Stormwater Management

Jefferson County is responsible for the stormwater quality that drains from property into our storm sewer system and discharges to state waters. Protecting water quality is critical in Jefferson County.

The Federal Water Pollution Control Act Amendments were enacted in 1972. This set of laws and additional amendments is known as the Clean Water Act. The Act gave the Environmental Protection Agency (EPA) authority to establish programs designed to clean U.S. waters and maintain water quality. The EPA delegates its authority to manage and regulate programs to the states. Stormwater Phase II is the latest component of the Clean Water Act. Stormwater Phase II regulations address stormwater discharges from small municipal separate storm sewer systems and construction sites that disturb at least one acre. Jefferson County is the owner of a separate storm sewer system.

Stormwater & Where It Comes From

Stormwater is any precipitation that collects in a natural or constructed storage or transport system following a storm event. For example, during construction of a new building or neighborhood, sites are often cleared and the soil is firmly compacted, which prevents rainfall or snowfall from soaking into the soil. As a result, the rainfall streams along the surface of the ground. This is stormwater runoff. 

After construction activities, impervious areas such as roads, roof tops, parking areas, and sidewalks prevent infiltration of moisture from rain and snowfall, thus increasing natural stormwater runoff. This runoff can be too much for the existing natural drainage systems to handle. As a result, natural drainage systems are often altered to rapidly collect runoff and convey it away (using curb and gutter, enclosed storm sewers, and lined channels). The stormwater runoff is then discharged to downstream waters such as streams, reservoirs, and lakes.

Managing Stormwater Quality

Jefferson County is responsible for the stormwater quality that drains from property into our storm sewer system and discharges to state waters. As part of the Stormwater Phase II Regulations, Jefferson County was required to apply to the State of Colorado Department of Public Health and Environment for a Municipal Separate Storm Sewer System (MS4) Permit. The five-year permit was granted to Jefferson County in March 2003. Under this permit Jefferson County is mandated to improve the quality of stormwater. The MS4 Program Description Document (PDD) is available to the public for review and comment.

Jefferson County is required to implement six minimum control measures over the permit period which includes:

• Public Education and Outreach
• Public Participation and Involvement
• Illicit Discharge Detection and Elimination
• Construction Site Runoff Control
• Post Construction Site Runoff Control
• Pollution Prevention/Good Housekeeping

Impervious Areas & Water Quality

Water that soaks into the soil is naturally filtered and cleaned. Water flowing on the surface of developed property picks up pollutants such as sediment, oil, and salts from roads and parking areas, fertilizer from lawn runoff, and bacteria from property where animals are kept. The effect of one property on the quality and quantity of stormwater runoff may seem insignificant. However, the cumulative impact from hundreds of thousands of properties across the state can negatively affect our water quality. And keep in mind: much stormwater runoff, after it enters lakes, streams, and reservoirs, or soaks into the ground, eventually becomes drinking water for downstream communities. This is one reason protecting water quality is so critical in Jefferson County.

Impervious Areas & Water Quantity

Impervious area creates a barrier to water soaking into the soil and prevents the rainfall or snowfall from recharging ground water supplies in that area. This reduces the amount of ground water that is available to well water users and increases the downstream surface water flow.

Additional Information

Have you seen any suspicious dumping into a storm drain? Have you noticed any suspicious outflow from a culvert or storm sewer? Please contact Planning and Zoning if you have questions about stormwater quality.