HomeMy WebLinkAbout22SITE3 Stormwater Report Rev1
Stormwater Pollution Prevention Plan
Leemilt’s Petroleum
612 Norwich-Salem Turnpike,
Oakdale, Connecticut 06370
Revision 1
November 4, 2021, January 18, 2022
Freeman File No.: 2021-1106
Prepared for:
Shahani Inc.
53 East Industrial Road, Unit C1
Branford, Connecticut 06405
Prepared by:
Freeman Companies, LLC
36 John Street
Hartford, Connecticut 06106
Stormwater Pollution Prevention Plan
Leemilt’s Petroleum – Shahani Inc.
612 Norwich-Salem Turnpike, Oakdale, CT 06370
ii
Table of Contents
1. Introduction ........................................................................................................................................................... 1
2. Project and Existing Site Description .................................................................................................................... 1
3. Proposed Drainage Conditions ............................................................................................................................. 1
4. Erosion and Sedimentation Control ...................................................................................................................... 2
5. Maintenance and Operations ................................................................................................................................ 3
Appendix A
Figure 1 – Site Location Map
FEMA Flood Insurance Rate Map (FIRMette)
NRCS Web Soil Survey: Hydrologic Soil Group
Appendix B
WQV Worksheet
WQF Worksheet
TSS Worksheet
Stormwater Pollution Prevention Plan
Leemilt’s Petroleum – Shahani Inc.
612 Norwich-Salem Turnpike, Oakdale, CT 06370
1. Introduction
The purpose of this Stormwater Pollution Prevent Plan (SWPP) is to provide information and guidance on the
proposed stormwater management system, and erosion and sedimentation controls during and after project
construction. The site improvements have been designed to be compatible with the surrounding neighborhood,
improve overland stormwater runoff conditions, and not have any significant negative impacts on any downstream
locations.
The SWPP has been developed in accordance with the requirements of the General Permit for the Discharge and
Dewatering Wastewaters from Construction Activities, dated August 21, 2013. The SWPP has been prepared using
sound engineering practices and is consistent with the 2004 Connecticut Stormwater Quality Manual and 2002
Connecticut Guidelines for Soil Erosion and Sediment Control. A copy of this SWPP shall be maintained on-site for
the duration of the construction activity.
2. Project and Existing Site Description
The site is currently a gas station that sits at the south western corner of the intersection of Norwich-Salem Tnpke
(RT 163 / 82) and Raymond Hill Rd (RT 82). The site is approximately 0.96 acres with existing wetlands in the
southwestern corner. Buffering the wetlands is a wooded area, followed by the gas station site in the eastern half of
the property. Stormwater from the wooded area drains to the wetlands. Stormwater from the rest of the developed site
drains in the southeasterly direction. There is an existing catch basin in the northeastern corner of the site that collects
runoff from a catch basin on Norwich-Salem Tnpke, and connects to a catch basin in the southeastern corner of the
site. This catch basin in the southeastern corner has filled with sediment and all stormwater directed to this catch basin,
both overland flow and piped, creates ponding in the immediate area, overtops the existing curb, and outfalls into the
wooded area via overland flow directly to downstream locations untreated.
The proposed project will include, but is not limited to, the renovation of the existing gas station building, installation of
new gasoline pumping facilities, installation of new gasoline storage tanks, installation of a new septic system,
improvements to the existing storm drainage system, and repaving of the asphalt on site.
Freeman Companies has prepared site improvements to the existing proposed Site Plan prepared by North Star
Surveying & Engineering LLC dated 10/23/2020. The site improvements include, but are not limited to, improvements
to the existing storm drainage system to properly treat stormwater runoff prior to discharge per the 2004 CT Stormwater
Manual.
Per the FEMA Flood Insurance Rate Map (FIRMette), the site is not located within a flood plain.
3. Proposed Drainage Conditions
The site improvements to the existing drainage infrastructure include a deep sump catch basin, a Contech Stormceptor
STC 900 hydrodynamic separator, and a level spreader. The stormwater management system will provide treatment
to any stormwater runoff carrying oils, from pumping spills and/or car fluid leaks, prior to being discharged. The system
has been designed to treat the Water Quality Flow (WQF), which is based on the Water Quality Volume (WQV), based
on the 2004 CT Stormwater Manual’s requirements prior to discharge. The discharge will connect to a level spreader
with a subsurface perforated pipe to allow even and less-erosive discharge immediately downstream. All runoff from
impervious surfaces, including the roof of the proposed building, will be captured and treated with the proposed
stormwater management system.
Stormwater Pollution Prevention Plan
Leemilt’s Petroleum – Shahani Inc.
612 Norwich-Salem Turnpike, Oakdale, CT 06370
According to the NRCS Web Soil Survey, the site’s soil is a HSG B soil meaning it is well draining and overland flow
will infiltrate well. For reference, the hydrologic soil group (HSG) is classified based on the soil’s infiltration rate. HSG
type A soils have a high infiltration rate, while a HSG type D has a low infiltration rate.
The WQF was used as the designing factor for the stormwater system instead of the WQV since the WQV is more
appropriate for projects in which a substantial increase in impervious surfaces requires detention. The proposed project
has approximately the same impervious coverage as the existing conditions, therefore, treating the WQF meets the
regulations set by the 2004 CT Stormwater Manual. Both the WQF and Total Suspended Solids (TSS) amounts
required to be treated for this project have been met. Please refer to the appendix for both the WQV and TSS tables.
4. Erosion and Sedimentation Control
It is important that the existing and proposed storm drain systems and their discharges to downstream water resource
areas be protected during and after construction from sedimentation and pollutants to the maximum extent possible.
All materials generated by demolition operations shall be removed off-site and disposed of in accordance with local
and state regulations at approved disposal sites. No demolition debris will be allowed to enter any resource area or to
be stored beyond the limits of work. All demolition debris shall be removed from the site as soon as possible, if not
immediately. For any shortcomings of the control measures, corrective measures shall be taken. These include but are
not limited to: removal of any sediment/debris within the stormwater system, cleaning any area that needs it,
replacement or rebuilding of any non-functioning or damaged components or infrastructure, reseeding any area that
needs it, placement of erosion control fabric as needed. The following are erosion and sedimentation control measures
to be used on site and are delineated on the plan set.
Inlet Protection (Silt Sack) – Inlet protection measures are used to prevent sediment from entering storm drainage
systems. Install inlet protection as soon as storm drain inlets are installed and before land-disturbance activities begin
in area with existing storm drain systems. Clean or replace the protection measure as sediment accumulates, the filter
becomes clogged, and/or performance is compromised. Where there is evidence of sediment accumulation adjacent
to the inlet protection measure, the deposited sediment must be removed as soon as possible.
Compost Filter Sock – The purpose of compost filter sock is to filter sediment as sediment laden water flows downhill
from the disturbance area to the downstream location. Install compost filter sock as shown on the plan set. Leave
space for maintenance between toe of slope and compost filter sock. Install through middle of compost filter sock 10’
apart. Curve the end of the compost filter sock to help contain run off. Remove sediment if it reaches 1/3 the height of
the compost filter sock. Should the compost filter sock decompose or become ineffective, replace section promptly.
Inspect once every 7 calendar days or within 24 hours of the end of a storm event. Inspect compost filter sock for
accumulated sediment height, damage, and gaps between fence and ground.
Soil Stockpiles – The soil stockpiles shall be surrounded by two rows of compost filter sock. Stockpiles stored for
more than 30 days shall be seeded with temporary cover to prevent erosion. Do not hose down or sweep soil or
sediment accumulated on pavement or other impervious surfaces into any storm drain structures.
Temporary Seed and Mulch – Temporary seeding and mulch shall be used no later than 7 days from the last
construction activity on exposed soil areas. Temporary seeding shall be conductive to the season. Seeded areas shall
also be mulched with straw reasonably free from noxious and foreign matter detrimental to the seeded grasses.
Records of all stabilization activities and buffer zone condition shall be kept and noted on inspection reports. Inspect
weekly seeded areas for failure and if needed reseed and repair as soon as possible.
Stormwater Pollution Prevention Plan
Leemilt’s Petroleum – Shahani Inc.
612 Norwich-Salem Turnpike, Oakdale, CT 06370
Soil Stabilization – Hay, straw matting, and/or stone, per the 2002 Connecticut Guidelines for Soil Erosion and
Sediment Control, shall be used in conjunction with each other and used with sediment control measures to reduce
erosion and sediment transport. The soil stabilization measures shall be inspected routinely and if needed
repair/replenish as soon as possible.
5. Maintenance and Operations
It is important that the existing and proposed storm drain systems and their discharges to downstream water resource
areas be protected during and after construction from sedimentation and pollutants to the maximum extent possible.
All materials generated by demolition operations shall be removed off-site and disposed of in accordance with local
and state regulations at approved disposal sites. No demolition debris will be allowed to enter any resource area or to
be stored beyond the limits of work. All demolition debris shall be removed from the site as soon as possible, if not
immediately. Work in high groundwater areas shall be scheduled, when possible, so it can be completed in a dry period
and in the shortest time possible. The following are maintenance recommendations for the various stormwater
management items:
Drainage Structure – New structures shall be installed with hooded outlets for pipes. Each drainage structure shall be
inspected regularly. Any debris within the sump shall be removed.
Paved Areas - Existing driveways and sidewalks shall be swept as needed.
Landscape Areas – Landscape areas shall be mowed regularly. Vegetation shall be pruned as necessary.
Dust Control – Construction activities will result in emissions of dust to the surrounding areas. Spray water as
necessary to control dust from construction activities.
Containment Areas - All chemical and petroleum product containers stored on the site (excluding those contained
within vehicles and equipment) shall be provided with impermeable containment which will hold at least 110% of the
volume of the largest container, or 10% of the total volume of all containers in the area, whichever is larger, without
overflow from the containment area. All chemicals and their containers shall be stored under a roofed area except for
those chemicals stored in containers of 100 gallon capacity or more, in which case a roof is not required. Double-walled
tanks satisfy this requirement.
Waste Disposal - Construction site waste shall be properly managed and disposed of during the entire construction
period. Additionally:
• A waste collection area will be designated. The selected area will minimize truck travel through the site
and will not drain directly to the adjacent wetlands.
• Waste collection shall be scheduled regularly to prevent the containers from overfilling.
• Spills shall be cleaned up immediately.
• Defective containers that may cause leaks or spills will be identified through regular inspection. Any
container found to be defective will be repaired or replaced immediately.
• Any stockpiling of materials should be confined to the designated area as defined by the engineer.
Stormwater Pollution Prevention Plan
Leemilt’s Petroleum – Shahani Inc.
612 Norwich-Salem Turnpike, Oakdale, CT 06370
Dewatering – If dewatering is needed during the construction, it shall be in accordance with the General Permit and
not result in any direct discharges in the storm drain system. Temporary measures shall be utilized to hold, minimize
and reduce the velocities exiting any pumped dewatering waters.
Special Material Precautions – To minimize the potential for discharge of construction materials to the receiving
waters, the following additional precautions shall be followed on the site:
a. Petroleum Products: All on-site vehicles will be monitored for leaks and receive maintenance as needed.
Petroleum products will be stored in tightly sealed containers which are clearly labeled. Any asphalt
substances used on-site will be applied according to the manufacturer’s recommendations.
b. Fertilizers: Fertilizers are not expected as part of this project but if they are used, this Plan shall be
updated accordingly and proper measures shall be taken to cover and prevent spills.
c. Paints and Solvents: All containers will be tightly sealed and stored when not required for use. Washing
or rinsing of paint buckets, brushes or accessories and/or excess material will not be discharged to the
ground surface or the storm sewer system but will be properly disposed of according to manufacturer’s
instructions and State and local regulations.
Spill Cleanup - The following practices shall be implemented during construction activities to mitigate spills of materials
and prevent their release to the waters or the State.
a. Manufacturer’s recommended methods for spill cleanup will be clearly posted and site personnel will be made
aware of the procedures and the location of the information and cleanup supplies.
b. Materials and equipment necessary for spill cleanup will be kept in the material storage area on-site.
Equipment and materials will include but not be limited to brooms, dust pans, mops, rags, gloves, goggles,
kitty litter, sand, sawdust, and plastic and metal trash containers specifically for this purpose.
Potential spills will most likely be related to fuels and lubricants used by the construction equipment. This use will be
monitored and controlled.
Stormwater Pollution Prevention Plan
Leemilt’s Petroleum – Shahani Inc.
53 E Industrial Rd, Unit C1, Branford, CT 06405
Appendix A
Figure 1 – Site Location Map
FEMA Flood Insurance Rate Map (FIRMette)
NRCS Web Soil Survey: Hydrologic Soil Group
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National Flood Hazard Layer FIRMette
0 500 1,000 1,500 2,000250
Feet
Ü
SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT
SPECIAL FLOODHAZARD AREAS
Without Base Flood Elevation (BFE)Zone A, V, A99With BFE or DepthZone AE, AO, AH, VE, AR
Regulatory Floodway
0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mileZone X
Future Conditions 1% Annual
Chance Flood HazardZone X
Area with Reduced Flood Risk due to
Levee. See Notes.Zone X
Area with Flood Risk due to LeveeZone D
NO SCREENArea of Minimal Flood Hazard Zone X
Area of Undetermined Flood HazardZone D
Channel, Culvert, or Storm Sewer
Levee, Dike, or Floodwall
Cross Sections with 1% Annual Chance
17.5 Water Surface Elevation
Coastal Transect
Coastal Transect Baseline
Profile Baseline
Hydrographic Feature
Base Flood Elevation Line (BFE)
Effective LOMRs
Limit of Study
Jurisdiction Boundary
Digital Data Available
No Digital Data Available
Unmapped
This map complies with FEMA's standards for the use of
digital flood maps if it is not void as described below.The basemap shown complies with FEMA's basemapaccuracy standards
The flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 11/8/2021 at 7:14 AM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time.
This map image is void if the one or more of the following map
elements do not appear: basemap imagery, flood zone labels,
legend, scale bar, map creation date, community identifiers,
FIRM panel number, and FIRM effective date. Map images for
unmapped and unmodernized areas cannot be used for
regulatory purposes.
Legend
OTHER AREAS OF
FLOOD HAZARD
OTHER AREAS
GENERAL
STRUCTURES
OTHER
FEATURES
MAP PANELS
8
B 20.2
The pin displayed on the map is an approximatepoint selected by the user and does not representan authoritative property location.
1:6,000
72°12'24"W 41°30'17"N
72°11'47"W 41°29'50"N
Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020
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Hydrologic Soil Group—State of Connecticut
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/8/2021
Page 1 of 445982104598220459823045982404598250459826045982704598280459821045982204598230459824045982504598260459827045982804598290733500733510733520733530733540733550733560733570733580733590733600733610733620
733510 733520 733530 733540 733550 733560 733570 733580 733590 733600 733610 733620
41° 30' 7'' N 72° 12' 8'' W41° 30' 7'' N72° 12' 3'' W41° 30' 5'' N
72° 12' 8'' W41° 30' 5'' N
72° 12' 3'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS84
0 25 50 100 150
Feet
0 5 10 20 30
Meters
Map Scale: 1:580 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:12,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: State of Connecticut
Survey Area Data: Version 21, Sep 7, 2021
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Mar 20, 2019—Mar
27, 2019
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Hydrologic Soil Group—State of Connecticut
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/8/2021
Page 2 of 4
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
15 Scarboro muck, 0 to 3
percent slopes
A/D 0.2 13.0%
23A Sudbury sandy loam, 0
to 5 percent slopes
B 0.3 27.6%
306 Udorthents-Urban land
complex
B 0.7 59.4%
Totals for Area of Interest 1.2 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Hydrologic Soil Group—State of Connecticut
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/8/2021
Page 3 of 4
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—State of Connecticut
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/8/2021
Page 4 of 4
Stormwater Pollution Prevention Plan
Leemilt’s Petroleum – Shahani Inc.
53 E Industrial Rd, Unit C1, Branford, CT 06405
Appendix B
WQV Worksheet
WQF Worksheet
TSS Worksheet
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Project:Designed:NVG Date:11/4/2021
Address:Checked:JNL Date:11/15/2021
0.409 ac
0.957 ac
3. Percent impervious cover, I (Impervious Area/Site Area)42.754
0.435
5. WQV = (1"*R*A)/12 0.035 ac ft
or 1512 cu ft
Conclusion
Water Quality Volume (WQV) Worksheet
Leemilt's Petroleum
612 Norwich-Salem Turnpike, Oakdale, CT 06370
1. Impervious cover area
2. Site area
4. Volumetric runoff coefficient, R = 0.05 + 0.009(I)
WQV to be used for WQF Calculations
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Project:Designed:NVG Date:11/4/2021
Address:Checked:JNL Date:11/15/2021
0.957 ac
2. Site Area 0.0015 sq mi
3. WQV 0.035 ac ft
0.439 in
5. CN = 1000/[10 + 5P +10Q -10(Q^2 + 1.25QP)^(1/2)]93
0.151
630 csm/in
8. WQF = (qu)*(A)*(Q)0.427 cfs
or 192 gpm
Conclusion
The proposed Contech Stormceptor STC 900 hydrodynamic seperator has a treatment
rate of 0.89 cfs which is greater than the required WQF.
Water Quality Flow (WQF) Worksheet
Leemilt's Petroleum
612 Norwich-Salem Turnpike, Oakdale, CT 06370
1. Site area
6. Ia = initial abstration
(Table 4.1 TR-55 - 2004 CT Stormwater Manual)
4. Q = runof depth
7. qu = unit discharge
(Exhibit 4-III TR-55 - 2004 CT Stormwater Manual)
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Location:
A B C D E
TSS Removal Starting TSS Amount Remaining
BMP1 Rate1 Load* Removed (B*C) Load (C-D)
Deep Sump and Hooded
Catch Basin Outlet
0.25 1.00 0.25 0.75
Contech Stormceptor
SCT 900 Hydrodynamic
Seperator 0.80 0.75 0.60 0.15
Total TSS Removal =85%
Project:Leemilt's Petroleum FC#2021-1106
Prepared By:NVG *Equals remaining load from previous BMP (E)
Date:1/18/2022 - Rev_1 which enters the BMP
OUTFALL FROM INFILTRATION SYSTEM
TSS Removal Calculation Worksheet