HomeMy WebLinkAbout335 Salem St 240807_2nd_SWPeerReview Horsley Witten Group - Correspondence - 335 Salem Street 9/7/2024
August 7,2024
Ms. Jean Enright, Planning Director
Planning Department
Town of North Andover
120 Main Street
North Andover, Massachusetts 01845
Re: Second Stormwater Peer Review
Proposed Residential House
335 SalemStreet,North Andover, MA
Dear Ms. Enright and Board Members:
The Horsley Witten Group, Inc. (HW) is pleased to provide the North Andover Planning Board
with this letter report summarizing oursecondreview of the Watershed Special Permit
Application for the proposed residential houseat335 SalemStreetin North Andover, MA. The
plans were prepared bySullivan Engineering Group, LLCon behalf of JCE Property
Development, LLC(Applicant).The project proposes to construct a single-family house, with a
driveway, utilities, and stormwater infrastructure on an undeveloped lot. The stormwater
management for the proposed projectincludes a subsurfaceinfiltrationsystem to capture roof
runoff located behind the house within the 150-foot Non Disturbance zone.A portion of the
driveway will be constructed of permeable pavers with a driveway turn around area constructed
of turfstone paverswith grass.
Theresidential lot is located within the Watershed Protection District and was created after
October 24, 1994. The entire parcel is withinthe Non-Discharge Zone from the edge of a
bordering vegetated wetland (BVW)located to the west of the proposedhouse.The proposed
house is located outside of the 150-foot Non Disturbance Zone.The proposed limit of
disturbance is greater than 100 feet from the wetland resource area. In accordance with §195-
4.19B.(2)of the North Andover Zoning Bylaws, any surface or subsurface discharge of
stormwater within the Non-Discharge Buffer Zone is only allowed after a special permit has
beengranted by the North Andover Planning Board.A portion of the project area including a
change in topography is located within the 150-footNon-Disturbance Zone.
The following additional documents and plans were received by HWin response to our initial
peer review letter dated June 19, 2024:
Letter to North Andover Planning Board, regarding 335 Salem Street, North Andover,
Massachusetts Drainage Analysis, prepared bySullivan Engineering Group, LLC,
revised July 23, 2024 (55pages);
Long-Term Stormwater Operation & Maintenance Plan,335 SalemStreet, North
Andover, Massachusetts, prepared bySullivan Engineering Group, LLC(17pages);and
Plot Plan of Land,335 SalemStreet, North Andover, Massachusetts,prepared by
Sullivan Engineering Group, LLC, dated June 4, 2024, revised July 23, 2024(1 sheet).
Town of North Andover
August 7, 2024
Page 2of 6
Stormwater Management Design Peer Review
In accordance with the North Andover Zoning Bylaw §195-8.14. E. (8) A Stormwater
management plan is required for all site plan review applications. The stormwater management
plan shall be prepared in accordance with the latest version of the Massachusetts Stormwater
Handbook (MSH) and demonstrate full compliance with the Massachusetts Stormwater
Standards and the North Andover Stormwater Management and Erosion Control, Chapter 165
of the Town Bylaws. Chapter 165 further references Chapter 250. Stormwater Management and
Erosion Control.
HW offers the following comments concerning the stormwater management design. We have
used the Massachusetts Stormwater Standards as the basis for organizing our comments.
However, in instances where the additional criteria established in §250-27 of the North Andover
Code requires further recommendations; we have referenced these as well.
The following comments correlatewith our initial review letter dated June 19, 2024. Follow up
comments are provided in bold font.
1.Standard 1: No new stormwater conveyances (e.g., outfalls) may discharge untreated
stormwater directly to or cause erosion in wetlands or waters of the Commonwealth.
a.The Applicant has evaluated one discharge point from the project site. Under existing
conditions, the site property is modeled as one subcatchment area which flows overland
towards the west. There are no existing stormwater practices.
August 7, 2024: HW has no further comment.
b.The Applicant proposes to construct a subsurface chamber system to infiltrate runoff
from the proposed roof. The system overflows through the downspout openings. The site
is discharging greater than 100 feet from the BVW and should not cause erosion in
waters of the Commonwealth.
August 7, 2024:HW has no further comment.
The Applicant complies with Standard 1.
2.Standard 2: Stormwater management systems shall be designed so that post-development
peak discharge rates do not exceed pre-development peak discharge rates.
a.In accordance with §250-22 B. (6) a summary of pre-and post-development peak rates
and volumes of stormwater demonstrating no adverse impacts should be provided as
part of the narrative. The Applicant has provided the peak flows and the peak volumes
for the 2-year, 10-year, 25-year, and 100-year storm events in its Drainage Analysis
dated June 4, 2024.The table may need to be revised as the Applicant addresses the
following comments.
August 7, 2024:TheApplicant has revised the Table to correspond to the updated
HydroCAD model. The Applicant has reduced the peak flow and peak volumes
under all storm events analyzed. HW has no further comment.
b.In accordance with §250-22 B. (5) (a) a summary of proposed land area to be disturbed
and existing and proposed impervious area should be provided as part of the narrative.
HW recommends that the Applicant include the proposed land area to be disturbed and
the existing and proposed impervious area in the narrative.
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August 7, 2024:The Applicant has provided the requested informationas a table
on the Plot Plan.The entire existing 25,360 sf lot hasno impervious surfaces.The
limit of work appears to include approximately 13,000 sf. Under proposed
conditions the total impervious surfacewill be1,457 sf. The pervious paversand
turfstone driveway total 1,762 sf of permeable surface.HW has no further
comment.
c.The Applicant has modeled the entire existing surface area as Fair Grass coverin the
HydroCAD model.Furthermore, the Applicant has used Good Grass cover for more than
50% of the proposed conditions HydroCAD model. HW recommends that the Applicant
justify the use of “fair” under existing conditionsor revise the descriptionto “good”.
August 7, 2024:The Applicant has revised the surface condition modeled to be
“good” grass coverunder existing and proposed conditions.HW has no further
comment.
d.The Applicant has used a direct entry of 6 minutes for the times of concentrations (Tc).
HW recommends that the Applicant confirm that under existing conditions a minimum Tc
of 6 minutes is realistic.
August 7, 2024:The Applicant has revised the Tc values as requested. HW has no
further comment.
e.HW recommendsthat the Applicant clarify the proposed 196 contour and where it
crosses the proposed driveway.
August 7, 2024:The Applicant has clarified where the 196-contourelevation
crosses the driveway. HW has no further comment.
f.The Applicant has routed the roof subcatchment (2S) to the SubsurfaceInfiltration Field
(1P) in the post-development HydroCAD model. The Infiltration Field can overflow via
the downspout openings to Design Point 1. The Infiltration Field has been designed to
fully retain the 100-year storm event. No further action requested.
August 7, 2024:HW has no further comment.
g.The Applicant has used precipitation values equal to or greater than the values provided
by National Oceanic and Atmospheric Administration (NOAA) Atlas 14 for the 24-hour
storm events, as outlined in §250-23 E. (19). No further action required.
August 7, 2024:HW has no further comment.
The Applicant complies with Standard 2.
3.Standard 3 requires that the annual recharge from post-development shall approximate
annual recharge from pre-development conditions.
a.The Applicant has provided the requiredrecharge volume,and the drawdown is less
than 72 hours.HW has no further comment.
August 7, 2024:HW has no further comment.
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b.The separation from the bottom of the subsurface chamber system to the Estimated
Seasonal High Groundwater (ESHGW) is 2feet. HW recommends that the Applicant
providea mounding analysis in accordance with Volume 3, Chapter 1, page 28 of the
MSH.
August 7, 2024:The Applicant has provided the requested mounding analysis
calculation. HW has no further comment.
The Applicant complies with Standard 3.
4.Standard 4 requires that the stormwater system be designed to remove 80% Total
Suspended Solids (TSS) and to treat 1-inch of volume from the impervious area for water
quality.
a.The Applicant has provided a TSS worksheet that lists the subsurface chamber system
to provide 80% TSS removal. Per the §250-23 B (1) the Applicant is required to remove
90% of the average annual load of Total Suspended Solids (TSS) and 60% of the
average annual load of Total Phosphorus. This can be achieved by “retaining the volume
of runoff equivalent to, or greater than, one (1.0) inch multiplied by the total post-
construction impervious surface area on the new development site”. The Applicant has
provided water quality volume calculations demonstrating that the subsurface chamber
system retains the 1” storm. No further action required.
August 7, 2024:HW has no further comment.
The Applicant complies with Standard 4.
5.Standard 5 is related to projects with a Land Use of Higher Potential Pollutant Loads
(LUHPPL).
a.The project is not considered a LUHPPL. Standard 5 is not applicable.
August 7, 2024:Standard 5 is not applicable.
6.Standard 6 is related to projects with stormwater discharging into a critical area, a Zone II, or
an Interim Wellhead Protection Area of a public water supply.
a.The proposed work is located within the North Andover Watershed Protection District. In
accordance with §195-4.19. B. (4) All construction in the Watershed Protection District
shall comply with best management practices for erosion, siltation, and stormwater
control in order to preserve the purity of the groundwater and the lake; to maintain the
groundwater table; and to maintain the filtration and purification functions of the land. It
appears that the proposed construction complies with best management practices for
erosion, siltation, and stormwater control. The Applicant complies with Standard 6.
August 7, 2024:HW has no further comment.
The Applicant complies with Standard 6.
7.Standard 7 is related to projects considered Redevelopment.
a.The project is proposing to increase impervious area and is not considered a
redevelopment. Standard 7 is not applicable.
August 7, 2024:Standard 7 is not applicable.
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8.Standard 8 requires a plan to control construction related impacts including erosion,
sedimentation, or other pollutant sources.
a.It appears that the proposed erosion control barrier delineates a portion of the limit of
work (LOW). HW recommends that the Applicant add a separate LOW line that includes
the construction entrance and avoids any existing trees.Furthermore, HW recommends
that the Applicant clarify if the fieldstone wall along Salem Street will remain.
August 7, 2024:The Applicant has clarified where the fieldstone wall will remain,
where it will be removed, and where it will be reset. HW has no further comment.
b.HW recommends that the Applicant add a note stating, prior to any land disturbance
activities commencing on the site, the developer shall physically mark limits of no land
disturbance with tape, signs, or orange construction fence, so that workers can see the
areas to be protected. The physical markers shall be inspected daily.
August 7, 2024:The Applicant has added the note as suggested above. HW has no
further comment.
c.It appears that there may be trees located within the limit of work. HW recommends that
the Applicant provide protection for any trees located withinthe proposed limit of work.
August 7, 2024:The Applicant has indicated that three trees along the front field
stone wall will be outside of the limit of work and therefore protected. The plan
also illustrates fivetrees on the west side of the property that will be outside of
the limit of work. HW has no further comment.
The Applicant complies with Standard 8.
9.Standard 9 requires a Long-Term Operation and Maintenance (O & M) Plan to be provided.
a.The Applicant has provided a description of the inspection and maintenance tasks
required for the site in the Stormwater Report. HW recommends that the Applicant
provide an O&M Plan as a standalone document to be signed by the owner, which
includes the following:
(1)Stormwater management system owners;
(2)Parties responsible for operation and maintenance;
(3)An example maintenance log or checklist for each stormwater practice that the
homeowner can use to log maintenance;
(4)A schedule for implementing routine and non-routine maintenance tasks to be
undertaken after construction is complete;
(5)An estimated operations and maintenance budget; and
(6)A simple sketch that is drawn to scale and shows the location of all stormwater
practices requiring inspections and long-term maintenance.
August 7, 2024:The Applicant has provided a standalone O&M Plan with the
information requested. HW has no further comment.
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b.HW recommends that the Applicant mention the inspection ports for the subsurface
chamber system in the O&M Plan.
August 7, 2024:The Applicant has included the inspection ports as suggested.
HW has no further comment.
c.HW recommends including the manufacturers maintenance recommendations for the
subsurface chamber systems for the owner’s benefit in the O&M Plan.
August 7, 2024:The Applicant has included the manufacturers maintenance
recommendations as suggested. HW has no further comment.
The Applicant complies with Standard 9.
10.Standard 10 requires an Illicit Discharge Compliance Statement be provided.
a.The Applicant has provided a signed Illicit Discharge Compliance Statement in the
Stormwater Report. No further comment.
August 7, 2024:HW has no further comment.
The Applicant complies with Standard 10.
Conclusions
HW is satisfiedthat the Applicant has adequately addressed our comments.Please contact
Janet Bernardo at 508-833-6600 or at jbernardo@horsleywitten.com if you have any questions.
Sincerely,
HORSLEY WITTEN GROUP, INC.
Janet Carter Bernardo, P.E.
Principal
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