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HomeMy WebLinkAboutSECOND peer Review Letter westonandsampson.com 427 Main Street, Suite 400, Worcester, MA 01608 Tel: 508.762.1676 December 31, 2024 Yarmouth Conservation Commission C/O Brittany DiRienzo, Conservation Administrator 1146 Route 28 Yarmouth, MA 02664 Re: Engineering Review of Stormwater Management Permit Application 228 Route 28 SECOND REVIEW Dear Commissioners: In accordance with your request, Weston & Sampson is pleased to present our second review of the above referenced application. The purpose of this letter report is to provide comments on the proposed stormwater drainage as it currently relates to regulatory compliance with the Town of Yarmouth Conservation Commission Stormwater Management Regulations (Effective July 1, 2021) and the Massachusetts Stormwater Handbook as referenced therein. Our review is based on information submitted to the Town by the Conserv Group and Green Seal Environmental, LLC., the “Engineer”, on behalf of A Plus Real Estate, LLC., the “Owner”. Weston & Sampson reviewed the following revised documents provided by the Engineer as they relate to the Stormwater Design.  A letter from Green Seal Environmental to the Yarmouth Conservation Commission written in response to our initial review comments from our letter dated October 8, 2024 (3 pages)  A plan sheet entitled “Erosion Control Details,” dated February 28, 2024 (1 sheet)  A document entitled “Erosion and Sedimentation Control Plan – Construction Period Pollution Prevention Plan (CPPPP),” dated October 22, 2024 (6 pages)  A document entitled “Long-Term Pollution Prevention and Operation and Maintenance Plan,” dated October 22, 2024 (5 pages)  A screenshot image of the HydroCAD rainfall tables information webpage (www.hydrocad.net/rainfall.tables.htm) Our review comments are provided below. Comments from our previous review are provided for reference in gray text, followed by updated comments. Town of Yarmouth Conservation Commission Stormwater Management Regulations Compliance Review Section 2.04 Stormwater Management Site Plan WSE 10/8/2024 COMMENT: The applicant has submitted all of the items required for submission under this section, subject to the comments presented below. Section 2.05 Stormwater Management Performance Standards 2.05(1) Low Impact Development WSE 10/8/2024 COMMENT: Under this standard the applicant is required to “document in writing why LID strategies are not appropriate when not used to manage stormwater.” LID examples cited in this standard include infiltrating roof runoff at the source, planting large canopy trees over impervious areas and using porous paving materials, etc. where feasible. The applicant has provided a brief statement indicating that it is their belief that LID strategies have been implemented as much as feasible, and that such measures include the planting of as many grassed/landscaped areas as possible. We offer no objection to the rationale presented by the applicant, this standard appears to be met. Page 2 westonandsampson.com 2.05(2) Good Housekeeping Procedures WSE 10/8/2024 COMMENT: We have noted the following in our review related to this standard:  This standard requires provisions for car washing to occur “on lawns or pervious areas using biodegradable and phosphate free detergent.” This is not discussed in the O&M plan. We recommend that the engineer address the item noted above. WSE COMMENT: The engineer has revised the Construction Period and Long-Term Pollution Prevention Plans to prohibit vehicle washing onsite. This comment has been addressed. 2.05(3) Stormwater Management Systems Design WSE 10/8/2024 COMMENT: We have noted the following in our review related to this standard:  The Engineer has shown that peak discharge rates do not exceed pre-development discharge rates for the 2, 10, and 100-year 24-hour storm events. Runoff from all areas of onsite improvement discharge to either an above-ground stormwater basin or subsurface chambers. These retain runoff from stormwater events including the 100-year event with no offsite runoff from these BMPs. These standards have been met.  This section includes a standard requiring pretreatment of runoff from metal rooftops if the site is discharging to a Zone II or interim wellhead protection area. The Engineer is proposing to discharge roof runoff into the subsurface infiltration system with no pretreatment, but the site does not appear to be within the areas described above and is not made of metal. This standard has been met.  This standard requires the use of NOAA Atlas 14 rainfall data for stormwater modeling, or alternative datasets at the discretion of the commission. It does not appear that the Engineer has used NOAA Atlas 14 data in the analysis. We recommend the Engineer revise the calculations to reflect the NOAA Atlas 14 data. WSE COMMENT: The engineer has responded, indicating that the rainfall values that were used in the calculations were derived from a dataset that is included in the Hydrocad software that is purported to consist of Atlas 14 rainfall data. We have confirmed by our own independent review of our Hydrocad software that the application does indeed include a dataset with the rainfall values used by the engineer, found in a rainfall event lookup file names “Atlas-14-Rain.txt” within the software. That being said, the rainfall values from that data file do not match what we understand to be the authoritative source of NOAA Atlas 14 rainfall data, which is the online NOAA precipitation frequency data server, found here: https://hdsc.nws.noaa.gov/pfds/ Based on the data server, the values for the 2, 10 and 100-year 24-hour storm events are 3.38, 4.93 and 7.38- inches, respectively. We recommend that the engineer use these values. 2.05(4) Stormwater Management System Pollutant Removal Requirements (new development) WSE 10/8/2024 COMMENT: This is a redevelopment project and this standard is not applicable. 2.05(5) Stormwater Management System Pollutant Removal Requirements (redevelopment) WSE 10/8/2024 COMMENT: We have noted the following in our review related to this standard: Page 3 westonandsampson.com  Stormwater management systems for redevelopments shall be designed to meet an average annual pollutant removal equivalent to 80% of the average annual post-construction load of TSS AND 50% of the average annual load of TP AND 30% of the average annual load of TN related to the total post-construction impervious area on the site. The Engineer has routed all trafficked impervious areas through pretreatment into infiltration practices and is infiltrating 0.8 inch multiplied by the total post-construction impervious surface area on the redeveloped site. This standard has been met. 2.05(6) Stormwater Management System EPA Tool Analysis WSE 10/8/2024 COMMENT: We have noted the following in our review related to this standard:  The applicant has not used the EPA Region 1 BMP Accounting and Tracking Tool to evaluate average yearly pollutant removal for the BMPs. Under this standard, applicants are required to provide this analysis or are otherwise allowed to use other federal or state approved performance standards when the EPA tools are not applicable for the proposed BMPs. If the presumption stated under 2.05(5) is correct and the Engineer is using 0.8-inch of retention as a means of satisfying the nutrient removal standards, then the EPA Tool Analysis would not be required. This standard has been met. 2.05(7) Discharges to water bodies subject to TMDL WSE 10/8/2024 COMMENT: The site does not discharge to a water body subject to a TMDL. Section 2.06 Erosion and Sediment Control Plan Standards 2.06(1) Contents of Erosion and Sediment Control Plan WSE 10/8/2024 COMMENT: The applicant has submitted plans for Erosion and Sediment Control which are substantially complete, subject to further comments below. 2.06(2) Stormwater Pollution Prevention Plan (SWPPP) Submission WSE 10/8/2024 COMMENT: The project will disturb more than one acre of land, therefore it will be subject to coverage under the NPDES Construction General Permit. Under this section, the applicant is required to submit a complete copy of the SWPPP for the project. We recommend that the applicant submit a copy of the SWPPP. The commission may wish to consider adopting a condition of approval requiring the submission of the SWPPP prior to any ground disturbing activity since the contractor will ultimately be the party responsible for the SWPPP. WSE COMMENT: The engineer has requested that the requirement for the submission of a SWPPP be addressed through a condition of approval for the project for the SWPPP to be submitted prior to construction. We offer no objection to this approach; the commission should consider whether it wishes to address this with such a condition. 2.06(3) Design of erosion and sediment controls WSE 10/8/2024 COMMENT: The applicant’s erosion and sediment control plan substantially conforms to this standard. 2.06(4) Erosion and Sedimentation Control Plan Content WSE 10/8/2024 COMMENT: We have noted the following in our review related to this standard:  This standard calls for a description of how fueling of vehicles/equipment and fuel/chemical storage will be conducted. This was not found on the plan. The engineer should address this. Page 4 westonandsampson.com  This standard calls for the identification of “trees with a caliper twelve (12) inches diameter breast height or larger, noting specimen trees and forest communities.” This was not found in the submitted materials. We recommend that the applicant either clarify whether this is applicable, submit the applicable information, or request a waiver from the commission if that is the applicant’s intent.  A description of procedures for construction vehicle fueling, temporary chemical storage and construction vehicle washing/washout was not found. The engineer should address this. WSE COMMENT: The engineer has added language to the Construction Period Pollution Prevention Plan to address fueling, washout and fuel/chemical storage. The engineer has also noted that the site has little tree cover and that the only trees 12-inch and over occur at the periphery of the site and are noted to be preserved. Plans indicate that the existing tree line at the periphery of the site is to be preserved and there does not appear to be any tree removal required, therefore the requirement for showing 12-inch or larger trees may be moot. We believe that the comments above have been addressed. 2.07 Operation and Maintenance (O&M) Plan 2.07(1) Stand-alone O&M plan requirements WSE 10/8/2024 COMMENT: We have noted the following in our review related to this standard:  There are comments noted farther above that the applicant should address related to the O&M plan.  The O&M plan is currently formatted as a chapter within the stormwater report. The commission may wish to advise whether it is desirable to have it separated as a “stand-alone” report. WSE COMMENT: The engineer has provided separate Construction and Long-Term Pollution Prevention Plans. This comment has been addressed. Under these standards, compliance with the MA Stormwater Handbook is required. Compliance with the Handbook is further discussed below. Massachusetts Stormwater Handbook Compliance Review Under Section 2.04(1) of the Yarmouth Conservation Commission Stormwater Management Regulations, the standards of the Massachusetts Stormwater Handbook are adopted by reference. These standards are listed below, followed by our review comments. Standard 1: Untreated Stormwater WSE 10/8/2024 COMMENT: No new point discharges of untreated stormwater are proposed. The proposed stormwater improvements for the site include deep sump hooded catch basins, drain manholes, underground stormwater chambers, hydrodynamic separators and an infiltration basin. The design proposed no new outfalls for stormwater to leave the site and proposes to retain stormwater up to and including the 100-year storm event. This standard has been met. Standard 2: Post Development Peak Discharge Rates WSE 10/8/2024 COMMENT: The stormwater report analyzed the site for storm events with recurrence intervals of 2-, 10-, and 100-years. The analysis indicates that the post-redevelopment peak discharge rates will be less than existing condition peak discharge rates. This standard has been met, subject to comments under the heading of other standards below. Page 5 westonandsampson.com Standard 3: Recharge to Groundwater WSE 10/8/2024 COMMENT: This standard requires that the site infiltration mimic preconstruction conditions for small storms based on the proposed increase in impervious area. The engineer has submitted calculations showing that onsite stormwater BMPs have been designed to retain and recharge far above the minimum required recharge volume. The Engineer has shown test pit data for the site, and adequate separation to groundwater appears to be provided for the subsurface infiltration system. This standard has been met. Standard 4: Total Suspended Solids (TSS) Removal WSE 10/8/2024 COMMENT: The town standards for TSS removal and stormwater quality treatment are more stringent than this standard. Compliance with the town’s standards is discussed in the preceding comments. We believe that this standard has been met. Standard 5: Land Uses with Higher Potential Pollutant Loads (LUHPPLs) WSE 10/8/2024 COMMENT: The Engineer has indicated that the proposed development is not a LUHPPL. We agree with this assessment. Standard 6: Protection of Critical Areas WSE 10/8/2024 COMMENT: The applicant’s submission indicates that the site is not within a critical area. Even so, the proposed stormwater BMPs are in keeping with what is required under this standard. This standard has been addressed. Standard 7: Redevelopments WSE 10/8/2024 COMMENT: This project qualifies as a redevelopment. The applicant has met the redevelopment standards and documented compliance. This standard has been addressed. Standard 8: Construction Period Pollution Prevention and Erosion/Sedimentation Control WSE 10/8/2024 COMMENT: The engineer has provided an erosion and sedimentation control plan. Due to the fact that the site will disturb more than one acre, a Stormwater Pollution Prevention Plan (SWPPP) will be required to obtain coverage under the NPDES Construction General Permit. The town’s standards related to this are more stringent. Provided that the applicant addresses the preceding comments, this standard from the Handbook will be satisfied. Standard 9: Operations & Maintenance Plan WSE 10/8/2024 COMMENT: A long-term pollution prevention and operations and maintenance plan have been provided. Further comments that related to this standard are provided above under the analysis of the town’s similar standard. Provided that those comments are addressed, this standard from the Handbook will be satisfied. Standard 10: Illicit Discharge Compliance Statement WSE 10/8/2024 COMMENT: The engineer has stated that an Illicit Discharge Compliance Statement will be signed by the responsible party prior to the start of construction. The Commission may wish to include this as a condition of approval for the project. WSE COMMENT: The engineer has indicated that an illicit discharge statement was attached to their response. We did not find this in the materials provided to us for review. The Commission may wish to address this with the applicant. Page 6 westonandsampson.com General Comments:  WSE 10/8/2024 COMMENT: Trench drains were proposed on the grading and drainage plan. The Engineer should provide a detail of the proposed trench drains. WSE COMMENT: The engineer has provided a revised detail sheet showing a trench drain detail. This comment has been addressed. Weston & Sampson appreciates the opportunity to present our findings. We are available at your earliest convenience to discuss our report. Please contact me if you have any questions. I may be reached at (978) 532-1900 or pearsonj@wseinc.com. Sincerely, WESTON & SAMPSON ENGINEERS, INC. James I. Pearson, PE Technical Leader