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Comprehensive Annual Financial Report


The maximum rate of flow that can be carried by sewers or received by a treatment plant, without causing an upset of the biological processes used in the treatment system.

Capital Improvement and Replacement Program

A plan for capital expenditures to be incurred each year over a fixed period of years to meet the capital needs to maintain or replace the sewer infrastructure or expand it to meet regulatory requirements. It sets forth each project’s expenditures and specifies the resources estimated to be available to finance the projected expenditures.

Catch Basin

A chamber or well used with storm or combined sewers as a means of removing grit which might otherwise enter and be deposited in sewers.


Hundred cubic feet: approximately 750 gallons.


Consent decree; between the United States, Missouri Coalition for the Environment, and the St. Louis Metropolitan Sewer District.


An improved, paved watercourse.


Capital Improvement Program


Cured-in-place-pipe, a construction method to rehabilitate a sewer pipe by lining it with a new pipe. This work does not require excavating the pipe and replacing it in total.


Capital Improvement and Replacement Program


Large, generally 100 gallons or more, device for storing captured stormwater. It can be built above or below ground from a variety of materials.

Cityshed Program

The portion of MSD’s Capital Improvement Program to mitigate the effect of wet weather surcharging and overland flooding of the combined sewer system.

Clean Water Act

Growing public awareness and concern for controlling water pollution led to enactment of the Federal Water Pollution Control Act Amendments of 1972.  As amended in 1977, this law became commonly known as the Clean Water Act. The Act established the basic structure for regulating discharges of pollutants into the waters of the United States. It gave the U.S. EPA the authority to implement pollution control programs such as setting wastewater standards for industry. The Clean Water Act also continued requirements to set water quality standards for all contaminants in surface waters. The Act made it unlawful for any person to discharge any pollutant from a point source into navigable waters, unless a permit was obtained under its provisions. It also funded the construction of sewage treatment plants under the construction grants program and recognized the need for planning to address the critical problems posed by nonpoint source pollution. Later amendments gave the U.S. EPA the authority to regulate stormwater discharges.


An opening, usually covered or capped, in a wastewater collection system used for inserting tools, rods or snakes while cleaning a pipeline or clearing a stoppage.

Cleanout Cap

A cap or lid used to close off a drain cleanout pipe.


Capacity Management Operations and Maintenance


Chemical Oxygen Demand: the quantity of oxygen utilized in the chemical oxidation of organic and inorganic matter as determined by Standard Methods and expressed in milligrams per liter.

Collection System

A network of pipes, manholes, cleanouts, traps, siphons, lift stations and other structures used to collect all wastewater, stormwater and combined wastewater of an area and transport it a treatment plant or disposal system. The collection system includes land, public sewer lines and appurtenances, pumping stations and general property.

Combined Sewers

A sewerage system that carries both wastewater and stormwater runoff.

Constructed Sanitary Sewer Overflow

An illegal pipe or conduit constructed within the wastewater sewer system to convey wastewater during wet weather into a stream.

Constructed Wetland

A man-made basin that contains slowly moving surface or subsurface water, a substance of soil, gravel rock, organic materials, etc., water-tolerant plants, and organisms similar to those found in natural wetlands. These engineered systems are designed to provide water quality improvements similar to their naturally occurring counterparts.

Also known as Rainscaping.


Introduction into water of any microorganisms, chemicals, toxic substances, wastes, or wastewater in a concentration that makes the water unfit for its next intended use.

Conveyance System

A series of sewers, manholes, pumping facilities and force mains that carry wastewater from residences, commercial establishments, and industrial plants terminating at a treatment plant.


Clean Rivers Healthy Communities; formerly the long term control plan communications effort.

Cross Connection

A connection between a storm drain system and a sanitary collection system. Less frequently used term to describe a connection between two sections of a collection system to handle anticipated overloads of one system.


Combined Sewer Overflows: discharges from a combined sewer in excess of the interceptor or regulator capacity, that are discharged into a receiving stream rather than going to a treatment plant.

Curb and Gutter

A curb and gutter system provides a defined drainage pathway along the edges of city streets or roadways for the flow of stormwater runoff.

Curb Cut

An area of curb that has been removed to allow an unobstructed pathway from the street level.  They are often used to redirect water from a traditional drainage way to a stormwater BMP.

Curb Inlet

A chamber or well, built at the curbline of a street, to admit gutter flow to the stormwater drainage system.


The occupant or owner of the property, or any person served by the System or discharging into the District’s system.

 Also known as User.


Clean Water Act:  Federal Water Pollution Control Act, commonly referred to as the Clean Water Act (CWA), is to restore and maintain the chemical, physical, and biological integrity of the nation's waters by preventing point and nonpoint pollution sources, providing assistance to publicly owned treatment works for the improvement of  wastewater treatment, and maintaining the integrity of wetlands.