65B - PROPOSED WATER AND SEWER RATE ADJ

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City of Santa Ana, CA I SEWER RATE STUDY Quick Structural Rating (QSR) Analysis The most current and reliable sewer main condition assessment data available from within the City's GIS database is the CCTV ratings results for QSR. These values provide actual internal pipeline conditions observed at the time of the inspection. The City's QSR values are assigned to individual sewer pipe segments following the evaluation of CCTV pipeline inspections. These ratings are based on the Pipeline Assessment and Certification Program (PACP) coding systems developed by NASSCO. The grading system only considers internal pipe conditions (defects) observed from the CCTV inspection. The PACP Quick Rating is a four - character score expressing the number of occurrences of the two highest severity grades. No. of Worst Defects No. of 2nd Worst Defects rL1 rA_j QSR: 5 2 3 6 Worst Defect ~2 d Worst Defect These scores are typically used in evaluating the overall grade of the entire pipe segment using one of two methods. Raw QSR Grading Method For simplicity, the first method only considers the first (highest) grade rank. It uses only the left -most digit of the four - character PACP grade for the pipe segment grade. The mechanisms and rates of pipe deterioration are highly dependent on local conditions and operational history. However, the following general guidelines (from NASSCO PACP, 2001) is provided as a starting point: Grade 5: Pipe has failed or will likely fail within five years, immediate attention recommended Grade 4: Pipe will probably fail in 5 to 10 years, in poor condition Grade 3: Pipe may fail in 10 to 20 years, in fair condition Grade 2: Pipe unlikely to fail for at least 20 years, in good condition Grade 1: Failure unlikely in the foreseeable future, in excellent condition Grade 0: No defects observed Null: no rating data provided in the City's GIS database This method is acceptable if you assume that the worst defect (i.e. weakest link) defines the structural condition of the overall pipe segment. It also ignores the frequency that these defects were observed or any lower grade defects. In the "5236" example above, the pipe would receive a Raw QSR Grade of S. By analyzing the City's GIS data for QSR observations, several summaries were made. Figure B 12 shows the percent of total sewer system (by pipe length) listed by each of the QSR Ratings (graded 0 to 5). As the graph shows, 22 percent of all pipeline records have no QSR data and 50 percent have a grade of zero. Of most concern are the highest grade pipes (Grades 3 -5). Combined these represent about 15 percent of the system. BLACK & VEATCH I Appendix B: Sewer CIP Prioritization Process 65B -240