Abstract
Project Overview The Upper Northwest Interceptor Sections 5 and 6 (UNWI 5/6) are part of a regional gravity sewer system designed and constructed to relieve the capacity deficiencies in the north eastern portion of Sacramento County. Sacramento Regional County Sanitation District (SRCSD) defines an interceptor as any pipe that conveys greater than 10 million gallons per day (mgd) of sewage. The UNWI system conveys flows to the regional wastewater treatment plant in Elk Grove, located in the southwestern portion of Sacramento County. UNWI 5/6 is a 5.5-mile gravity interceptor located along Elkhorn Boulevard starting at Don Julio Boulevard and terminating at Cherry Lane to the west. The interceptor diameter is 48 and 66-inch to convey an ultimate flow of 80.6 mgd. Currently, the interceptor conveys much less flow than 80.6 mgd and interim flows were considered during design. This project also includes the design of two hydraulic control structures to channelize and direct flow during low flow periods in the near-term and redirect flow during periods of maintenance or high flow. This paper will describe the hydraulic design criteria and process for design of UNWI 5/6 project components including the interceptor and hydraulic control structures. This interceptor project has been constructed and is currently in operation.