Glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

References

A

AASHTO: American Association of State Highway and Transportation Officials

access shaft: vertical work shaft used to access subsurface tunneling operations. The shaft allows removal of excavated materials and the installation of tunnel materials.

accessory building: a detached building whose purpose is related to, but subordinate to, that of the principal building on a given parcel of land.

acid rain: rain with a pH of less than 5.6 that has mixed with sulfur and nitrogen oxides in the atmosphere as a result of burning fossil fuel. Acid rain can damage buildings, wildlife and aquatic life.

acre-foot: a volume of water one foot deep and one acre in area, or 43,560 cubic feet.

aeration: a process used in wastewater treatment that promotes biological degradation of organic matter in water. The process can be passive (waste is exposed to air), or active (a mixing or bubbling device introduces oxygen).

aeration tank: a chamber used to inject oxygen into wastewater during treatment.

aesthetics: describes the visual quality of buildings and spaces within a townscape.

annexation: the process a municipality acquires surrounding land and incorporates it into its jurisdiction.

ASTM: American Society of Testing and Materials

B

base flow: the portion of stream flow that is not due to runoff from precipitation, usually supported by water seepage from natural storage areas such as aquifers, lakes, or wetlands.

basin: a structure, located above or below ground, that temporarily stores storm water, wastewater or combined sewage. Combined sewage basins generally hold the flow until the sewer system has sufficient capacity to transport it to the treatment plant. Many basins are equipped with treatment devices should primary treatment and disinfection be necessary. (Also, see storm water retention basins.)

belt filter press: equipment that reduces the water content of solids removed during the wastewater treatment process. These solids (called sludge) are easier and less costly to haul and dispose of when water content is reduced.

Best Management Practice (BMP): a practice or combination of practices that prevents or reduces storm water runoff and/or associated pollutants.

Biochemical Oxygen Demand (BOD): a laboratory measurement of wastewater that is one of the main indicators of the quantity of pollutants present. BOD measures the amount of oxygen that will be consumed by microorganisms when oxygen in wastewater biologically reacts with organic material in the wastewater. A decrease in BOD indicates that water quality is improving.

bioengineering: the science that uses living plant materials as a main structural component to control erosion, sedimentation, and flooding. Also referred to as soil bioengineering, it is used for land stabilization and habitat restoration.

blight: unsightly condition including the accumulation of debris, litter, rubbish, or rubble; fences characterized by holes, breaks, rot, crumbling, cracking, peeling or rusting; landscaping that is dead, characterized by uncontrolled growth or lack of maintenance, or damage, and any other similar conditions of disrepair and deterioration regardless of the condition of other properties in the neighborhood.

borings: cylindrical samples of a soil profile used to estimate the load-carrying capacity of the soil or determine infiltration capacity.

brownfield: abandoned, idled, or underused industrial and commercial facilities where expansion or redevelopment is complicated by real or perceived environmental contamination.

buffer: a strip of land , fence, or border of trees between one use area and another.

C

Capital Improvement Program (CIP): a program that spaces projects over several years, allowing municipalities to stay within their debt limit.

cast-in-place: mortar or concrete that is deposited in the place where it is required to harden as part of the structure, as opposed to precast concrete.

catch basin: a below-ground structure designed to collect and convey water into the storm sewer system. The design allows sediment to fall to the bottom of the catch basin and not directly into the pipe.

Central Business District (CBD): the major commercial downtown center of a community.

check dam: a log or earthen structure used in swales to reduce water velocities, promote sediment deposition and enhance infiltration.

chlorination: the process of disinfecting treatment plant effluent by mixing with chlorine.

cistern: an underground tank or pipe to collect storm water runoff from catch basins prior to discharge into sewer systems. Cisterns are used to store and slowly release storm water from residential areas into the combined sewer system until the threat of CSOs has passed.

Clean Water Act (CWA): the Clean Water Act is a 1977 amendment to the Federal Water Pollution Control Act of 1972 which set the basic structure for regulating discharges of pollutants to waters in the United States. The law gave the EPA authority to set effluent standards on an industry basis and continued the requirements to set water quality standards for all contaminants in surface waters. The CWA makes it unlawful to discharge any pollutant into a navigable water unless a NPDES permit is obtained under the Act. The CWA was reauthorized in 1987. The reauthorization focused on toxic substances, authorized citizen suit provisions and funded sewage plants under the Construction Grants Program.

cluster development: a development approach where buildings are grouped in close proximity and the remaining land is used as open space and recreational land.

cold patch: aggregates and liquid bitumin mixed up by hand or plant and stockpiled for patching or maintenance.

collection system: a network of sewer pipes used to collect wastewater and/or storm water and transport it to a wastewater treatment plant or sewer outfall.

collector sewers: pipes that run under city streets and receive sewage from homes and businesses. Collector sewers connect directly to an interceptor sewer that carries the wastewater to a treatment facility.

combined sewer: a sewer system that carries both sewage and storm water runoff. Normally, its entire flow goes to a wastewater treatment plant, but during a heavy storm, the volume of water may be great enough to cause overflows of untreated mixtures of storm water and sewage into receiving waters. Storm water runoff may also carry toxic chemicals from industrial areas or streets into the sewer system.

combined sewer overflow (CS0): discharge of a mixture of storm water and sewage when the flow capacity of a sewer system is exceeded during rainstorms.

commingling: the mixing of flows from two different sources. An example would be discharging sanitary sewer flows into a combined sewer system.

conditional use permit: a permit issued by the city or city and county planning commissions stating that the conditional use complies with the conditions and standards set forth in this title and authorized by the planning commission.

Consent Decree: a legal document, approved by a judge, that formalizes an agreement reached between EPA and potentially responsible parties (PRPs) through which PRPs will cease or correct actions or processes that are polluting the environment. The Consent Decree describes the actions PRPs will take and may be subject to a public comment period.

control structure: a structure such as a weir, gate or regulator located at a point in a sewer where flows can be detained or diverted in a different direction to prevent sewer pipes from becoming overloaded.

cubic feet per second (cfs): a unit of measure for the rate of liquid flow past a given point equal to one cubic foot in one second. 1 cfs is equal to 1.547 million gallons per day.

culvert: a closed conduit used for the passage of surface water under a road or other embankment.

D

decanting/dewatering: the process of draining or removing water from a storage structure like a basin or tunnel after a storm.

dechlorination: the process of removing residual chlorine from wastewater treatment plant effluent that has been disinfected with chlorine.

demography: the study of population and its characteristics, including its age structure, spatial distribution, growth patterns, social and economic characteristics, and ethnic composition.

density: the number of dwelling units per acre.

design storm: a rainfall event of specified size and return frequency (e.g. a storm that occurs only once every two years) that is used to calculate the runoff volume and peak discharge rate to a BMP.

designer: the registered engineer representing a firm, association, partnership, corporation or any combination of these who is responsible for the supervision or preparation of plans and specifications associated with storm drainage facility improvements.

detention: the temporary storage of storm water runoff to control peak discharge rates and provide gravity settling of pollutants.

detention time: the amount of time that a volume of water will remain in a detention basin.

diffuser: a porous tube or other device that air is forced through and divided into very small bubbles for interaction with organic pollutants found in liquids.

discharge: the rate of flow (the volume of water passing a point in a given period of time). Usually expressed as cubic feet per second.

disinfectant: a chemical or physical process that kills pathogenic organisms in water. Chlorine is often used to disinfect sewage treatment effluent, water supplies, wells, and swimming pools. Ultraviolet radiation is another disinfecting process used in wastewater treatment.

Dissolved Oxygen (DO): the oxygen freely available in water, vital to fish and other aquatic life and for the prevention of odors. DO levels are considered the most important indicator of a water body's ability to support desirable aquatic life. Secondary and advanced waste treatment are generally designed to ensure adequate DO in waste-receiving waters.

downspout disconnection: downspouts are connected into many combined sewer systems increasing the amount of rain water that gets into a system. Downspouts are disconnected at ground level to divert rain water onto lawns where it will filter into the ground. This requires capping the existing outlet pipe, installing a concrete splash pad at the downspout outlet and diverting the flow away from the home or building.

drainage area: the area of a watershed usually expressed in square miles or acres.

drawdown: the gradual reduction in water level in a storm water basin due to the combined effect of infiltration and evaporation.

dry weather flow: flow in a combined or sanitary sewer that is not influenced by a rain storm or snowmelt.

E

easement: a legal right, granted by a property owner to another entity, allowing that entity to make limited use of the property involved for a specific purpose. The Drain Commissioner secures temporary and permanent easements adjacent to County Drains to provide construction and maintenance access. Easements are recorded on the title to the land and transfer with the sale of land.

effluent: wastewater (treated or untreated) that flows out of a treatment plant, sewer, or industrial outfall into a surface water.

effluent limitation: restrictions established by a State or EPA on quantities, rates, and concentrations in wastewater discharges.

enclosed storm drainage system: a system of buried sewer pipes to collect and transport storm water to an outlet on a river, stream or lake. Most urban areas have enclosed storm drainage systems.

enclosures-Drain Commissioner: storm sewers which have been designated to be under the jurisdiction of the Drain Commissioner.

enclosures-municipal: storm sewers located outside of road rights-of-way for which the municipality has jurisdiction unless specific jurisdiction is designated by the Drain Commissioner, WCDPS, or MDOT.

environmental assessment: a review process for proposed federal, federally funded or federally licensed or sponsored projects or actions. An environmental assessment determines whether an action or project is environmentally significant and whether an environmental impact statement (EIS) must be prepared.

extended detention control device: a pipe or series of pipes that extend from the riser of a storm water pond that are used to gradually release storm water from the pond over a 24 - 40 hour period.

F

fill: added earth which is designed to change the contour of the land.

filter fabric: textile of relatively small mesh or pore size that is used to 1) allow water to pass through while keeping sediment out (permeable) or 2) prevent both runoff and sediment from passing through (impermeable).

filter strip: area of land covered with vegetation that slows and filters flows when depths are shallower than the vegetation height.

first flush: the delivery of a highly concentrated pollutant loading during the early stages of a storm, due to the washing effect of runoff on pollutants that have accumulated on the land.

floatables: materials found in sewers and storage tanks that are lighter than water.

floodplain: for a given flood event, that area of land adjoining a continuous watercourse that has been covered temporarily by water.

flushing gates: devices (gates) in a sewer or tank that can store flow. The flow is then released to flush sediments deposited in sewer and tank sections below the gates.

footing drain: drain tiles around a home’s foundation that collect water from around the home and prevent it from leaking into the basement.

footing drain disconnection: the removal of storm water footing drain flow from a combined or sanitary sewer system. This typically requires the installation of a sump pump to direct flows onto a lawn or into a nearby storm sewer system.

freeboard: the space from the top of an embankment to the highest water elevation expected for the largest design storm to be stored. The space is required as a safety margin in a pond or basin. A minimum of one foot is required.

frequent flooding: a phenomenon in urban streams whereby the number of bankfull and sub-bankfull flood events increases sharply after development. The frequency of these disruptive floods is a direct function of watershed imperviousness.

fringe wetland: narrow emergent wetland areas that are created by the use of shallow underwater benches along the perimeter of a wet pond. The benches are usually 15 feet wide and up to 12 inches deep. The fringe wetlands enhance pond pollutant removal, conceal trash and water level changes, reduce safety hazard, and create a more natural appearance.

G

gate: a moveable, water tight barrier used inside a sewer to control the movement or direction of wastewater flow.

goal: the long-term ideal or end product that is desired.

greenway: a linear park, alternative transportation route, or open space conservation area approved by the metro greenways commission that provides passive recreational opportunities, pedestrian and/or bicycle paths, and/or the conservation of open spaces or natural areas, as indicated in a greenway plan adopted by the commission.

gross floor area: the sum of the area of all of a building's floors existing within its exterior walls. A municipal zoning ordinance may define gross floor area as extending to the outer surface of the exterior walls; in commercial leasing, however, gross floor area is measured to the inside finish of these walls.

H

haul route: a designated street route construction equipment follows when going to or leaving a construction site. Usually, main roads with a direct route to an expressway are selected for the haul route.

heavy metals: metals that can be precipitated by hydrogen sulfide in acid solution, including lead, silver, gold, mercury, bismuth, and copper. Heavy metals are considered harmful to humans when ingested.

home occupation: commercial activity within an individual's dwelling. Several approaches may be taken by municipalities attempting to define which home occupations are to be permitted and are least likely to have an adverse impact upon the residential neighborhood.

hydraulic modeling: development of a computer model to represent the flow of wastewater in a collection system to determine how the system will react under different flow conditions.

hydraulics: the branch of engineering that deals with water or other fluid in motion.

hydrograph: a graph showing variation in the water depth or discharge in a stream or channel, over time, at a specific point along a stream.

hydrology: the applied science concerned with the waters of the earth in all their states - their occurrence, distribution, and circulation through the unending hydrologic cycle of precipitation, consequent runoff, streamflow, infiltration, and storage, eventual evaporation, and reprecipitation. It is concerned with the physical, chemical, and physiological reactions of water with the rest of the earth and its relation to the life of the earth.

I

illicit connection: an illegal connection of a sanitary sewer into a storm sewer that allows human waste to go directly into streams and rivers. Illegal connections also include illegal storm water connections to sanitary systems, such as sump pumps that homeowners have connected into the sanitary sewer system instead of discharging into their yard or storm sewer.

Illicit Discharge Elimination Plan (IDEP): a plan required by the USEPA's NPDES Permit Program to eliminate illegal, untreated sanitary discharges into surface and ground waters.

impervious areas: surfaces that cannot absorb rain water including streets, sidewalks, roofs, parking lots and driveways. The larger the impervious area, the greater the runoff volume.

infiltration: 1) the absorption of water into the ground, expressed in terms of inches/hour. 2) the penetration of water from the soil into sewer or other pipes through defective joints, connections, or manhole walls.

inflow: the discharge of storm water to a sanitary sewer system via footing drains, sump pumps, inappropriate catch basin connections, leaking manhole covers or other sources.

influent: flows into a treatment facility, storage facility, or sewer system. Influent characteristics, flow rates and volume are used to determine the size and treatment requirements of a facility.

in-system storage: the use of existing sewer pipes and structures to store excess flows during a wet weather event.

interceptor sewers: large sewer lines that, in a combined system, control the flow of sewage to the treatment plant. In a storm, they allow some of the sewage to flow directly into a receiving stream, thus keeping it from overflowing onto the streets. Also used in separate systems to collect flows from trunk sewers and carry them to treatment plants.

invert: the interior surface of the bottom of any pipe.

J

K

L

land use: the various ways in which land may be employed or occupied. Planners compile, classify, study and analyze land use data for many purposes, including the identification of trends, the forecasting of space and infrastructure requirements, the provision of adequate land area for necessary types of land use, and the development or revision of comprehensive plans and land use regulations.

land use plan: a proposal for how land should be used and where growth and renewal should occur. The land use plan, often one element of a comprehensive plan, is frequently developed concurrently with other closely related documents, such as transportation plans, environmental plans and community facility plans. Land use plans often cover a 20- to 25-year time span.

lateral sewer: a sewer that collects flows from homes and businesses for discharge into trunk sewers.

lot coverage: the proportion of the surface of a lot that is covered by buildings or that the municipal ordinance permits to be covered by buildings.

M

manhole: a concrete structure on a gravity sewer to permit entry for servicing.

Manning's Roughness Coefficient ("n"): a coefficient used in Manning's Equation to describe the resistance to flow due to the roughness of a culvert or stream channel.

mean: the average obtained by adding together the sum of the values and dividing by the number of values.

median: the value that appears at the midpoint of a distribution and divides the distribution in half.

Metropolitan Planning Organization (MPO): a local governmental unit that has legal jurisdiction over a geographic area for government service planning such as transportation and land-use planning.

million gallons per day (mgd): a measurement of water flow. It represents the number of million gallon increments of volume passing by a stationary point in a 24-hour period. Million gallons is abbreviated as MG.

mitigation: an activity or project to reduce the impact of a pollutant or replace lost land features such as wetlands and surface water.

Mixed-Use Development (MXD): a project in which a variety of complementary land uses are planned and constructed in one coordinated development. Typical mixed-use projects have office towers, street-level retail areas or malls, parking structures, and a subway and/or bus station at their base. Some have a hotel, theater or park as well.

modified county drains: open channels that have been designated as a County Drain and a major channel modification or relocation, widening or deepening has occurred under the jurisdiction of the Drain Commissioner.

moratorium: a temporary prohibition on new construction, usually imposed by government as a response to rapid growth that threatens to exhaust the water and sewer system or that is inadequately controlled by local land-use regulations.

N

National Pollutant Discharge Elimination System (NPDES): a provision of the Clean Water Act that prohibits discharge of pollutants into waters of the United States unless a special permit is issued by EPA, a state, or, where delegated, a tribal government on an Indian reservation.

natural buffer: a zone where plantings capable of filtering storm water are preserved or established and where construction paving or chemical application are prohibited.

natural county drains: drains that are designated as a County Drain where maintenance/cleanout operations have been performed under the jurisdiction of the Drain Commissioner.

natural watercourses: open channel sections of natural origin that have not been designated as a County Drain.

neotraditional development: an approach to land-use planning and urban design that promotes the building of neighborhoods with a mix of uses and housing types, architectural variety, a central public gathering place, interconnecting streets and alleys, and edges defined by greenbelts or boulevards.

net floor area: the total floor area of a structure minus the square footage devoted to elevator shafts, stairwells, interior space used for parking or loading, equipment and utility rooms and most basement areas.

New Urbanism: the process of reintegrating the components of modern life - housing, workplace, shopping and recreation - into compact, pedestrian-friendly, mixed-use neighborhoods linked by transit and set in a larger regional open space framework.

nonconformity: any nonconforming aspect of a structure, land, or use.

non-point source: sources of pollution that cannot always be traced to an exact point of entry. Non-point sources of pollution include land runoff that goes directly in the river, illicit sanitary sewer connections to a storm sewer and streambank erosion.

nutrient: an element or compound such as nitrogen, phosphorus or potassium that is necessary for plant growth. Fertilizers contain nutrients.

O

off-site detention: detention provided at a regional detention facility as opposed to storage on-site.

one hundred year flood (100-year flood): a surface water flood elevation that has a 1% chance of occurring in any given year.

one-year, one-hour storm: the intensity of a storm that statistically occurs at least once every year is called the 1-year, 24-hour storm. The 1-year, 1-hour storm is the hour during that storm with the heaviest rainfall.

open cut construction method: a method of construction where a large trench is cut to place a sewer or water main pipe.

open drainage system: a system of ditches and open channels that collect and transport storm water to an outlet on a river or stream. Open drainage systems are typically found in rural and industrial areas.

ordinance: a law, rule or regulation issued by the governing body of a local municipality under legal authority granted by the state. Ordinances are limited to the area over which the local governing body has jurisdiction.

organic material: material derived from organic or living things.

orifice: an opening in a wall or plate.

outfall: the conduit through which effluent is discharged into receiving waters.

overland flow: the flow of storm water across the land surface that ultimately reaches a stream, river or lake.

overlay district: additional zoning requirements that are superimposed upon existing zoning in specified areas shown on a zoning map. Overlay zones are commonly used when an area requires special protection or has a special problem.

oxbow: a loop formed by a horseshoe-shaped bend in a river.

P

peak discharge: the maximum instantaneous rate of flow during a storm, usually in reference to a specific design storm event.

permit: an authorization, license, or equivalent control document issued by an approved State agency to implement the requirements of an environmental regulation (e.g. a permit to operate a wastewater treatment plant or to operate a facility that may generate harmful emissions).

permit issuing authority: the State agency issuing NPDES or other environmental permits to regulated facilities.

pervious surfaces: surfaces that are permeable and absorb storm water. Grass is a pervious surface.

petition: a legal request to the Drain Commissioner to perform maintenance or construction, or to set up a drainage district. Either the municipality or individual(s) can petition to have work done or a district set up.

physical filtration: separation of particulate pollutants from storm water runoff as they pass across or through a surface of grass, or other organic matter.

pilot project: a project conducted on a small scale to demonstrate the effectiveness of an approach, such as to treat wet weather pollution or limit storm water from getting into a collection system.

Planned Unit Development (PUD): development characterized by comprehensive planning for the project as a whole, clustering of structures to preserve usable open space and other natural features, a mixture of housing types and sometimes a variety of nonresidential uses as well.

pocket wetlands: a storm water wetland design adapted for small drainage areas with no reliable source of base flow. The surface area of pocket wetlands is usually less than a tenth of an acre. The pocket wetland usually has no deep water cells, and is intended to provide some pollutant removal for very small development sites.

point source: discharges from stationary locations such as WWTPs, storm sewer outlets and factories. Point source discharges include combined sewer outfalls and storm sewer outfalls.

pollutant: generally, any substance introduced into the environment that adversely affects the usefulness of a resource.

pollution: generally, the presence of matter or energy whose nature, location, or quantity produces undesired environmental effects. Under the Clean Water Act, for example, the term is defined as the manmade or man-induced alteration of the physical, biological, chemical, and radiological integrity of water.

pond/wetland system: a two-cell storm water wetland design that uses a wet pond in combination with a shallow marsh. The pond/wetland design saves space and has been shown to be very effective at removing urban pollutants.

pretreatment: techniques to reduce/minimize pollutants prior to treatment facilities. In storm water, typically associated with detention basin forebays designed to capture or trap coarse sediments to preserve storage and prevent clogging. In wastewater, usually associated with industrial/commercial sites intended to reduce their discharge pollutant concentrations to levels that can be accommodated by a municipal wastewater treatment facility.

primary treatment: the first major treatment process in a wastewater treatment facility where solids and liquids are separated. This is usually done through a settling process where the materials that float or settle are removed. Primary treatment removes about 30% of pollutants from domestic sewage.

proprietor: any person or agent representing a firm, association, partnership, corporation, or any combination of these who proposes to undertake to modify or locate any structure within an identified storm drainage facility.

pumping station: a structure containing pumps and the associated piping, valves and other mechanical and electrical equipment for lifting wastewater to a higher level.

Q

R

Rational Method Formula: a simple technique for estimating peak discharge rates for developments, based on the rainfall intensity, watershed time of concentration, and a runoff coefficient. If a development is less than one square mile in area the formula is Q=CIA.

regulated wetland: any wetland protected by state law or local government regulation.

regulator: a device installed in combined systems to control the amount of flow into the sewer system during periods of wet weather. Excess flows are routed to an outfall.

release rate: the rate of discharge from a detention facility in volume per unit time.

relief sewer: a sewer built parallel to an existing sewer to carry a portion of the area's flow because the existing sewer is not large enough to transport the flows.

return interval: a statistical term for the average time of expected interval that an event of some kind will occur (e.g. a storm water flow that occurs every 2 years).

rezoning: a modification of, or amendment to, the zoning ordinance.

right-of-way: see easement.

riprap: a combination of large stone, cobbles, and boulders used to line channels, stabilize banks, reduce runoff velocities, or filter out sediment.

riser: a vertical pipe or weir within the embankment of a storm water wetland that is used to regulate the storm water discharge from the structure for specified design storm(s).

runoff: the excess portion of precipitation that does not infiltrate into the ground, but "runs off" and reaches a stream, water body, or storm sewer.

runoff coefficient: the ratio of the amount of water that is NOT absorbed by the surface to the total amount of water that falls during a rainstorm.

runoff conveyance: methods for safely conveying storm water to a wetland to minimize disruption of the stream network and promote infiltration or filtering of the runoff.

S

SA/V ratio: the surface area to volume ratio is a useful measure of the capacity of a storm water wetland to remove pollutants via sedimentation, adsorption, and microbial activity. The SA/V ratio can be increased by either increasing the surface area of a wetland or increasing the internal structural complexity within the wetland.

sanitary sewer: underground pipes that carry only domestic or industrial waste, not storm water.

sanitary sewer overflow (SSO): discharge of sewage when the flow capacity of a sanitary sewer system is exceeded.

scour: removal of sand or earth from the bottom or banks of a river by the erosive action of flowing water. Erosion of a concrete surface, exposing the aggregate. The action of a flowing liquid as it lifts and carries away the material on the sides or bottom of a waterway, conduit, or pipeline. The enlargement of a flow section of a waterway through the action of the fluid in motion carrying away the material composing the boundary.

screening: use of screens to remove coarse floating and suspended solids from sewage.

secondary treatment: the second major step in the wastewater treatment process where bacteria consume the organic parts of the waste. It is accomplished by bringing together waste, bacteria, and oxygen in trickling filters or in the activated sludge process. This treatment removes floating and settleable solids and when combined with primary treatment about 90% of the oxygen-demanding substances and suspended solids. Sludge disposal is included and disinfection is the final stage of secondary treatment.

sediment forebay: storm water design feature that employs the use of a small, separate cell pool to settle out incoming sediments before they are delivered to a storm water wetland. The forebay is typically 10% in excess of the total treatment volume of a BMP.

sedimentation: see settling.

septic system: a domestic wastewater treatment system that treats household waste through a septic tank and a soil absorption system. Bacteria decomposes the waste, sludge settles to the bottom of the tank, and treated effluent flows out into the ground through drainage pipes. Failing septic systems can contaminate ditches, creeks and shallow drinking water supplies.

setback: the required distance between every structure and the lot lines of the lot on which it is located.

settling: the process of subsidence and deposition of suspended matter carried by water, wastewater, or other liquids. It is usually accomplished by reducing the velocity of the liquid below the point that it can transport the suspended material. Also called sedimentation.

settling tank: a holding area for wastewater, where heavier particles sink to the bottom for removal and disposal.

sewage: the waste and wastewater produced by residential, commercial and industrial sources and discharged into sewers.

sewer: a channel or conduit that carries wastewater and storm water runoff from the source to a treatment plant or receiving stream. "Sanitary" sewers carry household, industrial, and commercial waste. "Storm" sewers carry runoff from rain or snow. "Combined" sewers handle both. Sewers are also categorized by the flow they carry, e.g. collector, interceptor and trunk.

sewer separation: replacing a combined sewer with a separate sanitary sewer pipe and a storm sewer pipe. The sanitary sewer pipe flow is transported to a wastewater treatment plant and storm sewer flow is discharged directly to a drain or river, without treatment.

sheetflow: runoff which flows over the ground surface as a thin, even layer, not concentrated in a channel.

short circuiting: the passage of runoff through a BMP in less than the theoretical or design treatment time.

shunt channel: a channel used to route flows around a storage basin when flow rates result in negative treatment.

site plan: an accurately scaled development plan that illustrates the existing conditions on a land parcel as well as depicting details of a proposed development. Among the features generally required on a site plan are the property boundaries and lot lines; major features of the landscape; and proposed street and utility networks, as well as planned access points.

skimming: the removal of floatables from combined or sanitary sewage.

sludge: the accumulated solids separated during primary and secondary treatment. It is disposed of through incineration or land application.

sludge cake: sludge that has been dewatered to a semi-solid mass.

snowmelt: runoff created when snow melts and the resulting water enters sewer systems.

sodium hypochlorite: a water solution of sodium hydroxide and chlorine where sodium hypochlorite is the essential ingredient. It is similar to laundry bleach and is used as a disinfectant in CSO basins.

soft engineering: is the use of ecological principles and practices to reduce erosion and achieve the stabilization and safety of shorelines, while enhancing habitat, improving aesthetics, and saving money.

Special Flood Hazard Area (SFHA): areas inundated by a flood having a one percent probability of being equaled or exceeded in any given year (also referred to as the 100-year flood).

spillway: a depression in the embankment of a pond or basin, used to pass peak discharges in excess of the design storm.

spot zoning: the assignment of a zoning classification different from the surrounding zoning classifications to a relatively small land parcel. Illegal spot zoning occurs when the use classification benefits the proprietor and is in violation of the community's comprehensive plan. Legal spot zoning includes new flexible zoning techniques (such as floating zones) or special zoning districts (such as historic districts).

State Revolving Fund (SRF) loan: a federal and state program offering low interest loans to municipalities for the construction of publicly-owned water pollution control facilities.

storage: temporary holding of wastewater before treatment, as in tunnels, basins or pipes.

storm drainage system: consists of any component and associated appurtenances which convey surface storm water runoff and include overland (street) drainage swales, street gutters, ditches, watercourse, drains, rivers, streams, various types of culvert and storm sewer enclosures, diversions, levees, and detention facilities. Stream - By MDNR definition: "a river, creek, or surface waterway that may or may not be defined by Act 40, P.A. of 1956; has definite banks, a bed, and visible evidence of continued flow or continued occurrence of water, including the connecting water of the Great Lakes." Even if water flow is intermittent, it is classified as a stream.

storm sewer: a system of pipes (separate from sanitary sewers) that carries only storm water runoff from buildings and land surfaces.

storm water detention basin: a constructed basin that temporarily stores water before discharging into a surface water body. Can be classified into three groups:

constructed wetland: a conventional wetland which uses a variety of depths to create conditions suitable for the growth of wetland plants. These constructed systems are not located within natural delineated wetlands.

extended detention basin: a detention basin that has been modified to increase the length of time that storm water will be detained to between 24 - 40 hours. Not effective at removing nutrients such as phosphorus and nitrogen, unless a shallow marsh is incorporated into the lower stage of the design.

wet detention basin: a detention basin that contains a permanent pool of water that will effectively remove nutrients in addition to other pollutants. This method is preferred in Canton Township.

storm water influenced wetland: refers to a natural wetland in an urban area that receives urban storm water runoff.

storm water runoff: water that runs off streets, roofs and land during rain storms, washing pollutants off these surfaces into the sewer system. Typical pollutants of storm water runoff include chlorides, coliform bacteria, heavy metals, nutrients, oil and grease, and suspended solids.

storm water wetland: a conventional storm water wetland is a shallow pool that creates growing conditions suitable for the growth of marsh plants. Storm water wetlands are designed to maximize pollutant removal through wetland uptake, retention, and settling. These constructed systems are typically not located within delineated natural wetlands.

stream bank erosion: the movement of sediment and soil material from the banks and bottom within a stream or river. The higher the flow, the greater the erosion.

streetscape: refers to all the elements that constitute the physical makeup of a street or avenue and that, as a group, delineate its character. A streetscape includes building frontage, street paving and furniture, street tree planting, lighting and signage.

substructure: the lower portion of a structure forming the foundation that supports the superstructure of a building.

subwatershed: a drainage area within a watershed.

superelevation: exaggerated tilt of roadway on a curve to counteract centrifugal force on vehicles.

superstructure: that part of a bridge above the bridge seats, above the spring line of the arches or above the bottom of the caps. That part of a building or other structure which is carried upon any main supporting level, as a foundation wall.

Supervisory Control and Data Acquisition (SCADA): a system used to electronically monitor (including the ability to trend data and generate regulatory reports) and control remote operations from a central point. For example, SCADA can be used to control and monitor the status of a remote pumping facility from a water or wastewater facility. A SCADA system consists of five major components: master computer, software, communication link, remote terminal and input/output devices. The key component is the communication link that can be dial up telephone, cellular telephone or radio frequency. Additional equipment is chosen based on compatibility with the communication link.

suspended solids: solid organic or inorganic particles physically held in suspension in wastewater by agitation or flow.

swale: a channel or a sloped surface that directs the flow of storm water runoff. Swales can be vegetated, lined with vegetation that slows and filters flows when depths are shallower than the vegetative height, or paved.

swirl concentrator: a treatment device that uses centrifugal force to remove pollutants from wastewater.

T

taking: occurs when the government acquires property or an interest in property from a private owner or otherwise substantially diminishes the value of property or substantially deprives the owner of the use and enjoyment of his property.

tax-increment financing: a means of financing redevelopment projects in which an area is improved with the proceeds of a bond issue slated to be repaid by the additional taxes the new development is expected to generate.

ten-year, one-hour storm: the intensity of a storm that statistically occurs at least once every ten years for a 24-hour period. The 10-year, 1-hour storm is the hour during that storm with the heaviest rainfall.

time of concentration: the time it takes for surface runoff to travel from the hydraulically farthest portion of the watershed to the design point.

Transfer of Developmental Rights (TDR): the transfer of the development potential of one piece of property to another.

treated wastewater: wastewater that has been subjected to one or more physical, chemical, and biological processes to reduce its pollution.

treatment plant: a structure built to treat wastewater before discharging it into the environment.

trunk sewer: a sewer that receives wastewater from many areas.

tunnel: a large, underground structure used to store and transport wastewater, combined sewage or storm water during rain storms. Tunnels usually have higher storage capacities than basins and are capable of transporting their flows directly to a wastewater treatment plant.

tunnel boring machine: a machine used to drill through the ground to create a tunnel.

tunneling construction method: an underground construction method where a tunnel boring or mining machine is used to drill a passageway for a tunnel pipe. Construction activities are conducted through an access shaft.

U

ultraviolet (UV) disinfection: the process of using ultraviolet radiation to disinfect wastewater treatment plant effluent. UV disinfection is an alternative to chlorination.

underdrain: plastic pipes with holes drilled through the bottom, installed on the bottom of an infiltration BMP to collect and remove excess runoff.

urban design: the attempt to give form, in terms of both beauty and function, to selected urban areas or to whole cities.

USEPA: The United States Environmental Protection Agency is the federal regulator responsible for administering the Clean Water Act.

V

value engineering: an independent review of project concepts and designs with the purpose of identifying opportunities to enhance the value of the project by systematically evaluating the project's functions and ways to achieve the functions at the lowest total cost.

W

wastewater: spent or used water from a home, community, or industry that contains dissolved or suspended matter.

wastewater collection system: a system of underground sewer pipes that collect wastewater from households and businesses and convey it to a wastewater treatment plant. Sometimes these pipes also collect storm water, called combined systems. Pump stations and control structures are considered part of the collection system.

wastewater infrastructure: the plan or network for the collection, treatment, and disposal of sewage in a community. The level of treatment depends on the size of the community, the type of discharge, and/or the designated use of the receiving water.

wastewater operations and maintenance: actions taken after construction to assure that facilities constructed to treat wastewater will be operated, maintained, and managed to reach prescribed effluent levels in an optimum manner.

wastewater treatment plant (WWTP): a facility containing a series of tanks, screens, filters and other processes used to remove pollutants from wastewater.

water pollution: the presence in water of enough harmful or objectionable material to damage the water's quality.

water quality criteria: levels of water quality expected to render a body of water suitable for its designated use. Criteria are based on specific levels of pollutants that would make the water harmful if used for drinking, swimming, farming, fish production, or industrial processes.

water quality standards: state-adopted and EPA-approved ambient standards for water bodies. The standards prescribe the use of the water body and establish the water quality criteria that must be met to protect designated uses.

watershed: the complete area or region draining into a river, river system, or body of water.

weir: a structure that extends across the width of a channel and is used to impound, measure, or in some way alter the flow of water through the channel.

wet pond: a conventional wet pond has a permanent pool of water for treating incoming storm water runoff.

wet sanitary system: a sanitary sewer system that experiences a higher volume of flow during wet weather due to storm water inflow and infiltration.

wet weather: weather that creates precipitation including rain, snow, sleet and hail.

wet weather pollution: pollution that occurs as the result of storm water entering a sewer system or running off impervious surfaces. Types of wet weather pollution include CSO, SSO and storm water runoff.

wetland: an area that periodically has water logged soils or is covered with a shallow layer of water resulting in reduced soil conditions. A wetland area typically supports plant life adapted to wet environments.

wetland mitigation: a regulatory term that refers to the process of constructing new wetland acreage to compensate for the loss of natural wetlands during the development process. Mitigation seeks to replace structural and functional qualities of the natural wetland type that has been destroyed. Storm water wetlands typically do not count for credit as mitigation, because their construction does not replicate all the ecosystem functions of a natural wetland.

wetland mulch: a technique for establishing low or high marsh areas where the top 12 inches of wetland soil from a donor wetland are spread thinly over the surface of a created wetland site as a mulch. The seedbank and organic matter of the mulch helps to rapidly establish a diverse wetland system.

wetted perimeter: the wetted surface of a stream (culvert) cross section which causes resistance to flow. The water to surface interface is a distance, usually expressed in feet.

X

xeriscape: a landscape designed with drought-tolerant plants.

Y

Z

zoning: an exercise of the police power in which utilization and development of privately owned land is regulated through the division of a community into various districts and the specification of permitted and/or prohibited uses for each district.

zoning variance: a waiver from compliance with a specific provision of the zoning ordinance granted to a particular property owner because of the practical difficulties or unnecessary hardship that would be imposed upon him by the strict application of that provision of the ordinance. The granting of variances traditionally is the responsibility of the zoning board of appeals.

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