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Hudson Engineering & Consulting, P.C.

STORMWATER POLLUTION PREVENTION PLAN

1216 Henry Avenue Subdivision Village of Mamaroneck - New York

January, 2015

REVISED: June 16, 2015 REVISED: December 10, 2015

Hudson Engineering & Consulting, P.C. 55 South Broadway

Tarrytown, NY 10591 914-909-0420

Hudson Engineering & Consulting, P.C.. Page 1 of 17

Table of Contents

1) Narrative:

a. Introduction

b. Methodology

c. Pre-Design Investigative Analysis

d. Pre-Developed Condition

e. Post-Developed Condition

f. Construction Phase

g. Construction Sequencing

h. Erosion and Sediment Control Components

i. Construction Practices to Minimize Stormwater Contamination

j. Stormwater Management Facilities Maintenance Program

k. Conclusion

Appendix A – Extreme Precipitation Table

Appendix B – Watershed Maps

Appendix C – Pre-Developed Analysis (HydroCad®)

Appendix D – Post-Developed Analysis (HydroCad®)

Appendix E – USDA Soil Map & Data

Appendix F – Percolation & Deep Hole Test Data

Appendix G – Contractors Certification Statement

Appendix H – Stormwater Management Construction Checklists


STORMWATER POLLUTION PREVENTION PLAN

1216 Henry Avenue Subdivision Village of Mamaroneck– New York

December 10, 2015

INTRODUCTION

This Stormwater Pollution Prevention Plan presents the proposed Best Management Practices (BMPs) to control erosion and sedimentation, and manage stormwater during and after the construction of a proposed subdivision that includes one existing and two proposed single family dwellings on a site located at 1216 Henry Avenue in the Village of Mamaroneck, Westchester County, New York.

The report, consisting of this narrative with enclosures and a plan set entitled: “Proposed Subdivision – 1216 Henry Avenue, Village of Mamaroneck, Westchester County – New York”, all as prepared by Hudson Engineering and Consulting, P.C., Tarrytown, New York, last revised December 10, 2015. The design has been prepared to meet the requirements of the Village of Mamaroneck.

METHODOLOGY

In accordance with the Village of Mamaroneck Village Code, specifically, Section 294-8 (B) (2)(b);

All construction activities resulting in a land disturbance greater than 2,000 square feet and less than one acre shall include stormwater quality and quantity controls (post-construction stormwater runoff controls), as set forth in § 294-9 and described in the Design Manual, to provide treatment of the water quality volume (WQv) through runoff reduction, and to attenuate the post-development twenty-five-year design storm, twenty-four-hour peak discharge rate (Qf) to predevelopment rates.

The stormwater analysis was developed utilizing the Soil Conservation Service (SCS) TR-20 methodologies (HydroCad®) to assist with the drainage analysis and design of the mitigation practice. The “Complex Number” (CN) value determination is based on soil type, vegetation and land use. The CN and Tc data is input into the computer model. The project site was modeled for the peak rates of runoff from the 1-, 10-, and 25-year Type III – 24-hour extreme storm events in both the Pre- and Post- Developed Conditions, per Village requirements. See Extreme Precipitation Table contained within the report.


The stormwater management system is designed to produce post-developed conditions that reduce or equal the total stormwater runoff rates of the pre-developed conditions.

PRE-DESIGN INVESTIGATIVE ANALYSIS

A pre-development investigative analysis was performed at the site. Four (4) deep test holes were excavated and labeled TP-1, TP-2, TP-3 and TP-4, as shown of the plans. Additionally, 12-inch diameter, 24-inch deep percolation holes were excavated at the location of each test hole and pre-soaked as required. A series of percolation tests were performed until a constant rate was achieved. The data is summarized below. See Deep Test Hole logs and Percolation Test sheets contained within the report.

TP-1 was excavated to a depth of 14-inches. The test revealed topsoil to a depth of 4-inches and brown silty sand to the invert. Ledge rock was encountered at 14-inches. No groundwater was encountered. An average percolation rate of 2.16-minutes per inch (28-inches per hour) was observed

TP-2 was excavated to a depth of 36-inches. The test revealed topsoil to a depth of 4-inches and silty sand to the invert. Ledge rock was encountered at 36-inches. No groundwater was encountered. An average percolation rate of 2.16-minutes per inch (28-inches per hour) was observed.

TP-3 was excavated to a depth of 30-inches. The test revealed topsoil to a depth of 4-inches and brown silty sand to the invert. Ledge rock was encountered at 30-inches. No groundwater was encountered. An average percolation rate of 0.66-minutes per inch (90-inches per hour) was observed.

TP-4 was excavated to a depth of 28-inches. The test revealed topsoil to a depth of 4-inches and brown silty sand to the invert. Ledge rock was encountered at 28-inches. No groundwater was encountered. An average percolation rate of 1.2-minutes per inch (50-inches per hour) was observed.

See Deep Test Hole logs and Percolation Test sheets contained within the report.

The site can be characterized as moderately sloping from the east to west. The Hydrologic Soil Group Classification, based upon the USDA Soil Survey, is ‘Urban land-Chatfield-Rock outcrop complex, rolling. See attached USDA Soil Survey Map and Report.

PRE-DEVELOPED CONDITION

For the purpose of this analysis, the existing lot is divided into four watersheds: [Watershed 1A], [Watershed 1B], [Watershed 2A], and [Watershed 2B].


[Watershed 1A] consists of 4,316 square feet of grass land and the proposed driveway. The impervious driveway totals 267 square feet and the watershed is generally sloped toward Design Point [DP-1] on Henry Ave. The weighted CN value for this area is 80 and the total Tc is 4.0 minutes.

[Watershed 1B] consists of 4,574 square feet of grass land and the existing front steps/walkway. Impervious areas total 124 square feet and the watershed is generally sloped toward Design Point [DP-2] on Henry Ave. at the southwest corner of the property. The weighted CN value for this area is 80 and the total Tc is 5.1 minutes.

[Watershed 2A] consists of 6,781 square feet of grass land. This watershed contains no impervious surfaces and is generally sloped toward Design Point [DP-3] at the northwest corner of the property. The weighted CN value for this area is 79 and the total Tc is 6.2 minutes.

[Watershed 2B] consists of 1,829 square feet of total surface area – all of which is impervious. This watershed consists of the existing house and a completed addition. The CN value for this area is 98 and the total Tc is 1 minute (direct entry). The stormwater runoff from this tributary area is conveyed via a comprehensive on-site drainage system to six (6) existing Cultec 100HD units set in one foot of gravel at the sides and invert. The system has the capability to fully accept (no release) the 50-year extreme storm event.

Using the HydroCAD® program the pre-developed runoff rates from the four watersheds were calculated to be as follows (in cubic feet per second):

Design Point

1-Year 10-Year 25-Year

Watershed 1 DP-1 0.28 0.75 1.04

Watershed 2 DP-2 0.19 0.53 0.73

See Sheet No. WS-E for additional information on existing watersheds.

POST-DEVELOPED CONDITION

The post-developed condition includes construction of two new dwellings each with a driveway and walkway.

For the purpose of this analysis, the post-developed lot(s) are divided into five watersheds: [Watershed 1A], [Watershed 1B], [Watershed 1C], [Watershed 2A] and [Watershed 2B].

[Watershed 1A] consists of 5,212 square feet of grass land, the existing driveway (for the existing house) along with the proposed driveways and walkways for Lots 1 and 3. The impervious areas total 1,219 square feet and the watershed is


generally sloped toward Design Point [DP-1] on Henry Ave. The weighted CN value for this area is 83 and the total Tc is 5.2 minutes.

[Watershed 1B] consists of 1,375 square feet of total surface area – all of which is impervious. This watershed consists entirely of the proposed house on Lot 3. The CN value for this area is 98 and the total Tc is 1 minute (direct entry). The stormwater runoff from this tributary area is conveyed via a comprehensive on-site drainage system to and attenuation gallery consisting of Sixty (60) linear feet of 24-inch solid HDPE pipe. Flow control is provided via two staged orifices and the attenuated runoff is conveyed via a 6-inch HDPE pipe to a proposed catch basin located in Henry Avenue adjacent to the southwest corner of the property, where it meets with the runoff from Watersheds 1A, 1C and 2B. From here the runoff is conveyed to an existing catch basin located at the corner of Henry Avenue and Florence Street. The system is designed to convey and control the flow rates for the 1-year, 10-year and 25-year storm events to be less than pre-existing conditions, thereby complying with Village Code, as well as bypass the flows of storms of higher intensity.

[Watershed 1C] consists of 1,375 square feet of total surface area – all of which is impervious. This watershed consists entirely of the proposed house on Lot 1. The CN value for this area is 98 and the total Tc is 1 minute (direct entry). The stormwater runoff from this tributary area is conveyed via a comprehensive on-site drainage system to and attenuation gallery consisting of Sixty (60) linear feet of 24-inch solid HDPE pipe. Flow control is provided via two staged orifices and the attenuated runoff is conveyed via a 6-inch HDPE pipe to a proposed catch basin located in Henry Avenue adjacent to the southwest corner of the property, where it meets with the runoff from Watersheds 1A, 1B and 2B. From here the runoff is conveyed to an existing catch basin located at the corner of Henry Avenue and Florence Street. The system is designed to convey and control the flow rates for the 1-year, 10-year and 25-year storm events to be less than pre-existing conditions, thereby complying with Village Code, as well as bypass the flows of storms of higher intensity.

[Watershed 2A] consists of 6,243 square feet of grass land, with 247 square feet of impervious patio area. This is generally sloped toward Design Point [DP-2] along the western property boundary. The weighted CN value for this area is 80 and the total Tc is 9.4 minutes.

[Watershed 2B] consists of 1,829 square feet of total surface area – all of which is impervious. No change from the pre-developed condition is proposed to this watershed. This watershed consists of the existing house and an approved addition (Lot 2). The CN value for this area is 98 and the total Tc is 1 minute (direct entry). The stormwater runoff from this tributary area is conveyed via a comprehensive on-site drainage system to six (6) existing Cultec 100HD units set in one foot of gravel at the sides and invert. The system has the capability to fully accept (no release) the 25-year extreme storm event. A 6-inch overflow pipe has also been provided which has been designed to convey the flows for storms of


higher intensity. This overflow meets with the discharge from Watersheds 1B and 1C (Lots 1 and 3) and is conveyed to a proposed catch basin in Henry Avenue. From here it joins with the runoff from Watershed 1A and is conveyed to an existing catch basin located at the corner of Henry Avenue and Florence Street.

Using the HydroCAD® program, post-developed runoff rates were calculated for the six watersheds and total runoff rates (in cubic feet per second) were determined for comparison to the pre-developed condition rates:

Design Point

1-Year 10-Year 25-Year

Watershed 1 DP-1 0.28 0.64 0.99

Watershed 2 DP-2 0.16 0.45 0.63

See Sheet No. WS-P for additional information on proposed watersheds. All Post-Developed Condition rates are less than Pre-Developed rates.

CONSTRUCTION SEQUENCING

The following erosion control schedule shall be utilized:

1. Install a stabilized construction entrance at the access point(s) to the site.

2. Install orange construction fencing around all proposed Cultec® infiltration field areas to avoid compaction.

3. Selective vegetation removal for silt fence installation.

4. Install silt fence down slope of all areas to be disturbed.

5. Install tree protection.

6. Remove trees where necessary (clear & grub) for the construction of the common driveway and individual driveways.

7. Strip topsoil and stockpile at the locations specified on the plans (up gradient of erosion control measures). Temporarily stabilize topsoil stockpiles (hydroseed and install silt fence around toe of slope).

8. Grade driveways. Stabilize driveways with base course material. Stabilize all newly graded areas with hydroseed or hold/grow fabric.

9. Stabilize all newly graded areas with hydroseed or hold/grow fabric.


10. Commence construction of residences. De-compact and aerate all disturbed areas to be planted (lawn & landscaping) utilizing Model AE401H5T Aerator as manufactured by Billy Goat.

11. Install Cultec® systems and connect roof drain leader piping.

12. De-compact and aerate all disturbed areas to be planted (lawn & landscaping) utilizing Model AE401H5T Aerator as manufactured by Billy Goat.

13. Fine grade and seed the entire project site and install landscape plantings.

14. Install asphalt pavement for the driveways.

15. Remove all temporary soil erosion and sediment control measures after the site and stormwater pond is stabilized with vegetation. Remove temporary drain inlet plugs.

*Soil erosion and sediment control maintenance must occur every two weeks and prior to and after every ½” or greater rainfall event.

EROSION AND SEDIMENT CONTROL COMPONENTS

The primary aim of the soil and sediment control measures is to reduce soil erosion from areas stripped of vegetation during and after construction and to prevent silt from reaching the off-site drainage structures and downstream properties. As outlined in the Construction Sequencing schedule, the Sediment and Erosion Control Components are an integral component of the construction sequencing and will be implemented to control sedimentation and re-establish vegetation.

Planned erosion and sedimentation control practices during construction include the installation, inspection and maintenance of the inlet protection, soil stockpile areas, diversion swales and silt fencing. General land grading practices, including land stabilization and construction sequencing are also integrated into the Sediment and Erosion Control Plan. Dust control is not expected to be a problem due to the relatively limited area of exposure, the undisturbed perimeter of trees around the project area and the relatively short time of exposure. Should excessive dust be generated, it will be controlled by sprinkling.

All proposed soil erosion and sediment control practices have been designed in accordance with the following publications:

New York State standards and Specifications for Urban Erosion and Sediment Control, August 2005

New York State General Permit for Stormwater Discharges, GP-0-10-001 (General permit).


“Reducing the Impacts of Stormwater Runoff from New Development”, as published by the New York State Department of Environmental Conservation (NYSDEC), second edition, April, 1993.

The proposed soil erosion and sediment control devices include the planned erosion control practices outlined below. Maintenance procedures for each erosion control practice have also been outlined below.

SILT FENCE

Silt fence (geo-textile filter cloth) shall be placed in locations depicted on the approved plans. The purpose of the silt fence is to reduce the velocity of sediment laden stormwater from small drainage areas and to intercept the transported sediment load. In general, silt fence shall be used at the toe of slopes or intermediately within slopes where obvious channel concentration of stormwater is not present.

Maintenance

Silt fencing shall be inspected at a minimum of once per week and prior to and within 24 hours following a rain event ½” or greater. Inspections shall include ensuring that the fence material is tightly secured to the woven wire and the wire is secured to the wood posts. In addition, overlapping filter fabric shall be secured and the fabric shall be maintained a minimum of six (6) inches below grade. In the event that any “bulges” develop in the fence, that section of fence shall be replaced within 24 hours with new fence section. Any sediment build-up against the fence shall be removed within 24 hours and deposited on-site a minimum of 100 feet outside of any wetland or watercourse.

The installation of silt fencing will be maintained or replaced until the fencing is no longer necessary. Once the site is stabilized, all silt fences shall be removed. The immediate area occupied by the silt fence will be shaped to an acceptable grade and stabilized.

INLET PROTECTION

After catch basins and surface inlets have been installed, these drain inlets will receive stormwater from the roadways, driveways, and surrounding overland watersheds. In order to protect the receiving waters from sedimentation, the contractor shall install stone and block inlet protection as shown on the plans. Once installed, ¾ inch stone aggregate shall be installed around the perimeter of all catch basins and surface inlets as illustrated on the approved plans. This barrier will allow stormwater to be filtered prior to reaching the basin inlet grate.

The stone barrier should have a minimum height of 1 foot and a maximum height of 2 feet. Do not use mortar. The height should be limited to prevent


excess ponding and bypass flow. Recess the first course of blocks at least 2 inches below the crest opening of the storm drain for lateral support. Subsequent courses can be supported laterally if needed by placing a 2x4 inch wood stud through the block openings perpendicular to the course. The bottom row should have a few blocks oriented so flow can drain through the block to dewater the basin area. The stone should be placed just below the top of the blocks on slopes of 2:1 or flatter. Place hardware cloth of wire mesh with ½ inch openings over all block openings to hold stone in place.

As an optional design, the concrete blocks may be omitted and the entire structure constructed of stone, ringing the outlet (“doughnut”). The stone should be kept at a 3:1 slope toward the inlet to keep it from being washed into the inlet.

A level area 1 foot wide and four inches below the crest will further prevent wash. Stone on the slope toward the inlet should be at least 3 inches in size for stability and 1 inch or smaller away from the inlet to control flow rate. The elevation of the top of the stone crest must be maintained 6 inches lower than the ground elevation down slope from the inlet to ensure that all storm flows pass over the stone into the storm drain and not past the structure.

The barrier should be inspected after each rain event and repairs made within 24 hours. Remove sediment as necessary to provide for accurate storage volume for subsequent rains. Upon stabilization of contributing drainage area, remove all materials and any unstable soil and dispose of properly. Bring the disturbed area to proper grade, smooth, compact and stabilized in a manner appropriate to the site.

Maintenance

Stone aggregate shall be inspected weekly prior to and within 24 hours following a rain event ½” or greater. Care shall be taken to ensure that all stone aggregate are properly located and secure and do not become displaced. The stone aggregate shall be inspected for accumulated sediments and any accumulated sediment shall be removed from the device and deposited not less than 100 feet from wetland or watercourse.

TREE PROTECTION

All significant trees to be preserved located within the limits of disturbance and on the perimeter of the disturbance limits shall be protected from harm by erecting a 3’ high (minimum) snow fence completely surrounding the tree. Snow fence should extend to the drip-line of the tree to be preserved. Trees designated to be protected shall be identified during the staking of the limits of disturbance for each construction phase.

Maintenance


The snow fence shall be inspected daily to ensure that the perimeter of the fence remains at the drip-line of the tree to be preserved. Any damaged portions of the fence shall be repaired or replaced within 24 hours. Care shall also be taken to ensure that no construction equipment is driven or parked within the drip-line of the tree to be preserved.

SOIL/SHOT ROCK STOCKPILING

All soil and shot rock stripped from the construction area during grubbing and mass grading shall be stockpiled in locations shown on the plans, but in no case shall they be placed within 100’ of a wetland or watercourse. The stockpiled soils shall be re-used during finish-grading to provide a suitable growing medium for plant establishment. Soil stockpiles shall be protected from erosion by vegetating the stockpile with rapidly –germinating grass seed (during the May 1st – October 30th) planting season or covering the stockpile with tarpaulin the remainder of the year. Install silt fence around toe of slope.

Maintenance

Sediment controls (silt fence) surrounding the stockpiles shall be inspected according to the recommended maintenance outline above. All stockpiles shall be inspected for signs of erosion or problems with seed establishment weekly or tarpaulin and prior to and within 24 hours following a rain event ½” or greater.

GENERAL LAND GRADING

The intent of the Erosion & Sediment Control Plan is to control disturbed areas such that soils are protected from erosion by temporary methods and, ultimately, by permanent vegetation. Where practicable, all cut and fill slopes shall be kept to a maximum slope of 2:1. In the event that a slope must exceed a 2:1 slope, it will be stabilized with stone riprap. On fill slopes, all material will be placed in layers not to exceed 12 inches in depth and adequately compacted. Diversion swales shall be constructed on the top of all fill embankments to divert any overland flows away from the fill slopes.

SURFACE STABILIZATION

All disturbed areas will be protected from erosion with the use of vegetative measures (i.e., grass seed mix, sod) hydromulch netting or hay. When activities temporarily cease during construction, soil stockpiles and exposed soil should be stabilized by seed, mulch or other appropriate measures within 7 days after construction activity has ceased, or 24 hours prior to a rain event ½” or greater.

All seeded areas will be re-seeded areas as necessary and mulched according to the site plan to maintain a vigorous, dense vegetative cover,


Erosion control barriers consisting of silt fencing shall be placed around exposed areas during construction. Where exposed areas are immediately uphill from a wetland or watercourse, the erosion control barrier will consist of silt fence or double rows of silt fencing. Any areas stripped of vegetation during construction will be vegetated and/or mulch, but in no case more than 14 days to prevent erosion of the exposed soils. And topsoil removed during construction will be temporarily stockpiled for future use in grading and landscaping.

As mentioned above, temporary vegetation will be established to protect exposed soil areas during construction. If growing conditions are not suitable for the temporary vegetation, mulch will be used to the satisfaction of the Village Engineer. Materials that may be used for mulching include straw, hay, salt hay, wood fiber, synthetic soil stabilizers, mulch netting, sod or hydromulch. In site areas where significant erosion potential exists (steep slopes) and where specifically directed by the Village ’s representative, Curlex Excelsior erosion control blankets (manufactured by American Excelsior, or approved equal) shall be installed. A permanent vegetative cover will be established upon completion of construction of those areas that have been brought to finish-grade and to remain undisturbed.

Temporary Stabilization (May 1st through October 31st planting season)

The following seeding application should be used depending on the time of year.

Spring/summer or early fall, seed the area with ryegrass (annual or perennial) at 30 lbs. per acre (Approximately 0.7 lb/1000 sq. ft. or use 1 lb/1000 sq. ft.).

Late fall or early winter, seed Certified ‘Aroostook’ winter rye (cereal rye) at 100 lbs. per acre (2.5 lbs/1000 sq. ft.).

Permanent Stabilization (May 1st through October 31st planting season)

1. Provide minimum of four (4) inches topsoil for all new lawn areas. Top dress all existing disturbed lawn areas with two (2) inches of topsoil.

2. Grass seed shall be evenly sown by mechanical seeder at a rate of 3.0-4.0 pounds per 1,000 square feet.

3. Fine rake, roll and water to a depth of one inch all seeded areas.

4. Apply air-dried hay or straw mulch to provide 90% coverage of surface (approximately 90 lbs. per 1,000 sf). Use small grain straw where mulch is maintained for more than three months


5. Contractor shall provide, at his own expense, protection against trespassing and other damage to lawn areas.

6. Lawn seed mix shall include:

a. General Recreation areas and lawns:

65% Kentucky Bluegrass blend 20% Perennial Rye 15% Fine fescue

Sod may be used as an alternate to seeding in select areas.

Slow release fertilizers will be applied by hand to horticultural plantings as part of regular horticultural maintenance program and shall be limited to a single spring application.

CONSTRUCTION PRACTICES TO MINIMIZE STORMWATER CONTAMINATION

General:

Adequate measures shall be taken to minimize contaminant particles arising from the discharge of solid materials, including building materials, grading operations, and the reclamation and placement of pavement, during project construction, including but not limited to:

Building materials, garbage, and debris shall be cleaned up daily and deposited into dumpsters, which will be periodically removed from the site and appropriately disposed of. All dumpsters and containers left on-site shall be covered and surrounded with silt fence in order to prevent contaminants from leaving the site. Silt fencing shall be inspected on a weekly basis.

Dump trucks hauling material from the construction site will be covered with a tarpaulin.

The paved street adjacent to the site entrance will be swept daily to remove excess mud, dirt, or rock tracked from the site.

Petroleum products will be stored in tightly sealed containers that are clearly labeled.

All vehicles on site will be monitored for leaks and receive regular preventive maintenance to reduce the chance of leakage.

All spills will be cleaned up immediately upon discovery. Spills large enough to reach the storm system will be reported to the National Response Center at 1-800-424-8802.


Materials and equipment necessary for spill cleanup will be kept in the temporary material storage trailer onsite. Equipment will include, but not be limited to, brooms, dust pans, mops, rags, gloves, goggles, kitty litter, sand, saw dust, and plastic and metal trash containers.

All paint containers and curing compounds will be tightly sealed and stored when not required for use. Excess paint will not be discharged to the storm system, but will be properly disposed according to the manufacturer’s instructions.

Sanitary waste will be collected from portable units a minimum of two times a week to avoid overfilling. All sanitary waste units shall be surrounded by silt fence to prevent contaminants from leaving the site. Silt fencing shall be inspected on a weekly basis.

Any asphalt substances used on-site will be applied according to the manufacturer's recommendation.

Fertilizers will be stored in a covered shed and partially used bags will be transferred to a sealable bin to avoid spills and will be applied only in the minimum amounts recommended by the manufacturer and worked into the soil to limit exposure to stormwater.

No disturbed area shall be left un-stabilized for longer than 14 days during the growing season.

When erosion is likely to be a problem, grubbing operations shall be scheduled and performed such that grading operations and permanent erosion control features can follow within 24 hours thereafter.

As work progresses, patch seeding shall be done as required on areas previously treated to maintain or establish protective cover.

Drainage pipes and swales/ditches shall generally be constructed in a sequence from outlet to inlet in order to stabilize outlet areas and ditches before water is directed to the new installation or any portion thereof, unless conditions unique to the location warrant an alternative method.

Spill Control & Spill Response:

For all hazardous materials stored on site, the manufacturer’s recommended methods for spill cleanup will be clearly posted. Site personnel will be made aware of the procedures, and the locations of the information and cleanup supplies.

Appropriate cleanup materials and equipment will be maintained by the Contractor in the materials storage area on-site. As appropriate, equipment and materials may include items such as booms, dust pans,


mops, rags, gloves, goggles, kitty litter, sand, sawdust, and plastic and metal trash containers specifically for clean up purposes.

All spills will be cleaned immediately after discovery and the materials disposed of properly.

The spill area will be kept well ventilated and personnel will wear appropriate protective clothing to prevent injury from contact with a hazardous substance.

After a spill, a report will be prepared describing the spill, what caused it, and the cleanup measures taken. The spill prevention plan will be adjusted to include measures to prevent this type of spill from reoccurring, as well as clean up instructions in the event of reoccurrences.

The Contractor’s site superintendent, responsible for day-to-day operations, will be the spill prevention and cleanup coordinator. The Contractor is responsible for ensuring that the site superintendent has had appropriate training for hazardous materials handling, spill management, and cleanup.

The Contractor’s site superintendent will be notified immediately when a spill or the threat of a spill is observed. The superintendent will assess the situation and determine the appropriate response.

If spills represent an imminent threat of escaping erosion and sediment controls and entering receiving waters, personnel will be directed to respond immediately to contain the release and notify the superintendent after the situation has been stabilized.

Spill kits containing appropriate materials and equipment for spill response and cleanup will be maintained by the Contractor at the site.

If oil sheen is observed on surface water, action will be taken immediately to remove the material causing the sheen. The Contractor will use appropriate materials to contain and absorb the spill. The source of the oil sheen will also be identified and removed or repaired as necessary to prevent further releases.

If a spill occurs the superintendent or the superintendent’s designee will be responsible for completing the spill reporting form and for reporting the spill to the contacts listed below.

Personnel with primary responsibility for spill response and clean up will receive training by the Contractor’s site superintendent or designee. The training must include identifying the location of the spill kits and other spill response equipment and the use of spill response materials.

Spill response equipment will be inspected and maintained as necessary to replace any materials used in spill response activities.

Spill Control Notification:


A reportable spill is a quantity of five (5) gallons or more or any spill of oil which: (1) violates water quality standards, ( 2) produces a ”sheen” on a surface water, or (3) causes a sludge or emulsion. This spill must be reported immediately to the agencies listed below.

Any spill of oil or hazardous substance to waters of the state must be reported immediately by telephone to the following agencies:

911 – Police, Fire and EMS

Mamaroneck Fire Department 146 Palmer Ave, Mamaroneck NY, 10543 Phone: (914) 825-8777

NYS Department of Environmental Conservation (NYSDEC) Spill Reporting Hotline (1800) 457–7362

National Response Center: (1800) 424-8802

Local Emergency Planning Committee (LEPC) Westchester County Office of Emergency Management 200 Bradhurst Avenue Hawthorne, NY 10532 (914) 864–5450

Westchester County Department of Health (WCDOH) Spill Reporting Hotline (914) 813-5000

U.S. Environmental Protection Agency (USEPA) EPCRA Information Hotline (1800) 535–0202

U.S. Department of Labor and Occupational Safety and Health Administration (OSHA) Tarrytown, NY (914) 524–7510

STORMWATER MANAGEMENT FACILITIES MAINTENANCE PROGRAM

The following maintenance plan has been developed to maintain the proper function of all drainage and erosion and sediment control facilities:

Erosion & Sediment Control Maintenance:

During the construction of the project, the site erosion and sediment control measures as well as basin embankments and outlet structures will be inspected by the project superintendent once a week and/or within 24 hours following a rainstorm ½” or greater. Any repairs required shall be performed in


a timely manner. All sediment removal and/or repairs will be followed within 24 hours by re-vegetation. Remove sediment and correct erosion by re-seed eroded areas and gullies within 7 days.

General Stormwater Facilities Maintenance (Storm Sewer, Catch Basins/Drain Inlets, Manholes, Pre-treatment Device and Subsurface Infiltration System)

All stormwater facilities shall be inspected immediately after completion of construction, and then monthly for the first three (3) months following the completion of the Project. Within the first three (3) months, inspections shall immediately be performed following a large storm event (i.e. producing 1/2" (one-half inch) of rain or greater. Thereafter, these facilities shall be inspected as described as follows. Upon inspection, facilities shall be immediately maintained and/or cleaned as may be required. Any site areas exhibiting soil erosion of any kind shall be immediately restored and stabilized with vegetation, mulch or stone, depending on the area to be stabilized.

Upon each inspection, all visible debris including, but not limited to, twigs, leaf and forest litter shall be removed from the swales, overflow discharge points and frames and grates of drainage structures.

Sumps − Catch Basin/Drain Inlets

All catch basin/drain inlets with sumps have been designed to trap sediment prior to its transport to the infiltration practice and, ultimately, downstream. These sumps will require periodic inspection and maintenance to ensure that adequate depth is maintained within the sumps.

All sumps shall be inspected once per month for the first three (3) months (after drainage system has been put into service). Thereafter, all sumps shall be inspected every four (4) months. The Owner, or their duly authorized representative, shall take measurements of the sump depth.

If sediment has accumulated to 1/2 (one-half) the depth of the sump, all sediment shall be removed from the sump. Sediments can be removed with hand-labor or with a vacuum truck.

The use of road salt shall be minimized for maintenance of roadway and driveway areas.

Subsurface Attenuation/Exfiltration Gallery:


The subsurface infiltration chambers shall be inspected immediately after construction. Thereafter, the exfiltration galleries shall be inspected every six (6) months (Spring and Fall) for excess sediment accumulation. During dry weather conditions, when sediment has accumulated to an average depth exceeding 3" (three inches), the gallery shall be water jetted clean, and all accumulated sediments shall be vacuumed out or removed manually. A stadia rod may be inserted to determine the depth of the sediment.

CONCLUSION

By fully infiltrating the runoff from both proposed houses along with reducing the total runoff from the lot, the proposed stormwater management plan meets all the requirements set forth by the Village of Mamaroneck. Design modification requirements that may occur during the approval process will be performed and submitted to the Village for review.


Appendix A

EXTREME PRECIPITATION TABLE


Appendix B

WATERSHED MAPS

5' Wood Fence

6' Wood Stockade Fence

4' Alum. Fence

4' Chain Link Fence

Irreg. Wire Fence

Row Of Arborvitae

Row Of Forsythia Irreg. Along Line

Driveway

Exist. Concrete Curb

Exist. Asphalt Curb

Exist. 8" Sewer

Exist. Gas Main

Exist. Water Main

T: 914-909-0420F: 914-560-2086

WS-E

5' Wood Fence

6' Wood Stockade Fence

4' Alum. Fence

4' Chain Link Fence

Irreg. Wire Fence

Row Of Arborvitae

Row Of Forsythia Irreg. Along Line

Driveway

Exist. Concrete Curb

Exist. Asphalt Curb

Exist. 8" Sewer

Exist. Gas Main

Exist. Water Main

T: 914-909-0420F: 914-560-2086

WS-P


Appendix C

PRE-DEVELOPMENT ANALYSIS OF THE

1-, 10-, 25-, 50- AND 100-YEAR STORM FREQUENCIES

1A

Watershed 1A

1B

Watershed 1B

2A

Watershed 2A

2B

Watershed 2B

DP-1

DP-1

DP-1A

DP-1A_End of Proposed Driveway

DP-1B

DP-1B_Henry Ave - SW Corner of Lot

DP-2

DP-2_NW Corner of Lot

RR 1A CURB

RR-1A Off-Site Overland Along Curb

RR 1A DRIVE

RR-1A Off-Site Overland Exiting

Driveway

RR 1B

RR-1B Off-Site Overland

3B.1

6-Cultec C-100HD Rechargers

Routing Diagram for Existing_Subdivision_2015-10-09Prepared by Hudson Engineering & Consulting, P.C., Printed 12/10/2015HydroCAD® 10.00-12 s/n 02549 © 2014 HydroCAD Software Solutions LLC

Subcat Reach Pond Link

Existing_Subdivision_2015-10-09 Printed 12/10/2015Prepared by Hudson Engineering & Consulting, P.C.

Page 2HydroCAD® 10.00-12 s/n 02549 © 2014 HydroCAD Software Solutions LLC

Area Listing (all nodes)

Area(acres)

CN Description(subcatchment-numbers)

0.351 79 50-75% Grass cover, Fair, HSG C (1A, 1B, 2A)0.006 98 Driveway (1A)0.024 98 Existing Roof (2B)0.018 98 Proposed Roof (2B)0.003 98 Steps (1B)

0.402 81 TOTAL AREA



Soil Listing (all nodes)

Area(acres)

SoilGroup

SubcatchmentNumbers

0.000 HSG A0.000 HSG B0.351 HSG C 1A, 1B, 2A0.000 HSG D0.051 Other 1A, 1B, 2B

0.402 TOTAL AREA



Ground Covers (all nodes)

HSG-A(acres)

HSG-B(acres)

HSG-C(acres)

HSG-D(acres)

Other(acres)

Total(acres)

GroundCover

SubcatchmentNumbers

0.000 0.000 0.351 0.000 0.000 0.351 50-75% Grass cover, Fair 1A, 1B, 2A

0.000 0.000 0.000 0.000 0.006 0.006 Driveway 1A0.000 0.000 0.000 0.000 0.024 0.024 Existing Roof 2B0.000 0.000 0.000 0.000 0.018 0.018 Proposed Roof 2B0.000 0.000 0.000 0.000 0.003 0.003 Steps 1B

0.000 0.000 0.351 0.000 0.051 0.402 TOTAL AREA

Type III 24-hr 1-Year Rainfall=2.86"Existing_Subdivision_2015-10-09 Printed 12/10/2015Prepared by Hudson Engineering & Consulting, P.C.


Time span=0.00-60.00 hrs, dt=0.01 hrs, 6001 pointsRunoff by SCS TR-20 method, UH=SCS, Weighted-CN

Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method

Runoff Area=4,316 sf 6.19% Impervious Runoff Depth=1.15"Subcatchment 1A: Watershed 1A Flow Length=121' Tc=4.0 min CN=80 Runoff=0.14 cfs 0.009 af

Runoff Area=4,574 sf 2.71% Impervious Runoff Depth=1.15"Subcatchment 1B: Watershed 1B Flow Length=99' Slope=0.0901 '/' Tc=5.1 min CN=80 Runoff=0.14 cfs 0.010 af


Runoff Area=1,829 sf 100.00% Impervious Runoff Depth=2.63"Subcatchment 2B: Watershed 2B Tc=1.0 min CN=98 Runoff=0.14 cfs 0.009 af

Inflow=0.28 cfs 0.019 afReach DP-1: DP-1 Outflow=0.28 cfs 0.019 af

Inflow=0.14 cfs 0.009 afReach DP-1A: DP-1A_End of Proposed Driveway Outflow=0.14 cfs 0.009 af

Inflow=0.14 cfs 0.010 afReach DP-1B: DP-1B_Henry Ave - SW Corner of Lot Outflow=0.14 cfs 0.010 af

Inflow=0.19 cfs 0.014 afReach DP-2: DP-2_NW Corner of Lot Outflow=0.19 cfs 0.014 af

Avg. Flow Depth=0.05' Max Vel=2.49 fps Inflow=0.14 cfs 0.009 afReach RR 1A CURB: RR-1A Off-Site n=0.013 L=93.0' S=0.0722 '/' Capacity=11.83 cfs Outflow=0.14 cfs 0.009 af

Avg. Flow Depth=0.02' Max Vel=2.59 fps Inflow=0.14 cfs 0.009 afReach RR 1A DRIVE: RR-1A Off-Site n=0.013 L=12.0' S=0.1775 '/' Capacity=5.28 cfs Outflow=0.14 cfs 0.009 af

Avg. Flow Depth=0.03' Max Vel=1.47 fps Inflow=0.14 cfs 0.010 afReach RR 1B: RR-1B Off-Site Overlandn=0.013 L=12.0' S=0.0342 '/' Capacity=2.32 cfs Outflow=0.14 cfs 0.010 af

Peak Elev=69.62' Storage=6 cf Inflow=0.14 cfs 0.009 afPond 3B.1: 6-Cultec C-100HD Rechargers Discarded=0.11 cfs 0.009 af Primary=0.00 cfs 0.000 af Outflow=0.11 cfs 0.009 af

Total Runoff Area = 0.402 ac Runoff Volume = 0.043 af Average Runoff Depth = 1.28"87.31% Pervious = 0.351 ac 12.69% Impervious = 0.051 ac



Summary for Subcatchment 1A: Watershed 1A

Runoff = 0.14 cfs @ 12.06 hrs, Volume= 0.009 af, Depth= 1.15"

Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-60.00 hrs, dt= 0.01 hrsType III 24-hr 1-Year Rainfall=2.86"

Area (sf) CN Description4,049 79 50-75% Grass cover, Fair, HSG C

* 267 98 Driveway4,316 80 Weighted Average4,049 93.81% Pervious Area

267 6.19% Impervious Area

Tc Length Slope Velocity Capacity Description(min) (feet) (ft/ft) (ft/sec) (cfs)

3.5 63 0.0946 0.30 Sheet Flow, A->BGrass: Short n= 0.150 P2= 3.50"

0.4 35 0.0437 1.46 Shallow Concentrated Flow, B->CShort Grass Pasture Kv= 7.0 fps

0.1 23 0.1178 6.97 Shallow Concentrated Flow, C->DP-1Paved Kv= 20.3 fps

4.0 121 Total

Summary for Subcatchment 1B: Watershed 1B




* 124 98 Steps4,574 80 Weighted Average4,450 97.29% Pervious Area



5.1 99 0.0901 0.32 Sheet Flow, A->DP-2Grass: Short n= 0.150 P2= 3.50"






Area (sf) CN Description6,781 79 50-75% Grass cover, Fair, HSG C6,781 100.00% Pervious Area



0.6 83 0.1247 2.47 Shallow Concentrated Flow, B->DP-3Short Grass Pasture Kv= 7.0 fps

6.2 182 Total




Area (sf) CN Description* 1,027 98 Existing Roof* 802 98 Proposed Roof

1,829 98 Weighted Average1,829 100.00% Impervious Area


1.0 Direct Entry,

Summary for Reach DP-1: DP-1

Inflow Area = 0.204 ac, 4.40% Impervious, Inflow Depth = 1.15" for 1-Year eventInflow = 0.28 cfs @ 12.08 hrs, Volume= 0.019 afOutflow = 0.28 cfs @ 12.08 hrs, Volume= 0.019 af, Atten= 0%, Lag= 0.0 min

Routing by Stor-Ind+Trans method, Time Span= 0.00-60.00 hrs, dt= 0.01 hrs

Summary for Reach DP-1A: DP-1A_End of Proposed Driveway





Summary for Reach DP-1B: DP-1B_Henry Ave - SW Corner of Lot



Summary for Reach DP-2: DP-2_NW Corner of Lot



Summary for Reach RR 1A CURB: RR-1A Off-Site Overland Along Curb


Routing by Stor-Ind+Trans method, Time Span= 0.00-60.00 hrs, dt= 0.01 hrsMax. Velocity= 2.49 fps, Min. Travel Time= 0.6 minAvg. Velocity = 1.07 fps, Avg. Travel Time= 1.4 min

Peak Storage= 5 cf @ 12.07 hrsAverage Depth at Peak Storage= 0.05'Bank-Full Depth= 0.25' Flow Area= 1.6 sf, Capacity= 11.83 cfs

0.00' x 0.25' deep channel, n= 0.013 Asphalt, smoothSide Slope Z-value= 50.0 0.0 '/' Top Width= 12.50'Length= 93.0' Slope= 0.0722 '/'Inlet Invert= 67.79', Outlet Invert= 61.08'

‡

Summary for Reach RR 1A DRIVE: RR-1A Off-Site Overland Exiting Driveway






10.00' x 0.10' deep Parabolic Channel, n= 0.013 Asphalt, smoothLength= 12.0' Slope= 0.1775 '/'Inlet Invert= 69.92', Outlet Invert= 67.79'

‡

Summary for Reach RR 1B: RR-1B Off-Site Overland





‡

Summary for Pond 3B.1: 6-Cultec C-100HD Rechargers

Inflow Area = 0.042 ac,100.00% Impervious, Inflow Depth = 2.63" for 1-Year eventInflow = 0.14 cfs @ 12.01 hrs, Volume= 0.009 afOutflow = 0.11 cfs @ 11.98 hrs, Volume= 0.009 af, Atten= 21%, Lag= 0.0 minDiscarded = 0.11 cfs @ 11.98 hrs, Volume= 0.009 afPrimary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af



Routing by Stor-Ind method, Time Span= 0.00-60.00 hrs, dt= 0.01 hrsPeak Elev= 69.62' @ 12.06 hrs Surf.Area= 168 sf Storage= 6 cf

Plug-Flow detention time= 0.2 min calculated for 0.009 af (100% of inflow)Center-of-Mass det. time= 0.2 min ( 754.4 - 754.2 )

Volume Invert Avail.Storage Storage Description#1 69.50' 76 cf Custom Stage Data (Prismatic) Listed below (Recalc) x 6

336 cf Overall - 84 cf Embedded = 252 cf x 30.0% Voids#2 70.50' 84 cf Cultec C-100HD x 6 Inside #1

Effective Size= 32.1"W x 12.0"H => 1.86 sf x 7.50'L = 14.0 cfOverall Size= 36.0"W x 12.5"H x 8.00'L with 0.50' Overlap

159 cf Total Available Storage

Elevation Surf.Area Inc.Store Cum.Store(feet) (sq-ft) (cubic-feet) (cubic-feet)69.50 28 0 071.50 28 56 56

Device Routing Invert Outlet Devices#1 Discarded 69.50' 28.000 in/hr Exfiltration over Surface area #2 Primary 71.49' 6.0" Vert. Orifice/Grate C= 0.600

Discarded OutFlow Max=0.11 cfs @ 11.98 hrs HW=69.53' (Free Discharge)1=Exfiltration (Exfiltration Controls 0.11 cfs)

Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=69.50' (Free Discharge)2=Orifice/Grate ( Controls 0.00 cfs)













4.0 121 Total


















6.2 182 Total







1.0 Direct Entry,




















‡








‡






‡






Plug-Flow detention time= (not calculated: outflow precedes inflow)Center-of-Mass det. time= 1.5 min ( 744.5 - 743.0 )





















4.0 121 Total


















6.2 182 Total







1.0 Direct Entry,




















‡








‡






‡




Appendix D

POST-DEVELOPMENT ANALYSIS OF THE

1-, 10-, 25-, 50 AND 100-YEAR STORM FREQUENCIES

1A

Watershed 1A

1B

Watershed 1B

1C

Watershed 1C

2A

Watershed 2A

2B

Watershed 2B

4R

6" HDPE

6R

6" HDPE

7R

6" HDPE

8R

6" HDPE

9R

6" HDPE

DP-1

DP-1_Henry Ave - SW Corner of Lot

DP-2

DP-2_NW Corner of Lot

RR 1A CURB

Off-Site Overland Along Curb

RR 1A DRIVE

Off-Site Overland Exiting Driveway

1B.1

60 L.F. 24" HDPE PIPE

1C.1

60 L.F. 24" HDPE PIPE

2B.1

6-Cultec C-100HD Rechargers

Routing Diagram for Proposed_Subdivision_2015-10-09Prepared by Hudson Engineering & Consulting, P.C., Printed 12/10/2015HydroCAD® 10.00-12 s/n 02549 © 2014 HydroCAD Software Solutions LLC

Subcat Reach Pond Link

Proposed_Subdivision_2015-10-09 Printed 12/10/2015Prepared by Hudson Engineering & Consulting, P.C.


Area Listing (all nodes)

Area(acres)

CN Description(subcatchment-numbers)

0.263 79 50-75% Grass cover, Fair, HSG C (1A, 2A)0.009 98 Exist Driveway & Steps (1A)0.024 98 Existing Roof (2B)0.006 98 Patio Area (2A)0.019 98 Proposed Driveway and Path (1A)0.063 98 Proposed House (1B, 1C)0.018 98 Proposed Roof (2B)

0.402 86 TOTAL AREA



Soil Listing (all nodes)

Area(acres)

SoilGroup

SubcatchmentNumbers

0.000 HSG A0.000 HSG B0.263 HSG C 1A, 2A0.000 HSG D0.139 Other 1A, 1B, 1C, 2A, 2B

0.402 TOTAL AREA



Ground Covers (all nodes)

HSG-A(acres)

HSG-B(acres)

HSG-C(acres)

HSG-D(acres)

Other(acres)

Total(acres)

GroundCover

SubcatchmentNumbers

0.000 0.000 0.263 0.000 0.000 0.263 50-75% Grass cover, Fair 1A, 2A

0.000 0.000 0.000 0.000 0.009 0.009 Exist Driveway & Steps 1A0.000 0.000 0.000 0.000 0.024 0.024 Existing Roof 2B0.000 0.000 0.000 0.000 0.006 0.006 Patio Area 2A0.000 0.000 0.000 0.000 0.019 0.019 Proposed Driveway and Path 1A0.000 0.000 0.000 0.000 0.063 0.063 Proposed House 1B,

1C0.000 0.000 0.000 0.000 0.018 0.018 Proposed Roof 2B

0.000 0.000 0.263 0.000 0.139 0.402 TOTAL AREA

Type III 24-hr 1-Year Rainfall=2.86"Proposed_Subdivision_2015-10-09 Printed 12/10/2015Prepared by Hudson Engineering & Consulting, P.C.






Runoff Area=1,375 sf 100.00% Impervious Runoff Depth=2.63"Subcatchment 1C: Watershed 1C Tc=1.0 min CN=98 Runoff=0.10 cfs 0.007 af



Avg. Flow Depth=0.04' Max Vel=3.78 fps Inflow=0.02 cfs 0.007 afReach 4R: 6" HDPE6.0" Round Pipe n=0.013 L=6.0' S=0.1667 '/' Capacity=2.29 cfs Outflow=0.02 cfs 0.007 af





Inflow=0.28 cfs 0.030 afReach DP-1: DP-1_Henry Ave - SW Corner of Lot Outflow=0.28 cfs 0.030 af


Avg. Flow Depth=0.06' Max Vel=2.88 fps Inflow=0.24 cfs 0.016 afReach RR 1A CURB: Off-Site Overland n=0.013 L=94.0' S=0.0745 '/' Capacity=12.02 cfs Outflow=0.24 cfs 0.016 af

Avg. Flow Depth=0.03' Max Vel=2.63 fps Inflow=0.24 cfs 0.016 afReach RR 1A DRIVE: Off-Site Overland n=0.013 L=16.0' S=0.1156 '/' Capacity=4.26 cfs Outflow=0.24 cfs 0.016 af

Peak Elev=75.27' Storage=75 cf Inflow=0.10 cfs 0.007 afPond 1B.1: 60 L.F. 24" HDPE PIPE Primary=0.02 cfs 0.007 af Secondary=0.00 cfs 0.000 af Outflow=0.02 cfs 0.007 af

Peak Elev=63.28' Storage=75 cf Inflow=0.10 cfs 0.007 afPond 1C.1: 60 L.F. 24" HDPE PIPE Primary=0.02 cfs 0.007 af Secondary=0.00 cfs 0.000 af Outflow=0.02 cfs 0.007 af







* 391 98 Exist Driveway & Steps* 828 98 Proposed Driveway and Path

6,431 83 Weighted Average5,212 81.04% Pervious Area1,219 18.96% Impervious Area



0.1 45 0.1136 6.84 Shallow Concentrated Flow, B->DP-1Paved Kv= 20.3 fps

5.2 125 Total




Area (sf) CN Description* 1,375 98 Proposed House

1,375 100.00% Impervious Area


1.0 Direct Entry,

Summary for Subcatchment 1C: Watershed 1C








1.0 Direct Entry,





* 247 98 Patio Area6,490 80 Weighted Average6,243 96.19% Pervious Area



8.7 99 0.0603 0.19 Sheet Flow, A->BGrass: Dense n= 0.240 P2= 3.50"


9.4 193 Total







1.0 Direct Entry,

Summary for Reach 4R: 6" HDPE

Inflow Area = 0.032 ac,100.00% Impervious, Inflow Depth = 2.63" for 1-Year eventInflow = 0.02 cfs @ 12.35 hrs, Volume= 0.007 afOutflow = 0.02 cfs @ 12.36 hrs, Volume= 0.007 af, Atten= 0%, Lag= 0.0 min





6.0" Round Pipen= 0.013 Corrugated PE, smooth interiorLength= 6.0' Slope= 0.1667 '/'Inlet Invert= 74.43', Outlet Invert= 73.43'













Summary for Reach DP-1: DP-1_Henry Ave - SW Corner of Lot






Summary for Reach RR 1A CURB: Off-Site Overland Along Curb







‡

Summary for Reach RR 1A DRIVE: Off-Site Overland Exiting Driveway





‡

Summary for Pond 1B.1: 60 L.F. 24" HDPE PIPE

Inflow Area = 0.032 ac,100.00% Impervious, Inflow Depth = 2.63" for 1-Year eventInflow = 0.10 cfs @ 12.01 hrs, Volume= 0.007 afOutflow = 0.02 cfs @ 12.35 hrs, Volume= 0.007 af, Atten= 77%, Lag= 20.4 minPrimary = 0.02 cfs @ 12.35 hrs, Volume= 0.007 afSecondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af





Volume Invert Avail.Storage Storage Description#1 74.43' 188 cf 24.0" Round Pipe Storage

L= 60.0'

Device Routing Invert Outlet Devices#1 Secondary 75.93' 6.0" Vert. Orifice/Grate C= 0.600 #2 Primary 74.43' 1.0" Vert. Orifice/Grate C= 0.600

Primary OutFlow Max=0.02 cfs @ 12.35 hrs HW=75.27' (Free Discharge)2=Orifice/Grate (Orifice Controls 0.02 cfs @ 4.30 fps)

Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=74.43' (Free Discharge)1=Orifice/Grate ( Controls 0.00 cfs)

Summary for Pond 1C.1: 60 L.F. 24" HDPE PIPE





L= 60.0'



Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=62.44' (Free Discharge)1=Orifice/Grate ( Controls 0.00 cfs)












5.2 125 Total







1.0 Direct Entry,









1.0 Direct Entry,










9.4 193 Total







1.0 Direct Entry,








‡






‡








L= 60.0'



Secondary OutFlow Max=0.01 cfs @ 12.32 hrs HW=76.00' (Free Discharge)1=Orifice/Grate (Orifice Controls 0.01 cfs @ 0.88 fps)






L= 60.0'















5.2 125 Total







1.0 Direct Entry,









1.0 Direct Entry,










9.4 193 Total







1.0 Direct Entry,








‡






‡








L= 60.0'









L= 60.0'





Appendix E

USDA SOIL MAP & REPORT

Drainage Class—Westchester County, New York(12161 Henry Ave)

Natural ResourcesConservation Service

Web Soil SurveyNational Cooperative Soil Survey

10/29/2014Page 1 of 4

4534

600

4534

700

4534

800

4534

900

4535

000

4535

100

4535

200

4535

300

4535

400

4535

500

4534

600

4534

700

4534

800

4534

900

4535

000

4535

100

4535

200

4535

300

4535

400

4535

500

606600 606700 606800 606900 607000 607100 607200 607300 607400 607500 607600 607700 607800 607900 608000 608100

606700 606800 606900 607000 607100 607200 607300 607400 607500 607600 607700 607800 607900 608000 608100

40° 57' 50'' N73

° 4

4' 0

'' W40° 57' 50'' N

73° 4

2' 5

3'' W

40° 57' 17'' N

73° 4

4' 0

'' W

40° 57' 17'' N

73° 4

2' 5

3'' W

N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS840 300 600 1200 1800

Feet0 100 200 400 600

MetersMap Scale: 1:7,110 if printed on A landscape (11" x 8.5") sheet.

MAP LEGEND MAP INFORMATION

Area of Interest (AOI)Area of Interest (AOI)

SoilsSoil Rating Polygons

Excessively drained

Somewhat excessivelydrainedWell drained

Moderately well drained

Somewhat poorly drained

Poorly drained

Very poorly drained

Subaqueous

Not rated or not available

Soil Rating LinesExcessively drained




Poorly drained

Very poorly drained

Subaqueous


Soil Rating Points

Excessively drained




Poorly drained

Very poorly drained

Subaqueous


Water FeaturesStreams and Canals

TransportationRails

Interstate Highways

US Routes

Major Roads

Local Roads

BackgroundAerial Photography

The soil surveys that comprise your AOI were mapped at 1:12,000.

Please rely on the bar scale on each map sheet for mapmeasurements.

Source of Map: Natural Resources Conservation ServiceWeb Soil Survey URL: http://websoilsurvey.nrcs.usda.govCoordinate System: Web Mercator (EPSG:3857)

Maps from the Web Soil Survey are based on the Web Mercatorprojection, which preserves direction and shape but distortsdistance and area. A projection that preserves area, such as theAlbers equal-area conic projection, should be used if more accuratecalculations of distance or area are required.

This product is generated from the USDA-NRCS certified data as ofthe version date(s) listed below.

Soil Survey Area: Westchester County, New YorkSurvey Area Data: Version 10, Sep 17, 2014

Soil map units are labeled (as space allows) for map scales 1:50,000or larger.

Date(s) aerial images were photographed: Mar 26, 2011—Apr 16,2012

The orthophoto or other base map on which the soil lines werecompiled and digitized probably differs from the backgroundimagery displayed on these maps. As a result, some minor shiftingof map unit boundaries may be evident.

Drainage Class—Westchester County, New York(12161 Henry Ave)



10/29/2014Page 2 of 4

Drainage Class

Drainage Class— Summary by Map Unit — Westchester County, New York (NY119)

Map unit symbol Map unit name Rating Acres in AOI Percent of AOI

CrC Charlton-Chatfieldcomplex, rolling, veryrocky

Well drained 6.7 2.8%

SuA Sutton loam, 0 to 3percent slopes

Moderately well drained 8.5 3.5%

SuB Sutton loam, 3 to 8percent slopes

Moderately well drained 0.1 0.0%

Uc Udorthents, wetsubstratum

Somewhat poorlydrained

0.4 0.2%

Uf Urban land 0.8 0.4%

UhB Urban land-Charltoncomplex, 2 to 8percent slopes

45.5 18.9%

UhC Urban land-Charltoncomplex, 8 to 15percent slopes

12.4 5.2%

UlC Urban land-Charlton-Chatfield complex,rolling, very rocky

44.5 18.5%

UmC Urban land-Chatfield-Rock outcrop complex,rolling

90.4 37.5%

UwB Urban land-Woodbridgecomplex, 2 to 8percent slopes

31.6 13.1%

Totals for Area of Interest 241.0 100.0%

Description

"Drainage class (natural)" refers to the frequency and duration of wet periods underconditions similar to those under which the soil formed. Alterations of the waterregime by human activities, either through drainage or irrigation, are not aconsideration unless they have significantly changed the morphology of the soil.Seven classes of natural soil drainage are recognized-excessively drained,somewhat excessively drained, well drained, moderately well drained, somewhatpoorly drained, poorly drained, and very poorly drained. These classes are definedin the "Soil Survey Manual."

Rating Options

Aggregation Method: Dominant Condition

Component Percent Cutoff: None Specified

Drainage Class—Westchester County, New York 12161 Henry Ave



10/29/2014Page 3 of 4

Tie-break Rule: Higher

Drainage Class—Westchester County, New York 12161 Henry Ave



10/29/2014Page 4 of 4


Appendix F

PERCOLATION & DEEP HOLE TEST DATA


Appendix G

CONTRACTOR’S CERTIFICATION


Appendix H

STORMWATER MANAGEMENT CONSTRUCTION CHECKLIST

stormwater pollution prevention plan 1216 …€¦ · · 2016-02-12stormwater pollution...

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