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HomeMy WebLinkAbout2026/04/03 - 2nd Stormwater Peer Review - - Horsley Wi ften Group %. "S .. i it I eI ... Iwnental... Solutions 112 Water Stru t-61 Floor Boston,MBA 02109 '"` April 3, 2026 Ms. Jean Enright, Planning Director Planning Department Town of North Andover 120 Main Street North Andover, Massachusetts 01845 Re: Second 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 second 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 additional documents and plans were received by HW in response to our initial review letter dated March 25, 2026: • Response to Comments letter, 203 Turnpike Street Solar Carport, prepared by Nobis Group, dated March 30, 2026 (14 pages); • Stormwater Management Plan, Solar Carport, prepared by Nobis Group, revised March 30, 2026 (121 pages); and Town of North Andover April 3, 2026 Page 2of6 • Solar Carport, 203 Turnpike Street, North Andover, MA, prepared by Nobis Group, dated March 6, 2026, revised March 30, 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. The following comments correlate to our initial review letter dated, March 25, 2026. 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 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. April 3, 2026: No further action is requested. b. HW recommends that the Applicant confirm that the two outfalls are not currently causing erosion in wetlands or waters of the Commonwealth. April 3, 2026: The Applicant has confirmed that the existing site is not currently causing erosion at either outfall. HW would not expect the post-development conditions to impact the existing outfalls. No further action is requested. 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. April 3, 2026: No further action is requested. Town of North Andover April 3, 2026 Page 3of6 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. April 3, 2026: The Applicant has stated that the solar panels will be pitched to the southwest. This appears to be reasonable for the two sets of panels closest to Building B. However, the panels closest to Building A will pitch onto the adjacent retaining wall. HW recommends that the Applicant confirms this is the intention and that the retaining wall will not be compromised. 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. April 3, 2026: The Applicant included in its response letter a list of LID practices that were considered and eliminated as not being feasible. No further action is requested. 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. April 3, 2026: The Applicant has noted that the downgradient water body is the Shawsheen River. No further action is requested. 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 April 3, 2026: No further action is requested. 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. April 3, 2026: The Applicant has updated the Existing and Proposed HydroCAD model using a surface condition of "good" for woods. No further action is requested. Town of North Andover April 3, 2026 Page 4 of 6 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. April 3, 2026: 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. April 3, 2026: The Applicant has noted that the catch basins require maintenance to confirm the depth of the sumps. The Planning Board may choose to require confirmation of the catch basin cleaning as a condition of approval. 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. April 3, 2026: The Applicant has removed this statement. No further action is requested. 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. April 3, 2026: The Applicant has stated that because of the parked cars, street sweeping would be considered a burden while providing minimal benefit. HW defers discussion of this long-term maintenance program to the Planning Board. HW imagines that there are typical times during a week when the parking lot of this medical office building is not full of cars. d. HW recommends that the Applicant address the Phosphorous removal calculations in accordance with §250-23 C. (1) of the North Andover Stormwater Regulations. April 3, 2026: The Applicant has provided the required calculations. There will be no reduction of phosphorous from the existing site conditions. No further action is requested. 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. April 3, 2026: No further action is requested. Town of North Andover April 3, 2026 Page 5 of 6 6. Standard 6 is related to projects with stormwater discharging into a critical area, a Zone Il, 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. April 3, 2026: No further action is requested. 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. April 3, 2026: The Applicant is improving existing conditions by adding hoods to the existing catch basins and submitting a Long-term Operation & Maintenance Plan for the property. HW supports the installation of solar panels on the existing parking lot. However, it would appear that something more could be done to improve the stormwater management of the parking lot runoff that is directed towards the adjacent resource area. Suggestions include regular sweeping of the parking lot, confirming and/or installing catch basins throughout the parcel that have four-foot sumps, and/or removing excessive impervious surfaces in the southern corner of the lot. HW defers further discussion of any improvements to the Planning Board. 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. April 3, 2026: 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. April 3, 2026: No further action is requested. 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 Town of North Andover April 3, 2026 Page 6of6 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 prior to land disturbance as a condition of approval. April 3, 2026: Suggested 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. April 3, 2026: The Applicant has included inspection of the outfalls in the O&M Plan. It has removed the sweeping of the parking lot. It is HW's opinion that the parking lot should be swept a minimum of once a year. 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. April 3, 2026: The Applicant has included a sketch, with its response to comments, that indicates where the existing snow storage is located on the site. HW recommends that a simple sketch that clearly calls out each catch basin and outfall is attached to the O&M Plan for the benefit of the property owner. HW further notes that the Table of Contents provided in the O&M Plan and the list of items included in Appendix A should be reviewed and updated. 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. April 3, 2026: Suggested condition of approval. Conclusions HW has included a few suggested conditions of approval for consideration by the Planning Board. We further recommend that the Applicant describe to the Planning Board how it is improving existing conditions and what the long-term maintenance will be. 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 ibernardoCcD-horsleywitten.com if you have any questions regarding these comments. Sincerely, HORSLEY WITTEN GROUP, INC. J Janet Carter Bernardo, PE Principal