The state operates under the Wyoming State Stormwater Management Program, through NPDES, WYDES permit, WYR04-0000 (issued under provisions of WY Water Quality Rules and Regulations (WYRR), Chapter 2 Section 6(j)(i)(C)). There is a phase II MS4 general permit to address stormwater runoff from new development and redevelopment projects that "disturb greater than or equal to one acre, including projects less than one acre that are part of a larger common plan of development or sale, and discharge into the small MS4." The standards apply statewide to regulated MS4s with exception of Wind River Indian Reservation.
“Permit specifies only that permittees must develop, implement, and enforce a program that ensures that controls are in place that would prevent or minimize water quality impacts from development and redevelopment. The MS4 operator is expected to develop procedures, ordinances or other regulatory mechanisms that will require, to the extent allowed by state or local law, that BMPs be appropriately designed and planned, and provide for enforceable operation and maintenance by the owner/operator.”