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1. What is stormwater and where does it come from?

Definition

Stormwater is any precipitation that collects in a natural or constructed storage or transport system following a storm event.

Causes

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, rooftops, 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.

Solutions

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.

2. Why must the City of Shelbyville manage stormwater quality?

The City of Shelbyville is responsible for the stormwater quality that drains from properties into our storm sewer system and discharges to state waters.

Municipal Separate Storm Sewer System

As part of the Stormwater Phase II Regulations, the City of Shelbyville was required to apply to the State of Kentucky Division of Water for a Municipal Separate Storm Sewer System (MS4) Permit. The five-year permit was granted to the City of Shelbyville in March 2003. Under this permit, the City of Shelbyville is mandated to improve water quality from our storm system or MS4.

Control Measures

The permit requires the City address six areas or control measures. The six control measures are:

• Construction Site Stormwater Runoff Control
• Good Housekeeping for Municipal Operations
• Illicit Discharge Detection and Elimination
• Post-Construction Stormwater Management, and Pollution Prevention
• Public Education and Outreach
• Public Involvement and Participation

Several tasks and activities have been identified within each control measure. The ultimate goal of each control measure is to reduce the impact stormwater has on our local receiving streams.

3. How does impervious area affect 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:

• Bacteria from properties where animals are kept
• Fertilizer from lawn runoff
• Sediment, oil, and salts from roads and parking areas

Effects of Poor Water Quality

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 the City of Shelbyville.

4. How does impervious area affect water quantity?

Impervious area creates a barrier to water soaking into the soil and prevents the rainfall or snowfall from recharging groundwater supplies in that area. This increases the downstream surface water flow.

5. Do you need additional information?

Have you seen any suspicious dumping into a storm drain? Have you noticed any suspicious outflow from a culvert or storm sewer? Do you have questions on stormwater quality? Please contact Jennifer Herrell (Municipal Separate Storm Sewer System (MS4) Coordinator / City Engineer) at 502-633-1094.