HomeMy WebLinkAboutESS Group Letter to ConComm RE Stormwater Management Permit Application Dated 10-13-21�ess
group
October 13, 2021
Ms. Kelly Grant, Conservation Administrator
Town of Yarmouth
Conservation Commission
1146 Route 28
South Yarmouth, MA 02664
404 Wyman Street, Suite 375, Waltham, Massachusetts 02451 781.419.7696
10 Hemingway Drive, 2nd Floor, East Providence, Rhode Island 02915 401.434.5560
environmental consulting & engineering services
Re: Urology Associates of Gape Cod - Technical Stormwater Peer Review
125 & 133 Route 6A, Yarmouth Port
AP 121 Parcels 85 and 86 and AP & 122 Parcel 2
ESS Project No. Y011-000
Dear Ms, Grant,
ESS has completed a technical stormwater peer review of the Stormwater Management Permit Application
prepared by Down Cape Engineering, Inc. submitted to the Commission on September 1, 2021 and
provided to ESS on September 7, 2021. The goal of the review was to determine if the application is
technically complete and to evaluate compliance with the Yarmouth Stormwater Management Regulations,
effective July 1, 2021. ESS has determined that the application is neither complete nor in compliance with
the Stormwater Management Regulations as summarized below. Revised documents, including a detailed
response to the following comments, should be provided for further review.
The following PDF documents prepared by Down Cape Engineering were reviewed:
1. Site plans titled "Urology Associates of Cape Cod Site Construction Plans", revised 8/18/2021
2. "Drainage Calculations", dated 6/22/2021
3. "Construction Period Pollution and Erosion and Sedimentation Control Plan", dated 6/22/2021
4. "Stormwater Operations and Maintenance Plan", dated 6/23/2021
5. "Checklist for Stormwater Report", dated 9/1/2021
Yarmouth Conservation Commission Stormwater Management Regulations
2.04 Stormwater Management Site Plan
(1) ... The SMSP shall fully describe the project in drawings, and narrative.
The very brief narrative provided does not fully describe the project sufficiently to demonstrate compliance
as outlined throughout this review letter.
(g) The site's existing and proposed topography with contours at 1-foot intervals;
The site plans provide existing contours at 2-ft intervals only.
(h) The existing site hydrology;
A description of the existing site hydrology has not been provided.
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Ms. Kelly Grant,
October 13, 2021
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2.05. Stormwater Management Performance Standards
(1) The applicant must document in writing why LID strategies are not appropriate when not used to manage
stormwater.
Neither a description of Low Impact Development (LID) strategies proposed nor a justification of why LID
strategies are not appropriate have been provided.
(2) (b) Removal of sediment, leaf litter and other organic debris from impervious surfaces a minimum of
twice a year in the spring (after snowmelt) and fall (after leaf faf);
Item 2 of the Schedule Of Inspection And Maintenance and item 1 of the Source Control Best Management
Practices provided in the Stormwater Operations and Maintenance Plan lists parking area sweeping only
once per year.
(2) (d) Restrictions on the application of fertilizers...
A discussion of appropriate fertilizer application addressing the 7 items of this subsection has not been
provided.
(3) Stormwater management systems design shall be consistent with, or more stringent than, the
requirements of the 2008 Massachusetts Stormwater Handbook (as amended) with the following additional
requirements.-
(3) (a) Post -development peak discharge rates do not exceed pre -development peak discharge rates for
the 2, 10, 25, 50 and 100-year 24-hour storms. The 50-year post -development stormwater volume shall be
retained onsite through design of the stormwater management system to the maximum extent practicable.
The 100-year post -development stormwater volume shall be controlled onsite with no offsite discharge to
the maximum extent practicable. This Standard may be waived for discharges to land subject to coastal
storm flowage as defined in the Massachusetts Wetlands Protection Regulations at 310 CMR 10.04.
• Pre -development peak discharge rates have not been provided.
• The designer states on page 3 of the stormwater report checklist that the post -development runoff
from the 25-year design storm will be fully infiltrated. This statement is not documented in the
stormwater report.
• While it is indicated that the site discharges to land subject to coastal storm flowage on pages 3
and 4 of the stormwater report checklists, no supporting documentation or narrative description
have been provided.
• Calculations for the 50 and 100 year design storms are not provided.
An evaluation of the practicality of retaining the 50 and 100 year design storms on -site has not
been provided.
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Ms. Kelly Grant,
October 13, 2021
2.06. Erosion and Sediment Control Plan
(2) If a project requires a Storm water Pollution Prevention Plan (SWPPP) per the NPDES General Permit
for Storm Water Discharges From Construction Activities (and as amended), then the permittee is required
to submit a complete copy of the SWPPP. If the SWPPP meets the requirements of the General Permit, it
will be considered equivalent to the Erosion and Sediment Control Plan described in this section...
The proposed project appears to include greater than 1 acre of earth disturbance, therefore, the project will
require a SWPPP per the NPDES General Permit for Storm Water Discharges From Construction Activities.
A copy of the SWPPP was not provided.
(3) The design of erosion and sediment controls shalt meet the following requirements...
Documentation of the items listed under this standard has not been provided in the Construction Period
Pollution and Erosion and Sedimentation Control Plan or the site plans.
(4) Erosion and Sedimentation Control Plan Content...
An Erosion and Sedimentation Control Plan is not included in the plan set.
2.07. Operation and Maintenance Plan (post -construction)
(1)(c) The persoo(s) responsible for financing maintenance and emergency repairs;
Not provided
(1) (g) The signature(s) of the owner(s);
Not provided
Checklist for Stormwater Report
A. Introduction
• The checklist should be included in the stormwater report.
An existing conditions drainage area plan has not been provided.
• The proposed conditions drainage area plan provided is not "at a scale that enables verification of
supporting calculations". The plan is not clearly legible at the scale and resolution provided and
could not be reviewed for accuracy.
• The stormwater report does not document compliance with each of the Stormwater Management
Standards.
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Nis. Kelly Grant,
October 13, 2021
Standard 7: Redevelopments and Other Projects Subject to the Standards only to the maximum extent
practicable
This section of the checklist has not been completed nor has the standard been addressed in the
stormwater report.
Standard 6: Construction Period Pollution Prevention and Erosion and Sedimentation Control
• Erosion and Sedimentation Control Plan Drawings have not been provided.
The designer should justify why "the project is not covered by a NPDES Construction General
Permit". While not described, it appears that at least 1 acre of disturbance is proposed. If so, the
project would be covered by the construction general permit.
Standard 9: Operation and Maintenance Plan
A drawing showing the location of all stormwater BMPs maintenance access areas is not included in the
operation and maintenance plan.
Standard 10: Prohibition of Illicit Discharges
• The tong -Term Pollution Prevention Plan does not include measures to prevent illicit discharges.
• An Illicit Discharge Compliance Statement was not provided.
General Technical Review
The following general technical review comments should be addressed in addition to the technical
regulatory review comments provided above.
Drainage Calculations
The following should be provided for review:
1. The drainage area in acres or a square foot to acre conversion factor in the rational method
equation.
2. The Time of Concentration calculations and results. Illustrate the time of concentration flow path
on the drainage area plans.
3. The referenced Rainfall Intensity nomograph.
Stormwater Management Regulations Section
Standards.
4. The calculated flow rate to each catch basin.
The NOAA Atlas 14 IDI= curve is required by
2.05, Stormwater Management Performance
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Ms. Kelly Grant,
October 13, 2021
8. It is not clear where the southern end of the proposed 45 elevation contour ties in. This should be
clarified.
9. A spot elevation should be provided at the high point south of building no. 125.
10. All required stormwater structure setbacks should be shown.
11. Proposed symbols should be added to the legend on proposed conditions drawings.
12. Existing drainage structures and utilities to remain and existing drainage structures to be removed
should be noted on the plans. For example (not exhaustive), a catch basin and manhole shown on
the southern portion of the site on drawing C 100 is not shown on drawing C 301 and one existing
catch basin shown on drawing C 301 south of the proposed entrance is not labeled to be removed
or to remain.
13. Duplicate labels should be corrected. Two proposed catch basins labeled C133 and two leach pits
labeled LP5 were identified.
14. The leach pit south of the main building should be labeled to clarify if this existing leach pit is to
remain or replaced with a new leach pit.
15. It appears that Area Drains may be proposed along the existing roof drain line. These should be
described in the application documents. Pre-treatment of stormwater collected by the Area Drains
prior to discharge to the leach pit should be provided.
Findings
Based on these observations, ESS concludes that the application is not in compliance with the Stormwater
Management Regulations. Additional calculations, drawings, and documentation should be provided to
demonstrate compliance as described above. A detailed response to the review comments should be
provided along with a reference to the associated revision or supporting material.
Sincerely,
ESS GROUP, INC.
455;20�� "��
Jason M. Gold, P.E.
Manager, Civil/Site Engineering
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