HomeMy WebLinkAboutConsultant Review - 100 CHADWICK STREET 1/9/2014 January 9, 2014
North Andover Planning Board
1600 Osgood Street
North Andover,MA 01845
Attention: Ms.Judy Tymon
Town Planner
Reference: Stormwater Review—Eggleston Environmental
Review Letter dated 1-3-2014
McEvoy Field,North Andover,MA
WDG Project No: 1524-C
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Dear Ms.Tymon and Board Members:
We have received Eggleston Environmental's (EE)comments regarding the Special Permit
Application submittal package for McEvoy Field dated December 6, 2013. Below we have listed
EE's comments followed by our response in italics briefly discussing how each item is addressed.
1. In accordance with the Site Plan Review requirements,the Stormwater Management Plan
includes drainage calculations demonstrating that there will be no increase in runoff
from the site under the 2, 10 and 100-year design storm events.
This statement is correct.
2. The proposed project also incorporates low impact development (LID) techniques to
maximize groundwater recharge on the site and to provide water quality treatment of
runoff"to the maximum extent practicable".
This statement is correct.
3. The play surface underdrains should connect to underdrains beneath the bioretention
area,not to the basins themselves as the note on Sheet L-3 suggests.
The note on Sheet L-3 will be corrected to state that the play surface underdrains
will connect to the bioretention area underdrains.
4. The bioretention area detail on Sheet D-4 should show underdrains beneath the system
and the overflow area drain with a direct connection to the underdrains, as well as the
proposed grading for the basin. The underdrains should be in a stone layer beneath the
bioretention soil.
The underdrains, overflow area drains,proposed grading and the stone layer beneath the
bioretention soils will be added to the bioretention detail on Sheet D-4.
5. 1 recommend a bioretention soil mix similar to that specified in the DEP Stormwater
Handbook (40% sand, 30-40% compost, 20-30% topsoil) rather than the loam specified
on Sheet D-4.
50 Cross Strc c,t / Winchcster / Massachusetts / 01890 / USA
(781)756.0001 / 1 (78'1)756.0007 / u/ww.waterfield(lesign.cortl
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The bioretention soil mix identified in the detail on Sheet D-4 will be changed to the mix
specified by the DEP Stormwater Handbook.
6. The 12-inch ponding depth called for on the bioretention system detail is inconsistent
with the spot grades shown on Sheet L-4 (showing a low point of 148.5 in the basins)
and the rim elevations of area drains#1 and 2 (149.0) shown on Sheet D-6.
The detail and spot grades will be modified to correctly identify the design
elevation of the area drain rims as 149.75.
7. The inlet and outlet inverts for area drain#2 are incorrectly listed in the detail on Sheet D-
6 as 138.0. I believe both inverts should be 148.00.
The inlet and outlet inverts for area drain#2 will be correctly listed in the detail on Sheet
D-6 as 148.0.
8. I note that the existing catch basins in Sutton Street are located directly on the drain
line,rather than in an off-line configuration.Hence, any sediment that accumulates in the
catch basins is prone to washout. Rather than adding a new area drain connection to the
existing drain line and a new drain connection to the existing catch basin in Sutton Street
as is proposed, consideration should be given to converting the existing catch basin to a
manhole structure and adding a new off-line catch basin.
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Consideration has been given to converting the existing catch basin to a manhole
structure and adding new offline catch basins as we agree that the existing on-line
catch basin system is not ideal. The existing drainage system to which both the
existing and proposed site outlets is off of the McEvoy Field property and is inside
the Sutton Street right of way.As shown in the Stormwater Report, adding new
catch basins is not necessary to meet the Site Plan Review Stormwater
Management requirements. Virtually no additional sediment will be introduced
into the drain because the area drain is located in a grassy area and there will be
no increase in scour velocity going to the catch basin.. In addition, in order to
prevent sediment in the online catch basins from entering the stormwater system
the Town will prioritize the cleaning of these catch basins as part of their
maintenance schedule.
The costs associated with adding new catch basins to the system and converting
existing catch basins to manholes would require the Town to greatly reduce the
scope of the McEvoy Field project.
9. As indicated on the Stormwater Checklist, this project entails the disturbance of more
than one acre of land and is therefore subject to EPA's NPDES Construction General
Permit (CGP). A draft Stormwater Pollution Prevention Plan (SWPPP) was submitted
with the application. This plan should be finalized in conjunction with the selected site
contractor prior filing of a Notice of Intent under the permit and initiation of work on the
project.
The SWPPP will be finalized once a site contractor is selected and a Notice of
Intent will then be filed with the EPA prior to the initiation of work on the project.
1' I A'7C1 RFIELD DESIGN GROUP., : ,,