The federal regulations, in 40 CFR 122.26(b)(14)(i)-(xi), identify 11 categories of stormwater discharges associated with industrial activity required to be covered under an NPDES permit (unless otherwise excluded). One category, Category 10, is construction sites that disturb five acres or more; however, because of the significant difference in the nature of those activities, construction sites are permitted separately.
EPA has issued a Multi-Sector General Permit (MSGP) that addresses stormwater discharges from 29 sectors of industrial activity. The 29 sectors are defined by either the facility’s Standard Industrial Classification (SIC) code or a general description of the facility’s industrial activities. The North American Industry Classification System (NAICS) will eventually replace the SIC system. The U.S. Census Bureau has a conversion table to bridge the two systems. For more information on each of the 29 sectors, view the Industrial Fact Sheet Series for Activities Covered by EPA’s MSGP.
More information about permitting stormwater discharges from construction activities is available. In general, the 10 categories of industrial activities are as follows: