Wet Weather Solutions Program

Abatement: The measures taken to reduce or eliminate pollution.

Acre-Foot: A term used in measuring the volume of water. It is equal to the quantity of water required to cover 1 acre, 1 foot deep; one acre-foot equals 43,560 cubic feet or 325,851 gallons.

Aeration: A process that forces air into wastewater. The oxygen keeps aerobic microorganisms alive in an activated sludge wastewater treatment plant, and sets off a chain reaction; live, eat, and multiply. Oxygen is an essential ingredient in all bio-treatment systems.

Ambient Water Quality: Quality of the waters into which effluent is discharged.

Anaerobic Digestion: The process by which sludge is stabilized by bacteria in a temperature-controlled, oxygen-free (anaerobic) environment.

Anti-backsliding: A provision in the Federal Regulations [CWA ss 303(d) (4); CWA ss 402(c); CFR ss 122.44(l)] that requires a reissued permit to be as stringent as the previous permit with some exceptions.

Authorized Program or Authorized State: A state, territorial, tribal or interstate National Pollutant Discharge Elimination System (NPDES) program which has been approved or authorized by the Environmental Protection Agency under federal regulations.

Average Number of Overflow Events per Year: The total number of combined sewer overflow events that occurred during the term of the wastewater discharge permit divided by the permit term in years.

Auxiliary Bypass: Flow relief of sanitary sewers by means of gravity overflow or portable mechanical pumps, which are used to divert flow from the sanitary sewer system to alleviate surcharging or flooding.

Average Flow: Average quantity of wastewater that enters the treatment system over a given period of time.

Baffles: Deflectors, grates and other items used to control the velocity of the wastewater, allowing a more uniform amount of wastewater to enter the treatment plant.

Berm: A levee, shelf, ledge or bench along a streambank that may extend into the channel to partially obstruct the flow of water, or runs parallel to the flow to contain the water within its streambanks. May be natural or man-made.

Best Management Practice (BMP): Common name for control of nonpoint source pollution and erosion.

Best Professional Judgment (BPJ): The method used by the EPA or state government when issuing NPDES permits to develop technology-based conditions for discharging pollutants on a case-by-case basis using all reasonably available and relevant data.

BOD5: The biochemical oxygen demand exerted over five days, a standard measure of the organic content of wastewater, expressed in mg/l (milligrams per liter).

Biochemical Oxygen Demand (BOD): A measure of the amount of oxygen used in the aerobic (with oxygen) decomposition of organic matter. It reflects the extent to which the wastewater has been treated. It gives a direct measurement of the strength of wastewater, usually expressed in mg/l (milligrams per liter).

Bypass: A flow relief device by which sewers can discharge a portion or all of their flow into a lake, stream or river to alleviate sewer backups.

Capital Budget: A planned schedule of projects and funding to acquire or improve land, property or facilities.

Catch basin: A chamber usually built at the curbline of a street, which admits water runoff and directs it into a storm drain.

Channelization: The realignment of a stream channel.

Chemical Oxygen Demand (COD): A measure of water quality. It measures the amount of oxygen required to chemically oxidize materials in water.

Chlorination: The process of adding chlorine to the treatment plant wastewater before it is discharged to kill most of the bacteria.

Clean Water Fund Loans: This program provides low interest loans for the construction of wastewater treatment facilities, nonpoint source pollution projects and estuary projects.

Clearwater: Rainwater or snowmelt entering the sanitary sewer system through infiltration or inflow . It reduces the sewer system capacity to carry sanitary sewage.

Coarse Screening: The first step in preliminary treatment that removes debris from the wastewater by screening.

Collection and Transportation System: A series of sewers, manholes, pumping facilities, and force mains which carry wastewater from residences, commercial establishments, public buildings, institutions, and industrial plants. It terminates at a treatment plant. Bypasses are considered a part of this system.

Collector Sewers: That portion of the collection and transportation system that gathers wastewater from individual buildings and transports it through a network of sanitary sewers to interceptor sewers.

Combined Sewers: A sewer that carries both sewage and stormwater runoff.

Combined Sewer Overflows: Release of untreated sewage and stormwater directly into marine waters, lakes and rivers during heavy rainfall, when the sewers have reached their capacity.

Compliance Schedule: A schedule of remedial measures included in a pollution discharge permit or an enforcement order (link to definition), including a sequence of interim requirements that lead to compliance with the Clean Water Act and regulations.

Containment Boom: Equipment inserted into water and used to absorb and contain liquid by forming a gate around the liquid. It consists of a floatation device and below-water skirt.

Conventional Pollutants: Components of wastewater (link to definition) as determined by the Clean Water Act, including, but not limited to, pollutants classified as biochemical oxygen demand, total suspended solids, oil and grease, fecal coliform, and pH.

Conveyance System: The system of sewers designed and operated to intercept and carry sewage from local government collection systems to the wastewater treatment plants.

Criteria: The numeric values and the narrative standards that represent pollution limits for surface water, ground water and sediment in order to protect the uses of the water.

Design Flow: Quantity of wastewater that a treatment facility is designed to handle, usually expressed in millions of gallons per day (MGD).

Designated Use: The ways in which a particular water body (lake, river, stream) is used as specified by the EPA or state government. The designated uses are tied to specific water quality criteria for each water body.

Detention Basin: A rainwater runoff storage facility that is normally dry but is designed to hold the water temporarily during and immediately after a heavy rainfall.

Development: Any activity that alters the surface of the land that generally creates additional hard surfaces including, but not limited to, pavement, buildings and structures.

Dewatering: Any process that removes water from sludge , i.e., vacuum filtering, centrifuging, decanting, heat drying, etc. The term is also used to describe the removal of groundwater during sewer construction projects.

Discharge Monitoring Report (DMR):The form used to report self-monitoring results by entities with an NPDES permit.

Dissolved Oxygen: Oxygen dissolved in water (as opposed to gaseous oxygen which occurs in water only as bubbles), available for respiration by most aquatic organisms.

Diversion Structures: Structures constructed to divert or change the flow of wastewater and/or stormwater. The structures are used in combined sewer systems to direct the wastewater and stormwater to the treatment plant during normal conditions and to divert excess water to a storage facility or an overflow point during wet weather.

Domestic Wastewater: Wastewater that comes from nonindustrial sources such as homes, businesses and institutions.

Dry Weather Overflow: A combined sewer overflow that occurs during dry weather. usually caused by blockage due to.

Dryer Cyclone: A piece of equipment used to remove dust particles from the dryer exhaust at the treatment plant.

Easements: A right to obtain access to property; can be temporary or permanent.

Effluent or Effluent Discharge: Sewage, water or other liquid, flowing out of a reservoir, basin or treatment plant.

Effluent Limitations: The maximum amount of a pollutant that a point source may discharge into a water body as specified in an NPDES permit. A permit may allow some or no discharge at all, depending on the specific pollutant to be controlled and the water quality standards established for the lake, river or stream receiving the discharge.

Enforcement Order: A directive from the EPA or state government to come into compliance with the Clean Water Act and subsequent regulations.

Environmental Assessment: The aspect of the facility planning process and resulting report analyzing environmental, social and economic implications of the proposed alternatives.

Environmental Protection Agency (EPA or USEPA): The federal agency responsible for regulating water quality and the Federal Clean Water Act.

Erosion: The removal of soil particles by flowing water.

Flood Control: Preventing the entry of stormwater into an area from another area, or from a stream or other water body.

Floodwall: A concrete or masonry embankment built to restrain the flow of water of a riverbank and protect land from flooding.

Flow Regulator: A structure that controls the flow or movement of wastewater. It can restrict the flow or halt it completely for temporary storage.

Flow: The liquid (water, wastewater, stormwater) that moves from one location to another.

Force Mains: Pipes used to convey wastewater under pressure against the force of gravity.

Gate: A device in a sewer that creates a barrier to control the rate or direction of the flow of wastewater.

General Permit: A permit issued under EPA regulations (40 CFR ss 122.28) that authorizes a category of discharges under the Clean Water Act within a geographical area. A general permit is not specifically tailored for an individual discharger.

Geographic Information System (GIS): A computer system designed to tie data and information to locations and display that information on a map.

Heavy Metals: A general name given to the metallic elements such as copper, zinc, iron, chromium and aluminum that are used to manufacture products. They are found in some wastewater and are normally removed by a chemical substance that cannot be dissolved in water (usually a metallic hydroxide in industrial settings).

Industrial Pretreatment Program: Partial treatment of wastewater required for some industries. The process removes some type of pollutants before the wastewater enters the municipal sewer system.

Inflatable Dam: A temporary dam constructed of inflatable rubber inside the sewer system that is used to control the amount of overflow from the sewer.

Infiltration/Inflow:. Extraneous water that has entered a sanitary sewer system. Infiltration is groundwater-related flow that enters the sanitary sewer system through physical defects such as cracked pipes, deteriorated pipe joints, and leaking manholes. Inflow is rainfall-related flow that enters the sanitary sewer system from surface flows through sources such as building roof drains, yard drains, storm water sump pumps, manhole covers, and cross-connections between the storm sewer and sanitary sewer system.

Influent: The wastewater entering the wastewater treatment plants.

Inline Storage System (ISS): A system that provides relief to the sewer system during extreme wet weather periods by allowing excess flows to be diverted to a storage area. The excess flow is stored until treatment plant capacity is available.

Instrumentation and Control (I&C): Equipment used to monitor and control wastewater treatment processes.

Interceptor: Large sewers that collect wastewater from local trunk sewers and convey it to the wastewater treatment plants.

Lateral: A smaller sewer pipe that connects a building to the collector sewer line.

Levee: A natural or man-made earthen obstruction along the edge of a stream, lake or river. Also, a long, low embankment usually built to restrain the flow of water out of a riverbank and protect land from flooding.

Lift Station: A facility in a sewer system which collects and lifts wastewater to a higher elevation.

Million gallons per day: A unit of measurement commonly used for wastewater discharges. One MGD is equivalent to 1.547 cubic feet per second.

National Pollutant Discharge Elimination System (NPDES): The national program administered by the EPA in compliance with the Clean Water Act that controls discharges of pollutants into waters such as lakes, rivers and streams. NPDES permits contain limitations based on water pollution control technology and surface water (lakes, rivers, streams) quality standards, whichever is more stringent. They also establish best management practices and monitoring and reporting requirements. Entities that discharge or propose to discharge into the Nation's waters must apply for a permit.

Nonconventional Pollutants: Pollutants that are not defined as conventional pollutants in the Clean Water Act nor as priority pollutants in the federal regulations.

Non-point Source Pollutants: Pollutants which do not enter the water from any discernable, confined and discrete conveyance but rather wash off, run off or seep from broad areas of land.

Office of Wastewater Management (OWM): Office within the EPA that oversees a range of programs contributing to the well-being of the nation's waters and watersheds. Through its programs and initiatives, OWM promotes compliance with the requirements of the Federal Water Pollution Control Act.

Operation and Maintenance Budget (O&M): Annual budget for activities related to controlling, operating, managing and maintaining the sewer system.

Organic Matter: Material derived from living things.

Outfall: The point or location where sewage or drainage discharges from a sewer, drain or conduit to receiving waters.

Overflow: (1) The untreated wastewater and stormwater that empties out of the combined sewer system directly into lakes, rivers or streams when the sewer system is overloaded during wet weather. (2) The untreated wastewater that empties out of the sanitary sewer system into lakes, rivers, streams, streets, or buildings when the sewer system is overloaded, often due to wet weather.

Overflow Rate: The amount of water released from a detention basin divided by the surface area of the basin. It can be thought of as an average flow rate through the basin. Generally expressed as gallons per day per square ft (gpd/sq.ft.)

Peak Flow: The maximum volume of effluent expected to enter a treatment system over a given time period. Treatment systems are designed based on an estimate of the rate of peak flow to average flow for different segments of the system.

Point Source Pollutants: Those pollutants that enter the receiving water from any discernable, confined and discrete source or outlet such as a sewer pipe, culvert, tunnel or other channel.

Preliminary Treatment: The first stage of wastewater treatment, which removes debris, sand, grit and fine particles.

Pretreatment: Any process used by local industries to reduce the pollution amount before wastewater is introduced into a main sewer system or delivered to a treatment plant.

Primary Clarification: The first process in wastewater treatment in which solids are settled to the bottom of the water and then removed. This is the level of treatment that would typically be provided under peak wet weather flow conditions.

Primary Treatment: The process following preliminary treatment of wastewater at the plant which allows solids to settle, thicken and be removed. Primary effluent goes on to secondary treatment. The sludge is removed for processing by anaerobic digestion.

Publicly-Owned Treatment Works (POTW): A treatment system, as defined by the Clean Water Act (Section 212) that is owned by the state or municipality. This definition includes any devices and systems used in the storage, treatment, recycling and reclamation of municipal sewage or industrial wastes of a liquid nature. It also includes sewers, pipes and other conveyances only if they convey wastewater to a POTW treatment plant.

Pumping Station: A facility designed not only to lift sewage to a higher elevation but also to convey it through force mains to points where sewage flows by gravity.

Rainfall Duration: The length of time of a rainfall event.

Rainfall Intensity: The amount of rainfall occurring in a unit of time, usually expressed in inches per hour.

Receiving Water: A river, lake, stream or other body of water into which wastewater or treated effluent is discharged.

Regulator: A structure in the combined sewer system designed to direct normal flows to wastewater treatment while diverting excess wet weather flows to surface streams.

Relief Sewer: A river, lake, stream or other body of water into which wastewater or treated effluent is discharged..

Sanitary Sewers: Sewers that are designed to carry only sewage (wastewater) coming from inside buildings (from sinks, showers, toilets, etc.). Stormwater runoff is carried in a separate sewer.

Sanitary Sewer Overflows (SSO): Unintentional discharges of raw sewage from municipal sanitary sewers.

Secondary Treatment: A process to biologically remove dissolved solids and pollutants from the water by means of the activated sludge process.

Sediment: Soil particles eroded by flowing water; either suspended in the water or deposited on land.

Sensitive Areas: Areas of particular environmental significance or sensitivity that could be adversely affected by a sewer overflow, including outstanding natural resource waters, natural marine sanctuaries, water with threatened or endangered species, waters with primary contact recreation, public drinking water intakes, shellfish beds, and other areas identified by the municipality, state or EPA.

Separated Sewer: A two-pipe sewer system in which one pipe collects wastewater and sends it to a treatment plant and the other pipe collects storm water, which is typically discharged to a stream.

Service Area: The area that will be served by a wastewater treatment system.

Sewage: Sewage refers to the wastewater generated by residential, commercial, and industrial establishments that flows through pipes to a treatment plant.

Sewerage: Sewerage refers to the system of sewers and physical facilities employed to transport, treat, and discharge sewage.

Skimmer Vessels: A device to take up and remove floating matter in wastewater.

Sludge: the accumulated settled solids deposited from sewage or industrial wastes, raw or treated, in tanks and basins, and containing more or less water forming a semi-liquid mass.

Solids: The particulates contained in, or removed from wastewater (debris, sand and grit, sludge).

State Revolving Fund Program: A federal program created by the Clean Water Act Amendments in 1987 that offers low interest loans for wastewater treatment projects.

Storm Sewer: A conduit that collects and transports rain and snow runoff only. In a separate sewer system, storm sewers are entirely separate from those carrying wastewater.

Stormwater: Rain water and snow melt that runoff hard surfaces such as buildings, streets, sidewalks, parking lots and driveways.

Stormwater Storage:Temporary storage of stormwater for the purpose of reducing excess runoff.

Sump Pump: A pump, often in the basement of a house, that removes water from a drain or receptacle for liquids.

Surcharge: An uncontrolled spillage of wastewater that does not occur at a designated sewer overflow point.

Swirl Concentrator: A device that uses the force of rotating water to concentrate sewage by trapping the pollutants and debris in the vortex (whirlpool) of swirling water.

Total Maximum Daily Load (TMDL): Maximum allowable loading for a pollutant for a given stream segment.

Total Suspended Solids (TSS): Small particles of solid pollutants in sewage that contribute to turbidity and that resist separation by conventional means. One of the two main determinations for water quality.

Trickling Filter: An aerobic biological treatment process for wastewater that filters the wastewater. The Blue River Secondary Plant utilizes trickling filters.

Turbidity: A loss of clarity in the water due to sediment and other pollutants.

User Charges: Fees levied upon users of a wastewater treatment system based upon the volume and characteristics of their waste.

Wastewater: Water that has been used and rendered unsuitable for reuse without treatment. It is collected from buildings (homes, businesses, institutions, industrial facilities) and transported through sewers.

Water Quality Criteria: The levels of pollutants that affect the suitability of water for a given use. Generally, water use classification includes: public water supply; recreation; propagation of fish and other aquatic life; agricultural use and industrial use.

Water Quality Standard: A law or regulation that consists of the beneficial use or uses of a waterbody, the numeric and narrative water quality criteria that are necessary to protect the use or uses of that particular waterbody and an antidegradation statement.

Waters of the United States: All waters that are currently used, were used in the past or may be susceptible to use in interstate or foreign commerce. Waters of the United States include but are not limited to all lakes, rivers and streams (including intermittent streams), mudflats, sand flats, wetlands, sloughs, prairie potholes, wet meadows, play lakes or natural ponds.

Watershed: The land area that drains into a lake or river. Also called catchment area, drainage area, or river basin and expressed in acres or square miles.

Weir: A half wall in the sewer system that diverts all wastewater to the treatment plant during dry weather and diverts excess wastewater and stormwater to a storage facility or an overflow point during wet weather.

Wet Weather Flow: The amount of wastewater and stormwater in the sewer system during periods of rain or snow melt.

Wet Weather Flow Conditions: The traits of the wastewater and stormwater within the combined sewer system resulting from precipitation.