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BMP Descriptions <br />Curb -cut Rain Gardens <br />Curb -cut rain gardens capture stormwater that is in roadside gutters and redirect it into shallow <br />roadside basins. These curb -cut rain gardens can provide treatment for impervious surface runoff from <br />one to many properties and can be located anywhere sufficient space is available. Because curb -cut rain <br />gardens capture water that is already part of the stormwater drainage system, they are more likely to <br />provide higher benefits. Generally, curb -cut rain gardens were proposed in areas without sufficient <br />existing stormwater treatment and located immediately up -gradient of a catch basin serving a large <br />drainage area. Bioinfiltration was solely proposed (as opposed to biofiltration) as the available soil <br />information suggested infiltration rates could be sufficient to allow complete draw -down within 24-48 <br />hours following a storm event (Figure 5). <br />i J <br />Figure 5: Rain garden before/after and during a rainfall event <br />All curb -cut rain gardens were presumed to have a 12" ponding depth, pretreatment, mulch, and <br />perennial ornamental and native plants. The useful life of the project was assumed to be 30 years and <br />so all costs are amortized over that time period. Additional costs were included for rehabilitation of the <br />garden at years 10 and 20. Annual maintenance was assumed to be completed by the landowner of the <br />property at which the rain garden could be installed. <br />Boulevard Bioswale (NSS-El) <br />One option for retrofitting a stormwater <br />BMP within an existing boulevard is a <br />bioswale. This practice is similar to the <br />boulevard rain garden in its orientation <br />and size. Bioswales typically range from 5- <br />30' in length, house a rich native plant <br />community, and are installed between the <br />existing sidewalk and roadway curb (Figure <br />6). Unlike rain gardens, these practices are <br />typically much shallower (1-3" in depth) <br />and have a curb -cut inlet and outlet (Figure <br />6). Although many rain gardens have <br />outlets in the form of underdrains or <br />risers, the bioswale outlet allows for a <br />Figure 6: Right-of-way bioswale installed in New York City (NYC Environmental <br />Protection, 2013) <br />City of Ramsey Stormwater Retrofit Analysis <br />