HomeMy WebLinkAbout230206_HW1stPeerReview_34 Glenore Circle - - 34 GLENORE CIRCLE Horsley Witten Group
Sustairiable Etivironmental Solutions
112 Wafer Street•80"Floor•Boston,AAA 02109 „
857-263-8193•horsleywit¢en.com
February 6, 2023
Ms. Jean Enright, Planning Director
North Andover Planning Board
120 Main Street
North Andover, Massachusetts 01845
Ref: Special Watershed Permit Peer Review
34 Glenore Circle
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 letter report summarizing our initial review of the Watershed Permit Application for the
proposed pool construction at 34 Glenore Circle, North Andover, MA. The plans were prepared
by Sullivan Engineering Group, LLC, on behalf of David & Marianne Sweetser (Applicant). The
project proposes the construction of an inground pool with an enclosure, a pervious paver patio,
a firepit, and a deck. The stormwater from the pool enclosure roof will be directed to a proposed
subsurface infiltration system (SIS). The proposed work will not include tree removal.
The proposed construction is approximately 190 feet from the onsite wetland resource area,
located along the eastern border of the site. The proposed work is over 200 feet from Lake
Cochichewick and within the Watershed Protection District. The proposed work is located within
the 325-foot Non-Discharge buffer to a wetland resource within the Watershed Protection
District. In accordance with §195-4.19. B. of the North Andover Zoning Bylaws, any surface or
subsurface discharge proposed within the Non-Discharge Buffer Zone requires a Special
Watershed Permit.
The following documents and plans were received by HW:
• Stormwater Report Plan, 34 Glenore Circle, North Andover, MA, prepared by Sullivan
Engineering Group, LLC, dated October 11, 2022 (1 page);
• Special Permit- Watershed Permit Application, 34 Glenore Circle, North Andover, MA,
prepared by Sullivan Engineering Group, LLC (92 pages); and
• Plot Plan of Land, 34 Glenore Circle, North Andover, MA, prepared by Sullivan
Engineering Group, LLC, dated January 23, 2023 (1 sheet).
Stormwater Management Design Peer Review
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.
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Town of North Andover
February 6, 2023
Page 2 of 3
HW has the following comments regarding the proposed stormwater management design.
1. It appears that the proposed grading is minimal, with the new patio being set on the
relatively level existing lawn area.
2. The bottom of the proposed SIS is located 3 feet above the Estimated Seasonal High
Groundwater Table (ESHGWT). HW recommends that the Applicant conduct a
mounding analysis to confirm that the groundwater will not mound up into the chamber
system.
3. It appears that the Applicant is not proposing an overflow outlet for the SIS. HW
recommends that the Applicant confirm where stormwater will be directed if the system
is at capacity.
4. The Applicant has provided adequate recharge volume within the SIS.
5. The Applicant has provided a watershed map in the Stormwater Report Plan. HW
understands that the existing and proposed catchment areas are identical for this
project.
6. The Applicant has analyzed two subcatchment areas draining to two design points under
existing conditions. It appears that Design Point 1 is the bordering vegetated wetland
(BVW) to the east, and Design Point 2 is the catch basin located in the grass at the end
of the driveway. It appears that a small portion of Subcatchment 2 along the southern
property boundary drains to Design Point 1.
7. According to the HydroCAD model, the total runoff area is 62,142 sf. However, based on
the existing conditions watershed figure provided in the Stormwater Report Plan, it
appears that the total runoff area is closer to 75,000 sf. HW recommends that the
Applicant verify the total runoff area for the watershed, specifically the area listed as
subcatchment area 1.
8. HW recommends that the Applicant confirm the area of grass cover under existing and
proposed conditions and adjust the HydroCAD model accordingly.
9. The Applicant has used the precipitation depths as defined in the Hydrology Handbook
for Essex County. HW understands that the 2008 Massachusetts Stormwater Handbook
(MSH) is being updated soon to require precipitation depths as specified by the NOAA
Atlas 14 Precipitation Frequency Estimates. HW recommends that the Applicant
consider revising its HydroCAD model for the 10- and 25-year storm to use the more
conservative depths as listed in the Table below:
Recurrence Interval Hydrology Handbook NOAA Atlas 14 (inches)
(inches)
10 year 4.80 5.04
25 year 6.00 6.20
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Town of North Andover
February 6, 2023
Page 3 of 3
10. The Applicant is proposing the installation of a silt fence erosion control barrier at the
limit of work. HW concurs with the chosen erosion control measures.
11. The Applicant has proposed inserting a silt sack in the existing catch basin. HW
recommends that the Applicant provide a silt sack detail.
12. The Applicant has included a proposed materials staging and soil stockpile area on the
site plan which is outside of the 150-foot non-disturbance zone.
13. HW recommends that a standalone Operation & Maintenance (O&M) Plan be provided
to the homeowner for long term maintenance of the existing catch basin, permeable
pavers, roof drains, and SIS. HW further recommends that a plan is attached to the O&M
Plan that clearly illustrates where all stormwater practices are located on the property.
14. The Applicant has provided an Illicit Discharge Statement. HW recommends that the
Town require the Illicit Discharge Statement to be signed by the property owner.
15. HW recommends that the Applicant explain to the Planning Board the methodology for
pumping out the pool at the end of the season. Specifically, where will the pool water be
pumped to and how will the Applicant confirm that pool chemicals will not be discharged
towards the resource area. The pool maintenance should be included in the O&M Plan
for the owners use.
Conclusions
HW recommends that the Planning Board require that the Applicant provide a written response
to address these comments as part of the Board's review process. The Applicant is advised that
provision of these comments does not relieve him/her of the responsibility to comply with all
Town of North Andover Codes and By-Laws, Commonwealth of Massachusetts laws, and
federal regulations as applicable to this project. Please contact Janet Bernardo at 508-833-6600
or at jernardo@horsleywitten.com if you have any questions regarding these comments.
Sincerely,
HORSLEY WITTEN GROUP, INC.
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Janet Carter Bernardo, P.E. Veronica Seward-Aponte
Associate Principal Environmental Engineer
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