Managing Stormwater at Industrial Facilities in Arizona

In Arizona, there are three regulatory paths for stormwater discharge at industrial facilities:

  1. Tribal lands, where all stormwater discharges are regulated by USEPA under their federal permit system.

  2. Stormwater discharges into municipal separate stormwater systems – either large or small.  These discharges must meet the multi-sector industrial permit programs, which are implemented by the state, but they are also subject to pollution prevention programs and reporting as required by various municipal codes.

  3. Stormwater discharges into other receiving bodies.  These discharges must meet only the state multi-sector industrial general permit requirements.

This program falls under the National Pollutant Discharge Elimination System (NPDES) stormwater program of the national Clean Water Act, as applicable to the state and local jurisdiction where the subject property is located.  States adopt general permits that cover a wide range of industrial and business activities.

A permit must be obtained for facilities where stormwater is considered “contact stormwater”, from either the state or the city, depending on where the stormwater is discharged.  However, some industrial activities are not covered or exempted under general permit standards.

Non-contact stormwater flows on an industrial property means stormwater that does not come into contact with industrial operations or loading/unloading activities.

For facilities that are not planning discharge pollutants into the stormwater system, there are two ways to proceed:

  1. The No Exposure Certification.  This certifies that all industrial activities are protected by a storm resistant shelter and that no pollutants are being discharged due to no exposure. The certification is signed by the facility owner and is supported by answering 11 questions, all of which must be answered “no” in order to qualify for the exemption, typically by inspecting the facility and documenting the outfall configuration, facility activities, potential sources of regulated pollutants, and any protections that exist on site.  It’s also important to check the state regulations to ensure that the facility is covered under the Limitations of Coverage section of the general industrial permit.

  2. Zero Discharge.  There is a concept called “zero discharge,” which is not in the regulations but is used to support the case to the regulatory agency that an industrial facility is not subject to any of the stormwater regulatory requirements.  The Zero Discharge concept does not have any regulatory definition, but essentially certifies that the facility doesn’t meet the criteria for discharge of a pollutant.  Some of the city stormwater management plans have requirements that apply to a claim of zero discharge, including having it certified by a registered professional engineer or professional geologist.  A zero discharge certification should be supported by inspecting the facility and documenting the outfall configuration, facility activities, potential sources of regulated pollutants, and any protections that exist on site.