A 1987 amendment to the Federal Clean Water Act required implementation of a
two-phase national program to address storm water runoff and its associated
pollutants. Phase I regulated construction sites larger than five acres, 10
categories of industrial facilities and major metropolitan cities. In Minnesota, the cities affected by Phase I of the storm
water program were Minneapolis and St. Paul.
In 2003, Phase II was implemented to include construction sites greater than one acre and smaller municipalities. Farmington is required to follow National Pollutant Discharge Elimination System (NPDES) Phase II requirements since the population is over 10,000 (based on census data). Under Phase II operators of small MS4s needed to obtain authorization from the Minnesota Pollution Control Agency (MPCA) to discharge stormwater runoff to surface water. The permit is designed to prevent items considered pollutants from being washed by stormwater runoff into the municipal storm sewer and then discharged from the storm sewer into local waterbodies.
The MPCA reissued the NPDES Phase II permit in August 2013, requiring municipalities to submit a revised application and Storm Water Pollution Prevention Program (SWPPP) document. A complete version of the combined application and SWPPP and NPDES permit are available here.