2018 Sewer Collection Master Plan Update

Transcription

1 2018 Sewer Collection Master Plan Update June 2015 Prepared For: Logan City Corporation. 255 N Main Street Logan, UT Prepared By: 1047 South 100 West, Suite 180 Logan, UT 84321

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3 CONTENTS EXECUTIVE SUMMARY... viii 1 INTRODUCTION Background Project Tasks Master Plan Purpose DATA COLLECTION Introduction Existing System Mapping System Connectivity Sewer Cleanouts Lift Station Information Reverse Grade Pipes Flow Routing Adjustments Drop manholes Pipe Diameter Adjustments Sanitary Sewer Flows Total Flows Infiltration Inflow Summer Flow Data Collection Summer Meter Schedule Summer Meter Equipment Summer Meter Locations Summer Flow Data Evaluation EXISTING SYSTEM ANALYSIS Introduction Collection System Regulatory Requirements Development Requirements Logan City Page iii

4 3.4 Model Development and Assumptions Collection System Geometry Assumptions Flow Input Location Assumptions Sanitary Flow Assumptions Pump Parameter Assumptions Diurnal Curves Assumptions Infiltration Assumptions Inflow Flows from Others and Large Water Users Cost Estimating Assumptions Model Calibration Existing System Evaluation Depth of Flow over Diameter of Pipe (d/d) Reserve Capacity Hydraulic Grade Line Profile Evaluation Condition Analysis Lift Station Analysis Existing System Improvements Capacity Improvements Condition Improvements Lift Station Improvements Summary of Existing Improvements MASTER PLAN & RELIEF ALTERNATIVES Introduction Key Assumptions for Future Models Creation of Future Models Future Lift Station Placement Future Flow Generation Evaluation and Results Evaluation and Results Logan City Page iv

5 4.6 Buildout Evaluation and Results PRIORITIZED CAPITAL IMPROVEMENT PROJECTS (CIP) CONCLUSIONS AND RECOMMENDATIONS REFERENCES TABLES Table 1-1: Logan City Growth Table... 2 Table 1-2: Time Frames Analyzed... 3 Table 2-1: Reverse Grade Slope Summary Table, S < Table 2-2: Temporary Flow Meters Table 3-1: Diurnal Curve Assignments Table 3-2: Infiltration Rates Table 3-3: Existing System Capacity Improvements Table 3-4: Existing System Condition Improvements Table 4-1: Future Time Frames Analyzed Table 4-2: Future Pipe Design Parameters Table 4-3: 2020 Capacity Improvements Table 4-4: 2025 Capacity Improvements Table 4-5: Build Out Capacity Improvements Table 5-1: Existing System CIP Summary Table 5-2: Future System CIP Summary GRAPHS Graph 2-1: Wintertime Sewer Flows Graph 2-2: Summertime Sewer Flows Graph 2-3: Summertime Sewer Flows and Precipitation Graph 3-1: Diurnal Curves Graph 3-2: Example Calibration Flow Graph Logan City Page v

6 DIAGRAMS Diagram 3-1: Pipe Flow Less than Half Full Diagram 3-2: Negative Reserve Capacity Illustration APPENDICES APPENDIX A REPORT FIGURES (Large maps bound separate from this report) Figure 1 - Existing Collection System Figure 2 - Flow Meter Locations Figure 3 - Diurnal Curve Pattern Assignments Figure 4 - Infiltration Rates Figure 5 - Existing Depth over Diameter Figure 6 - Existing Reserve Capacity Figure 7 - Existing Peak Velocities Figure 8 - Existing System Improvements Figure 9 - Projected Growth Figure Depth over Diameter Figure Reserve Capacity Figure Improvements Figure Depth over Diameter Figure Reserve Capacity Figure Improvements Figure 16 - Build Out Depth over Diameter Figure 17 - Build Out Reserve Capacity Figure 18 - Build Out Improvements Figure 19 - Build Out System APPENDIX B TEMPORARY FLOW METER GRAPHS Flow versus Time Graphs Depth and Velocity versus Time Graphs Velocity versus Level Scatter Plots APPENDIX C TEMPORARY FLOW METER SITE NOTES Logan City Page vi

7 APPENDIX D GRAPHS OF FLOWS FROM CONTRIBUTING CITIES APPENDIX E UNIT PRICE COSTS SUMMARY TABLE APPENDIX F MODEL CALIBRATION GRAPHS APPENDIX G CALIBRATION NOTES TABLE APPENDIX H BUILD OUT LOCATIONS TO MONITOR APPENDIX I SYSTEM IMPROVEMENT DIAGRAMS APPENDIX J PROJECTED POPULATIONS OF CONTRIBUTING COMMUNITIES APPENDIX K COMPUTER MODEL UPDATE PROCEDURE Logan City Page vii

8 EXECUTIVE SUMMARY Background Logan City hired J-U-B Engineers Inc. (J-U-B) to complete a sewer collection system master plan. The main purpose of the master plan is to provide a planning document and tools that help Logan City meet its existing and future sewer collection needs. The primary tool is a computer hydraulic sewer model that is built based on Geographic Information System (GIS) data provided by the City. Avoiding the overloading of existing sewer pipes from new development or re-development is of major importance. Re-development can significantly change peak flows in collection pipes near the redeveloped area. The sewer model created for this plan is detailed enough to allow each proposed development or re-development to be evaluated to verify its potential impact on the system. Every mapped pipe (with the exception of some dead end pipes that do not have manholes at the upstream end) is modeled to allow for capacity checks of the pipes in these types of situations. Master Plan Goals Create a detailed calibrated model that is efficient to operate and update Identify existing system capacity and condition deficiencies Identify future system deficiencies Master plan a conceptual collection system to serve undeveloped areas Provide a prioritized list of capital improvement projects needed now and for years 2020, 2025, and build out This master plan combined with the Logan City 2015 Sewer System Management Plan (SSMP) complies with the requirements of the Utah Division of Water Quality s Utah Sewer Management Program (USMP) including the System Evaluation and Capacity Assurance Plan (SECAP) requirements. The program is authorized under State of Utah Administrative Code R Conclusions and Recommendations Existing System Geometry - There are some pipe invert elevations and other system geometry data that still need to be updated. Update the City GIS data to include some new manhole inverts that were added as noted in the model. In the future, the GIS data will always be the parent data and the model will be updated based on the latest GIS data. Continue to identify and update corrections for the system GIS files and then update the model. System Infiltration - The total approximate base flow recorded at the treatment lagoons during winter months is approximately 3,750 gallons per minute (GPM) based on the flows recorded during the very early morning hours of winter days. The base flow during the summer is approximately 7,750 GPM. It is probable that a large portion of the base flow comes from groundwater infiltration with some flow Logan City Page viii

9 being sanitary flow produced mainly by industrial users that operate during early morning hours. A very large portion of the infiltration comes from the island area. Implement more flow monitoring in the island area during the summer months to identify more specific sources of infiltration. This will lead to more effective efforts to reduce the infiltration. Implement infiltration reduction methods, such as sealing open pipe joints. An ongoing fund needs to be included in the budget to implement this maintenance program. This program will result in sewer treatment savings if I&I is successfully reduced. System Inflow - Small amounts of inflow were observed as a result of some small rain events recorded while gathering flow data for this master plan. Infiltration is a much larger flow contributor to the system then inflow from small rain events. Collect flow data during large rain events for an accurate evaluation of the impacts of inflow on the system. Existing Pipes Near Capacity - Some existing pipes appear to be approaching capacity in the model (See Figures 5 and 6). As development occurs, the existing d/d and reserve capacity figures should be referenced to determine where areas of concern may be. The model should also be updated to reflect new flow conditions as new routing or new development happens. Existing Poor Condition Areas - Some pipes in the existing system are known to be problem areas or pipes that are deteriorated (See Figure 8). These pipes are listed in the report in Table 3-3 with the estimated replacement costs. Repair or replace the listed pipes. The condition of the existing pipe located in 400 North from 700 East to Main Street is of particular concern and should be repaired/replaced as soon as possible. Existing Over Capacity Areas - Some small isolated pipes in the existing system are over capacity at peak flow times (See Figure 8). Design and build the improvements listed in Table 3-4 of the report to add additional capacity as soon as possible. The improvements are listed in order of priority. Existing Lift Stations New pumps will be needed at the existing lift station at the airport in the next few years. Improvements are currently being made to the Providence lift station by city staff. New pumps will need to be added to the West Regional Lift Station in the year Install two pumps at the Airport lift station. Continue to monitor the existing lift stations and upgrade as needed. Plan to add two new pumps to the West Regional Lift Station in the year Logan City Page ix

10 Future Areas Near Capacity - Some additional pipes appear to be approaching capacity in the model at the Build Out time frame (See table in Appendix H). Continue to maintain and update the model in order to manage future capacity issues. Future Over Capacity Areas - There are some areas in the existing system that will exceed capacity in the future based on the assumed growth projections. Begin plans now to build the 2020 improvements as listed in Table 4-3 of the report. Future Trunk Lines and Lift Station Upgrades - Many new trunk lines and lift stations will be needed to serve the areas that will develop in the city in the future. Size pipes and lift stations based on the conceptual future system plan prepared for this report (See Figure 19). Computer Model - The computer model is very detailed and can be used to identify impacts from new developments. Utilize the existing model to determine impacts from proposed new developments or areas that plan to re-develop to higher densities. Update the existing model regularly by importing updated system information from the GIS databases that are maintained by the Logan GIS department. Logan City Page x

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12 1 INTRODUCTION 1.1 BACKGROUND The Logan City sanitary sewer system collects sewer flows from Logan City and other surrounding communities and transports those flows to the Logan wastewater treatment facility located near 600 North 1900 West in Logan, Utah. There are approximately 895,000 lineal feet of pressure and gravity sewer pipe in the collection system ranging from 4-inch diameter to 60-inch diameter. The majority of the collection pipes are 8-inch diameter totaling approximately 589,000 feet in length. Logan has grown significantly over the last few decades as shown in Table 1-1 (United States Census Bureau, n.d.) (Utah Governor's Office of Planning and Budget, 2013). Table 1-1: Logan City Growth Table Logan City Growth Year Population Average Annual Growth Rate , % , % ,174 Logan continues to see growth around its outer edges and growth from re-development in its center as areas re-develop to higher densities. The collections system serves six surrounding cities that will also continue to grow. The following cities are connected to the collection system: Smithfield Hyde Park North Logan River Heights Providence Logan City Page 2

13 Nibley The trunk lines in the collection system that serve these cities need to be large enough to continue to convey the flows that will come with the future growth. The City hired (J-U-B) to evaluate the capacity of the existing collection system, and propose system improvements to accommodate projected growth. There are four time-frames analyzed in this plan as listed in Table 1-2 below. Table 1-2: Time Frames Analyzed Time Frames Analyzed Title Description 2014 Existing flows during summer irrigation months when infiltration is high 2020 Projected 2020 flows during summer irrigation months 2025 Projected 2025 flows during summer irrigation months Build Out Projected flows during the summer irrigation months at build out. Build out is defined as the condition when all of the areas in the future boundaries of the City develop to the planned densities as identified in the 2015 Water Master Plan and the contributing cities reach their projected 2060 populations as estimated by the Governor's Office of Planning and Budget (GOPB). The goals of the master plan are: Create a detailed model that is efficient to operate and update Identify existing system capacity and condition deficiencies Identify future system deficiencies Master plan a collection system to serve Logan at build out Provide a prioritized list of capital improvement projects needed for 2020, 2025, and build out Train City staff to operate and update the model A master plan is an essential element for any community experiencing growth. With a master plan, a community has a tool to guide infrastructure improvements. This master plan provides direction to Logan City Page 3

14 continue providing adequate sewer collection services as new areas develop and existing developed areas re-develop. 1.2 PROJECT TASKS J-U-B performed the following tasks to complete the plan: Gathered system information and flow data from Logan City Mapped the existing collection system utilizing data provided by Logan City Added sanitary flows to the collection system based on winter culinary water meter data as recorded by City water meters Analyzed existing sewer flow meter data provided by the City Performed a preliminary model calibration using existing flow data Recommended temporary flow data collection sites to measure summer flows during high infiltration Collected flow data from 13 simultaneous temporary meter sites during the summer months to record the high infiltration flows Calibrated the model to match the metered flows Met with City staff to identify poor condition locations in the system Identified existing system repairs, capacity deficiencies and areas to monitor Made future flow projections for 2020, 2025 and build out based on input from City Staff Identified system improvement projects needed for 2020, 2025 and build out Master planned a conceptual collection system to serve areas that will develop in the future Prepared prioritized lists of improvement projects and areas to monitor for each of the future time frames analyzed Listed conclusions and recommendations drawn from the master plan study Provided model training for the city staff A central component of these tasks is the use of computer modeling software to simulate current and future sanitary sewer system capacity. The software and planning parameters used for this study are discussed in greater detail in Chapter MASTER PLAN PURPOSE The main purpose of the master plan is to provide a planning document and tools that help Logan City meet its future sewer collection needs. This report serves as the planning document. The main tool is the computer hydraulic sewer model. The model is detailed enough to allow each new development or re-development to be evaluated to verify its potential impact on the collection system. Re-development can significantly change peak flows in collection pipes near the re-developed area. For example, a multistory, multi-family building constructed in the place of a single family home will greatly increase the peak sewer flows that may enter the collection system. The re-development may be connected to an Logan City Page 4

15 existing 8-inch sewer pipe that already is approaching its capacity limits. Every pipe in the system has been modeled to allow for capacity checks of the pipes in these types of situations. Conditions may change and ultimately affect the master plan. The analysis and recommendations contained herein should be updated as necessary. The City should revisit this document and the model prior to engaging in detailed design of any sanitary sewer facilities to verify that the model and conclusions are still valid. The model and plan should be updated and verified with any significant changes to the system. Logan City Page 5

16 2 DATA COLLECTION 2.1 INTRODUCTION A large amount of data was required to build a model of the collection system. Existing system mapping information, existing water use data and sewer flow data were needed. The software used for the mapping was ArcGIS software Version EXISTING SYSTEM MAPPING The existing collection system is shown in Figure 1: Existing Collection System (All of the report figures are included in Appendix A and bound separate from this report). The information needed to create the existing system figure was obtained from the City GIS department. The following items are included in the mapping: Aerial image of the City Existing gravity sewer lines Existing private and City owned lift stations and associated pressure force mains Existing Logan City limits Points of connection from other cities Street labels J-U-B met multiple times with City staff during the system mapping process to review the sewer collection data and make adjustments as needed. Through this process, some updates were made to the existing system for the model as described in the following sub-sections. The City GIS data needs to be updated to include some new manhole inverts that were integrated and noted in the existing sewer system model. In the future, the GIS data will always be the parent data and the model will be updated based on the latest GIS data System Connectivity The system connectivity had to be created to allow the model flows to be conveyed through the system. All of the manholes in the system needed elevations in order to complete the connectivity. The following steps were followed to create the system connectivity: Identified the manholes that were missing elevations Met with the GIS department to review the missing elevations Developed a plan with the GIS department to receive the updated data Entered the new invert elevations to the model Interpolated some elevations that did not come with the updated GIS data Added notes on manholes that we interpolated Logan City Page 6

17 At the meeting, it was discussed that the GIS department may not be able to identify all the inverts and that some of the manholes would need to be interpolated. The City gathered or calculated many more elevations, but there were still a few manholes that needed elevations. These elevations were interpolated where possible using the manholes with elevations. Notes were made in the model to track manholes with elevations that were calculated rather than surveyed. There were also many pipes in the system that were not connected together. These were connected in the model in order for the model to run. J-U-B re-drew the un-connected pipes from the upstream manhole to the downstream manhole and added notes to the pipes that were adjusted Sewer Cleanouts There are many small dead end pipes in the system that are stubbed out for future services or line extensions but not connected to any manholes. J-U-B identified these and added manholes or removed the pipe from the model. J-U-B added notes to all the pipes, manholes and cleanouts to provide an identifier indicating if they were to be used in the model. J-U-B added a cleanout or removed the dead end pipe from model at each dead end location Lift Station Information The City has multiple lift stations (Figure 1) that are needed to convey some of the flows that come from within Logan and some of the flows that come from other cities to the treatment facility. Pump information and wet well geometry information for the lift stations was given to J-U-B in the form of record drawings and entered into the model Reverse Grade Pipes The collection system GIS file from the City has some reverse grade pipes. The following steps were taken to determine if the pipes were truly sloping the wrong direction or if the pipe elevations needed to updated or corrected: J-U-B identified pipes in the system with reverse grades Logan and J-U-B met and decided that pipes with more than 0.4 feet of reverse elevation difference between manholes would be verified by the City and that the city would give updated elevations to J-U-B for the model J-U-B input the corrected and interpolated elevations provided by the City There are still 39 gravity pipes identified in the model with less than 0.4 feet of reverse elevation difference. The model cannot calculate flows for gravity pipes with reverse grades. For the hydraulic calculations, the modeling software assumes that the reverse grade pipes have a downstream invert elevation that is feet lower than the upstream invert elevation. The elevations that are provided in the model inputs are not changed by the model software. These pipe segments are listed in Table 2-1. Logan City Page 7

18 Table 2-1: Reverse Grade Slope Summary Table, S < 0.4 GIS ID UPSTREAM INVERT REVERSE GRADE PIPE SUMMARY DOWNSTREAM INVERT NEAREST INTERSECTION/DESCRIPTION SM S/600 W (Runs in 600 W) SM N/100 E (Runs in 100 E) SM Center St./100 W (Runs in 100 W) SM S/1100 W (Runs in 1100 W) SM Near Country Manor LS SM N/600 W (Runs in 1800 N) SM Rosewood Circle SM S/Riverwood Dr. (Runs in 800 S) SM S/Park Ave. (Runs in 880 S) SM SM Davis Ave./Hillcrest Ave. (Runs parallel to Davis behind homes) Davis Ave./Hillcrest Ave. (Runs parallel to Davis behind homes) SM N Near sewer lagoons SM W Hwy. 89 SM S (Connection between Rosehill Develp. and housing to the east) SM South of Home Depot (Runs parallel to Main St.) SM N 600 E SM Between 1780 S and 1750 S SM Between 400 W and 600 W north of 1600 N SM Between 400 W and 600 W north of 1600 N SM S/500 E SM S/400 E (Runs in 400 E) SM N/400 W (Runs in 400 W) SM S/2000 W (Runs in 200 W) SM Riverwalk Pkwy/Golf Course Rd. (Back of townhomes) SM N Near sewer lagoons SM S/1000 W (North of Codale Elec.) SM N/900 W (Runs along 900 W) SM S/Park Ave. Logan City Page 8

19 GIS ID UPSTREAM INVERT REVERSE GRADE PIPE SUMMARY DOWNSTREAM INVERT NEAREST INTERSECTION/DESCRIPTION SM S/2000 W (Runs in 2000 W) SM S/Park Ave. (Runs in Park Ave.) SM S/1000 W (Runs in 1000 W) SM S/1000 W (Runs in 1000 W) SM N/200 E (Runs in 200 E) SM N/1000 W (Runs in 1000 W) SM N/1000 W SM N/1000 W (Runs in 1000 N) SM N/1000 W (Runs in 1000 W) SM S/Rosewood Cir. (Runs in Rosewood Cir.) SM S/200 E Flow Routing Adjustments There are many manholes in the system that have two or more pipes that exit. The modeling software splits the flows at these manholes based on the elevations of the exiting pipes and based on the flow path of least resistance. The accuracy of the flows in the pipes downstream of the split manholes is dependent on accurate outgoing pipe elevations, pipe sizes and slopes. J-U-B worked with the Logan GIS department to field check as many of these locations as possible and input updated information into the model. The following steps were followed: J-U-B queried the model to find the manholes with more than one pipe exiting J-U-B met with City staff to develop a strategy to gather more invert and flow routing data City staff checked the manholes in the field: o If outgoing inverts were different, they collected survey shots on the inverts and added new invert elevations to the system shape files o If outgoing inverts were the same, they made an estimate of what percent of the incoming flow goes to each of the outgoing pipes o Other notes such as All flows go west until pipe is more than half full, then flows are split 50/50 were made J-U-B imported the new data and checked the flow routing Multiple iterations of this process were followed to update the flow routing in the model. Logan City Page 9

20 2.2.6 Drop manholes There are many drop manholes in the existing collection system. Drop manholes are typically found in steeper areas of the City. They often can be identified in the field by having two inlet pipes (one a few feet directly above the other) on the upstream side of the manhole with the upper inlet being mostly dry or completely dry. The dry pipe is representative of the elevation of the pipe upstream of the manhole as it approaches the manhole. However, at a close distance from the manhole, the upstream pipe has a vertical tee installed with some vertical elbows that drop the incoming flow through a lower pipe to an elevation that is close to the bottom elevation of the manhole it enters. Logan City staff provided drop manhole information that has been recorded by the GIS department. There are still some drop manholes in the actual system that need to be input into the model. Over time the City should continue to identify drop manholes and update the drop manhole information in the system GIS files Pipe Diameter Adjustments J-U-B identified some pipes in the mapped system data with sizes that did not appear to be correct. For example, there were a few trunk lines in the data that had pipes that were smaller than expected based on comparisons with the surrounding pipes. Some of the pipe sizes were updated in the model after verifying the actual sizes out in the field with Logan public works staff. 2.3 SANITARY SEWER FLOWS The sanitary flows are the flows in the system that come directly from homes or businesses. These flows do not include any extra flows that may enter the collection system along the way to the treatment facility in the form of infiltration or inflow (I&I). The sanitary flows were estimated by assuming that the daily sanitary sewer volumes from each sewer connection are equal to the culinary water usage as recorded by individual water meters during the winter months. During the winter, most of the culinary water that is used enters the sewer collection system because no water is being used for outdoor watering. J-U-B obtained water usage data by gathering water meter records from the City s water database for the winter season of J-U-B reviewed this data and selected the highest usage month to use for the model, which was November J-U-B estimated the daily volume at each meter location by taking the total volume recorded for November 2013 and dividing by 30 days. 2.4 TOTAL FLOWS The total flows in the collection system consist of the sanitary flows along with flows that enter the system in the form I&I. Flow data is critical to quantify the effects of I&I on the flows in the system. Logan City Page 10

21 Flow data is most useful for collection system master planning when it represents the highest seasonal flows that pass through the system. This allows for future pipe sizing that is adequate to convey the peak seasonal flows. Based on past meter records at the treatment lagoons, the highest flows during a given year typically occur in the summer time around July and August. The higher flows in the summer are typically made up in large part by increases in infiltration Infiltration Infiltration consists of groundwater that enters the sewer system through open joint pipes, cracks in pipes, faulty service connections, leaky manhole joints and poor seals at the connections between pipes and manholes. Infiltration flows are typically slightly less than the total flow in a collection system during the very early morning hours when most of the people in the city are asleep. Graph 2-1 shows the wintertime flows recorded at the sewer treatment lagoons during the month of November Graph 2-1: Wintertime Sewer Flows The base winter nighttime flows (infiltration) as recorded by the treatment lagoons meter are approximately 3,750 gallons per minute (GPM). In Logan, many irrigation canals pass through the city and carry water during the summer months. With so many canals located close to sewer collection lines, there is potential to have increased groundwater infiltration when the canals are carrying irrigation water. Graph 2-2 shows the summertime sewer flows at the treatment lagoons as recorded during parts of July and August Logan City Page 11

22 Graph 2-2: Summertime Sewer Flows Inflow The base summer nighttime flows recorded at the lagoons are approximately 7,750 GPM. The recorded summer infiltration flows were approximately 4,000 GPM greater (approximately two times greater) than the winter infiltration flows recoded at the treatment lagoons. Inflow is surface storm water that enters into the sewer system during or after a storm event. Inflow enters collection systems through manhole covers and direct connections such as roof drains, foundation drains, and storm sewer connections. One way to estimate the amount of inflow in a system is by comparing metered flows during rain events with metered flows recorded at times without rain. Graph 2-3 shows the flows at the treatment plant during the same summer metering period along with the precipitation data recorded at the Logan-Cache Airport. Logan City Page 12

23 Graph 2-3: Summertime Sewer Flows and Precipitation The largest storm recorded during the meter period occurred just after midnight on July 30 th. This storm lasted approximately 6 hours with a total of 0.43 inches recorded at the Logan-Cache Airport. This was a significant rain event but not rare with a return period of less than 1 year. A 1 year 6-hour storm in Logan has a total depth of 0.7 inches. Collection systems need to be designed to convey daily peak sanitary flows plus the peak seasonal infiltration and any inflow that may enter the system during a rain event. Based on the data collected in Logan for this study, infiltration is a much larger flow contributor to then inflow from rain events. More flow data during rain events needs to be evaluated to gain a better understanding of the inflow to the system due to rain. More specifically, more data is needed during large rain events to understand how the system flows change as a result. A few other observations are made based on the flow data in Graph 2-3. First, the base nighttime flows in the system increased over a period of three or four days surrounding the short rain events that occurred. These increases indicate that the collection system has some delayed inflow or rainfall-induced infiltration around wet periods of time. Delayed Inflow is defined as the portion of total inflow that is generated from indirect connections to the collection system or connections that produce inflow after a significant time delay from the beginning of a storm. Delayed inflow sources include: sump pumps, foundation drains, indirect sewer/drain cross-connections, etc. Rainfall-induced infiltration cannot be distinguished from delayed inflow and is therefore included as part of delayed inflow. Delayed inflow sources have Logan City Page 13

24 a gradual impact on the collection system and flow decreases gradually upon conclusion of the rainfall event, and after peak inflow caused by direct connections (EPA, 2014). Some short duration increases in the recorded flows occurred during or right after some of the recorded storms. For example, the nighttime flows recorded immediately after the storm that occurred in the very early morning hours of July 30 th were significantly higher than other recorded nighttime flows. This is likely because of inflow that quickly entered the system during, or right after the 6-hour storm. Inflow that enters the system quickly through direct connections is called direct inflow. Direct Inflow is defined as the portion of total inflow which is from direct connections to the collection system such as catch basins, roof drains, manhole covers, etc. These inflow sources allow storm water runoff to rapidly impact the collection system (EPA, 2014). 2.5 SUMMER FLOW DATA COLLECTION Temporary flow meters were installed during the summer of 2014 in order gather flow data needed to have a well calibrated sewer model to match the higher seasonal summer flows. These meters were installed at strategic locations throughout the collection system. The flow data was combined with other meter data that Logan collected during the same meter period from permanent meters at the existing lift stations and at the treatment lagoons Summer Meter Schedule Flow data was collected throughout the collection system for a three-week period from July 22, 2014 through August 12, The start and end dates for the data collection vary slightly for some of the meter sites Summer Meter Equipment J-U-B rented twelve Hach 910 area velocity flow monitors and used one March McBirney Flo-Dar meter owned by Logan City to collect flow data from 13 temporary sites. These monitors measured flow depths and velocities to calculate flow and recorded measurements at fiveminute intervals during the metering period. Having multiple meters collecting data throughout the City at the same time allows for a comparison of flows and helps to isolate areas of interest or concern. The Hach 910 meters were equipped with submerged depth velocity sensors that use a pressure transducer to measure flow depths and measure velocity with sound waves, using the Doppler principle. The Flo Dar meter consists of a radar-based velocity measurement system and an ultrasonic-based pulse echo depth measurement system. Logan City provided additional flow data for the same meter period that was recorded at permanent meters located at the treatment lagoons and at some of the large lift stations in the Logan City Page 14

25 system. Many of the permanent meters measure flows from the surrounding communities that are connected to the collection system Summer Meter Locations The locations of the temporary summer meters are listed in Table 2-2 and shown in Figure 2: Flow Meter Locations. Table 2-2 also gives information about the pipe size metered and the start and end dates of the collected meter data. The meter locations in the table include a facility identification number which is the numbering system the City uses for all of the manholes in the collection system. Logan City Page 15

26 Table 2-2: Temporary Flow Meters TEMPORARY FLOW METER SITES METER FACILITY ID LOCATION DESCRIPTION In parking lot along the east side of 1000 West 1 SEMH00644 Street at approximately 1075 North and 400 to 500 feet east of 1000 West Street 2 SEMH North 875 West 3 SEMH North 975 West 4 SEMH North 990 West 5 Man Hole east of SEMH00408 by 120 feet 6 SEMH South 930 West 7 SEMH South 950 West 8 SEMH West 600 South 9 SEMH North 750 East 10 SEMH East 1405 North 11 SEMH East 1350 North 12 SEMH East 700 North 13 SEMH East 435 South 325 North 950 West (in parking lot just east of 950 West street) METER PERIOD to to to to to to to to to to to to to Logan City Page 16

27 2.5.4 Summer Flow Data Evaluation J-U-B graphed and evaluated the data collected by the temporary flow meters for the summer flow meter period. The following graphs are included in Appendix B for each of the temporary meter sites: Flow vs. Time Depth and Velocity vs. Time Velocity vs. Level Scatter Plot The Flow vs. Time graphs include the amount of precipitation in inches that was recorded on an hourly basis at the Logan Cache Airport during the summer meter period. Notes and conclusions about the flows recorded at each of the temporary sites are included in Appendix C. Logan City Page 17

28 3 EXISTING SYSTEM ANALYSIS 3.1 INTRODUCTION J-U-B created and calibrated a computer model to simulate and analyze the existing flows in the collection system. The model was created using InfoSWMM 5.1 modeling software which is a product of Innovyze Incorporated. InfoSWMM functions within ArcGIS software which allows for easy assimilation of other City mapping that is contained in Geographic Information Systems (GIS) shape files. The computer model and findings meet Utah Department of Water Quality capacity verification requirements for large collection systems. 3.2 COLLECTION SYSTEM REGULATORY REQUIREMENTS The Utah Department of Water Quality requires any municipality, or other political subdivision of the state that owns and operates a sewer collection system to comply with the Utah Sewer Management Program (USMP) as defined in Rule R of the Utah Administrative Code. Under the USMP, Logan City is required to have and implement a written Sewer System Management Plan (SSMP). Logan has a written plan that was completed in August of 2015 that meets the state requirements. The SSMP covers: General organizational structure for the system Operation and maintenance of the system Sewer defects Sewer design standards Sanitary Sewer Overflow (SSO) actions Grease, oil, sand and commercial management Monitoring and measuring System mapping Sewer backup flows Larger collection systems must also complete a System Evaluation and Capacity Assurance Plan (SECAP) to identify any potential system capacity deficiencies and a capital improvements plan to address capacity deficiencies. The Logan City collection system falls within the larger system category and is required to have a SECAP. The work done for this master plan meets the SECAP requirements for Logan City. 3.3 DEVELOPMENT REQUIREMENTS All new sewer system improvements within the city need to be constructed to meet current Logan City and State design requirements. This is true for public systems as well as sewer systems that are constructed as private utilities including collection piping and lift stations. Logan City Page 18

29 The city standards for design and construction shall be used in conjunction with Utah Administrative Code R Where a conflict exists between these two standards, the Administrative Code shall prevail. 3.4 MODEL DEVELOPMENT AND ASSUMPTIONS The hydraulic model consists of following inputs: Collection system geometry Flow input locations Sanitary flows Lift Station parameters Daily sanitary flow patterns (Diurnal Curves) Infiltration flows Flows from others and large water users The key assumptions used in the existing system model are explained in the following sections Collection System Geometry Assumptions The system geometry (Figure 1) consists of all of the collection system components such as: Gravity pipes Manholes Lift stations Force mains Diversions Other ancillary items such as pumps Each of the components has attributes assigned such as ground elevations, invert elevations, sizes etc. The attributes were provided by the Logan City GIS department and include some updates made during the model building process as errors or discrepancies were found. Notes have been added in the system attributes table within the model where changes were made to the system geometry data. Updating and adding data to the system layer in the model will be an ongoing effort in the future for the City to continue to improve the accuracy of the model Flow Input Location Assumptions J-U-B added flows to the collection system based on the water meter database provided by the City in a two-step process. 1. Assigned each water meter to the nearest sewer pipe and then to the sewer collection manhole immediately upstream Logan City Page 19

30 2. Reviewed the sewer lateral map data that was provided by Logan city to adjust flow input locations as needed Sanitary Flow Assumptions The daily sanitary flows (no I&I) in the system are equal to the daily culinary water use during the winter months. These flows were added based on the winter culinary water meter database that was provided by the City as described in Section 2.3 of this report. A small amount of flow was added to parks and other open spaces based on the estimated number or fixture units in restrooms or other plumbed structures. The flows from the open spaces are very minimal Pump Parameter Assumptions The parameters of the pumps in the existing lift stations were added based on data provided by the City from as-built records Diurnal Curves Assumptions Sewer flows vary throughout the day. The flow patterns during the day are known as diurnal curves. These diurnal curves allow the modeling software to quantify the flows throughout the day for the various types of land use. J-U-B initially input 5 different diurnal curves in the model that have been developed and adjusted by J-U-B over time to match flows that have been recorded in areas made up of the following flow land use categories: 1. Residential 2. Commercial 3. Industrial 4. Open Space (Parks with restrooms) 5. School These diurnal curves were adjusted during the calibration process (Section 3.3) to match the flows recorded by the flow meters. Graph 3-1 below shows the diurnal curves used in the model. The graph gives the percentage of the total daily volume that is assigned to each hour during the day for each of the curves. The diurnal curves represent only the sanitary flows and do not include any inflow or infiltration. Logan City Page 20

31 PERCENT OF DAILY FLOW Graph 3-1: Diurnal Curves 12% 10% 8% DIURNAL CURVES RESIDENTIAL COMMERCIAL INDUSTRIAL OPEN SPACE SCHOOL 6% 4% 2% 0% HOURS J-U-B assigned one of these diurnal curves to each of the sanitary flows added to the model based on the land uses that were included in the water meter databased provided by the City. There are many land uses in the City that could generate slightly different diurnal curves, but for the model, the curves were consolidated into the 5 major types shown in Graph 3-1. The land uses associated with the water meter database provided by the City are listed below in Table 3-1 along with the diurnal curve that was assigned for each of those land uses. Logan City Page 21

32 Table 3-1: Diurnal Curve Assignments Diurnal Curve Assignments City Land Use Diurnal Curve Assigned in Model CR MH MR-12 MR-20 MU Not Logan NR-6 PUB TC AP COM Community Commercial CS GW MU NC Not Logan PUB REC TC IP PUB MU PUB REC PUB MU (USU) PUB (USU) Residential Commercial Industrial Open Space Schools Logan City Page 22

33 The diurnal flow pattern assignments for the existing and future service areas are mapped in Figure 3: Diurnal Curve Pattern Assignments. The undeveloped parcels and some areas that are not connected to the sewer do not contribute flows in the existing model and were not assigned a flow pattern. Sanitary flow volumes are based on individual water meter data and not on the diurnal flow pattern Infiltration Assumptions Infiltration is assumed to be a constant base flow that is approximately equal to the average nighttime base flows. The meter data used to estimate infiltration was recorded by the temporary flow meters that were installed in July 2014 along with data from permanent meters for the same time period. Because of the limitation on the number of temporary meters installed, some assumptions were made about what localized areas may have more infiltration than other areas. For example, the island area near the Logan River has high ground water levels and many sections of older pipe that are not water tight. Because of these and other factors, this area was designated very high infiltration. On the other hand, some of the areas on the east bench have much lower infiltration because the pipes are newer, the ground water level is deeper in the ground and the soils in these areas drains much more freely. The developed part of the City was divided into regions and categorized into 5 different rates of infiltration. A proportionate fraction of the total infiltration in a region was assigned to each manhole within the region. The rates of infiltration per manhole were adjusted in each of the regions until the base nighttime flows in the model matched the base nighttime flows recorded by the temporary flow meters. Areas that will develop in the future do not add any infiltration to the existing model. The infiltration regions and the rates assigned to each region in the City are shown in Figure 4: Infiltration Rates. Table 3-2 lists the 5 existing infiltration rates used and the flow added as infiltration at each manhole for each of the assigned rates. Logan City Page 23

34 Table 3-2: Infiltration Rates Infiltration Rates Name Infiltration Added per Manhole (gpm) Very Low 0.2 Low 0.5 Medium 0.6 High 3.2 Very High Inflow No inflow was added to the model because: The infiltration flows measured in the system in the summer are much greater than the flows that may be added by inflow during a typical summer rain event. The small rain events that were recorded during the summer meter period did have some varying effects on the flows in the system depending on the location in the system. More sewer flow data needs to be collected and evaluated during large storm events to quantify the effects from inflow Flows from Others and Large Water Users The following cities near Logan are connected to the collection system (Figure 1): Smithfield Hyde Park North Logan River Heights Providence Nibley Providence City has two connection points and Smithfield and Hyde Park share a single connection point. Each connection has a flow meter that records the flows as they enter the collection system. Flows were added to the model at the connection points to simulate the Logan City Page 24

35 flows that enter from each of these outside communities. The flows were shaped into diurnal flow patterns to match the patterns recorded by the meters. The flow patterns recorded by the meters from the contributing communities are included in Appendix D. Utah State University (USU) is another large contributing entity that is connected to the collection system at multiple locations. Winter-water usage data was used to estimate the sanitary flows that come from USU in the same fashion as sanitary flows were added throughout the rest of the City. Summer infiltration from USU was estimated based on flow meter data from the summer temporary meters as explained in Section USU has many small pumps from building basements that turn on and off multiple times during each day for short periods. These pumps add very little volume to the system with short peaks that attenuate quickly in the collection system. Tyco Electronics is a large industrial water user located at 710 North 600 West in Logan that is connected to the sewer collection system. Hourly water use data from meters at Tyco were used to create a more accurate diurnal flow pattern. The flows from other large water users such as Gossner Foods and Schreiber Foods are based on monthly winter water use. The typical industrial diurnal flow pattern was assigned to these water users and other industrial water users. 3.5 COST ESTIMATING ASSUMPTIONS The model development is important because it identifies areas where existing or future system deficiencies exist in the collection system. Deficiencies are typically addressed by making some kind of improvement to the system. Funds are required to make most sewer system capacity improvements. At the master planning stage, many assumptions are required to estimate the costs of future improvements because there is a fairly high level of uncertainty about challenges or obstacles to projects that will not be identified until a design process is completed. As a given improvement gets designed, the uncertainty is reduced. J-U-B has prepared conceptual cost estimates for improvements that are needed in the collection system now, at year 2020, year 2005 and at build out. Cost estimates for this plan are based on J-U-B bid tabulation records for sewer collection and lift station projects and pipe material costs provided by pipe suppliers. For piping projects, it is assumed that the improvements will be made utilizing conventional open-cut construction in city roadways with manholes will be placed every 350 feet. The project costs include an additional 40% factor (40% of the estimated construction cost) to account for engineering services and for uncertainty in items that will be required for construction. A basic unit price summary table is included in Appendix E. Logan City Page 25

36 28-Jul 29-Jul FLOW (gpm) 3.6 MODEL CALIBRATION J-U-B calibrated the model by adjusting the inputs until the model flows matched the existing system flows as recorded by the meters. The first step in the calibration process is to choose a day with relatively high flows to match with the computer model flows. A day with relatively high peak flows is desired in order to avoid underestimating existing and future flows which may lead to having an unexpected exceedance of system capacity. As mentioned earlier in the report, the flows in the system are typically the largest in the summer when irrigation water is in the irrigation ditches. Upon reviewing the flow data collected in the summer of 2014, Monday July 28, 2014 was selected as the day to match with the model. In many collection systems, peak flows during a week occur on weekends when people are at home. However, the peak flows recorded in Logan on the weekdays were higher than during the weekends. This is probably because a large portion of Logan s flows come from commercial and industrial entities that do not operate on the weekends. Calibration involved an iterative process of superimposing the flow graphs from the temporary flow meters and from the treatment plant from July 28, 2014 over the model-generated diurnal flow curves. Then, the flow generating model parameters (diurnal curve shape, infiltration etc.) were adjusted to match the metered flows. An example calibration flow graph is shown below in Graph 3-2 for the temporary meter that was installed near the North Logan connection point. Graph 3-2: Example Calibration Flow Graph W Parking Lot Meter Model data DATE - July 28, 2014 Logan City Page 26

37 All of the flow calibration graphs are included in Appendix F to show how the model flows compared to the actual metered flows. A summary of how the flows in the calibrated model compared to the flows measured by the flow meters is tabulated in Appendix G. 3.7 EXISTING SYSTEM EVALUATION The existing model simulates the existing flows based on the winter culinary water usage plus summer infiltration to match the flows recorded in the system on Monday July 28 th Four specific items were evaluated as part of the existing system evaluation: 1. Depth of Flow over Diameter of Pipe (d/d) 2. Reserve Capacity 3. Hydraulic Grade Line Profiles 4. System Condition 5. Lift Station Analysis Depth of Flow over Diameter of Pipe (d/d) A quick way to display how well a collection system accommodates flows is by observing the depth of flow in a pipe as a ratio of the pipe s inside diameter. The illustrated pipe shown in diagram 3-1 below represents a pipe flowing less than half full. Diagram 3-1: Pipe Flow Less than Half Full A pipe that is full would have a d/d value of 1.0. While a pipe flowing half full would have a d/d value of 0.5. Larger pipes are able to handle more flows than are smaller pipes, at equivalent d/d values. Larger pipes have more reserve capacity per increment of d/d value. The InfoSWMM modeling software reports d/d values based on the hydraulic grade line throughout the collection system. If there is a downstream choke point in the collection system that causes the water to back up and raise the hydraulic grade line to levels above the top of a pipe, InfoSWMM reports a d/d value of 1.0. The d/d values typically vary along the length of pipe segments. Some pipe segments have flows that transition between full or partially full. The d/d values recorded in this report are at the upstream end of each pipe segment in the model. Logan City Page 27