The storm water discharge from the AHTD Municipal Separate Storm Sewer System (MS4) within the Little Rock city limits is covered by a different permit from the remainder of the state. The City of Little Rock was designated as a medium-size municipality (population size 100,000-250,000) for the purposes of MS4 storm water permitting. Operators of a MS4 system within this area were required to obtain a permit under the National Pollutant Discharge Elimination System Phase I regulations for MS4s, which resulted in the City of Little Rock and AHTD becoming co-permittees with a shared Storm Water Management Plan (SWMP). Storm water discharges by the Little Rock and AHTD combined MS4 system must meet the conditions of the Arkansas Department of Environmental Quality's Permit Number ARS000002.
This permit establishes the responsibilities of each co-permittee with regards to compliance, monitoring, record keeping and reporting permit conditions.