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April 2016 - FINAL DRAFT 4-1 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Chapter 4 COLLECTION SYSTEM FACILITIES AND HYDRAULIC MODEL This chapter presents an overview of the City of Modesto’s (City) wastewater collection system and describes the update and calibration of its wastewater collection system hydraulic model. A summary of the hydraulic model calibration steps, standards, and results for both dry and wet weather conditions is also provided. 4.1 WASTEWATER TREATMENT FACILITIES The City has two wastewater treatment facilities that treat domestic and commercial wastewater: the Sutter Avenue Primary Treatment Plant (Sutter Plant) and the Jennings Road Secondary Treatment Plant (Jennings Plant). Raw (untreated) wastewater collected by the sanitary sewer system flows to the Sutter Plant to undergo primary treatment. The primary effluent is then conveyed to the Jennings Plant through a 6.5-mile long outfall pipeline (the Primary Domestic Outfall). The Jennings Plant facilities include a secondary treatment train, a tertiary treatment train, and 2,458 acres of agricultural property used for the land application of treated municipal effluent, cannery process water, and anaerobically digested biosolids from the Sutter Plant. Currently, cannery process water is segregated from the domestic wastewater flows during canning season. The Cannery Segregation Line (CSL) trunk sewer consists of approximately 8 miles of gravity sewer that conveys the cannery process water from the Beard Industrial Park directly to the Sutter Plant. The cannery process water is then conveyed to City-owned agricultural land at the Jennings Plant via the Can Seg Outfall, where it is combined with secondary effluent and used to irrigate the ranch land. For more detail on the City's wastewater treatment facilities, see the Wastewater Treatment Master Plan. 4.2 SEWER SERVICE AREA The study area and the existing wastewater collection system are generally divided into ten major sewer service tributary areas, which are shown in Figure 4.1. In this Master Plan, further discussions of capital projects are grouped according to their sewer service area. The following list describes each of the ten sewer service areas: • Area 1: Area 1 is located in the City’s west and northwest sections, where approximately half of its Comprehensive Planning Districts (CPDs) are located. Because of this, much of the growth and increased wastewater flow will occur in this area’s collection system. The primary truck lines that convey wastewater from this area to the Sutter Plant are the North Trunk and West Trunk. The North Trunk runs east to west along Bangs Ave and connects to the West Trunk at the intersection of ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-2 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc American Avenue and Bangs Avenue. The West Trunk begins in American Avenue, continues south to Paradise Road, and terminates at the Sutter Plant. • Area 2: Area 2 is located in the City’s north-central section. The portion of this area northeast of Highway 99 is nearly built-out. However, the area southwest of Highway 99 will experience some redevelopment, infill development, and potential connections from unincorporated County islands. Currently, Area 2 experiences significant increases in peak wet weather flow (PWWF) because direct storm drain connections to the wastewater collection system cause flow to spike after a storm event. The primary trunk line that conveys flow in this tributary area is the Emerald Trunk. • Area 3: Area 3 is located in the City’s central section. Although this area is primarily built-out, it will experience some redevelopment, infill development, and potential connections from unincorporated County islands. Like Area 2, Area 3 experiences increases in PWWF because of direct storm connections to the wastewater collection system. In this tributary area, the primary trunk that conveys flow is the Sutter Trunk. • Area 4: Area 4 encompasses the downtown area of the collection system. The City has identified areas of downtown likely to experience redevelopment or development intensification. The redevelopment plans call for a densification of the development, which will increase the wastewater generated from the area. Like other areas, Area 4 experiences increases in PWWF attributed to the direct storm connections to the wastewater collection system. This area contains several trunks, but the primary trunk lines that convey flow are the J, H, D, 6th, 7th, and 9th Street Trunks. • Area 5: Area 5 is located immediately east of downtown. The Rose/Celeste Lift Station, Rose/Celeste Trunk, and Santa Rosa Trunks serve this area. • Area 6: Area 6 is located in the City’s eastern section. As development within the City limits continues and CPDs are approved for annexation, this area is expected to grow significantly. The Sonoma and Lakewood Trunks serve customers north of the Scenic Lift Station in Area 6. South of the Scenic Lift Station, all wastewater flow is conveyed through the River Trunk. The River Trunk then conveys flow to the Sutter Plant for Areas 4, 5, 6, 7, 8, and 9. The CSL also runs parallel to the River Trunk and serves several large dischargers in the Beard Industrial Park within Area 6. • Area 7: Area 7 is a small industrial section located south of Area 5. The primary trunk servicing this area is the River Trunk. • Area 8: Area 8 is located in the City’s south-central section and includes the north Ceres area served by the Sutter Plant. The Ceres Trunk serves Area 8 and conveys flow to the River Trunk. • Area 9: Area 9 is located in the City’s southern section and consists primarily of industrial land uses. This area is served by the Spokane Trunk and could include future flows from developed County islands. ---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 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 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 HWY 99 HWY 99 HWY 99 BRIGGSMORE AVE 9TH ST SYLVAN AVE PELANDALE AVE BANGS AVE North Trunk Rumble Trunk Rose\Celeste Trunk Sonoma Trunk Lakewood Trunk Empire Trunk Cannery Segregation Line South Trunk Sutter Plant Sutter Trunk Emerald Trunk West Trunk Santa Rosa Trunk River Trunk ?Î R7 LS R7 LS R7 LS 10'' 18'' 45'' 21'' 18'' 10'' 15'' 27'' 18'' 15'' 36'' 30'' 66'' 18'' 12'' 15'' 10'' 10'' 48'' 27'' 30'' 12'' 15'' 10'' 45'' 10'' 21'' 18'' 48'' 15'' 39'' 12'' 30'' 21'' 14'' 30'' 30'' 12'' 27'' 10'' 24'' 60'' 10'' 10'' 51'' 12'' 10'' 24'' 36'' 12'' 24'' 10'' 10'' 54'' 10'' 30'' 33'' 15'' 33'' 10'' 10'' 36'' 12'' 18'' 12'' 18'' 10'' 12'' 18'' 21'' 27'' 10'' 26'' 15'' 18'' 18'' 24'' 12'' 18'' 10'' 18'' 10'' 39'' 12'' 15'' 12'' 12'' 15'' 12'' 12'' 30'' 32'' 12'' 24'' 12'' 18'' 36'' 18'' 10'' 10'' 10'' 12'' 12'' 18'' 32'' 10'' 15'' 12'' 12'' 15'' 15'' 21'' 15'' 12'' 18'' 30'' 10'' 10'' 10'' 10'' 10'' 18'' 10'' 12'' 10'' 15'' 15'' 33'' 12'' 18'' 12'' 10'' 10'' 15'' 15'' 10'' 10'' 12'' 12'' 24'' 24'' 12'' 27'' 16'' 16'' 10'' 10'' 30'' 12'' 36'' 33'' 10'' 15'' 30'' 18'' 30'' 27'' 48'' 24'' 30'' 42'' 27'' 27'' 54'' 12'' 24'' 12'' 36'' 33'' 36'' 12'' 39'' 30'' 60'' 21'' 60'' 16'' 10'' 15'' 10'' EXISTING WASTEWATER COLLECTION SYSTEM FIGURE 4.1 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN Legend Sewer Main 8" or Smaller 9" to 18" 20" to 36" Larger than 36" R7 LS Lift Station Private Sewer Main R7 LS Private Lift Station Roads Sewer Tributary Areas Area 1 Area 2 Area 3 Area 4 Area 5 Area 6 Area 7 Area 8/Northern Ceres Area 9 Area 10 O 0 1 2 Miles Beard Industrial Park Empire North Ceres R7 LS pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Data/MXDs/Fig 4_1.mxd ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-4 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc • Area 10: Area 10 is located in the City’s southwest section and conveys flow through the Imperial and South Trunks. The land uses in this area consist of residential, commercial, industrial, and village residential. This area will grow as the Fairview CPD is developed. 4.3 COLLECTION SYSTEM FACILITIES The existing wastewater collection system consists of approximately 618 miles of sanitary sewer lines ranging in diameter from 4 inches to 66 inches, as well as 40 wastewater lift stations and 60 storm drain connections. The City's existing collection system is shown in Figure 4.1. Table 4.1 summarizes the total length of pipe for each diameter in the domestic collection system and the CSL. The table is based on geographic information system (GIS) data provided by City Staff and includes newly installed pipelines along Litt Road and Pelandale Avenue as well as the Parklawn Lift Station force main. These pipelines are currently dry and are not in service yet. The table excludes north Ceres, County sewers, and private sewer lines within the study area. 4.3.1 Major Trunk Sewers As shown in Figure 4.1, five major trunk lines convey flows to the Sutter Plant: the West Trunk, Emerald Trunk, Sutter Trunk, River Trunk, and South Trunk. These trunk sewers range in diameter from 10 inches to 66 inches. In addition to these trunk lines, the CSL conveys cannery process water from the Beard Industrial Park to the Sutter Plant. 4.3.2 Lift Stations The City operates and maintains 40 wastewater lift stations. Of these lift stations, 21 were incorporated into the collection system hydraulic model. Although the City does not own and operate the North Gate and County Lift Stations, these lift stations were also included in the lift station analysis. However, small lift stations that drain small tributary areas were not modeled. Table 4.2 summarizes the design data for the City’s lift stations. 4.3.3 Storm Drain Cross Connections In areas without permanent storm drain systems, the City uses the sanitary sewer to convey storm water runoff. Because storm runoff is routed directly to the collection system, these cross connections cause dramatic increases in PWWF after a storm event. Figure 4.2 identifies the locations of 60 known storm drain cross connections determined by the City's GIS data. Most of the discharge points are located within the downtown area and in northwest Modesto. As shown on Figure 4.2, three storm drain cross connections are planned for removal. ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-5 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Table 4.1 Collection System Sewer Size Summary Wastewater Collection System Master Plan City of Modesto, California Diameter (inches) Length (feet) Diameter (inches) Length (feet) Domestic Sanitary Sewer CSL 4 4,300 12 2,200 6 1,934,300 18 2,100 8 608,700 21 100 10 169,300 24 3,100 12 119,900 30 1,200 14 1,600 36 2,800 15 57,100 42 3,900 16 13,000 48 14,100 18 55,800 54 6,000 20 700 60 3,700 21 20,200 66 3,000 24 32,100 26 1,800 27 32,200 30 52,800 32 9,700 33 39,700 36 17,800 39 18,500 42 1,600 45 7,500 48 11,500 51 7,200 54 19,700 60 18,500 66 3,700 Unknown 1,800 Total (feet) 3,261,000 Total (feet) 42,200 Total (miles) 618 Total (miles) 8 ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-6 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Table 4.2 Lift Station Information Wastewater Collection System Master Plan City of Modesto, California Lift Station ID Pump Number Pump Capacity (gpm) Total Capacity Firm Capacity (gpm) (mgd) (gpm) (mgd) Athens(1) 1 1 250 250 0.36 250 0.36 Beardbrook 2 1 250 250 0.36 250 0.36 Benson(1) 3 1 2 150 500 650 0.94 150 0.22 California(1) 5 1 2 400 400 800 1.15 400 0.58 Carver & Scott(1) 6 1 2 600 600 1,200 1.73 600 0.86 Carver & Standiford(1) 7 1 2 400 400 800 1.15 400 0.58 Cheyenne & Dutch Hollow 8 1 2 300 300 600 0.86 300 0.43 Clayton & N. Martin 10 1 2 350 350 700 1.01 350 0.50 Coldwell & N. Olive(1) 11 1 2 200 200 400 0.58 200 0.29 College & Orangeburg(1) 14 1 226 226 0.33 226 0.33 El Terino & Fairmont(1) 15 1 220 220 0.32 220 0.32 Codoni 16 1 2 870 870 1,740 2.51 870 1.25 Emerald(1) 17 1 2 3 2,800 2,800 4,500 10,100 14.54 5,600 8.06 Evergreen & Gay 18 1 240 240 0.35 240 0.35 Hahn(1) 19 1 2 700 700 1,400 2.02 700 1.01 La Loma(1) 21 1 2 300 300 600 0.86 300 0.43 Mark Randy 22 1 157 157 0.23 157 0.23 Maze & Spencer 23 1 2 178 178 356 0.51 178 0.26 Muriel 25 1 2 177 177 354 0.51 177 0.25 Northgate(1),(3) 26 1 2 242 242 484 0.70 242 0.35 ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-7 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Table 4.2 Lift Station Information Wastewater Collection System Master Plan City of Modesto, California Lift Station ID Pump Number Pump Capacity (gpm) Total Capacity Firm Capacity (gpm) (mgd) (gpm) (mgd) Pepsi 27 1 2 265 265 530 0.76 265 0.38 Phoenix & Edgebrook 28 1 100 100 0.14 100 0.14 Rose & Celeste(1) 29 1 2 600 600 1,200 1.73 600 0.86 Rumble(1) 30 1 2 950 950 1,900 2.74 950 1.37 Scenic(1) 31 1 2 3 1,000 1,000 5,000 7,000 10.08 2,000 2.88 Thousand Oaks(1) 32 1 2 3 4 2,300 3,675 2,300 3,675 11,950 17.21 8,275 11.9 2 Thousand Oaks Auxiliary 33 1 240 240 0.35 240 0.35 Torrid & Diablo 34 1 2 300 300 600 0.86 300 0.43 Trask & Encina 35 1 235 235 0.34 235 0.34 Tully & Davis 37 1 2 225 225 450 0.65 225 0.32 Woodland(1) 39 1 2 3 4 5 4,500 4,500 2,000 4,500 3,500 19,000 27.36 14,500 20.8 8 T.R.R.P 41 1 300 300 0.86 300 0.43 Fleur De Ville 45 1 2 100 100 200 0.29 100 0.14 Jefferson(1) 46 1 2 1,400 1,400 2,800 4.03 1,400 2.02 Centre Plaza Garage 48 Not available Centre Plaza North 49 1 2 300 300 600 0.86 300 0.43 Orangeburg Park 51 1 2 100 100 200 0.29 100 0.14 ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-8 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Table 4.2 Lift Station Information Wastewater Collection System Master Plan City of Modesto, California Lift Station ID Pump Number Pump Capacity (gpm) Total Capacity Firm Capacity (gpm) (mgd) (gpm) (mgd) Holiday Express 55 1 2 200 200 400 0.58 200 0.29 Coffee/Claratina(1) 58 1 2 1,000 1,000 2,000 2.88 1,000 1.44 County(1)(5) 59 Not available Fairview(1) 62 1 2 450 450 900 1.30 450 0.65 Parklawn(4) - Not available Notes: Lift station is included in the model. Emerald lift station is in the process of being replaced. Data in this table do not reflect the new lift station characteristics. Lift Station is privately owned. Lift Station is new and will become functional in 2016. County Lift Station is owned and operated by Stanislaus County and is located near the intersection of Hackett Road and Crows Landing Road. ---PAGE BREAK--- ---PAGE BREAK--- Planned for Removal Removed in late 2015 Planned for Removal Planned for Removal in 2017 STORM DRAIN CROSS CONNECTIONS FIGURE 4.2 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN Legend Sewer Main 8" or Less 9" to 18" 20" to 36" Larger than 36" Storm Drain Cross Connection Subcatchments Study Area Boundary O 0 2,500 5,000 Feet ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-10 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc 4.4 HYDRAULIC MODEL DEVELOPMENT This section summarizes the process for developing the hydraulic model, including a summary of the modeling software selection, a description of the modeled collection system, and elements of the hydraulic model. 4.4.1 Selected Hydraulic Modeling Software Before model calibration, a number of model updates were required to confirm that the modeled network accurately represented the sewer system. One update involved upgrading the City’s model software from H2OMAP Sewer to InfoSWMM®. Although Innovyze, Inc. supports both programs, H2OMAP Sewer is not a fully dynamic model and is therefore subject to limitations, such as the inability to model flow backup and surcharging that results from capacity bottlenecks. InfoSWMM®, on the other hand, offers a fully dynamic solution that more accurately represents flow conditions in a sewer system. Automated tools within InfoSWMM®, which perform functions such as calculating manhole invert elevations and pipe offsets from pipe invert elevations, assisted in the conversion process. 4.4.2 Modeled Collection System and Skeletonization Skeletonization is the process of stripping sewer systems of pipelines not considered essential for the intended purpose of the analysis. The purpose of skeletonizing a system is to develop a model that accurately simulates the hydraulics of a collection system while simultaneously simplifying a large and complex model. In sewer system master planning, it is common practice to exclude small diameter sewers when developing a hydraulic computer model. For the City’s hydraulic model, pipelines 10 inches in diameter or larger were included as well as some smaller diameter sewers (8 inches in diameter or smaller) where needed for connectivity. Otherwise, sewers 8 inches in diameter or smaller were excluded. The modeled sewer system consists of 21 sanitary lift stations and approximately 170 miles of sanitary sewer pipelines that range in diameter from 4 inches (smaller pipelines are force mains) to 66 inches. Figure 4.3 presents the City’s modeled wastewater collection system. Table 4.3 presents a summary of the modeled sewer system according to diameter and pipe length. ---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 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 ?Î Jefferson Coldwell & Olive Emerald Thousand Oaks Hahn Woodland Carver & Standiford Rumble Coffee & Claratina College & Orangeburg Scenic Carver & Scott Carver & Scott El Terino & Fairmont Athens Benson California Northgate Rose & Celeste County La Loma Fairview 10'' 21'' 15'' 16'' 21'' 45'' 10'' 18'' 18'' 12'' 12'' 10'' 10'' 10'' 60'' 10'' 30'' 30'' 30'' 16'' 60'' 42'' 10'' 24'' 10'' 10'' 33'' 18'' 12'' 10'' 54'' 10'' 10'' 30'' 36'' 24'' 18'' 10'' 12'' 24'' 26'' 18'' 12'' 10'' 27'' 27'' 24'' 12'' 15'' 10'' 21'' 12'' 27'' 18'' 15'' 10'' 45'' 18'' 18'' 39'' 33'' 12'' 15'' 15'' 12'' 30'' 36'' 36'' 24'' 12'' 36'' 27'' 51'' 10'' 12'' 39'' 12'' 10'' 10'' 10'' 15'' 10'' 21'' 30'' 15'' 12'' 12'' 15'' 18'' 12'' 12'' 33'' 15'' 12'' 10'' 10'' 54'' 12'' 10'' 15'' 16'' 15'' 12'' 24'' 15'' 12'' 15'' 15'' 27'' 27'' 30'' 36'' 48'' 10'' 48'' 15'' 21'' 18'' 33'' 18'' 10'' 10'' 66'' 24'' 30'' 27'' 24'' 42'' 27'' 60'' 24'' 48'' 30'' 24'' 10'' 27'' 18'' 60'' MODELED SEWER SYSTEM FIGURE 4.3 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN Legend R7 LS Lift Station Sewer Main 8" or Less 10" to 18" 21" and Larger Tributary Areas Area 1 Area 2 Area 3 Area 4 Area 5 Area 6 Area 7 Area 8/Northern Ceres Area 9 Area 10 O 0 4,000 8,000 Feet Beard Industrial Park Empire North Ceres pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Data/MXDs/Fig 4_3.mxd ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-12 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Table 4.3 Collection System Pipeline Used in Hydraulic Model Wastewater Collection System Master Plan City of Modesto, California Diameter (inch) Length (feet) Diameter (inch) Length (feet) 4 500 30 57,800 6 76,200 32 1,800 8 26,800 33 37,700 10 178,700 36 31,700 12 125,500 39 18,800 14 1,000 42 5,800 15 59,300 45 6,900 16 15,600 48 26,400 18 63,100 51 6,600 21 23,900 54 26,500 24 41,700 60 21,800 26 1,800 66 5,500 27 34,300 Total 895,700 Notes: Total length of modeled pipelines includes Modesto, north Ceres, County, and CSL. 4.4.3 Elements of the Hydraulic Model The following section provides a brief overview of the major elements of the hydraulic model and the required input parameters associated with each element: • Junctions: Junctions represent sewer manholes, cleanouts, pipeline intersections, and other locations where pipe size changes. Required inputs for junctions include rim elevation, invert elevation, and surcharge depth, which represent pressurized systems. Junctions also represent locations where flows are split or diverted between two or more links. • Pipes: Pipes represent gravity sewers and force mains. Input parameters for pipes include length, friction factor Manning’s n for gravity mains and Hazen Williams C for force mains), invert elevations, diameter, and whether the pipe is a force main. • Storage Nodes: Storage nodes typically represent lift station wet wells (although other storage basins can be modeled as storage nodes). Input parameters for storage nodes include invert elevation, wet well depth, and wet well cross sectional area. • Pumps: Pumps are included in the hydraulic model as links. Input parameters for pumps include pump curves and operational controls. • Outfalls: Outfalls represent areas where flow leaves the system. For sewer system modeling, an outfall typically represents the connection to the influent pump station at a wastewater treatment plant. ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-13 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc • Rain Gauges: Rain gauges are input into the hydraulic model to simulate historical or theoretical hourly rainfall events. • Subcatchments: Subcatchments represent the hydrologic units of land area. These areas have topography and drainage characteristics that direct surface runoff from known storm drainage cross connections to a single discharge point in the sewer system. Ultimately, subcatchment parameters determine how much stormwater inflow enters the sewer system. Other sources of flow into the system sanitary flows and rainfall-derived infiltration and inflow from sources other than the storm drain cross connection) are modeled as inflows. These inflows are described in the next bullet point. • Inflows: Below are the three sources of wastewater flow that can be injected into individual model junctions (and storage nodes): – External: External inflows can represent any number of flows that enter the collection system, such as metered flow data or groundwater inflow. External inflows are applied to a specific model junction by applying a baseline flow value and a pattern that varies the flow by hour, day, or month. – Dry Weather: Dry weather inflows simulate base sanitary wastewater flows and represent the average flow. Dry weather flows can be multiplied by up to four patterns that vary the flow by month, day, hour, and type of day weekday or weekend). The dry weather diurnal patterns are adjusted during the dry weather calibration process. – RDII: RDII flows are applied by assigning a unit hydrograph and a corresponding tributary area to a given junction. The unit hydrographs consist of several parameters that adjust the volume of RDII entering the system at a given location. These parameters are adjusted during the wet weather calibration process. 4.4.4 Wastewater Flow Allocation Determining the quantity of dry weather wastewater flows generated by a municipality and the way flows are distributed throughout the collection system are important components of the hydraulic modeling process. They are also important in maintaining and sizing sewer system facilities, both for future and present conditions. To determine the quantity and distribution of flows, wastewater flows are assigned to individual model junctions using various techniques depending on the type of data available. For the City’s hydraulic model, baseline wastewater flows were allocated (assigned to specific nodes) based on the City’s land use data and wastewater flow coefficients (described in detail in Chapter Both the flow coefficients and the land use data provide a means for transforming a specific land use category into an average dry weather flow. The process of allocating baseline wastewater flows consisted of four steps, which are described below: ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-14 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc • Step 1: The City’s service area was divided into 1,341 individual flow loading polygons that represent the geographic area in which flows enter a single model node trunk system manhole). In an all-pipe model, a loading polygon could be as small as a few parcels. In a skeletonized model, such as the City’s model, a loading polygon usually encompasses a particular subdivision or grouping of lots. • Step 2: Using a GIS software program, the loads were calculated by multiplying the appropriate flow coefficient by the land use acreage. • Step 3: The hydraulic model’s load allocation assigned the calculated average dry weather flow to the appropriate node in the sewer system model. • Step 4: The allocated loads were adjusted when necessary during the dry weather flow calibration process (see Section 4.5). This was done to closely match the actual measured dry weather flows recorded during the flow monitoring period. 4.4.5 Model Construction The City’s hydraulic model combines information about the wastewater collection system’s physical and operational characteristics and solves a series of mathematical equations to simulate pipe flows. The model construction process consisted of six steps, which are described below: • Step 1: The City’s GIS shape files for the sewer collection system were obtained. • Step 2: The GIS data were reviewed and formatted for easy import into the InfoSWMM® modeling platform. • Step 3: The GIS data were skeletonized to exclude gravity sewers 8 inches in diameter or smaller, except where they were needed for connectivity. • Step 4: The collection system pipeline and facility data were imported into the modeling software and verified. Physical and operational data for the City’s wastewater collection facilities were not available from the GIS data. The data, which included wet well dimensions, pump stations, and other special features, were input manually into the model based on available information. Pipelines and junctions with missing inverts or invert discrepancies were reviewed and also manually input or modified based on City records, field reconnaissance, and engineering judgment. Once all relevant data were input into the hydraulic model, the model was reviewed to verify that they were input correctly and that the flow direction and size of the modeled pipelines were logical. Additionally, the modeled lift stations were checked to verify that they operated correctly. ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-15 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc • Step 5: Dry weather wastewater flows were allocated to the appropriate model junctions. These flows were scaled up or down when necessary to match the dry weather flows recorded during the flow monitoring period. • Step 6: The hydraulic model’s run parameters were established, and the model was debugged. The user must set up the model’s run parameters at the beginning of the project. These run parameters include run dates, time steps, reporting parameters, output units, and the flow routing method. Once they are established, the model can be debugged to ensure that it runs without errors or warnings. 4.5 HYDRAULIC MODEL CALIBRATION Hydraulic model calibration is a crucial component of hydraulic modeling. Calibrating the model to match data collected during the flow monitoring program ensures the most accurate results possible. This process calibrates both dry and wet weather conditions. For this project, dry and wet weather monitoring occurred at various sites. Dry weather monitoring was conducted at 41 monitoring sites, and wet weather flow monitoring was conducted at 39 monitoring sites. Monitoring was also performed over different time periods. Dry weather monitoring occurred over a period of approximately three weeks in 2014, and wet weather monitoring occurred over a period of approximately 12 weeks. There are several purposes to calibrating both dry and wet weather flow. For dry weather flow (DWF), calibration ensures an accurate depiction of the base wastewater flow generated within the study area. The purpose of wet weather flow (WWF) calibration is to accurately simulate the peak and volume of infiltration/inflow (I/I) that enters the sewer system, which is done by calibrating the hydraulic model to a specific storm event or storm events. The amount of I/I is essentially the difference between the WWF and DWF components. For Modesto, the majority of I/I enters through storm drain connections to the sewer system located downtown and in northern areas. 4.5.1 Calibration Standards The hydraulic model was calibrated in accordance with international modeling standards established by the Wastewater Planning Users Group (WaPUG), a section of the Chartered Institution of Water and Environmental Management. These are generally agreed upon principles for model verification. The dry weather and wet weather calibration focused on meeting the recommendations for model verification contained in the “Code of Practice for the Hydraulic Modeling of Sewer Systems,” published by the WaPUG (WaPUG 2002). The recommendations in this book are summarized below: • Dry Weather Calibration Standards: Dry weather calibration should be carried out for two dry weather days, and the modeled flows and depths should be compared to ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-16 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc the field-measured flows and depths. Both the modeled and field-measured flow hydrographs should closely follow each other in both shape and magnitude. In addition to the shape, the flow hydrographs should meet the following criteria as a general guide: – The timing of flow peaks and troughs should be within one hour. – The peak flow rate should be within the range of ±10 percent. – The volume of flow (or the average rate of flow) should be within the range of ±10 percent. If applicable, care should be taken to exclude periods of missing or inaccurate data. • Wet Weather Calibration Standards: For at least two storm events that occur during the flow monitoring period, the model-simulated flows and depths should be compared to the field-measured flows and depths. The flow hydrographs for both events should closely follow each other in both shape and magnitude until the flow has substantially returned to dry weather flow rates. In addition to the shape, the flow hydrographs should meet the following criteria as a general guide: – The timing of the peaks and troughs should be similar for the duration of the events. – The peak flow rates at significant peaks should be in the range of +25 percent to -15 percent and should be generally similar throughout. – The volume of flow (or the average flow rate) should be within the range of +20 percent to -10 percent. For wet weather calibration, the WaPUG recommends the use of a single calibration period that incorporates a number of rainfall events. In other words, if the flow monitoring program captures several back-to-back storms, it may be preferable to use them as the calibration storms instead of calibrating two separate storms that occurred weeks or months apart. 4.5.2 Dry Weather Flow Calibration The list below outlines each stage of the DWF calibration process: • Divide the system into areas tributary to each flowmeter. The first step in the calibration process was to divide the City into flowmeter sub-basin areas. To do this, 41 sub-basin areas were created, one for each flowmeter from the temporary flow monitoring program. Chapter 3 includes a map showing the locations of each flow monitoring site and its associated tributary area as well as a schematic of the flow meters. ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-17 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc • Define flow volumes within each area. The next step was to define the flow volumes within each area, which was accomplished in the flow allocation step described above for model construction. • Create diurnal patterns to match the temporal distribution of flow. A diurnal curve is a pattern of hourly multipliers applied to the base flow to simulate the variation in flow that occurs throughout the day. For each flow monitoring tributary area, three diurnal curves were developed to represent daily flow, weekday flow, and weekend flow. These diurnal patterns were initially developed using the flow monitoring data and were adjusted as part of the calibration process until the model-simulated flows closely matched the field-measured flows. Figure 4.4 shows the calibrated weekday and weekend diurnal patterns for the area tributary to Site 6-8. Similar diurnal curves were developed for each meter and its tributary area. These additional curves are available in Appendix D. • Adjust model variables to match field-measured velocity and flow depths. After the model-simulated flows satisfactorily matched the field-measured flows, the model- simulated velocity and flow depth were compared to the field-measured velocity and flow depth. Adjustments were then made to various model parameters until the modeled and measured velocity and depth closely matched each other. For this process, the primary varied parameters were pipeline roughness (Manning’s n) and sediment buildup in the pipe, although other parameters can also be adjusted as calibration results are generated. Manning’s roughness coefficients, or n values, have industry-accepted ranges based on a number of variables. Roughness coefficients increase over time depending on the construction methods, installation quality, system maintenance, and other environmental factors. Additionally, certain factors within the City’s collection system can result in roughness coefficients that differ from the typical range. For example, pipeline bellies, joint misalignment, cracks, and debris root intrusion) lead to increased turbulence in a pipe, which in turn increases the apparent Manning’s n factor. If the model is unable to reasonably match the field-measured flow depth and velocity without leaving the acceptable range of Manning’s roughness coefficients, further investigation is conducted to determine the cause of the discrepancy. Causes of the discrepancy can include errors in a pipe’s slope or diameter, blockages, pipeline sags, and, in some cases, influences from lift station operations. Table 4.4 provides a summary of the dry weather flow calibration using the average and daily peak flow results for both weekday and weekend conditions. Table 4.4 shows that, with the exception of Site 6-1, the model simulated average and peak flows for both weekday and weekend DWF within 10 percent. ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-18 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Table 4.4 Dry Weather Flow Calibration Summary Wastewater Collection System Master Plan City of Modesto, California Weekday Weekend Overall ADWF Measured Data(1) Modeled Data(2) Percent Error(3) Measured Data(1) Modeled Data(2) Percent Error(3) Pipe Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Percent Error Meter Diameter Flow Velocity Level Flow Velocity Level Flow Velocity Level Flow Velocity Level Flow Velocity Level Flow Velocity Level Measured Modeled Number (in) (mgd) (ft/s) (in) (mgd) (ft/s) (in) (mgd) (ft/s) (in) (mgd) (ft/s) (in) (mgd) (mgd) SITE 1-1 60 5.31 1.25 24.5 5.310 1.43 23.0 0.0% 14.9% -6.3% 5.43 1.26 24.6 5.37 1.43 23.1 -1.2% 13.5% -6.3% 5.35 5.33 -0.4% SITE 1-2 48 4.13 1.92 14.7 4.068 1.97 14.2 -1.6% 3.1% -3.4% 4.39 1.96 15.0 4.28 2.00 14.5 -2.5% 2.1% -3.2% 4.21 4.13 -1.9% SITE 1-3 39 1.24 1.10 10.1 1.243 1.16 9.8 0.0% 5.6% -3.2% 1.36 1.15 10.3 1.33 1.18 10.0 -2.1% 2.2% -2.2% 1.28 1.27 -0.6% SITE 1-4 30 1.15 1.67 8.2 1.146 1.72 8.1 -0.1% 2.6% -0.9% 1.22 1.70 8.4 1.21 1.73 8.3 -0.3% 2.1% -0.9% 1.17 1.17 -0.2% SITE 1-5 54 5.23 2.02 16.3 5.153 2.18 15.3 -1.4% 7.9% -6.3% 5.25 2.04 16.2 5.11 2.17 15.2 -2.6% 6.3% -5.9% 5.24 5.14 -1.8% SITE 2-1 42.75 3.52 5.88 6.4 3.339 5.89 6.1 -5.2% 0.1% -4.0% 3.51 5.87 6.4 3.37 5.90 6.1 -4.1% 0.5% -3.4% 3.52 3.35 -4.9% SITE 2-2 54 2.66 1.79 13.8 2.704 1.79 13.5 1.8% 0.0% -1.9% 2.62 1.78 13.6 2.70 1.79 13.5 3.4% 0.1% -0.8% 2.64 2.70 2.3% SITE 2-3 24 0.56 1.19 7.9 0.557 1.11 7.3 -0.2% -6.8% -7.6% 0.57 1.21 7.9 0.57 1.12 7.4 -0.5% -7.4% -7.1% 0.56 0.56 -0.3% SITE 2-4 48 1.69 1.40 11.9 1.694 1.43 11.8 0.1% 2.2% -1.6% 1.64 1.37 11.8 1.68 1.42 11.7 2.1% 3.9% -1.1% 1.68 1.69 0.6% SITE 2-5 30 0.72 1.11 9.9 0.711 1.16 10.3 -0.7% 3.7% 4.3% 0.71 1.13 9.7 0.72 1.15 10.3 0.4% 1.5% 6.4% 0.71 0.71 -0.4% SITE 2-6 15 0.13 1.11 3.0 0.127 1.06 3.0 -0.8% -4.7% 2.5% 0.13 1.08 3.0 0.13 1.05 3.0 -0.9% -2.9% 0.8% 0.13 0.13 -0.8% SITE 3-1 27 1.10 2.32 8.0 1.110 2.16 7.5 1.0% -6.8% -6.8% 1.07 2.28 7.9 1.08 2.13 7.4 0.7% -6.6% -7.1% 1.09 1.10 0.9% SITE 4-1 21 0.04 0.39 2.4 0.034 0.42 2.0 -3.0% 7.9% -16.9% 0.03 0.35 2.2 0.02 0.37 1.8 -9.0% 6.8% -20.3% 0.03 0.03 -4.4% SITE 4-2 33 1.16 1.73 7.5 1.179 1.70 7.8 1.6% -1.8% 3.8% 0.99 1.67 6.8 1.08 1.65 7.4 9.5% -0.7% 10.0% 1.11 1.15 3.6% SITE 4-3 15 0.26 0.96 5.4 0.255 1.03 5.0 -0.5% 6.9% -7.5% 0.23 0.91 5.2 0.23 1.01 4.8 0.3% 10.7% -9.2% 0.25 0.25 -0.3% SITE 4-4 10 0.00 0.07 1.4 0.002 0.08 1.3 3.1% 28.1% -1.6% 0.00 0.00 1.1 0.00 0.01 1.1 -2.2% 181.0% -0.3% 0.00 0.00 3.0% SITE 5-1 40.5 7.70 2.91 18.8 8.000 3.90 15.2 3.9% 34.0% -19.4% 7.59 2.91 18.6 7.67 3.83 14.9 1.0% 31.8% -19.9% 7.67 7.91 3.1% SITE 5-2 36 2.03 2.57 9.1 2.034 2.43 9.2 0.3% -5.6% 0.8% 2.03 2.57 9.1 2.03 2.42 9.1 0.2% -6.0% 1.0% 2.03 2.03 0.3% SITE 5-3 27 1.07 1.48 8.7 1.064 1.48 8.2 -0.8% 0.3% -5.7% 1.15 1.57 8.6 1.13 1.51 8.4 -1.3% -4.2% -2.7% 1.09 1.08 -0.9% SITE 5-4 15 0.46 1.67 5.7 0.448 1.83 5.2 -2.9% 9.3% -9.0% 0.45 1.66 5.6 0.43 1.80 5.1 -4.2% 8.5% -9.2% 0.46 0.44 -3.3% SITE 5-5 24 0.61 0.90 9.2 0.595 1.30 6.8 -3.1% 43.9% -25.6% 0.60 0.88 9.2 0.58 1.29 6.8 -2.5% 47.2% -26.3% 0.61 0.59 -2.9% SITE 6-1 48 3.52 7.60 5.7 2.921 4.07 7.7 -17.0% -46.5% 35.3% 3.56 7.60 5.7 2.83 4.03 7.5 -20.6% -47.0% 31.8% 3.53 2.89 -18.1% ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-19 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Table 4.4 Dry Weather Flow Calibration Summary Wastewater Collection System Master Plan City of Modesto, California Weekday Weekend Overall ADWF Measured Data(1) Modeled Data(2) Percent Error(3) Measured Data(1) Modeled Data(2) Percent Error(3) Pipe Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Avg. Percent Error Meter Diameter Flow Velocity Level Flow Velocity Level Flow Velocity Level Flow Velocity Level Flow Velocity Level Flow Velocity Level Measured Modeled Number (in) (mgd) (ft/s) (in) (mgd) (ft/s) (in) (mgd) (ft/s) (in) (mgd) (ft/s) (in) (mgd) (mgd) SITE 6-3 48 1.88 2.64 6.8 1.871 2.46 7.2 -0.3% -7.0% 5.2% 1.39 2.42 5.8 1.40 2.23 6.3 0.8% -7.9% 7.4% 1.74 1.74 0.0% SITE 6-4 45 3.14 1.73 13.4 3.153 1.80 13.0 0.5% 4.0% -3.3% 3.43 1.77 14.0 3.25 1.81 13.1 -5.2% 2.4% -6.0% 3.22 3.18 -1.2% SITE 6-5 36 2.85 3.34 8.5 2.913 3.24 8.8 2.2% -2.9% 3.4% 2.92 3.30 8.7 3.02 3.26 8.9 3.4% -1.0% 3.0% 2.87 2.94 2.6% SITE 6-6 33 1.36 1.87 7.9 1.387 1.85 8.0 2.1% -0.8% 1.9% 1.46 1.91 8.1 1.48 1.88 8.3 1.4% -1.4% 2.2% 1.39 1.41 1.9% SITE 6-7 33 1.22 2.81 5.4 1.231 2.72 5.6 1.3% -3.3% 3.1% 1.29 2.86 5.6 1.30 2.76 5.7 0.6% -3.6% 3.0% 1.24 1.25 1.1% SITE 6-8 30 0.62 1.31 6.1 0.625 1.32 6.1 0.0% 0.3% 0.3% 0.66 1.32 6.2 0.65 1.33 6.1 -1.2% 0.4% -0.6% 0.63 0.63 -0.4% SITE 6-9 30 0.95 1.18 8.8 0.957 1.19 8.8 0.5% 1.0% -0.2% 1.01 1.20 9.0 1.00 1.21 8.9 -0.4% 0.7% -0.6% 0.97 0.97 0.3% SITE 6-10 15 0.31 1.24 5.2 0.310 1.50 5.6 0.0% 21.5% 7.6% 0.32 1.24 5.2 0.32 1.51 5.7 0.2% 21.7% 8.1% 0.31 0.31 0.1% SITE 7-1 60 5.22 3.35 12.0 5.661 2.79 12.9 8.5% -16.6% 7.0% 5.41 3.38 12.2 5.31 2.72 12.5 -1.9% -19.5% 2.4% 5.28 5.56 5.4% SITE 7-B 30 0.19 1.46 2.6 0.193 1.43 2.6 0.0% -1.9% 1.9% 0.15 1.33 2.3 0.15 1.26 2.4 1.8% -4.9% 5.6% 0.18 0.18 0.5% SITE 8-1 24 0.84 1.79 6.6 0.829 1.74 6.7 -1.3% -2.5% 1.5% 0.75 1.68 6.3 0.75 1.68 6.3 0.1% 0.0% 0.5% 0.81 0.81 -0.9% SITE 9-1 30 0.29 0.66 6.0 0.297 0.94 4.9 2.3% 42.7% -19.3% 0.25 0.63 5.6 0.26 0.90 4.6 1.9% 41.9% -19.0% 0.28 0.29 2.2% SITE 10-1 33 1.42 8.01 3.3 1.390 8.81 3.1 -1.7% 10.0% -7.5% 1.40 8.00 3.3 1.37 8.75 3.1 -2.1% 9.4% -7.4% 1.41 1.38 -1.9% SITE A 21 0.51 1.01 7.9 0.503 1.10 7.4 -2.1% 9.2% -6.5% 0.54 1.04 8.1 0.53 1.12 7.6 -2.3% 8.1% -6.1% 0.52 0.51 -2.2% SITE B 16 0.24 0.84 5.7 0.249 0.91 5.5 3.1% 8.2% -3.1% 0.23 0.84 5.5 0.24 0.89 5.4 3.1% 6.2% -2.0% 0.24 0.25 3.1% SITE C 15 0.06 0.70 3.1 0.064 0.72 3.1 -0.4% 2.2% 1.2% 0.06 0.69 3.1 0.06 0.71 3.1 -1.4% 3.9% 0.2% 0.06 0.06 -0.7% SITE D 60 10.17 1.22 37.8 10.522 1.23 37.5 3.5% 0.8% -0.8% 9.73 1.19 36.9 9.97 1.19 36.7 2.5% 0.2% -0.7% 10.04 10.36 3.2% SITE E 21 0.13 0.59 4.2 0.134 0.64 3.9 -0.5% 8.4% -9.1% 0.12 0.59 4.0 0.12 0.62 3.7 -0.7% 5.3% -7.1% 0.13 0.13 -0.5% Notes: Source: City of Modesto 2014 Temporary Flow Monitoring Program, V&A Consulting Engineers Average flows are calculated from flow monitoring data. Maximum flow values are hourly peaks. Percent Difference = (Modeled - Measured)/Measured*100. ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-20 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Appendix D contains a detailed dry weather flow calibration summary sheet for each of the 41 dry weather metering sites. Each calibration sheet provides plots that compare the model-simulated and field-measured flow, velocity, and level data for both weekday and weekend conditions. An example of the dry weather calibration for Site 6-8 is shown in Figure 4.4. As shown in Figure 4.5 and in Appendix D, the field-measured data correlates exceptionally well with the results of the model output. Although some sites had modeled levels or velocities outside the generally accepted calibration tolerances, the majority of these sites were only marginally outside the acceptable tolerances. Therefore, the model was considered calibrated. 4.5.3 Wet Weather Flow Calibration The WWF calibration enables the hydraulic model to accurately simulate I/I entering the collection system during a large storm. The list below outlines each part of the WWF calibration process. • Identify calibration rainfall events. The WWF calibration process entails running model simulations of historic rainfall events based on data collected from the temporary flow monitoring program. The goal of any wet weather flow monitoring program is to capture and characterize a system’s response to a significant rainfall event, preferably during wet antecedent moisture conditions. The selection of a particular calibration storm or group of storms is based on a review of flow and rainfall data. In this case, the model was run from December 11, 2014, to December 17, 2014, and was calibrated to the main rainfall event that occurred during the flow monitoring period. To run a model simulation for December 11, 2014, to December 17, 2014, the hourly rainfall data were input into the model for these events. Each flow monitoring tributary area, or basin, was assigned a specific rainfall hyetograph, which was calculated for each basin using the rainfall data collected from the permanent rain gauge station. Refer to Chapter 3 and Appendix C for more detail on how this computation was performed. • Define RDII tributary areas. For the WWF calibration, RDII flows are superimposed onto the DWF. To do this, the model calculates RDII by assigning “RDII Inflows” to each node in the model. RDII inflows consist of both a unit hydrograph and the total tributary area to the model node. Each RDII tributary area is then calculated in GIS using the loading polygons, excluding any large, vacant, or open space and other areas in the system that are not expected to contribute to I/I entering the collection system. These tributary areas provide a means to transform hourly rainfall depth from the rainfall hyetographs into a rainfall volume, which is transformed into actual RDII flows using the unit hydrograph. This process is described in the next step. ---PAGE BREAK--- ---PAGE BREAK--- 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Hourly Multiplier Hour Weekday Diurnal Weekend Diurnal EXAMPLE DIURNAL PATTERNS (SITE 6-8) FIGURE 4.4 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- ---PAGE BREAK--- 0 24 48 72 96 120 144 0.0 0.5 1.0 1.5 Flow (mgd) Days Flow Calibration Modeled Flow Measured Flow 0 24 48 72 96 120 144 0.0 0.5 1.0 1.5 2.0 Velocity (ft/s) Days Velocity Calibration Modeled Velocity Measured Velocity 0 24 48 72 96 120 144 0 2 4 6 8 10 Level (in) Days Level Calibration Modeled Level Measured Level EXAMPLE DRY WEATHER FLOW CALIBRATION (SITE 6-8) FIGURE 4.5 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-23 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc • Refine subcatchment parameters. The storm drainage connections to the sewer system were modeled by creating stormwater subcatchments that simulate surface water runoff to the sewer system. During model calibration, a number of parameters were input and refined for each subcatchment, including the area, percent impervious, width, slope, and roughness. These parameters were refined during model calibration to match the flow monitoring data for the downtown area, where the majority of wet weather flow comes from storm drain cross connections. • Create an I/I parameter database and modify it to match field-measured flows. The main step in the WWF calibration process involves creating custom unit hydrographs for each flow monitoring tributary area using the “RTK Method,” which is widely used in collection system master planning. In the RTK Method, the RDII unit hydrograph is the summation of three separate triangular hydrographs (short term, medium term, and long term). Each of these is defined by three parameters: R, T, and K. For the parameters, R represents the fraction of rainfall over the sewershed that enters the collection system; T represents the hydrograph’s time to peak; and K represents the ratio of time to recession to time to peak. In total, nine separate variables are associated with each unit hydrograph. Figure 4.6 shows the shape of a sample unit hydrograph. To simulate I/I, the hydrographs utilized the R-Values (percent of rainfall that enters the collection system) calculated for each basin. The nine variables in each unit hydrograph were initially established based on engineering judgment and then adjusted until the model-simulated flows (both peak flows and average flows) matched closely with the field-measured flows. As with dry weather calibration, the wet weather calibration process compared the meter data with the model output. Comparisons were made for average and peak flows as well as the temporal distribution of flow until flows returned to their baseline levels. According to the WaPUG, a hydraulic model is generally considered satisfactorily calibrated to WWF conditions if the modeled peak flows are within +25 percent to -15 percent of the field-measured data, and if the average modeled flows are within +20 percent to -10 percent of the field-measured data. • Refine model variables to match field-measured velocity and flow depths. After the model was deemed satisfactorily calibrated for wet weather flows, its simulated velocities and flow depths were checked against the field-measured velocities and flow depths during the calibration storms. Refinements were also made to the various model parameters so the modeled and measured velocity and depth closely matched each other. If any adjustments were made to Manning’s n values or other parameters, the DWF calibration was rechecked to ensure that the flow depth and velocities still matched properly under DWF conditions. ---PAGE BREAK--- ---PAGE BREAK--- R I R I R I Total RDII Hydrograph Short Term Hydrograph Medium Term Hydrograph Long Term Hydrograph T T K T T K T T K 1 1 1 1 2 2 2 2 3 3 3 3 EXAMPLE RDII HYDROGRAPH FIGURE 4.6 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-25 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Appendix E contains a detailed wet weather flow calibration summary sheet for each of the 39 wet weather meter sites. Each calibration sheet provides plots that compare the model- simulated and field-measured flow, velocity, and level data for the calibration storms. An example of the wet weather calibration for Site 6-8 is shown in Figure 4.7. Table 4.5 provides a summary of the wet weather flow calibration using the average and peak flow results. Table 4.5 shows excellent overall correlation between the field-measured data and the model output results. However, in some sites, the modeled flows, levels, or velocities were outside the generally accepted calibration tolerances. These sites were further investigated and deemed acceptable. The model was then considered calibrated and ready to use for capacity analysis. ---PAGE BREAK--- ---PAGE BREAK--- 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 12/11 12/12 12/13 12/14 12/15 12/16 12/17 Rain (inches/15-minutes) Flow (mgd) Flow Calibration Rain ADWF Measured Data Modeled Data 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 12/11 12/12 12/13 12/14 12/15 12/16 12/17 Rain (inches/15-minutes) Velocity (ft/s) Velocity Calibration Rain Measured Data Modeled Data 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0 1 2 3 4 5 6 7 8 9 10 12/11 12/12 12/13 12/14 12/15 12/16 12/17 Rain (inches/15-minutes) Level (inches) Level Calibration Rain Measured Data Modeled Data EXAMPLE WET WEATHER FLOW CALIBRATION (SITE 6-8) FIGURE 4.7 CITY OF MODESTO WASTEWATER COLLECTION SYSTEM MASTER PLAN ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-27 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Table 4.5 Wet Weather Flow Calibration Wastewater Collection System Master Plan City of Modesto, California Storm 1 (12/11/2014-12/14/2014) Storm 2 (12/15/2014-12/17/2014) Measured Data(1) Modeled Data(2) Percent Error(3) Measured Data(1) Modeled Data(2) Percent Error(3) Pipe Avg. Peak Avg. Avg. Avg. Peak Avg. Avg. Avg. Peak Avg. Avg. Avg. Peak Avg. Avg. Avg. Peak Avg. Avg. Avg. Peak Avg. Avg. Meter Diameter Flow Flow Velocity Level Flow Flow Velocity Level Flow Flow Velocity Level Flow Flow Velocity Level Flow Flow Velocity Level Flow Flow Velocity Level Number (in) (mgd) (mgd) (ft/s) (in) (mgd) (mgd) (ft/s) (in) (mgd) (mgd) (ft/s) (in) (mgd) (mgd) (ft/s) (in) SITE 1-1 58 7.431 15.157 1.42 28.8 6.728 15.683 1.52 27.2 -9.5% 3.5% 7.0% -5.4% 6.238 8.907 1.33 26.6 6.282 10.040 1.60 24.2 0.7% 12.7% 20.0% -8.8% SITE 1-2 48 5.857 11.512 2.09 17.6 5.322 12.092 2.11 16.2 -9.1% 5.0% 0.8% -8.0% 5.008 7.105 2.04 16.2 4.831 7.804 2.07 15.6 -3.5% 9.8% 1.7% -3.9% SITE 1-3 39 1.713 3.486 1.31 11.1 1.659 3.607 1.25 11.2 -3.1% 3.5% -4.7% 0.7% 1.514 2.342 1.29 10.4 1.473 2.214 1.22 10.6 -2.7% -5.5% -5.6% 2.7% SITE 1-4 28 1.719 5.234 1.93 9.6 1.699 4.663 1.87 9.9 -1.2% -10.9% -2.9% 3.4% 1.500 2.799 1.88 9.0 1.511 3.034 1.84 9.4 0.7% 8.4% -2.2% 4.9% SITE 1-5 54 6.173 14.005 2.24 15.7 6.446 15.172 2.20 17.6 4.4% 8.3% -1.9% 11.9% 5.837 9.789 2.31 15.9 6.077 9.582 2.17 17.3 4.1% -2.1% -6.0% 8.9% SITE 2-1 42.75 4.645 7.219 6.55 7.1 4.536 8.135 6.38 7.0 -2.3% 12.7% -2.5% -0.6% 4.337 5.924 6.16 7.1 4.201 6.983 6.29 6.8 -3.1% 17.9% 2.0% -3.5% SITE 2-2 31.5 3.830 10.063 1.66 20.9 3.694 10.189 1.71 19.1 -3.6% 1.3% 3.5% -8.5% 3.348 6.322 1.60 17.8 3.262 6.408 1.77 15.4 -2.6% 1.4% 10.6% -13.5% SITE 2-3 18.5 0.783 1.604 1.24 12.5 0.677 1.364 1.07 12.5 -13.5% -15.0% -14.0% 0.4% 0.791 1.228 1.31 9.0 0.626 0.957 1.09 9.6 -20.9% -22.0% -17.0% 6.3% SITE 2-4 30 2.467 7.519 1.49 18.2 2.522 8.388 1.55 17.2 2.2% 11.6% 4.2% -5.4% 2.209 4.811 1.53 13.5 2.146 4.993 1.53 13.2 -2.8% 3.8% 0.0% -2.0% SITE 2-5 21 0.952 2.290 1.14 15.5 0.877 2.316 1.53 13.4 -7.9% 1.1% 34.1% -13.5% 0.907 1.724 1.22 9.9 0.804 1.276 1.58 10.0 -11.3% -26.0% 29.8% 0.6% SITE 2-6 15 0.108 0.388 0.85 3.1 0.130 0.323 1.19 2.8 20.1% -16.8% 40.0% -10.7% 0.121 0.337 0.96 3.1 0.127 0.225 1.19 2.8 5.6% -33.3% 24.8% -10.4% SITE 3-1 18 1.538 3.460 2.57 9.2 1.520 3.492 2.40 8.9 -1.2% 0.9% -6.6% -3.4% 1.453 2.588 2.57 8.8 1.437 2.379 2.39 8.6 -1.1% -8.1% -7.2% -2.2% SITE 4-2 33 1.561 5.257 1.64 9.1 1.615 5.463 1.81 8.8 3.5% 3.9% 10.3% -3.4% 1.439 3.119 1.69 8.8 1.592 3.920 1.83 8.9 10.6% 25.7% 8.4% 1.1% SITE 4-3 15 0.464 2.134 1.55 5.7 0.444 2.032 1.53 5.6 -4.4% -4.8% -1.2% -0.8% 0.401 1.285 1.56 5.2 0.398 1.388 1.56 5.1 -0.7% 8.0% -0.1% -1.4% SITE 4-4 10 0.005 0.055 0.11 1.8 0.003 0.090 0.06 1.2 -38.7% 64.7% -47.1% -30.7% 0.005 0.048 0.11 1.8 0.003 0.010 0.09 1.3 -45.0% -79.1% -21.1% -27.2% SITE 5-1 41.5 9.150 26.615 3.85 20.9 10.461 27.549 3.95 18.2 14.3% 3.5% 2.7% -13.0% 7.129 13.721 3.55 14.9 9.807 17.117 4.02 15.7 37.6% 24.8% 13.2% 5.3% SITE 5-2 28 2.589 5.613 2.64 10.6 2.542 5.758 2.51 10.4 -1.8% 2.6% -4.8% -2.5% 2.379 3.882 2.68 9.9 2.394 3.792 2.49 10.1 0.7% -2.3% -7.0% 2.5% SITE 5-3 25.5 1.305 2.726 1.49 10.8 1.306 2.773 1.56 9.0 0.0% 1.7% 4.3% -16.3% 1.245 1.919 1.46 10.7 1.208 1.935 1.53 8.8 -3.0% 0.8% 4.9% -18.1% SITE 5-4 15 0.462 1.183 1.85 5.1 0.491 1.194 1.84 5.4 6.1% 1.0% -0.2% 6.0% 0.456 0.975 1.85 5.1 0.484 0.880 1.84 5.4 6.2% -9.7% -0.6% 6.9% SITE 5-5 21 0.614 1.450 0.97 8.7 0.681 1.367 1.33 7.0 10.9% -5.7% 37.7% -19.0% 0.586 1.108 0.95 8.5 0.661 1.015 1.33 6.9 12.9% -8.4% 39.7% -18.8% SITE 6-1 36 9.084 24.912 2.82 22.0 9.895 26.070 1.92 9.1 8.9% 4.6% -31.9% -58.5% 8.171 13.820 2.82 18.4 9.271 16.449 1.87 8.0 13.5% 19.0% -33.5% -56.3% SITE 6-3 48 1.844 3.910 2.12 7.7 1.849 3.818 2.33 7.2 0.3% -2.4% 9.7% -5.9% 1.885 3.383 2.19 7.8 2.027 2.963 2.42 7.6 7.5% -12.4% 10.2% -1.5% SITE 6-4 45 3.763 9.369 2.14 12.7 4.044 10.092 1.91 14.7 7.5% 7.7% -10.9% 15.7% 3.401 6.315 2.11 12.1 3.664 6.630 1.88 14.1 7.7% 5.0% -10.9% 16.5% SITE 6-5 36 3.589 9.016 3.59 9.4 3.775 10.160 3.47 10.0 5.2% 12.7% -3.2% 6.1% 3.154 5.946 3.51 8.8 3.419 6.418 3.40 9.6 8.4% 7.9% -3.1% 8.9% SITE 6-6 33 1.714 4.438 2.09 8.5 1.725 3.990 1.95 8.9 0.6% -10.1% -6.9% 5.6% 1.546 3.241 2.10 8.0 1.580 2.811 1.92 8.6 2.3% -13.3% -8.5% 8.2% SITE 6-7 33 1.401 2.927 3.02 5.6 1.441 3.190 2.99 5.8 2.9% 9.0% -0.9% 3.3% 1.226 1.993 2.94 5.3 1.348 2.077 2.96 5.7 10.0% 4.2% 0.6% 7.0% SITE 6-8 30 0.670 1.465 1.42 5.9 0.721 1.431 1.36 6.5 7.6% -2.3% -4.1% 10.0% 0.632 1.131 1.44 5.7 0.681 0.971 1.34 6.4 7.7% -14.1% -6.4% 11.9% ---PAGE BREAK--- ---PAGE BREAK--- April 2016 - FINAL DRAFT 4-28 pw://Carollo/Documents/Client/CA/Modesto/9704A00 - WW Collection/Deliverables/CH04/Draft Final - Ch04 CS.doc Table 4.5 Wet Weather Flow Calibration Wastewater Collection System Master Plan City of Modesto, California Storm 1 (12/11/2014-12/14/2014) Storm 2 (12/15/2014-12/17/2014) Measured Data(1) Modeled Data(2) Percent Error(3) Measured Data(1) Modeled Data(2) Percent Error(3) Pipe Avg. Peak Avg. Avg. Avg. Peak Avg. Avg. Avg. Peak Avg. Avg. Avg. Peak Avg. Avg. Avg. Peak Avg. Avg. Avg. Peak Avg. Avg. Meter Diameter Flow Flow Velocity Level Flow Flow Velocity Level Flow Flow Velocity Level Flow Flow Velocity Level Flow Flow Velocity Level Flow Flow Velocity Level Number (in) (mgd) (mgd) (ft/s) (in) (mgd) (mgd) (ft/s) (in) (mgd) (mgd) (ft/s) (in) (mgd) (mgd) (ft/s) (in) SITE 6-9 30 0.992 1.996 1.32 8.3 1.075 2.095 1.22 9.4 8.4% 5.0% -7.3% 12.7% 0.896 1.367 1.26 8.0 1.026 1.513 1.21 9.2 14.5% 10.7% -4.5% 14.5% SITE 6-10 15 0.335 0.707 1.41 7.2 0.351 0.669 1.54 6.5 4.9% -5.4% 8.7% -10.1% 0.317 0.464 1.42 6.0 0.335 0.496 1.53 6.0 5.8% 6.9% 7.3% 0.4% SITE 7-1 45 6.874 19.711 2.57 15.3 7.210 19.861 2.81 14.8 4.9% 0.8% 9.1% -3.6% 6.216 11.103 2.60 14.4 6.775 12.410 2.80 14.6 9.0% 11.8% 7.6% 1.2% SITE 8-1 24 1.043 2.998 1.79 8.3 0.975 2.945 1.77 7.2 -6.5% -1.8% -1.0% -12.8% 1.111 2.091 1.96 7.4 0.938 1.821 1.78 7.2 -15.5% -12.9% -9.2% -3.6% SITE 9-1 30 0.280 0.992 0.86 4.5 0.274 0.970 0.88 4.0 -2.1% -2.2% 2.6% -10.5% 0.254 0.594 0.84 4.4 0.266 0.604 0.88 4.1 4.4% 1.8% 4.5% -6.7% SITE 10-1 24 0.393 1.086 6.19 1.6 0.359 0.991 5.78 1.6 -8.6% -8.8% -6.8% 2.4% 0.370 0.725 6.16 1.5 0.344 0.607 5.77 1.6 -7.1% -16.2% -6.4% 3.6% SITE A 18 0.689 1.795 1.25 8.3 0.661 1.672 1.17 8.6 -4.2% -6.8% -6.2% 3.6% 0.615 1.121 1.21 7.9 0.588 1.072 1.14 8.2 -4.4% -4.4% -6.1% 3.4% SITE B 16 0.535 1.577 1.66 7.5 0.461 1.723 1.40 7.3 -13.9% 9.3% -15.7% -2.3% 0.514 1.577 1.76 5.6 0.368 1.169 1.38 6.3 -28.4% -25.8% -21.7% 13.2% SITE C 15 0.038 0.156 0.50 3.6 0.047 0.132 0.68 4.9 24.9% -15.3% 35.9% 35.7% 0.037 0.087 0.54 2.5 0.046 0.082 0.66 4.0 24.5% -6.1% 22.9% 61.7% SITE F 18 1.202 2.821 2.45 8.8 1.110 2.813 1.85 8.4 -7.7% -0.3% -24.5% -5.5% 1.123 2.210 2.56 7.3 1.037 2.019 1.92 7.4 -7.7% -8.6% -25.3% 1.2% Notes: Source: City of Modesto 2014 Temporary Flow Monitoring Program, V&A Consulting Engineers Average flows are calculated from flow monitoring data. Maximum flow values are hourly peaks. Averages were adjusted to account for data not recorded. Percent Difference = (Modeled - Measured)/Measured*100. ---PAGE BREAK---