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6. Capacity Analysis 6.1 Existing 4″ PVC service connection Full-flow capacity of the 4″ PVC service (n = 0.013) at the minimum building-sewer slope of 1/8″ per foot (S = 0.0104 ft/ft): Diameter / area / R 4″ (0.333 ft); A = 0.087 ft²; R = 0.083 ft Full-flow capacity ≈ 0.19 cfs = 87 gpm = 126,000 gpd Velocity (full) 2.2 ft/s (≥ 2.0 ft/s minimum ✓) Peak demand of ≈ 2.0 gpm is about 2% of the 4″ service’s minimum full-flow capacity. The existing service has ample excess capacity, with more than 85 gpm to spare. At a steeper (typical) slope of 1/4″ per foot the capacity rises to ≈ 123 gpm. 6.2 Existing 15″ public sewer main At the minimum design slope for a 15″ sewer (S = 0.15%), and using a conservative lined effective diameter (n = 0.011), the 15″ main’s full-flow capacity is on the order of: Full-flow capacity (minimum slope, conservative) ≈ 1,100 gpm ≈ 1.6 MGD Velocity (full) ≥ 2.0 ft/s ✓ The 15″ main already conveys the facility’s current flow as part of a much larger tributary area. Because the project adds no sanitary demand, it places no additional load on the main. Even at the conservative minimum-slope capacity above, the facility’s peak demand is a negligible fraction (well under 1%) of the main’s capacity. 7. Conclusions ● No increase in sanitary demand. The addition adds building area only; occupant loads and operations are unchanged, so demand remains ≈ 730 gpd average / ≈ 2.0 gpm peak. ● 4″ service is adequate. Minimum full-flow capacity ≈ 87 gpm; peak demand uses ≈ 2%, leaving substantial excess capacity. ● 15″ main is adequate. Capacity on the order of 1,100+ gpm; the main already conveys the facility’s flow and receives no additional load from this project. ● No upgrade required. The existing 4″ service and 15″ public main have adequate capacity for the facility as proposed. Appendix A — Representative Unit Design Flow Rates Representative values for occupancy-based estimating, consistent with the referenced standards. Sanitary Sewer Capacity Analysis • 4350 Seneca Street Building Addition • Page 4 Page 47 of 84