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HomeMy WebLinkAboutE1 Commission Memorandum REPORT TO: Honorable Mayor and City Commission FROM: Bob Murray, Project Engineer Chris Kukulski, City Manager SUBJECT: Wastewater Facility Plan MEETING DATE: May 8, 2006 BACKGROUND: The City has undertaken the task of updating its facility plans. The team of Morrison Maierle/HDR was selected for the Wastewater plan. The draft plan has now been completed and is ready for review and comment. Attached is a copy of the executive summary for the document which will be the basis of the presentation to the Commission. This meeting will be for the Commission to discuss and review the findings of the plan with the consultant. A subsequent public hearing will be held on the 22nd. RECOMMENDATION: Listen to presentation; ask questions for clarification, discussion. FISCAL EFFECTS: N/A ALTERNATIVES: None Respectfully submitted, _________________________________ ____________________________ Robert J. Murray Jr., Project Engineer Chris A. Kukulski, City Manager Attachments: Easement Documents Report compiled on 5/3/2006 i H:\0417\048\DOCS\Second Draft\Chapter 1.doc Bozeman Wastewater Facilities Plan Chapter 1 Executive Summary Prepared by: James Nickelson, MMI Reviewed by: Bob Morrison, MMI Amanda McInnis, HDR ii H:\0417\048\DOCS\Second Draft\Chapter 1.doc Table of Contents 1.1 INTRODUCTION............................................................................................................1-1 1.2 BASIS OF PLANNING....................................................................................................1-1 1.3 COLLECTION SYSTEM ANALYSIS ..........................................................................1-2 1.4 WASTEWATER TREATMENT PLANT ANALYSIS..............................................1-3 1.5 RECOMMENDATIONS.................................................................................................1-5 1.5.1 Collection System Recommendations...................................................................1-5 1.5.2 Wastewater Treatment Plant Recommendations................................................1-7 List of Tables Table 1-1 – Projected Influent Wastewater Flows and Loads ................................................ 1-1 Table 1-2 – Probable Total Capital Cost of Recommended WWTP Alternatives ............... 1-5 Table 1-3 – Collection System – Priority 1 Projects ................................................................. 1-6 Table 1-4 – Bozeman WWTP Phase 1 Improvements – Probable Project Capital Cost ... 1-8 Table 1-5 – Bozeman WWTP Phase 2 Improvements – Probable Project Capital Cost ... 1-9 Table 1-6 – Bozeman WWTP Phase 3 Improvements – Probable Project Capital Cost ... 1-9 1-1 H:\0417\048\DOCS\Second Draft\Chapter 1.doc Recommended design population for year 2025 is 92,500 1.1 INTRODUCTION In 2004 the City of Bozeman undertook the task of planning for the future of their wastewater infrastructure. The goal of the planning effort was to define the existing infrastructure, estimate future populations and wastewater quantities, determine improvements needed to meet future permit requirements and accommodate growth, and develop an improvements plan for the wastewater system. This executive summary briefly describes the contents of the plan and the resulting recommendations. 1.2 BASIS OF PLANNING The starting point for projecting wastewater system needs is to define a study boundary and estimate future populations and wastewater flows and loads. A study area was selected that includes approximately 42,400 acres. The estimated growth rate for the City of Bozeman was approximately 5% per year for the period 2001 to 2005, and is continuing at an accelerated pace that is exceeding the 5% annual average. In order to effectively plan for future growth, a year 2025 population of 92,500 based on a 5% annual growth rate is utilized for the planning period. The following table summarizes the design population and resulting projected wastewater flows and loads through the planning period. Table 1-1 – PROJECTED INFLUENT WASTEWATER FLOWS AND LOADS Flow and Load Parameters 2005 2010 2015 2020 2025 DESIGN POPULATION 34,900 44,500 56,800 72,500 92,500 ANNUAL AVERAGE FLOW, mgd 5.20 6.70 8.50 10.90 13.90 ANNUAL AVERAGE CARBONACEOUS BIOCHEMICAL OXYGEN DEMAND (CBOD) LOAD, lb/day 9,400 12,000 15,300 19,600 25,000 ANNUAL AVERAGE TOTAL SUSPENDED SOLIDS (TSS) LOAD, lb/day 9,800 12,500 15,900 20,300 25,900 1-2 H:\0417\048\DOCS\Second Draft\Chapter 1.doc Nearly 110 miles of sewer lines and 2 lift stations at a total estimated cost of $70 million will be required to provide service to the study area. 1.3 COLLECTION SYSTEM ANALYSIS The wastewater collection system consists of approximately 150 miles of gravity sewer mains, approximately 3,300 manholes and six lift stations, and associated forcemains that discharge wastewater to the wastewater treatment plant. The collection system consists of pipe ranging from new PVC pipe associated with recent expansions and increasing development, to clay pipe exceeding 100 years old. Few capacity problems were identified at existing flows. Some condition related problems in the existing system include excessive amounts of root cutting and clay pipe maintenance, infiltration in areas of high groundwater and suspected sump pump connections, and a non-quantitative approach to setting existing system rehabilitation priorities. It is recommended that a more proactive approach be taken to rehabilitate the aging pipe network, including a specific annual sewer main rehabilitation program. Specific conclusions regarding the existing collection system are as follows: • The City has an ongoing Closed-Caption Television (CCTV) program that includes reviewing new and existing infrastructure, however; due to time and staff constraints, much of the existing system goes un-reviewed unless a problem occurs. The City should establish a dedicated program to CCTV and record, preferably to a GIS system, approximately 20- percent of their existing collection system each year to identify specific problem areas associated with the aging pipe. This would result in a 5-year turn-around time to inspect the entire system before the inspection cycle begins again. ¾ The City’s current maintenance protocol includes evaluating CCTV reports and recording the information to a spreadsheet. There is currently no quantitative scoring system in place. Additionally, the City’s equipment lacks lateral inspection capabilities. Systems are available that include CCTV inspection equipment with lateral inspection capabilities and a pipe reporting software system. The software includes a sewer scoring system for structural and root defect problems. Scoring should be associated with each manhole and segment of pipe with a feature identification number, in order to more accurately address system rehabilitation needs. ¾ Several rehabilitation projects identified in the 1998 City of Bozeman Wastewater Facility Plan have not yet been completed. Additionally, the City has identified spot repairs including manhole replacement, manhole lining, pipe lining and pipe replacement projects that need to be addressed. The significant increase in wastewater flows over the planning period will require substantial improvements and expansions of the collection system. Chapter 6 provides recommendations for the City of Bozeman’s future wastewater collection system improvements which include major and minor infrastructure replacement and paralleling projects, an outline of future extensions and lift stations with proposed sizing, and a recommended plan to reduce infiltration and inflow. 1-3 H:\0417\048\DOCS\Second Draft\Chapter 1.doc The existing WWTP has reached its design loadings. Growth and new permit requirements drive the need for $55 million in improvements. In order to serve the study area, over 515,000 feet of new sewer and two lift stations will be required. In addition, approximately 95,000 feet of existing sewer interceptors and trunk mains are in need of upsizing or installation of paralleling pipes. Key interceptors that will require upsizing and/or parallel pipes include the Frontage Road Interceptor, the extension of both the Rouse Interceptor and Front/Tamarack Interceptors, and the main interceptor into the wastewater treatment plant. Recommendations for upsizing existing sewer lines listed in Chapter 6 include $14 million in scheduled improvements. If the future interceptors that are needed to provide service throughout the study area are included, the needed improvements approach $70 million (2005 dollars). In addition to growth related improvements, it is imperative that aging infrastructure become a high priority issue to the City of Bozeman. While capacity issues have not been identified in areas of older pipe, continuing problems with root and structural defects creates potential blockages and capacity issues that predictive modeling cannot foresee. It is only with diligent effort to quantify these problems with an effective inspection, scoring, and maintenance program, that infrastructure degradation can be managed and addressed, thus ensuring the continued integrity of Bozeman’s collection system. 1.4 WASTEWATER TREATMENT PLANT ANALYSIS The Bozeman Wastewater Treatment Plant (WWTP) is a secondary treatment facility utilizing the activated sludge process. The Bozeman WWTP was originally constructed in 1970, and has been expanded or modified five times. The original plant was a very basic secondary treatment facility. In 1982, the WWTP was expanded and modified to a more advanced activated sludge treatment plant. In 1983, the plant added final effluent polishing and sludge storage facilities. In 1998, the two digested sludge storage lagoons were converted to a single larger lagoon and another sludge storage lagoon was added. In 2002 and 2003, the City expanded and modified the plant again adding a primary clarifier and improving the anaerobic digesters. Finally, the City has recently completed construction of a project that included adding a secondary clarifier, improvements to the headworks and aeration facilities and a new computer based supervisory control and data acquisition system. The following summarizes the most relevant findings relative to the existing conditions at the wastewater treatment plant: 1. Flows to the Bozeman WWTP have not increased significantly over the last decade even though the population has increased significantly. This is an indication that the City’s infiltration and inflow (I/I) removal program is working by reducing the volume of groundwater and/or rainfall that reaches the wastewater collection system. Lower than average precipitation over the past several years may have some impact on recorded flows. Average annual wastewater flows from 2001 to 2005 have been just below 5 mgd. (Design flow of the existing facility is 5.8 mgd.) 2. Wastewater strength parameters (CBOD, TSS, and ammonia) have increased significantly over the last decade. These parameters are higher than normally expected for Bozeman’s population, 1-4 H:\0417\048\DOCS\Second Draft\Chapter 1.doc indicating that commuter/day users are exerting more of a demand on the wastewater system than in the past. 3. The Bozeman WWTP consistently meets or exceeds its discharge permit requirements. 4. The WWTP was originally designed to provide an annual average treatment capacity of 5.80 mgd. Design annual average CBOD and TSS loadings were 8,580 and 7,220 lb/day, respectively. Current (2001 to 2005) annual average flows to the plant are about 4.9 mgd, or about 85 to 90 percent of the rated capacity. However, current CBOD and TSS loads have exceeded the design values by 4 to 16 percent. This necessitates that the WWTP unit process design capacities be re-evaluated with current wastewater flow and strength characteristics. 5. For the most part, the plant’s current hydraulic conveyance system (pipes, channels, etc.) can handle the design peak hourly flow without submerging weirs or overtopping walls. However, the headworks at the influent end of the plant and the effluent end of the plant from the secondary clarifiers to the outfall to the East Gallatin River does have some hydraulic bottlenecks that should be addressed. 6. The City’s activated sludge aeration system, and the bio-solids treatment and disposal system have capacity limitations. The aeration blower system, anaerobic digestion system and sludge storage system need expanding. In addition, the City will need more farmland for final disposal of the sludge than it currently has available. Alternate sludge handling and disposal systems should be investigated and compared to just expanding current processes. 7. The WWTP has a number of equipment items over 20 years old and some over 35 years old. Much of the existing equipment should be scheduled for replacement or refurbishment over the next 5 to 10 years. 8. Several upgrades to the existing plant are considered desirable or critical to utilize the existing plant to its full rated capacity of 5.80 mgd. In order to provide capacity for the design wastewater flows and loads through the planning period, the wastewater treatment plant will need to be expanded and additional processes added. The projected flows and loads at the end of the study period represent an increase of more than 100% over existing process capacities. In addition, current and anticipated discharge limitations will require that the wastewater treatment plant be upgraded to a more advanced treatment process. Solids handling facilities and treatment facilities will also require modifications. Chapter 8 evaluates multiple alternatives for liquid treatment unit processes and solids handling and treatment alternatives. The recommended liquid stream process facility for the 20 year planning period is an advanced biological nutrient removal system with secondary clarification and effluent filtration. It is recommended that the City continue to stabilize their sludge with anaerobic digestion and to land apply biosolids; however, it is recommended that screw press dewatering facilities be added. Table 1-2 presents the total estimated capital cost of the recommended alternatives. The total cost of $55 million (2005 dollars) includes the estimated construction cost of the facilities and an allowance for technical services. The costs are based on year 2025 facilities. 1-5 H:\0417\048\DOCS\Second Draft\Chapter 1.doc Table 1-2 PROBABLE TOTAL CAPITAL COST OF RECOMMENDED WWTP ALTERNATIVES (a) Project Component Description Probable Cost Construction of Liquid Treatment Systems Construction of Solids Handling/Treatment Systems Subtotal Construction Cost $33,570,000 12,300,000 $45,870,000 Engineering, Legal, Administrative and Other Related City Costs at 20% (b) $9,180,000 Total Capital Cost $55,050,000 (a) Cost estimates are prepared in mid-2005 dollars and should be advanced to the mid-point of construction. (b) Costs for technical services and related City personnel services are based on a percent of total construction for budgeting purposes only. Final costs for technical services will be negotiated during the final design phase of the project and may vary depending on actual site conditions, availability of existing data, the final scope of services, etc. 1.5 RECOMMENDATIONS The following is a summary of the recommendations for the collection system and wastewater treatment plant improvements. Additional details are provided in Chapters 4, 6 and 10 regarding the collection system and Chapters 5, 8 and 10 in regards to the wastewater treatment plant. 1.5.1 Collection System Recommendations Much of the City’s collection system is old and its condition is unknown. Several changes are recommended to move to operating in a more pro-active mode where problems are anticipated, repairs are scheduled, emergencies avoided, rather than in a reactive mode. • Chapter 4 identifies approximately 4,500 feet of sewer main that should be reviewed in the field to assess if capacity problems exist at current flows. • It is recommended that the annual sewer main rehabilitation program receive increased funding to address system wide problems associated with aging infrastructure. • City staff indicate that many crawl space sump pumps are connected to the sewer system and that this has been a practice for over 20 years. There is a City ordinance on record to prevent crawl space pumps from discharging to the sanitary sewer, but this has not been enforced. A program should be implemented to address and eliminate such connections to the collection system. • The City has an ongoing CCTV program for new and existing sewer lines; however, much of the existing system goes un-reviewed unless an emergency occurs. The City should establish a dedicated program to CCTV and record, preferably to GIS, approximately 20-percent of their existing collection system each year to identify specific problem areas associated with the aging pipe. This would result in a 5-year turn-around time to inspect the entire system 1-6 H:\0417\048\DOCS\Second Draft\Chapter 1.doc Eight high priority collection system projects recommended totaling $8 million. before the inspection cycle begins again. It will require City staff approximately 160 working days per year with a full-time CCTV staff to collect data on 20-percent of the existing system. • The City’s current maintenance protocol includes evaluating CCTV reports and recording the information to a spreadsheet. There is currently no quantitative scoring system in place. Additionally, the City’s equipment lacks lateral inspection capability. Systems are available that include CCTV inspection equipment with lateral inspection capability and a pipe reporting software system. The software includes a sewer scoring system for structural and root defect problems. Scoring should be associated with each manhole and segment of pipe with a feature identification number, in order to more accurately address system rehabilitation needs. • With an expanding and aging collection system and recommendations for additional assessment activities, additional operations staff will likely be required in the near term. • Eight high priority projects based on both capacity and condition are identified in Chapter 6. The following table describes the projects totaling approximately $8,000,0000 in improvements in 2005 dollars. Table 1-3 Collection System - Priority 1 Projects Project Name Current Diameter (inches) Future Diameter (inches) Replacement or Parallel Approx. Length of Pipe (LF) S. Rouse Trunk: E Babcock to Kagy 8 24/21 Replacement 8,420 Kagy from 3rd Ave S to 7th Ave S 8 21 Replacement 1,400 Mendenhall to Tamarack from Grand to Rouse 6 to 18 6 to 18 Lining/ Replacement 12,275 (6, 8) 5,150 (10, 15, 18) Front Street: Tamarack/Rouse to Haggerty Various 24/21/18 Replacement 8,330 College to Babcock from 5th Avenue to 11th Avenue Various N/A Lining/ Replacement 15,750 (line) 6,575 (repl) 21-inch Interstate Crossing/Wal-Mart 21 21 Lining/ Replacement 2,400 Front Street Collector 8 12 Replacement 410 Babcock between Hunters Way and Silver Maple 8 12 Replacement 200 It is important that the City continue to monitor the impacts that expansion of the service area has on the existing collection system and ensure that needed capacity improvements are realized with the 1-7 H:\0417\048\DOCS\Second Draft\Chapter 1.doc Three phase approach to WWTP Improvements Recommended. expansion of the service area. This plan provides the framework to allow for the service area to be expanded; however, scheduling of the improvements is dependent on the need to provide sewer service to specific areas. Twenty-five specific projects have been identified to provide additional capacity within the existing collection system area in addition to forty projects that provide extensions into the expanded service area. The timing of such projects are dependent on the location of future development projects and their impact on the collection system capacity. 1.5.2 Wastewater Treatment Plant Recommendations Based on the priority of the needed improvements and the desire of the City to spread out the capital outlays necessary to construct the required facilities, it is recommended that the treatment plant improvements be implemented in three phases as summarized below. The project cost estimates summarized below are advanced forward to the estimated mid-point of construction for purposes of planning financing. Average inflation rates of 5 percent per year from mid-2005 to 2008, 4.5 percent per year from mid-2005 to 2014, and 4 percent per year from mid-2005 to 2020 were used to estimate future costs. An allowance of 20 percent of the probable construction cost is also included to account for future preliminary and final engineering, bid phase services, construction administration, grant administration (if applicable), legal, and City administration staff services. Recommended Phase 1 improvements to the Bozeman advanced WWTP include the following: • New Headworks Building. • New Primary Effluent Lift Station. • New BNR bioreactor basins. • Modify the existing aeration basins to plug flow arrangement and add aeration system capacity including a new blower building. • Two new 85-foot diameter secondary clarifiers and a new RAS/WAS pump station. • New low lift pump station with provisions for connection to a future effluent filtration system. • New UV disinfection structure. • New liquid chlorine storage/feed system for odor control, RAS bulking control, and standby disinfection. • New 750 KW emergency power engine generator. • Construct a parallel 36-inch outfall pipeline. • New anaerobic digester and a new digester control building. The Phase 1 projects are critical to the City because they address hydraulic and organic load capacity issues (the existing plant is rapidly approaching or is already at its design capacity), future treatment requirements for nitrogen and phosphorous, unsafe and difficult to meet permit requirements with the existing chlorination and de-chlorination systems, and biosolids treatment capacity issues. Table 1-4 summarizes the total project capital cost for the Bozeman advanced WWTP Phase 1 improvements. 1-8 H:\0417\048\DOCS\Second Draft\Chapter 1.doc Table 1-4 BOZEMAN WWTP PHASE 1 IMPROVEMENTS PROBABLE PROJECT CAPITAL COST Project Component Probable Cost(a) Liquid Treatment Improvements Solids Handling and Treatment Improvements $23,900,000 $3,900,000 Subtotal Probable Construction Cost $27,800,000 Engineering, Legal, Administrative And Other Related City Costs at 20%(b) $5,600,000 Total Capital Cost $33,400,000 (a) Cost estimates have been advanced from mid-2005 dollars to mid-2008 dollars (the estimated Phase 1 mid-point of construction) assuming an inflation rate of 5 percent per year. (b) Costs for technical services and related City personnel services are based on a percent of total construction for budgeting purposes only. Final costs for technical services will be negotiated during the final design phase of the project and may vary depending on actual site conditions, availability of existing data, the final scope of services, etc. Recommended Phase 2 improvements to the Bozeman advanced WWTP would extend the capacity of the plant and further improve effluent quality and solids handling flexibility. These improvements are summarized below: • Add a third grinder/screen unit to the Headworks. • One new primary clarifier with a primary sludge pump station. • Replace the clarifier mechanisms on two existing clarifiers. • Replace the existing primary sludge and scum pumps in the gravity thickener pump station and replace existing sludge/scum piping with glass-lined piping. • Add new primary effluent pump(s). • Construct second half of the new BNR bioreactor basins. • New phosphorous removal chemical feed system and primary sludge fermentation system. • Add new blower(s) to Blower Building. • One new 85-foot diameter secondary clarifier and add new RAS and WAS pumps to RAS/WAS pump station. • New effluent filtration structure with at least four cloth media filter units. • New liquid sludge storage tank and new screw press dewatering building with one screw press and odor control facilities. • New dewatered sludge storage facility. • Purchase new biosolids haul and application equipment. • New Administration/Laboratory Building. The Phase 2 project components address increasingly stringent effluent quality requirements and critical solids handling system’s flexibility and performance. Table 1-5 summarizes the estimated total project capital cost for the Phase 2 improvements. 1-9 H:\0417\048\DOCS\Second Draft\Chapter 1.doc Table 1-5 BOZEMAN WWTP PHASE 2 IMPROVEMENTS PROBABLE PROJECT CAPITAL COST Project Component Probable Cost(a) Liquid Treatment Improvements Solids Handling and Treatment Improvements $17,400,000 $10,900,000 Subtotal Probable Construction Cost $28,300,000 Engineering, Legal, Administrative And Other Related City Costs at 20%(b) $5,700,000 Total Capital Cost $34,000,000 (a) Cost estimates have been advanced from mid-2005 dollars to early 2014 dollars (the estimated Phase 2 mid-point of construction) assuming an inflation rate of 4.5 percent per year. (b) Costs for technical services and related City personnel services are based on a percent of total construction for budgeting purposes only. Final costs for technical services will be negotiated during the final design phase of the project and may vary depending on actual site conditions, availability of existing data, the final scope of services, etc. The recommended Phase 3 improvements to the Bozeman advanced WWTP would extend the plant capacity to the projected year 2025 conditions. These improvements are summarized below: • Construct the fifth primary clarifier. • Add new primary sludge pumps(s) and piping at the newer primary sludge pump station. • Construct the eighth secondary clarifier. • Add two new cloth media filter units to the final effluent filtration structure. • One new anaerobic digester. • Add one screw press dewatering unit. Table 1-6 presents the estimated total project capital cost of the recommended Phase 3 improvements. Table 1-6 BOZEMAN WWTP PHASE 3 IMPROVEMENTS PROBABLE PROJECT CAPITAL COST Project Component Probable Cost(a) Liquid Treatment Improvements Solids Handling and Treatment Improvements $4,800,000 $2,700,000 Subtotal Probable Construction Cost $7,500,000 Engineering, Legal, Administrative And Other Related City Costs at 20%(b) $1,500,000 Total Capital Cost $9,000,000 (a) Cost estimates have been advanced from mid-2005 dollars to early 2020 dollars (the estimated Phase 3 mid-point of construction) assuming an inflation rate of 4 percent per year. (b) Costs for technical services and related City personnel services are based on a percent of total construction for budgeting purposes only. Final costs for technical services will be negotiated during the final design phase of the project and may vary depending on actual site conditions, availability of existing data, the final scope of services, etc. 1-10 H:\0417\048\DOCS\Second Draft\Chapter 1.doc $33 million Phase 1 WWTP project should be under taken now. It is our opinion that the recommended alternatives and three project phases is the best approach to meet the City’s growth and regulatory requirement demands, minimize WWTP operational difficulties and eliminate current problem areas, and minimize the cost impacts that would result from excessive phasing. It is recommended that the City proceed with the Phase 1 Project at this time in order to be able to commence construction in 2007.