Small Municipal Separate Storm Sewer System (SMS4) Program

York County is designated by the South Caroline Department of Health and Environmental Control (SCDHEC) as one of at least 70 regulated small Municipal Separate Storm Sewer Systems across South Carolina that are required to obtain NPDES permit coverage in order to discharge pollutants into Waters of the State. The federally mandated MS4 designation is based on urbanized areas as determined by the latest census.

As defined by the U.S. Environmental Protection Agency (EPA), a Municipal Separate Storm Sewer System (MS4) is a system of conveyances that are:

Owned by a state, city, town, village, or other public entity that discharges to waters of the U.S.,
Designed or used to collect or convey stormwater (e.g., storm drains, pipes, ditches),
Not a combined sewer, and
Not part of a sewage treatment plant, or publicly owned treatment works (POTW).

TMDL Monitoring and Assessment

York County is required by the MS4 permit to conduct quarterly stream or creek monitoring and assessment of select water bodies across the County. A TMDL, or Total Maximum Daily Load, is the amount of a single pollutant (such as bacteria, nutrients, metals) that can enter a water body on a daily basis and still meet water quality standards established by SCDHEC.

Stormwater Management Plan (SWMP)

York County is also required by the MS4 permit to development, implement and enforce a SWMP designed to reduce the discharge of pollutants to the maximum extent practicable (MEP), to protect water quality, and to satisfy the appropriate water quality requirements of 33 U.S.C. § 1251 et seq. (1972), also known as the “Clean Water Act”. The SWMP shall include supporting ordinances or other regulatory mechanisms that provide the legal authority necessary to implement and enforce the requirements of the SMS4 permit; management practices; control techniques and system, design, and engineering methods; and such other provisions as the State of South Carolina determines appropriate for the control of such pollutants.

Minimum Control Measures

The SMS4 permit also requires that York County develop and implement certain Minimum Control Measures (MCMs) to protect, maintain, and enhance water quality and the environment of York County and the short-term and long-term public health, safety, and general welfare of the citizens of York County. These MCMs include:

York County received its Individual Stormwater Permit on August 1, 2008 from the South Carolina Department of Health and Environmental Control (SCDHEC) with Certificate Number SCR039104.