HomeMy WebLinkAboutPeer Review Response 11.29.2021
Engineers
Environmental Scientists
Software Developers
Landscape Architects
Planners
Surveyors
349 Main Street, Route 28, Unit D / West Yarmouth, MA 02673 / 508-778-8919
NOVEMBER 29, 2021 www.bscgroup.com
Town of Yarmouth Conservation Commission
Yarmouth Town Offices
1146 South Yarmouth, MA 02664
Attn: Kelly Grant, Conservation Administrator
RE: Stormwater Permit Application for Cape Cod Inflatable Park
BSC Project No. 48592.05
Dear Members of the Commission,
BSC Group, Inc. is pleased to submit revised site plans and the following responses to the November 17, 2021 peer review
by ESS Group, Inc. The BSC responses follow each comment in bold and italicized font.
2.04 Stormwater Management Site Plan
1(i). It appears that stormwater from a portion of the site may drain to an existing catch basin located within Route 28,
west of Parcel 79. The catch basin should be shown on the plans and described in the report.
The existing catch basin has been added to the plan set and is described in the report.
1(k). The seasonal high groundwater elevation has not been provided. The elevation should be shown on the plans in
relation to the bottom of the proposed Infiltration systems and the method for determining them should be documented
in the report.
BSC has done test pits at numerous sites along Route 28 in this section of West Yarmouth. At the nearby Cape
Point Hotel, BSC completed several witnessed test pits for the design of the septic systems on that property.
Those test holes consisted generally of medium sands, and no groundwater was encountered down to a depth
of 12’-8” in the deepest test hole. Given our knowledge of the local soils, and years of experience working in this
part of Yarmouth, we are confident that the proposed stormwater design for this site will meet requirements.
However, if the Commission feels it is necessary, BSC will perform test pits to confirm the soil type and depth
to groundwater.
1(l). The ground surface and corresponding Curve Numbers are not shown on the Drainage Area Maps. These should be
provided for comparison with the stormwater calculations.
The ground surface description and Curve Numbers (CN) have been added to the Drainage Area Maps.
1(m). Some of the pre- and post- construction stormwater paths are not correct as they are not perpendicular to the
contours.
The time of concentration flow paths have been modified, as requested.
The pre-construction drainage area boundaries do not appear to be correctly delineated. The 6S/4S boundary is not
drawn perpendicular to the contours. The northern portion of the 6S/5S boundary passes through the center of a valley
and the southern portion appears to arbitrarily follow a curb line. The boundaries should be corrected, or flow arrows and
spot elevations should be provided to support the current delineation.
349 Main Street, Route 28, Unit D / West Yarmouth, MA 02673 / 508-778-8919
The subcatchment area boundaries have been modified, as requested.
1(n). The size, slope, and materials of the proposed drainage lines have not been provided.
The size, slope and material of the proposed pipes have been added.
The separation distance to the bottom of the underground detention system to seasonal high groundwater and
bedrock/Impermeable layer have not been provided. A minimum of 2-foot separation distance to seasonal high ground
water is required by the Stormwater Handbook.
See response to Comment 1(k) above.
1(r). Pipe sizing calculations have not been provided.
Pipe sizing calculations are included with the provided.
Stormceptor sizing calculations have not been provided.
Stormceptor sizing calculations have now been provided.
A mounding analysis Is required If separation distance to seasonal high groundwater Is less than 4 feet.
A mounding analysis will be performed if 4’ of vertical separation from seasonal high groundwater cannot be
provided in the proposed design. A mounding analysis is not required if 4’ of separation is provided.
2.05 Stormwater Management Performance Standards
1. While this standard has not been addressed in the stormwater report, It was subsequently addressed In the November
12, 2021 letter.
The November 12, 2021 letter Is now part of the application materials. No further action is required.
2.(b) While addressed In the November 12, 2021 letter, this standard should be added to the Operations and Maintenance
Plan.
This standard has been added to the Operations and Maintenance Plan.
2.(d) While briefly addressed In the November 12, 2021 letter, the listed restrictions should be added to the Operation and
Maintenance Plan
The listed restrictions have been added to the Operations and Maintenance Plan.
3. A review of compliance with the Massachusetts Stormwater Handbook Is addressed In the "Checklist for Stormwater
Report" section below.
No action required.
2.06 Erosion and Sediment Control Plan
2. The Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan provided does not appear
to fully comply with all of the requirements of the NPDES Construction General Permit. However, the applicant has
Indicated that "the SWPPP will be submitted before land disturbance begins" under Standard 8 of the MassDEP Checklist
for Stormwater Report.
The SWPPP will be submitted before land disturbance begins (as required). No further action is required at this
time.
349 Main Street, Route 28, Unit D / West Yarmouth, MA 02673 / 508-778-8919
3.(e) Inlet protection should be provided for the catch basin located within Route 28 near the construction entrance.
Inlet protection and associated detail has been provided for the existing catch basin.
2.07 Operation and Maintenance Plan (post-construction)
1. While an O&M Plan Is Included in Section 5.0 of the Stormwater Report, It has not been prepared as a stand-alone
document.
No further action is required.
1.(a), 1.(b), 1.(c), 1.(g), & 1.(h) Not provided.
The name and address of the owner of the systems, person responsible for maintenance, finance, signature,
and operation and maintenance budget have been provided.
Stormwater Checklist and Certification
Standard 3: Recharge - As noted above, a mounding analysis or documentation the proposed minimum separation to the
seasonal high groundwater Is at least 4 feet should be provided.
See response to comment 1(k).
Standard 4: Water Quality- Documentation supporting the claimed TSS removal rate provided by the proprietary BMP
(Stormceptor) has not been provided.
The requested documentation is now included in the revised Stormwater Report.
Standard 9: Operation and Maintenance - Name of the stormwater management system owners, party responsible for
operation and maintenance, plan showing the location of all stormwater BMPs maintenance access areas, and estimated
operation and maintenance budget.
The requested information is now included in the Stormwqter Report.
Standard 10: Prohibition of Illicit Discharges - "No Illicit Discharges Compliance Statement is attached but will be
submitted prior to the discharge of any stormwater to post-construction BMPs" should be checked consistent with
Section 2.10 of the Stormwater Report.
This Item Is checked.
General Technical Review
Drainage Calculations 1. While NRCS soil type has been provided, documentation of compliance with the soil evaluation
procedure outlined In Volume 3 Chapter 1 of the Stormwater Handbook should be provided for review.
See response to comment 1(k). If test pits are required to be performed, BSC will complete the test pit logs on
the DEP Form 11.
Erosion and Sedimentation Control Plan 1. Section 4.2 states "the site Is currently an existing sand and gravel pit". This
apparent typographical error should be corrected.
The typographical error has been corrected.
349 Main Street, Route 28, Unit D / West Yarmouth, MA 02673 / 508-778-8919
2. Section 4.6 describes "loaming and seeding" and "completion of paved areas". The site plans and project narrative
should Indicate where the work Is proposed.
The site plan and project narrative Indicate the locations of loam and seed areas and paved areas.
3. Section 4.6 proposes the use of "hay mulch" to temporarily stabilize surfaces. This should be replaced with "straw
mulch" to prevent Introducing weed seeds to the project.
This change has been made, as requested.
Site Plans 1. Clarification should be provided on the plans to Indicate that the structures labeled "WQU" on sheet 4 are
represented by the detail labeled "Stormceptor STC 450i" on sheet 8.
The labels have been updated.
2. Observation wells should be provided to enable inspection of water levels within each infiltration system as required
by the Stormwater Handbook.
Observation wells (or Inspections ports) have been provided for each of the systems.
3. Pavement details are provided on Sheet 8. The site plans and project narrative should Indicate where proposed
pavement Is proposed. The corresponding surfaces should be Indicated In the stormwater calculations.
The location of the proposed pavement is indicated on the site plans, the project narrative, and has been
updated in the stormwater calculations.
Sincerely,
BSC Group, Inc.
Brian G. Yergatian, PE, LEED AP
Senior Project Manager/Senior Associate