HomeMy WebLinkAbout2011-09-06 Planning Board Supplemental Materials (52) Eggleston Environmental
32 Old Framingham Rd Unit 29 Sudbury MA 01776 tel 508.259.1137 fax 866.820.7840
August 24, 2011
North Andover Planning Board
1600 Osgood Street
North Andover, MA 01845
Attn: Judy Tymon, Town Planner
RE: Stormwater Management Review
1780 Osgood Street
Dear Ms. Tymon and Board Members:
Per your request, I have reviewed the May 16, 2011 Site Plan (revised through 8/5/11)
and July 19, 2011 Stormwater Management Report prepared by LJR Engineering for the
proposed modifications at the J. Tropeano, Inc. property at 1780 Osgood Street.
It is my understanding that a Notice of Intent (NOI) application for the project has been
filed concurrently with the Conservation Commission, and that my review is intended to
assist both the Planning Board and the Conservation Commission in their respective
reviews of the project. My primary focus in this review is therefore on the project’s
compliance with the Town of North Andover’s zoning requirements for Site Plan
Review, the Massachusetts Wetlands Protection Act Regulations (310 CMR 10.0), and
the North Andover Wetlands Protection Bylaw (Ch. 178) and Regulations, specifically
with respect to drainage and stormwater management.
The project site is an existing contractor’s storage facility on a heavily disturbed lot, with
wetlands to the east and the MBTA and the Merrimack River to the west. Drainage
appears to be in a westerly direction, toward the river. The proposed project entails the
addition of a small porch roof to the front of the building, and a 50’ x 60’ foot garage
addition, with associated grading, to the side of the existing building. Roof runoff from
both additions would be directed to new subsurface infiltration systems.
My comments are outlined below:
1. The proposed infiltration system for the porch addition is designed to capture and
infiltrate runoff for storm events up to and including the 100-yr design storm,
therefore it should not generate any excess runoff. While it is located within 50 ft
of the wetland, I believe the location is justified by the fact that it is infiltrating
clean roof runoff from an area in similar proximity to the wetland.
2. The infiltration system for the proposed garage addition appears to be undersized.
The design calculations call for 12 Cultec C-100 units to store the runoff from the
10-yr design storm, and the plans show only 6 units in that system. Additional
analysis is needed to evaluate the impact of the excess runoff generated by larger
1780 Osgood Street, Technical Review 2
August 24, 2011
storms, e.g. 100-yr frequency, from the proposed addition and the associated
grading.
3. The proposed project entails fill within the 100-yr floodplain/floodplain district. A
floodplain replication area is shown on the plan, however no compensatory flood
storage calculations were provided in the materials I reviewed. In addition, the
stormwater report appears to overlook the fact that the 100-yr floodplain is a
wetland resource area subject to Conservation Commission jurisdiction.
4. It is not clear why the plan calls for 6-inches of crushed stone in the compensatory
flood storage area.
5. I recommend against the use of filter fabric beneath the proposed infiltration
systems due to the potential for clogging.
6. The infiltration system details indicate the surface cover to be porous pavement. I
do not believe that porous pavement is proposed (or appropriate) for this site.
7. The infiltration systems should be equipped with observation ports to facilitate
ongoing inspections.
8. I recommend the use of straw wattles or staked haybales to supplement the
siltation fence erosion control.
9. Disturbed areas should be re-vegetated following construction.
10. The O&M Plan should address long-term source controls to be used on the
property, including protection of stockpiled materials.
I appreciate the opportunity to assist the North Andover Planning Board and
Conservation Commission 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