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Home My WebLink AboutTechnical Report 08 - Overview of Sewer Service DEXTER WILSON ENGINEERING, INC. WATER ● WASTEWATER ● RECYCLED WATER CONSULTING ENGINEERS 2234 FARADAY AVENUE ● CARLSBAD, CA ● (760) 438-4422 OVERVIEW OF SEWER SERVICE FOR THE OTAY RANCH TOWN CENTER REDEVELOPMENT June 22, 2023 OVERVIEW OF SEWER SERVICE FOR THE OTAY RANCH TOWN CENTER REDEVELOPMENT June 22, 2023 Prepared by: Dexter Wilson Engineering, Inc. 2234 Faraday Avenue Carlsbad, CA 92008 (760) 438-4422 Job No. 509-127 June 15, 2023 509-127 Hunsaker & Associates San Diego, Inc. 9707 Waples Street San Diego, CA 92121 Attention: Chuck Cater, Vice President Subject: Overview of Sewer Service for the Otay Ranch Town Center Redevelopment Introduction This report provides an overview of sewer service for the Otay Ranch Town Center Redevelopment project. The project is located east of State Route 125, north of Birch Road, west of Eastlake Parkway, and south of Olympic Parkway in the City of Chula Vista. A vicinity map for the project is presented on Figure 1. The existing Otay Ranch Town Center site includes five lots (Lots 1, 2, 3, 4, and 5) on approximately 87.25 acres and comprises commercial space. The project proposes to redevelop the northwest portion of the existing Otay Ranch Town Center site. The redevelopment will affect Lots 1 and 4, which make up 58.49 acres of the overall site. Within the 58.49 acres, 16.57 acres will be redeveloped with 840 residential dwelling units; there will be no change in commercial square footage as 37,200 square feet of existing commercial will be removed and replaced with 37,200 square feet of new commercial. The remaining area will consist of private streets and plaza improvements. The Tentative Map title sheet for the Otay Ranch Town Center Redevelopment project is provided in Appendix A for reference. The title sheet includes tabulated land use breakdowns of the affected lots and shows the location of existing Lots 1, 2, 3, 4, and 5. Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 3 Sewer service for the existing Otay Ranch Town Center site is provided by the City of Chula Vista. Background The backbone sewer system for the existing Otay Ranch Town Center (previously referred to as Freeway Commercial or FC-1) site was identified in the May 2001 Freeway Commercial Conceptual Sewer Study prepared by Powell/PBS&J (May 2001 Study). This study projected sewer flows for the project based on a generation factor of 2,500 gpd/acre and established recommended sewer system projects required to provide sewer service to the project. Sewer Planning Criteria The planning criteria used to evaluate the sewer system requirements for the Otay Ranch Town Center Redevelopment project are in accordance with the City of Chula Vista 2014 Wastewater Collection System Master Plan. The 2014 Wastewater Collection System Master Plan outlines velocity and depth-to-diameter (d/D) requirements for existing and new sewer lines. Table 1 lists the sewer planning criteria for the project. TABLE 1 OTAY RANCH TOWN CENTER REDEVELOPMENT SEWER SYSTEM CRITERIA Item1 Criteria New Pipes 12-inches in diameter and smaller 2 0.50 (50%) full at peak wet weather flow Minimum Velocity 2 feet per second (½ full or full) Maximum Velocity 10 feet per second Manning’s n 0.013 New Pipe Minimum pipe diameter 8-inch 1. Gravity main requirements. 2. Design plans will be required when d/D reaches 0.60 for existing 12-inch diameter pipes or smaller, and improvements will be required once d/D reaches 0.70 at peak wet weather flows. Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 4 The gravity sewer analyses in this report were performed using a computer spreadsheet which uses the Manning Equation for all of its calculations. Per Table 1, the value of Manning’s “n” used is 0.013. Sewage Generation As previously mentioned, the May 2001 Study projected sewer flows for the current Otay Ranch Town Center site. The sewage generation factor used in the sewer study was 2,500 gpd/acre. Sewage generation for the proposed Otay Ranch Town Center Redevelopment project was estimated using sewage generation factors provided in the City of Chula Vista 2014 Wastewater Collection System Master Plan. The decrease in sewer generation factors compared to the May 2001 Study is due to water conservation efforts in recent years. The sewage generation factors are summarized in Table 2. TABLE 2 OTAY RANCH TOWN CENTER SEWAGE GENERATION FACTORS Land Use Sewage Generation Factor May 2001 Study Sewage Generation Factor Commercial 2,500 gpd/acre Current Sewage Generation Factors Commercial 1,401 gpd/acre Multi-Family Residential 182 gpd/DU To convert average sewage generation to peak dry weather flow (PDWF) a peaking factor of 1.41 was used. To convert average sewage generation to peak wet weather flow (PWWF) a peaking factor of 1.85 was used. Backup data for these peaking factors is presented in Appendix B. Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 5 Existing Otay Ranch Town Center Sewage Generation. Table 3 summarizes the average sewage generation for the existing Otay Ranch Town Center site based on the sewage generation factor presented in the May 2001 Study. TABLE 3 EXISTING OTAY RANCH TOWN CENTER AVERAGE SEWAGE GENERATION Land Use Quantity Sewage Generation Factor2 Average Sewage Generation, gpd Commercial1 87.25 acres 2,500 gpd/acre 218,125 TOTAL 218,125 1. Acreage reflects entire Otay Ranch Town Center site. The redevelopment will only affect 16.57 acres of Lots 1 and 4 which have a total area of 58.49 acres. 2. Based on sewage generation factor presented in the May 2001 Study. Based on Table 3, it is estimated that the existing Otay Ranch Town Center site generates sewage as follows: Average Sewage Generation: 218,125 gpd PDWF: 218,125 gpd x 1.41 = 307,556 gpd PWWF: 218,125 gpd x 1.85 = 403,531 gpd Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 6 Proposed Otay Ranch Town Center Redevelopment Sewage Generation. Table 4 summarizes the projected average sewage generation for the proposed Otay Ranch Town Center Redevelopment project based on current sewage generation factors. TABLE 4 OTAY RANCH TOWN CENTER REDEVELOPMENT AVERAGE SEWAGE GENERATION Land Use Quantity Sewage Generation Factor Average Sewage Generation, gpd Existing Development to Remain Existing Commercial1 70.68 acres 1,401 gpd/acre 99,023 Proposed Development2 Multi-Family Residential 840 DU 182 gpd/DU 152,880 Proposed Commercial 0.85 acres 1,401 gpd/acre 1,191 TOTAL 253,094 1. Acreage of existing Otay Ranch Town Center site (87.25 acres) reduced by 16.57 acres (redevelopment area). 2. Acreage excludes private street area (2.93 acres) and park/plaza area (2.73 acres) as no sewer generation is expected. Based on Table 4, it is estimated that the redevelopment of the existing Otay Ranch Town Center site will generate sewage flows as follows: Average Sewage Generation: 253,094 gpd PDWF: 253,094 gpd x 1.41 = 356,863 gpd PWWF: 253,094 gpd x 1.85 = 468,224 gpd In comparing the average sewage generation estimates shown on Table 3 and Table 4, the proposed redevelopment will increase existing average sewage generation by 34,969 gpd from 218,125 gpd to 253,094 gpd. Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 7 Existing Sewer System As previously mentioned, the Otay Ranch Town Center Redevelopment project is within the City of Chula Vista and will receive sewer service from the City of Chula Vista public sewer system. Sewer service to the existing Otay Ranch Town Center site is currently provided by 8-inch and 10-inch sewer lines onsite. The onsite sewer facilities convey sewage south to Birth Road by gravity to an existing 10-inch gravity sewer line. The 10-inch gravity sewer line in Birth Road conveys flow west across State Route 125 and increases to a 12-inch line before reaching La Media Road. A 12-inch gravity sewer in La Media Road conveys flow north to the Poggi Canyon Interceptor in Olympic Parkway. The existing sewer system in the vicinity of the project is presented on Figure 2. Proposed Sewer System Figure 3 presents the proposed sewer system for the Otay Ranch Town Center Redevelopment project. The existing 8-inch gravity sewer line in the northwest corner of the existing Otay Ranch Town Center site will be removed to accommodate the proposed redevelopment. The two northernmost buildings proposed within the redevelopment area will receive sewer service by installing two new reaches of sewer to serve the two northernmost proposed buildings within the project. Per the design criteria in Table 1, these new reaches of sewer will be required to have a minimum diameter of 8 inches. Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 10 Onsite Public Sewer System Analysis To evaluate the available capacity in the existing sewer lines within the Otay Ranch Town Center site, the sewer generation estimates in Table 4 were used. Using the sewer generation numbers presented in Table 4, a calculation was performed for the worst-case 8-inch segment of public sewer line within the project site that is impacted by the redevelopment. The worst-case 8-inch segment that is impacted by the redevelopment serves the west side of the site and has a 0.5 percent slope (see Figure 3). The calculation shows that an 8-inch sewer line at 0.5 percent slope can convey a maximum of 276,610 gpd at a depth-to-diameter (d/D) ratio of 0.5. The projected sewer flow for this 8-inch sewer line is 169,948 gpd at PWWF (91,864 gpd x 1.85 = 169,948 gpd) and is based on serving 320 residential units and 24 commercial acres (conservatively assumed to be approximately 1/3 of entire site acreage). Thus, the projected sewer flow for the worst-case 8-inch segment onsite is well under its available capacity. A second calculation was performed for the worst-case 10-inch segment of public sewer line within the project site that is impacted by the redevelopment. The minimum slope for any 10-inch sewer line onsite is 0.77 percent (see Figure 3). A 10-inch sewer line onsite at 0.77 percent slope can convey a maximum of 622,380 gpd at a depth-to-diameter (d/D) ratio of 0.5. This is well above the PWWF of 468,224 gpd projected for the entire Otay Ranch Town Center site post-redevelopment (PWWF = ADWF x 1.85 = 253,094 gpd x 1.85 = 468,224 gpd). Thus, all other onsite lines meet City of Chula Vista sewer criteria and onsite sewer line upgrades are not required for the redevelopment. Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 11 Offsite Public Sewer System Analysis The offsite public sewer analysis consists of two parts: the first part addresses the public sewer lines from the project to Olympic Parkway (Birch Road and La Media Road) and the second part address the capacity of the Poggi Canyon Interceptor. Birch Road and La Media Road Public Sewer Analysis. To evaluate the available capacity in the existing sewer lines downstream of the Otay Ranch Town Center site (west in Birch Road and north in La Media Road) to Olympic Parkway, hydraulic modeling data from the City of Chula Vista 2014 Wastewater Collection System Master Plan was used (see Appendix 2 of 2014 Wastewater Collection System Master Plan). The modeling data in the 2014 Wastewater Collection System Master Plan provides sewer pipeline diameters, slopes, and Year 2050 peak wet weather flows for the sewer system downstream of the project. The data provided in the 2014 Wastewater Collection System Master Plan was used to create a computer model spreadsheet to analyze the existing sewer system. The critical reach of sewer downstream of the project is a 10-inch sewer line in Birch Road that has a slope of 0.5 percent. The sewer slope for the critical reach of sewer was confirmed using an as-built drawing which is included in Appendix C for reference. At the time of the preparation of the 2014 Wastewater Collection System Master Plan, the following two assumptions were made related to manhole sewer flow loading: 1. It was assumed that the Otay Ranch Town Center (previously referred to as Freeway Commercial) site would flow north into Olympic Parkway; however, that is not the case as the existing Otay Ranch Town Center site flows south into Birch Road. 2. It was assumed that 982 EDUs (modeling data shows ADWF = 260,329 gpd / 265 gpd/EDU = 982 EDUs) would flow into the existing 10-inch sewer line in Birch Road upstream of the intersection of Birch Road and Millenia Avenue; however, that is not the case as the only project contributing sewer flow to this portion of the sewer line is the Eastern Urban Center project which contributes a maximum of 580 EDUs to the sewer line in Birch Road per the project’s approved EIR (see Appendix D). Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 12 Based on the changes to the assumptions in the 2014 Wastewater Collection System Master Plan outlined above, the following two changes were made to the modeling data pulled from the 2014 Wastewater Collection System Master Plan for the sewer analysis. 1. The PWWF determined for the Otay Ranch Town Center site under existing and proposed conditions was added to the PWWF at Birch Road presented in the 2014 Wastewater Collection System Master Plan to evaluate the available capacity in the existing sewer system. 2. The PWWF presented in the 2014 Wastewater Collection System Master Plan for the Eastern Urban Center was reduced from 371,483 gpd (982 EDUs at 265 gpd/EDU with 1.44 peaking factor) to 246,790 gpd (580 EDUs at 230 gpd/EDU with 1.85 peaking factor) to evaluate the available capacity in the existing sewer system. Appendix E presents the computer model results for the existing sewer system under Year 2050 flows plus the existing Otay Ranch Town Center site. Exhibit A at the back of this report presents a Manhole Diagram for the modeling data. The results in Appendix E indicate that the maximum d/D in the existing public sewer system downstream of the project is 0.59 d/D at Computer Model Pipe 16648 (10-inch sewer line just downstream of the project). Flow velocities in the existing sewer system range from 3.0 fps to 7.6 fps. Appendix F presents the computer model results for the existing sewer system under Year 2050 flows plus the proposed Otay Ranch Town Center redevelopment. Exhibit A presents a Manhole Diagram for the system. The results indicate that the maximum d/D in the existing public sewer system downstream of the project increases from 0.59 d/D to 0.63 d/D. Flow velocities in the existing sewer system range from 3.0 fps to 7.7 fps. As described in Footnote 2 of Table 1 in this report, the maximum allowable d/D for existing sewer lines 12-inches in diameter and smaller is 0.70 d/D before a sewer system upgrade is required. Thus, no public sewer improvements are required to accommodate the proposed project as the existing public sewer system can accommodate the proposed project based on Year 2050 flows. Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 13 Poggi Canyon Interceptor Analysis. The available capacity in the Poggi Canyon Interceptor was evaluated using data from the April 2009 Poggi Canyon Basin Gravity Sewer Development Impact Fee Update prepared by PMC (2009 Poggi DIF Study). Data from this report includes existing permitted EDUs in the Poggi Canyon basin as well as committed EDUs based on previous project approvals. Since the time of the 2009 Poggi DIF Study a few projects have been approved that have increased the amount of units to the Poggi Interceptor. The projects accounted for are the following: 1. JPB Village 2 SPA Amendment. The JPB Village 2 SPA Amendment increased the unit count in Village 2 by 197 units. Per the November 21, 2011 Sewer System Evaluation that was done for this project, the net effect of this land use change was the addition of 160 EDUs to the Poggi Basin. These additional EDUs have been considered in this sewer system analysis. 2. Village 2 Comprehensive SPA Amendment. The Village 2 Comprehensive SPA Amendment increased the unit count in Village 2 by 1,562 units. Per the March 4, 2014 Sewer System Evaluation that was done for this project, the net effect of this land use change was the addition of 938 EDUs to the Poggi Basin. These additional EDUs have been considered in this sewer system analysis. 3. Eastern Urban Center (EUC). The EUC was approved in September 2009, shortly after the 2009 PMC Study was prepared. The PMC Study did, however, anticipate the EUC project and included 429 EDUs from the EUC (Table 3-2) in the calculation of the Poggi Interceptor Fee. These units include 189 EDUs within the Poggi Basin and 240 EDUs that are proposed to be permanently diverted from the Salt Creek Basin to the Poggi Basin. Since the 2009 PMC Study already accounts for units from the EUC, no additional EDUs from the EUC have been considered as part of this sewer system analysis. Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 14 Because the analysis of the Poggi Canyon Interceptor will be largely based on the 2009 Poggi DIF Study, a comparison of the proposed redevelopment versus the assumptions in the 2009 Poggi DIF Study is necessary. Table 5 provides the sewer flow projections from the 2009 Poggi DIF Study compared to the current land use plan with the redevelopment. As shown in Table 5, the Poggi Basin projections in the 2009 Poggi DIF Study would be increased by 132 EDUs based on the proposed Otay Ranch Town Center Redevelopment project. TABLE 5 OTAY RANCH TOWN CENTER REDEVELOPMENT POGGI BASIN EDU SUMMARY Description Quantity Unit Flow Factor Average Flow, gpd EDUs1 2009 DIF Study Commercial – Otay Ranch Town Center 87.25 acres2 2,500 gpd/ac 218,125 823.1 Subtotal 2009 DIF Study 823.1 Current Plan with Redevelopment Existing Commercial3 70.68 acres 1,401 gpd/acre 99,023 373.7 Multi-Family Residential 840 DU 182 gpd/DU 152,880 576.9 Retail 0.85 acres 1,401 gpd/acre 1,191 4.5 Subtotal Current Plan with Redevelopment 955.1 Increase 132 1. Based on the sewer generation factor of 265 gpd/unit used in the 2009 Poggi DIF Study. 2. Acreage of the Otay Ranch Town Center site was presented as 81.92 acres in the 2009 DIF Study. Current numbers show the site has a total area of 87.25 acres. Therefore, the acreage was increased from 81.92 acres to 87.25 acres for this analysis. 3. Acreage of existing Otay Ranch Town Center site (87.25 acres) reduced by 16.57 acres (redevelopment area). Table G-7 in Appendix G summarizes the impact that adding 132 EDUs would have on permitted and committed remaining capacity in the Poggi Canyon Interceptor. Exhibits B-1 and B-2 identifies Poggi Interceptor reach locations and indicate where the Otay Ranch Town Center flows ultimately enter the Poggi Interceptor. Chuck Cater June 22, 2023 ORTC Redevelopment – Overview of Sewer DEXTER WILSON ENGINEERING, INC. PAGE 15 As shown in Table G-7 in Appendix G, the two reaches already identified in the 2009 Poggi DIF Study for future replacement are shown as being over capacity and one additional reach, P345 to P365, reach is shown to be slightly over capacity. This additional reach was identified as over capacity in the March 4, 2014 Sewer System Evaluation that was done for Village 2 Comprehensive SPA Amendment. Thus, the limits of the required DIF improvements for the Otay Ranch Town Center Redevelopment project are the same as those presented in the March 4, 2014 Sewer System Evaluation that was done for Village 2 Comprehensive SPA Amendment. The Poggi Basin Gravity Sewer Development Impact Fee is currently being updated and should reflect the additional units and additional improvement identified in Table G-7 in Appendix G. Thank you for the opportunity to assist you with the sewer system planning for this project. If you have any questions regarding the information presented in this report, please do not hesitate to call. Dexter Wilson Engineering, Inc. Fernando Fregoso, P.E. FF:ru Attachments APPENDIX A TENTATIVE MAP TITLE SHEET F C -1 F C -2 F C -1 F C -1 F C -1 F C -1 F C -1 M U /R M U /R P P S P S P S P S M U /R M U /R M U /R P M U /R M U /R M U /R M U /R P P L O T 1 0 L O T 1 L O T 5 L O T 7 L O T 8 L O T 6 L O T 9 L O T 2 L O T 3 L O T 4 L O T A L O T B L O T C L O T D L O T H L O T E L O T F L O T G L O T 1 0 L O T 1 0 L O T 1 0 L O T 1 0 A. PROPOSED LAND USE LOT LAND USE AREA AC COMMERCIAL DENSITY DU/AC UNITS MU/R LOT 1 Urban Core 1.65 -77.0 - MU/R LOT 2 Urban Core 1.23 -77.0 - MU/R LOT 3 Urban Core 1.88 -77.0 - MU/R LOT 4 Urban Core 1.86 *37,200 SF 77.0 - MU/R LOT 5 Urban Core 0.73 -77.0 - MU/R LOT 6 Urban Core 0.73 -77.0 - MU/R LOT 7 Urban Core 1.19 -77.0 - MU/R LOT 8 Urban Core 1.17 -77.0 - MU/R LOT 9 Urban Core 0.47 -77.0 - SUBTOTAL MU/R 10.91 --840 PS LOT A Private St.1.50 --- PS LOT B Private St.0.80 --- PS LOT C Private St.0.26 --- PS LOT D Private St.0.37 --- SUBTOTAL PS 2.93 --- P LOT E Park/Plaza 0.72 --- P LOT F Park 0.87 --- P LOT G Park 0.38 --- P LOT H Park 0.76 --- SUBTOTAL PARK 2.73 --- SUBTOTAL REDEVELOPMENT 16.57 --- LOT 10 Commercial Retail 41.93 --- TOTAL 58.49 *37,200 -840 Note: Acreages rounded to the nearest hundredth of an acre *37,200 sf of existing commercial to be replaced with 37,200 sf of new commercial B. EXISTING LOTS LOT LAND USE AREA AC LOT 1 Commercial Retail 50.791 LOT 4 Commercial Retail 7.699 TOTAL 58.490 CONDOMINIUM NOTES OTAY RANCH TOWN CENTER FC-1 TENTATIVE MAP/CVT 22-0002 FOR: CITY OF CHULA VISTA, CALIFORNIA 8 SHEET OF REVISIONS DATE BYNO.PREPARED BY: HUNSAKER& ASSOCIATES TOWN CENTER FC-1 TENTATIVE MAP/CVT 22-0002 OTAY RANCH City Of Chula Vista, California CVT # 22-0002 EARTHWORK/GRADING QUANTITIES GENERAL NOTES SOURCE OF TOPOGRAPHY GENERAL DESIGN NOTES BENCHMARK: SHEET INDEX PUBLIC UTILITIES LEGAL DESCRIPTION: EASEMENT & ENCUMBRANCE NOTES ABBREVIATIONS LEGEND MU/R SHEET 1 - TITLE SHEET/TABLES SHEET 2 - STREET SECTIONS & SITE SECTION SHEET 7 - BOUNDARY, EASEMENTS SHEET 5 - PROJECT DESIGN & ENCUMBRANCES SHEET 4 - PROJECT DESIGN SHEET 8 - BOUNDARY, EASEMENTS & ENCUMBRANCES KEY MAP SHEET 3 - PROJECT DESIGN 1 LAND USE SUMMARY L D A O IS A S .V IALP A N C 47945 LIVIC FTA OE ILACF T S R E G IS NRO AI I N E ER O TER E D P R O F E SSI NAL E N G APPLICANT/OWNER SHEET 6 - PROPOSED LOTTING, EASEMENTS & FC-1 5 EASEMENTS OR PORTIONS OF EASEMENTS TO BE VACATED LOT 1 LOT A APPENDIX B PEAKING FACTOR BACKUP DATA City of Chula Vista Wastewater Collection System Master Plan May 2014 - FINAL Figure 3-5: Normalized Diurnal Curve (Non-Residential) 3.3.6 PEAK WET WEATHER WASTEWATER FLOW (PWWF) Peak Wet Weather Wastewater Flow (PWWF) is estimated as Peak Dry Weather Flow (PDWF) plus Rainfall Dependent Infiltration/Inflow (RDI/I) and BWI, combined as Inflow/Infiltration (I/I) for this master plan due to the data available. RDI/I is storm water that enters the wastewater collection system in direct response to the intensity and duration of individual rainfall events. RDI/I may recede gradually after a storm; however, any residual flow is considered to be a general increase in GWI. To create the PWWF scenarios, the model was loaded using PDWF values, and Rainfall Dependent Inflow and Infiltration (RDI/I), combined as I/I was added to the PDWF. Peak values were then evaluated based on consistency throughout the year from data gathered from the City’s main outfalls, removing any inconsistent peaks, resulting in an average peaking factor for I/I of 1.85. The total volume of I/I was then averaged out across the city and multiplied accordingly to each pipeline based on its length-diameter. The respective I/I value was then added to the calculated BWF per time period for PWWFs. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0: 0 0 1: 0 0 2: 0 0 3: 0 0 4: 0 0 5: 0 0 6: 0 0 7: 0 0 8: 0 0 9: 0 0 10 : 0 0 11 : 0 0 12 : 0 0 13 : 0 0 14 : 0 0 15 : 0 0 16 : 0 0 17 : 0 0 18 : 0 0 19 : 0 0 20 : 0 0 21 : 0 0 22 : 0 0 23 : 0 0 Pe r c e n t a g e o f A v e r a g e F l o w Time (HH:MM) 3-21 City of Chula Vista Wastewater Collection System Master Plan May 2014 - FINAL Figure 3-4: Normalized Diurnal Curve (Residential) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0: 0 0 1: 0 0 2: 0 0 3: 0 0 4: 0 0 5: 0 0 6: 0 0 7: 0 0 8: 0 0 9: 0 0 10 : 0 0 11 : 0 0 12 : 0 0 13 : 0 0 14 : 0 0 15 : 0 0 16 : 0 0 17 : 0 0 18 : 0 0 19 : 0 0 20 : 0 0 21 : 0 0 22 : 0 0 23 : 0 0 Pe r c e n t a g e o f A v e r a g e F l o w Time (HH:MM) 3-20 APPENDIX C SEWER SYSTEM AS-BUILT DRAWING APPENDIX D EASTERN URBAN CENTER EIR EXCERPT 4.11 Public Services and Utilities Eastern Urban Center Sectional Planning Area EIR City of Chula Vista State Clearinghouse No. 2007041074 May 2009 Page 4.11-107 PRELIMINARY WORKING DRAFT – Work in Progress proposed on-site system would be required to comply with the existing Subdivision Manual, Section 3 (General Design Criteria) and would be subject to review by the City’s Engineering Department. Compliance with regulatory design criteria would ensure that on-site lines would not exceed 75 percent of pipe capacity for pipes greater than 12 inches in diameter or 50 percent for pipes 12 inches or less in diameter. Therefore, the project would be less-than-significant with respect to this threshold requirement. B. Off-Site Sewage Collection System (1) Off-Site Poggi Canyon Sewer Improvement Area Detailed analysis of the off-site sewage collection system and potential impacts to each sewer drainage basis are provided in the TSS attached in Appendix J of this EIR. The current preliminary Grading Analysis of the proposed project shows that the northern blocks of the EUC (Blocks 2 through 6 and Park P1), would drain north to an existing 10-inch gravity sewer in Birch Road, where wastewater would be conveyed to the Poggi Canyon Trunk Sewer (PCTS) The Poggi Canyon Sewer Basin Plan Update and Pumped Flow Analysis (PBS&J, May 2002), which determined the number of committed and future EDUs in the PCTS found that Reaches P205 and P270 were the most critical in the PCST system. Since the study, Reach P205 has been replaced, leaving Reach P270, located at the intersection of Olympic Parkway and Brandywine Avenue, as the remaining critical reach. Based on the City’s Subdivision Manual Criteria of 265 gpd/EDU and a flow of 75 percent of system capacity, a 21-inch replacement for Reach 270 is determined sufficient to serve the interim and ultimate worst case flow conditions for the maximum land use plan in the north sector of the EUC, including the potential for shifts in land use densities and ultimate flow conditions for the maximum land use plan.57 As demonstrated in the Technical Sewer Study, the maximum condition, which includes 464 EDUs (122,960 gpd) from Village Seven and 580 EDUs (153,700 gpd) from the EUC, would increase tributary units to 14,236 EDUs. The resulting rate of 6,262,416 gpd would increase the flow in the Poggi Canyon system to 67.6 percent of capacity, which would be less than the 75 percent threshold. Reach P270 (the PCSI) is proposed to be replaced as part of the EUC project with design plans to be complete prior to the approval of any Final Maps for any areas in the EUC within the Poggi Canyon Basin, and construction to be completed prior to first occupancy of units that would utilize the PCTS. Mitigation measures are recommended to ensure that improvements would be completed in a manner acceptable to the City Engineer. With the completion of the proposed improvement, the proposed project would have a less-than-significant impact with respect to the capacity of the PCTS. Therefore, the project would not exceed the threshold capacity in this system. 57 PBS&J, op. cit., page 13. APPENDIX E SEWER SYSTEM ANALYSIS YEAR 2050 CITY FLOWS PLUS EXISTING OTAY RANCH TOWN CENTER FLOWS 6/20/2023 FOR:SHT 1 OF 1 509-127 BY:REFER TO PLAN SHEET: M.G.D.C.F.S. 16648 A 15191 15190 251,048 403,531 654,579 0.655 1.013 10 0.50 0.302799 0.49146 0.59 0.4817 3.03 EXIST. ORTC PWWF = 403,531 gpd 16647 15190 15189 253,052 403,531 656,583 0.657 1.016 10 2.50 0.135831 0.30911 0.37 0.2651 5.52 16646 15189 15188 254,712 403,531 658,243 0.658 1.019 10 4.10 0.106334 0.27155 0.33 0.2222 6.60 16645 15188 15187 256,368 403,531 659,899 0.660 1.021 10 2.20 0.145527 0.32087 0.39 0.2788 5.27 16644 15187 15186 258,592 403,531 662,123 0.662 1.025 10 1.20 0.197709 0.38027 0.46 0.3491 4.23 16643 15186 15185 260,393 403,531 663,924 0.664 1.027 10 1.00 0.217168 0.40125 0.48 0.3742 3.95 16642 15185 15184 262,615 403,531 666,146 0.666 1.031 10 1.00 0.217895 0.40202 0.48 0.3751 3.96 16641 15184 15183 264,411 403,531 667,942 0.668 1.034 10 1.20 0.199446 0.38218 0.46 0.3513 4.24 16640 15183 15181 265,983 403,531 669,514 0.670 1.036 10 2.60 0.135816 0.30909 0.37 0.2651 5.63 16638 15181 15180 268,018 403,531 671,549 0.672 1.039 10 1.20 0.200523 0.38336 0.46 0.3527 4.24 16637 15180 15179 269,563 403,531 673,094 0.673 1.042 10 3.60 0.116039 0.28428 0.34 0.2366 6.34 16636 15179 15178 271,379 403,531 674,910 0.675 1.044 10 4.10 0.109026 0.27516 0.33 0.2262 6.65 16776 15178 15243 350,354 403,531 753,885 0.754 1.167 10 1.30 0.216278 0.40030 0.48 0.3731 4.50 16765 15243 15244 352,977 403,531 756,508 0.757 1.171 12 4.30 0.073385 0.26920 0.27 0.1704 6.87 16766 15244 15245 355,743 403,531 759,274 0.759 1.175 12 3.70 0.079401 0.28018 0.28 0.1802 6.52 16767 15245 15246 357,773 403,531 761,304 0.761 1.178 12 2.50 0.096854 0.31042 0.31 0.2078 5.67 16770 15246 9161 357,773 403,531 761,304 0.761 1.178 12 2.50 0.096854 0.31042 0.31 0.2078 5.67 9146 9161 15248 374,963 403,531 778,494 0.778 1.205 12 0.60 0.202166 0.46216 0.46 0.3549 3.39 16772 15248 15250 376,682 403,531 780,213 0.780 1.207 12 0.60 0.202612 0.46274 0.46 0.3554 3.40 16773 15250 15251 379,025 403,531 782,556 0.783 1.211 12 0.60 0.203221 0.46353 0.46 0.3562 3.40 16774 15251 15252 380,839 403,531 784,370 0.784 1.214 12 0.60 0.203692 0.46415 0.46 0.3568 3.40 16775 15252 15242 383,075 403,531 786,606 0.787 1.217 12 0.60 0.204272 0.46490 0.46 0.3576 3.40 16764 15242 13388 406,107 403,531 809,638 0.810 1.253 12 4.00 0.081431 0.28381 0.28 0.1834 6.83 15531 13388 13389 408,761 403,531 812,292 0.812 1.257 12 0.50 0.231076 0.49887 0.50 0.3918 3.21 15530 13389 13387 411,514 403,531 815,045 0.815 1.261 12 5.20 0.071897 0.26634 0.27 0.1679 7.51 15529 13387 13386 509,234 403,531 912,765 0.913 1.412 12 1.00 0.183606 0.43761 0.44 0.3304 4.27 15528 13386 12844 511,194 403,531 914,725 0.915 1.415 12 1.90 0.133488 0.36748 0.37 0.2618 5.41 Min Slope Max dn/D 0.50 0.59 A. City model shows slope of 0.7% for Line 16648. As-built drawing presented in Appendix C shows slope of 0.5% for Line 16648; thus, a sewer slope of 0.5% is used for the analysis. COMBINED PEAK FLOW (gpd) DATE:SEWER STUDY SUMMARY Otay Ranch Town Center Redevelopment - City Year 2050 Flows JOB NUMBER:Dexter Wilson Engineering, Inc. LINE FROM TO CITY YEAR 2050 PWWF (gpd) EXISTING ORTC PROJECT PEAK FLOW (gpd) Ca for Velocity(3)VELOCITY (f.p.s.)COMMENTS PEAK FLOW (DESIGN FLOW)LINE SIZE (inches) DESIGN SLOPE (%)DEPTH K' (1)dn (feet)dn/D(2) 1 K' based on n = 0.013 2 dn/D using K' in Brater King Table 7-14 3 From Brater King Table 7-4 based on dn/D \\artic\Eng\509127\Sewer\2023-06-20 Town Center Redevelopment Offsite Sewer Analysis Year 2050 Flow APPENDIX F SEWER SYSTEM ANALYSIS YEAR 2050 CITY FLOWS PLUS PROPOSED OTAY RANCH TOWN CENTER FLOWS 6/20/2023 FOR:SHT 1 OF 1 509-127 BY:REFER TO PLAN SHEET: M.G.D.C.F.S. 16648 A 15191 15190 251,048 468,224 719,272 0.719 1.113 10 0.50 0.332726 0.52263 0.63 0.5184 3.09 PROP. ORTC PWWF = 468,224 gpd 16647 15190 15189 253,052 468,224 721,276 0.721 1.116 10 2.50 0.149214 0.32525 0.39 0.2839 5.66 16646 15189 15188 254,712 468,224 722,936 0.723 1.119 10 4.10 0.116785 0.28524 0.34 0.2377 6.78 16645 15188 15187 256,368 468,224 724,592 0.725 1.121 10 2.20 0.159794 0.33761 0.41 0.2984 5.41 16644 15187 15186 258,592 468,224 726,816 0.727 1.125 10 1.20 0.217026 0.40110 0.48 0.3740 4.33 16643 15186 15185 260,393 468,224 728,617 0.729 1.127 10 1.00 0.238329 0.42420 0.51 0.4020 4.04 16642 15185 15184 262,615 468,224 730,839 0.731 1.131 10 1.00 0.239056 0.42506 0.51 0.4031 4.04 16641 15184 15183 264,411 468,224 732,635 0.733 1.134 10 1.20 0.218764 0.40295 0.48 0.3762 4.34 16640 15183 15181 265,983 468,224 734,207 0.734 1.136 10 2.60 0.148939 0.32493 0.39 0.2835 5.77 16638 15181 15180 268,018 468,224 736,242 0.736 1.139 10 1.20 0.219841 0.40410 0.48 0.3776 4.34 16637 15180 15179 269,563 468,224 737,787 0.738 1.142 10 3.60 0.127191 0.29847 0.36 0.2528 6.50 16636 15179 15178 271,379 468,224 739,603 0.740 1.144 10 4.10 0.119477 0.28869 0.35 0.2416 6.82 16776 15178 15243 350,354 468,224 818,578 0.819 1.267 10 1.30 0.234837 0.42004 0.50 0.3971 4.59 16765 15243 15244 352,977 468,224 821,201 0.821 1.271 12 4.30 0.079661 0.28064 0.28 0.1806 7.04 16766 15244 15245 355,743 468,224 823,967 0.824 1.275 12 3.70 0.086166 0.29218 0.29 0.1910 6.67 16767 15245 15246 357,773 468,224 825,997 0.826 1.278 12 2.50 0.105084 0.32385 0.32 0.2203 5.80 16770 15246 9161 357,773 468,224 825,997 0.826 1.278 12 2.50 0.105084 0.32385 0.32 0.2203 5.80 9146 9161 15248 374,963 468,224 843,187 0.843 1.305 12 0.60 0.218966 0.48380 0.48 0.3765 3.47 16772 15248 15250 376,682 468,224 844,906 0.845 1.307 12 0.60 0.219412 0.48437 0.48 0.3771 3.47 16773 15250 15251 379,025 468,224 847,249 0.847 1.311 12 0.60 0.220021 0.48515 0.49 0.3779 3.47 16774 15251 15252 380,839 468,224 849,063 0.849 1.314 12 0.60 0.220492 0.48576 0.49 0.3785 3.47 16775 15252 15242 383,075 468,224 851,299 0.851 1.317 12 0.60 0.221072 0.48650 0.49 0.3792 3.47 16764 15242 13388 406,107 468,224 874,331 0.874 1.353 12 4.00 0.087937 0.29524 0.30 0.1938 6.98 15531 13388 13389 408,761 468,224 876,985 0.877 1.357 12 0.50 0.249480 0.52310 0.52 0.4161 3.26 15530 13389 13387 411,514 468,224 879,738 0.880 1.361 12 5.20 0.077603 0.27691 0.28 0.1773 7.68 15529 13387 13386 509,234 468,224 977,458 0.977 1.512 12 1.00 0.196619 0.45489 0.45 0.3476 4.35 15528 13386 12844 511,194 468,224 979,418 0.979 1.515 12 1.90 0.142929 0.38133 0.38 0.2752 5.51 Min Slope Max dn/D 0.50 0.63 A. City model shows slope of 0.7% for Line 16648. As-built drawing presented in Appendix C shows slope of 0.5% for Line 16648; thus, a sewer slope of 0.5% is used for the analysis. SEWER STUDY SUMMARY Otay Ranch Town Center Redevelopment - City Year 2050 plus Project Flows Dexter Wilson Engineering, Inc.JOB NUMBER: COMBINED PWWF (gpd) DATE: COMMENTS PEAK FLOW (DESIGN FLOW)VELOCITY (f.p.s.) LINE SIZE (inches) DESIGN SLOPE (%)DEPTH K' (1)dn (feet)dn/D(2)Ca for Velocity(3)LINE FROM TO CITY YEAR 2050 PWWF (gpd) PROPOSED ORTC PROJECT PEAK FLOW (gpd) 1 K' based on n = 0.013 2 dn/D using K' in Brater King Table 7-14 3 From Brater King Table 7-4 based on dn/D \\artic\Eng\509127\Sewer\2023-06-20 Town Center Redevelopment Offsite Sewer Analysis Year 2050 plus Project Flow APPENDIX G TABLE G-7 POGGI CANYON INTERCEPTOR SUMMARY TABLE G-7 POGGI CANYON INTERCEPTOR SUMMARY Reach Capacity at d/D=0.85 EDUs 2009 Poggi DIF Study Permitted EDUs 2009 Poggi DIF Study1 Committed EDU’s Additional EDUs2 Net EDUs Permitted Remaining Net Committed Remaining EDUs Current Remaining Capacity Current Remaining Capacity P102 to P140 18,367 11,602 6,765 16,204 2,163 1,230 5,535 933 P140 to P175R 22,192 11,602 10,591 16,204 5,988 1,230 9,361 4,758 P175R to P195 35,898 11,602 24,296 16,204 19,694 1,230 23,066 18,464 P195 to P230 18,367 10,726 7,640 15,328 3,039 1,230 6,410 1,809 P230 to P240 16,427 10,053 6,374 14,655 1,772 1,230 5,144 542 P240 to P253R 16,427 10,053 6,374 14,655 1,772 1,230 5,144 542 P253R to P2703 12,175 9,763 2,412 14,365 (2,190) 1,230 1,182 (3,420) P270 to P3053 12,175 8,587 3,589 13,125 (950) 1,230 2,359 (2,180) P305 to P310 38,503 8,587 29,916 12,609 25,894 1,230 28,686 24,664 P310 to P345 17,047 8,447 8,600 12,469 4,578 1,230 7,370 3,348 P345 to P3654 13,339 8,289 5,049 12,312 1,027 1,230 3,819 (203) P365 to P405 17,305 8,289 9,016 11,590 5,715 1,230 7,786 4,485 P405 to P410 13,339 7,770 5,569 11,070 2,269 1,230 4,339 1,039 u/s P410 to SR125 13,339 6,605 6,733 9,906 3,433 1,230 5,503 2,203 1. Committed EDUs do not include interim 464 EDUs from Village 7, 281 EDUs from EUC. 2. Includes 160 EDUs from the JPB Village 2 SPA Amendment, 938 EDUs from the Village 2 Comprehensive SPA Amendment, and 132 EDUs from the Otay Ranch Town Center Redevelopment project (160 EDUs + 938 EDUs +132 EDUs = 1,230 EDUs). 3. Identified for future replacement in 2009 Poggi DIF Study. 4. Identified for future replacement in March 4, 2014 Sewer System Evaluation prepared for the Village 2 Comprehensive SPA Amendment. EXHIBIT A MANHOLE DIAGRAM FOR BIRCH ROAD AND LA MEDIA ROAD ANALYSIS EXHIBIT B POGGI INTERCEPTOR MAP