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B. Proposed Volume Reduction Best Management Practices (BMPs) <br /> Proposed infiltration/bio-filtration areas are shown in Appendix A. <br /> Generally, volume reduction is proposed through the following measures: <br /> Large infiltration and/or filtration basins in select locations of extended street <br /> boulevards: <br /> • West side of Asbury Street bordering the Northwestern College property. <br /> • East side of Ridgewood Road north of Edgewater Avenue. <br /> • West side of Ridgewood Road between Edgewater Avenue and Glen Hill <br /> Road. <br /> Depending on the infiltration capabilities of the soils, the basins may utilize <br /> underground filtration cells with perforated pipe to assist drawdown. <br /> Residential boulevard infiltration/bio-filtration basins or rain gardens: <br /> homeowners will have the option of placement of a small basin with a curb cut in <br /> their street frontage and are subsequently responsible for maintenance. The City <br /> will offer shrub and plug plantings at the discretion of the homeowners. The <br /> boulevard basins offer the homeowner the opportunity to participate in the <br /> treatment of street runoff that eventually reaches the Lake Johanna. <br /> If BMPs (rain gardens, infiltration basins, filtration basins) are constructed in one third <br /> of the boulevards in conjunction with the large infiltration/filtration basins listed above, <br /> up to 33% of the RCWD storm water treatment requirement would be accomplished in <br /> the neighborhood itself. <br /> C. Constructed Basin in Johanna Marsh Parkland <br /> A neighborhood treatment basin constructed within the upland area of the Johanna Marsh <br /> parkland is proposed to meet the balance of the RCWD treatment requirement. Two <br /> options are recommended for further exploration. <br /> Option 1: Biofiltration Basin <br /> The construction of a large biofiltration basin would be similar in construction to the <br /> smaller-scale basins proposed in the neighborhood. Low-maintenance plant material <br /> suited to a wetter environment is recommended. Soil borings taken in January 2012 <br /> indicate no presence of ground water in the neighborhood. However, there are concerns <br /> about a high groundwater table within the marsh area. Further soil exploration and <br /> wetland delineation is needed in order to determine the feasibility of installing a bio- <br /> infiltration basin. <br /> Option 2: Constructed Wetland <br /> Due to the possibility of a high ground water table and wetland conditions, consideration <br /> is being given to a constructed wetland for storm water treatment. A constructed wetland <br /> is a treatment system that uses natural processes involving wetland vegetation and soils to <br /> improve water quality. These systems also provide plant and animal habitat. <br /> 9 <br />