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Grant, Kelly
From:Aguiar, Nicholas
Sent:Friday, September 13, 2019 3:53 PM
To:Grant, Kelly
Subject:272 & 280 Union Street NOI Comments
Good Afternoon Kelly,
Please see below for my comments in regards to the NOI submission for 272 & 280 Union Street.
Drawing Set
Notes on drawing Sheets S2, S4, and S5 should indicate a 4’ sump for the deep sump catch basin to provide
consistency with Detail B on sheet S3.
Drawing sheet S5 needs to show all subcatchment areas in their entirety within the designated drawing space.
Drawing sheet S2, and Details D and F on sheet S3, should indicate a max slope of 3:1 for the Forebay and
Infiltration Basin side slopes.
Details D and F on sheet S3 should also specify the stabilization of the Forebay and Infiltration Basin side slopes
with vegetation.
The cross-section of the deep sump catch basin shown in Detail B on sheet S3 should show the pipe hood
specified within the notes of the accompanying plan view.
Stormwater Report/Design
There are several references to the area of the bituminous pad within the stormwater report which are
inconsistent with what is reported on drawing sheet S2.
The design engineer claims that the structure located on 280 Union Street is not located within the Miss
Thacher’s Pond watershed, while external survey data from the Cape Cod Commission indicates the contrary.
Please verify/substantiate claim.
There are several references to data/figures which are not included within the submission.
The applicant must submit all pertinent HydroCAD input and output data in order to substantiate model results
and associated conclusions.
The model scenario used to validate basin sizing is not in conformance with the Massachusetts Stormwater
Handbook. Consideration of sidewall exfiltration is not permitted. Drawdown calculation through stage-
discharge model is not permitted. Reference should be made to Volume 3, Chapter 1, Documenting Compliance
for compiling the necessary calculation package.
The operation and maintenance items outlined on drawing sheet 3 do not constitute a complete Long-Term
Operations and Maintenance Plan. Reference should be made to Volume 1, Chapter 1, Stormwater
Management Standards, Standard #9, for a list of the items which should, at a minimum, be included.
Maintenance items/schedules should be derived from the pertinent structural BMP specifications contained
within Volume 2, Chapter 2.
Some of the existing contours shown to the East of the proposed infiltration basin appear to allow unaccounted
for runoff to directly enter the basin and circumvent pretreatment.
Construction Period Pollution Prevention/Erosion and Sedimentation Control Plan
Construction period BMPs must be different from the BMPs used to manage stormwater post-construction.
BMPs which utilize infiltration are not designed to handle the concentrations of sediment which are typically
found in construction site stormwater runoff.
The Inspection and Maintenance Schedule provided lacks necessary specificity and detail required by the
Massachusetts Stormwater Handbook including: erosion control detail drawings, allowable sediment
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accumulation, and sediment disposal. Reference should be made to Volume 2, Chapter 1, Components of
Stormwater Management for more details.
Please feel free to contact me if you have any questions, or if you would like to discuss my comments further. I hope
that you have a good weekend.
Kind Regards,
Nick
Nicholas M. Aguiar, E.I.T.
M.S. Civil & Environmental Engineering
Town of Yarmouth
Civil Engineer
99 Buck Island Road
West Yarmouth, MA 02673
(508)398-2231, Ext. 1255
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