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Project Description This project is a development of a 3.17 acre +/- site located on the west side of Orchard Park Road in the Town of West Seneca. The property will be developed with (26) 2-bedroom apartment units and (4) 3-bedroom apartment units. This analysis will also include the recently approved multi-family project at 1130 Orchard Park Road (45 2- bedroom units). The proposed sewer service for this development will connect to an existing 10” Town of West Seneca sewer main the runs along the west side of Orchard Park Road. Node 1 – 1001 Orchard Park Rd (12”): Existing Peak Flow measured (wet weather event) = 2.844 cfs (1.838 mgd)* Proposed Apartments Peak Flow (Flattery’s) = 0.065 cfs** Proposed Apartments Peak Flow (1425 OP Road) = 0.046 cfs** Proposed Total Peak Flow = 2.955 cfs Theoretical capacity of existing 12” pipe @ 0.36% = 2.314 cfs Conclusion: Monitored flows the day following the 0.72” rainfall event exceeded the capacity of the existing pipe 12” sewer. One time during the monitoring period the flow depth exceeded the pipe diameter at Node 1, but at no time during the monitoring period did the flow at any point slow or stall which would have caused a backup or flooding at the manhole. The 12” sewer receives surcharges from a 27” sewer and 36” sewer downstream during high rainfall events. Outside of these events, the 12” sewer has ample capacity to handle the additional proposed total peak flow. I/I mitigation shall be required for the contribution proposed for this project. Node 2 – Orchard Park Rd (15”): Existing Peak Flow measured (wet weather event) = 2.917 cfs (1.885 mgd)* Proposed Apartments Peak Flow (Flattery’s) = 0.065 cfs** Proposed Apartments Peak Flow (1425 OP Road) = 0.046 cfs** Proposed Total Peak Flow = 3.028 cfs Theoretical capacity of existing 15” pipe @ 0.34% = 4.077 cfs Conclusion: The proposed total peak flow is less than the capacity of the 15” pipe, therefore there is sufficient capacity. One time during the monitoring period the flow depth exceeded the pipe diameter at Node 2, but at no time during the monitoring period did the flow at any point slow or stall which would have caused a backup or flooding at the manhole. The 15” sewer receives surcharges from a 27” sewer and 36” sewer downstream during high rainfall events. Outside of these events, the 15” sewer has ample capacity to handle the additional proposed total peak flow. I/I mitigation shall be required for the contribution proposed for this project. Proposed Apartments 10/3/2022 Page 1 of 2 Page 482 of 849