The Water and Sewer Authority of Cabarrus County (WSACC) operates and maintains a regional sewer system including 116 miles of interceptor sewers serving multiple municipal entities in Cabarrus County.  One of the oldest interceptors in the WSACC system is the Kings Grant interceptor located along the Rocky River.  This interceptor is located near Concord Mills and Charlotte Motor Speedway in a portion of Cabarrus County experiencing significant growth.  The Kings Grant Rocky River Parallel Interceptor project was required to provide sewer capacity for this growth.

Willis Engineers provided design, regulatory and construction services for the Kings Grant Rocky River Parallel Interceptor project.  The project consisted of over 24,000 linear feet of 54 and 48-inch interceptor including a 330-foot long 66-inch diameter tunnel located under Interstate 85.  The project included numerous challenging conditions including very high water table, large areas requiring rock removal and areas of beaver impoundments.

During the design process, Willis Engineers worked with various pipe manufacturers to determine the best pipe material for the varying ground conditions while providing corrosion protection.  The project was bid with lined ductile iron pipe and fiberglass reinforced polymer pipe as alternatives.  The contractor selected for the project chose to use fiberglass reinforced polymer pipe.  All manholes on the project were also required to have a corrosion resistant liner.