Admin Order 58-20-26 - Laserfiche WebLink

Home Browse Search

Teri Higgins June 30, 2016 Page 10 Terry Street The pump station caisson is divided into wet‐ and dry wells with a reinforced concrete wall separation. The pump station superstructure corners overhang the caisson; it is unclear whether they are cantilevered or on small foundations. If they are supported on foundations, differential settlement could damage the building. The pump station wood frame superstructure beam and roof connections should be evaluated. The pump station was designed prior to the seismic rezoning in the 1990s. Wood frame structures with large openings are vulnerable if connections are inadequately detailed. Pump discharge lines and the discharge header lateral support appear to be inadequately braced and should be checked by a structural engineer. Tadmore The pump station pipe material is unknown. If 1968 vintage piping could be cast iron, which is brittle and vulnerable in earthquakes. Manhole and vault structures and piping appear adequate to resist seismic loading. Submersible pumps anchorage dependent of manufacturer’s design. Historically these have not failed in earthquakes. This design is older than the others and as a result is more vulnerable to failure. Check with the pump station manufacturer on the stability of the pump anchorage. Division Avenue Manhole and vault structures and piping appear adequate to resist seismic loading. Submersible pumps anchorage dependent of manufacturer’s design. Historically these have not failed in earthquakes 6.Mitigation Recommendations for Collection/ Conveyance Sewers and Pump Stations This section recommends action items to minimize the impact of a CSZ Earthquake on the Eugene wastewater system. 1.Geotechnical Hazard Parameters ‐ Develop a better understanding of the probabilities and PGDs associated with liquefaction and landslide within the City. Pipeline performance in earthquake is controlled by the geotechnical hazard environment. The DOGAMI maps used for this project designated liquefiable areas along the Willamette River as having a low probability of liquefaction occurring (5 percent or less), and if it did liquefy, PGDs would be 4‐inches or less. The DOGAMI maps showed pockets of moderate liquefaction in southern Eugene, some areas with the probability of liquefaction being as high as 15 percent with PGDs as high as 40 inches. In the same areas the landslide probabilities are as high as 30 percent with PGDs exceeding 100 inches. These geotechnical earthquake hazard parameters strongly influence the expected performance of the sewer system. 2020 Eugene Wastewater Master Plan Appendix A-10