The approach developed for Oklahoma City evaluates a total year of simulated rainfall based on historical precipitation patterns. The typical year time series rainfall was used by Oklahoma City to identify an acceptable level of protection and risk. It was also possible to define different levels of protection to different parts of the wastewater collection system and evaluate seasonal collection system performance. This is a robust analysis which uses local precipitation patterns and can be readily duplicated for any geographic location. Most importantly perhaps, it puts the decision of acceptable level of protection and risk firmly into the hands of the wastewater collection system owner.

The Oklahoma City Water Utilities Trust (OCWUT) reconciled several sanitary sewer overflow data sources and performed an informal condition assessment of their wastewater collection system in response to a Request for Information from the U.S. Environmental Protection Agency. Based on the assessment, staff implemented a targeted preventative maintenance program and developed several capital improvement projects for both rehabilitation and replacement and for increasing collection system and treatment capacity. From this process, OCWUT determined that an improved preventative maintenance program was necessary, better organization of the data would provide more accessible data for future analysis and a formalized, electronic method for condition assessment of the collection system would save valuable time and resources. Lastly, OCWUT realized that in-house staff could provide a quick and thorough response on time-constrained regulatory requests due to institutional knowledge of their systems.