St Louis sanitary sewer overflows and combined sewer overflows control planning

This case study looks at fixing the fourth largest collection system in the United States.

An aerial view of the city of St Louis. It's water collection system is the fourth largest in the US.
An aerial view of the city of St Louis. It's water collection system is the fourth largest in the US.

Project details

Location: St Louis, Missouri, USA
Value: $4.7 billion
Date of completion: 2013 (planning), ongoing (implementation)
Duration: 10 years (planning), 23 years (implementation)
Client: Metropolitan St. Louis Sewer District (MSD)
Project manager: Jacobs

Challenge summary: Protecting public health by reducing overflows into streams and rivers, eliminating illegal discharge points in the collection system, and meeting the requirements of the EPA Consent Decree.

Challenge solution: $4.7 billion, 400+ project, 23-year long Capital Improvement Replacement Program.

Metropolitan St. Louis Sewer District SSO & CSO Control Planning Project Summary
Metropolitan St. Louis Sewer Disctrict SSO & CSO control planning project summary


The Metropolitan St. Louis Sewer District (MSD) provides wastewater and stormwater service to approximately 1.3 million people in a 525 square-mile service area which encompasses the City of St. Louis and most of St. Louis County, in Missouri. The collection system includes approximately 9,578 miles of sewers (3,028 miles of Stormwater sewers, 4,744 miles of Sanitary sewers, and 1,806 miles of Combined sewers), 294 pumping stations, and seven wastewater treatment plants, across 21 watersheds, making it the fourth largest collection system in the United States.

The Clean Water Act prohibits discharge of pollutants except as authorized by permit. MSD took a proactive approach to investigate their collection system. In 2003 MSD hired Jacobs as their Watershed Facility Planning consultant to develop a Sanitary Sewer Overflow (SSO) Control Master Plan and a Combined Sewer Overflow (CSO) Long-Term Control Plan. In 2012 MSD entered into a federal Consent Decree (settlement agreement under the Clean Water Act) with the United States Environmental Protection Agency (EPA) to make extensive improvements to its sewer systems.

Jacobs created client-consultant watershed teams, using over 360 team members in 39 engineering disciplines, to identify collection system problem areas, assess potential solutions, and develop capital projects to resolve known issues throughout the system. This resulted in a 23-year, $4.7-billion Capital Improvement and Replacement Program (CIRP) comprising over 400 projects scheduled which, in conjunction with existing MSD projects, complied with the Consent Decree and will facilitate the reduction of almost 13 billion gallons per year of overflows into streams and rivers, and eliminate more than 200 illegal discharge points within the sanitary sewer system.

Project Innovation

In 2003, MSD employed Jacobs as its planning consultant to provide services to augment, assist, and facilitate various tasks and activities necessary to refine and enhance its existing $3.7-billion CIRP aimed at protecting public health and complying with federal regulatory requirements, including combined and sanitary sewer overflow control. A fully integrated, hybrid team, utilizing MSD and Jacobs staff was used to execute the project.

Hybrid Team Structure
Hybrid team structure

The planning program was an extensive effort requiring contribution and coordination from all levels of the MSD organization as well as Jacobs. Jacobs worked closely with MSD's program manager and staff to develop the organizational structure necessary to deliver a successful program and provide flexibility as planning requirements and priorities changed throughout the 10-year planning period. Within this structure, Jacobs engaged in simultaneous work processes and provided multi-tasking teams and personnel.

To guide the hybrid team in carrying out planning activities, Jacobs worked with MSD to prepare a Technical Memorandum Manual (TMM) comprising 40 technical memorandums, which outlined the sequence of tasks and described the general procedures for accomplishing objectives of the program. The purpose of the TMM was to provide a common program reference for all team participants and to ensure consistency in the conduct and the results of the program across the District’s 20+ watersheds. This was achieved by documenting systematic processes integral to program success, while simultaneously providing flexible approaches that could be tailored to suit individual watersheds as necessary. To support and complement the TMM, more detailed Best Management Practice documents (BMPs) were also developed for major tasks. The TMM along with the BMPs ensured consistency and can be used by MSD if they decide to replicate any part of the program to meet future challenges.

SSO Control master plan tasks
SSO control master plan tasks

In executing the integrated planning program, key elements of Jacobs’ scope included: Collection System Characterization, Sewer System Evaluation Survey (SSES) – System Investigation, Hydraulic Modeling and Capacity Assessment, Data Analysis and Project Development, Public Involvement, Project Prioritization and Scheduling, and Master Plan Development. Several of these scope items involved innovations in, and/or early adoption and application of, leading-edge planning tools and methodologies.

SSES activities performed

For example, in executing the hydraulic modeling portion of the work, a unique aspect included development of a design storm tool specific to the St. Louis area to create synthetic design rain storms used by the models to simulate wet weather flow conditions across the collection system. Sixty-one years of local rainfall data, including a 5-year radar-rainfall database, was used to develop more realistic, less conservative design storms to accurately size projects, resulting in reduced costs.

The project also represented an early case of Geographic Information System (GIS) mapping used extensively to analyze large scale collection system data geospatially. For example, maps were efficiently created to identify existing sewer sizes, insurance claims, service requests, historical projects, flow meter data, and modeling results for a given area to quickly assess suspected problem areas.

Suspected Problem Area 'Cluster Map' example generated using GIS
Suspected problem area 'cluster map' exampled generated using GIS

From a methodology standpoint, Jacobs, together with MSD, advanced the planning paradigm shift from solving isolated, localized issues to employing a holistic watershed approach on a scale likely unequaled at the time. Comprehensive hydraulic modeling was performed Districtwide on a watershed basis. HYDRA software was used for the Sanitary Sewer System and XP-SWMM was used for the Combined Sewer System. Models were used to assess current infrastructure capacity needs as well as assess and optimize the performance of a range of proposed solutions.

Hydraulic Grade Line Graph example generated using data imported from HYDRA
Hydraulic grade line graph example using data imported from HYDRA

Contribution to the Engineering Profession and Public Perception

A key contribution of this project to the engineering profession has been to demonstrate a successful long-term, large-scale model of client/consultant partnership – working together as a fully integrated, hybrid, team in a real partnership to meet project goals and regulatory demands on time and within budget. Performed under a pending lawsuit from EPA, followed by Consent Decree negotiations and changing program direction, the project required an integrated and flexible organizational structure and planning approach, as well as an enhanced level of communication with MSD. It also required increased communications with the public.

The magnitude of capital needs identified by MSD demonstrates a problem facing many sewer districts and municipalities throughout the United States – aging infrastructure. Many sewer systems were originally constructed decades ago with the help of federal funds. Now the federal funds are gone and those original sewer systems are in need of repair. The cost burden is placed on the customers, and the price of water quality is high. Public education has become important. Unlike a bridge or a road, sewers are out of sight, thus more effort is required by utility districts to explain the problems being faced. Jacobs and MSD understood that the planning team and approach extended beyond just the engineers, technicians, and other employees assigned to the program. It also included educating and listening to the public.

Communication occurred with multiple audiences over the course of the program, including the public at large, the media, ratepayers, neighborhood groups, community associations, elected officials, municipalities, professional associations, and project-specific audiences. Outreach was achieved through multiple channels including speaking engagements, public receptions, billing inserts, regular briefings to various organizations on MSD activities, editorial board meetings, interactions with reporters, and proactive and reactive media activities.

MSD also launched the Project Clear initiative to better interface with, as well as inform, the public regarding ongoing implementation of its program.

Project Clear logo
Project Clear

Social, Economic, and Sustainable Development

MSD has a responsibility to protect public health and safety. Social issues were addressed by providing all stakeholders improved water quality in the surrounding streams and rivers. The SSO and CSO programs establish enhanced levels of service by eliminating sanitary discharges to local waterways and significantly reducing CSO volumes leaving the collection system. Additionally, the CSO plan included a public involvement component where stakeholders had input on the selection of CSO controls.

As a public agency, MSD has a duty to its ratepayers to conduct business in an economically judicious manner. Cost-effective analyses, using life-cycle cost comparisons were routinely performed, assuring low costs for ratepayers. Triple bottom line assessments, which included not only economic impacts but social and environmental impacts, were formally documented for all watershed-wide solutions. The CSO Long-Term Control Plan also included an affordability study. Additionally, cost savings were identified through Jacobs’ proprietary ‘Jacobs Value Plus’ system. More than $120 million in cost savings (more than double the fee for the project) were applied over the course of the project.

The CSO Long-Term Control Plan addressed inclusion of sustainable green infrastructure solutions primarily to areas tributary to the Mississippi River where extensive redevelopment is forecast. The team identified and recommended $100 million in green infrastructure practices in the CSO Long-Term Control Plan, including green roofs, bioretention, green streets, green parking retrofits, rain barrels, permeable pavement, and site-scale and neighborhood-scale stormwater retrofitting.


MSD owns and operates a large, complex wastewater and stormwater collection system. It provides service to approximately 1.3 million people in a 525-square-mile area encompassing the City of St. Louis and most of St. Louis County (88 different municipalities). According to a National Association of Clean Water Agencies membership survey, the District has the fourth largest collection system in the United States based on miles of wastewater sewer infrastructure. Most of the District’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. To add to the complexity, at the outset of the program in 2003, the District had a significant volume of Combined Sewer Overflows and 305 constructed Sanitary Sewer Overflows with goals to reduce CSO volume discharges from the collection system and to eliminate all constructed SSOs.

MSD’s jurisdictional area is divided into five major Wastewater Treatment Facility (WWTF) Service Areas: Bissell Point, Coldwater Creek, Lemay, Lower Meramec, and Missouri River. The Bissell Point and Lemay Service Areas contain both Sanitary and Combined Sewer Systems, while the District’s other service areas are served by Sanitary Sewer Systems. The District’s five Service Areas are further subdivided into 21 predominately Sanitary Sewer System watersheds.

MSD’s combined systems in the Lemay and Bissell Point Service Areas comprise 51 citysheds. MSD’s watersheds and citysheds are diverse. Each has unique features and challenges. Some contain Combined sewers along with Sanitary and Storm sewers, while others utilize only Sanitary and Storm sewers. Some have no pump stations while others have many. Slopes, geology, and land use, as well as age, size, and construction materials of the sewers all combine to create watershed differences that required site-specific considerations during planning and development of solutions.

Due to the tremendous amount of data compiled for the project, multiple databases were established to organize the latest information, and a SharePoint collaboration website was developed for project coordination.

Project successes

The SSO Control Master Plan was submitted before the Consent Decree deadline, and the 32 documents comprising the Master Plan were approved with minimal conditions by the EPA. After a negotiation period, an updated SSO Control Master Plan was submitted to the EPA which outlined all of the conditions of approval. MSD’s SSO Control Master Plan met the Consent Decree requirements.

The revised CSO Long-Term Control Plan was submitted on time and was approved by the Missouri Department of Natural Resources (MDNR). The report met the requirements of EPA’s 1994 CSO Control Policy as well as Missouri State Operating permits for the Lemay and Bissell Point WWTFs.

A Master Schedule was developed by Jacobs to logically sequence the projects to meet Consent Decree requirements. The schedule and associated cash flow was used by MSD to develop their 5-year Capital Improvements and Replacement Program, which they use to hire design consultants and contractors to implement the Consent Decree projects.

master schedule
Master Schedule example (p1 of 154)


The project involved over 10 years of comprehensive planning, resulting in an SSO Control Plan and Master Schedule and a CSO Long-Term Control Plan which provide MSD the framework to implement sequenced capital projects over a 23-year Consent Decree period. MSD’s Consent Decree program is one of the largest in the United States. The sheer size of the project required a large staff to execute the work and controls were needed to effectively manage resources to ensure consistency with respect to processes and procedures. Major tasks included:

  • Team Management – organization, communication, Technical Memorandum Manual, Best Management Practices
  • System Characterization – data collection and analysis, problem identification
  • Sewer System Evaluation Survey (SSES) – system investigation, flow and rainfall monitoring, smoke testing, dye tracing, closed circuit television (CCTV)
  • Hydraulic Modeling and Capacity Assessment – model updates, design storm tool, existing and future scenarios
  • Data Analysis and Project Development – integrated planning approach to project alternatives, Capacity, Management, Operation, and Maintenance (CMOM) Adaptive Management, cost estimates, prioritization, scheduling
  • Master Plans

The project was a success, having met regulatory deadlines and requirements. In addition, capital program costs and planning costs were below original estimates. Planning procedures and tools developed over the course of the project are now in use by MSD as they continue to plan for the future.

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