Using a Phased Approach to Plan for Condition Assessment of a Lime Slurry Force Main Using In-Line Inspection Technology

The City of Columbus Department of Public Utilities (DPU) operates three water treatment facilities, including the Hap Cremean Water Plant (HCWP) and the Dublin Road Water Plant (DRWP). The HCWP and DRWP treat surface water with a variety of processes including lime softening. The waste lime slurry from this process is pumped to a waste quarry through a 17-mile long 12-inch diameter ductile iron (DI) force main for the HCWP and a three-mile-long 14-inch diameter DI force main for the DRWP. There have been some failures on the pipelines in the past, some due to corrosion impacts, which have resulted in lime slurry releases to waters of the State. Due to these releases, the Ohio EPA directed the City to take the proper actions to prevent further releases of lime slurry from the main. The City contracted with Brown and Caldwell to conduct an inspection of the pipelines to determine condition and to identify deteriorated sections. Brown and Caldwell proposed the use of the See Snake electromagnetic in-line inspection tool from PICA, Inc., a division of Russell NDE. Like most utility owners, the City is wary of inserting tools into pipelines that may already be weakened by corrosion. Brown and Caldwell and PICA have developed a three-phase program to introduce the inspection technology to the City and to carefully manage the risks to the pipeline. The first phase in the program is the inspection of a similar sized water main. A 1,700 foot segment of 12-inch DIP water main was selected due to its ease of access and potential for minimal disruption to service. With the confidence developed from a successful inspection in Phase One, a second pilot phase would be initiated to perform an in-line inspection on a selected segment of the lime slurry line. The goal of Phase Two was to prove that the approach is feasible in the slurry system and to further build confidence in the technology and approach. Phase Three would entail the inspection of the remainder of the pipeline. The paper will describe the planning that went into the preparation for the inspections, the results of the inspections, and a discussion of the lessons learned.