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HomeMy WebLinkAbout07/10/2019 - Horsley Witten Group Stormwater Peer Review #1 - 481 Sutton Street A ��pppp Horsley Wiften Grouper Sustainable Environmental Solutions 294 Washington Street•Suite 801•Boston,MA 02108 857-263-8193•horsleywitten.com July 10, 2019 Ms. Monica Gregoire, Staff Planner Planning Department Town of North Andover 120 Main Street North Andover, Massachusetts 01845 Ref: Initial Stormwater Peer Review North Andover Adult Center 1 Surrey Drive North Andover, Massachusetts Dear Ms. Gregoire 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 Drainage Report and Permitting Plans for the proposed North Andover Adult Center at 1 Surry Drive, North Andover, MA. The plans were prepared for the Town of North Andover (Applicant) by DeVellis Zrein Inc. HW understands that the Applicant is proposing to construct an Adult Center, a parking lot, landscaping improvements, a stormwater management system, and new utility infrastructure. The project proposes to redevelop a 1.5-acre area comprised of multiple lots that currently contain two existing 2-family homes. There are no waterways or wetlands on-site. The area is not associated with any Natural Heritage & Endangered Species Program areas and is outside of the FEMA 100-year flood zone. The following documents and plans were received by HW: • Letter Authorization from the Sutton Street Redevelopment, LLC for applications to the Planning Board, dated May 28, 2019; • Special Permit Site Plan Review Application; • Common Driveway Special Permit Application; • Planning Board Application for Special Permit; • Property Deeds; • Drainage Report and Stormwater Management Plan (73 pages) for the North Andover Adult Center located at 1Surrey Street[sic], prepared by DeVellis Zrein Inc., dated May 24, 2019, which includes: o Drainage report narrative which includes an executive summary, existing conditions, proposed conditions, methodology and design criteria for stormwater management; DEP Stormwater Management Standards; and Operation and Maintenance Plan; o Figures which include a SCS soil map, pre-development watershed plan and post- development watershed plan; o Stormwater Management Report Checklist; i--lor-sleyWiittert.corra Horsley Witten Group, Vnc. Town of North Andover July 10, 2019 Page 2 of 8 o Existing conditions HydroCAD model results for the 1-inch and the 2-,10-, and 100- year storm events; o Proposed conditions HydroCAD model results for the 1-inch and the 2-,10-, and 100- year storm events; o Supplemental Stormwater Management Calculations; o Long Term Best Management Practices O&M Plan (includes Construction Phase Best Management Practices); o Test Boring Logs; and o TSS Removal Calculations. • Site Development Plans, North Andover Adult Center, 1 Surrey Street [sic], North Andover, Massachusetts, prepared by DeVellis Zrein Inc., dated May 28, 2019, which include: o Cover Sheet o Existing Conditions Plan (The Morin-Cameron Group, Inc.) o Layout and Materials Plan C-1 o Grading and Utility Plan C-2 o Planting Plan C-3 o Site Details Sheet C-4 o Site Details Sheet C-5 o Site Lighting SL-1 • North Andover Adult Center Architectural Plans, 500 Sutton Street, North Andover, Massachusetts, prepared by Catlin + Petrovick Architects, PC, dated May 30, 2019, which include: o First Floor Plan A1.0 o Second Floor Plan A1.2 o Attic Floor Plan A1.4 o Roof Plan A1.5 o Elevations A2.0 o Elevations A2.1 Stormwater Management Design Peer Review HW offers the following overall comments concerning the stormwater management design as per the Massachusetts Stormwater Handbook (MSH) dated February 2008, the North Andover Stormwater Management and Erosion Control Regulations (Stormwater Regulations) adopted February 5, 2011, and the North Andover Stormwater Management and Erosion Control Bylaw (Bylaw). The comments below correlate with the MSH standards and where the more stringent Town requirements are applicable additional comments are noted. The development is increasing impervious surfaces and therefore has been evaluated as being new development. 1. Standard 1 states that no new stormwater conveyances (e.g. outfalls) may discharge untreated stormwater directly to or cause erosion in wetlands or waters of the Commonwealth. I I:AProjects\2015\Ib065 N Andover On-Ca ll\I 8065K North Andover Adult CenterAReports\190710_Ist Stormwater Peer Review_I Surn Drive Adrdt Center.docx Town of North Andover July 10, 2019 Page 3 of 8 a. The Applicant has analyzed the existing and proposed stormwater discharge rates from the project site at the property boundaries. HW notes that there are some minor discrepancies between the pre- and post-development watershed boundaries of the 1 Surrey Drive application and the 505 Sutton Street application (review recently completed by HW on July 1, 2019). HW recommends that the watershed boundaries under existing and proposed conditions be coordinated between the two projects to the extent possible. b. The Applicant will also be discharging a majority of the proposed flow towards the municipal drainage system on Surrey Drive. To verify that the outlet of the municipal system will not cause erosion in waters of the Commonwealth, HW recommends that the Applicant show the locations of the municipal drainage system on the plans, provide a narrative describing where the municipal system currently outlets and document that no erosion is currently occurring at the final discharge point. 2. Standard 2 requires that 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 provided calculations for the 2-year, 10-year and 100-year, 24- hour events for pre-and post-development conditions. However, per the North Andover Stormwater Regulations, the 0.5-inch storm and the 25-year, 24-hour event calculations also need to be included. Also, the depths of rainfall used for each event shall be as described in the North Andover Stormwater Regulations under Section 7.2 B.b. Specifically noting that the 100-year rainfall amount is 8.6 inches over 24 hours. b. Per North Andover Stormwater Regulations Section 7.2 B.i, pervious lands onsite "shall be considered to be in good condition regardless of existing conditions existing at the time of computation". HW recommends that the Applicant update pervious cover to be in `Good' condition in the HydroCAD modeling calculations for pre- development conditions. c. The Existing Watershed Map provided by the Applicant does not show topography extending to the south (e.g., into 19 Surrey Drive), HW is not able to confirm if there is any off-site drainage from adjacent properties currently being managed onsite. HW recommends that the Applicant confirm the drainage areas under existing conditions. d. The time of concentration (Tc) value utilized for the EX-1 drainage area was assumed to be 6 minutes. HW recommends that the Tc flow path be shown on the Existing Watershed Map and calculated, it appears that the lawn area may have a Tc value longer than 6 minutes. e. It is not clear from the Proposed Watershed Map how the Applicant delineated the subwatersheds or which portions are pervious or impervious. HW recommends that the Proposed Watershed Map include the proposed contours and shading or hatching of areas of impervious cover. Based on the information provided on the Layout and Materials Plan and Planting Plan, it appears that the amount of pervious area is closer to 0.3 acres as compared to the 0.4 acres provided in the HydroCAD modeling calculations. HAP rojects\2018\18065 N Andover On-Ca ll\I8065K North Andover Adult CenterAReports\190710_1st Stormwater Peer Rev iecv_1 Sum, Drive—Adult Center.docx Town of North Andover July 10, 2019 Page 4 of 8 f. Under proposed conditions, the Applicant has indicated that the stormwater runoff from the proposed building roof will be collected via a pipe and directed to a rain garden system. HW recommends that the Applicant provide a detail of the roof leaders and means to overflow if the rain garden system backs up. g. The Applicant is showing the use of three rain gardens onsite: two to collect overland flow from the parking lot and another to manage roof runoff. For those collecting runoff overland, it is not clear how the water is being directed to the curb openings and into the rain garden. Also, there does not appear to be any pretreatment provided. HW recommends that the Applicant provide a plan-view detail for these rain gardens showing pretreatment as required by Standard 3 and the MSH, Volume 2, Chapter 2. For the rain garden collecting roof runoff, there are no invert elevations provided for the flared end sections. h. The Applicant is proposing the use of a subsurface infiltration/detention system to manage a portion of the site. HW recommends that the Applicant clarify the following: i. The Applicant is using an exfiltration rate of 0.27 in/hr, which is consistent with a Hydrologic Soil Group (HSG) C soil. The test pit at the proposed subsurface system indicates that soils are of a sandy loam and sandy loam gravel, which are consistent with HSG B soils. As noted in the MSH, Volume 3, Chapter 1, Page 13, the Applicant should use the HSG group based on test pit data at the actual site in place of the NRCS data provided. ii. The Applicant has not provided elevations of the 12-inch header pipe or the connecting pipes on the plan or in the detail. The outlet elevations of the subsurface system should be clearly labeled on the plans and details. iii. The Applicant has indicated that the outlet invert of the 8-inch pipe (presumably between DMH 6 and DMH 7) is 158 as noted in the HydroCAD model. However, the outlet invert appears to be 157.6 on the site plan. The HydroCAD model should be revised to reflect the elevations proposed in the plans. iv. The subsurface system detail provided on Sheet C-5 does not include information on minimum depth between ground and top of the proposed subsurface system or the proposed elevation at the bottom of the system, both which are required to verify the elevations used in the HydroCAD modeling. i. The Applicant is proposing the use of Stormceptor STC 450i for four catch basins. However, there are no design calculations provided showing that this model has adequate capacity for the contributing drainage areas, including the water quality flow rate calculations. HW recommends that the Applicant provide these design calculations in its drainage report for each of the four proposed proprietary catch basins. j. The Applicant has conducted soil evaluations within each of the subsurface systems and has provided the soil logs in Appendix C of the drainage report. HW requests that the surface elevations of the test pits within the infiltration systems be added to ITAPro_jects\2018\18065 N Andover On-CalI\I8065K North Andover AClult CenterAReports\190710_1st S tot nmater Peer ReN ievv_I SurtY Drive Adult Center docx Town of North Andover July 10, 2019 Page 5 of 8 the test logs. HW recommends that the Applicant verify that it is providing adequate separation to groundwater from the bottom of the stone. Furthermore, it is not clear why the Applicant has chosen a lower infiltration rate than the rate associated with the soil type documented in the test pits. 3. Standard 3 requires that the annual recharge from post-development shall approximate annual recharge from pre-development conditions. a. In Appendix B of the Drainage Report, the Applicant has provided calculations to address recharge as required by the MSH and Section 7.2 C of the North Andover Stormwater Regulations. HW recommends that the Applicant use the total impervious area within the site under post-development conditions,_not only the increase in total impervious area. b. The Applicant has not provided the draw down calculations for the subsurface system. If the subsurface practice is intended for infiltration, the proposed system must be able to drain fully within 72 hours as required by Standard 3. HW recommends that the Applicant provide the required calculations and verify whether the system will be able to drain within 72 hours. c. Under the MSH Volume 3, Chapter 1, page 27, the Applicant is required to direct no less than 65% of the site's impervious cover to the practices intended to infiltrate the required recharge volume. Based on the Applicant's HydroCAD modeling reports, it appears that of the 1 acre of impervious area proposed onsite, 0.4 acres is directed to the proposed subsurface infiltration/detention system while the remaining 0.6 acres will drain directly to Surrey Drive and the municipal system. HW recommends that the Applicant adjust the required recharge volume as noted or direct more runoff to infiltration systems. 4. Standard 4 requires that the stormwater system be designed to remove 80% Total Suspended Solids (TSS) and to treat 0.5-inch of volume from the impervious area for water quality. a. TSS removal calculations are provided in Appendix B of the Drainage Report include the use of street sweeping for TSS removal credit. In the MSH, Volume 2, Chapter 1, guidance states that a removal rate of 5% requires quarterly cleaning using one of three types of sweepers. However, in the Applicant's Operation and Maintenance Plan on Page 28 of the Drainage Report, the Applicant suggests cleaning on a semiannual basis. In addition, the Applicant states that hand sweeping and hand held leaf blowers can be an alternative to street sweeping. HW recommends that the Applicant discuss with the Town the recommended O&M procedures and confirm whether a street sweeping credit is applicable for TSS reductions. b. The TSS calculations provide an assumed TSS reduction for the proposed proprietary devices (Stormceptor STC 450i). HW recommends that the Applicant provide supporting calculations from the manufacturer to ensure that the TSS reduction is adequate to meet Standard 4. Furthermore, MassDEP has provided guidance stating that when the STC4501 is utilized as an inlet catch basin only 25% TSS removal is accepted practice. HW recommends that the Applicant revisit the proposed stormwater treatment practices. I1:Aprojects\2018\18065 N Andover On-Cal 1\18065K North Andover Adult CcnterAReports\190710__I st Stornwater I'm Review_I Sum, Drive Adult Center.docx Town of North Andover July 10, 2019 Page 6 of 8 c. The Applicant has provided TSS reduction for one treatment train (for subwatershed PR-1 B), but has not provided a calculation for subwatershed PR-1A. HW recommends that the Applicant provide the TSS calculations for the catchment areas which include driveways and parking areas. d. As noted above in comment 2a, HW recommends that the Applicant provide the analysis for the 0.5 inch storm as required under the North Andover Stormwater Regulations under Section 7.2B.b. 5. Standard 5 is related to projects with a Land Use of Higher Potential Pollutant Loads (LUHPPL). a. The proposed development is not considered a LUHPPL therefore, Standard 5 is not applicable to this project. 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 within a critical area, Zone II or an IWPA area and therefore Standard 6 is not applicable to this project. 7. Standard 7 is related to projects considered Redevelopment. a. The proposed development is considered a new development with an increase of impervious area, therefore Standard 7 is not applicable. 8. Standard 8 requires a plan to control construction related impacts including erosion, sedimentation or other pollutant sources. a. On Sheet C-1, the Applicant appears to be showing silt soxx placed at the limit of work on the north west and a majority of the south side of the limit of work, with the exception of the limit of work located within the 505 Sutton Street Development. A detail is provided on Sheet C-4. HW recommends that the Applicant clarify in the legend the different line types shown for limit of work and limit of work with silt soxx. b. The Applicant mentions tree protection and silt fence in the O&M plan on page 30; however, these sediment and erosion control measures are not shown on the plans. HW recommends that the Applicant confirm the location of these items on the plans. c. In the Drainage Report, under Section 5, the Applicant states that in regard to Standard 8, additional coordination is necessary to determine the sediment and erosion control measures with the adjacent development, 505 Sutton Street. Also, in the O&M plan on page 30 the Applicant states that during construction the contractor shall present a plan for vehicle entrances and washout areas. HW recommends that the Applicant provide an erosion and sediment control plan as outlined in the North Andover Stormwater Regulations under Section 8.1. The plan should include, if applicable, phasing of work with the 505 Sutton Street development, particularly at the shared limit of work area. HW recommends that the plan address: materials and methods for protecting the municipal drainage system on Surrey Drive, protecting trees to remain in the right-of-way on Surrey Drive and Sutton Street, locations and details for construction entrances and washout areas, locations and details for sediment/material stockpiles, dust control and other items as required by this standard. II:AI'rojects\201b\I 8065 N Andover On-Ca ll\I8005K North Andover Ado It Ceti terAReports\190710_Ist Storrnwater Peer Rev iew_I Sung Drive Adult Center.docx Town of North Andover July 10, 2019 Page 7 of 8 9. Standard 9 requires a long-term operation and maintenance plan shall be developed and implemented to ensure that stormwater management systems function as designed. a. In the O&M Plan provided on page 28 of the Drainage Report, the Applicant refers to the manufacturer's specifications for cleaning, but does not reference the attachment. Further, the Applicant states that the 'water quality units will be cleaned during the same schedule as the catch basins'. HW recommends that the Applicant clearly state the frequency of cleaning as required by the manufacturer's specifications or recommendations. Also, the Applicant should specify what equipment is required for cleaning these units. The manufacturer states that maintenance is performed with a standard vacuum truck, whereas typical catch basin cleaning can be done with clamshell buckets. b. The Applicant does not specify the frequency for inspection and/or maintenance for the proposed rain gardens. Further, many of the maintenance activities outlined in the MSH, Volume 2, Chapter 2 for rain gardens and bioretention areas are not discussed here, such as vegetation management or the repair of eroded areas. HW recommends that the Applicant clarify the O&M procedures for rain gardens. c. The Applicant has outlined the O&M for the pervious patio pavers. The pavers are not shown on the plans. The O&M states that that a leaf blower be used at least twice a year for cleaning of debris. HW recommends that the Applicant also address the activities and equipment potentially required if there is ponding, weeding or a covering of the paver joints. d. The Applicant states that the subsurface detention/infiltration system can be accessed by the manholes at the corner of the system. However, these manholes are not within or in-line with the system for proper jetting or vacuuming. HW recommends that clean out ports for the proposed subsurface system should be included, both in the plan and on the detail, with appropriate labels. Also, the Applicant should also outline the timeframe for inspections and cleanouts in the O&M Plan. e. The Applicant has provided a long-term O&M Plan in the Drainage Report. The O&M Plan should be a standalone document and include a simple sketch to clearly indicate the location of all stormwater practices to be inspected as well as locations for snow storage. HW recommends that the Applicant include a simple sketch that will be provided to the property owner. f. The Applicant has not provided an inspection and maintenance schedule with routine and non-routine tasks to be performed of the systems as required by Section 9.1A of the North Andover Stormwater Regulations. g. HW recommends that the property owner sign the O&M Plan in accordance with the North Andover Stormwater Regulations. 10. Standard 10 requires that an Illicit Discharge Compliance Statement be provided. a. The Applicant provided an Illicit Discharge Compliance Statement to be signed by the owner on page 19 of the Drainage Report. HW recommends that the illicit discharge statement be signed by the property owner prior to land disturbance. I I:A Project s\20I S\I8065 N Andover Orr-Ca Ih18065K North Andover Adult Center\Reports\190710_Ist Stormwater Peer RePlevv_I Sung Drive Adult Center.docx Town of North Andover July 1O. 201Q Page 8of8 11. Miscellaneous Comments: e. HVV has noted the following inconsistencies in the Checklist for 8tornovvater Report in comparing itto the Applicant's Drainage Report: i. The Applicant has not noted the method they are using tosize the infiltration BMPe (page 2J). ii. The Applicant has stated that runoff from all impervious areas at the site are discharging to the infiltration BMP. However, only e portion of the site (oubvvaterohedPR-1A) ia draining tu the proposed subsurface detention/infiUrotinneyetenn. iii. The Applicant has stated that aTK8OL exists and that documentation has been provided to address the TMOL (page 25). However, Do such discussion o[documentation ie provided in the Drainage Report. b. HVV noted that some drainage pipe diameters and materials were not shown on the plan. HVV recommends that the Applicant provide e drainpipe schedule and calculations showing that the pipes have adequate capacity to convey the proposed f|nvvo. c. The Applicant should clearly identify the locations of seeding and provide callouts for proposed locations of trees, plants and shrubs, verifying that that all plants are native to Essex County. � � d. The drainage report and plans refer to 'Surrey Street' in several locations. The Applicant should revise these documents to note 'Surrey Drive' as shown on the � � existing conditions plan. . Conclusions HW recommends that the Planning Board require that the Applicant 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, ConnnnoDvvao|th of Massachusetts |avvu` and federal regulations � oo applicable to this project. P|eaeeoontautJaOetBernordoat774-413-2S8QaXt202orat jbernardo@horsleywitten.com if you have any questions regarding these comments. Ginoar8|y. � H{}R8LEYVV|TTEN GROUP, INC. Janet Carter Bernardo, P.E. Senior Project Manager � HAP"ojrum2o|m|mm5m Andover On-Ca o\/mm5xwwm Andover xJukc,oxanu;vns\|m7)o_|stamnounm Peer m vie n_| ooxv