HomeMy WebLinkAboutStormwater Report & Operation Manaual - No HydroCADMassachusetts Department of Environmental Protection
Bureau of Resource Protection - Wetlands Program
Checklist for Stormwater Report
A. Introduction
Important: when A Stormwater Report must be submitted with the Notice of Intent permit application to document
filling out forms compliance with the Stormwater Management Standards. The following checklist is NOT a substitute for
on the computer, (which h
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key to move your here as a tool to help the applicant organize their Stormwater Management documentation for their
cursor- do not Report and for the reviewer to assess this information in a consistent format. As noted in the Checklist,
use the return the Stormwater Report must contain the engineering computations and supporting information set forth in
key. Volume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared and
d certified by a Registered Professional Engineer (RPE) licensed in the Commonwealth.
The Stormwater Report must include:
• The Stormwater Checklist completed and stamped by a Registered Professional Engineer (see
page 2) that certifies that the Stormwater Report contains all required submittals.[ This Checklist
is to be used as the cover for the completed Stormwater Report.
• Applicant/Project Name
• Project Address
• Name of Firm and Registered Professional Engineer that prepared the Report
• Long -Term Pollution Prevention Plan required by Standards 4-6
• Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan required
by Standard 82
• Operation and Maintenance Plan required by Standard 9
In addition to all plans and supporting information, the Stormwater Report must include a brief narrative
describing stormwater management practices, including environmentally sensitive site design and LID
techniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans are
required to show existing and proposed conditions, identify all wetland resource areas, NRCS soil types,
critical areas, Land Uses with Higher Potential Pollutant Loads (LUHPPL), and any areas on the site
where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for
both existing and proposed conditions at a scale that enables verification of supporting calculations.
As noted in the Checklist, the Stormwater Management Report shall document compliance with each of
the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The
soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the
Massachusetts Stormwater Handbook.
To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report
Checklist by checking the box to indicate that the specified information has been included in the
Stormwater Report. If any of the information specified in the checklist has not been submitted, the
applicant must provide an explanation. The completed Stormwater Report Checklist and Certification
must be submitted with the Stormwater Report.
' The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included in
the Stormwater Report, the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to
the post -construction best management practices.
P For some complex projects, it may not be possible to include the Construction Period Erosion and Sedimentation Control Plan in
the Stormwater Report. In that event, the issuing authority has the discretion to issue an Order of Conditions that approves the
project and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan
before commencing any land disturbance activity on the site.
8807.Stormwater Check List • 04/01/08 Stormwater Report Checklist • Page 1 of 8
Massachusetts Department of Environmental Protection
Bureau of Resource Protection - Wetlands Program
Checklist for Stormwater Report
B. Stormwater Checklist and Certification
The following checklist is intended to serve as a guide for applicants as to the elements that ordinarily
need to be addressed in a complete Stormwater Report. The checklist is also intended to provide
conservation commissions and other reviewing authorities with a summary of the components necessary
for a comprehensive Stormwater Report that addresses the ten Stormwater Standards.
Note: Because stormwater requirements vary from project to project, it is possible that a complete
Stormwater Report may not include information on some of the subjects specified in the Checklist. If it is
determined that a specific item does not apply to the project under review, please note that the item is not
applicable (N.A.) and provide the reasons for that determination.
A complete checklist must include the Certification set forth below signed by the Registered Professional
Engineer who prepared the Stormwater Report.
Registered Professional Engineer's Certification
I have reviewed the Stormwater Report, including the soil evaluation, computations, Long-term Pollution
Prevention Plan, the Construction Period Erosion and Sedimentation Control Plan (if included), the Long-
term Post -Construction Operation and Maintenance Plan, the Illicit Discharge Compliance Statement (if
included) and the plans showing the stormwater management system, and have determined that they
have been prepared in accordance with the requirements of the Stormwater Management Standards as
further elaborated by the Massachusetts Stormwater Handbook. I have also determined that the
information presented in the Stormwater Checklist is accurate and that the information presented in the
Stormwater Report accurately reflects conditions at the site as of the date of this permit application.
Registered Professional Engineer Block and Signature
SH OF MgSs�S
JOHN M. GU
O'REILLY
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Checklist
Project Type: Is the application for new development, redevelopment, or a mix of new and
redevelopment?
® New development
❑ Redevelopment
❑ Mix of New Development and Redevelopment
8807.Stormwater Check List • 04/01/08 Stormwater Report Checklist • Page 2 of 8
Massachusetts Department of Environmental Protection
Bureau of Resource Protection - Wetlands Program
Checklist for Stormwater Report
Checklist (continued)
LID Measures: Stormwater Standards require LID measures to be considered. Document what
environmentally sensitive design and LID Techniques were considered during the planning and design of
the project:
® No disturbance to any Wetland Resource Areas
® Site Design Practices (e.g. clustered development, reduced frontage setbacks)
❑ Reduced Impervious Area (Redevelopment Only)
❑ Minimizing disturbance to existing trees and shrubs
❑ LID Site Design Credit Requested:
❑ Credit 1
❑ Credit 2
❑ Credit 3
❑ Use of "country drainage" versus curb and gutter conveyance and pipe
❑ Bioretention Cells (includes Rain Gardens)
❑ Constructed Stormwater Wetlands (includes Gravel Wetlands designs)
❑ Treebox Filter
® Water Quality Swale
❑ Grass Channel
❑ Green Roof
Deep sump catch basins, dry water quality swales & subsurface leaching
® Other (describe): galleys
Standard 1: No New Untreated Discharges
® No new untreated discharges
® Outlets have been designed so there is no erosion or scour to wetlands and waters of the
Commonwealth
® Supporting calculations specified in Volume 3 of the Massachusetts Stormwater Handbook included.
8807.Stormwater Check List • 04/01/08 Stormwater Report Checklist • Page 3 of 8
Massachusetts Department of Environmental Protection
Bureau of Resource Protection - Wetlands Program
Checklist for Stormwater Report
Checklist (continued)
Standard 2: Peak Rate Attenuation
❑ Standard 2 waiver requested because the project is located in land subject to coastal storm flowage
and stormwater discharge is to a wetland subject to coastal flooding.
❑ Evaluation provided to determine whether off-site flooding increases during the 100 -year 24-hour
storm.
® Calculations provided to show that post -development peak discharge rates do not exceed pre -
development rates for the 2 -year and 10 -year 24-hour storms. If evaluation shows that off-site
flooding increases during the 100 -year 24-hour storm, calculations are also provided to show that
post -development peak discharge rates do not exceed pre -development rates for the 100 -year 24-
hour storm.
Standard 3: Recharge
® Soil Analysis provided.
® Required Recharge Volume calculation provided.
❑ Required Recharge volume reduced through use of the LID site Design Credits.
® Sizing the infiltration, BMPs is based on the following method: Check the method used.
❑ Static ® Simple Dynamic ❑ Dynamic Field'
❑ Runoff from all impervious areas at the site discharging to the infiltration BMP.
® Runoff from all impervious areas at the site is not discharging to the infiltration BMP and calculations
are provided showing that the drainage area contributing runoff to the infiltration BMPs is sufficient to
generate the required recharge volume.
® Recharge BMPs have been sized to infiltrate the Required Recharge Volume.
❑ Recharge BMPs have been sized to infiltrate the Required Recharge Volume only to the maximum
extent practicable for the following reason:
❑ Site is comprised solely of C and D soils and/or bedrock at the land surface
❑ M.G.L. c. 21 E sites pursuant to 310 CMR 40.0000
❑ Solid Waste Landfill pursuant to 310 CMR 19.000
❑ Project is otherwise subject to Stormwater Management Standards only to the maximum extent
practicable.
® Calculations showing that the infiltration BMPs will drain in 72 hours are provided.
❑ Property includes a M.G.L. c. 21E site ora solid waste landfill and a mounding analysis is included.
1 80% TSS removal is required prior to discharge to infiltration BMP if Dynamic Field method is used.
8807.Slormwater Check List • 04/01/08 Stormwater Report Checklist • Page 4 of 8
Massachusetts Department of Environmental Protection
Bureau of Resource Protection - Wetlands Program
Checklist for Stormwater Report
Checklist (continued)
Standard 3: Recharge (continued)
❑ The infiltration BMP is used to attenuate peak flows during storms greater than or equal to the 10 -
year 24-hour storm and separation to seasonal high groundwater is less than 4 feet and a mounding
analysis is provided.
❑ Documentation is provided showing that infiltration BMPs do not adversely impact nearby wetland
resource areas.
Standard 4: Water Quality
The Long -Term Pollution Prevention Plan typically includes the following:
• Good housekeeping practices;
• Provisions for storing materials and waste products inside or under cover;
• Vehicle washing controls;
• Requirements for routine inspections and maintenance of stormwater BMPs;
• Spill prevention and response plans;
• Provisions for maintenance of lawns, gardens, and other landscaped areas;
• Requirements for storage and use of fertilizers, herbicides, and pesticides;
• Pet waste management provisions;
• Provisions for operation and management of septic systems;
• Provisions for solid waste management;
• Snow disposal and plowing plans relative to Wetland Resource Areas;
• Winter Road Salt and/or Sand Use and Storage restrictions;
• Street sweeping schedules;
• Provisions for prevention of illicit discharges to the stormwater management system;
• Documentation that Stormwater BMPs are designed to provide for shutdown and containment in the
event of a spill or discharges to or near critical areas or from LUHPPL;
• Training for staff or personnel involved with implementing Long -Term Pollution Prevention Plan;
• List of Emergency contacts for implementing Long -Term Pollution Prevention Plan.
® A Long -Term Pollution Prevention Plan is attached to Stormwater Report and is included as an
attachment to the Wetlands Notice of Intent.
® Treatment BMPs subject to the 44% TSS removal pretreatment requirement and the one inch rule for
calculating the water quality volume are included, and discharge:
❑ is within the Zone II or Interim Wellhead Protection Area
❑ is near or to other critical areas
® is within soils with a rapid infiltration rate (greater than 2.4 inches per hour)
❑ involves runoff from land uses with higher potential pollutant loads.
❑ The Required Water Quality Volume is reduced through use of the LID site Design Credits.
® Calculations documenting that the treatment train meets the 80% TSS removal requirement and, if
applicable, the 44% TSS removal pretreatment requirement, are provided.
8807.Slormwater Check List • 04/01/08 Stormwater Report Checklist • Page 5 of 8
Massachusetts Department of Environmental Protection
Bureau of Resource Protection - Wetlands Program
Checklist for Stormwater Report
Checklist (continued)
Standard 4: Water Quality (continued)
® The BMP is sized (and calculations provided) based on:
®
The %" or 1" Water Quality Volume or
❑ The equivalent flow rate associated with the Water Quality Volume and documentation is
provided showing that the BMP treats the required water quality volume.
❑ The applicant proposes to use proprietary BMPs, and documentation supporting use of proprietary
BMP and proposed TSS removal rate is provided. This documentation may be in the form of the
propriety BMP checklist found in Volume 2, Chapter 4 of the Massachusetts Stormwater Handbook
and submitting copies of the TARP Report, STEP Report, and/or other third party studies verifying
performance of the proprietary BMPs.
❑ A TMDL exists that indicates a need to reduce pollutants other than TSS and documentation showing
that the BMPs selected are consistent with the TMDL is provided.
Standard 5: Land Uses With Higher Potential Pollutant Loads (LUHPPLs)
❑ The NPDES Multi -Sector General Permit covers the land use and the Stormwater Pollution
Prevention Plan (SWPPP) has been included with the Stormwater Report.
® The NPDES Multi -Sector General Permit covers the land use and the SWPPP will be submitted prior
to the discharge of stormwater to the post -construction stormwater BMPs.
❑ The NPDES Multi -Sector General Permit does not cover the land use.
❑ LUHPPLs are located at the site and industry specific source control and pollution prevention
measures have been proposed to reduce or eliminate the exposure of LUHPPLs to rain, snow, snow
melt and runoff, and been included in the long term Pollution Prevention Plan.
❑ All exposure has been eliminated.
❑ All exposure has not been eliminated and all BMPs selected are on MassDEP LUHPPL list.
❑ The LUHPPL has the potential to generate runoff with moderate to higher concentrations of oil and
grease (e.g. all parking lots with >1000 vehicle trips per day) and the treatment train includes an oil
grit separator, a filtering bioretention area, a sand filter or equivalent.
Standard 6: Critical Areas
❑ The discharge is near or to a critical area and the treatment train includes only BMPs that MassDEP
has approved for stormwater discharges to or near that particular class of critical area.
❑ Critical areas and BMPs are identified in the Stormwater Report.
8807.Stormwater Check List • 04/01/08 Stormwater Report Checklist • Page 6 of 8
Massachusetts Department of Environmental Protection
Bureau of Resource Protection - Wetlands Program
Checklist for Stormwater Report
Checklist (continued)
Standard 7: Redevelopments and Other Projects Subject to the Standards only to the maximum
extent practicable
❑ The project is subject to the Stormwater Management Standards only to the maximum Extent
Practicable as a:
❑ Limited Project
❑ Small Residential Projects: 5-9 single family houses or 5-9 units in a multi -family development
provided there is no discharge that may potentially affect a critical area.
❑ Small Residential Projects: 2-4 single family houses or 2-4 units in a multi -family development
with a discharge to a critical area
❑ Marina and/or boatyard provided the hull painting, service and maintenance areas are protected
from exposure to rain, snow, snow melt and runoff
❑ Bike Path and/or Foot Path
❑ Redevelopment Project
❑ Redevelopment portion of mix of new and redevelopment.
❑ Certain standards are not fully met (Standard No. 1, 8, 9, and 10 must always be fully met) and an
explanation of why these standards are not met is contained in the Stormwater Report.
❑ The project involves redevelopment and a description of all measures that have been taken to
improve existing conditions is provided in the Stormwater Report. The redevelopment checklist found
in Volume 2 Chapter 3 of the Massachusetts Stormwater Handbook may be used to document that
the proposed stormwater management system (a) complies with Standards 2, 3 and the pretreatment
and structural BMP requirements of Standards 4-6 to the maximum extent practicable and (b)
improves existing conditions.
Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control
A Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan must include the
following information:
Narrative;
• Construction Period Operation and Maintenance Plan;
Names of Persons or Entity Responsible for Plan Compliance;
• Construction Period Pollution Prevention Measures;
Erosion and Sedimentation Control Plan Drawings;
• Detail drawings and specifications for erosion control BMPs, including sizing calculations;
• Vegetation Planning;
• Site Development Plan;
Construction Sequencing Plan;
Sequencing of Erosion and Sedimentation Controls;
• Operation and Maintenance of Erosion and Sedimentation Controls;
Inspection Schedule;
Maintenance Schedule;
• Inspection and Maintenance Log Form.
❑ A Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan containing
the information set forth above has been included in the Stormwater Report.
8807.Stormwater Check List • 04/01/08 Stormwater Report Checklist • Page 7 of 8
Massachusetts Department of Environmental Protection
Bureau of Resource Protection - Wetlands Program
Checklist for Stormwater Report
Checklist (continued)
Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control
(continued)
❑ The project is highly complex and information is included in the Stormwater Report that explains why
it is not possible to submit the Construction Period Pollution Prevention and Erosion and
Sedimentation Control Plan with the application. A Construction Period Pollution Prevention and
Erosion and Sedimentation Control has not been included in the Stormwater Report but will be
submitted before land disturbance begins.
❑ The project is not covered by a NPDES Construction General Permit
❑ The project is covered by a NPDES Construction General Permit and a copy of the SWPPP is in the
Stormwater Report.
® The project is covered by a NPDES Construction General Permit but no SWPPP been submitted.
The SWPPP will be submitted BEFORE land disturbance begins.
Standard 9: Operation and Maintenance Plan
® The Post Construction Operation and Maintenance Plan is included in the Stormwater Report and
includes the following information:
® Name of the stormwater management system owners;
® Party responsible for operation and maintenance;
® Schedule for implementation of routine and non -routine maintenance tasks;
® Plan showing the location of all stormwater BMPs maintenance access areas;
® Description and delineation of public safety features;
® Estimated operation and maintenance budget; and
® Operation and Maintenance Log Form.
❑ The responsible party is not the owner of the parcel where the BMP is located and the Stormwater
Report includes the following submissions:
❑ A copy of the legal instrument (deed, homeowner's association, utility trust or other legal entity)
that establishes the terms of and legal responsibility for the operation and maintenance of the
project site stormwater BMPs;
❑ A plan and easement deed that allows site access for the legal entity to operate and maintain
BMP functions.
Standard 10: Prohibition of Illicit Discharges
® The Long -Term Pollution Prevention Plan includes measures to prevent illicit discharges;
❑ An Illicit Discharge Compliance Statement is attached;
® NO Illicit Discharge Compliance Statement is attached but will be submitted prior to the discharge of
any stormwater to post -construction BMPs.
8807.Stormwaler Check List • 04/01/08 Stormwater Report Checklist • Page 8 of 8
J.M. OREILLY & ASSOCIATES, INC.
PROFESSIONAL ENGINEERING, LAND SURVEYING leg' ENVIRONMENTAL SERVICES
Site Development • Property Line • Subdivision • Sanitary • Land Court • Environmental Permitting
STORMWATER MANAGEMENT REPORT
AND
OPERATIONS & MAINTENANCE MANUAL
Miracle Way & Faith Road Cluster Subdivision
Assessors' Map 125, Parcel 39, Route 6A
Yarmouth, MA
FEBRUARY 18, 2022
PREPARED FOR:
THE DAVENPORT COMPANIES
20 NORTH MAIN STREET
SOUTH YARMOUTH, MA 02664
PREPARED BY:
J.M. O'REILLY & ASSOCIATES, INC.
1573 MAIN STREET
P.O. BOX 1773
BREWSTER, MA 02631
508-896-6601
1573 MAIN STREET, P.O. BOX 1773, BREWSTER, MA 02631 • PHONE: (508) 896-66oI • FAX: (508) 896-6602
W W W.JMOREILLYASSOC. COM
TABLE OF CONTENTS
1. Property Description and Information
2. Stormwater Management System Description
3. Massachusetts Stormwater Management Design Standards
4. Owner and Responsible Party
5. Schedule of Inspection and Maintenance of System
6. Schedule of Vegetation control for Roadway, Driveway & Sight Easement Areas
7. Long Term Lawn Care & Pollution Prevention Plan
8. Emergency Spill Cleanup Plan
9. APPENDICES
APPENDIX A — Checklist for Stormwater Report
APPENDIX B—TSS Removal Calculation Sheets
APPENDIX C - HydroCAD Modeling Reports
Page 2 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORMWATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
-
Lot Area: Area: 15.30 acres (666,507 sf+/-)
Parcel Improvements: The site is to be developed with a cluster subdivision which will contain (14)
The proposed post -development stormwater management plan consists of: A main stormwater system
that addresses the roadway, road shoulder and Swale areas; Secondary stormwater systems that address
driveway and front yard areas, and a system of drywells to handle roof runoff from the 14 proposed
dwellings.
The roadway will use Cape Cod berms to control and pitch stormwater toward a network of offline catch
basins (12 total). The catch basins then flow into a centralized conveyance system of pipe and manholes
that outlet into two dry water quality swales. The Upper Swale, adjacent to the intersection of Miracle
Way & Faith Road, routes overflow volume back into the conveyance system and into the Lower Swale,
adjacent to the intersection of Miracle Way and Route 6A. Any overflow from the Lower Swale is then
routed into a subsurface leaching galley. Landscaped areas and driveways are graded to direct stormwater
runoff into a series of smaller dry water quality swales. Roof runoff will be directed into subsurface
leaching facilities. Please see the Stormwater Contributory Area Pian for delineations of the site's
contributory areas.
Page 3 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORMWATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
residential lots and an Open Space lot. Each residential lot will be developed with
a (4) bedroom dwelling, for a total of (56) bedrooms.
Wetlands:
The parcel is abutted by a vegetated wetland at its Southwest corner. However
the wetland is greater than 250' from the closest area of the parcel that is
proposed for development. The wetland is on the far side of the 150' electrical
easement, and is not within the same watershed as any of the developed portion
of the parcel.
Soils:
The NRCS Soil Survey places the parcel within the soil unit 252C Sail, Carver
Coarse Sand, 8 to 15 percent. Medium to coarse sands were found in all
preliminary test holes conducted on the site.
Groundwater:
The USGS Cape Cod Groundwater Map places groundwater at approximately
elevation 8. With the parcel's topography ranging from EL=72 at the hilltop to
EL=28 at the low point near the West property line, the depth to groundwater to
range from 20 to 64 feet below the existing grade. Perched groundwater was
found at the bottom of test holes conducted within low areas. Maximum
elevation of perched water found at EL=23.
Zone II:
The parcel is not located within a Zone II Groundwater Recharge mapped area.
Topography:
The topography is hilly with a high point toward the back of the lot and the front
portion of the lot sloping down toward Route 6A.
Site Conditions:
The existing lot is vacant woodlands directly adjacent to Route 6A.
Stormwater Management
System Description:
The proposed post -development stormwater management plan consists of: A main stormwater system
that addresses the roadway, road shoulder and Swale areas; Secondary stormwater systems that address
driveway and front yard areas, and a system of drywells to handle roof runoff from the 14 proposed
dwellings.
The roadway will use Cape Cod berms to control and pitch stormwater toward a network of offline catch
basins (12 total). The catch basins then flow into a centralized conveyance system of pipe and manholes
that outlet into two dry water quality swales. The Upper Swale, adjacent to the intersection of Miracle
Way & Faith Road, routes overflow volume back into the conveyance system and into the Lower Swale,
adjacent to the intersection of Miracle Way and Route 6A. Any overflow from the Lower Swale is then
routed into a subsurface leaching galley. Landscaped areas and driveways are graded to direct stormwater
runoff into a series of smaller dry water quality swales. Roof runoff will be directed into subsurface
leaching facilities. Please see the Stormwater Contributory Area Pian for delineations of the site's
contributory areas.
Page 3 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORMWATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
As shown in the HydroCAD Modeling report, all of the main and secondary stormwater systems are
designed to collect and retain all runoff from their contributory areas for the 2, 10, 25 and 100 year storms.
There are no stormwater recharge systems included for driveways in flat areas that do not flow off-site,
as well as backyards and Open Space areas that do not slope toward developed portions of the lot. These
non -recharge areas are responsible for the entirety of the. Post -Development Peak Discharge rate, as all
recharge areas have been designed to retain all runoff for the 100 -Year Storm Event. Therefore, the Post -
Development 100 -year Storm Peak Discharge Rate relative to Pre -Development conditions has decreased
from 3.71 CFS to 2.41 CFS. The table below provides a comparison of the site -wide Pre- to Post -
Development peak discharge rate for each storm event.
Storm Event
Pre -Development Peak
Discharge Rate, cubic feet per
second (ft3/sec)
Post -Development Peak
Discharge Rate, cubic feet per
second (ft3/sec)
2 year
0
0
10 year
0.18
0.12
25 year
0.86
0.65
100 year
3.71
2.41
For HydroCAD modeling analysis of the stormwater systems, the following methods and assumptions
were used:
• Simple Dynamic
• Rawls Rate of 8.27 in/hr for sands within the subsoil layers for subsurface leaching galleys.
• Rawls Rate of 2.41 in/hr for the loamy sands in the upper soil layers for dry water quality
swales.
• Exfiltration has been assumed to occur along wetted surface area of bottom and walls/slopes.
Stormwater Management System Specifications by Contributory Area:
Main Stormwater System, M1 (Upper system):
• Roadway and shoulder runoff from the upper portion of Miracle Way & Faith Road directed
via grading and cape cod berms to a series of catch basins (6 total).
• Catch basins flow into a centralized conveyance system of pipe and manholes. Upper
conveyance system includes (2) outfall pipes flowing into the Upper dry water quality Swale.
• Landscaped and natural areas in the vicinity of the Swale will flow directly into the Swale.
• Swale sized so that it will fill to a maximum 18" water depth during storm events before
overflowing into (1) catch basin installed within the Swale with rim elevation 18" above
bottom of Swale. Overflow enters into the Lower conveyance system to flow into the Lower
dry water quality Swale (M2).
Main Stormwater System, M2 (Lower system):
• Roadway and shoulder runoff from the lower portion of Miracle Way directed via grading and
cape cod berms to a series of catch basins (6 total).
Page 4 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORMWATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
• Catch basins flow into a centralized conveyance system of pipe and manholes. Lower
conveyance system includes (2) outfall pipes flowing into the Lower dry water quality Swale.
• Landscaped and natural areas in the vicinity of the Swale will flow directly into the Swale.
• Swale sized so that it will fill to a maximum 18" water depth during storm events before
overflowing into (1) catch basin installed within the Swale with rim elevation 18" above
bottom Of Swale.
• Overflow enters into (1) 70' x 14' subsurface leaching facility consisting of (5) 6' diameter, 6'
deep leach pits spaced 14' on center, with stone around. Leaching facility has been sized to
retain 100 year storm runoff with no overflow.
Roof Runoff, M3 (per dwelling):
• Roof runoff for each dwelling will be directed via gutters and downspouts into two subsurface
leaching facilities, one on each side of the dwelling.
• Each leaching facility is 15.5' x 4.33' x 2.5', consisting of (2) Cultec Recharger 330XLHD Units
set in series (stoneless system).
• Roof runoff subsurface leaching facilities sized to retain 100 year storm runoff with no
overflow.
Secondary Stormwater Systems (Total of 7):
• Driveway and front/side yard runoff flows directly into several dry water quality swales sited
adjacent to driveway parking areas on residential lots.
• Swales have a maximum depth of 2'. Swales have all been sized to retain 100 year storm
runoff for their contributory areas, with no overflow.
Page 5 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORM WATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
Erosion Control Plan - Temporary Siltation Barrier & Slit Socks:
Prior to start of construction, a Stormwater Pollution Prevention Plan (SWPPP) will be prepared and a
Notice of Intent will be filed with the US EPA under the EPA NPDES Construction Stormwater program.
• The SWPPP & NO] shall address the erosion controls necessary prior to and during construction.
• The erosion controls shall include a row of staked 9 -inch straw wattles or an erosion (silt) fence
surrounding the entire area to be disturbed. Erosion controls shall be installed around all areas
of disturbance.
• Once the driveway stormwater systems are installed, deep sump catch basins shall be fitted with
filter fabric (silt socks) underneath the grates, to prevent silt and debris from clogging and/or
damaging the dry water quality swales and subsurface leaching facility.
• The erosion controls shall be monitored and corrected during the entire construction phase and
until the site has been stabilized with ground cover and the proposed landscape.
• Contractor shall be required to provide extra siltation controls in case a repair is needed to the
straw wattles and/or catch basin filter fabric.
Operational and maintenance plan is included herewith in order to address the long-term maintenance
of the stormwater systems.
Page 6 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORMWATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
Massachusetts Stormwater Management Design Standards:
The following is a description of how the proposed project meets the Massachusetts Stormwater
Handbook design standards.
Standard 1: No new untreated discharges:
This standard is met since there are no new untreated stormwater discharges proposed. See Standards 4-
6 calculations.
Standard 2 • Maintain Pre -development peak discharge rate:
This standard has been met. All stormwater management systems are sized such that the post
development peak discharge rate for the development site does not exceed the pre -development
discharge rate for the 2 year -24 hour; 10 year -24 hour; 25 year -24 hour; and 100 year -24 hour storm
events.
As shown in the HydroCAD Modeling report, all of the main and secondary stormwater systems are
designed to collect and retain all runoff from their contributory areas for the 2, 10, 25 and 100 year storms.
There are no stormwater recharge systems included for driveways in flat areas that do not flow off-site,
as well as backyards and Open Space areas that do not slope toward developed portions of the lot. These
non -recharge areas are responsible for the entirety of the Post -Development Peak Discharge rate, as all
recharge areas have been designed to retain all runoff for the 100 -Year Storm Event. Therefore, the Post -
Development 100 -year Storm Peak Discharge Rate relative to Pre -Development conditions has decreased
from 3.71 CFS to 2.41 CFS.
Standard 3: Groundwater Recharge:
This standard is met. The proposed stormwater management systems are sized so that the total recharge
volume provided exceeds the minimum groundwater recharge volume specified in the handbook and the
proposed stormwater recharge galleys will drawdown within 72 hours of a storm event. In accordance
with the MA Stormwater Manual, the required recharge volume factor (F) required across the impervious
area (A) is 0.6 inches per hour for hydraulic soil group A soils. Coarse Sand (Rawls Rate: 8.27 inches per
hour) has been used in the sizing of the stormwater recharge galleys. Refer to the HydroCAD Stormwater
Modeling Report in Appendix. The required recharge volume is calculated based on the total pavement
and roof areas on site.
Required Recharge Volume Rv = F x A = (0.6 in)(1 ft/12 in)(68,592 sf) = 3,430 cf (pavement and roofs)
Recharge Storage Provided (Subsurface leaching facilities) = 6,280 cf > 3,430 cf
The drawdown for the subsurface leaching facilities for the driveway/parking system and roof runoff
is 24 hours < 72 hour maximum allowance.
Standard 4: Water Quality.
This standard has been met. The roof runoff stormwater system will remove 80% of the annual load of
Total Suspended Solids (TSS) via subsurface leaching facilities. The main stormwater system serving the
roadway provides 78% TSS pretreatment removal of roadway runoff, and 96% total removal of roadway
runoff. TSS removal calculation tables for roadway and roof runoff are included in the Appendix. In
accordance with the MA Stormwater Manual, the required water quality depth (Dwq) across the
Page 7 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORM WATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
impervious area (A) is 1.0 inches per hour in areas containing soils with rapid infiltration rate greater than
2.4 in/hr. The required water quality volume is based on the total pavement area on site.
• Required Water Quality Volume Vwq = Dwq x A = (1.0 in)(1 ft/12 in)(50,560 sf) = 4,213 cf (pavement)
• Water Quality Storage Provided (Dry water quality swales) =12,111 cf > 4,213 cf
Standard 5: Land uses with higher potential pollutant loads:
This standard has been met. The proposed condominium units are residential buildings.
• Prior to construction a NPDES Construction General Permit for stormwater discharges associated
with construction activities will be completed and submitted.
• The Operation and Management Plan of the facility, as previously provided identifies the
operational procedures for the reduction and elimination of potential exposure to hazardous
materials.
Standard 6• Stormwater discharges within Zone 11 or Interim Wellhead protection area of a public water
supply and stormwater discharges near or to any critical area.
This standard has been met. The 1 inch Required Water Quality Volume for discharges within a
Groundwater Protection area has been met, see Standard 4 calculations.
Standard 7: Redevelopment.,
This standard is not applicable given the new development within the site meets the performance
standards of the Massachusetts Stormwater Design Standards.
Standard 8: Construction Erosion Control Plan:
The project is subject to the NPDES Construction General Permit. All applicable SWPPP and NOI submittals
shall be completed and approvals issued prior to any work being started for the proposed development
areas.
Standard 9• Long Term Operation and Maintenance Plan:
A long-term O&M plan has been submitted with this report, refer to Appendix. The Davenport Companies
will operate and maintain the stormwater systems.
Standard 1o: Illicit Discharges:
This standard is met since there are no illicit discharges at this site and no illicit discharges proposed.
Page 8 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORM WATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
Owner and Responsible Party
The owner and responsible party for Stormwater Pollution Control at Davenport Cluster Subdivision,
Yarmouth, MA
Owner:
The Davenport Companies
20 North Main Street
South Yarmouth, MA 02664
(508) 394-8800
Operator:
The Davenport Companies
20 North Main Street
South Yarmouth, MA 02664
(508) 394-8800
Page 9 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORM WATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
Schedule of Inspection and Maintenance of Stormwater Management Systems
1. The main stormwater systems serving the roadway requires regular attention in order to ensure
the effectiveness of the systems. It is recommended that the drainage systems be inspected
annually by a stormwater operation and maintenance professional in order to ensure that the
system is properly maintained. Any deterioration threatening the structural integrity of the
system shall immediately be repaired.
2. Paved areas shall be swept when necessary to remove debris and good housekeeping measures
should be implemented throughout the site in order to keep the roadway clean of debris.
3. The hooded, deep -sump catch basins shall be inspected at least two times per year; at the end of
foliage (approximately November 3011) and snow removal (approximately March 31st) seasons.
Sediments must be removed when the depth of deposits is greater than or equal to one half the
depth of the sumps. All deep -sump catch basins shall be cleaned out via vacuum truck or other
catch basin cleaning mechanism a minimum of once per year.
4. The subsurface leaching facility serving the roadway shall be inspected at least twice a year. Any
debris that may clog the system must be removed.
5. The two larger dry water quality swales serving the roadway shall be inspected and mowed
monthly. Inspect the grass side slopes and bottom for signs of erosion and formation of rills and
gullies. Remove accumulated trash, debris and silt as needed and at time of inspection.
6. The seven smaller dry water quality swales serving individual lot driveway and yard space shall be
the responsibility and shall be maintained by the owner of the lot the Swale is located on. Swales
shall be inspected and mowed monthly. Remove accumulated trash, debris and silt as needed and
at time of inspection.
Estimate of annual operation and maintenance budget for common areas = $ 5,000
Page 10 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORMWATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
Schedule of Vegetation control for Roadway, Driveway & Sight Easement Areas
1. Roadway shoulders: The grassed shoulders areas within the right of ways for Miracle Way and
Faith Road shall be mowed regularly during periods of growth, a minimum of once per month in
late Spring, Summer and early Fall. Any trash and debris, such as fallen tree limbs or leaves, shall
be removed on a regular basis. Shoulder areas shall be kept free of obstructions.
2. Sight Easements: The two sight easements areas adjacent to the entrance to Miracle Way must
remain free of vegetation or any other obstructions greater than 2.5' in height, in order to allow
sufficient visibility for drivers exiting Miracle Way onto Route 6A. Sight easements shall be mowed
regularly during periods of growth, a minimum of once per month in late Spring, Summer and
early Fall. Any trash and debris, such as fallen tree limbs or leaves, shall be removed on a regular
basis. Sight easement areas shall be kept free of obstructions. Tree limbs and any other vegetation
extending into the sight easement area from above shall be trimmed back to allow a 10' tall sight
easement 'window'.
3. Driveways: Each 10' wide paved driveway shall have surrounding vegetation trimmed back once
every two years so that sufficient space is allowed for Fire Safety vehicle access. The required
'window' that shall remain clear of vegetation is 14' wide, 12' tall, with vegetation removal.
extending a minimum of 2' beyond edge of pavement on either side of the driveways.
Estimate of annual operation and maintenance budget for common areas = $12,000
Page 11 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORMWATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
Long Term Lawn Care & Pollution Prevention Plan
Description of Pollutant Sources:
• Light vehicle traffic— residential development
• Lawn care products
Source Control Best Management Practices
• There shall be no storage of items or materials which will be subject to the weather.
• Good housekeeping measures shall be implemented throughout the site in orderto keep the road
and driveways clean of debris.
• Regularly sweep paved areas to remove debris and any other potential stormwater pollutants.
• The use of winter de-icing sand and salt materials shall be minimized to the maximum extent
practicable.
• Winter de-icing sand and salt materials shall be stored indoors.
• Snow storage shall be on paved surfaces.
• Immediately clean up any spillage on paved areas and dispose of wastes properly.
• Application of any fertilizer or pesticide products shall be applied only by a state -licensed
professional, using the product manufacturer's specified application rates.
• . Fertilizer and/or pesticide products may only be used on lawn or garden areas, and shall not be
used in any natural areas.
• Fertilizer shall not be applied immediately prior to or during a heavy rainfall event.
• Fertilizer shall not be applied between November 12 and the following March 31.
• Fertilizer shall not be applied, spilled or deposited on impervious surfaces or in a manner that
allows it to enter into storm drains.
• Fertilizer shall not be applied within 100 feet of any surface water or within the Zone I of a public
drinking water well
• Fertilizer containing phosphorus shall not be applied unless a soil test taken not more than three
years before the proposed fertilizer application indicates that additional phosphorus is needed
for growth of that turf, or unless establishing new turf or reestablishing or repairing turf after
substantial damage or land disturbance.
• A single application of fertilizer that contains nitrogen shall not exceed 1.0 pound of nitrogen per
1,000 square feet, shall consist of at least 20% slow-release nitrogen (SRN) fertilizer (NOTE: This
represents the minimum percentage: use of higher SRN content is generally preferable, especially
on sandy root zones, during stress and pre -stress periods, and when there are fewer annual
applications of nitrogen made to a lawn) and the annual rate shall not exceed 3.2 pounds of actual
nitrogen per thousand square feet. Single applications shall be done at intervals of no less than
four weeks until the annual maximum is reached.
Page 12 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORM WATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
Page 13 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORMWATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
Emergency Spill Cleanup Plan
1. The owner of the facility shall have a designated person with overall responsibility for spill
response cleanup.
2. In the event of a spill the following shall be notified:
A. Yarmouth Fire Department (508) 398-2212
(for a gasoline or hazardous material spill) 911
B. Massachusetts D.E.P. Emergency Response (800) 304-1133
C. Yarmouth Health Department (508) 398-2231 ext. 1240
3. Cleanup of spills shall begin immediately.
Page 14 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORM WATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
O Lo�,(j;) Perm
Condition
Inspector
Initials
Item Inspected
Date
Time
Good
Clean-out
Needed
Repair
Needed
Repaired
Date
O&M Log form records to be maintained by property manager for a minimum of three years
Page 15 of 15
DAVENPORT CLUSTER SUBDIVISION - MIRACLE WAY & FAITH ROAD STORMWATER MANAGEMENT REPORT
ASSESSORS' MAP 125, PARCEL 39, ROUTE 6A, YARMOUTH, MA FEBRUARY 18, 2022
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