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City of Santa Ana, CA I WATER RATE STUDY <br />These results support the conclusion that the Cast Iron pipe failure rate is most likely age related. Pre - <br />1930s pipe has an average failure rate of 1.5 breaks per mile; whereas the failure rate decreases lineally <br />through to the 1970s pipe which has a failure rate of 0.75 breaks /mile. Early Asbestos Cement pipe is <br />also showing significant break rates and again a broadly linear pattern which seems to be age related. <br />Fortunately, the bulk of the Asbestos Cement pipe was not installed until the 1970s. <br />Likewise 1970s and 80s vintage Ductile Iron pipe shows a significantly high break rate. This cohort <br />warrants further investigation as pipes of this vintage and material would not be expected to have <br />significant failure rates. No obvious correlations with clay soils which could cause aggressive conditions <br />and accelerated corrosion were found. Any planned condition assessment or opportunistic pipe <br />condition sample collection and analysis should concentrate on this cohort of pipes. Operational <br />conditions in these areas should also be assessed in more detail. <br />Another unexpectedly high failure rate was observed in the 1980s PVC pipes. However, on further <br />investigation it was determined that this anomaly was actually four breaks on the same pipe segment; <br />three on the same day. Also, the "PVC' break records are of lower reliability as some records may reflect <br />the replacement pipe material, not the original failed pipe material. <br />Number of Breaks by Pipe Diameter and Material <br />Table B- 6 and Figure B - 16 indicates the total number of breaks repaired since 1990 on pipe of various <br />diameters. These are listed by the material of the associated main. The break -to -main relationship was <br />established using the same process as described above. <br />Table B- 6: Number of Breaks by Pipe Diameter and Material <br />Diameter <br />AC <br />CI <br />CMLC <br />CYL <br />DI <br />PVC <br />Total <br />Percent <br />4 <br />2 <br />7 <br />9 <br />3.11% <br />6 <br />26 <br />117 <br />2 <br />145 <br />50.17% <br />8 <br />18 <br />50 <br />9 <br />6 <br />83 <br />28.72% <br />10 <br />1 <br />3 <br />4 <br />1.38% <br />12 <br />7 <br />18 <br />5 <br />4 <br />34 <br />11.76% <br />14 <br />1 <br />1 <br />2 <br />0.69% <br />16 <br />1 <br />1 <br />1 <br />4 <br />7 <br />2.42% <br />18 <br />1 <br />1 <br />0.35% <br />20 <br />1 <br />1 <br />0.35% <br />36 <br />3 <br />3 <br />1.04% <br />Total <br />55 <br />196 <br />4 <br />3 <br />19 <br />12 <br />289 <br />100.00% <br />BLACK & VEATCH I Appendix B: water CIP Prioritization Q-, <br />65B -109 <br />97 <br />