FINAL DESIGN REPORT/FINAL EIS/FINAL SECTION 4(F) EVALUATION PIN 0054.05.103 NY Route 347 Safety and Mobility Improvement Project Northern State Parkway to NY Route 25A Towns of Smithtown, Islip & Brookhaven Suffolk County May 2007 Storm Water Management and Roadway Drainage Technical Report Volume II, Appendix F U.S. Department of Transportation Federal Highway Administration NEW YORK STATE DEPARTMENT OF TRANSPORTATION ELIOT SPITZER, Governor ASTRID C. GLYNN, Acting Commissioner
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FINAL DESIGN REPORT/FINAL EIS/FINAL SECTION 4(F)
EVALUATION
PIN 0054.05.103NY Route 347 Safety and Mobility Improvement
Project
Northern State Parkway to NY Route 25ATowns of Smithtown, Islip & Brookhaven
Suffolk County
May 2007
Storm Water Management andRoadway Drainage Technical Report
Volume II, Appendix F
U.S. Department of TransportationFederal Highway Administration
NEW YORK STATE DEPARTMENT OF TRANSPORTATIONELIOT SPITZER, Governor ASTRID C. GLYNN, Acting Commissioner
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Table of Contents Executive Summary .......................................................................................................... 3
Compliance with NYSDEC SPDES GP-02-01 ............................................................ 3 Roadway Runoff and Stormwater Management ........................................................... 4 Roadway Runoff Collection and Conveyance .............................................................. 4
Water Quality...................................................................................................................... 4 Water Quantity.................................................................................................................... 6 Roadway Runoff and Stormwater Management ........................................................... 9
Eliminate Existing MLBS..................................................................................... 11 Utilize Existing RB’s ............................................................................................... 12 Eliminate Discharge to Existing Pipe Systems ........................................................... 14
Roadway Runoff Collection and Conveyance System ........................................................ 19 Inlet Runoff Interception and Spacing ....................................................................... 19 Pipe Diameter ......................................................................................................... 24
Appendices A – Stormwater Quality Calculations B – Stormwater Quantity Calculations C – Eliminate Existing MLBS Calculations D – Utilize Existing RB’s Calculations E – Eliminate Discharge to Existing Pipe Systems Calculations F –Roadway Drainage Evaluation Inlet Runoff Interception and Spacing Calculations Pipe Diameter Calculations
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Executive Summary The Route 347 Safety and Mobility Improvement Project provides roadwy improvements that
include the two additional 3.6 meter wide lanes and a 0.612 meter wide shoulder in each direction
along both sides of the road plus turning lanes at numerous intersections, and various
interchange/intersection alternatives at the Route 454/Route 347 split, Middle Country Road and
Nicolls Road, selected pavement widening of the ramps at the Northern State Parkway, and
variable widening of cross streets.
Runoff from the portion of the project between the high point east of White Oak Drive, Station
18+757, and the high point east of Southern Boulevard, Station 27+612, discharges to the
Nissequogue River and its tributaries. The Nissequogue River is designated a waterbody of the
United States. Therefore compliance with the New York State Department of Environmental
Conservation (NYSDEC) State Pollution Discharge Elimination System (SPDES) General Permit
(GP –02-01 is required for this portion of the project.
The report is divided into three sections, NYSDEC SPDES GP-02-01 Compliance, Roadway
Drainage and Stormwater Management, and Roadway Runoff Collection and Conveyance.
Compliance with NYSDEC SPDES GP-02-01
Compliance with both the water quality requirements and the water quantity requirements of
SPDES GP-02-01, was evaluated in accordance with the procedures contained in the New York
State Stormwater Management Design Manual (NYSSMDM).
Water quality compliance is achieved with the installation of a surface water quality basin, most
likely a stormwater pond or wetland pond, near three existing waterbodies, with overflow and
discharge from each water quality basin to the nearby existing waterbody.
Water quantity compliance for discharges to the Nissequogue River is achieved in accordance
with the provisions of Section 4.7 Downstream Analysis of the NYSSMDM. The increased
runoff resulting from the project is less than five percent of the total existing runoff in the stream
at the point of roadway runoff discharge to the existing watercourses. Consequently, compliance
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with the intent of the Unified Stormwater Sizing Criteria is achieved. Therefore, stormwater
attenuation facilities are not required to address runoff rate changes.
Roadway Runoff and Stormwater Management
Roadway runoff from the portion of the project exempt from compliance with NYSDEC SPDES
GP-02-10, west of high point east of White Oak Drive and east of Southern Boulevard discharges
to either a recharge basin (RB), pipe system or multiple leaching basin system (MLBS). The
objective of the roadway runoff and stormwater management evaluation was to direct runoff to a
recharge basin and eliminate discharge to existing pipe systems and MLBS to the greatest extent
possible. Installation of the proposed 17 RB achieve this objective except for approximately 117
meters of Route 347 in the vicinity of the Route 11 intersection and approximate 697 meters of
the road east of Market Street to Route 25A.
Roadway Runoff Collection and Conveyance
The roadway runoff collection and conveyance and conveyance system was evaluated in
accordance with the requirements of Chapter 8, Highway Drainage, of the NYSDOT Highway
Design Manual (HDM). The runoff collection system evaluation identified the inlet spacing
required along each edge and the median of Route 347 and the resultant quantity of inlets
required for the project. The runoff conveyance system evaluation computed the pipe diameter
required for each pipe to convey runoff to a water quality basin, existing waterbody or recharge
basin. The evaluation also established the approximate invert elevation at each receiving facility
and potential need for use of a “bubbler “ chamber in selected cases when the invert was below
the invert of the receiving facility.
NYSDEC SPDES GP-02-01 Compliance
Compliance with the water quality and water quantity requirements of NYSDEC SPDES GP-02-
01 is described below
Water Quality
Water quality requirements are presented in Chapter 4 of the NYSSMDM. Section 4.2 includes
guidance and procedures to demonstrate compliance with the water quality requirements. The
water quality volume is directly related to the amount of impervious cover created by the project.
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Impervious cover is defined as that portion of the project that does not have permanent vegetative
or permeable cover. Roadway pavement is considered impervious cover. The impervious cover
created by the project includes two components, the additional 3.6-meter wide lane and 0.61
meter wide additional shoulder pavement in each direction for the entire length of the project and
the left turn pavement at the intersections. Proposed sidewalk replaces existing sidewalk.
Therefore, sidewalk installation does not create impervious cover on the project. The impervious
cover created by the project includes four components:
a. two additional 3. 6 meter wide lanes and 0.61 meter wide additional shoulder
pavement in each direction yields a width of 8.42 meters.
b. additional pavement at Northern State Parkway (NSP)
c. additional pavement at cross streets
d. additional turning lane pavement at intersections.
The total area made impervious by the project is 103 753 square meters. Compliance will be
achieved by providing treatment for the runoff from the portion of the roadway equal to the area
made impervious by the project. This will be accomplished by installing surface water quality
basins (WQB), at three locations in undeveloped property beyond wetland limits. The total area
made more impervious by the project of 103 753 square meters yields a required storage volume
of 3 199 cubic meters. The runoff from the portion of the roadway equal to the impervious cover
created by the project within the limits that contribute runoff to each discharge location will be
directed to its respective discharge location. The WQB location, WQB designation, contributing
pavement characteristics required storage volume and storage volume provided are summarized
in Table 1
Table 1 Water Quality Basin Characteristics WQB Contributing Pavement
Characteristics WQv (M3)
Location Designation Station Limits Area Required Provided West East (M2) East of Old Willets Path
WQ-OWP1 19+450 20+150 28 039 808 946
East of Simeon Woods Road
WQ1BR2 21+300 21+455 5 285 153 420
West of Helen Ave. WQ2B2 25+555 27+612 77 171 2 238 2 631 TOTAL 110 495 3 199 3 997
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Runoff will be delivered to each proposed WQB through a closed pipe system that
collects runoff from the portion of the roadway indicated in Table 1. Runoff that exceeds
the storage volume of each proposed WQB will breach the control spillway set an
elevation below the top of the berm for the WQB, and proceed through the adjacent
wetlands to a receiving water body with a culvert crossing at Station 20+630 for WQ-
OWP1, at Station 21+230 for WQ1B2R, and at Station 25+400 for WQ2B2.
The required pipe invert is below the GWT for WQ1BR2 and WQ2B2. Installation of the pipe
with the invert elevation below the GWT, into a drainage chamber with an open grate on top that
allows runoff to overtop the chamber and enter the WQB surrounding the chamber is a reasonable
solution.
The calculations are in Appendix A.
Water Quantity
Overland runoff from the south side of Route 347 is conveyed across Route 347 in various
tributaries of the Nissequogue River at four locations. The location of the existing culvert
crossings that discharge to the Nissequogue River or its tributaries, their configuration and their
contributing watershed roadway limits are presented in Table 2.
West East Grassy Pond Dr. (19+450) West of Old Willets Path
(20+150) WQ-OWP1 1
Rte. 454 Split (22+320) West of Rte 111 (22+883) Steam @ Sta. 21+580 2 West of Rte.111 (22+883) West of Rte. 111 (23+000) MLBS 3 East of Rte 111 (23+650) East of Plaisted
Ave.(24+330) Stream @ Sta. 25+500 2
East of Southern Blvd. (27+612)
East of Lake Ave. (28+072) AJR2 2
East of Lake Ave. (28+072) Grassy Pond Rd. (28+330) 209 2 East of Hallock Rd. (31+900) West of Stony Brook Rd.
(32+040) Nicolls Road 2
West of Nicolls Rd. 33+120) East of Nicolls Rd. (33+700) Nicolls Road 2 West of Belle Mead Ave. (35+000)
West East East of Wireless Rd. (36+300) West of Arrowhead La.
(36+500) XR6 2
West of Arrowhead La. (36+940)
Arrowhead La. (37+143) XR6 2
East of Old town Rd. (38+110) West of Terryville Rd. (39+107)
15AR5 2
East of Rte. 112 (40+498) East of Market St, (41+103) 17AR4 2 East of Market St. (41+103) Route 25A(41+800) MLBS 2 Remarks:
1. Overflow proceeds overland through adjacent wetlands to the stream at Station
20+630.
2. Runoff to be discharged to an existing stream or a proposed RB will be conveyed in a
closed pipe system.
3. Provide longitudinal pipe infiltration system.
The calculations are in Appendix C
Utilize Existing RB’s
Runoff from a portion of Route 347 is currently discharged to an existing recharge basin (RB) at
five locations. These include the RB in the area between eastbound Northern State Parkway,
New Highway and Parkway Drive South, RB-08 on the eastbound side of Route 347 west of
Autumn Drive, RB-0274 on the south side of Route 111 west of the Route 347 intersection, RB-
209 on the eastbound side of Route 347 between Browns Road and Middle Country Road (Route
25) and RB-0276 on the eastbound side of Route 347 west of Stony Brook Road.
Each of the existing RB’s was evaluated to determine how each could be incorporated into the
design. The volume required to contain the storm with a recurrence interval of once in fifty
years was computed by multiplying the contributing area by 0.16 meters (6.3”) of rainfall in
accordance with DM 92 (20) Recharge Basin Design Criteria to determine the geometric
requirements of each existing RB. The results are summarized below.
1. RB at Northern State Parkway
The proposed realignment of Parkway Drive South at the intersection with New
Highway introduces fill into the exiting RB No. SP10, thereby reducing the usable
storage volume. This reduced storage volume will be replaced by increasing the
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slope between the last two contours to the standard one vertical on two horizontal.
This increases the area of the bottom contour and consequently the volume in the RB.
The fill introduced by the project causes a volume loss of approximately 430 cubic
meters as compared to the approximately 585 cubic meters resulting from re-grading
the basin.
2. RB-08, Eastbound Side of Route 347 West of Autumn Drive
Runoff from approximately between White Oak Drive (Station 18+757) and Grassy
Pond Drive (Station 19+450) is discharged to existing RB No.SP08 located on the
eastbound side of Route 347 west of Autumn Drive. The usable storage volume in
existing RB-08 is approximately 4 550 cubic meters.
The required storage volume is 11 840 cubic meters as compared to a usable storage
volume in existing RB 08 of approximately 4 550 cubic meters. Supplemental RB
SRB1B2 to be installed in the property on the eastbound side of Route 347 between
Autumn Drive and New Highway currently owned by Suffolk County provides a
usable storage volume of 12 981 cubic meters.
The surface area of supplemental RB SRB1B2 was limited by the configuration,
dimensions, ground water table elevation and topography of the candidate site. The
ground water table is approximately seven meters below the existing Route 347
elevation at the roadway centerline between Ledgewood Drive and New Highway.
The bottom will be above the ground water table elevation.
3. RB 0274 – Route 111 West of the Route 347 Intersection
Runoff from the eastbound lanes of Route 347 in the vicinity of the Route 111
intersection (approximately between Station 23+000 and Station 23+650) is discharged
to existing Recharge Basin (RB) – 0274 located on the eastbound side of Route 111 west
of the Route 347 intersection. This basin has a history of standing water because of high
groundwater. Rehabilitation to improve infiltration is highly unlikely. Runoff from the
remainder of Route 347 within these limits is conveyed in a closed pipe system to an
existing pond on the westbound side of Route 347 west of the Route 111 intersection.
Opportunity to enlarge this existing pond is limited, primarily due to the small
area of the exiting lot and encroachment of athletic fields. The apparently shallow
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depth to groundwater further restricts the ability to increase volume by increasing
the depth. Installation of a longitudinal infiltration pipe system below the
pavement box and above the groundwater table elevation may be the only
opportunity to create additional storage volume for this portion of Route 347.
Runoff from this portion of Route 347 should continue to be delivered to the
existing pond and RB 0274, supplemented by a longitudinal pipe infiltration
system to supplement the storage volume.
4. RB 209 – Eastbound Side of Route 347 between Browns Road and Route 25
The existing RB provides a usable storage volume of 5 060 cubic meters. The RB
will be re-graded using current RB design criteria to provide a usable storage volume
of 9 975 cubic meters and incorporated into the project.
5. RB-0276 – Eastbound Side of Route 347 West of Stony Brook Road
The small size of this RB and the resultant limited usable storage volume warrants
eliminating this RB from the project.
The calculations are in Appendix D.
Eliminate Discharge to Existing Pipe Systems
Eliminating the discharge of roadway runoff to existing pipe crossings of Route 347 is achieved
with the installation of RB’s also known as a dry extended detention pond, dry pond, extended
detention basin, detention pond or an extended detention pond with adequate a usable storage
volume that contains the runoff with a recurrence interval of once in fifty years.
Identification of sites for the installation of a RB focused on areas within the highway boundary.
This optimizes the use of otherwise unusable areas and minimizes the need for additional
property acquisition. Ramp infield areas at proposed grade separated interchanges are ideal
candidate RB sites. When the required storage volume could not be achieved within the highway
boundary, alternatives were considered in the following sequence:
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1. Expand an existing NYSDOT RB into adjacent vacant land
2. Utilize residual portions of parcels acquired for the roadway project
3. Acquire vacant public property with access denied to Route 347
4. Acquire vacant private property with access denied to Route 347
5. Acquire vacant private property
6. Acquire other private property
RB’s were located as close as possible to the main line low points. This procedure minimizes the
length of pipe required to convey the runoff to the RB and minimizes the depth of the RB
required to contain the required storage volume
Use of the sequential RB site identification procedure described above occasionally yielded a RB
site in some watersheds some distance from the mainline low point location. Also, no candidate
RB site was identified in watershed 4 and 5, since there is no available undeveloped parcel.
Therefore, the runoff from these watersheds is conveyed to the RB’s in the Nicolls Road
interchange area in the adjacent watershed 6.
The configuration of each proposed RB was limited by the site dimensions, ground water table
elevation and topography of the candidate site. RB configuration typically used a six-meter offset
from the property line to the edge of the berm, slopes of one vertical on two horizontal, and a 4.
2-meter wide access ramp with a maximum 12 percent grade into the bottom. The bottom
typically provided a minimum fifteen-meter by ten-meter flat area.
The designation and location of the proposed RB’s is presented in Table 7.
Table 7 Designation and Location of Proposed RBs Watershed Designation
RB Designation RB Location
1 AJR2
Westbound side of Route 347 between Lake Avenue and Gibbs Pond Road
2 MCR2 & MCR4 Middle Country Road ramp infield areas 2 RB 0209 Existing RB on eastbound side of Route 347 between
Brown’s Road and Middle Country Road to be enlarged 3 RB 9DRA Eastbound side of Route 347 between the projection of
Cambon Place (Sta. and Middle Country Road (Sta. 3 MO-3 Westbound side of Route 347 ,,behind exiting shopping
center, between Moriches Road and Hallock Road
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Table 7 Designation and Location of Proposed RBs Watershed Designation
RB Designation RB Location
4 No RB site available in this watershed. Convey runoff to
RB’s in the Nicolls Road interchange 5 No RB site available in this watershed. Convey runoff to
RB’s in the Nicolls Road interchange 6 Opt 1A SPD NR3R1 & NR4R2 Interchange Areas 6 Opt 2A Cloverleaf
Int.1R, Int. 2R, Int. 3R, Int. 4R
Interchange Ramp Infield Areas
7 VR-1 Eastbound side of Route 347 west of Emily Drive 8 WR-1 Eastbound side of Route 347 west of Mark Tree Rd. 9 XR-6 Eastbound side of Route 347 east of Belle Meade Avenue 10 15 AR5 Westbound side of Route 347 between Arrowhead Lane
and Old Town Road 11 AM Eastbound side of Route 347 between Woodhull Avenue
and Terryville Road 11 15 AR5 Westbound side of Route 347 between Arrowhead Lane
and Old Town Road (in watershed # 10) 12 17AR4 Southeast quadrant of the Route 347/Route 112
intersection The volume required to contain the storm with a recurrence interval of once in fifty years was
computed by multiplying the contributing area by 0.16 meters (6.3”) of rainfall in accordance
with DM 92 (20) Recharge Basin Design Criteria to determine the geometric requirements of
each proposed RB. The area that contributes runoff to Route 347 included the roadway and
adjacent berm area along Route 347 plus areas along cross streets, including the adjacent terrain
that slopes toward Route 347.
The contributing watershed limits, contributing drainage area and the required and usable storage
volume in each proposed RB in the non-SPDES compliance portion of the project, east of the
high point ( Station 27+612), between Southern Boulevard and Lake Avenue, are summarized in
TABLE III-8.
The usable storage volume is based on the allowable water surface (AWS) elevation in each RB.
The AWS is either 0.3 meters below the top of berm or 0.3 meters below the lowest elevation of
the roadway that contribute runoff to the RB. The lowest roadway elevation considered the cross
slope of the road and was, therefore set 0.3 meters below the TGL along the eastbound roadway.
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Site constraints, primarily limited viable sites for the installation of RB’s, and the limited usable
storage volume at several sites occasionally required conveying runoff to a RB in an adjacent
watershed as stated in the remarks column of table 8. T