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HomeMy WebLinkAbout2011-07-19 Planning Board Supplemental Materials (13) Eggleston Environmental 32 Old Framingham Rd Unit 29 Sudbury MA 01776 tel 508.259.1137 fax 866.820.7840 July 14, 2011 North Andover Planning Board 1600 Osgood Street North Andover, MA 01845 Attn: Judy Tymon, Town Planner RE: Stormwater Management Review 140 Academy Road at Stevens Street Dear Ms. Tymon and Board Members: Per your request, I have reviewed the June 29, 2001 revisions to the Land Disturbance Permit Application packet prepared by Andover Consultants, Inc. for the above- referenced project. The revised submission incorporates a number of the improvements discussed at our May 24th site visit and subsequent June 3rd meeting with the Applicants. As discussed at the meeting, the project is fully subject to the MA DEP Stormwater Standards under the North Andover Stormwater Management and Erosion Control Bylaw (Chapter 160), even though fewer than five lots are proposed. As also discussed, however, the Planning Board has the right to waive full compliance with any of the standards/requirements on a case- by-case basis, where warranted. With the incorporation of the most recent revisions, I believe that the proposed project complies to the maximum extent feasible with the DEP Standards, and that it will not negatively impact downstream resources. Furthermore, the proposed project also incorporates several improvements to the existing town drainage system that will provide a net benefit to the stormwater management in the area. These include two new deep sump catchbasins with outlet hoods, which will enhance pollutant removal in the system, and replacement/lowering of an existing culvert under Stevens Street to reduce flooding of the roadway in this area. I do have the following comments on the current design: 1. The June 28, 2011 drainage calculations indicate that the roadway in the vicinity of the existing culvert will still be overtopped under large storm (25-yr and greater) conditions, albeit to a lesser extent. Consideration should be given to using a larger pipe with capacity to convey the entire 25-yr storm flow. 2. The project will require an easement for the proposed work on private property, at the spillway outlet of the culvert that is being replaced. 3. The proposed drop inlet should have a beehive grate, similar to the catchbasin being replaced. 140 Academy Road at Stevens St, Technical Review 2 July 14, 2011 4. A detail has been added to the plans showing weep holes in the retaining wall every 50 ft to allow groundwater through and relieve hydrostatic pressure. I do, however, still have concern that no vegetated drainage ways for the upgradient flow are provided, and that the grading is actually toward the house foundations and the driveways. Directing flow onto the driveways is not acceptable, either from a water quality or safety standpoint. 5. The O&M plan calls for the homeowners to keep the culverts clear of blockages, and they are likely to be motivated to do so. It may, however, also be prudent to add trash racks on the upgradient sides of the culverts to prevent sports balls and the like from getting into the culverts. 6. The project entails the disturbance of more than one acre of land and is therefore subject to the EPA’s NPDES Phase II Construction General Permit. The Applicant has filed a Notice of Intent for coverage under the permit, and a Construction Stormwater Pollution Prevention Plan (SWPPP), dated April 21, 2011, was included with the original application packet. The Construction SWPPP should be updated to reflect the recent revisions to the project design, and should also incorporate the Erosion & Sediment Control Criteria (Section 8.2) of the North Andover Stormwater and Erosion Control Regulations, as they include several specific requirements not spelled out in the SWPPP. Given the steep slopes and total area of disturbance proposed on the project site, I also recommend a pre-construction meeting with the contractor to discuss implementation of the erosion & sediment controls and encourage either the Planning Board or the Conservation Commission to consider requiring an independent Environmental Monitor for the project. 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 Lisa D. Eggleston, P.E. C: Jennifer Hughes, North Andover Conservation Commission