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Section 3 - Sanitary Sewer Service Sanitary sewer service for the proposed Seneca Mall redevelopment will be provided by a private sanitary sewer collection system consisting of 8 inch and 10 inch sanitary sewer mains, with manholes installed at all changes in alignment and at appropriate intervals in accordance with Town of West Seneca and Erie County standards. The proposed sanitary sewer system has been designed to accommodate both the initial phase of development and future build out of the site. Individual proposed and future buildings within the redevelopment will be connected to the private sanitary sewer system through separate 6 inch SDR 35 PVC sanitary service laterals installed at a minimum slope of 1.0 percent. The sanitary collection infrastructure has been designed to provide adequate capacity for the anticipated wastewater flows associated with the ultimate development of the property. Design Parameters 0.1 gal/d/sf x 241,000 sf = 24,100 gpd 500 gal/d/wind. x 4 wind. = 2,000 gpd 25 gal/d/seat x 222 seats = 5,550 gpd 0.1 gal/d/sf x 120,025 sf = 12,003 gpd 15.0 gal/d/Employ. x 5 Employ. = 75 gpd 35 gal/d/seat x 500 seats = 17,500 gpd Total Sanitary Sewer Demand = 61,228 gpd 61,228 gpd * 3.93 = 240,462 gpd *use peaking factor of 3.93 The hydraulic loading rate is per “Design Standards for Intermediate Sized Wastewater Treatment Systems” 2014, NYSDEC. See Appendix A for detailed Calculations Section 4 - Storm Sewer Service Existing site drainage generally flows to two primary drainage areas. The western portion of the site drains toward Slade Avenue, while the remainder of the site is collected by an existing network of catch basins that ultimately discharge through a large storm sewer outlet located near the north central portion of the site. This outlet conveys runoff directly to Cazenovia Creek. Stormwater runoff generated by the proposed redevelopment will be collected and conveyed through a stormwater management system consisting of a wet pond, catch basins, yard drains, manholes, and smooth interior HDPE storm sewer pipe. The proposed stormwater management infrastructure has been designed to accommodate the ultimate full build out of the site and will provide the necessary conveyance, water quality treatment, and peak flow attenuation for future development phases. As a redevelopment project, the site is required to provide Water Quality Volume (WQv) treatment for 25 percent of the disturbed impervious area and 100 percent of any new impervious area in accordance with NYSDEC requirements. The existing site contains approximately 47.80 acres of impervious cover, while the proposed redevelopment will result in approximately 47.0 acres of impervious cover which includes the widening of Slade Ave and Orchard Park road. Since the project does not create any new impervious area, all proposed improvements are classified as disturbed impervious area and are therefore subject to the 25 percent WQv treatment requirement. Because no new impervious cover is being created, no Runoff Reduction Volume (RRv) is required for the project. The proposed wet pond provides 100 percent of the required Water Quality Volume (WQv) treatment for the redevelopment and also provides peak flow attenuation. Discharge from the wet pond is controlled West Seneca Exchange 07/20/2026 2 of 3 Page 675 of 1174