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HomeMy WebLinkAboutConsultant Review - 1018 OSGOOD STREET 11/6/2012 Eggleston Environmental November 6, 2012 North Andover Planning Board 1600 Osgood Street North Andover, MA 01845 Attn: Judy Tymon, Town Planner RE: 1018 Osgood Street Watershed Protection District Applicability Dear Ms. Tymon and Board Members: I am in receipt of the October 19, 2012 Special Permit Application Packet for the proposed Dunkin Donuts project at 1018 Osgood Street and, per your request, have reviewed the request for determination of Watershed Protection District applicability included with the application packet. According to the Town's zoning map, the Lake Cochichewick drainage basin boundary is located just offsite to the north of the subject property; hence the entire parcel is included in the Watershed Protection District. The request letter from Mark Gross, P.E. of NMF Design Consultants, Inc. states that the proposed project should not be subject to the requirements of the Watershed Protection Zone on the basis that the on-site wetlands are not tributary to Lake Cochichewick and the drainage from the site will not be conveyed to the lake. My comments on this request are outlined below: 1. Based on surface topography, the southwest portion of the lot (Area IS on the pre-development drainage plan) drains in a southerly direction (toward Osgood Street and the lake), while the remainder of the lot drains toward the small bordering vegetated wetland (BV W) in the northeast corner of the lot. 2. The September 15, 2012 memorandum from Epsilon Associates submitted in support of the request specifically addresses the drainage from the onsite BVW, not the site as a whole. It is also lacking in the detail necessary to substantiate the findings, specifically maps or figures showing the offsite wetlands and the drainage structures referenced in the memo. I would also point out that the fact that the rim elevation of a catchbasin in Osgood Street is higher than the pipe on the north side of the street does not necessarily indicate the direction of flow; the inverts of the pipe at both locations will determine the slope. 3. If it can be adequately documented that the onsite wetland drains away from the lake (and it appears that it does), I would concur that the portion of the lot that drains to the wetland (Area 2S) should be excluded from the Watershed Protection District since it would be outside of the Lake Cochichewick watershed._ The southwestern portion of the lot, however, is a different matter, as it is topographically still within the Lake Cochichewick watershed. Surface runoff from the lot will likely be diverted into the drainage system in Osgood Street in most storm events; it remains unclear where that drainage goes and whether any 32 0[d Framingham lid Unit 29 Sudbury MA 01776 tel 508.259.1137 fax 866.820.7840 1018 Osgood Street, WPD Applicability 2 November 6, 2012 of it is discharged towards the lake. However, runoff from storm events that exceed the capacity of the drainage system will still drain toward the lake and, more importantly, the groundwater beneath that portion of the property likely also flows toward the lake, since the topography of the land surface usually also determines the general direction of groundwater flow. As stated in Section 4.136 of the Watershed Protection District regulations, they are specifically"intended to preserve the purity of the ground water,the lake and its tributaries;to maintain the ground water table, and to maintain filtration and purification functions of the land". Hence, the protections afforded by the Watershed Protection District regulations should not be waived within the watershed, regardless of whether a portion of the surface runoff is diverted elsewhere. Based on setbacks from a tributary wetland on the south side of Osgood Street, it is my opinion that a portion of the property at 1018 Osgood Street is within the Non-Discharge Zone of the Watershed Protection District. I appreciate the opportunity to assist the North Andover Planning Board with the review of this project, and hope that this information is suitable for your needs. Please feel free to contact me if you or the applicants have any questions regarding the issues addressed herein. Sincerely, EGGLEMN ENVIRONMENTAL z Lisa D. Eggleston, P.E. 1018 Osgood St. Review Nov. 14, 2012 1018 Osgood St Reviews: Watershed Special Permit Determination—Summary of L. Eggleston's review: • Based on topography, SW portion of the lot drains in a southerly direction towards Osgood St. and the lake. Applicant did submit detail that addresses drainage on the site to the wetlands on the rear of the property but did not address drainage on the site as a whole. With more information, she would agree that the rear of the lot drains to the wetlands that are outside of the Watershed Protection District. • SW portion is in the watershed topographically. Groundwater most likely drains to the lake because groundwater follows topography and the Watershed Zoning is designed to also protect groundwater. Also, large storm events that exceed the capacity of any drainage system that is built for the site will also drain towards Osgood St. Civil Review— Summary of Hancock Review: • Parking: Applicant requests a reduction in parking from required 27 spaces to 25. Applicant should provide substantiating information for this request and possibly, empirical data from the existing DD facility. • Fiscal Impact and Community Impact—the applicant is requesting a waiver and should provide a basis for that request. • Parking—the plan does not provide buffering required by section 8.4. Accessible spaces should be located nearest to the entrance. Two-way aisle widths should be 25 ft. No loading area has been designated and the proposed sign does not meet the bylaw. • Utilities are proposed underground but plans show a utility pole on site. • Grade of entrance exceeds 8%. Could be a problem for vehicles entering Osgood St. • Should consider inclusion of grease trap—required by BOH? • Light levels are too low. • Block wall too close to rear property line and too close to proposed drainage system. Traffic Review—Summary • Should conduct traffic counts when school is in session. • Use empirical data from existing DD for traffic counts and parking requirements • Crash data should be expanded to more accurately reflect conditions. —type of crash, time of day, etc. • Should provide trip tracing data • Collect empirical trip generation data and queuing data from existing DD. • Redesign access - One exit, one entrance and allow for delivery and emergency vehicle access. Allow for access for a WB-50 truck. Existing design does not allow for adequate access.. • Queuing at exit driveway from drive-thru is not adequate. Potential for vehicle backup on the site. 1 1018 Osgood St. Review Nov. 14, 2012 Stormwater Management - Summary of L. Eggleston Review • Runoff analysis—needs to be recalculated. A higher infiltration rate was used than what is associated with"C" soils. • Total volume of runoff would not be mitigated. There is a loss of re-charge on the entire site and a diversion of runoff from the wetlands to Osgood St. • Groundwater recharge for entire sites goes to infiltration system in the northeast corner, thus representing a net loss of groundwater recharge to the Watershed. • Proposed system cannot provide the total recharge volume required. • Infiltration systems should have a setback of 50 Ft. from a wetland. • Problems with mounding analysis—needs to be re-done. • The TSS removal calculation for Stormceptor is closer to 50%, not 70%. Also Stormceptor should be located upgradient of the septic system. • Need calculations to determine if Stormceptor and oil/grit separators provided required treatment • Consider alternative for overflow line to detention system. • Roof runoff is unnecessarily diverted into the oil/grit separator. • O&M plan should address maintenance of Stormceptor • LTPPP should cite the fact that the site is within the Watershed. Should also determine if the parcel is within the Zone A. • Snow storage not addressed. 2 Eggleston it November 14, 2012 North Andover Planning Board 1600 Osgood Street North Andover, MA 01845 Attn: Judy Tymon, Town Planner RE: 1018 Osgood Street Stormwater Management Review Dear Ms. Tymon and Board Members: Per your request, I have conducted a technical peer review of the October 19, 2012 Special Permit Application Packet submitted by MHF Design Consultants for the proposed Dunkin Donuts project at 1018 Osgood Street, with respect to Stormwater management. The materials I have received and reviewed to date include the following: ■ October 19, 2012 letter to North Andover Planning Board from Mark Gross, P.E. of MHF Design Consultants Inc. Re: 1018 Osgood Street, Site Plan Special Permit, with attachments. ■ Stormwater Management Report, Map 35 Lot 19, 1018 Osgood St, prepared by MHT Design Consultants, Inc. for JFJ Holdings LLC, and dated October 19, 2012. ■ Proposed Site Development Plans for Map 35 Lot 19, 1018 Osgood St, Sheets 1 through 11 of 11, A7 and A8, prepared by MHF Design Consultants and dated October 19, 2012. This letter is in follow-up to my November 6, 2012 letter regarding the request for determination of Watershed Protection District applicability for this project, in which I indicated that at least a portion of the project site is within the Watershed Protection District. My primary focus in this initial review is on the overall stormwater management approach and design concepts used in the project, as well as its compliance with the Town of North Andover's zoning requirements for Site Plan Review and Watershed Protection Districts, the Massachusetts Department of Environmental Protection (DEP) Stormwater Management Standards and Regulations, and the North Andover Wetlands Bylaw. It is my understanding that a Notice of Intent (NOI) application for the project has been filed concurrently with the Conservation Commission. My review is aimed at assisting both the Planning Board and the Conservation Commission in their respective reviews of the project. The project site is a 28,127 sf parcel located on the northerly side of Osgood Street. It is currently occupied by an uninhabited residential dwelling with a driveway and detached garage. Drainage on the site is overland, with the southern portion of the lot flowing in a southeasterly direction toward Osgood Street and Lake Cochichewick, and the northern 32 Old Frarninagharn Pd Unit 29 Sudbury MA 01776 tel 508.259.1137 fax 866.82.0.7840 1018 Osgood Street, Stomiwater Review 2 November 14, 2012 portion draining toward a small bordering vegetated wetland (BVW) in the northeast corner of the lot. The proposed project is a 2,250 sf Dunkin Donuts coffee shop with associated parking, drive-through, and two new driveways onto Osgood Street. The total area of disturbance associated with the project would be about 25,000 sf, and the total impervious area on the post-development site is approximately 19,000 sf. As proposed, the runoff from most of the parking lot and the exit driveway would be collected in a closed drainage system with deep sump catchbasins and conveyed into a subsurface detention system (with a portion of the flow diverted through an oil/grit separator first), then through a Stormceptor 4501 water quality unit. Discharge would be directly into the Town's drainage system in Osgood Street. Runoff from the drive- through lane and a small portion of the parking lot would similarly be collected in deep sump catchbasins and discharged to a subsurface infiltration system beneath the parking lot, with a portion of the flow diverted through an oil/grit separator first. Runoff from the building roof would also drain through this system. Overflow from the infiltration system would be split, with a portion of the flow discharged toward the onsite wetland and the remainder discharged through the subsurface detention system to the Town's drainage system in Osgood Street. My comments are summarized below: 1. As indicated in my November 6, 2012 letter, at least a portion of the project site is within the Lake Cochichewick watershed and, based on setbacks from a tributary wetland across the street, probably falls within the Non-Discharge Zone of the Watershed Protection District. (It does appear that the site is outside of the Zone A of the watershed, but this should be verified.) The project will require a Watershed Special Permit and will need to maximize onsite recharge of runoff flow, particularly within the watershed area. Stormwater BMPs will also need to be sized for a one-inch water quality volume and provide adequate pretreatment of infiltrated flows. A written certification by a professional engineer stating that the project will not cause any significant degradation in the quality or quantity of water in or entering Lake Cochichewick will also be required. 2. The Site Plan Review regulations of the Town's Zoning Bylaw require that the runoff from the site be mitigated to zero for the 2, 10 and 100-year storm events and the North Andover Wetlands Protection Regulations require mitigation of peak runoff rates for the 1, 10, and 100-year storms, and analysis of peak discharge rates and the volume of runoff on a sub-watershed level. A drainage analysis based on HydroCAD modeling is provided in the Stormwater Report, which indicates there is no net increase in the peak rate of runoff for all of the design storm events However, I believe that the analysis is flawed in that it relies on an unrealistically high rate of exfiltration from the proposed infiltration system. The predominant soils on the site are Paxton fine sandy loams, which are described by NRCS as having slow permeability in the substratum and classified as Hydrologic Soil Group (HSG) C, with relatively low infiltration rates. Both the Rawls (1982) reference cited in the DEP handbook and the custom soil report 1018 Osgood Street, Stormwater review 3 November 14, 2012 included in the Stormwater Report indicate that the design infiltration rate for such soils should be about 0.2 in/hr, not the 1.02 in/hr used in the analysis. Per MHF's own report narrative, the four test pits performed on the site indicated loamy sand and sandy loam consistent with a "C"soil, and the runoff calculations and recharge volume calculations are based on C soils throughout the site. Absent sieve analyses demonstrating the presence (or absence) of finer particles in the soil and/or field testing of saturated hydraulic conductivity (e.g. falling head permeability) in accordance with the DEP Handbook there is no basis for using the higher design infiltration rate. 3. In addition to the question of whether peak rates of runoff are mitigated, it is quite clear from the analysis that the total volume of runoff leaving the project site would not be mitigated under post-development conditions. In the 1-year storm, for instance, the volume of flow discharged to the Town drainage system in Osgood Street would be more than three times the volume that currently drains to Osgood Street, and approximately 30 percent more than what currently leaves the entire site as surface runoff. This is indicative of a loss of recharge on the site overall(despite the fact that the analysis significantly overestimates the volume of flow that is infiltrated during storms), as well as the diversion of runoff flow from the onsite wetland to the Osgood Street drainage system. In addition to impacting the hydrologic regime of the wetland, it has not been determined where the Osgood Street drainage system discharges and what effect the increase in flow might have there. 4. The drainage analysis does not account for tailwater conditions in the Osgood Street drainage system. Since it is unlikely that the Town's system has the capacity to convey flow from the 100-yr event, additional surcharging of the proposed drainage system on this site should be expected. 5. As proposed, groundwater recharge for the entire project site would be provided through the infiltration system located below the northeast corner of the parking lot. Assuming that the northern portion of the lot is located outside of the Lake Cochichewick watershed, this would represent a net loss of groundwater recharge to the watershed. It is also not consistent with the requirements of the Wetlands Bylaw regulations, which require that recharge be provided on a sub-watershed basis. 6. The proposed infiltration system also does not and cannot provide the total recharge volume required by the DEP Standards for the site since the capture area (the area tributary to the infiltration system) represents only about 44 percent of the total impervious area on the site. As is outlined in the DEP Stormwater Handbook, at least 65 percent of the impervious surfaces on a site must be directed to the proposed infiltration BMPs in order for the system to capture sufficient runoff to infiltrate the required recharge volume on an annual basis. The sizing calculations for the recharge structures also need to take into account the capture area. 1018 Osgood Street, Stormtvater Review 4 November 14; 2012 7. The DEP regulations call for stormwater infiltration systems to have a minimum setback of 50 feet from wetlands. The proposed plan provides only a 35-ft setback. 8. Since the proposed infiltration BMP is used to attenuate large storm events, the Stormwater Report includes a mounding analysis as required under DEP Standard 3. The mounding analysis should use a hydraulic conductivity consistent with the Paxton soils instead of medium sand. In addition, the saturated thickness should not be the ESHGW elevation, but rather the difference between it and the bottom of the aquifer. Given that the test pits did not encounter bedrock it is reasonable to assume a saturated thickness of at least 10 to 15 ft. 9. The locations of the soil tests conducted on the site should be shown on the plans. 10. The proposed treatment train for the driveway/parking area at the front of the site is comprised of deep sump catchbasins, an off-line oil/grit separator, and a Stormceptor 4501 unit. The TSS removal calculations assume 70.percent removal by the proposed Stormceptor unit; however verification data to support this rate was not submitted and it is most likely based on the Massachusetts STEP fact sheet that was recalled by DEP in January, 2011. The Stormceptor 4501 is currently certified through the NJCAT TARP Tier I testing program at a TSS removal rate of only 50 percent. 11. While the Stormceptor unit can provide effective pretreatment of pavement runoff, it should be located upgradient of the subsurface detention system. As currently proposed a good deal of the sediment is likely to settle out in the detention system where it is more difficult to remove. 12. Calculations are needed to demonstrate that both the oil/grit separators and the Stormeeptor unit are designed to treat the required water quality volume in accordance with DEP's computational method for determining equivalent peak water quality flow rate. 13. I note that at CB-6 there is only a 0.1 foot offset between the low flow pipe to the oil/grit separator and the overflow line to the detention system. The offsets at DMH-1 and DMH-2 are somewhat greater, but are still going to require a good deal of precision in the installation process in order to ensure the proper distribution of flows. Consideration should be given to alternative methods (e.g. a manhole with an overflow weir) that would provide better control of the flow distribution. 14. Based on the plan, the clean runoff from the building roof is routed through DMH-1, not directly to the infiltration system as is indicated in the model. Hence, a portion of the roof runoff is unnecessarily diverted into the oil/grit separator. 1018 Osgood Street, Storiiiwater Review 5 November 14, 2012 Roof downspouts should be screened to keep out leaf litter, and the runoff should be recharged directly. 15. The O&M Plan should distinguish between the infiltration system and the subsurface detention system and should include maintenance of the Stormceptor unit. 16. The Long Term Pollution Prevention Plan should identify the fact that the site is within the Lake Cochichewick watershed and should reflect the restrictions on landscaping chemicals and deicers associated with that designation. 17. Snow storage on the site needs to be addressed. There appears to be very little room for snow storage outside of buffer zone areas. Once again, I appreciate the opportunity to assist the North Andover Planning Board with the review of this project, and hope that this information is suitable for your needs. Please feel free to contact me if you or the applicants have any questions regarding the issues addressed herein. Sincerely, EGGLESTON ENVIRONMENTAL se Lisa D. Eggleston,P.E. Eggleston Environmental April 3, 2013 North Andover Planning Board 1600 Osgood Street North Andover, MA 01845 Attn: Judy Tymon, Town Planner RE: 1018 Osgood Street Stormwater Management Review Dear Ms. Tymon and Board Members: I am writing this letter in follow-up to my previous (November 14, 2012 and January 7, 2013) comment letters on the above-referenced project. Since that time I have received and commented on(via email)the January 28, 2012 and March 1, 2013 revised plans and calculations submitted by MHF Design Consultants, participated in a meeting with town staff and the applicants' representatives on March 7, 2013 and, most recently, received and reviewed the March 25, 2013 revised plans and Stormwater Management Report. The revised plans address most of my previous comments on the project, and in particular my concern about the separation to groundwater beneath the proposed infiltration systems. My comments on the revised submittal are outlined below: 1. Per my conversation with Chris Tymula today,the invert of the weir in DMH- 1 should be raised to be commensurate with the crown of the 6-inch pipe to the Oil&Grit separator. 2. The plan(Sheet 8) should be clarified to show that all roof drainage drains to Infiltration System#2 and there is no roof drain connection to DMH-2. 3. There are several discrepancies between the design detail for the Lane sand filter and the proposed design configuration; it should be verified with the manufacturer that the filter can receive inflow from both ends (with the clearwell in the middle), and that less than the minimum 60-inch minimum maintenance headspace called for in the detail will be adequate. 4. 1 strongly recommend against putting filter fabric on the bottom of the infiltration systems (as is called for in the design detail), as it can be prone to clogging. 5. Each subsurface infiltration system should have at least two inspection ports/cleanouts. 6. The O&M Plan should include the specific tasks for maintaining the sand filter(e.g. not just reference the manufacturer's instructions), including periodic cleaning of the forebay and replacement of the top inch or so of media when it becomes discolored and/or the rate of filtration slows. (The need to replace the entire depth of media should be less frequent).The sand 32 Old Framingham Rd Unit 29 Sudbury MA 01776 tel 508.259.1137 fax 866.820.7840 1018 Osgood Street, Stornmvater Review 2 April 2. 2013 filter should be inspected after large storms to ensure that it is fully drained within 72 hours. 7. The Erosion& Sediment Control Plan should call for keeping the infiltration systems offline until the site is stabilized. 8. The detail for the construction entrance should specify a minimum of 2-inch stone. Once again, I appreciate the opportunity to assist the North Andover Planning Board with the review of this project, and hope that this information is suitable for your needs. Please feel free to contact me if you or the applicants have any questions regarding the issues addressed herein. Sincerely, EGGLEMN ENVIRONMENTAL r Lisa D.Eggleston,P.E. C: Jennifer Hughes, Conservation Coordinator Eggleston vi t April 18, 2013 North Andover Planning Board 1600 Osgood Street North Andover, MA 01845 Attn: Judy Tymon, Town Planner RE: 1018 Osgood Street Stormwater Management Review Dear Ms. Tymon and Board Members: In follow-up to my most recent (April 3, 2013) comment letter on the above-referenced project, I have received and reviewed the April 4, 2013 revised plans and Operations & Maintenance Plan submitted by MHF Design Consultants. The revised plans satisfactorily address my outstanding comments on the project, with the exception of the following: 1. We are still awaiting confirmation from the manufacturer of the sand filter on the proposed design configuration. 2. In addressing my previous comment#4, MHF has revised the design detail for the infiltration systems to remove the filter fabric, however there is still a note in the detail on Sheet 8 (under Foundation) that indicates that the trench bottom may be stabilized with geotextile fabric at the geotechnical engineer's discretion. The plans should clearly state that fabric is not to be placed on the bottom of the system. Once again, I appreciate the opportunity to assist the North Andover Planning Board with the review of this project, and hope that this information is suitable for your needs. Please feel free to contact me if you or the applicants have any questions regarding the issues addressed herein. Sincerely, EGGLESTON ENVIRONMENTAL R 4� Lisa D. Eggleston, P.E. C: Jennifer Hughes, Conservation Coordinator 32 Old Framingham Rd Unit 29 Sudbury MA 01776 tel 508.259.1137 fax 866.820.7840