Show/Hide
Best Management Practices (BMPs) -- BMPs are accepted standard maintenance procedures, prohibitions of practices, and other management practices to prevent or reduce the pollution in water runoff from properties to the ‘Waters of the United States" or "Waters of the State.” BMPs also include treatment requirements, operating procedures, and practices to control site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage during construction activities and the permanent use of land.


Biochemical Oxygen Demand (BOD)
-- The amount of oxygen used by microorganisms in the breakdown or decay of organic matter in a water body.

Biofiltration -- The use of vegetation (usually grasses or wetland plants) to filter and treat stormwater runoff as it is conveyed through an open channel or swale.

Biological diversity -- The concept of multiple species of organisms living together in balance with their environment and each other.

Bioretention -- The use of vegetation in retention areas designed to allow infiltration of runoff into the ground. The plants provide additional pollutant removal and filtering functions while infiltration allows the temperature of the runoff to be cooled.

Clean Water Act -- The CWA is the primary Federal law in the United States governing water pollution. The requirements of the NPDES program regulating stormwater discharges has its authority defined by Sections 301, 307, 402, 318, and 405 of the Act.

Construction General Permit -- An NPDES permit issued by the SWRCB for the discharge of stormwater associated with construction activity fro soil disturbances of one acre or more.

Design Standards -- Design Standards refers to the City's "Manual of Stormwater Quality Control Standards for New Development and Redevelopment." Within the Manual is a variety of post-construction design standards to incorporate specific structural BMPs into construction projects.

Detention -- The temporary storage of stormwater runoff to allow treatment by sedimentation and metered discharge of runoff at reduced peak flow rates.

Detention ponds -- A BMP consisting of a permanent pool of water designed to treat runoff by detaining water long enough for settling, filtering, and biological uptake. Wet ponds are also often designed to have an aesthetic or recreational value.

Discharge -- means any release, spill, leak, pump, flow, escape, leaching (including subsurface migration to groundwater), dumping, or disposal of any gaseous, liquid, semi-solid, or solid substance from the source to the City’s storm drain.

Erosion -- The wearing away of land surface by wind or water. Erosion occurs naturally from weather or runoff but can be intensified by land-clearing practices relating to farming, residential or industrial development, road building, or timber cutting.

Filter Strip -- Grassed strips situated along roads or parking areas that remove pollutants from runoff as it passes through, allowing some infiltration, and reductions of velocity.

Illicit Connection -- Illicit connections are defined as illegal and/or improper connections to storm drainage systems and receiving waters.

Illicit Discharge -- The discharge of anything other than stormwater to the municipal separate storm sewer system. No debris or waste should be dumped into the MS4 since these materials are quickly carried to nearby waters.

Impervious Surface -- A surface that cannot be penetrated by water such as pavement, rock, or a rooftop and thereby prevents infiltration and generates runoff.

Industrial General Permit -- An NPDES Permit issued by the SWRCB for the discharge of stormwater associated with industrial activity.

Infiltration -- The process or rate at which water percolates from the land surface into the ground. Infiltration is also a general category of BMP designed to collect runoff and allow it to flow through the ground for treatment.


Integrated Pest Management
-- IPM is an ecosystem-based strategy that focuses on long-term prevention of pests or pest-related damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant plant varieties. Pesticides are used only after monitoring indicates they are needed according to established guidelines, and treatment is implemented with the goal of removing only the target organism. See the City's IPM program website.

Low Impact Development -- LID means a sustainable landscaping approach that can be used to replicate or restore natural watershed functions and/or address targeted watershed goals and objectives such as pollution prevention related to stormwater. One of LID's primary goals is to reduce runoff volume by infiltrating rainfall water to groundwater, evaporating rainwater back to the atmosphere after a storm and finding beneficial uses for water rather than exporting it as a waste product down storm sewers. The result is a landscape functionally equivalent to predevelopment hydrologic conditions, which means less surface runoff and less pollution damage to lakes, streams and coastal waters.

Maximum Extent Practicable (MEP) -- MEP is the technology-based standard established in the Federal Clean Water Act that dischargers of stormwater must meet. Technology-based standards establish the level of pollutant reductions that dischargers must achieve. MEP is generally a result of emphasizing pollution prevention and source control BMPs primarily but possibly in combination with other treatment methods. The MEP approach is an ever evolving, flexible and advancing concept, which considers technical and economic feasibility. As knowledge about controlling pollutants in stormwater continues to evolve so does that which constitutes MEP. The way in which MEP is met varies between communities.

Measurable Goal -- Measurable goals are definable tasks or accomplishments that are associated with implementing BMPs who's collective outcome have a measurable or quantifiable effect upon the quality of stormwater discharge to the waters of the State or United States.

Minimum Control Measure -- A stormwater program area that must be addressed (BMPs implemented to accomplish the program goal) by all regulated Small MS4s. The six minimum control measures required to be addressed by regulated Small MS4s are defined in section 3.

NPDES -- National Pollutant Discharge Elimination System is an authorization, license, or equivalent control document issued by the EPA or an approved state agency to implement the requirements of the NPDES program as required by the Clean Water Act. In California, the SWRCB has issued General Permits for stormwater discharges associated with industrial and construction activities.

Natural buffer -- A variable width area maintained with natural vegetation between a pollutant source and a water body that provides natural filtration and other forms of protection.

Notice of Intent --NOI means a formal notice of intent that the city will comply with an NPDES permit to follow certain discharge conditions and to commence with activities submitted by the owner/operators of construction sites and industrial facilities. The NOI is submitted to the SWRCB and provides information on the permittee, location of discharge, type of discharge and certifies that the permittee will comply with conditions of the Construction and Industrial General Permits. The NOI is not a permit application and does not require approval.

Notice of Termination -- NOT means a formal notice of intent to terminate activities submitted by the owner/operators of construction sites and industrial facilities. The NOT is submitted to the SWRCB and provides information on the permittee. and certifies that the permittee is no longer subject to the conditions of the Construction and Industrial General Permits.

Notice of Violation -- NOV means a formal notice to the property owner whenever the City finds that a person has violated a prohibition or failed to meet a requirement of this Chapter.

Outfall -- the location where a point source from a municipal separate stormwater drainage discharges to Waters of the United States and does not include open conveyances connecting two municipal separate stormwater drainages, or pipes, tunnels or other conveyances which connect segments of the same stream or other Waters of the United States or State and are used to convey Waters of the United States or State.

Peak discharge -- The greatest volume of stream flow occurring during a storm event.

Permeability -- A property of solid that enables water or air to move through it. Usually expressed in inches/hour or inches/day.

Point Source Pollution -- 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, landfill leachate collection system, vessel or other floating craft from which pollutants are or may be discharged. This term does not include return flows from irrigated agriculture or agricultural stormwater.

Performance Standards -- Performance Standards are the level of implementation necessary to demonstrate the control of pollutants in stormwater to MEP.

Sedimentation -- The process of depositing soil particles, clays, sands, or other sediments that were picked up by runoff.


Small Municipal Separate Storm Sewer System (Small MS4)
-- Means a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains) that are:

  1. Owned or operated by the United States, a State, County, town, boroughs, county, parish, district, association, or other public body (created by or pursuant to State law) having jurisdiction over disposal of sewage, industrial wastes, stormwater, or other wastes, including special districts under State law such as a sewer district, flood control district or drainage district, or similar entity, or an Indian tribe or an authorized Indian tribal organization, or designated and approved management agency under section 208 of the CWA that discharges to Waters of the United States.
  2. Not defined as “large” or “medium” municipal separate storm sewer systems.
  3. This term includes systems similar to separate storm sewer systems in municipalities, such as systems at military bases, large hospital or prison complexes, and highways and other thoroughfares. The term does not include separate storm sewers in very discrete areas, such as individual buildings. MS4s are also referred to as storm drain systems.

State Water Resources Control Board -- SWRCB is an agency of the State of California who's mission is to preserve, enhance and restore the quality of California's water resources, and ensure their proper allocation and efficient use for the benefit of present and future generations. The SWRCB oversees all NPDES permitting in the State through its regional organizations known as Regional Water Quality Control Boards. The City of Davis reports on its NPDES permits to the Central Valley Regional Water Quality Control Board.

Storm drain -- means a drainage inlet, corresponding conveyance facilities and systems that carry stormwaters directly to waters of the State or United States.

Stormwater -- means stormwater runoff, snow melt runoff, and surface runoff and drainage.

Storm Water Management Plan -- SWMP is a planning document developed to address stormwater quality within the City's jurisdiction. The SWMP will address a wide variety of activities conducted within the City that are sources of pollutants in storm water. The City is required, reviewed and approved by the State of California through the Central Valley Water Resources Control Board as part compliance with the requirements of the NPDES Stormwater Discharge Permit. The SWMP has the following seven required elements:

  1. Commercial and Industrial
  2. Illicit Discharges
  3. Construction Activities
  4. New Development and Redevelopment
  5. Municipal Operations
  6. Public Education, Outreach and Participation
  7. Public Agency Legal Authority

Storm Water Pollution Prevention Plan (SWPPP) -- a documented plan to describe a process whereby a facility thoroughly evaluates potential pollutant sources at a site and selects and implements appropriate measures designed to prevent or control the discharge of pollutants in stormwater runoff during construction activities.

Structural Control Measure -- means any structural facility designed and constructed to mitigate the adverse impacts of stormwater and urban runoff pollution (e.g. canopy, structural enclosure). The category may include both Treatment Control and Source Control Measure.

Swale -- A natural or human-made open depression or wide, shallow ditch that intermittently contains or conveys runoff. Can be used as a BMP to detain and filter runoff.

Total Maximum Daily Load -- TMDL is a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards. Water quality standards identify the uses for each water body, for example, drinking water supply, contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use. The Clean Water Act, section 303, establishes the water quality standards and TMDL programs.

Treatment Control Measure -- means any engineered system designed to remove pollutants by simple gravity settling of particulate pollutants, filtration, biological uptake, media adsorption or any other physical, biological, or chemical process.

Waters of the State -- means any surface water or groundwater, including saline waters, within the boundaries of the State of California.

Waters of the United States -- any surface water or groundwater, including saline waters, within the boundaries of the United States.

XeriscapingTM -- An alternative landscaping technique that focuses on water conservation through plant selection and site design.

X-year storm event -- The storm event that has a probability of recurring on average once every X-years based on records from previous years.