The Iowa Hill Pump Storage Project is a Sacramento Municipal Utility District (SMUD) project located in El Dorado County. The proposed facility would pump water 1,200 feet uphill when power is available and let it flow downhill to generate electricity when needed.
SMUD, Jacobs Associates, Carlton Engineering, Crux Subsurface, Inc.
Crux was selected to provide core drilling and sampling, insitu testing and instrumentation. Two borings provided geotechnical data for the construction of an underground pump house, and a third provided information regarding rock quality at the proposed storage pond area. Geotechnical conditions were challenging, but the sites allowed for access by track-mounted drill rig.
The first two borings were 10-degrees sub horizontal, and drilled to depths of 2,002 and 1,473 feet. Packer testing and hydraulic fracturing were completed in both, and Crux performed optical borehole imaging (OBI) the full length of each hole. Testing and OBI activities were challenging due to the poor soil conditions in the area. Both borings successfully stayed within deviation requirements and reached their targets without the need for downhole corrections.
The third boring was vertical and drilled to 1,487 feet. Packer testing and hydraulic fracturing were performed, and OBI was completed the full depth of the hole. Upon the completion of imaging activities, Crux installed three permanent vibrating wire piezometer transducers at varying depths before grouting the hole. Water inflow was experienced, requiring pressure grout using a nitrogen packer system at numerous intervals for successful abandonment.