HomeMy WebLinkAbout2013-04-02 Planning Board Supplemental Materials (101) Eggleston Environmental
32 Old Framingham Rd Unit 29 Sudbury MA 01776 tel 508.259.1137 fax 866.820.7840
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. I 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
1018 Osgood Street, Stormwater 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,
EGGLESTON ENVIRONMENTAL
Lisa D. Eggleston, P.E.
C: Jennifer Hughes, Conservation Coordinator