As a primary part of the District’s preventive maintenance plan, a high velocity pipeline cleaning program is used to maintain 190 miles of sewer lines. Based upon system performance evaluations, pipeline cleaning is performed on a 3-year system wide cleaning schedule. In addition to cleaning the lines, the cleaning crew provides an observation and analysis of the line condition. Physical observation of the type and amount of debris in the line or the amount of grease or roots generated by the cleaning helps determine if and when an increase in the cleaning schedule is warranted. It also helps to determine if the individual line segment(s) should be placed on the “problem line” list.
Problem lines are defined as a particular line segment that has a likelihood of plugging due to more rapid buildups of debris, grease or roots. The type of problem affecting the line segment will dictate the type and frequency of cleaning. In general, problem lines are addressed on an annual basis. Lines that experience high root growth or grease accumulations are placed on a six-month schedule. The District uses several different methods for keeping problems lines clean and flowing properly. High velocity pipeline cleaning is used for debris and light to moderate grease problems. Hydraulic root sawing is used for moderate to heavy grease and light to moderate root problems. Mechanical rodding is used for the most severe accumulations of grease and roots. Pipeline segments experiencing high root growth problems may also be placed on a chemical root foaming program.