The City of Omaha has committed to a Long Term Control Plan (LTCP) for controlling combined sewer overflows that affect the tributaries of the Papillion Creek and Missouri River. This LTCP is being developed by CH2M Hill with additional consultants assigned to specific basin area studies.
The City’s combined sewer system is divided into ten drainage basins which are comprised of approximately 800 miles of sewers in a 51 square mile area. The ten drainage basins are further described as either “complex” or “less complex” based on their CSO volume. The combined area includes a total of 29 permitted CSO points.
The overall project included characterizing all sewers 24-inch and larger developing a hydraulic model to verify existing and future sewer capacities, developing alternatives to relieve existing bottlenecks and remove existing overflows, verify preliminary facility siting; constructability; and operability, and ultimately providing a report identifying the required facilities and improvements to the sewer system along with estimated costs; proposed funding strategy, and implementation schedule
TREKK was responsible for concurrently conducting field reconnaissance efforts for nine of the City’s ten basins over a seven month period. The five complex basins involved in the study were Minne Lusa, Ohern/Monroe, Leavenworth, Saddle Creek and the South Interceptor, while the four less complex basins studied were Bridge Street, Cole Creek and Papillion Creek South and Papillion Creek North. The less complex basins included additional I/I studies of the separated areas. These studies were to determine the effect of I/I on the separated systems and included flow monitoring, manhole inspections, smoke testing and CCTV inspections.
Work consisted of conducting field inspections (Confined Space Entry and topside) of over 600 diversion structures, outfalls and manholes. RTK GPS surveys (Leica 1200) of the rim elevations for all field inspections were attempted. Approximately 120,000 linear feet of sewer within the CSO Basins were smoke tested. TREKK performed CCTV inspection of approximately 40,000 linear feet of sewer. Flow monitoring in the basins involved the use of 18 meter sites and 7 rain gauge sites were data collection occurred for a period of 90 days. All field data collected on field forms was entered into MS Access databases which were subsequently imported into the City’s InfoNet sewer model. TREKK assisted in the preparation and submittal of the draft and final basin consultants’ reports.
