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River Islands Development at Lathrop November 2020 Final Phase 2 Sewer Technical Rei3ort Rev 1 #6520 Table 6-5: Sewer Collection Area B1 — Land Uses, ADWF, and PWWF Land Use Area B1 Sewer Flow Average Dry Total No of DU Factor Weather Flow Land Use /Acres (GPD/du or ac) (GPD) Low Density Residential (per DU) 876 200 175,200 Medium Density Residential (per DU) 1,150 180 207,000 High Density Residential (per DU) 1,562 170 265,540 Commercial (per acre) 0 590 0 Industrial (per acre) 0 355 0 Parks (per acre) 57 55 3,130 Schools/ Institutional (per acre) 0.0 245 0 Total Area B1 Average Dry Weather Flow 650,870 Peaking Factor 2.19 Peak Wet Weather Flow' 1,424,966 Notes: 1. PWWF shown is based on the ADWF from area B1 conveyed to the proposed sewer lift station LS-B1. 6.4.2 Sewer Lift Station B1 (LS-131)— Preliminary Firm Pumping Capacity Requirements The firm pumping capacity for lift station B1 should be equal to the PWWF of 1,424,966 GPD or 990 GPM. This exceeds 1.0 cfs (or 450 GPM), and therefore a low flow pump should be provided and designed for 50-100 GPM. As described in Section 2.2.3, the design TDH for LS-131 pumps should consider the secondary requirement of being able to utilize the interim/emergency bypass pipelines. During the design of Phase II's sewer collection system, the sewer model should be updated based the proposed interim and future emergency situations to provide TDH sizing parameters for the LS-B1 pumps. Table 6-6: Sewer Lift Station Area B1 (LS-B1)— Preliminary Firm Pumping Capacity Requirements Parameter Pumping Capacity Low Flow Pump Capacity 50-100 GPM Preliminary Required Firm Pumping Capacity 1,424,966 GPD or 990 GPM 6.5 Sewer Collection Area B2— Preliminary Steady State Results 6.5.1 Sewer Collection Area B2—Land Uses,Average Dry Weather Flows,and Peak Wet Weather Flows Sewer Collection Area B2 is proposed to be located in the South of Phase II and is bounded by Collection Area Al in the North, Collection Area A2 in the east, the Paradise Cut in the South and Collection Area B1 in the west. B2 is approximately 605 acres composed of all land uses except industrial. Based on conversations with River Islands, the future employment centers should be modeled as commercial land uses. Table 6-7 lists the total number of dwelling units or acreage of each land use in collection area B2, and the ADWF in gallons per day. At full buildout and under normal operating conditions, LS-B1 will pump Area B1's sewage into Area 132's collection system along A Street. Per the City Standards, the PWWF conveyed to the proposed sewer lift station B2 (LS-132) is 2,746,811 GPD based on the combined ADWF from areas B1 and B2. 24