Industrial facilities are a major source of stormwater runoff, especially where outdoor operations, materials, and equipment are exposed to rain or snowmelt. Without proper controls, stormwater can carry pollutants – such as oil, metals, sediment, and chemicals – into storm drains and nearby waterways, degrading water quality and violating regulatory standards.
In Iowa, most industrial stormwater discharges are regulated under the National Pollutant Discharge Elimination System (NPDES) through General Permit No. 1 or General Permit No. 3, administered by the Iowa Department of Natural Resources (IDNR).
General Permits No. 1 & 3
General Permit No. 1 covers stormwater discharges associated with industrial activity from manufacturing, trucking, transportation, mining, and related operations.
General Permit No. 3 covers discharges from asphalt plants, concrete batch plants, rock crushing operations, quarries, and sand and gravel facilities.
Both permits require the development and implementation of a Stormwater Pollution Prevention Plan (SWPPP). This plan must:
- Identify potential sources of stormwater pollution
- Describe site-specific control measures and best management practices (BMPs)
- Outline inspection, monitoring, and maintenance procedures
Facilities discharging through a Municipal Separate Storm Sewer System (MS4) may also need to coordinate with local permit holders for additional requirements.
Stormwater pollution prevention plans (SWPPPs)
A SWPPP is a living document that helps industrial facilities prevent pollution, reduce runoff, and comply with permit conditions. While the specific content may vary by site and industry, core elements include:
- Site description and drainage map
- Inventory of materials and activities exposed to stormwater
- Description of all structural and non-structural BMPs
- Routine inspection and maintenance procedures
- Spill prevention and response plans
- Employee training and documentation
Click here to download the EPA’s SWPPP Template.
Good housekeeping practices
General Permit No. 1 and No. 3 require industrial facilities to implement good housekeeping as a foundational pollution prevention strategy. These practices focus on proper material handling, storage, waste management, and maintenance to minimize exposure of pollutants to stormwater.
Common good housekeeping practices at industrial sites include:
- Covered storage areas for raw materials, products, and waste to prevent contact with precipitation.
- Secondary containment for chemicals and fuels to prevent leaks or spills from reaching drains.
- Spill response kits and procedures readily available at all storage and handling areas.
- Routine sweeping of paved areas to remove debris, sediment, and materials before they enter stormwater systems.
- Designated wash areas for equipment and vehicles, with runoff directed to containment or treatment systems.
- Proper waste disposal and covered dumpsters with intact lids.
- Visual inspections and maintenance logs for tanks, valves, storage areas, and loading zones.
- Training for employees on housekeeping and spill prevention procedures.
These practices not only reduce the risk of violations but also protect long-term site infrastructure and improve operational safety.
Additional resources
EPA has created a series of fact sheets for the 29 industrial sectors that are currently regulated. Each fact sheet describes the types of facilities included in the sector, typical pollutants associated with the sector, and types of stormwater control measures used to minimize the discharge of the pollutants.