HomeMy WebLinkAboutResponse to 1st Stormwater Peer Review - - 364 JOHNSON STREET Horsley Wiften Group
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July 7, 2025
Ms. Jean Enright, Planning Director
Planning Department
Town of North Andover
120 Main Street
North Andover, Massachusetts 01845
Re: Initial Stormwater Peer Review
Proposed Improvements— 364 Johnson Street
North Andover, Massachusetts
Dear Ms. Enright and Board Members:
The Horsley Witten Group, Inc. (HW) is pleased to provide the North Andover Planning Board with
this report summarizing our initial review of the Watershed Special Permit Application for the
proposed improvements at 364 Johnson Street in North Andover, MA. The plans were prepared by
John J. McDonnell, MSCE, PE, PLS on behalf of Gergory and Melissa Buitkus (Applicant). The
project proposes a 376 square foot (sf) expansion of the existing two-story dwelling within the 325-
foot "Non-Discharge Buffer Zone" to Bordering Vegetated Wetlands (BVW). The stormwater
management for the proposed improvements includes a 160-gallon mini drywell and a subsurface
system for infiltration on the east side of the existing building. The existing footprint of the house is
890 sf. The proposed footprint of the expanded house is 1,266 sf. A total increase of approximately
376± sf of impervious surface area is proposed within the 26,571-sf parcel. It appears that the total
land disturbance will be less than 43,560 sf.
The residential lot is located within the Watershed Protection District and was created in 1964,
before October 24, 1994. The lot is located within the urbanized area and the area of disturbance is
less than 1 acre. The project is proposed within the 325-foot Non-Discharge Buffer Zone from the
edge of a BVW. The BVW is located along the western side of the roadway at 365 Johnson Street.
The closest point of the proposed expansion to the BVW is approximately 260 feet. The proposed
limit of disturbance is greater than 100 feet from the wetland resource area. In accordance with
§195-4.19 B.(2)(a) 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 been
granted by the North Andover Planning Board.
The following documents and plans were received by HW:
• Watershed Special Permit Application, 364 Johnson Street, North Andover, MA, prepared by
John J. McDonnell, MSCE, PE, PLS, dated May 20, 2025 (12 pages);
• Plot Plan of Land, 364 Johnson Street, North Andover, MA, prepared by John J. McDonnell,
MSCE, PE, PLS, dated June 13, 2025 (1 sheet); and
• Stormwater Management Report, 364 Johnson Street, North Andover, MA, prepared by John
J. McDonnell, MSCE, PE, PLS, dated June 25, 2025 (15 sheets).
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Stormwater Management Design Peer Review
n 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.
HW has the following comments and recommendations regarding the proposed stormwater
management design.
1. The Applicant has provided a Plot Plan of Land. HW recommends adding a north arrow to
the plan and providing a legible signed and stamped copy of the plan to the Planning Board.
RESPONSE:
Detail included in revised plan.
2. The Applicant has called out erosion controls and notes on the Plan. A callout for a silt sock
is noted but it is unclear where it is located. It is also unclear where stockpiling onsite will
occur and the limits of the disturbance for work. HW recommends showing the limits of
disturbance and locations of silt sock in addition to where the stockpiles will be located
during construction. HW recommends that the erosion controls be added along the tree line
parallel to the eastern property line to protect the wetland from sediment transported by
construction equipment onto the existing driveway. HW further recommends that erosion
controls be extended along the tree line to the north of the house to protect the area from
sediment transported by construction equipment using the proposed construction access.
RESPONSE:
Silt Sock fixed in revised plan. Limits of disturbance included in revised plan.
Stockpile locations included in revised plan. I note however, that it will be physically
impossible for surface water that crossed over or around this Project site to make its
way to the wetlands. The land contours are such that the surface water that crosses
this Project Site will not flow in the direction of the wetlands.
3. HW recommends that the Applicant callout a defined construction access point to the work
onsite. HW recommends that the Applicant consider construction matting or other measures
to minimize the tracking of sediment offsite per§250-25.E.(13) of the North Andover Code.
RESPONSE:
Construction Access Point Included in revised plan. Construction matting will be
provided.
4. HW recommends that the Applicant provides a path and mechanism to divert
uncontaminated water around the disturbed areas per§250.25.E.(l 0) and §250-26.A.(27) of
the North Andover Code.
RESPONSE:
Earthen Berm has been depicted on the revised plan. This berm will create an
elevated portion of soil that will divert surface water around the construction area to
an area lined by the silt socks.
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5. HW recommends that the Applicant includes measures to maintain the infiltration capacity of
the existing soils where infiltration is proposed per§250-25.E.(12) of the North Andover
Code. The USDA soil maps list the soil type for this site as hydrologic soil groups `C' and `D'
which are poor for infiltration. HW also recommends that the Applicant provide the field
permeability tests to confirm the 24 inches/hour infiltration rate documented.
RESPONSE:
A report of the description of the Field Permeability Tests has been included in
revised submission
6. The Applicant has provided some results of the HydroCAD report and analysis for the
proposed system. HW recommends that the Applicant provide the entire HydroCAD output
for the 100-year event and include the stage storage tables for the infiltration system that will
be used in the drawdown calculations.
RESPONSE:
Full HydroCAD Report included in revised submission
7. The Applicant has provided a drywell to provide pretreatment prior to the infiltration system.
A drywell also infiltrates water. It is not clear how the drywell serves as a `pre-treatment' to
the infiltration rather than additional storage. Furthermore, it appears that any Total
Suspended Solids JSS) being treated in the drywell system would clog the system over
time. HW recommends that the Applicant provide a sump for solids to settle within the
drywell or providing a deep sump catch basin instead of a drywell as part of the
proposed project.
RESPONSE:
The Shea Mini Drywell will be placed as a component of the system that will allow for
the distribution of water into the infiltration system, while also allowing a certain
component of pretreatment (recognizing that under the Stormwater guidelines
pre-treatment is not required for the roof runoff for this Project). The Mini-Drywell as
a component of the system will have a Concrete bottom as depicted in the details on
Shea Mini Dry Well Depicted in revised plan, It will also be set such that the weep
holes within the drywell are located in close proximity to the bottom of the drywell
which will allow for the natural dewatering of this system component. Further the
bottom of this system component will be set at elevations 254, which is more than 2
feet above the soil motels found. (For further information regarding this system
component, see the response to HW Comment Number 8.)
8. HW notes that the Applicant has described the proposed 376 sf addition in the Watershed
Permit Application. HW notes that roof runoff that is being directed to the subsurface
chamber system is considered clean and does not need pretreatment.
RESPONSE:
The Mini Concrete Drywell, which will also allows for the water to seep out through
the weep-holes within the basin is, which will be included in this stormwater
infiltration system, as a component that will provide for any sedimentary material,
that finds its way into the downspout, to settle out within the 24 inch sump provided
by the drywell. This will proactively allow potential organic matter to settle within the
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system sump, thus preventing the possibility that it would clog the Cultec infiltrator
system components. Further, given that there will be a manhole cover, that will allow
for easy access for purposes of inspection, the applicant will be able to routinely
inspect the system for any potential build-up of sediment with the sump.
Also, the installation of a sump that also has the ability to allow the system to
de-water after the water that enters the system. This drywell component will allow
water to seep out of the sump, so that there will be no standing water within the
system. As a result, there will not be a continuous basin of water for insects, such as
mosquitos, to breed.
The inclusion of this system component will also allow for the replacement of this
single component if it becomes clogged with sediment, thus this will prevent the
potential for sediment to enter the infiltrators, preventing the system from becoming
compromised.
9. HW further notes that the Applicant has included 900 sf of future paved area in the
Stormwater Management Report. However, this area is not shown on the plans or in the
Permit Application. The driveway runoff should include pretreatment prior to infiltrating.
RESPONSE:
The applicant no longer includes plans for a future paved area within the
jurisdictional area of the lot. Further, if the applicant wants to include a paved surface
in the future, it will be placed outside of the jurisdictional area of the Bylaw.
10. HW recommends that the Applicant includes the bottom of stone, bottom of chamber, top of
chamber, top of stone and proposed surface elevation on the Cultec Recharger Detail
provided.
RESPONSE:
Included in revised plan.
11. HW recommends that the Applicant illustrate the drainage connection from the roof
downspouts and from the proposed driveway surface. As shown, it is not obvious
how stormwater will get into the drywell or into the Cultec chambers.
RESPONSE:
Included in revised plan.
12. HW recommends that the Applicant include any proposed grading on the site plan. It
appears that the Cultec recharge system proposed will require a change in surface
grades.
RESPONSE:
Included in revised plan.
13. The Applicant has provided an Operation and Maintenance (O&M) Plan as part of the
drainage report. HW recommends that the Applicant includes an inspection and
maintenance log and a simple sketch that clearly labels the stormwater practices as part of
the O&M Plan for use by the homeowner.
RESPONSE:
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Inspection and maintenance Log included with the revised submission.
Conclusions
HW recommends that the North Andover Planning Board require the Applicant to address the above
comments as part of its permit review process. We appreciate the opportunity to assist the Town of
North Andover with this project review. Please contact Janet Bernardo at 508-833-6600 or at
jbernardo(d0orsleywitten.com if you have any questions regarding these comments.
Sincerely,
HORSLEY WITTEN GROUP, INC.
r
Janet Carter Bernardo, P.E.
Principal