Glossary

A receptacle designed to collect surface or stormwater from an open area.

Wastewater or stormwater which is unable to drain and flow properly through sewers due to a blockage or capacity limitation, or overcharging.

Post construction, natural and engineered systems that control the quality, rate, and volume of stormwater runoff from developed areas. Examples of BMP systems include rain gardens, bioretention, pervious pavements, green roofs, rainwater harvesting systems, wet ponds, and constructed wetlands.

The process of collecting stormwater in a treatment area consisting of soil and plant materials to facilitate infiltration and remove sediment and other contaminants through physical, chemical, and biological processes. Used as the technical term for a rain garden that meets regulatory criteria as a stormwater best management practice.

A shallow depression in the landscape that is designed to capture and infiltrate stormwater runoff in a short period of time (typically 12 to 48 hours) Also known as "bioretention area," "basin," or "rain garden"

Partial or complete interruption of flow as a result of some obstruction in a sewer. Also referred to as a stoppage.

Biochemical Oxygen Demand: the quantity of oxygen utilized in the biochemical oxidation of organic matter in five days as determined by Standard Methods and expressed in milligrams per liter.

A fracture or opening in a pipe, manhole or other structure due to structural failure and/or structural defect.

A vegetated area between a waterbody and adjacent land practices such as farming or development.  Buffers are designed to provide soil stability, slow the flow of runoff into the waterbody, and improve water quality by filtering pollutants from the adjacent land.

A pipe, valve, gate, weir, trench or other device designed to permit all or part of a wastewater flow to be diverted from usual channels or flow. Sometimes refers to a special line which carries the flow around a facility or device that needs maintenance or repair.

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.

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.

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.

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

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.

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.

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.

A sewerage system that carries both wastewater and stormwater runoff.

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

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.

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.

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.

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

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.

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.

Where an underground drainpipe exits from below ground and discharges to the soil surface or a waterbody.  It also describes the process of uncovering or exposing some or all of the water flow from a previously covered stream, river, or drainage system.

The delay or holding of the flow of water and water-carried wastes in a pipe system. This can be caused by a restriction in the pipe, a stoppage or a dip. Detention also means the time water is held or stored in a basin or a wet well.

Permit granted by the Missouri department of natural resources allowing the discharge of pollutants into a body of water. The point source must meet technology based limitations, and conform to specific water quality standards established for the receiving waters.

Refers to The Metropolitan St. Louis Sewer District or MSD. The District is organized pursuant to Article VI, Section 30 of the Missouri State Constitution that empowers the people in the City of St. Louis and St. Louis County “to establish a metropolitan district for functional administration of services common to the area.”

Department of Natural Resources: a Missouri state government agency responsible for the administration and enforcement of state water pollution control policies and laws.

The process of separating roof downspouts from the home’s lateral line, and thus the sewer system, redirecting roof runoff onto pervious surfaces, most commonly a lawn.

A person trained and licensed to build or repair drains.

Any system of artificially constructed drains, including open channels and separate stormwater sewers used to convey stormwater, surface water or groundwater, either continuously or intermittently to natural watercourses.

Discharges from a wastewater system in dry weather into a receiving stream rather than a treatment plant, usually as a result of a blockage or break in the system. Also called a non-capacity-related SSO.

Eco roofs absorb and filter rainwater, provide building insulation, enhance roof lifespan, moderate roof deck temperatures, improve heating and cooling system efficiency, and add amenity value for urban rooftop views and spaces. Also known as Green Roof and Vegetated Roof.

Wastewater or other liquid – raw/untreated, partially or completely treated – flowing from a reservoir, basin, treatment process, or treatment plant.

A structure that forms the bank of a pond, foundation of a road, or other similar structures. It is typically made from earth, gravel, or similar materials.

Soil or growing media that has been formulated with specific components for a specific purpose or application. For example, an engineered soil for a rain garden may contain native soil from the site mixed with compost and sand to improve drainage and plant growth.

U.S. Environmental Protection Agency: a federal agency that is responsible for the administration and enforcement of national water pollution control policies and laws. The EPA provides federal grant funds to local governments for wastewater treatment under the provisions of the EPA Construction Grants Program.

Removal of soil particles by wind and water. Often the eroded debris (silt or sediment) becomes a pollutant via stormwater runoff. Erosion occurs naturally but can be intensified by human activities such as farming, development, road-building, and timber harvesting.

Commonly found food items such as meat, fish, butter, and cooking oil, gravy, sauces, mayonnaise, salad dressing, syrup, batter, cheese, and food scraps. Also known as FOG.

Vegetated areas used to reduce stormwater runoff velocity, filter out pollutants, and enhance infiltration. A filter strip is often used around the perimeter of a rain garden or along a stream channel.

First flush is the concept that runoff water from the first portion of rainfall in a storm event is the most contaminated with pollutants, typically considered from the first ½ to 1 inch of rainfall. This is especially true when rainfall has not occurred for a long period of time.

The volume of effluent expected to enter a treatment system over a given time period. Treatment systems are designed based upon estimates of peak and average flow for different segments of the system.

Commonly found food items such as meat, fish, butter, and cooking oil, gravy, sauces, mayonnaise, salad dressing, syrup, batter, cheese, and food scraps. Also known as Fats, Oils and Grease.

A force main sewer is a sewer line through which wastewater is propelled by the force of pump stations located along the path of the sewer.

Fiscal year

A small storage device that collects stormwater usually from a roof surface. Also known as a Rain Barrel.

Green Infrastructure; MSD green infrastructure initiatives are referred to as rainscaping.

When referring to construction sites, it’s the changing of the existing ground surface to desired slopes, elevations, and forms. It’s used to direct and manage stormwater runoff, create accessible areas for buildings, automobiles, and people, and enhance landscape space definition and aesthetics.

Wastewater from showers, baths, washing machines, and sinks other than kitchen sinks.

Green roofs absorb and filter rainwater, provide building insulation, enhance roof lifespan, moderate roof deck temperatures, improve heating and cooling system efficiency, and add amenity value for urban rooftop views and spaces. Also known as Eco Roof and Vegetated Roof.

Water that flows below the ground surface through saturated soil, glacial deposits, or rock.

The man-made features of a landscape constructed from concrete, masonry, wood, or other non-plant materials. This may include streets, sidewalks, patios, decks, etc.

Common everyday products that people use in and around their homes - including paint, paint thinner, herbicides, and pesticides - that can be hazardous if not properly disposed.

A graphical representation of water flow rate as a function of time. Hydrographs are used to describe water flow in streams, rivers, pipes, or other means of conveyance.

The science of hydrologic cycle is addressing the properties, distribution, and circulation of water across the landscape, through the ground, and into the atmosphere.

Areas of the land surface that by man's action become blocked or sealed from rainfall causing runoff in excess of the natural rain water runoff of vegetated areas. Examples are parking lots and rooftops.

A system for assessing fees for stormwater runoff conveyances and controls, and the operation and maintenance of same based upon the amount of impervious area on the rate payer's property.

The characteristic of a material which prevents the infiltration or passage of liquid through it. This may apply to roads, streets, parking lots, rooftops and sidewalks.

The seepage of groundwater into a sewer system, including service connections. Seepage frequently occurs through defective or cracked pipes, pipe joints, connections or manhole walls.

A shallow impoundment designed to infiltrate stormwater runoff into the soil. Infiltration basins do not release water except by infiltration, evaporation, or emergency overflow.

Rain water discharged into a wastewater sewer system and service connections from such sources as, but not limited to, downspouts, cellars, yard and area drains, foundation drains, cooling water discharges, drains from springs and swampy areas, around manhole covers or through holes in the covers, cross connections from storm and combined sewer systems, catch basins, stormwater, surface runoff, street wash waters or drainage. Inflow differs from infiltration in that it is a direct discharge into the sewer rather than a leak in the sewer itself.

Refers collectively to public works such as electrical and water distribution systems; streets, roads, bridges, and other components of the transportation system; stormwater collection and conveyance systems; and other constructed components that are required for an economy to function.

• When used in the context of stormwater management, “green infrastructure” or rainscaping ,refers to the use of soil, plants, and other natural features that capture precipitation and use it on-site or allow it to infiltrate. Green infrastructure/rainscaping varies in scale from preserved and restored natural landscape features (such as forests, floodplains, and wetlands) that manage and filter significant stormwater quantities to smaller scale practices including rain gardens, porous pavement, and green roofs. Green infrastructure/rainscaping is designed to mimic natural processes.
• “Gray infrastructure” refers to all components in traditional systems used to collect and convey stormwater runoff, such as curbs and gutters, storm drains, culverts, and others. This name is derived from the use of concrete to manufacture many of these components.

A surface connection to a storm or combined sewer pipe. A chamber for collecting stormwater with no well below the outlet pipe for collecting grit. Often connected to a catch basin or a basin manhole/cleanout manhole with a grit chamber.

A sewer that receives flow from a number of other large sewers or outlets and conducts the waters to a point for treatment or disposal.  Also referred to as an interceptor.

A sewer installed to connect two separate sewers. If one sewer becomes blocked, wastewater can back up and flow through the interconnector to the other sewer.

The lowest elevation of a pipe, pond, or drainage facility where water is designed to flow out.

The private portion of the sewer lying within a public street or easement connecting a building sewer service to the main sewer.

A wastewater pumping station that lifts the wastewater to a higher elevation when continuing the sewer at reasonable slopes would involve excessive depths of trench. Also, an installation of pumps that raise wastewater from areas too low to drain into available sewers. Also known as Pump Station.

Litter is any solid waste object, disposable item or resource, that can be held or carried in a person's hand that is left behind or placed in an inappropriate location. Any such material or item disposed of in an inappropriate manner is to be regarded as litter - the end outcome of an environmentally undesirable disposal action.

Lower-Middle River Des Peres

A land development approach that emphasizes site design and planning techniques that mimic the natural infiltration-based hydrology of the historic landscape. LID techniques generally manage stormwater by retaining and infiltrating runoff on-site.

Land Reutilization Authority, part of St. Louis Development Corporation

Long-term control plan

An opening in a sewer provided for the purpose of permitting operators or equipment to enter or leave a sewer. Also referred to as an access hole or maintenance hole.

Missouri Coalition for the Environment

Missouri Department of Natural Resources

Made out of sand, peat, shredded tires, foam, crushed glass, geo-textile fabric, or other material, and is used to remove solids and certain other contaminants from stormwater.

All property connected to an approved water meter which is:

1. Used only for human residency and consists of two or more dwelling units connected to a single approved water meter; or
2. Used for commercial or industrial purposes and connected to an approved water meter(s).

All property connected to an approved water meter through which the amount of water usage is measured.

Property used only for human residency, which consists of a single dwelling unit which is connected to an approved water meter which serves only such unit.

Milligrams per liter, commonly used to report results of laboratory analysis of wastewater samples and used as a parameter for wastewater extra strength user charge rate.

Million gallons per day: standard measure of wastewater flow through treatment plants.

Metropolitan St. Louis Sewer District

National Association of Clean Water Agencies

Plants which occurred in an area before disturbance by humans.

A grassed, wooded or vegetative strip that acts as a filter for the runoff before the water enters a stream.

Discharges from a wastewater system in dry weather into a receiving stream rather than a treatment plant, usually as a result of a blockage or break in the system. Also known as a Dry Weather Overflow.

Pollution which does not enter the water from any discernible, confined and discrete conveyance source but rather wash off, run off or seep from broad areas of land.

National Pollutant Discharge Elimination System

Overflow Regulation System: the District's O.R.S. is focused on the facilities that evolved from the former direct discharges of sewage from trunk sewers into the Mississippi River. The system now includes the management, operation, maintenance and improvements to the integrated trunk sewer outfalls, riverfront interceptors, interceptor pump stations and flood protection facilities. The goal of the O.R.S. is to capture the maximum amount of sewage and wastewaters and convey these to wastewater treatment plants at Bissell Point and Lemay.

Any solid object in or protruding into a wastewater flow in a collection line that prevents a smooth or even passage of the wastewater.

Operation Maintenance Construction Improvement district; funds generated by tax payments in certain districts can be used for capital improvements in those districts; funds can be used for capital project or maintenance within that specific district where the tax was collected.

Downstream opening or discharge end of a pipe, culvert, or canal.

Water flow over a surface at a uniform depth. Also known as Sheet Flow.

The percentage of a given area that will not allow water to infiltrate. The greater the percentage of impervious cover, the more runoff that will occur.

The flow of water within the soil profile once it has moved through the soil surface.

Includes several methods and materials, such as blocks, concrete and asphalt, that allow water and air to move through the pavement and into the underlying soil. Also known as Pervious Pavement or Porous Pavement.

Anyone that holds a permit from an issuing agency. An industrial user required to maintain an industrial waste permit, issued by MSD, due to the quality or quantity of their wastewater or point of discharge into the MSD sewer system.

Includes several methods and materials, such as blocks, concrete and asphalt, that allow water and air to move through the pavement and into the underlying soil. Also known as Permeable Pavement or Porous Pavement.

Any discernible, confined, and discrete conveyance, including but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, vessel, or other floating craft from which pollutants are or may be discharged. Also known as Point Source.

Any discernible, confined, and discrete conveyance, including but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, vessel, or other floating craft from which pollutants are or may be discharged. Also known as Point of Discharge.

Pollution that enters the environment from a single point such as a factory, an oil or chemical spill, a municipal wastewater treatment plant, or a stormwater discharge pipe.

Any substance which, alone or in combination with other substances, if discharged to waters of the State in sufficient quantities, causes or is reasonably certain to cause any alteration of the physical, chemical or biological properties of such waters; or to create a nuisance; or to render such waters harmful, detrimental or injurious to public health, safety or welfare, or to domestic, industrial, agricultural, recreational, or other legitimate beneficial uses or to any organism, aquatic life, plant or animal.

Annual report designed to provide an overview of MDS's work and summary financial information during the fiscal year from July 1 - June 30, using non-technical language.

Includes several methods and materials, such as blocks, concrete and asphalt, that allow water and air to move through the pavement and into the underlying soil. Also known as Permeable Pavement or Pervious Pavement.

Publicly owned treatment works

MSD Project Clear is a long-term initiative to improve water quality and alleviate many wastewater concerns in the St. Louis region.  It will invest billions of dollars over a generation in planning, designing, and building community rainscaping, system improvements, and through an ambitious program of maintenance and repair.

Installation of pumps to lift wastewater to a higher elevation in places where flat land would require excessively deep sewer trenches. Also used to raise wastewater or stormwater from areas too low to drain into available collection lines. Also known as Lift Station.

A small storage device that collects stormwater usually from a roof surface. Also known as a Garden Barrel.

A planted depression or a hole that allows rainwater runoff from impervious urban areas, like roofs, driveways, walkways, parking lots, and compacted lawn areas, the opportunity to be absorbed.

MSD's Green Infrastructure initiatives - combining plantings, water features, and other activities that manage stormwater as close as possible to where it falls; slowing it down so it can be absorbed by the soil and/or plants. Also known as Constructed Wetland.

The collection or capture of rainwater on-site, rather than allowing it to run off.

Customer

Plant influent or wastewater before any treatment.

Bodies of water or surface water systems that receive water from upstream sources.

The part of the precipitation falling on a drainage area which does not escape as surface stream flow. It is the difference between total precipitation and total runoff during the period, and surface or underground storage onsite.

A stormwater control structure with a permanent pool of water into which storm runoff is directed. Runoff from each storm is retained, allowing suspended sediment particles and associated pollutants to settle out. Water in the basin infiltrates or is displaced by runoff from a subsequent storm.

Techniques that hold or retain runoff water, allowing it to infiltrate, evaporate, and/or be used on-site in order to reduce off-site transportation of runoff and improve water quality.

Right of way

Excess rainfall, snowmelt, or irrigation water that flows over the surface of the land. It will eventually infiltrate to the ground, evaporate, or flow into a storm drain system, stream, river, lake, or other waterbody.

Overflow of sanitary sewage, mixed with stormwater, to a stream, from the separate sanitary sewer system in times of wet weather due to the entry of extraneous water into the System. These wet weather overflows occurs when the sewers become hydraulically overloaded. By-passes are usually designed and are used to prevent back-ups into basements. Dry weather overflows occur form maintenance-related reasons, such as a blockage or pipe failure.

The sewer system that caries liquid and wastewater from residences, commercial buildings, industrial plants and institutions, together with minor quantities of ground, storm and surface waters that are not admitted intentionally.

A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated. Usually the process follows primary treatment by sedimentation. The process commonly is a type of biological treatment process followed by secondary clarifiers that allow the solids to settle out from the water being treated.

Supplemental Environmental Project; Under the terms of the Consent Decree, MSD implemented a Sewer Connection & Septic Tank Closure Program for low income residents. Funding for the program is now completed.

Sewers that carry only wastewater or only carry stormwater. The separate sanitary sewers are ultimately connected to a treatment plant. The separate storm sewers ultimately discharge directly to a stream.

All of St. Louis City and 90% of St. Louis County, with Highway 109 as general western boundary and the three major rivers: Missouri, Mississippi, and Meramec as boundaries.

A sewer pipe to which building laterals are connected. Also called a collection main.

A supplemental environmental project required by the Consent Decree to connect low income residents’ homes that are on septic tanks to the MSD sewer system.

A sewer pipe to which building laterals are connected. Also called a collection main.

A comprehensive term that includes facilities collecting, pumping, treating and disposing of wastewater.

Water flow over a surface at a uniform depth. Also known as Overland Flow.

The solids removed from sewage during wastewater treatment.

The purposeful, systematic control of the generation, storage, collection, transport, processing, and disposal of sludge.

Surface runoff produced from melting snow.

Include any material added to soil to improve its physical, chemical, biological, or structural properties or to provide enhanced plant growth. Improved permeability, infiltration, drainage, structure, or nutrient availability may all be goals of using soil amendments.

Sewer system evaluation survey

A separate pipe, conduit or conveyance that carries stormwater runoff and discharges it into streams.

Any water resulting from precipitation that may or may not be mixed with an accumulation of dirt, soil, and other debris or substances collected from the surface on which such precipitation falls or flows.

The management of stormwater on- or off-site, including detention, retention, infiltration, or use.

The portion of rainfall, melted snow or irrigation water that flows across ground surfaces and eventually is returned to streams. Runoff can pick up pollutants from the air or land and carry them to the receiving waters.

The user charge to generate the revenue to operate and maintain the stormwater system.

A pump used to remove water that has accumulated in a water collecting sump basin, commonly found in the basement of homes.

The additional charge for the treatment of wastes containing suspended solids, biochemical oxygen demand or chemical oxygen demand exceeding normal wastewater strengths, for commercial customers.

A broad, shallow, gently sloped channel for conveying stormwater runoff. It may be lined with vegetation, compost, riprap, or other material and is designed to slow runoff velocity, trap particulates, and promote infiltration. Vegetated swales are often referred to as bioswales, enhanced swales, or water quality swales.

• Dry swale (bioswale)—incorporates additional elements in the design. Water treatment is aided by a soil bed (natural or amended) with an underdrain system typically composed of a perforated pipe surrounded by gravel.
• Wet swale—temporarily retains stormwater runoff, but unlike the dry swale, lacks an underdrain system. The wet swale is marsh-like and supports wetland vegetation that is adaptable to variable moisture conditions.

The entire sewer and drainage system owned and operated by the District for the collection, storage, handling, and treatment of wastewater, for the collection, storage, handling and treatment of stormwater, and combined sewers for the collection, storage, treatment and handling of wastewater and stormwater to serve the needs of the District and its customers.

Tunnel boring machine.

A calculation of the maximum amount of a pollutant or pollutants that a waterbody can receive and still meet established water quality standards.  These standards are dependent on the intended use of the waterbody such as drinking, swimming, or fishing.

Any substance whether gaseous, liquid or solid which, when discharged to a wastewater system watercourse in sufficient quantities, interferes with or passes through any wastewater treatment process, or constitutes a hazard to human beings, animal life, plant life, or inhibits aquatic life.

Containers typically installed beneath street or sidewalk level in which trees are planted. Runoff is directed into the tree box where it is filtered by soil and vegetation and then discharged into a storm drain system. This improves the water quality and delays the peak flow of water entering the storm drain system.

A sewer that receives wastewater from many tributary branches and sewers lines and serves as an outlet for a large territory or is used to feed an intercepting sewer.

A perforated or slotted pipe beneath a constructed soil bed that removes excess water from the bed.

Usually consists of vaults or piping systems used to store stormwater to eventually infiltrate or be used for irrigation or domestic purposes. This is an alternative to storage aboveground such as in a retention pond. Underground detention is sometimes constructed beneath permeable pavement.

Property used only for human residency, which is not metered residential property.

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

The major charges established by the District; wastewater user charge and stormwater service charge.

Vegetated roofs absorb and filter rainwater, provide building insulation, enhance roof lifespan, moderate roof deck temperatures, improve heating and cooling system efficiency, and add amenity value for urban rooftop views and spaces. Also known as Eco Roof and Green Roof.

Wastewater charge applied to each customer’s contributed wastewater volume. It includes both OM&R and capital costs components.

Sludge that has been aerated and subjected to bacterial action, used to remove organic matter in raw sewage during secondary waste treatment.

Permit issued to allow, with certain conditions, waste discharge into the System. This includes discharge of hauled waste.

Soiled water from homes, businesses and other buildings destined for treatment plants. Water in the combined sewer system becomes wastewater even when a mix of stormwater and wastewater.

An arrangement of pipes, equipment, devices, tanks and structures for treating wastewater and industrial wastes. A water pollution control plant.

The costs related to the amount of wastewater discharged to the sanitary sewer system. Measured in hundred cubic feet (CCF’s) for customers with water meters and the number of rooms and indoor plumbing fixtures for customers without water meters.

The financial assistance available to homeowners for MSD-related issues causing backups: Overcharged Sewer Line - If excessive rain falls in a short timeframe, it can fill the sewer line so much that it can't hold any more water. If sewer lines discharge into your building as a result, MSD will reimburse up to current limits -- to cover damage that occurs. Because damages may exceed this amount, MSD recommends homeowners obtain additional coverage through their insurance company. Blocked Sewer Line - If a sewer line collapses or is blocked by tree roots, or other debris that has washed into the sewer, it can cause a building backup. If this is the cause, MSD will reimburse the homeowner for the adjusted losses. See Financial Assistance for Building Backups for more details.

The suitability of water for given uses as measured by the levels of pollutants it contains. Water use classification, as defined by the State of Missouri, includes: public water supply; recreation; propagation of fish and other aquatic life, agricultural use and industrial use.

A value used for design purposes that accounts for the majority of the rainfall events in a given area, but excluding high volume events.

The volume of water needed to be captured and treated from a given area for a storm that is equal to the water quality rainfall event.

A natural or artificial channel for the passage of water, either continuously or intermittently.

A region or area bounded peripherally by water parting and draining ultimately to a particular watercourse or body of water.

Winter Quarter is the average billing calculated on readings, for Residential Metered customers, obtained by your water provider for the timeframe of January 15th through April 30th (representing water usage from mid-December through March) each calendar year.

Wastewater Treatment Plant