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April 2016 - FINAL DRAFT 3-1 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH03/Draft Final - Ch03 CS.doc Chapter 3 FLOW MONITORING PROGRAM This chapter presents the temporary flow monitoring program data applied to the hydraulics model that was used to evaluate the capacity of the collection system. 3.1 FLOW MONITORING PROGRAM In 2014, the City of Modesto (City) contracted with V&A Consulting Engineers (V&A) to conduct a temporary flow monitoring project for the City’s sanitary sewer collection system. The goals of this project were to quantify wastewater flows in the sewer system, to assist the development of design flow criteria, and to correlate actual collection system flows with the hydraulic model’s predicted flows. The data from this project were also used to recalibrate the collection system’s hydraulic model for dry weather and wet weather flow and to identify areas of the system with high infiltration/inflow V&A conducted two flow monitoring programs. The first flow monitoring program was conducted during the dry season, which ran from April 30, 2014, to May 27, 2014. The second monitoring program was conducted during the wet season, which ran from December 11, 2014, to March 1, 2015. Both flow monitoring programs are summarized in the “Draft Sanitary Sewer Flow Monitoring and Inflow/Infiltration Study, July 2015,” which V&A prepared. For reference, a copy of this report is included in Appendix C. 3.1.1 Flow Monitoring Sites and Tributary Areas The City’s sewer service area is divided into ten tributary areas. Forty-three monitoring sites were selected to isolate each tributary area and the multiple sub-areas within the City’s collection system. In general, the same monitoring locations were used for both dry weather and wet weather monitoring programs, with a few exceptions. Figure 3.1 shows the locations of temporary flow monitoring and the tributary area associated with each site. Figure 3.1 indicates the type of flow monitoring data collected at each site dry weather, wet weather, or both). Table 3.1 lists the locations of flow monitoring and the diameters of pipes that were metered. Figure 3.2 provides a schematic illustration of the flow monitoring locations. ---PAGE BREAK--- April 2016 - FINAL DRAFT 3-2 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH03/Draft Final - Ch03 CS.doc Table 3.1 Flow Monitoring Sites Wastewater Collection System Master Plan City of Modesto, California Meter Name Location Flow Data Type Are a Measured Pipe Diameter (inch) 1-1 Soccer Field, South of John and Thomas St. Dry & Wet 1 58 1-2 Conant Ave. and Sisk Rd. Dry & Wet 1 48 1-3 North of Hahn Dr. and English Oaks Dr. Dry & Wet 1 39 1-4 Woodrow Ave. and Mark Allen Dr., at Stop Sign Dry & Wet 1 28 1-5 Poust Rd. and Naas Ct. in Southbound Lane of Poust Rd. Dry & Wet 1 54 2-1 North of Hancock St. and Donald St. Dry & Wet 2 42.75 2-2 N. Emerald Ave. and Elm Ave. in Center of Intersection Dry & Wet 2 31.25 2-3 North of Woodland Ave./Coldwell Ave. and N. 9th St. Dry & Wet 2 18.5 2-4 North of Kearney Ave. and Coldwell Ave. in Northbound Lane Dry & Wet 2 30 2-5 Tully Rd. and W. Granger Ave. Dry & Wet 2 21 2-6 Carver Rd. and Bay Meadows Dr. in Southbound Lane Dry & Wet 2 15 3-1 Sutter Ave., south of Robertson Rd. Dry & Wet 3 18 4-1 North of E St. and 6th St. in Northbound Lane of 6th St. Dry & Wet 4 18 4-2 Just north of N. 7th St. and C St. in Northbound Lane Dry & Wet 4 33 4-3 Just North of 9th St. and B St. in Center of 9th St. Dry & Wet 4 15 4-4 Beard St. and D St. Dry & Wet 4 10 5-1 On River Floodplain Off Bridge at S. Morton Boulevard and 9th St. Dry & Wet 5 41.5 5-2 S. Santa Rosa Ave., Near Railroad Crossing Dry & Wet 5 30 5-3 In Median of Scenic Dr., Between Sunnyside Ave. and Brighton Dry & Wet 5 28 5-4 Coffee Rd. and E. Morris Ave. in Southbound Lane Dry & Wet 5 15 5-5 Rose Ave. and Rockford Ave., in Center of Roadway Dry & Wet 5 21 6-1 S. Morton Boulevard at Entrance to Beard Brook Park Dry & Wet 6 47.5 6-3 Off Shoulder at 90° Corner of Nathan Ave. and El Roya Ave. Dry & Wet 6 48 ---PAGE BREAK--- April 2016 - FINAL DRAFT 3-3 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH03/Draft Final - Ch03 CS.doc Table 3.1 Flow Monitoring Sites Wastewater Collection System Master Plan City of Modesto, California Meter Name Location Flow Data Type Are a Measured Pipe Diameter (inch) 6-4 Beard Ave., South of Rodney Ave. at Canal Dry & Wet 6 45 6-5 Lincoln Ave., Just South of Gibson Way Dry & Wet 6 36 6-6 South End of Scenic Bend, Just South of Scenic Dr. Dry & Wet 6 33 6-7 North End of Scenic Bend, Just South of Scenic Dr. Dry & Wet 6 33 6-8 Wild Palms Dr. Between Pepper Tree Ln. and Fransen Ln. Dry & Wet 6 30 6-9 Eastbound Lane of St. Pauls Way, West of Sturm Dr. and St. Pauls Ct. Dry & Wet 6 30 6-10 S. McClure Rd., South of Yosemite Blvd. Dry & Wet 6 10 7-1 Oregon Dr., West of S. Santa Cruz Ave. Dry & Wet 7 60 7-2 Tioga Dr. and Empire Ave. in Westbound Stop Lane of Tioga Dr. Dry & Wet 7 (CS L) 47.75 7-B Oregon Dr. and Empire Ave. in Middle of Intersection Dry Only 7 30 8-1 Blankenburg Ave., Just West of S. 7th St. on Eastbound Edge of Road Dry & Wet 8 24 9-1 Cascade Ave., 1/2 Block North of W. Hatch Rd. Dry & Wet 9 30 10-1 North of 90º Turn on Crater Ave., North of W. Hatch Rd. Dry & Wet 10 24 A Center of Eastbound Lane of Veneman Ave. Between Beachler Dr. and Hahn Dr. Dry & Wet 1 18 B N. Jefferson St. and Linden St. Dry & Wet 1 16 C Off Shoulder of Zeff Rd. at Crows Landing Rd. Dry & Wet 9 15 D At 5th Tee of Dryden Golf Course Dry Only 3 60 E Southbound Lane of Crows Landing Rd., South of Algen Ave. Dry Only 10 21 F Sutter Ave., Just South of Tuolumne Blvd. Wet Only 3 18 G Dirt Road in Empty Field, South of Tuolumne Boulevard and S. 7th Street Wet Only 7 (CS L) 48 H W. Roseburg Avenue, West of Del Rey Avenue Wet Only 2 24 Notes: Source: Sanitary Sewer Flow Monitoring, V&A Consulting Engineers, Inc. (2014/2015). ---PAGE BREAK--- ---PAGE BREAK--- R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LSR7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LSR7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS R7 LS KIERNAN AVE COVERT RD BACON RD BECKWITH RD NORTH AVE WOODLAND AVE MAZE BLVD CALIFORNIA AVE PARADISE RD WHITMORE AVE SHOEMAKE AVE BLUE GUM AVE KANSAS AVE STODDARD RD AMERICAN AVE TULLY RD MC HENRY AVE COFFEE RD OAKDALE RD ROSELLE AVE CLAUS RD LANGWORTH RD CARVER RD DALE RD PRESCOTT RD FINNEY RD ALBERS RD Detail A RG North RG East RG West RG South !(Site G (CSL) ?Î R7 LS Site 1-3 Site 1-4 Site 1-5 Site 2-3 Site 3-1 Site 4-1 Site 4-4 Site 5-1 Site 5-3 Site 5-5 Site 6-1 Site 6-3 Site 6-5 Site 6-6 Site 6-7 Site 6-8 Site 6-9 Site 6-10 Site 10-1 Site B Site C Site D Site 1-2 Site 2-2 Site 2-4 Site 2-5 Site 2-6 Site 4-2 Site 4-3 Site 5-4 Site A Site E Site 1-1 Site 2-1 Site 7-1 Site 7-B Site 7-2 (CSL) Site 8-1 Site 9-1 Site 5-2 Site 6-4 Site F FLOW MONITORING LOCATIONS FIGURE 3.1 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN Legend Rain Gauge Flow Monitoring Location Dry Weather Only Dry and Wet Weather Wet Weather Only R7 LS Lift Station Sewer Pipelines 8" or Smaller 10" or Larger Flow Monitoring Tributary Areas Roads O 0 1 2 Miles R7 LS Site 4-3 Site 4-2 Site 6-1 Site 5-1 Site 4-4 Site G (CSL) Site 4-1 Detail A R7 LS pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Data/MXDs/Fig 3_1.mxd ---PAGE BREAK--- ---PAGE BREAK--- Sutter Plant Legend Site 1-1 (5.35 mgd) Flow Meter (Measured DWF) Flow Split Flow Direction Site A (0.52 mgd) Site 1-3 (1.28 mgd) Site 1-2 (4.21 mgd) Site 1-5 (5.24 mgd) Site 1-1 (5.35 mgd) Site 2-1 (3.52 mgd) Site 3-1 (1.09 mgd) Site B (0.24 mgd) Site 2-2 (2.64 mgd) Site 2-3 (0.56 mgd) Site 2-6 (0.13 mgd) Site 1-4 (1.17 mgd) Site 10-1 (1.41 mgd) Site E (0.13 mgd) Site 2-4 (1.68 mgd) Site 2-5 (0.72 mgd) Site 6-1 (3.53 mgd) Site 4-1 (0.03 mgd) Site 4-2 (1.11 mgd) Site 4-4 (0.001 mgd) Site 4-3 (0.25 mgd) Site 7-1 (5.28 mgd) Site 5-2 (2.03 mgd) Site 5-3 (1.09 mgd) Site 5-4 (0.46 mgd) Site 5-5 (0.61 mgd) Site 6-4 (3.22 mgd) Site 7-B (0.18 mgd) Site 6-5 (2.87 mgd) Site 6-7 (1.24 mgd) Site 6-3 (1.74 mgd) Site 6-10 (0.31 mgd) Site 6-8 (0.63 mgd) Site 6-9 (0.97 mgd) Site 6-6 (1.39 mgd) Site D (10.0 mgd) Site 5-1 (7.67 mgd) Site 7-2 CSL (0.85 mgd) Site 9-1 (0.28 mgd) Site C (0.06 mgd) Site 8-1 (0.81 mgd) FLOW MONITORING SCHEMATIC FIGURE 3.2 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN Tributary Area Area 1 Area 2 Area 3 Area 4 Area 5 Area 6 Area 8/ North Ceres Area 9 Area 10 Area 7 Site G CSL (0.77 mgd) Site H (0.42 mgd) Site F (0.89 mgd) pw://Carollo/Documents/Client/CA/Modesto/9704A00/Data/FM Schematic ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 3-6 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH03/Ch03 CS.doc 3.1.2 Rainfall Monitoring V&A recorded data from three significant storm events that occurred on December 11, 2014, December 15, 2014, and February 6, 2015. For each storm, rainfall data were collected from four rain gauges installed by V&A. The locations of these gauges are shown in Figure 3.1 and summarized in Table 3.2. In addition, V&A used rainfall data from permanent rain gauges in the area the airport and the Modesto Irrigation District offices downtown) to validate the rainfall data recorded by the V&A rain gauges. Table 3.2 Rain Gauge Locations Wastewater Collection System Master Plan City of Modesto, California Rain Gauge Operator Location RG North V&A Next to Beyer Park RG East V&A Northeast of Lakewood Avenue and Scenic Drive RG South V&A Near Bret Harte Park RG West V&A N. Carpenter Road and Rosemore Avenue 3.2 WASTEWATER FLOW COMPONENTS This section defines the terminology used for the hydraulic analysis of the wastewater collection system. Figure 3.3 illustrates the various components of wastewater flow. 3.2.1 Inflow and Infiltration (I/I) All collection systems receive some I/I. For an illustration of the most common sources, consult Figure 3.4. Infiltration refers to storm water flows that enter the collection system by percolating through the soil and then through defects in pipelines, manholes, and joints. Examples of infiltration include cracks in pipelines, misaligned joints, and root penetration. Inflow, on the other hand, refers to storm water that enters the collection system via a direct connection to the system. Examples of inflow include roof drain and downspout connections, leaky manhole covers, and illegal storm drain connections. When I/I enters a collection system, it can cause problems by increasing flow volume and peak flows. If too much I/I enters the collection system, sanitary sewer overflows (SSO) can occur. Figure 3.5 illustrates the effects of I/I on a collection system. ---PAGE BREAK--- ---PAGE BREAK--- Pl205f1-6825.cdr Figure 3.3 WASTEWATER FLOW COMPONENTS WASTEWATER COLLECTION SYSTEM MASTER PLAN CITY OF MODESTO Base Wastewater Flow Dry Weather Flow Dry Weather Flow Infiltration Infiltration Inflow Inflow Dry Weather Ground Water Infiltration Storm Water Inflow Trench Infiltration Ground Water Infiltration Rainfall Dependent Inflow and Infiltration Total Flow Time (Days) 1 2 3 4 5 6 7 NOV DEC JAN FEB MAR APR MAY JUN Month Rain Rainfall Dependent Infiltration and Inflow (RDI/I) ( ) Average Dry Weather Flow (ADWF) Groundwater Infiltration (seasonal mounding) Flow Rain Seasonal Weekly Flow Rain Inflow Sanitary Dry Weather Flow Infiltration Groundwater Infiltration Inflow SWI + + = = Infiltration TI RDI/I Rainfall Dependent Infiltration & Inflow (RDI/I) = Rain Pl205f1-6825.cdr 3-18 Figure 3.8 TYPICAL WASTEWATER FLOW COMPONENTS DISTRICT-WIDE MASTER PLAN WEST COUNTY WASTEWATER DISTRICT Note: This figure is not based on flow data specific to the City or this Master Plan TYPICAL WASTEWATER FLOW COMPONENTS FIGURE 3.3 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- ---PAGE BREAK--- Leaky Building Lateral Foundation Drain Connected to Building Lateral Exfiltration from Storm Drain Sanitary Sewer LEGEND Cracked or Broken Pipe Red Lettering is Infiltration Deteriorated or Misaligned Joint Faulty Lateral Connection to Sanitary Sewer Illicit Catch Basin Connection Manhole Cover with Holes Blue Lettering is Inflow Storm Drain Deteriorated Manhole Faulty Manhole Frame/ Chimney Seal Root Penetration Roof Vent Downspout Area Drain Service Line Cleanout (uncapped) Driveway Drain Stairwell Drain Foundation Drain Floor Drain Pl205f2-6825.cdr Figure 3.4 CITY OF MODESTO TYPICAL SOURCES OF INFILTRATION AND INFLOW WASTEWATER COLLECTION SYSTEM MASTER PLAN 3-21 Figure 3.9 TYPICAL SOURCES OF INFILTRATION AND INFLOW DISTRICT-WIDE MASTER PLAN WEST COUNTY WASTEWATER DISTRICT TYPICAL SOURCES OF INFILTRATION AND INFLOW FIGURE 3.4 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- ---PAGE BREAK--- Trench Infiltration Groundwater Infiltration Inflow Dry Weather Flow Sewer Lateral Flow 2 1 3 5 days 0 4 Due to Infiltration and Inflow Average Dry Weather Flow Average Dry Weather Flow pL205F3-6825.cdr Figure 3.5 CITY OF MODESTO EFFECTS OF INFILTRATION AND INFLOW WASTEWATER COLLECTION SYSTEM MASTER PLAN 3-22 Figure 3.10 TYPICAL EFFECTS OF INFILTRATION AND INFLOW DISTRICT-WIDE MASTER PLAN WEST COUNTY WASTEWATER DISTRICT TYPICAL EFFECTS OF INFILTRATION AND INFLOW FIGURE 3.5 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 3-10 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH03/Draft Final - Ch03 CS.doc 3.2.2 Base Wastewater Flow (BWF) Base wastewater flow (BWF) is flow generated by the City's residential, commercial, and industrial customers without I/I. BWF has a diurnal pattern that varies with land use categories. Typically, a residential diurnal pattern has two peaks, with a more pronounced peak occurring in mid-morning and a less pronounced peak occurring in the evening. Although commercial and industrial patterns vary depending on their type of water use, they usually have more consistent higher flow patterns during business hours and lower flows at night. Furthermore, the diurnal flow pattern experienced during a weekend may vary compared to the diurnal flow experienced during a weekday. 3.2.3 Groundwater Infiltration (GWI) Groundwater infiltration (GWI) is extraneous groundwater that enters the sewer system through defects in pipes and manholes. Groundwater levels and the condition of sewer pipes and manholes affect the degree of GWI that occurs. Additionally, while GWI may occur throughout the year (for example, in areas of heavy agricultural irrigation), GWI rates are typically higher in the late winter and early spring. Since dry weather GWI (or base infiltration) is not easily separated from BWF using flow measurement techniques, it is typically grouped with BWF. 3.2.4 Annual Average Flow (AAF) The annual average flow (AAF) is the average flow measured at the Sutter Plant over a one-year period, including dry and wet weather periods. The AAF includes BWF and GWI. 3.2.5 Average Dry Weather Flow (ADWF) Average dry weather flow (ADWF) is the average flow that occurs during the dry weather season. This includes BWF and dry weather GWI. For this Master Plan, ADWF was calculated based on historical flow data at the Sutter Plant and dry weather flow data from the flow monitoring program. 3.2.6 Peak Dry Weather Flow (PDWF) Peak dry weather flow (PDWF) is the highest observed hourly flow that occurs during the dry weather season. For this Master Plan, PDWF was not used to evaluate the collection system. 3.2.7 Maximum Day Wet Weather Flow Maximum day wet weather flow is the highest daily flow that occurs during the wet weather season (defined as October through May for this Master Plan). The Water Environment Federation (WEF) Manual of Practice FD-6 and the American Society of Civil Engineers (ASCE) Manual and Report on Engineering Practice No. 62 suggest the ratio of to ADWF typically ranges between 2.0 and 3.0, even in well-constructed systems. ---PAGE BREAK--- April 2016 - FINAL DRAFT 3-11 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH03/Draft Final - Ch03 CS.doc This is because higher values usually indicate a more pronounced I/I problem. At the Sutter Plant, the on the wettest day in 2014 (December 11) was 35.4 mgd, which translates to an to ADWF ratio of 1.73. This indicates that, overall, the collection system has low I/I rates. 3.2.8 Peak Wet Weather Flow (PWWF) Peak wet weather flow (PWWF) is the highest observed flow that occurs following a design storm event. Increased flow in the collection system may be due to wet weather I/I. Because PWWF is used to design sewers and lift stations, PWWF and Design Flow are synonymous and will be used interchangeably throughout this report. 3.3 FLOW MONITORING RESULTS This section summarizes the results of the flow monitoring program, including dry weather flow data, rainfall data, and wet weather flow data. Data collected from Meter 2-2 is presented throughout this chapter as an example of the type of data and results derived from the flow monitoring program. For data summaries of the remaining meter sites, refer to Appendix C. 3.3.1 Dry Weather Data Depth and velocity data were collected at each meter at 15-minute intervals during flow monitoring periods. These data were then aggregated into hourly data. From the hourly data, characteristic dry weather 24-hour diurnal flow patterns for each site were developed and then used to calibrate the hydraulic model for ADWF. Calibration of the hydraulic model (comparing actual flows to modeled flows) is discussed in Chapter 4. Since diurnal flow patterns are different on weekdays than on weekends, each pattern was analyzed separately to better understand the overall dry weather flow patterns. To estimate the weekday and weekend dry weather flows, V&A used the data from days least affected by rainfall. In addition, V&A estimated the average weekday and weekend levels and velocities at each site, which were used for dry weather flow calibration. Figure 3.6 illustrates a typical variation of the City’s weekday and weekend flow, which is based on the data collection from Site 2-2. Similar graphics associated with the remaining sites are included in Appendix C. Table 3.3 summarizes the dry weather flows at each meter. As shown in the table, the total of the individual flow meters during the monitoring period was 21.4 mgd. A comparison of field-measured flows and the flows measured by the Sutter Plant influent flow meter is presented in Chapter 5. ---PAGE BREAK--- 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 Flow (mgd) Time (hours) Mon.-Thurs. Fri. Sat. Sun. TYPICAL WEEKDAY VS. WEEKEND DRY WEATHER FLOW VARIATION (SITE 2-2) FIGURE 3.6 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 3-13 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH03/Draft Final - Ch03 CS.doc Table 3.3 Dry Weather Flow Summary Wastewater Collection System Master Plan City of Modesto, California Monitor Site Dry Weather Flow (Mon – Thur) (mgd) (Friday) (mgd) (Saturday) (mgd) (Sunday) (mgd) Overall (mgd) 1-1 5.32 5.29 5.44 5.42 5.35 1-2 4.14 4.13 4.36 4.42 4.21 1-3 1.24 1.27 1.37 1.35 1.28 1-4 1.14 1.16 1.21 1.23 1.17 1-5 5.23 5.21 5.28 5.23 5.24 2-1 3.53 3.51 3.54 3.48 3.52 2-2 2.67 2.62 2.65 2.59 2.64 2-3 0.56 0.57 0.57 0.58 0.56 2-4 1.70 1.68 1.66 1.63 1.68 2-5 0.72 0.71 0.69 0.74 0.72 2-6 0.13 0.13 0.13 0.13 0.13 3-1 1.10 1.10 1.06 1.08 1.09 4-1 0.04 0.03 0.03 0.03 0.03 4-2 1.15 1.19 0.93 1.05 1.11 4-3 0.26 0.25 0.23 0.24 0.25 4-4 0.00 0.00 0.00 0.00 0.00 5-1 7.89 6.94 7.34 7.85 7.67 5-2 2.04 1.99 2.01 2.05 2.03 5-3 1.08 1.04 1.10 1.20 1.09 5-4 0.47 0.44 0.43 0.47 0.46 5-5 0.61 0.61 0.60 0.59 0.61 6-1 3.54 3.45 3.46 3.67 3.53 6-3 1.89 1.82 1.34 1.43 1.74 6-4 3.17 3.00 3.31 3.55 3.22 6-5 2.86 2.80 2.78 3.06 2.87 6-6 1.36 1.34 1.43 1.50 1.39 6-7 1.22 1.21 1.28 1.30 1.24 6-8 0.63 0.62 0.64 0.67 0.63 6-9 0.96 0.93 0.99 1.03 0.97 ---PAGE BREAK--- April 2016 - FINAL DRAFT 3-14 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH03/Draft Final - Ch03 CS.doc Table 3.3 Dry Weather Flow Summary Wastewater Collection System Master Plan City of Modesto, California Monitor Site Dry Weather Flow (Mon – Thur) (mgd) (Friday) (mgd) (Saturday) (mgd) (Sunday) (mgd) Overall (mgd) 6-10 0.31 0.30 0.31 0.33 0.31 7-1 5.31 4.86 5.04 5.79 5.28 7-2(3) 0.88 0.88 0.79 0.75 0.85 7-B 0.20 0.18 0.16 0.14 0.18 8-1 0.83 0.86 0.75 0.75 0.81 9-1 0.29 0.28 0.26 0.25 0.28 10-1 1.43 1.34 1.39 1.41 1.41 A 0.51 0.52 0.54 0.54 0.52 B 0.24 0.25 0.23 0.23 0.24 C 0.06 0.06 0.06 0.06 0.06 D 10.03 10.70 9.74 9.71 10.04 E 0.13 0.13 0.12 0.12 0.13 F - - - - - Total Influent(4) 21.41 21.93 21.17 21.10 21.41 Notes: Source: Sanitary Sewer Flow Monitoring, V&A Consulting Engineers, Inc. (2014). Overall Dry Weather Flow = x Monday - Thursday)+(Friday)+(2 x Weekend))/7. Cannery Segregation Line (CSL). Represents the sum of flow monitoring sites 1-1, 2-1, 3-1, 10-1, and D. 3.3.2 Rainfall Data Over the course of the wet weather flow monitoring period, three significant rainfall events and a few relatively minor events occurred. Figure 3.7 illustrates the total accumulation of rainfall during this period according to the four rain gauges. Figure 3.8 shows the average rain events for all four gauges over the period. Table 3.4 summarizes the total rainfall recorded during the three main rainfall events and over the entire flow monitoring period. ---PAGE BREAK--- 6.26 6.05 5.69 5.24 RAINFALL ACCUMULATION PLOT FIGURE 3.7 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- ---PAGE BREAK--- 0.00 0.10 0.20 0.30 0.40 0.50 0.60 Rainfall (in/hr) RAINFALL ACTIVITY DURING FLOW MONITORING PERIOD FIGURE 3.8 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 3-17 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH03/Draft Final - Ch03 CS.doc Table 3.4 Rainfall Event Summary Wastewater Collection System Master Plan City of Modesto, California Storm Event RG North (inch) RG East (inch) RG South (inch) RG West (inch) Average (inch) December 11 3.16 2.49 3.04 3.01 2.93 December 15 0.97 0.84 1.05 0.99 0.96 February 6 1.28 1.04 1.16 0.88 1.09 December 11 – 20, 2014 4.68 3.76 4.59 4.60 4.41 Total Over Monitoring Period (Dec 11 – Mar 01) 6.26 5.24 6.05 5.69 5.81 Notes: Source: Sanitary Sewer Flow Monitoring, V&A Consulting Engineers, Inc. (2015). The historical average rainfall for the month of December is 2.05 inches. This data, which averages rainfall totals between the years 1906 and 2015, was taken from the Western Regional Climate Center (WRCC) at Station 045738 in Modesto. The historical average rainfall indicates that the events that occurred from December 11, 2014, to December 20, 2014 (4.41 inches), produced approximately twice the average rainfall during December. Thus, the December 11th rainfall event can be classified as a 50-year, 24-hour storm event, while the December 15th event is less than a 1-year storm event. 3.3.3 Wet Weather Flow Data V&A evaluated the flow monitoring data to quantify the collection system's response to wet weather events. Because the rainfall event that occurred on December 11, 2014, captured the largest I/I response during the flow monitoring period, it was selected for the I/I analysis. Figure 3.9 shows an example of the wet weather response at Site 2-2 during the December 11th rainfall event. The volume of I/I that entered the system from the collection system upstream of Site 2-2 is also illustrated in Figure 3.9. The light blue area is the base wastewater flow, and the gray area is the measured wet weather flow from the flow monitoring period. As shown, discernible amounts of I/I enter the system during wet weather events. Similar graphs were generated for the remaining monitoring sites and are shown in Appendix C. The flow monitoring data were used to conduct an analysis of the system’s I/I response. Typically, the metric used to quantify the severity of the system’s I/I is the R-Value, which is defined as the percentage of rainfall volume that enters the collection system as I/I. Table 3.5 summarizes the results for the December 11, 2014, rainfall event. As shown, the R- Values vary from 0.5 percent in Basin 10 to 7.7 percent in Basin 7. The City’s overall R- Value for the rainfall event was roughly 2.2 percent. In general, an R-Value of 5 percent or higher is considered significant. ---PAGE BREAK--- 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 11-Dec 12-Dec 13-Dec 14-Dec 15-Dec 16-Dec 17-Dec Rainfall (in./hr.) Flow (mgd) WWF DWF Rain EXAMPLE WET WEATHER FLOW RESPONSE (SITE 2-2) FIGURE 3.9 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- April 2016 - FINAL DRAFT 3-19 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH03/Draft Final - Ch03 CS.doc The R-Value is determined by isolating I/I from each individual flow monitoring basin (excluding flows from upstream flow monitors) and calculating the ratio of the volume of water that enters the system as I/I versus the volume of rainfall over the tributary area. In some cases, flow splits and/or overflows affect the calculated R-Value for certain tributaries and can skew the results. In these cases, tributary areas that cannot be isolated are combined. Another important metric used to quantify the severity of the system’s I/I response is the peak I/I rate, which is calculated by subtracting the BWF from the peak flow measured during Event 1. As shown in Table 3.5, the measured ratio of peak I/I rate to dry weather flow ranged from 1.36 in Basin 5 to 16.2 in Basin 7. Citywide, the ratio of peak I/I rate to dry weather flow from Event 1 was 4.42. It should be noted, however, that the peak I/I rates presented in Table 3.5 are for Event 1 only, which was classified as a 50-year, 24-hour storm event. Therefore, the peak I/I rate during the design 10-year storm event will be lower. Table 3.5 Wet Weather Flow Summary (Storm Event 1) Wastewater Collection System Master Plan City of Modesto, California Basin DWF (mgd) Estimated Total I/I (gallons) R- Value Peak I/I Rate (mgd) Peak I/I to DWF Ratio Basin 1 5.91 5,254,000 1.1 8.25 1.40 Basin 2 2.77 4,534,600 1.7 7.35 2.66 Basin 3 1.26 1,281,000 1.0 2.05 1.63 Basin 4 1.18 3,258,000 5.4 6.35 5.37 Basin 5 2.10 1,344,000 0.8 2.85 1.36 Basin 6 4.70 3,061,000 0.9 6.70 1.43 Basin 7 0.62 2,719,000 7.7 10.0 16.2 Basin 8 0.80 963,000 1.4 2.12 2.65 Basin 9 0.19 332,000 1.0 0.70 3.68 Basin 10 0.33 230,000 0.5 0.61 1.85 Basin CSL 0.73 1,701,000 n/a 4.37 5.99 ---PAGE BREAK---