HomeMy WebLinkAbout2026/03/25 - 1st Stormwater Peer Review - - %�.
Horsley Wiften Group
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SLIStainable, Ehvirownental Solutions
112 W'at r `tr t-61 Floor-Boston,MBA 02109 ..........
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March 25, 2026
Ms. Jean Enright, Planning Director
Planning Department
Town of North Andover
120 Main Street
North Andover, Massachusetts 01845
Re: Initial Stormwater Peer Review
203 Turnpike Street— Solar Carport
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 Site Plan Application and Modification to
Special Permit for the proposed solar panel carport installation at 203 Turnpike Street in North
Andover, MA. The plans were prepared by Nobis Group on behalf of the North Andover Office
Park Condominium Trust c/o Colliers (Applicant). The existing parcel is approximately 5.31
acres and consists of two 4-story buildings containing 113,100 square feet (sf) of office space
with 386 parking spaces. The parking spaces are located primarily to the northeast and
southwest of the two buildings. There are no proposed changes to the existing buildings, the
number of parking spaces, or the limits of impervious surfaces.
The proposed project is to construct three separate carports with solar panels over existing
parking spaces. The total solar roof area is approximately 11,900 sf. In accordance with §195-
8.84 Site Plan Reviews and Special Permits are required for all solar energy systems. Per §195-
8.14 E. (8)All Site Plan Review applications require a Stormwater Management Plan prepared
in accordance with the Massachusetts Stormwater Handbook (MSH) and Chapter 165 of the
North Andover Bylaws.
The proposed carports and earthwork are located outside of the 100-foot buffer of the wetland
resource areas to the south and west of the existing buildings and therefore the project is
outside the jurisdiction of the North Andover Conservation Commission. HW understands that
the North Andover Conservation Agent has confirmed that the proposed project is not required
to file with them.
The following documents and plans were reviewed by HW:
• Project Narrative for Site Plan Application and Modification to Special Permit, 203 Turnpike
Street Solar Carport, prepared by Nobis Group, dated February 20, 2025 (2 pages);
• Special Permit Application, 203 Turnpike Street, North Andover, MA, prepared by North
Andover Office Park Condo Trust (3 pages);
• Waiver Request for Modification to Special Permit Application, Solar Carport, prepared by
Nobis Group, dated March 5, 2026 (1 page);
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Town of North Andover
March 25, 2026
Page 2of5
• Carport Sample Elevation (1 pages);
• Site Photos, Carport Solar, 203 Turnpike Street, North Andover, MA, prepared by Nobis
Group (5 pages);
• Email correspondence regarding Conservation Commission jurisdiction, dated through
February 27, 2026 (4 pages);
• Stormwater Management Plan, Solar Carport, prepared by Nobis Group, dated march 5,
2026 (109 pages); and
• Solar Carport, 203 Turnpike Street, North Andover, MA, prepared by Nobis Group, dated
March 6, 2026:
o Cover Sheet
o General Notes and Legend G-1
o Site Plan C-1
o Fire Truck Turning Plan C-2
o Construction Details C-3
Stormwater Management Design Peer Review
HW offers the following comments concerning the stormwater management design as per the
Massachusetts Stormwater Handbook (MSH) dated February 2008, and the North Andover
Chapter 165 Stormwater Management and Erosion Control Bylaw (Bylaw), and the Chapter 250
Stormwater Management and Erosion Control regulations (Stormwater Regulations) adopted
June 21, 2022.
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 analyzed the pre- and post-development stormwater runoff to two
points of analysis (POA).
(1) POA-1 is an existing 12-inch drainpipe that outfalls into the wetland resource area
on the west corner of the parcel. Wetland flag series 1 B though 14B.
(2) POA-2 is an existing 12-inch drainpipe that outfalls into the wetland resource area
on the south corner of the parcel. Wetland flag series 1 D through 12D.
b. HW recommends that the Applicant confirm that the two outfalls are not currently
causing erosion in wetlands or waters of the Commonwealth.
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. The Applicant has illustrated that the post-development stormwater runoff will be
identical to the pre-development runoff. The Applicant is not altering the impervious
surface within the parking lot and has not proposed any detention or retention
stormwater practices. No further action is requested.
Town of North Andover
March 25, 2026
Page 3 of 5
b. HW recommends that the Applicant clarify which direction the solar panels will pitch. It
appears that the downgradient side of the panels will be on the east side. HW
recommends that for clarity the Applicant include a note on the Site Plan.
c. Per §250-22 B. (5)(b) and §250-23 A. (1) of the North Andover Stormwater Regulations,
Low-Impact development (LID) site planning and design strategies must be implemented
to the maximum extent feasible. HW recommends that the Applicant document any LID
options it considered within the Project Area.
d. In accordance with §250-22 B. (5)(c), HW recommends that the Applicant identify the
watershed basin and the downgradient water body that stormwater from the project site
discharges into.
e. In accordance with §250-23 E. (19), the Applicant must utilize the 24-hour rainfall data
taken from National Oceanic and Atmospheric Administration (NOAA) Atlas 14 for the
rainfall precipitation depths. The Applicant has used the Cornell Extreme Precipitation
Rates Rainfall values, which are similar.
Year Cornell Values NOAA Atlas 14 Values
2-year 3.14 inches 3.15 inches
10-year 4.79 inches 5.00 inches
25-year 6.10 inches 6.15 inches
100-year 8.81 inches 7.93 inches
f. HW recommends that the Applicant use a grass and woods surface condition of"good"
instead of"fair." HW understands that this suggestion will not have any impact on the
design, as the existing and proposed conditions are identical.
3. Standard 3 requires that the annual recharge from post-development shall approximate
annual recharge from pre-development conditions.
a. The Applicant has illustrated that the post-development annual recharge will be identical
to the pre-development recharge. The Applicant is not increasing or decreasing the
impervious surface within the parking lot. No further action is requested.
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 proposed to add hooded outlets (Eliminators)to the existing catch
basins to improve the TSS removal obtained. HW recommends that the Applicant
confirm that the existing catch basins have 4-foot-deep sumps.
b. In Section 1 of the Stormwater Operation & Maintenance Plan the Applicant notes that
riprap overflow controls will be placed at the outlets to provide energy dissipation. HW
recommends that the Applicant confirms if any riprap is proposed at the existing outFalls.
Town of North Andover
March 25, 2026
Page 4 of 5
c. HW recommends that the Applicant include street sweeping on a routine schedule in
compliance with Volume 2, Chapter 1, page 9 of the MSH.
d. HW recommends that the Applicant address the Phosphorous removal calculations in
accordance with §250-23 C. (1) of the North Andover Stormwater Regulations.
5. Standard 5 is related to projects with a Land Use of Higher Potential Pollutant Loads
(LUHPPL).
a. The Applicant has indicated that the project is considered a LUHPPL, likely because of
the vehicle trips per day. The Applicant has also noted that it is meeting Standard 5 to
the maximum extent practicable by improving the TSS removal. No further action is
requested at this time.
6. Standard 6 is related to projects with stormwater discharging into a critical area, a Zone 11, or
an Interim Wellhead Protection Area of a public water supply.
a. The proposed development is not discharging near or into a critical area, Zone II or an
IWPA area. Standard 6 is not applicable.
7. Standard 7 is related to projects considered Redevelopment. A redevelopment project is
required to meet the following Stormwater Management Standards only to the maximum
extent practicable: Standard 2, Standard 3, and the pretreatment and structural best
management practice requirements of Standards 4, 5, and 6. Existing stormwater
discharges shall comply with Standard 1 only to the maximum extent practicable. A
redevelopment project shall also comply with all other requirements of the Stormwater
Management Standards and improve existing conditions
a. This project is considered a redevelopment. As listed above, the Applicant is required to
meet the standards to the maximum extent practicable and improve existing conditions.
HW recommends that the Applicant describe how it is improving existing conditions.
8. Standard 8 requires a plan to control construction related impacts including erosion,
sedimentation, or other pollutant sources.
a. The Applicant has provided erosion controls on Sheet C-1 and the associated details on
Sheet C-3. The catch basins will be installed with silt sacks, and an erosion control
barrier will be placed at the edge of the pavement closest to the resource areas. HW
notes that the area of land disturbance is relatively minimal, including 10 columns to hold
the canopies, and the installation of the electrical cables beneath the existing asphalt.
No further action is requested.
b. HW notes that the limit of disturbance will be less than 1 acre therefore a Construction
General Permit (CGP) and a Stormwater Pollution Prevention Plan (SWPPP) is not
required by EPA.
9. Standard 9 requires a Long-Term Operation and Maintenance (O & M) Plan to be provided.
a. The Applicant has provided an Operation and Maintenance Plan as Appendix D in the
Stormwater Management Report. The document can easily be removed as a standalone
reference. The plan lists the Landowner and Team Leader. However, there are several
contacts that are noted as TBD and references to the Town of Walpole that should be
corrected. The Planning Board may choose to require receipt of a final signed O&M Plan
Town of North Andover
March 25, 2026
Page 5 of 5
prior to land disturbance as a condition of approval.
b. HW recommends that the Applicant include inspection of the outfalls and sweeping of
the parking lot in the O&M Plan.
c. HW recommends that the Applicant provides a simple sketch that includes the
stormwater practices for the entire parcel, specifically all catch basins and outfalls. HW
further recommends that the sketch includes snow storage locations.
10. Standard 10 requires an Illicit Discharge Compliance Statement be provided.
a. The Applicant has provided an unsigned Illicit Discharge Compliance statement. The
Planning Board may choose to require receipt of a signed version as a condition of
approval.
Conclusions
HW recommends that the Planning Board requires the Applicant to provide a written response
to address these comments. 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
ibernardo(cD-horsleywitten.com if you have any questions regarding these comments.
Sincerely,
HORSLEY WITTEN GROUP, INC.
J
Janet Carter Bernardo, PE
Principal