127.29 Stormwater

Provisions of the Federal Clean Water Act and related state rules and regulations require a municipal separate storm sewer system (MS4) permit when the facility serves a population of 1,000 or more within an urbanized area or are located outside an urbanized area serving a jurisdiction with a population of at least 10,000 and a population density of 1,000 people per square mile or more. Furthermore, a municipal separate storm sewer means a conveyance or system of conveyances including roads and highways with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, paved or unpaved channels, or storm drains designated and utilized for routing of storm water. MoDOT has an MS4 general permit, obtained from the Missouri Department of Natural Resources (MDNR). It requires MoDOT develop and adhere to a Storm Water Management Plan (SWMP) comprised of six minimum control measures (MCMs) listed below.

1. Public Education and Outreach

2. Public Participation and Involvement

3. Illicit Discharge Detection and Elimination

4. Construction Site Runoff Control (This measures covers our existing Pollution, Erosion and Sediment Control Program.)

5. Post Construction Runoff Control

6. Pollution Prevention/Good Housekeeping

See 10 CSR 20-6.200.

Illicit Discharge Detection and Elimination

An illicit discharge is defined by MDNR (10 CSR 20-6.200) as a discharge of pollutants to a Municipal Separate Storm Sewer System (MS4) that is not comprised entirely of stormwater and is not authorized under the NPDES permit. MoDOT is an MS4 statewide and holds a general state operating permit.

Additionally, an illegal connection is a pipe or other conveyance that has illegally been connected to MoDOT’s MS4. See additional information at EPG 127.25.8.3.2 System Attachments by Others.

Sources of illicit discharges are spills from roadway accidents, sanitary wastewater, effluent from septic tanks, improper oil disposal, laundry wastewaters, improper disposal of auto and household toxics, etc. See EPG 127.25.8.3.1 Industrial and Domestic Waste Waters on Right of Way and EPG 127.25.8.3.2 System Attachments by Others.

MoDOT is authorized to discharge the following non-stormwater sources provided that the permitting authority has not determined these sources to be substantial contributors of pollutants to the permittee’s MS4 that require a separate permit:

• Landscape irrigation
• Rising ground waters
• Uncontaminated ground water infiltration
• Uncontaminated pumped ground water
• Discharges from potable water sources
• Foundation drains
• Air conditioning condensation
• Springs
• Water from crawl space pumps
• Footing drains
• Lawn watering
• Flows from riparian habitats and wetlands
• Street wash water
• Bridge wash water
• Discharges or flows from emergency firefighting activities
• Individual residential car washing
• Dechlorinated residential swimming pool discharges