Project Description: The infiltration manholes on Bishop Avenue and Craddock Street introduce a new green infrastructure technology for the Save the Rain Program. Infiltration manholes are similar to dry wells, however, are more substantial and capture a greater volume of stormwater than dry wells. The manhole walls are perforated with rings of 3” holes and open on the bottom to allow stormwater to infiltrate into the surrounding gravel storage and subgrade native soils.
Bishop Avenue and Craddock Street were chosen as the first location for this product because they are located within the high priority CSO 052 area, and because they are narrow streets with utility restrictions that prevent other traditional forms of green infrastructure. These infiltration manholes allow for increased stormwater capture volume in a small space, compared to stone storage alone.
In addition, two catch basins along Bishop Avenue are being separated from the sanitary sewer and being directed to Furnace Brook as part of this project. These catch basins are located within 30 feet of Furnace Brook and the close proximity allows for simple separation. Water quality treatment for the new separated catch basins will be provided via filter inserts that capture street borne debris and an intermediary infiltration manhole.
Infiltration manholes are planned to be used in a much greater frequency in future projects in utility complex areas and are an excellent addition to the Save the Rain Program’s portfolio of green infrastructure technologies. A total of approximately 540,000 gallons of stormwater will be captured annually with these infiltration manholes on Bishop Avenue and Craddock Street.
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