Protecting Public Health and the Environment.
Stormwater is rain or melting snow that does not immediately soak into the ground. Stormwater runs off of land and hard surfaces such as streets, parking lots, and rooftops, and picks up pollutants, such as fertilizers, dirt, pesticides, and oil and grease. Eventually, stormwater soaks into the ground or discharges to surface water (usually through storm drains), bringing the pollutants with it.
Construction activities that disturb 1 acre or more of land, including clearing, grading, and excavation activities; industrial activities specifically listed by the US Environmental Protection Agency (EPA); and municipal separate storm sewer systems (MS4), which are a city's or town's storm drains are considered point sources of pollution (i.e., a source of pollution that comes from a discrete pipe or other point) and require coverage by a National Pollutant Discharge Elimination System (NPDES) stormwater permit.
In Idaho, stormwater is channeled to rivers, streams, or lakes, or underground to ground water (it is also channeled to the ocean in coastal areas of the United States). It is not cleaned at a wastewater treatment plant. This means all of the pollutants carried by stormwater are also channeled to these water bodies. If you pour something down a storm drain or in a gutter, it is just as though you poured it directly into your favorite swimming hole or fishing spot, or even into the source of your drinking water.
Federal, state, and local government agencies; business and industry; and individual land owners all share responsibility for stormwater management in Idaho.
EPA, Region 10, is the NPDES permitting authority for Idaho and is responsible for issuing NPDES stormwater permits.
Many communities have stormwater NPDES permits and related stormwater ordinances that impact everyone, including individuals. Stormwater ordinances are designed to minimize the environmental threat to Idaho's rivers, lakes, and streams by prohibiting certain activities that would directly discharge into stormwater sewer systems. For more information about local ordinances in your community, contact your local public works department, highway district, or county.
Businesses, industry, and land owners are responsible for stormwater runoff from their property and may need to obtain a stormwater NPDES permit from EPA and/or comply with their city's municipal stormwater NPDES permit. Compliance with a stormwater permit may require the use of stormwater best management practices (BMPs); their use is recommended although not required.
A total maximum daily load (TMDL) is a water quality improvement plan that provides a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards. TMDLs are calculated for surface water bodies that do not meet water quality standards; their purpose is to improve poor water quality. Since stormwater can discharge pollutants to streams, lakes, and rivers, stormwater discharges must be consistent with the requirements of a TMDL that has been developed for a particular water body.
If a TMDL has been established for the stream, lake, or river where stormwater will discharge, the stormwater discharger should contact DEQ to determine if there are specific TMDL stormwater requirements. Following BMPs from the Catalog of Stormwater Best Management Practices for Idaho Cities and Counties described below is generally sufficient to meet TMDL requirements, but it is best to discuss BMPs with DEQ before implementing if a TMDL is in place.
A BMP is a technique of preventing or reducing pollution that has been determined to be an effective, practical method of doing so in a specific situation. Stormwater BMPs are used in Idaho to help prevent stormwater runoff from polluting Idaho's streams and rivers. DEQ has developed a Catalog of Stormwater Best Management Practices for Idaho Cities and Counties to provide technical guidance for the selection and site design of stormwater BMPs.
In general, the following two types of BMPs for stormwater pollution control exist:
Each of us can help prevent stormwater pollution through simple actions we take every day:
Wastewater Engineering ManagerChas Ariss, P.E.DEQ State OfficeWater Quality Division1410 N. HiltonBoise, ID 83706(208) firstname.lastname@example.org
Nonpoint Source PollutionPollution Prevention for CitizensStorm Drain Marking ToolkitStormwater NPDES Permits