The CSO Story
What is CSO?
A combined sewer overflow (CSO) is the discharge of combined sewage into a water body, such as a river, lake, or stream. Combined sewage is a combination of untreated sewage and storm water. Lansing's sewage collection system was designed to collect sewage from residences, commercial properties, and industrial facilities and transport it to the wastewater treatment plant (WWTP) for proper treatment during dry weather conditions. When it rains or snow melts, the water collected in catch basins, roof drains, yard drains and other structures discharges to the combined sewer where it mixes with sewage. When this large flow volume exceeds the capacity of the interceptor sewers and the WWTP, it is diverted through a CSO regulator (underground diversion chamber) directly to the Red Cedar River or Grand River. Each time there is a CSO event, combined sewage discharges into the rivers. Overflows of untreated sewage diminish water quality and threaten public health.
Please click here to download the CSO Brochure (PDF, 3962KB).
History
When many of Lansing's combined sewers were constructed, there was no WWTP. The original purpose of the combined sewer was to get both the sanitary and storm flows to the river, which carried the flow away from the City. As the Lansing developed, it became necessary to move the discharge of sewage further downstream, away from the City center. This was achieved by installing "sanitary" interceptor sewers along the river. Wherever a combined sewer connected to an interceptor sewer, a CSO regulator was installed. The regulator routed dry weather flow to the interceptor sewer to be discharged downstream, while excess wet weather flow overflowed to the river right in the City. In the late 1930's the WWTP was constructed on Sunset Avenue to treat sewage before it entered the Grand River, but the combined sewage was still discharged to the rivers upstream at the CSO regulator locations. The construction of combined sewers ended in the early 1950s, replaced by construction of separate sanitary and storm sewers.
Studies completed in the early 1980s identified 108 overflow structures in the collection system, including 62 in the combined sewer system, and 46 in the separate sewer/pump station system . From 1984–89 approximately 4,150 acres of combined sewer area were separated and 22 CSO overflow structures were eliminated. In addition, the known 42 separate sewer overflow points were eliminated with sewer system capacity improvements. The four pump stations with bypass structures were improved to deliver the flow to the WWTP without bypassing during wet weather events. This left 40 CSO regulators/diversions remaining in the 6,700-acre combined sewer system in the late 1980s.
In 1987, the Michigan Department of Environmental Quality (DEQ) issued a National Pollutant Discharge Elimination System (NPDES) Permit to the City of Lansing that required development of a long-term plan to eliminate the discharge of "raw" (untreated) sewage into the Grand and Red Cedar Rivers from the 40 remaining CSO locations. This action was taken to enforce Michigan PA 245 of 1929, now PA 451 of 1994. Options to achieve this requirement included separating the CSO system or providing adequate treatment for all flows discharged to the rivers to comply with Water Quality Standards.
The State of Michigan has been a leader in pursuing the removal of CSO flow to surface waters of the state. EPA, under the Clean Water Act, did not release its first requirements and policy on CSO controls until 1994. By having an approved long-term CSO Control plan in place with the DEQ prior to EPA rules, Lansing's plan was automatically accepted by EPA.
A final approvable report was due to the DEQ on or before December 1, 1991. The study and plan was completed and submitted on April 30, 1991. The Project Plan submitted by the City recommended sewer separation as the most cost effective alternative and requested a 30-year time frame to complete the project (1991 – 2020). Prior to final approval by the DEQ, the City moved forward with the first design projects in 1991 to remain on the schedule submitted in the plan. The DEQ approved the plan, including the 30-year implementation schedule, on April 1, 1992.
The implementation schedule for the project was incorporated into the 1992 NPDES Permit and subsequent permits issued in 1997 and 2002. It is anticipated that it will continue to be required with the re-issuance of the NPDES Permit in 2007.
Since 1991, the City has met all scheduled compliance dates in the NPDES Permit to complete the sewer separation project. As of 2006, the project has separated 50% of the area and reduced the number of CSO structures by 40%, leaving 24 to complete by 2020.
DEQ Role
The Michigan Department of Environmental Quality (DEQ, formerly Department of Natural Resources, DNR) is the regulatory agency in the State of Michigan responsible for water related issues including wastewater treatment plants, collection systems, combined sewers, and state water quality standards. DEQ has also been authorized by the U. S. Environmental Protection Agency (EPA) to manage the NPDES Permit program in Michigan. All reports, plans, design plans and specifications must be reviewed and approved by DEQ.
DEQ also has responsibility to manage the State Revolving Fund (SRF) low-interest loan program for water quality improvement projects in Michigan. They must approve project plans prior to the project being included in the priority list to receive SRF loans. Application forms must be completed, submitted and approved by DEQ prior to receiving authorization for the SRF loan. The SRF loan program has been one of the primary funding mechanisms for the City's long-term CSO control plan.
Solutions
The 1991 Project Plan recommended separation of the combined sewers by providing two pipes, one sanitary sewer and one storm sewer, as the most cost effective option to achieving compliance with the requirements of the NPDES Permit. The primary method of separating would be to install a new sanitary sewer and keep the existing sewer, if structurally sound, as the storm sewer.
Other options such as construction of retention/treatment basins, tunnels, or other facilities to store and/or treat the flows related to wet weather events were also evaluated. When the flows would exceed the storage capacity, treatment would be required before discharge to the rivers. These options were more costly than the selected separation option and would have still resulted in the discharge of partially treated sewage to the Grand and Red Cedar Rivers.
The selected option is re-evaluated every five years of the 30-year program to confirm that it remains the most cost effective and preferred solution as part of the Project Plan amendment. The most recent review, Lansing Combined Sewer Overflow Control Program Project Plan Amendment No. 3, was completed in June 2007. The final report continued to support separation as the best solution for the City of Lansing. In addition to the five year review process, in 1997-1998, an independent consultant was brought in to provide a peer review of the selected option. They also recommended separation as the recommended option.
Opportunities
The CSO Project is an opportunity for the City of Lansing and its residents to have a positive, lasting impact on the water quality of the Grand and Red Cedar Rivers for many decades to come. Not only by improving public health and the water quality of the rivers as they flow through the City, but for all downstream communities and four of the five Great Lakes.
Each property owner within the CSO service area also has the obligation to participate directly in the program by redirecting rainwater inflow sources away from the sanitary sewer system. Roof downspouts, yard drains, driveway drains and patio drains must be redirected from the property's service lead to help prevent overload of the separated sanitary sewer system. The new sanitary sewer system is not designed to convey storm water runoff.
The project also offers the City the opportunity to improve other aging infrastructure such as roads, curbs, water mains, natural gas lines and other utilities located within the publicly-owned right of way. By teaming with the Board of Water and Light, many old water mains and services are being replaced in conjunction with the sewer installation. The new pipes should provide long-term service ranging from 50 to 100 years, or more.
30-Year Schedule
The City's CSO Control Project Plan looked closely at the cost and time to complete the work. A 30-year implementation plan was requested from the DEQ due to the following considerations:
- Cost to the system users to pay for the project
- The need for continued access through downtown Lansing and the major corridors
Considerable CSO separation work had just been completed in the 1980s, already significantly reducing the combined sewer area served by CSO systems, the number of CSO outfalls, and installing reliable regulator devices to reduce the risk of dry weather bypasses
After lengthy negotiations with the DEQ, the City was granted a 30-year time frame, 1991–2020, to complete the project. Most communities were limited to a maximum of 15 years to complete their programs. Being proactive, cooperative, and responsive to the DEQ during the process and negotiations, as well as being one of the first to take action to develop a long-term plan had a positive influence on the approved time frame to complete the project.
Awards
The CSO Program and aspects of it have been formally recognized by others. Awards include:
- 2006 Project of the Year ($10,000,000 to $100,000,000) for the Capitol Loop Downtown Rehabilitation Project presented by the Michigan Chapter of the American Public Works Association.
- 1994 National Second Place Award for Combined Sewer Overflow Control Program Excellence, presented by the U.S. EPA. This award recognized the City of Lansing's work in the 1980s and the 1991 CSO Control Plan to eliminate CSOs.
- 1993 Crystal PACE Award for Community Relations for the CSO Control Project by the Public Relations Society of America, Central Michigan Chapter.
- 1986 National Grand Award from the American Council of Engineering Consultants (1985 Eminent Conceptor Award from ACEC Michigan) for the Design of System M and the Leaping Orifice for CSO Control.
