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HomeMy WebLinkAbout02/14/2023 - Response to 1st Stormwater Peer Review - - 149 MAIN STREET A, IVEiA /V 'Technical ExcellIenice Practical Experience Client Responsiveness 14 February 2023 Ms. Jean Enright, Planning Director North Andover Planning Board 120 Main Street North Andover, Massachusetts 01845 Re: Initial Stormwater Peer Review: Response to Comments 149 Main Street& 14 Second Street North Andover, MA Langan Project No.: 151028501 Dear Ms. Enright, On behalf of Main and Second LLC, please find our responses to the Horsley Witten Group, Inc. (HW) Initial Stormwater Peer Review letter dated 07 December 2022 for the proposed mixed use development project at 149 Main Street and 14 Second Street in North Andover, MA. Below please find each comment followed by our response in bold. STORMWATER REVIEW COMMENTS I 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. It appears that the existing site sheet flows onto Main Street and Second Street and is captured by the existing municipal drainage system. Runoff appears to flow north down Main Street and east down Second Street with a low point at the two catch basins at the intersection of Main and Second Streets. Under proposed condition b. s the Applicant has intercepted the runoff from the site and piped it into the municipal drainage system. It does not appear that the stormwater is directed into a wetland resource area. However, HW recommends that the Applicant document where the municipal drainage system eventually outlets. COMMENT RESPONSE.- The site is located within the Merrimack River watershed and the municipal drainage system ultimately discharges to the Merrimack River. AV This has been confirmed with the town engineering department. The Merrimack River is located approximately 2,300 feet from the site. 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 drawn the existing and proposed watershed maps within the property boundaries of the Project Site. It appears that the parcels directly to the south of the 100 Cambridge Street,, Suite 1310 Boston, IMA 02114 T, 617.8,24.91,00 IF. 617.824.9101 www.1l,a.ngan.com New�Jersey a New,York*ConnecticiA-*Massachusetts*Pennsylvania 9 Washington, DC 9 Ohio*Illinois*Florid�*Texas*Arizona o,Colorado*Wa5hington*California Athens 6 Calgary*Dubai a London* Panama, Initial Stormwater Peer Review: Response to Comments 14 February 2023 149 Main Street& 14 Second Street Page 2 of 7 North Andover, MA Langan Project No.: 151028501 site at 159 Main Street and 161 Main Street may flow onto the proposed development. HW recommends that the Applicant clarify where the runoff from 159 and 161 Main Street is directed under existing and proposed conditions. COMMENT RESPONSE: We have visited the site and confirmed that runoff from portions of 159 and 161 Main Street under existing and proposed conditions drain on to the project site. This includes a portion of the roof of the house and small paved area at 159 Main Street and a portion of the shed at 161 Main Street. A berm runs along the property line at 161 Main Street and the project site, which keeps the runoff from the majority of 161 Main Street on its own property. We have updated our existing and proposed condition HydroCAD models, figures, pipe calculations, and design to accommodate the off-site runoff. b. If the proposed stormwater features are capturing offsite runoff, HW recommends that the Applicant confirm the stormwater systems are sized adequately. COMMENT RESPONSE: See comment response 2(a) above. c. HW has reviewed the HydroCAD model provided in the Stormwater Report. We concur with the curve numbers and time of concentration (Tc) values included in the model. COMMENT RESPONSE: No response required. d. The Applicant has utilized precipitation values in accordance with the Northeast Regional Climate Center (NRCC). HW recommends that the Applicant use 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) of the North Andover Code. COMMENT RESPONSE: We have revised the precipitation values in our calculations and models to use the highest values from NOAA Atlas 14 and NRCC for the storm events. See revised Stormwater Management Report Section 2.3 for the revised rainfall data and Appendix A and B for the updated HydroCAD calculations. e. 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 but not the peak volumes for the 2-year, 10-year, 25-year, and 100-year storm events. HW recommends that the Applicant add the peak volumes to Table 1 in the narrative. COMMENT RESPONSE: We have revised the Stormwater Management Report Table 1 to include peak volumes. The post-development peak flow rates are less than the pre-development peak flow rates. The post-development peak volumes are slightly higher(14%)than the pre-development peak volumes for some of the storm events. The amount is not significant and will not anticipated to have a LAIVGA/V Initial Stormwater Peer Review: Response to Comments 14 February 2023 149 Main Street& 14 Second Street Page 3 of 7 North Andover, MA Langan Project No.: 151028501 negative impact downstream or off-site. Since the project will have less than 1 acre of disturbance and therefore a land disturbance permit is not required, the project does not meet the threshold of the bylaw requirements noted above. The project's stormwater management design is in compliance with the Massachusetts Stormwater Standards. f. HW recommends that the Applicant review the proposed contours at the top of curbs. Furthermore, HW recommends that the Applicant add spot grades along the patio areas to confirm runoff is being directed away from the building and towards the trench drains. COMMENT RESPONSE: We have revised the plan to include additional top of curb, top of wall, and patio area elevations. See CG 101. g. The Applicant has proposed a subsurface infiltration system to manage the roof runoff and a portion of the parking lot. The system includes 431 R-Tanks that are 13.8 inches in height with 3 inches of stone placed below the tanks and 6 inches of stone placed over the tanks. HW recommends that the Applicant include the total number of tanks to be installed on the plan set. COMMENT RESPONSE: The total number of tanks to be installed have been added to the plan. See CG101. h. The Applicant has noted that the subsurface system is a combined detention/infiltration system. The HydroCAD model does not include an exfiltration rate to indicate that infiltration has been included. HW recommends that the Applicant clarify the type of stormwater practice proposing. COMMENT RESPONSE: The subsurface system will be a detention and infiltration system and has been designed to exfiltrate the required recharge volume. The HydroCAD model does not include exfiltration in model since the separation from groundwater is greater than 2 feet, but less than 4 feet. Maintaining the pre- development peak flows in post-condition is met without including the exfiltration rate in the HydroCAD model. i. The soil test pits provided indicate that a concrete slab was encountered in the area where the subsurface stormwater system is proposed. HW recommends that the Applicant indicate on the plan set that the concrete slab will be removed in its entirety as well as any fill encountered beneath the subsurface stormwater system. COMMENT RESPONSE: The plan set has been revised to indicate the concrete slab is to be removed, see Sheet CE101 and CS002(Grading and Drainage Note 12). The applicant will have an additional soil test pit conducted by a qualified soil professional before the subsurface infiltration/detention system is installed. The soil professional will determine the soil textural classification of the material below the slab and if it is a sandy loam, loamy sand, or sand we recommend allowing the soil to remain. If the material does not meet that LAIVGA/V Initial Stormwater Peer Review: Response to Comments 14 February 2023 149 Main Street& 14 Second Street Page 4 of 7 North Andover, MA Langan Project No.: 151028501 criteria we recommend removal of up to 2 feet of the soil below the bottom of the infiltration system and the replacement with a soil of a textural classification of sandy loam, loamy sand, or sand. The applicant will provide documentation to the Planning Board of the soil test pit investigation and findings. We have added a note to Sheet CS002 (Grading and Drainage Note 11). We recommend that this be made a condition of approval. 3. Standard 3 requires that the annual recharge from post-development shall approximate annual recharge from pre-development conditions. a. It appears from adjacent test pits that the subsurface infiltration system will have greater than 2 feet of separation to Estimated Seasonal High Groundwater (ESHGW) but less than 4 feet. HW recommends that the Applicant provide a mounding analysis per the MSH Volume 3, Chapter 1, Page 28. Furthermore, HW recommends that additional soil testing is conducted prior to installation of the system to confirm that adequate separation has been provided. COMMENT RESPONSE: The subsurface system will be a detention and infiltration system and has been designed to provide storage of the required recharge volume below the outlet control structure weir. The vertical separation from the bottom of the subsurface system to Estimated Seasonal High Groundwater(ESHGW)is greater than 2 feet and less than 4 feet, but the system does discharge flow from a 10-year or higher 24-hour storm. Even so, we have provided a groundwater mounding analysis using the Hantush method and the maximum groundwater mounding is 0.13 feet, which is below the bottom of the infiltration system. Please refer to Appendix C of the revised Stormwater Report for the groundwater mounding analysis. Please refer to response 2(i) above regarding the additional soil testing. b. The Applicant has provided the required recharge volume and drawdown time calculations per the MSH Volume 3, Chapter 1, Pages 15 and 25. The recharge calculations indicate an exfiltration rate of 1.02 inches per hour (iph). HW concurs that this value is reasonable however as noted previously additional soil testing beneath the subsurface infiltration system should be conducted prior to installation. HW further notes that additional soil testing should be performed by a soil professional, and documentation provided to the Planning Board. COMMENT RESPONSE. See comment response 2(i)above. 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 noted in its narrative that the proposed stormwater system has been designed to treat one-half inch of water quality volume. Per §250-23 B. (1)(b) new developments are required to retain the volume of runoff equivalent to one inch multiplied by the total post-construction impervious surface. Per §250-23 C. (1)(b) LAIVGA/V Initial Stormwater Peer Review: Response to Comments 14 February 2023 149 Main Street& 14 Second Street Page 5 of 7 North Andover, MA Langan Project No.: 151028501 redevelopment projects are required to retain the volume of runoff equivalent to 0.8 inches multiplied by the total post-construction impervious surface. Per §250-23 C. (2) when both new development and redevelopment are proposed for a project site, the redevelopment and new development work shall be conducted per the applicable regulations. HW recommends that the Applicant review the proposed design and confirm compliance with §250-23 Design and Performance Criteria. COMMENT RESPONSE: Since the project will have less than 1 acre of disturbance and therefore a land disturbance permit is not required,the project does not meet the threshold of the bylaw requirements noted above. The project"s stormwater management design is in compliance with the Massachusetts Stormwater Standards. b. HW recommends that the Applicant provide documentation to support the TSS removal provided by the Trench Drain Filter. COMMENT RESPONSE: Supporting documentation from the manufacturer for the trench drain filter is included in Appendix D of the revised Stormwater Management Report. 5. Standard 5 is related to projects with a Land Use of Higher Potential Pollutant Loads (LUHPPL). a. The site is not considered a LU H PPL. Therefore, Standard 5 is not applicable. COMMENT RESPONSE: No response required. 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 development is not discharging near or into a critical area, Zone II or an IWPA area. Therefore! Standard 6 is not applicable. COMMENT RESPONSE: No response required. 7. Standard 7 is related to projects considered Redevelopment. a. The proposed project is a mix of new development and redevelopment. The area consisting of the existing parking lot behind the existing commercial building may be considered redevelopment. In this redevelopment area, a decrease in paved area is proposed and being converting to roof top which is considered an improvement. The proposed roof runoff is being managed by the subsurface infiltration system as new development. HW recommends that the Applicant respond to the other comments in this review letter to confirm it has adequately incorporated Standard 7. COMMENT RESPONSE: The project is mix of new and redevelopment and the project's stormwater management system is in full compliance of the Massachusetts Stormwater Standards. LAIVGA/V Initial Stormwater Peer Review: Response to Comments 14 February 2023 149 Main Street& 14 Second Street Page 6 of 7 North Andover, MA Langan Project No.: 151028501 8. Standard 8 requires a plan to control construction related impacts including erosion, sedimentation, or other pollutant sources. a. The proposed project requires land disturbance of under 1 acre. Therefore, a Stormwater Pollution Prevention Plan (SWPPP) per the EPA NPDES Construction General Permit will not be required. COMMENT RESPONSE. No response required. b. HW recommends that the Applicant confirm that any stormwater runoff from the upgradient properties that may currently flow onto the site will not cause ponding on abutting properties during construction. COMMENT RESPONSE. See comment response 2(a). Where consistent with existing conditions, positive drainage from the upgradient properties onto the site will be maintained and will not pond on abutting properties during or after construction. Note 3 (under Soil Erosion-Sediment Control Notes, subsection Proposed Development) has been added to CS002 that the contractor is to maintain existing drainage patterns from upgradient properties onto the project site during and after construction. c. HW recommends that the Applicant explain how the site will be accessed during construction and locate the stabilized construction entrance on the erosion control plan. COMMENT RESPONSE: The site will be accessed during construction from the existing paved driveway curb cuts on Main Street and Second Street. As construction progresses and the existing asphalt pavement is required to be removed, the contractor will install a rock construction entrance on Main Street and Second Street. Please see revised CE101. d. In accordance with §250-23 A. (7) of the North Andover Code the Applicant has identified five (5) trees to be removed within the limit of disturbance. The Applicant has illustrated six (6) trees to be planted along Main Street and Second Street. HW recommends that the Applicant confirm whether the critical root zones (CRZs) of any large trees will be impacted by the proposed development; construction activity over CRZs will potentially damage the root systems of trees and cause long-term degradation of the tree's health. HW further recommends that any trees at the edge of the limit of work proposed to be protected are clearly marked in the field and a tree protection detail is added to the plan set. COMMENT RESPONSE. We have identified nine trees on CE101 to be removed within the limit of disturbance. The large trees that would be impacted by the proposed development are the ones being proposed to be removed. We have proposed a total of 12 trees to be planted as part of the project on Main Street, Second Street, and on the site. 9. Standard 9 requires a Long-Term Operation and Maintenance (0 & M) Plan to be provided. LAIVGA/V Initial Stormwater Peer Review: Response to Comments 14 February 2023 149 Main Street& 14 Second Street Page 7 of 7 North Andover, MA Langan Project No.: 151028501 a. In accordance with the MSH Volume 1 Chapter 1 Page 23, the Applicant has provided a Long-Term Operation & Maintenance Plan as a standalone document as Appendix F of the Stormwater Management Plan. HW recommends that the Planning Board reference this document and require a signed O&M Plan as a condition of approval. COMMENT RESPONSE: The applicant has provided a signed O&M Plan. Please refer to page 2 of Appendix F of the revised Stormwater Management Report. b. HW recommends that the 0&M Plan include a simple plan that is drawn to scale and shows the location of all stormwater practices within the parcel requiring inspections and long-term maintenance. COMMENT RESPONSE: A plan has been added to the O&M indicating the location of all stormwater practices. Please refer to Appendix F of the revised Stormwater Management Report. 10. Standard 10 requires an Illicit Discharge Compliance Statement be provided. a. The Applicant has provided an Illicit Discharge Compliance Statement in Appendix G of the Stormwater Management Plan. HW recommends that the Planning Board include a condition of approval requiring that the Illicit Discharge Compliance Statement be signed by the property owner prior to land disturbance. COMMENT RESPONSE: The applicant has provided a signed Illicit Discharge Compliance Statement. Please refer to Appendix G of the revised Stormwater Management Report. Should you have any questions or require any additional information, please contact me at (781) 264-3874 or fholmes@langan.com. Sincerely, Langan Engineering and Environmental Services, Inc. U Frank Holmes, PE Senior Associate Hilary Holmes, PE Senior Project Engineer Cc: Janet Carter Bernardo, Richard Crespo, Kyle Young, John Smolak Enc: Revised Stormwater Management Report Revised Site Plans (CS001, CS002, CS101, CG 101, CE101, CS503, CS505) \\1angan.com\data\BCS\data5\151028501\Project Data\Correspondence\Comment Response\Stormwater Peer Review Response to Comments 2023-02-14.docx LAIVGA/V