Offshore Drilling for Intake System
Southern Nevada Water Authority (SNWA) investigated the construction of a large diameter water-supply tunnel from their existing water treatment plant into Lake Mead’s Boulder Basin. The new intake would extend 12,000 to 16,000 feet into Lake Mead, and provide critical drought protection and water quality improvements for the rapidly growing Las Vegas region. The primary purpose was to replace the existing intake should the water elevation of Lake Mead drop below an elevation of 1050 feet above sea level.
Southern Nevada Water Authority
MWH and CH2M HILL Joint Venture
Crux provided drilling and geophysical services to locate and design the new intake system, completed in multiple phases of land-based and offshore drilling. The land-based program consisted of HQ3 borings drilled to depths of 600 feet on or near Saddle Island. The offshore program consisted of borings drilled depths of 300 feet below mudline in water depths ranging from 10 to 350 feet.
To mitigate environmental impacts within the National Recreation Area, Crux successfully contained drill fluids and spoils; utilized specialty fueling systems; and developed Best Management Practices. Additional challenges included severe weather and poor geologic conditions, which were especially impactful during offshore drilling. Crux overcame these difficult conditions by developing a multistring casing system to limit buckling of drill strings and allow for drill fluid recirculation.
In-situ testing was completed by Crux Oriented Borehole Logging (COBL), including optical and acoustical televiewer; natural gamma; temperature profile; permeability testing; and dilatometer testing. Offshore drills were equipped with data loggers to record penetration rates, drill pressure changes and other drilling parameters.