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River Islands Development at Lathrop November 2020 Final Phase 2 Sewer Technical Report Rev 1 #6520 Table 6-3: Sewer Collection Area C2— Land Uses, ADWF, and PWWF Land Use Area C2 Sewer Flow Average Dry Total No of DU Factor Weather Flow Land Use or Acres (GPD/du or ac) (GPD) Low Density Residential (per DU) 931 200 186,200 Medium Density Residential (per DU) 602 180 108,360 High Density Residential (per DU) 0 170 0 Commercial (per acre) 0 590 0 Industrial (per acre) 0 355 0 Parks (per acre) 37 55 2,036 Schools/ Institutional (per acre) 19 245 4,731 Total Area C2 Average Dry Weather Flow 301,327 Total Area C1 Average Dry Weather Flow 208,082 Total Area C1 + C2 Average Dry Weather Flow 509,409 Peaking Factor 2.29 Peak Wet Weather Flow' 1,168,388 Notes: 1. PWWF shown is based on the ADWF from areas C1 and C2 conveyed to the proposed sewer lift station LS- C2 6.3.2 Sewer Lift Station C2 (LS-C2)— Preliminary Firm Pumping Capacity Requirements Under normal operating conditions, PWWFs from collection areas C1 and C2 will be conveyed to the proposed sewer lift station C2. The firm pumping capacity for lift station C2 should be 1,168,388 GPD or 811 GPM. Per Appendix H in the City Standards, when design flows exceed 1.0 cfs (or 450 GPM), a low flow pump designed for 5% to 10% of the total design flow should be provided and operated as the lead pump. For the proposed sewer lift station C2, the low flow pump should be designed for 41-81 GPM. Table 6-4: Sewer Lift Station Area C2 (LS-C2)— Preliminary Firm Pumping Capacity Requirements Parameter Pumping Capacity Low Flow Pump Capacity 41-81 GPM Preliminary Required Firm Pumping Capacity 1,168,388 GPD or 811 GPM 6.4 Sewer Collection Area 131 — Preliminary Steady State Results 6.4.1 Sewer Collection Area B1 —Land Uses,Average Dry Weather Flows, and Peak Wet Weather Flows Sewer Collection Area 131 is proposed to be located in the center of Phase II near Lakes 20 &21. Area 131 is bounded by Collection Area Al in the North, Collection Area B2 in the east, the Paradise Cut in the south and Collection Area C1 in the west. 131 is approximately 550 acres composed of comprised mainly of low, medium and high density residential units and some parks and a school. Table 6-5 lists the total number of dwelling units or acreage of each land use in collection area B1, and the ADWF in gallons per day. The total PWWF generated from sewer collection area B1 and conveyed to the proposed sewer lift station B1 is approximately 1,424,966 GPD. See Figure 6-1 for the PWWFs and minimum required pipe sizes for collection area B1. 23