City of Columbus Division of Sewerage and Drainage
Burgess & Niple (B&N) led a multi-consultant team that evaluated alternatives to address inflow and infiltration (I/I), structural concerns and the long-term sustainability of the sanitary sewer system within the West Fifth Avenue study area. The team, which included Brown & Caldwell and CCI, identified the locations and pathways of excessive I/I and recommended cost-effective improvements to remove I/I from the system.
During the first phase of the project, the team analyzed existing system information and performed detailed field investigations. More than 126,000 linear feet of sanitary sewers were cleaned and inspected. Flow meters and rain gauges also were installed during this phase for monitoring.
A computer hydraulic model of the project area’s sanitary sewers was created using sewer flow data and rainfall amounts collected over a one year period. The model helped identify areas with excessive I/I and sewer lines that do not have sufficient capacity. The results of the CCTV pipe inspection were evaluated based on the PACP Scoring and deficiencies that were identified. Public and private dye testing also was conducted in areas where the model indicated excessive I/I.
The pipe inspection results were used to predict the remaining useful life of the pipe segments. The pipeline remaining useful life was used in conjunction with the hydraulic modeling results to determine a strategy for either pipe replacement or rehabilitation.
The team developed alternatives using a Triple Bottom Line and Life Cycle Analysis approach taking into account environmental, social and direct capital costs. Every catchment in the study area was evaluated using a variety of rainfall derived infiltration and inflow (RDII) remediation methods including: pipe and manhole rehabilitation, private lateral rehabilitation, inline storage, off line storage, drainage improvements and green infrastructure. The storm sewer component included an evaluation of existing storm sewer capacities and the potential for flooding that would negatively impact the sanitary sewer.
At the completion of the project, the B&N team provided the City of Columbus Division of Sewerage and Drainage with a detailed report of the findings and a cost/benefit analysis. The final recommendations include a combination of sewer and manhole rehabilitation, relief sewers, and sewer replacement projects, prioritized to solve I/I and structural problems in the area in the most cost-effective manner.