Metropolitan St. Louis Sewer District. CSO LTCP Update EXECUTIVE SUMMARY

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1 Metropolitan St. Louis Sewer District Purpose The Metropolitan St. Louis Sewer District (MSD) provides wastewater and stormwater service to approximately 1.4 million people in a 535-square-mile service area encompassing the independent City of St. Louis and most of St. Louis County. The collection system owned and operated by MSD consists of over 9,600 miles of pipe, making it the fourth largest in the United States. Most of MSD s customers are served by separate sanitary and storm sewers. However, approximately 75 square miles of St. Louis City and adjoining St. Louis County are served by a combined sewer system, as shown in Figure ES-1. During dry weather, the capacity of the combined sewer system is sufficient so that wastewater is conveyed to MSD s wastewater treatment plants. During heavy rainfall, the combination of stormwater and wastewater may exceed the capacity of the combined sewer system. The excess flow, called combined sewer overflow (CSO), is discharged directly to the Mississippi River or to one of the river s tributary streams through permitted outfall pipes. Figure ES-1 MSD s Service Area and Combined Sewer Area Page ES-1 February 2011

2 The U.S. Environmental Protection Agency (EPA) issued a CSO Control Policy in 1994 intended to eventually bring CSOs nationwide into compliance with the Clean Water Act. The goals of CSO control are to: Ensure that if CSOs occur, they are only as a result of wet weather, Bring all wet weather CSO discharge points into compliance with the technology-based and water quality-based requirements of the Clean Water Act, and Minimize the impacts of CSOs on water quality, aquatic biota, and human health. The policy requires agencies with CSOs to prepare a Long-Term Control Plan (LTCP) describing how they will accomplish these goals. MSD prepared and submitted its original LTCP to the Missouri Department of Natural Resources (MDNR) in 1999, but due to conflicts between Missouri law and the federal Clean Water Act, MDNR could not approve the submitted plan. A second, phased-implementation LTCP was prepared for MDNR in 2004 in accordance with State laws and regulations. This LTCP was approved by MDNR but was later disapproved by EPA. Following discussions aimed at resolving the conflicts, EPA and MDNR requested that MSD update its original LTCP. This report describes the development and selection of MSD s updated plan for controlling combined sewer overflows. Certain controls from the 2004 phased-implementation LTCP have been incorporated into the current LTCP, along with additional control measures to meet the requirements of the Clean Water Act and CSO Control Policy. The 2004 phased-implementation LTCP is no longer considered to be in effect. CSO Locations and Impacted Waterways Within MSD s combined sewer area there are a total of 199 CSO outfalls. These outfalls are included as permitted discharge locations in the Missouri State Operating Permits issued to MSD by MDNR. One permit covers the Bissell Point service area (MO ) while the other covers the Lemay service area (MO ). During wet weather, these CSOs may discharge to the following waterways: Mississippi River (60 CSOs) River Des Peres Lower and Middle (52 CSOs) River Des Peres Upper (39 CSOs) Tributaries to the River Des Peres (42 CSOs) Maline Creek (4 CSOs) Gingras Creek (1 CSO) Gravois Creek (1 CSO, recently separated and removed) The locations of these waterways and CSOs are shown in Figure ES-2. Characteristics of these waterways, including applicable beneficial designated uses, are described below. None of these waterways have been identified as meeting the definition of Sensitive Areas contained in the CSO Control Policy. Sensitive Areas are those that should receive the highest priority for potential elimination or re-location of CSOs if feasible. Page ES-2 February 2011

3 Metropolitan St. Louis Sewer District Figure ES-2 CSO and Receiving Water Locations Lower & Middle River Des Peres The Lower River Des Peres starts at the confluence with Deer Creek and extends about six miles downstream to the Mississippi River. Flow consists of a small base flow, and large volumes of intermittent storm drainage from runoff, storm sewers, and combined sewers. The Lower River Des Peres is subject to backwater from the Mississippi River. This segment of the River Des Peres is classified for livestock & wildlife watering, warm water aquatic life protection, and secondary contact recreation1. The Middle River Des Peres extends approximately seven and one-half miles from the intersection of Dartmouth and Harvard Streets in University City to the confluence with Deer Creek. The upper four and one-half mile reach has been enclosed and is a combined sewer. The lower three mile reach, beginning near the Macklind Pump Station, is an open channel with a concrete base and concrete or riprap slopes. Flow is intermittent, consisting entirely of storm drainage from the Upper River Des Peres and combined sewers. The Middle River Des Peres is unclassified. 1 Designated uses are based on 10 CSR , Water Quality Standards, July 31, 2008, and revisions approved by Missouri Clean Water Commission on July 1, Page ES-3 February 2011

4 Upper River Des Peres The Upper River Des Peres extends approximately six miles in the Lemay service area from near Ashby and Warson Roads to the intersection of Dartmouth and Harvard Streets in University City. Flow is intermittent, and consists of storm drainage from separate storm sewers and overflows from combined sewers. The Upper River Des Peres is unclassified. Maline Creek Maline Creek extends approximately seven miles from east of Lambert-St. Louis International Airport through the Bissell Point service area to the Mississippi River. Flow is intermittent, and consists mostly of storm runoff and drainage from storm sewers. The lower reaches of the creek are subject to backwater from the Mississippi River. One mile of the creek is classified for livestock & wildlife watering, warm water aquatic life protection, and recreational uses. The lower half-mile segment, which receives CSO discharges, is classified for secondary contact recreation. The upper halfmile segment, above the CSO locations, is classified for whole body contact recreation (Class B). Mississippi River The Mississippi River at St. Louis receives significant point and nonpoint source loads from a 697,000 square mile drainage area encompassing all or part of 13 states, as well as local discharges from municipal, industrial, and agricultural wastewater treatment facilities located in St. Louis City and St. Louis County, Missouri, and Madison and St. Clair Counties, Illinois. The Mississippi River at St. Louis has a daily average flow of approximately 175,000 cubic feet per second. The segment of the river that receives CSO flows from MSD s service area is classified for irrigation, livestock & wildlife watering, warm water aquatic life protection, drinking water supply, industrial process and cooling water supply, and secondary contact recreation. Two Use Attainability Analyses have been conducted to support the secondary contact recreation use designation. Assessment of Current CSO Impacts To assess the impact of CSOs on these waterways, MSD collected in-stream water quality data and developed hydraulic models of its combined sewer system. Computer models of the CSO-impacted portions of the River Des Peres and Maline Creek were also developed. In developing these models, it was also necessary to model the runoff from portions of these watersheds that are served by separate stormwater systems. These computer models were calibrated to flow, rainfall, and water quality data collected over a multi-year period. A review of existing water quality data was conducted to determine parameters that should be modeled to assess the impact of CSOs. This review concluded that, for the tributaries receiving CSOs, bacteria and dissolved oxygen are parameters of concern, and ammonia is a potential parameter of concern. For the Mississippi River, neither bacteria, dissolved oxygen nor ammonia are parameters of concern that require modeling to assess the impact of CSOs. Therefore, water quality data alone were used to assess impacts on the Mississippi River. CSO planning was based on typical or average year conditions, in accordance with EPA guidance. MSD selected the year 2000 rainfall as representative of system-wide average annual conditions, based on a detailed statistical analysis of 57 years of hourly rain data from Lambert-St. Louis International Airport. Year 2000 Mississippi River stage, which influences backwater conditions in the tributaries, was also deemed to be typical, based on a stage-exceedance analysis using 75 years of daily river data. Page ES-4 February 2011

5 The hydraulic models of the combined sewer system allowed estimation of CSO overflow volumes and frequencies to the various waterways for the average year conditions, as summarized in Table ES-1. Waterway CSO Volume Number of (billion gallons) Overflow Events River Des Peres and tributaries Maline Creek Gingras Creek Mississippi River Total 13.3 Table ES-1 Estimated CSO Occurrence for Average Year (Year 2000) The estimated volumes were used to calculate pollutant loadings from the combined sewer system. Water quality in the River Des Peres and Maline Creek was modeled for the average year conditions using the calculated loadings from the CSOs, separate storm runoff, and upstream boundaries. Simulated water quality parameters included E. coli bacteria, carbonaceous biochemical oxygen demand (CBOD), nitrogen (organic and ammonia), and dissolved oxygen. The information below summarizes the results of the model simulations and conclusions from in-stream data. Lower & Middle River Des Peres Model calculations demonstrate that ammonia criteria are met 100 percent of the time during a typical year. While exceedances of dissolved oxygen criteria occur regularly in the Lower River Des Peres, the model indicates that removal of CSOs does not greatly increase the time of compliance. Most dissolved oxygen exceedances occur during wet weather, but some occur during dry weather as well, primarily during periods when backwater from high water levels in the Mississippi River reduce flow velocities and reaeration in the River Des Peres channel. Other factors influencing dissolved oxygen levels include plant photosynthesis and respiration, stream temperatures, stormwater discharges, and sediment oxygen demand. Compliance with the secondary contact recreation criteria in the typical year is not an issue, and complete removal of CSOs has a relatively minor effect on reducing the geometric mean bacteria densities. Upper River Des Peres Model calculations demonstrate that ammonia criteria are met 100 percent of the time during a typical year. Exceedances of dissolved oxygen criteria occur, partly as a result of photosynthesis-respiration, but also as a result of CSOs. Maline Creek Modeling demonstrates that ammonia criteria are met 100 percent of the time during a typical year. Exceedances of dissolved oxygen criteria occur regularly; however, removal of CSOs has no perceptible impact due to their small volume relative to upstream and stormwater sources. Compliance with the secondary contact recreation criteria in the CSO-impacted segment is not an issue, and complete removal of CSOs again has a relatively minor effect on reducing the geometric mean bacteria densities. Mississippi River Water quality data indicate that dissolved oxygen concentrations in the river are generally well above the 5 mg/l standard. Bacteria densities in the river are orders of magnitude less than bacteria in the other receiving streams and meet the secondary contact recreation standard. Page ES-5 February 2011

6 Alternatives Evaluation MSD used a multi-level screening process, depicted in Figure ES-3, to develop and evaluate various alternatives to control CSOs to meet the goals of the CSO Control Policy and improve water quality in the impacted waterways. LEVEL 1 SCREENING LEVEL 2 SCREENING LEVEL3 SCREENING SOURCE CONTROL TECHNOLOGIES COLLECTION SYSTEM CONTROLS STORAGE TECHNOLOGIES INTEGRATED CONTROL ALTERNATIVES SPECIFIC TO MSD S SYSTEM AND RECEIVING WATERS FEASIBLE AND COST-EFFECTIVE INTEGRATED CONTROL ALTERNATIVES SELECTED ALTERNATIVE TREATMENT TECHNOLOGIES 70+ TECHNOLOGIES 55 ALTERNATIVES 12 ALTERNATIVES 1 ALTERNATIVE FEASIBILITY Figure ES-3 Alternatives Evaluation Process COST COST- PERFORMANCE PUBLIC INPUT MSD began by evaluating a wide range of control technologies: Source Control Technologies those technologies that affect the quantity or quality of runoff prior to entering the collection system. Collection System Controls those technologies that affect CSO flows and loads once the runoff has entered the collection system. Storage Technologies those technologies that provide for storage of flows from the collection system for subsequent treatment after the storm is over and conveyance and treatment capacity have been restored. Treatment Technologies those technologies that provide for either local (at the CSO) or centralized treatment of CSO flows to reduce the pollutant loading to receiving waters. More than 70 CSO control technologies were evaluated (Level 1 Screening). Each technology was screened to determine its feasibility and applicability to the unique characteristics of MSD s combined sewer system. Feasible CSO control technologies were then assembled into 55 Integrated Control Alternatives specific to each receiving water. Each Integrated Control Alternative consists of one or more of the following components: Source Control Technologies that were determined to be applicable to all alternatives. Collection System Technologies that were determined to be applicable to all alternatives. Long-term CSO controls that have already been implemented by MSD or are currently being implemented by MSD that will continue to serve an important long-term role in controlling CSOs. These controls represent an investment of $0.6 billion that has already reduced annual CSO volumes by 38 percent. New long-term CSO controls necessary to meet the established CSO control goals. Page ES-6 February 2011

7 Each of the 55 Integrated Control Alternatives was then evaluated and screened to develop a short list of the most feasible and cost effective alternatives for further analysis (Level 2 Screening). Evaluation criteria included affordability, CSO flow/load reduction, constructability, expandability, operability, public acceptability, reuse of existing facilities, and infrastructure rehabilitation / upgrade opportunities. Twelve Integrated Control Alternatives remained after the Level 2 screening process. For each of these twelve alternatives, MSD: evaluated a range of sizes of the 12 Integrated Control Alternatives that would achieve 0, an average of 1 to 3, an average of 4 to 7, and an average of 8 to 12 overflow events per year; analyzed the impact that each of the 12 Integrated Control Alternatives is estimated to have on peak instantaneous and sustained flows to the Lemay and Bissell Point Treatment Plants; estimated project costs, including capital costs, annual operation and maintenance costs, and total present worth (life-cycle) costs; estimated the benefits arising from implementation; conducted cost-performance ( knee of the curve ) analyses comparing estimated costs to the estimated benefits; and involved its Stakeholder Advisory Committee and the public in reviewing the analysis results. This Level 3 screening process resulted in the identification of five CSO control scenarios that consist of combinations of the 12 Integrated Control Alternatives: Scenario 1 Complete elimination of CSOs Scenario 2 CSO control to the knee-of-the-curve on all CSOs Scenario 3 CSO control to the knee-of-the-curve on CSOs discharging to urban streams (e.g., Maline Creek, the River Des Peres and its tributaries), plus an enhanced green infrastructure program in areas with CSOs directly tributary to the Mississippi River Scenario 4 CSO control to a uniform minimum level of control (18 overflows per year) on all CSOs Scenario 5 CSOs to urban streams to receive a graduated level of control (higher control on smaller streams), plus an enhanced green infrastructure program in areas with CSOs directly tributary to the Mississippi River These scenarios were discussed with MSD s Stakeholder Advisory Committee that was created for the LTCP public participation program, and the general public. Scenario 3 was selected to form the basis of the CSO control measures for the LTCP. The selection was based on a number of factors including: Public and political acceptance of the proposed solutions, Total program cost and resulting user rates, Costs and benefits of existing controls, Costs versus benefits, Cascading effect of implementing controls, Water quality gains, Treatment plant impacts, and Technical feasibility. Page ES-7 February 2011

8 Figure ES-4 depicts the calculated annual system-wide overflow volume with each control scenario compared to the pre-control and current conditions. Figure ES-5 provides the same information for the urban streams only. Scenario 1 (complete sewer separation) is neither realistic nor affordable. Scenario 2 (uniform control everywhere) is significantly more expensive than Scenarios 3 and 5, and provides little added water quality benefit. Control Scenario 3 provides the maximum benefit on the urban streams, and the same system-wide benefit as Scenarios 4 and 5, at an affordable cost. 25 Annual CSO Volume (billion gallons) Pre-Control Modeled Conditions Scenario 5 Scenario 3 Scenario 4 Scenario 2 Scenario 1 Figure ES-4 Comparison of Scenarios System-Wide Benefits Annual CSO Volume (billion gallons) Scenario 1 Complete elimination Scenario 2 Knee-of-the-curve everywhere Scenario 3 Knee-of-the-curve on urban streams + enhanced green program on Mississippi Scenario 4 Uniform minimum Level of Control Scenario 5 Graduated control on urban streams + enhanced green program on Mississippi 0 Pre-Control Modeled Conditions Scenario 4 Scenario 5 Scenario 3 Scenario 2 Scenario 1 Figure ES-5 Comparison of Scenarios Urban Streams Page ES-8 February 2011

9 Public Involvement MSD conducted a focused public involvement program to engage the affected public in the abovedescribed decision making process to select the long-term CSO controls. The program included the following components: Face-to-face interviews with key stakeholders representing business, community, environmental, municipal, public health and regional planning organizations. These interviews were used to modify the public involvement program plan to make it more responsive to the public s interests and external realities. A Stakeholder Advisory Committee (SAC) comprising 12 municipal, environmental, regional, business and community representatives. The SAC reviewed program data and technical findings; increased community awareness of and support for the CSO control program; advanced MSD s understanding of their constituents concerns, issues, priorities and interests; and served as a sounding board and connection to the community at-large. Stakeholder and community presentations to a wide variety of business, community, environmental, legislative, municipal and professional groups. The presentations were educational in nature, intended to raise awareness of the CSO control program. Public open houses at 13 locations throughout MSD s service area. The open houses were designed to educate the public about CSOs and their impacts, review options for controlling CSOs, identify the public s preferred options and explore opportunities for additional action by MSD and the public in addressing the CSO issue. These public deliberation sessions allowed 451 members of the public to directly weigh in on the selection of CSO controls. A Clean Rivers Healthy Communities web site that provided the public with opportunities to learn more about the program, participate virtually in the public open houses, and leave feedback for the CSO control program. Outreach to the media, through such activities as tours and briefings, to aid their understanding of complex issues as they communicated with their audiences. Telephone surveys to gauge public understanding of the CSO issue. The input received from the public during these activities was used by MSD to help define the CSO control scenarios that were considered during the alternatives evaluation process, and to assist in selection of the preferred control option. Follow-up public open houses were conducted to present and discuss the selected control option with the community. MSD intends to continue its public involvement program throughout the LTCP approval and implementation process. Selected Plan Details MSD is committed to continue to improve water quality in the Mississippi River, Maline Creek, and the River Des Peres and its tributaries. The selected LTCP controls build upon MSD s previous investments in CSO control and provide for significant additional reductions in CSO volumes and pollutant loadings. The selected controls will also allow MSD the financial capability to maintain its existing infrastructure and tackle significant issues in its separate sewer systems. The selected LTCP consists of controlling CSOs to MSD s urban streams to the point where further expenditures yield significantly diminished returns (the knee-of-the-curve ), coupled with an enhanced green infrastructure program in areas with CSOs that discharge directly to the Mississippi River. Source controls and collection system controls common to all areas are also part of the selected plan, as are the CSO controls that MSD has already implemented during the planning period. Page ES-9 February 2011

10 The selected LTCP components are listed in Table ES-2 along with estimated total capital and total present worth costs. Costs for long-term CSO controls that have already been implemented by MSD, or are currently being implemented, are not included in the table. The estimated total capital cost of these completed and ongoing improvements is $634 million. Figure ES-6 depicts the locations of the principal new components. Cost Opinions ($million) 1 LTCP Component Total Present Capital Cost Worth System-wide Source Control Technologies Note 2 Note 2 Collection System Technologies Note 2 Note 2 Maline Creek Bissell Point Overflow Regulation System Note 2 Note 2 Sewer Separation of Outfalls 053 and 060 Note 2 Note 2 Treatment unit to treat overflows from Outfall 051 and storage tank to store overflows from Outfall Gingras Creek Separation of three storm sewers from combined sewer system and relocation of Outfall Upper River Des Peres Skinker-McCausland Tunnel to express convey separate sewer system flows around the combined sewer system Note 2 Note 2 Storage tunnel to store flows from CSO outfalls to the Upper River Des Peres River Des Peres Tributaries Sewer separation of 15 smaller CSOs Note 2 Note 2 Elimination of all CSO outfalls to tributaries, tunnel to store/convey flows to the River Des Peres channel Lower and Middle River Des Peres Lemay Overflow Regulation System Note 2 Note 2 Skinker-McCausland Tunnel to express convey separate sewer system flows around the combined sewer system Note 2 Note 2 Full utilization of excess primary treatment capacity at Lemay Treatment Plant Note 2 Note 2 Sewer separation of 5 smaller CSOs Note 2 Note 2 Repair of inflow to interceptor sewers under River Des Peres Note 2 Note 2 Upstream CSO controls (Upper River Des Peres) Note 3 Note 3 Flow storage in 29-ft horseshoe sewers under Forest Park and in new storage tunnel, 100 MGD treatment unit near Outfall 063, removal of 1,103 1,208 secondary treatment bottlenecks at WWTP Mississippi River Bissell Point Overflow Regulation System Note 2 Note 2 Separation of two major industrial sources Note 2 Note 2 Full utilization of excess primary treatment capacity, and maximizing flow pumped to the Bissell Point Treatment Plant Note 2 Note 2 Sewer separation for Outfall 055 Note 2 Note 2 Upstream CSO controls (Maline Creek, River Des Peres) Note 3 Note 3 Enhanced green infrastructure program Grand Total 1,819 2,001 Notes: 1. Costs updated to ENR Construction Cost Index of Costs for controls already implemented or currently being implemented are not included as LTCP future costs. 3. Costs for upstream CSO controls are reflected under the appropriate upstream components. Table ES-2 Selected Long-Term Control Plan Components Page ES-10 February 2011

11 Metropolitan St. Louis Sewer District Figure ES-6 Selected Long-Term Control Plan - Major Future Components The principal components of the control plan are described below. System-wide Controls System-wide source controls include green infrastructure, illicit connection control, stormwater detention for new developments, catch basin cleaning, solids/floatables control, illegal dumping control, hazardous waste collection, good housekeeping, street sweeping, construction erosion and waste control, litter control, industrial pretreatment program, stream teams, community clean-up programs, recycling programs, pet waste management, proper yard waste disposal, and the installation and maintenance of warning signage. System-wide collection system controls include diversion structure maintenance, outfall maintenance, sewer system cleaning and sewer separation for new developments or redevelopments. Maline Creek CSO Controls The CSO controls selected for Maline Creek are estimated to control overflows to a level of 4 overflows per year in the typical year. The controls include the following components: The existing Bissell Point Overflow Regulation System will continue to be operated to control the influence of Mississippi River stage on the capture of flows at Bissell Point Outfall 051 to Maline Creek. Infiltration and inflow (I/I) controls will be implemented in the separate sewer systems upstream of the Maline Drop Shaft as part of MSD s efforts to eliminate constructed SSOs. Reduced peak flows Page ES-11 February 2011

12 resulting from I/I control may allow for greater capture of wet weather flows from the combined sewer system. Bissell Point Outfalls 053 and 060 will be eliminated by sewer separation. A 1.0 million gallon storage facility will be constructed to control overflows from Bissell Point Outfall 052. Control features will include modifications to the existing drop shaft/diversion structure, flow screening facilities, an above- or below-grade storage tank, a tank dewatering pump station, and interconnecting piping. Combined sewage will be temporarily stored at the facility during a storm event until the north leg of the Bissell Point Interceptor Tunnel has capacity to convey the return flow to the Bissell Point Treatment Plant for secondary treatment. A 94 MGD treatment facility will be built to treat CSO flows from Bissell Point Outfall 051 prior to discharge to Maline Creek. Control features will include a modified diversion structure, pump station to the treatment facility, and Enhanced High Rate Clarification treatment unit(s) providing screening, the equivalent of primary treatment and disinfection to the design flows prior to discharge to Maline Creek. Gingras Creek CSO Controls The CSO controls selected for Gingras Creek will eliminate the occurrence of CSOs. The controls include the following components: Three large storm sewers will be disconnected from the existing combined sewer system and connected to a new separate storm sewer discharging to Gingras Creek. Bissell Point Outfall 059 will be eliminated. The existing 66-inch combined sewer will be extended to the Baden combined sewer system (Gingras Creek Branch of the Baden Trunk Sewer). Upper River Des Peres CSO Controls The CSO controls selected for the Upper River Des Peres are estimated to control overflows to a level of 4 overflows per year in the typical year. The controls include the following components: MSD will continue to operate and maintain the Skinker-McCausland Tunnel to express route separate sanitary flows around the combined portions of the Upper River Des Peres sewer system, thereby eliminating the overflow of this separate sanitary flow from the combined sewer system during wet weather. A 30 million gallon deep storage tunnel will be constructed to store flows from the 39 CSO outfalls to the Upper River Des Peres. The tunnel is estimated to be approximately 24 feet in diameter, extending approximately 9,000 feet from near Lemay Outfall 090 to a location near Outfall 064. The existing 39 CSO outfalls will be consolidated to approximately 4 or 5 drop shaft locations along the tunnel. A tunnel dewatering pump station will pump stored flow back to the Skinker-McCausland Tunnel and Lemay Treatment Plant for secondary treatment as capacity becomes available. River Des Peres Tributaries CSO Controls The CSO controls selected for the River Des Peres tributaries (Deer, Black, Hampton and Claytonia Creeks) are estimated to control overflows to a level of 4 overflows per year in the typical year. The controls include the following components: Fifteen small CSO outfalls will be eliminated by sewer separation. A tunnel, approximately 20 feet in diameter and 12,000 feet long, will convey all flows from the remaining CSOs to a single location on the River Des Peres main channel in the vicinity of its confluence with Deer Creek. Consequently, the CSO outfalls along the tributaries, remaining after the above-mentioned sewer separations are completed, will be eliminated. The tunnel size necessary for total flow conveyance is adequate to provide CSO flow storage to the desired level of control. The tunnel alignment will generally follow the creek alignment from the confluence of Claytonia and Hampton Creeks to the River Des Peres main channel. Approximately five or six drop shafts are Page ES-12 February 2011

13 anticipated to direct flow from shallow conveyance piping to the deep tunnel. A dewatering pump station at the tunnel s downstream end will pump stored flow from the tunnel to the Lemay Treatment Plant, where it will receive full secondary treatment, as conveyance and treatment capacity becomes available. Lower & Middle River Des Peres CSO Controls The CSO controls selected for Lower and Middle River Des Peres are estimated to control overflows to a level of 4 overflows per year in the typical year. The controls include the following components: The existing Lemay Overflow Regulation System will continue to be operated to control the influence of Mississippi River stage on the capture of flows at outfalls along the Lower and Middle River Des Peres. MSD will continue to operate and maintain the Skinker-McCausland Tunnel to express route separate sanitary flows around the combined portions of the Upper River Des Peres sewer system, thereby eliminating the overflow of this separate sanitary flow from Lemay Outfall 063 during wet weather. MSD will utilize excess primary treatment capacity at the Lemay Treatment Plant to maximize treatment during wet weather. Upon completion of influent pumping and ongoing plant outfall modifications, the expanded treatment plant will have the ability to treat 340 MGD through its preliminary and primary treatment facilities. Flow rates of up to 340 MGD will be pumped and treated during wet weather events. The current capacity of the secondary treatment facilities is 167 MGD. Five small CSO outfalls will be eliminated by sewer separation. MSD will correct the excessive inflow problem to the interceptor sewers beneath the Lower River Des Peres channel that has been hampering MSD s ability to maximize the capture of wet weather flows from its combined sewer system. These excessive inflows occur during periods of backwater due to high Mississippi River stage. CSO controls implemented on the Upper River Des Peres and River Des Peres tributaries will benefit the Lower and Middle River Des Peres by reducing overflow volumes and pollutant loadings. The existing dual 29-foot wide horseshoe sewers beneath Forest Park (immediately upstream of Lemay Outfall 063) will be utilized to store up to 25 million gallons of wet weather flow. This will be accomplished by the construction of a flow control gate at Outfall 063. A 100 MGD Enhanced High Rate Clarification treatment unit will be constructed adjacent to Outfall 063 to provide for the equivalent of primary treatment and disinfection of up to 100 MGD of flow from Outfall 063. Treated flow will be discharged to the Middle River Des Peres channel. A 206 million gallon deep storage tunnel will be constructed to store flows from the CSO outfalls to the Lower and Middle River Des Peres. The tunnel is estimated to be approximately 28 feet in diameter, extending approximately 47,400 feet from Outfall 063 to a location near the Lemay Treatment Plant. The existing CSO outfalls will be consolidated to approximately 14 drop shaft locations along the tunnel. A tunnel dewatering pump station will pump stored flow directly to the Lemay Treatment Plant for secondary treatment as capacity becomes available. Flow capacity bottlenecks that currently limit secondary treatment capacity at the Lemay Treatment Plant to 167 MGD will be removed. It is anticipated that secondary capacity can be increased to 210 MGD. Stress testing will be performed to determine maximum treatable flow rates for the plant. Mississippi River CSO Controls The CSO controls described above for the receiving waters that are tributary to the Mississippi River will complement the significant long-term controls already implemented on the Mississippi River outfalls. These controls, along with the enhanced green Page ES-13 February 2011

14 infrastructure program proposed by MSD, will provide meaningful reductions in overall CSO volumes and pollutant loadings to the Mississippi River. The existing Bissell Point and Lemay Overflow Regulation Systems will continue to be operated to control the influence of Mississippi River stage on the capture of flows at the CSO outfalls to the Mississippi River. Two significant industrial users currently have their wastewater discharges disconnected from the combined sewer system and connected directly to the Bissell Point Interceptor Tunnel. MSD will utilize excess primary treatment capacity at the Bissell Point Treatment Plant to maximize treatment during wet weather. The treatment plant has the ability to treat 350 MGD through its preliminary and primary treatment facilities. Flow rates of up to 350 MGD will be pumped and treated during wet weather events, except during extremely high river stage conditions, when the capacity of the effluent pump station limits total plant flow to approximately 250 MGD. The current capacity of the secondary treatment facilities is 250 MGD. Bissell Point Outfall 055 will be eliminated by sewer separation. In addition to the above-noted CSO long-term controls that have already been implemented, the CSO controls implemented along Maline Creek, and the River Des Peres and its tributaries will benefit the Mississippi River by significantly reducing CSO volumes and pollutant loadings. MSD will invest $100 million in an enhanced green infrastructure program focused on its combined sewer areas with CSOs that are directly tributary to the Mississippi River. The overall objective is to identify and implement projects and programs that will significantly reduce CSOs and provide additional environmental benefit. A program goal is to reduce CSO overflow volumes to the Mississippi River by 10 percent. This goal will be updated based upon the results of initial projects comprising the pilot phase of the program. MSD has limited direct control over the infrastructure and policies that impact the magnitude of storm runoff in the combined sewer areas. To address this challenge, MSD plans to work with local units of government, private developers, and other stakeholders to implement the program. It is anticipated that MSD s enhanced green infrastructure program will comprise the following types of activities: Community outreach and education programs. Partnering with the Land Reutilization Authority and the St. Louis Development Corporation to implement green infrastructure on to-be-developed properties in some of the most economicallydistressed portions of the City of St. Louis. Once the pilot program is complete, perform similar work with like entities in the economically-distressed portions of North St. Louis County located within the Bissell Point service area. Lot-scale and neighborhood-scale stormwater management projects that incorporate green infrastructure. Working with developers to encourage green infrastructure implementation in specific redevelopment opportunities. Support of rain barrel and rain garden implementation programs. LTCP Benefits and Water Quality Standards Review and Revision The selected CSO controls are intended to bring CSOs into compliance with technology-based and water quality-based requirements of the Clean Water Act and to minimize the impact of CSOs on water quality, aquatic biota and human health. Implementation of the selected LTCP will substantially reduce the occurrence and magnitude of CSOs to MSD s urban streams as well as significantly reduce CSO volumes and loadings to the Mississippi River. For the parameters of concern ammonia, bacteria and dissolved oxygen water quality data and water quality simulations indicate that, with the LTCP controls implemented: Page ES-14 February 2011

15 Ammonia criteria, acute and chronic, are met for all receiving waters. Geometric mean criteria for E. coli bacteria are met for all receiving waters. The dissolved oxygen criteria are met in the Mississippi River. Exceedances of water quality criteria for dissolved oxygen are predicted to occur in Maline Creek. CSOs, however, play a very small role, as their volume is very small compared to upstream and storm flows. Exceedances of water quality criteria for dissolved oxygen are predicted to occur in the River Des Peres, partially due to CSOs. Despite the significant reductions in pollutant loadings associated with the selected LTCP controls, these controls are expected to only slightly improve the percent compliance with dissolved oxygen criteria in the urban streams (Maline Creek and the River Des Peres). Even complete elimination of CSO and stormwater discharges would not significantly improve dissolved oxygen conditions. Other contributing factors to the problem include diurnal swings in dissolved oxygen due to plant photosynthesis-respiration, and backwater conditions caused by high Mississippi River stage. Because of these factors, a site-specific dissolved oxygen criterion for the River Des Peres and Maline Creek will be necessary. Preparation of the Use Attainability Analysis necessary to determine the highest attainable use should not delay agreement on the selected CSO controls because it is clear that even elimination of the CSOs would not address the stream impairments. Financial Impacts and Schedule MSD has evaluated the financial impacts of constructing and operating the improvements contemplated in its total Capital Improvement and Replacement Program (CIRP). The CIRP comprises not only the CSO controls described in this LTCP, but also the need to operate and maintain current assets, control wet weather flows in sanitary sewer systems, construct wastewater treatment plant improvements, and provide stormwater services. MSD s financial analysis is consistent with the principles of EPA s Guidance on Financial Capability Assessment and Schedule Development. The assessment is based on determining the amount of net revenues that may be generated under feasible rate and fee increase scenarios. The feasibility of these scenarios is based in part on current and projected burden of wastewater and stormwater service costs, and in part on the unique socio-economic attributes of MSD s service area. MSD has employed its cash flow forecasting model to determine the capital project financing capacity under a range of wastewater and stormwater rate slope scenarios and alternative configurations of the CIRP. The analyses were based on well documented information on the District s financial position, and several critical assumptions such as inflation rates, median household income (MHI) growth rate, and capital financing (bond) parameters. The resulting cash-flow projections have allowed MSD to determine the amount and pace of CIRP spending that can be financed within the District s capabilities. MSD s proposed 23-year baseline schedule for implementing CSO controls, together with other CIRP expenditures, represents an unprecedented capital investment for MSD s service area that will require substantial rate increases. These rate increases build the necessary revenue generation capacity for MSD to aggressively control CSOs and address other water quality issues (SSO control, wastewater treatment, and stormwater management). At the same time, these increases will elevate claims on ratepayer income already strained by recent economic decline, as shown in Figure ES-7. Page ES-15 February 2011

16 3.0% Residential Bill as % of MHI 2.5% 2.0% 1.5% 1.0% 0.5% 0.0% St. Louis County St. Louis City EPA High Burden Threshold Combined (Weighted Avg) Low Income Figure ES-7 Projected Typical Residential Bills for Proposed Capital Improvement and Replacement Program The projected rate increases place portions of the MSD ratepayer population at the threshold of High Burden while imposing potentially problematic burdens on low-income ratepayers throughout the District s service area. MSD s approach to financial capability assessment also contemplates mechanisms to assess and manage risk should significant adverse changes to its financial circumstances or other financial or budgetary issues arise. MSD will periodically update projected cash flows and estimated project costs. In the event that the funding level is significantly less than anticipated, or project costs are significantly higher than anticipated, MSD may propose adjustments to project scopes and/or timelines consistent with available funding levels and project costs. Post-Construction Compliance Monitoring Post-construction compliance monitoring will be performed to determine the effectiveness of the LTCP in meeting the plan s performance objectives, and to assess and document impacts on receiving waters resulting from implementation of the CSO control measures. Documentation of the monitoring results will be provided in annual progress reports that will summarize: Final design criteria and sizing of the CSO control program elements, CSO control measure performance (e.g., CSO activation and flow data), Rainfall data, Receiving water quality data, Progress in updating and calibrating/validating the hydraulic models, Status in achieving performance objectives based on continuous simulation modeling for the typical year, Identification of variances from expected results, and Proposed corrective action of LTCP program element(s), if needed. Page ES-16 February 2011