Admin Order 58-20-26 - Laserfiche WebLink

Home Browse Search

Teri Higgins June 30, 2016 Page 7 Table 4 shows the expected number of repairs when the system under goes the expected permanent ground deformation estimated by DOGAMI. This is not a precise number with a range in the results of minus 50% to plus 100%. The large majority of the failures are in small diameter concrete and PVC/Truss pipe. Many of these repairs are found in the areas with high probability of liquefaction and PGDs in the hills in the southern part of Eugene. Table 4. Expected Gravity Pipe Failure Due to Liquefaction/Lateral Spread (PGD) K 8" or less 10"‐ 12" 15"‐ 20" 21"‐ 30" 36"‐ 48" 54"‐ 72" Total Concrete ‐ assumed bell & spigot 0.7 26 3 2 2 2 0 34 PVC/Truss 0.7 26 1 0 0 0 0 28 Continuously Lined between Manholes ‐ Various Host Pipes, includes HDPE 0.4 2 0 0 0 0 0 3 Transite 0.5 0 0 0 0 0 0 0 Cast Iron/Steel 1.0 0 0 0 0 0 0 0 Clay 1.0 0 0 0 0 0 0 0 Total 54 5 2 2 2 0 65 For pressure pipe, there is a very limited length, so the expected number of failures is two or less. The ALA (for water pipeline fragilities) includes a relationship between leaks and breaks; for PGV related repairs, 20% are estimated to be breaks, and 80% leaks. For PGD related repairs, 80% are estimated to be breaks and 20% leaks. For sewers, it is assumed leaks will result in increased infiltration. Breaks would be related to catastrophic pipe collapse. Applying these relationships, the results are shown in Table 5. Table 5. Estimated Number of Pipeline Repairs and Catastrophic Failures Failure Categories Calculated Leaks Calculated Breaks Calculated Total Estimated Catastrophic Repairs PGV Related Repairs 23 6 29 1 PGD <= 4" Related Repairs 8 31 39 8 PGD > 4" Related Repairs (1) 5 21 26 21 (1) Total Calculated Repairs 36 58 94 30 (1) Repairs in areas with PGDs > 4 in pipe 12” and smaller, located in the southern Eugene hills. 2020 Eugene Wastewater Master Plan Appendix A-7