Draft Project Impact Report - Boston Redevelopment Authority

Exeter Residences/888 Boylston
Existing Conditions
Proposed Conditions
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Infrastructure.docx
In Exeter Street, the stormwater drainage system is owned and managed by the
BWSC. A 12-inch northwestern flowing stormwater main combines with a 20-inch
southeastern flowing stormwater main at the intersection of Blagden Street at Exeter
Street. The resulting 18-inch drain pipe is routed to a collector drain in Dartmouth
Street and is eventually directed to an outfall at the Charles River.
A 12-inch stormwater drain is located in Boylston Street and flows northeasterly.
This drain line increases to a 33x39-inch stormwater main before the intersection of
Boylston and Fairfield Streets where it discharges to a 60x72-inch combined sewer.
From here the flow gets carried northward until it discharges dry weather and lower
intensity flows to the West Side Interceptor (WSI). During high wet weather flow
events, this line overflows to a 36x48-inch combined sewer line that continues to
carry flow northward to the Boston Marginal Conduit (BMC) located beneath
Storrow Drive.
A 48x100-inch stormwater drain, which flows southwesterly in Boylston Street,
combines with the 33x39-inch sanitary line at the siphon chamber at the intersection
of Boylston and Hereford Streets where it discharges dry weather and lower
intensity flows to the WSI. During high wet weather flow events, this line overflows
to an 84-inch combined sewer line that continues to carry flow northward to the
BMC located beneath Storrow Drive.
Due to existing on-site constraints a below grade stormwater recharge system will be
located in Exeter Street within the public way. Approximately 65 precast concrete
galleys will be constructed to provide a total stormwater recharge volume of
approximately 3,500 cubic feet. In an effort to address the goals of the Groundwater
Conservation Overlay District, the recharge system will be located on Exeter Street
where it can supplement groundwater elevations in the proximity of the Lenox Hotel
and Boston Public Library. The recharge system is sized for the equivalent 1-inch
roof runoff from both Exeter Residences and 888 Boylston, although Exeter
Residences will physically supply the runoff to this system. Specifically, the roof
runoff from Exeter Residences will discharge directly to the below grade system
which will also include overflow connections to the existing 12-inch and 20-inch
stormwater mains in Exeter Street to accommodate for high flow conditions. Figure
6-1 depicts the schematic design of the recharge system along Exeter Street.
As discussed previously in the NPC/PNF, roof runoff from 888 Boylston will be
discharged to the existing 12-inch main in Boylston Street since there is no physical
connection to the proposed recharge system in Exeter Street. Figure 7-2 contained in
the NPC/PNF depicts the conceptual utility plan along Boylston Street.
Infrastructure Systems 6-2