Murrells Inlet residents gave notice to Georgetown County last week that they are ready to go to court to enforce compliance with federal regulations that require the county to improve water quality in the estuary.

If that happens, it will be the first action in the state to challenge compliance with federal permits for “municipal separate storm sewer systems,” known as MS4s, according to Amy Armstrong, executive director and chief counsel of the S.C. Environmental Law Project, which is representing the citizens group Preserve Murrells Inlet and Murrells Inlet Seafood.

Georgetown County is one of 70 small MS4s in the state that operate under federal permits administered by the state. The Department of Health and Environmental Control notified the county last April that an audit of its MS4 program found deficiencies. That included the failure to show that it had implemented a 2014 plan to reduce the amount of pollutants entering the Murrells Inlet watershed.

“Georgetown County is not some sort of outlier. We’ve seen it in other places, but not as well documented,” Armstrong said.