Glossary & Definitions

Accrual Basis of Accounting
A basis of accounting in which transactions are recognized when they occur, as opposed to being recognized when the actual cash changes hands.

Aeration basin
A tank that is part of a biological treatment system used for nitrification.

Ambient air quality
Quality of the outside air.

Anadromous fish
Fish that ascend rivers from the sea at certain seasons for breeding (e.g., salmon).

In the absence of oxygen.

Growing or living in or upon the water.

A geologic formation capable of yielding a significant amount of groundwater to wells or springs.

Average dry weather flow (ADWF)
The average non-storm flow over 24 hours during the dry months of the year (May through September). It is composed of the average sewage flow and the average dry weather inflow/infiltration.

Average wet weather flow (AWWF)
The average flow over 24 hours during the wet months of the year (October through April) on days when no rainfall occurred on that or the preceding day.

Best Management Practice (BMP)
A method, activity, or procedure for reducing the amount of pollution entering a water body.

The process of filtering water or air through a redundant media that has been allowed to develop a microbial biofilm that assists in the removal of fine particulate matter and dissolved organic materials. Also called biological filtration.

Biological Treatment
A method of wastewater treatment in which bacterial or biochemical action is intensified as a means of producing oxidized wastewater.

Residential wastewater from toilets, dishwashers, kitchen sinks and garbage grinder fixtures.

An estimate of revenues and expenditures for a period of time into the future.

Capital Improvement Projects (CIP)
A detailed plan that identifies requirements for the expansion, repair, replacement and rehabilitation of facility infrastructure over an extended period, often 20 years or more. A utility usually updates or prepares this plan annually. For wastewater systems, the plan consists of programs and projects to upgrade and rehabilitate wastewater collection and treatment systems and increase their capacity to allow for future growth.

Mechanical equipment used to remove water from digested solids.

A settling tank to separate solid & liquid material.

Clean Water Act
Also known as the Federal Water Pollution Control Act (33 U.S.C. 1251 et seq.).

Connection Fees
Fees charged to join or to extend an existing sewer system. Often referred to as tap fees or system development charges (SDC). SDC revenue is used to pay for future capital improvements.

Debt Service
The principal and interest due and payable on outstanding revenue bonds and loans.

A chemical or physical process that kills organisms which cause infectious disease. Chlorine is often used to disinfect treated sewage.

The Department of Ecology is Washington State’s principal environmental management agency and is responsible for permitting municipal wastewater systems. They protect the air, water and land.

Treated water, wastewater or other liquid flowing out of a treatment facility.

Environmental Protection Agency (EPA)
A federal agency established in 1979 by Presidential executive order to control pollution of the environment.

Equivalent Residential Unit (ERU)
An ERU is a unit of flow that represents the average volume of wastewater discharged by a family in a day. It is a term commonly used to compare or relate wastewater demand or flow from various uses (e.g. residential, commercial).

A body of water where freshwater joins saltwater.

Under the accrual basis of accounting an expense account records the cost of goods or services received without consideration of whether cash was expended or not.

Fiscal Year
Any period of twelve months that is designated as the operating year for accounting and budgeting purposes. The District’s fiscal year is from January 1st through December 31st per Washington state statute.

Force main
A pipeline leading from a pumping station that transports wastewater under pressure.

Allocation of money that is segregated for carrying out a specific purpose or activity

Generally Accepted Accounting Principles (GAAP)
Standards formulated by the Governmental Accounting Standards Board that set the guidelines used for accounting and reporting for government entities.

Gallons per minute, a rate of liquid flow.

Residential wastewater from showers, bathtubs, washing machines and bathroom sink fixtures.

Initial part of a treatment plant used for removing large debris.

"Impacts" are the effects or consequences of actions. Environmental impacts are effects upon the elements of the environment listed in WAC 197-11-444.

Industrial wastewater
Water or liquid-carried waste from any industry, manufacturing operation, trade, business or commercial establishment which includes process wastewater, cooling water, contaminated stormwater, contaminated leachates, or other waters in some combination such that the combined effluent differs in some way from purely residential wastewater, or is subject to regulation under federal categorical pretreatment standards, the state waste discharge permit program, or this chapter.

Flow of groundwater into a wastewater collection system through cracks and gaps in the piping or manholes.

Flows of surface water runoff directly into a wastewater collection system from sources other than sanitary sewer connections, such as roof leaders, basement drains, manhole covers, cross connections from storm sewers, and street washing.

Water, wastewater or other liquid flowing into a reservoir, basin or treatment plant.

A large diameter gravity sewer line which receives flow from many trunk sewers, force mains and sewer mains and generally, has no side sewer connections.

Intergovernmental Revenues
Revenues received by the District from other governments for providing services.

Interlocal Agreement
An agreement between two or more government entities pursuant to Chapter 39.34 RCW.

Manhole Grouting
Manhole grouting is a technique used to restore and repair manholes as a defense against infiltration and Inflow of water in structurally sound sewer systems.

Million gallons per day, a rate of liquid flow.

New Assets Capital Improvement Projects Account
An account that is used to fund future infrastructure improvements (e.g. CIP). SDC’s are the primary revenue source for this fund.

Nonpoint source pollution
Pollution that enters water from dispersed and uncontrolled sources (such as surface runoff) rather than through pipes. Nonpoint sources (e.g., stormwater runoff from agricultural or forest operations, on-site sewage disposal systems, and discharge from boats) may contribute pathogens, suspended solids, and toxicants. The cumulative effects of nonpoint source pollution can be significant.

NPDES Permit
Permit issued by Ecology under the National Pollution Discharge Elimination System, which establishes reporting requirements and other conditions for discharge of pollutants to receiving waters.

The exit point, usually a pipe or pipes, where effluent is discharged from the wastewater treatment system into receiving water and which is engineered to ensure dispersion and dilution of the effluent in the receiving waters.

Peak flow
The maximum flow expected to enter a facility.

Point source pollution
Pollution emanating from a single, well-defined location.

The reduction, alteration or the elimination of pollutants in wastewater prior to (or in lieu of) introducing such pollutants into the collection or treatment system. This reduction or alteration can be obtained by physical, chemical or biological processes; by process changes; or by other means (except by diluting the concentration of the pollutants unless allowed by an applicable pretreatment standard).

Pretreatment program
An industrial wastewater pretreatment program administered by Ecology or applicable control authority and/or the U.S. EPA under their respective laws and regulations and includes any requirements for local municipalities necessary to assist and support Ecology and/or EPA’s program.

Primary treatment
The first stage of wastewater treatment involving removal of floating debris and solids by screening and/or settling.

Pump Station
A structure used to move wastewater uphill, against gravity.

Raw sewage
Untreated wastewater.

Assets that are segregated for future use or for a specific purpose.

Restoration & Replacement (R&R)
Restoration or replacement of existing assets to maintain or extend their useful life including general facilities such as trunk sewers and pump stations, local collection systems (e.g. 8” sewers) and fleet and facilities.

Rates and charges received by the District used to fund general operations, debt service, and capital construction projects. Revenue Sources include sewer service charges, system development charges, intergovernmental revenues, investment income, and related fees.

Revised Code of Washington (RCW)
A compilation of all permanent laws now in force in Washington State.

Salmon Creek Treatment Plant (SCTP)
A treatment plant facility owned by Discovery Clean Water Alliance with 100% capacity owned by the City of Battle Ground and the District. The majority of the District’s collected sewage is transmitted to the SCTP for treatment. Clark County provides the operating staff at the plant through contract with the Discovery Clean Water Alliance.

Salmon Creek Wastewater Management System (SCWMS)
The Salmon Creek Wastewater Management System consists of the SCTP and its related transmission facilities.

Once suspended material which has settled to the bottom of a liquid, such as the sand and mud that make up much of the shorelines and bottom of water bodies (e.g. lakes, rivers).

Septic Elimination Program (SEP)
A program of capital projects for the construction of local sewers to provide service to existing residences in order to help protect and enhance the quality of water resources and reduce environmental health problems caused by failing or improperly functioning septic systems.

Total organic waste and wastewater generated by residential and commercial establishments.

A channel or conduit that carries wastewater or stormwater runoff from the source to a treatment plant or receiving stream. Sanitary sewers carry household, industrial, and commercial wastewater. Storm sewers carry runoff from rain or snow. Combined sewers carry both kinds of water.

Side sewer
The portion of the sewer system that connects the customer’s plumbing system to the mainline sewer located in the public right-of-way. Consists of a public portion, within public right of way or easement, and a private portion, located on private property, which is the responsibility of the property owner to maintain and repair.

Special Purpose District (Title 57 RCW)
An independent governmental unit, separate from a general purpose government, which is authorized under Title 57 RCW, to provide specific municipal utility services (e.g. sewer, water).

State Environmental Policy Act (SEPA)
A state law (Chapter 43.21C RCW) which requires that state agencies and local governments consider environmental impacts when making decisions regarding certain activities, such as development proposals over a certain size, and comprehensive plans. As part of this process, environmental impacts are documented and opportunities for public comment are provided.

STEP System
Septic Tank Effluent Pumping System includes a septic tank and a pump. Sewage is conveyed by gravity to the tank through the building plumbing line. Liquid waste is pumped under pressure to the public sewer system. Solid waste will remain in the STEP tank where it naturally degrades and is eventually pumped out.

Water that is generated by rainfall and is often routed into drain systems in order to prevent flooding.

Suspended solids
Small particles of organic or inorganic materials that float on the surface of, or are suspended in, sewage or other liquids and which cloud the water. The term may include sand, mud, and clay particles as well as waste materials.

System Development Charges (SDC)
Fees charged to join or to extend an existing sewer system. Often referred to as tap fees or connection fees. SDC revenue is used to pay for future capital improvements.

Total Maximum Daily Load
A regulatory term describing the maximum amount of material from any source that can be discharged into a water body.

Total suspended solids (TSS)
The total suspended matter that floats on the surface of, or is suspended in, water, wastewater, or other liquid, and which is removable by laboratory filtering.

Causing death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions (including malfunctions in reproduction), or physical deformations in any organism or its offspring upon exposure, ingestion, inhalation, or assimilation.

Chemical, biological, or mechanical procedures applied to industrial or municipal wastewater or to other sources of contamination to remove, reduce, or neutralize contaminants.

A gravity sewer that receives flow from one or more mains, covering a large area, less than two square miles and may have direct side sewer connections.

Utility Local Improvement District (ULID)
A district formed by a local government to fund infrastructure improvements. Includes the levying of special benefit assessments against property which is specially benefited by improvements relating to the district. (36.94.230 RCW)

Washington Administrative Code (WAC)
The codified regulations adopted by various Washington state agencies through the rulemaking process.

Total flow within a sewerage system. In separated systems, it includes sewage and infiltration/inflow. In combined systems, it includes sewage and stormwater.

Wastewater District
A special purpose district that provides sanitary sewer services.

Water pollution
The addition of harmful or objectionable material to water in concentrations or sufficient quantities to adversely affect is usefulness or quality.

Water quality criteria
The levels of pollutants that affect use of water for drinking, swimming, raising fish, farming or industrial use.