2021-10-07 SW Permit Amendment Cover Letter - 95 Barrett
4 Allen Place, Northampton, MA 01060 (413) 582-7000 bdg@berkshiredesign.com
Berkshire
Design
Group
October 7, 2021
Doug McDonald
Northampton DPW
RE: Stormwater Permit Amendment
95 Barrett Street
Dear Doug:
Enclosed please find plans and stormwater report in support of a proposed amendment to the existing
stormwater permit that was granted on 7/23/15 for development at 95 Barrett Street in Northampton.
As you know, the owner has proposed a special permit amendment to allow the conversion of garage units that
were built under the original 2015 project permits into residential apartments. As part of this modification,
pavement will be extended into the north end of the central green space to provide additional parking and a
small recycling shed will be constructed. These changes resulted in a small, but significant, increase in
impervious area and additional stormwater management is required.
The proposed plan incorporates a new underground detention basin, constructed of solid HDPE pipe. A simple
outlet control structure is provided and is proposed to discharge to the stormwater quality unit that was built
under the original construction plan. As you noted in our conversation on 10/1/2021, modification of the
stormwater chamber may be problematic. If this is the case, discharge would be moved downstream of the
water quality unit. This change would not impact the routing within the stormwater model, and because the
new detention basin carries only roof runoff, TSS removal would not be impacted.
The enclosed stormwater report is a revision to the original report for the site and demonstrates compliance
with the Stormwater Standards for the site as a whole in the final proposed conditions.
Please do not hesitate to contact me with any questions.
Sincerely,
Berkshire Design Group
Christopher Chamberland, P.E.
Principal