So What's the Problem?

Terre Haute, like many other Midwestern cities, has a problem with polluted waterways. Combined sewage overflows, failing septic systems, and urban stormwater runoff all contribute to sewage or untreated water flowing into the Wabash River, which can cause health problems and degrade the river water quality. As little as a quarter inch of rain can cause the combined sewer system to overflow to the river.

Why Are CSOs a Problem in Terre Haute?

View More

Click to enlarge area and view additional information

More than 130 years ago, Terre Haute built a sewer system to carry stormwater away from homes, businesses, and streets. They were generally directed to the west in order to discharge into the Wabash River. When indoor plumbing was developed, homes and businesses hooked their sanitary sewage lines to many of the storm sewers, making them combined sewers. In the 1960’s a large interceptor sewer was constructed along the river to the wastewater plant. This new sewer interceptor collected the sewage from the original sewers during dry weather and delivered it to the wastewater plant. However, when it rains or snow melts, combined sewers and this interceptor sewer are occasionally overloaded with incoming stormwater. When this happens, overflows are directed into the river through CSO diversion structures (see image), so the sewers do not back up into homes and basements. This is called a combined sewer overflow, or CSO. At the time they were built, CSOs were an acceptable way of handling excess flows, but their environmental impacts are now controlled under the present regulations of the federal Clean Water Act. Our combined sewers are located primarily within the city limits and older parts of the system, while other parts of the sanitary district are served by separate sanitary and storm sewers. However, due to the routing of the overall sewer system, sewage from many outlying areas eventually flows through the combined sewer system in the center of the city before flowing to the treatment plant.

Are CSOs a problem in other Cities?

Terre Haute is not alone in this problem. There are roughly 772 communities across the U.S. with aging combined sewer systems, according to the U.S. EPA. Over 100 of these communities are in Indiana, including Indianapolis.

Combined sewer systems are remnants of the country's early infrastructure and so are typically found in older communities. Many of these communities are faced with overflow problems similar to those experienced in Terre Haute, and they must develop plans to reduce these overflows under the Clean Water Act and subsequent adopted regulations.

Did You Know...
  • It is estimated that, on average, 284 million gallons of combined sewage discharge from the City's CSOs into the Wabash River on an annual basis.
  • Everything that enters our storm sewer system is discharged untreated into the waterbodies in our neighborhoods and town.


CSOs Impact
On Water Quality

Sewage, household, automobile and other wastes flowing into rivers and streams can cause:

  • A health hazard for people - combined sewage may contain harmful bacterial and viruses such as E.coli that can make people sick.
  • Damage to habitat and aquatic life - organic waste, like sewage, can contribute to impaired water quality by causing dissolved oxygen levels in our streams to fall.

Potential Health Threats

To alert the public to the potential health threat, the City has posted signs at CSO locations throughout the area advising citizens to avoid contact with the water during and after heavy rains.

  • It is recommended that people not swim, wade, boat, or fish for at least three days (72 hours) after a rainfall of a quarter inches or more or until high water levels in area rivers or streams return to normal.
  • The City also issues CSO advisories by electronic and media notifications. If you would like to receive a notification, sign up here.

Information About Our Waterways

Assessing the current water quality condition of the Wabash River provides a basis for understanding the impacts of the City’s CSOs on the river and for comparing the benefits of potential CSO controls. The City conducted a river sampling program to measure E. coli, Total Suspended Solids (TSS), Biological Oxygen Demand (BOD), and various metals in the summer of 1999. Another river sampling program was conducted from September 2001 through November 2001 to measure E. coli and dissolved oxygen (D.O.) A flow monitoring program was conducted by the City in the combined collection system in 2005 to better characterize the system and to have a robust dataset for calibrating and validating the CSS model. In 2007 the City conducted an extensive Wet Weather Sampling Program to characterize water quality in the Wabash River during periods when their CSOs are actively discharging.

The updated Wet Weather Sampling Program was conducted by LimnoTech in Fall 2007 for the City of Terre Haute and consisted of collecting water samples from the Wabash River, selected combined sewer overflows, and tributaries that receive storm water for E. coli . This is the most detailed water quality sampling conducted in this portion of the Wabash River. Six rounds of river sampling and two rounds of source sampling were conducted over a 72-hour period during three discrete storm events with varying characteristics.

Results from the wet weather sampling were used to characterize impacts of the City’s CSOs on river quality by monitoring the amount of E. coli found in the river over the course of the storm event. Major findings from the river sampling program include:

  • The City’s CSOs impact water quality in the Wabash River but impacts tend to last less than a day;
  • Local precipitation conditions do not significantly alter in-stream pollutant loads originating upstream of the City;
  • Upstream sources do not impact the City until one or two days after the local storm event; and,
  • The magnitude of the impact from the City’s CSOs on the river water quality is positively correlated with the magnitude of the rainfall.

Data analyses of the bacteriological conditions in the Wabash River were conducted using data collected by IDEM and the City between 1991 and 2009 during both dry and wet weather. Chemical data, which are snapshots of in-stream conditions in space and time, can be segregated into “wet” and “dry” categories so that distinctions in water quality attributed to wet weather sources, such as CSOs, can be identified, if such distinctions exist.

The data indicate that the Wabash River occasionally exceeds the State’s water quality standards and these exceedances occur more frequently during wet weather, suggesting that CSOs and other wet weather sources are contributing E. coli loads to the river. While the City’s CSOs have been identified as a source of bacteria, analyses of the available data show that state water quality standards are exceeded in both dry and wet weather and that exceedances are observed in portions of the watershed that do not receive any CSO discharges. These results suggest that there are multiple sources loading bacteria to the rivers. CSO discharges in wet weather appear to have no impact on either the dissolved oxygen or total suspended solids parameters of the receiving streams. In addition, the streams do not appear to be under any conditions of stress due to biodegradable organics or heavy metals.

  • Every year millions of gallons of combined sewage, stormwater, and debris overflow to the Wabash River.
  • The overflows cause increased E. coli readings and other pollution to the river.
  • The City of Terre Haute is undertaking a program to reduce the number of overflows to the river.
  • The goal of the CSO Reduction Program is to have a cleaner city, resulting in a cleaner river.