thus, requiring this building to get relocated out

of the floodway.

3. SITE PLANS – SHT. C-03: This demolition plan proposes to remove approximately 280

linear feet of existing 18 inch pipe that originates in the wetlands and catches the water

from the existing ditch. This ditch collects runoff from the existing township drainage

system that traverses through the nursing home, existing detention systems, and the

runoff drainage from Cranford Avenue. Removing this section of pipe will create a back

up effect into the ditch, and the two existing detention systems on the nursing home

property, creating more frequent ponding, thus, affecting the storage capacity in those

detention basins. This backwater would change the hydric characteristic of the soil,

possibly destroying existing wetland habitat and vegetation, and increasing the potential

for breeding of mosquitoes. This piping system should be left in place. In addition, you

will be going into the wetlands to remove this pipe. Wetlands GP#1 permit will be

required for the disturbance of wetlands due to removal of this pipe.

4. SITE PLANS – SHT. C-03: A note should be added to this plan to require construction

fencing around all trees that are to remain undisturbed. This fence shall be placed along

the drip line of each tree or cluster of trees.

5. SITE PLANS – SHT. C-03: This plan should be reviewed by the Construction Sub Code

Officer to see if it complies with all demolition building codes.

6. SITE PLANS – SHT. C-04: The areas noted, as “Lawn & Landscaping and Courtyard”

do not show any sidewalk or patio areas. Also sidewalk and patio areas are not shown

when referring to Sheet C-07 “Landscaping and Tree Replacement Plan.” However, that

plan has open unmarked areas in between the landscaping that we must assume are going

to be grass. These unmarked areas must be labeled “grass areas.”

7. SITE PLANS – SHT. C-04: There are existing storm and sanitary sewer systems

traversing the site. Some have easements, others don’t. We need fifteen-foot easements

along all these utilities, and fifteen-foot access easements to get to these utilities.

8. SITE PLANS – SHT. C-04: At the north corner of the parking garage in Building “B”

there is an open area approximately 12’ and 140’ long that is undefined. However, in the

architects plans its defined as an areaway. Does it have a roof? What is its purpose? Will

it be impervious? How will it drain? Will there be access to it for maintenance?

9. SITE PLANS – SHT. C-04: Fire safety concerns for access, positioning equipment for

fighting a fire, and fire flows should be addressed by the Fire Department. Some concerns

are, firstly, during a flood the fire truck would only be able to enter through the

northeasterly entrance of this 24 foot wide two way street, because the northwesterly

entrance would be under water by more than 2.5 feet. There are no turnarounds for the

fire trucks proposed on this site. They would have to back out. Secondly, the turning

radius of 20 feet for the 90-degree turns, located along the south corners of Building “B,”

will make it difficult for the fire truck to turn. The truck would be turning into the

oncoming lanes at some point in the maneuver and, if oncoming vehicles were

encountered, they would have to back up, extending the time it takes to get to the fire. If

they are moving quickly, there may be a collision due to the restrictive site distance of the

southwest building corner being within 10 feet of the curb. This roadway should be

wider. Thirdly, as shown on Sheet C-05, the northwesterly entrance has a steep incline of

12% right after you enter it. This can put the fire truck at risk of bottoming out. Finally,

once the fire ladder truck is in position to fight the fire, they would be setting down their

stabilizers, which have an 18-foot spread. If the truck driver were perfectly positioned,

there would only be 6 feet remaining in the street for passing vehicles, like police and

ambulance vehicles that would have to negotiate around the truck. There should be fire

lanes established along this building to prevent other vehicles from parking in the areas

close to the building, and this loop road should be 30 feet wide to provide room for other

emergency vehicles to pass.

10. SITE PLANS – SHT. C-05: The proposal to raise Birchwood Avenue over 1-1/4 feet is

the solution the applicant is requesting to meet the NJDEP requirement of maintaining

one access during a flood. However, to get the northeasterly entrance out of the flood

plain they will push the 100-year flood line approximately one hundred feet closer to

the stream. This will reduce the stream cross-section and raise the height of the

flooding upstream. What impact will this filling in of the flooded roadway have on the

upstream properties, which properties include the Township Conservation Center and

Wetlands?

NJDEP Flood Hazard Area Control Rules, Section 7:13-11.3 Requirements for

excavation, fill and grading activities Sub-section (b)1, states that the following

requirement has to be met, “The overland flow of stormwater is not impeded and

floodwaters can freely enter and exit the disturbed areas,.. .” By filling in the roadway in

a portion of the floodplain, the hydraulic stream section is being reduced and the

floodwaters are impeded from entering the downstream floodplain. The loss in the

stream section due to the roadway fill is approximately 12%. In fact, this section is not

the only stream section that has been reduced. When we looked at the Engineers report

there were no hydraulic model stream sections between the upstream entrance and

downstream exit of the 624 linear feet of twin 36x60 inch elliptical concrete pipe. That

means that this roadway section was not even considered in the flood hazard area design

elevation and tailwater determinations.

At the upstream entrance to the twin pipes there is a split in the flow of the floodwater

that may have a significant impact on the backwater into our roadway and conservation

center. At this point the flows should be evaluated as split flows, one through the twin

pipes and the other overland across the Conservation Center and Birchwood Avenue.

This part of the split flow, the overland flow, crosses the diagonally at the intersection of

Birchwood Avenue with the entrances of the Verizon parking lot and the westerly

proposed driveway of this application. This hydraulic stream section is only 330 linear

feet where the section at the upstream and downstream end of the twin pipes are 980 and

688 linear feet respectively - significantly narrower then the other sections. (To get the

entrance driveway out of the floodplain as quick at possible, the proposed entrance drive

climbs up 4 feet in fifty feet, filling in the floodplain approximately 1.5 feet in this cross

section.) The loss in this stream section due to the driveway fill is approximately

18%. This reduction in the stream section will additionally impede the floodwaters

from passing through the site, making an existing upstream flood condition even

worse.

11. SITE PLANS – SHT. C-05: Where will all the plowed snow go on the inside curve of

the loop road when there is sidewalk up against the curb, and building “B” is only an

average of 6 feet away from that sidewalk, and where will all the plowed snow go along

the outside curve of this loop road, when there is guide rail or 90 degree parking. There is

no room to plow the snow in the sides. There are no designated areas showing the storage

of plowed snow. This will also impact the Fire Department access.

12. SITE PLANS – SHT. C-05: A new 8 inch sanitary line is being proposed to connect into

our existing manhole located in the wetlands. This new line will require excavation in the

wetlands, wetlands buffer and floodplain. The mitigation and disturbance of wetlands and

wetlands buffer is not considered anywhere in this plan package. A Wetlands GP#2

permit will be required for the disturbance of wetlands due to construction of this pipe.

13. SITE PLANS – SHT. C-05: The new pipe will be paralleling the wetlands line. This

wetlands line is within the 76 and 77 foot ground elevation. The pipe is averaging more

the 10 feet deep in this area. This places the pipe invert between elevation 71.8 and 68.8,

far below the wetlands surface grade and below the streambed elevation. Unless there are

cutoff walls place across this sanitary sewer system, the new trench can act like a conduit

transporting the ground water out of the area and possibly drying up the wetlands.

14. SITE PLANS – SHT. C-05: The proposed sanitary pipe invert elevation located at the

top of the system is just below the invert elevation of the proposed storm water pipe

system in that same area. The proposed lateral that will collect the sanitary sewer flows

from the northern part of Building “B” may conflict with the elevation crossing of this

storm line. This pipe crossing should be checked and the pipe elevations noted on the

plan. Also a concrete bridge should be poured between the pipe crossings.

15. SITE PLANS – SHT. C-05: The additional sanitary sewer flows added to this new

piping system would stress our already old system. What’s to guarantee that the added

flow of 360 dwelling units will not accelerate the deterioration of our piping system?

The “Sanitary Sewer Capacity Study,” prepared by L2A Land Design LLC in January

2009 indicated that there were three sections of piping system that were inadequate. In

their conclusion they also indicate that inflow and infiltration had increased the flow rates

between 40% and 50%. However, nowhere did they recommend a remedy to resolve the

insufficient capacity, and inflow and infiltration problems. We need to be provided

documentation that shows how this change in unit count will affect our existing sanitary

sewer system, and then provide a remedy for those insufficient areas in our piping

system.

16. SITE PLANS – SHT. C-05: The outflow rip-rap apron located at the upstream end of the

stream should be designed in accordance with “The Standards for Soil Erosion and

Sediment Control in New Jersey.” The outflow velocities of the proposed 24-inch

stormwater pipe have to be reduced to the point where they do not erode the opposite

bank of the stream. Calculations for the dimensions and size of the outflow rip-rap apron

will have to be provided. When proposing stormwater discharges, the designer should be

aware that no outfall structure be oriented toward lands not owned by the applicant. This

is prohibited unless the applicant can obtain written permission from the effected

property owners, per NJAC 7:13-9.2(f).

17. SITE PLANS – SHT. C-06: The lighting plan shows 16 foot tall street lamps along the

inside of the 10 foot buffer located along the west side of the property. These lights

would be intermixed with the proposed arborvitae. Lighting would become ineffective

once these trees grow. The lights should be moved away from the tree buffer area.

18. SITE PLANS – SHT. C-06: There should be lighting in front of the complex along

Birchwood Avenue, because 360 units will generate pedestrian pick ups and drop offs in

front of the complex. The lighting should be the Townships standard lamps that are used

in the downtown area.

19. SITE PLANS – SHT. C-06: Police may want the 140 feet deep breezeway that faces

Birchwood Avenue lit for safety and security reasons. It is the only breezeway around

Building “B” that is not lit.

20. SITE PLANS – SHT. C-07: Arborvitae grows to 60 feet tall. The building next to it is 55

feet tall. The distance between the two is approximately 55 feet apart. There would be

limited time of sunlight to this area. In addition, the plantings in the courtyards will have

the same reduction of sunlight. I recommend that a landscape architect review the

Landscape Plan to see if there will be issues with the duration of sunlight for these

proposed plantings. As great as these landscape plans look, if the plant does not get the

proper amount of sunlight it will die or not grow fully, and the areas will look baron. In

addition, the planting should be native to the region. We have been getting foreign

species along our river ways, that are choking the native species and changing the flow

characteristic of the rivers.

21. SITE PLANS – SHT. C-08: Silt fence location is to close to Building “A.” It measures

approximately 5 feet off the building. This provides no room for machinery, excavation

for footings and any other work needed for construction of the building from the outside.

Silt fencing should be at a minimum of 15 feet off the proposed building lines.

22. SITE PLANS – SHT. C-08: The proposed topsoil stockpile location is 5 feet off the

proposed building “B” wall. In addition, the proposed stockpile is in a breezeway where

it is surrounded by three sides of the building. How is the construction machinery going

to get around this pile to construct footings, the two drainage pipe that go under the pile,

and deliver construction material?

23. SITE PLANS – SHT. C-09: The sanitary sewer profile shows the pipe to over 12.5 feet in

the ground. We need to know pipe design specifications, and that the pipe can sustain the

weight of the saturated soils in this area. Or you need to change the pipe to cast iron.

24. SITE PLANS – SHT. C-014 through C-17: The end-area storage calculation table does

not account for the volume displaced by Building “B” structural walls and columns that

have to support the building, and the supports for the stairs, elevator, mechanical room

and for the protection needed for the bathroom plumbing that will be exposed to the

floodwater flows.

25. SITE PLANS – SHT. C-20: The outflow rip-rap apron detail should be designed in

accordance with “The Standards for Soil Erosion and Sediment Control in New Jersey.”

The outflow velocities of the proposed 24-inch stormwater pipe have to be reduced to the

point where they do not erode the opposite bank of the stream. Calculations for the

dimensions and size of the outflow rip-rap apron will have to be provided.

26. SITE PLANS – SHT. C-22: The “5’ x 10’ Structure W/Backflow Preventer” detail needs

to be revised to clearly show that end of the “Tideflex” check valve (the part that extends

furthest away from the wall of the chamber) clears the floor of the chamber by 6 inches,

not 6-inches at the chamber wall. Some “Tideflex” check valves curve downward as they

leave connection at the wall.

27. SITE PLANS – SHT. TA-01: This plan does not show the impact of the proposed

sanitary sewer as it passes through the wetlands and buffer to connect to the existing

sanitary sewer manhole. Nor does it show the impact of the proposed stormwater outflow

rip-rap apron as it connects to the stream. Disturbance of the wetlands should be

mitigated.

28. SITE PLANS – SHT. TA-01: The impact to the wetland buffers along the south wall of

Building “B,” and along the proposed retaining wall (located along the proposed loop

road) is only 5 feet from these structures. To build the footing for these structures and

provide the needed construction access for machinery to build these structures, you need

15 feet, or explain how these structures are to be built with only 5 feet of space without

cutting into the buffer.

29. SITE PLANS – SHT. TA-02: There should be a note stating that a construction fence

should be placed along the final buffer average limit line, so that construction vehicles

will not encroach beyond those limits.

30. ARCH PLANS – SHT. 1: Trash collection areas are shown within the parking garages.

With a floor–to-floor elevation difference of 11 feet 6 inches and approximately a 3-foot

reduction for concrete main beams, vehicular clearance would be 8 feet 6 inches. A

standard garbage truck cannot make those clearances. How will the garbage be picked

up?

31. ARCH PLANS – SHT. 1: There is annotation stating “Lobby Amenity Leasing At

Ground Level” at the pool entrance of Building “B.” If there is proposed leasing to

outside organizations, or even residents with guests, where will they park?

32. MAINTENANCE MANUAL – Pg. 2: There needs to be a paragraph describing the area

of flood storage under Building “A.”

33. MAINTENANCE MANUAL – Pg. 6: Section VIII.A.3. should be rewritten, starting at

the second sentence, as follows: “This work may require an engineering design

consultant to prepare construction or rehabilitation plans for review and approval to the

township engineer.” The last sentence should read, “Should rehabilitation work be

required, it is recommended that you contact the design engineer of record:”

34. MAINTENANCE MANUAL – Pg.7: The word “Wayne” and “Division” should be

taken out and replaced with “Cranford” and “Department” in paragraph “C.”

35. MAINTENANCE MANUAL – Pg. 8: The word “Passaic” should be replaced with

“Union” located in the last paragraph on this page.

36. MAINTENANCE MANUAL – Pg. 9: The words “and/or JCP&L” should be removed in

the last paragraph on this page.

37. ENGINEER REPORT – Stormwater Section: This report broke the surface drainage

areas into three major sections, because area DA-1 has to be routed through the parking

lot detention area, and area DA-2 is routed through a grass depression. Area DA-3 is not

required to be routed through any detention or storage system. However, when the

surfaces were broken down into classification areas for woods, grass, etc, there are no

plans showing what areas were considered as wooded or grass, other then the survey that

shows woods line limit symbols. We need a map showing these sub-section breakdowns,

because, if all the areas not encompassed by the woods line symbol are considered as

grass areas, we need to look at breaking the grass areas down more, or change the surface

designation, because there are stands of large trees that canopy most of the grass areas.

38. ENGINEER REPORT – Stormwater Section: The existing condition CN numbers used

for grass in much of Area #3 should be increased because these areas do have a canopy of

trees covering the ground, and thin cover of grasses and mosses. The CN numbers should

be more in the range of 82 and 86 for soil groups C and D, as designated in your Table

2.2c “wood-grass combination – poor.”

39. ENGINEER REPORT – Pond Report Pond #1 – 215 Parking Lot: This report shows the

outlet orifice control to be a 12” diameter pipe. These calculations never considered the

outflow restrictions that the gate valves had on each of these existing 12” outflow pipe.

Or the gate valves were assumed to be completely open in the analysis of the parking lot

storage and outflow conditions. This is not the correct way to determine the storage in the

parking lot. Why would the existing parking lot stormwater systems have gate valves if

the regulated outflow were set for a 12” diameter pipe opening, which is the existing size

of the pipe leading to the gate valves? Any backup flow from the main brook would not

flood the parking lot, because the parking lot elevations are higher then the 100 flood

elevation in this area. Therefore you would not need these valves to prevent backup into

the parking lot. The backup of floodwater into the existing parking lot stormwater system

would only help in storing the floodwater for a longer period of time. The valves had

purpose of regulating the outflow and were only opened all the way to clean out the

system. However, this reduced opening cannot be determined unless you go back to the

original design criteria that required this type of detention system. We do not have those

old engineering calculations. So, the only way to determine the opening size for the gate

valves is to assume the site as undeveloped and recreate the outflow requirements using

the dimensions of the parking detention and overflow controls.

40. ENGINEER REPORT – Pond Report Pond #1 – Pond #4 – Underground Basin: Our

engineering consultant, P.S.& S., has to look at the storage methodology used, starting

with the last chart of the last page of this report entitled “Stage/Storage/Discharge Table”

to confirm the following. It appears that there is no outflow from the proposed

underground storage facility until it fills up 3.62 feet or to elevation 78.12. However, the

24” diameter orifice control invert for this structure is at 74.00.’ The Backflow Preventer

check valve will keep the floodwaters from coming into the underground detention basin.

But it will also allow the detention basin to outflow until these floodwaters come up to

the base elevation of the detention structure. So at the beginning of a storm event, there

would be an small outflow rate that progressively gets larger until the flood waters from

the main stream back up into this outflow detention system. This is not reflected in this

table. If this water is not detained on the site opposite of what the

“Stage/Storage/Discharge Table” indicates, we will be releasing runoff faster then the

existing conditions did, and not opening up the detention structure for additional storage

for the flood waters. I’m not convinced their methodology works. A design that is

below the flood hazard flood elevation must take into consideration the function of the

basin during both flood and non-flood events. The rate of discharge from the basin may

be significantly reduced by the tailwater conditions on the receiving water.

When I had to design detention facilities in or below a flood elevation I either compared

the difference in the time of concentration of the main river with the time of

concentration of the runoff passing through the detention structure, and left additional

storage in the detention facility for the runoff that could no longer get out, or I just

designed my system so that the required storage would be above the flood elevation,

knowing that some runoff would still be discharging, but at the same rate as the existing

site conditions. The various storm event lag times of the stream with the discharge times

from the storage basin have to be evaluated.