Confidently predicting effectiveness of sewer rehabilitation

NSCC has to date rehabilitated 32 mini-catchments, the rehabilitation effectiveness results are currently available for 14 of these catchments. Each of these mini-catchments has been rehabilitated from the outset with the view towards determining the effectiveness of the rehabilitation undertaken within the catchment. Because of this, the process and data capture has been carefully managed for the last 10 years.

NSCC now have a small database of I/I reduction results that (most importantly) has been collected and measured using the same process and methodology. A model that predicted the percentage reduction in RDII and peak wet weather flow was developed using this data. Confidence intervals were determined to help accommodate the variation in the reduction in I/I not explained by the models. The confidence intervals enable the model outputs to be used with a known degree of confidence.

Also presented within the paper are the measured reductions in RDII% and PWWF from all 14 catchments with rehabilitation effectiveness results; NSCC’s current forecast of the point at which a catchment may be too watertight to achieve a significant reduction in I/I; and a thorough description of how sewer rehabilitation fits into the wider trunk sewer network cost-optimization program.