The Lowell (Mass.) Regional Wastewater Utility sewer separation program and remote gate control system upgrades had significantly reduced combined sewer overflows (CSOs) to local waterways.To further reduce CSOs, operators at the 32 mgd Duck Island Wastewater Treatment Facility wanted to make full use of the 48- to 120-inch reinforced concrete interceptor system for storage of wet-weather flows.Because the pipes are fairly flat, ultrasonic level sensors in diversion stations throughout the interceptor system enabled operators to extrapolate levels for upstream pipe segments. But without a true understanding of levels in all interceptor segments, the utility lacked confidence when establishing set points
