Lake Fordyce Dam

Gregg Drilling was contracted by Gannett Fleming and PG&E to conduct a geotechnical investigation at the Lake Fordyce Dam for a seepage mitigation project. The project will involve removal of poorly controlled fill at the upstream toe and replacement with engineered fill. Construction of a concrete plinth and grout curtain tied into bedrock and placement of a PVC membrane will used to control future seepage. Geotechnical investigation of upstream and downstream areas for rockfill was needed for further determination. 

Challenges:

• S Vertical and angled borings up to 30 degrees
• Depth of borings ranged from 50-210 ft below ground
• Steel conductor casing to be used and seated into rock 

Highlights:

•  Heliportable drill used on (7) exploratory borings in upstream area with an additional (2) in downstream quarry
• HQ or PQ sized triple barrel wireline coring
• Optical and acoustic televiewer and P-S suspension logging 

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