The third phase of the North Coast System Rehabilitation Project in Santa Cruz, California, required upgrading approximately 3.5 miles (5.6 kilometers) of raw water pipeline 24 inches (0.6 meters) in diameter.
This included the crossing of Lombardi Gulch, a sensitive riparian area inhabited by the threatened California red-legged frog.
The project became more urgent when the existing water main suffered a premature failure during a severe drought. The main was leaking at a rate of 500,000 gallons (1,900 cubic meters) per day.
Mott MacDonald was selected to provide geotechnical engineering, design, and construction engineering support services for the project, which included four horizontal auger borings beneath California State Route 1 and a crossing beneath the stream environment of Lombardi Gulch, using horizontal directional drilling (HDD).
Bid and completed as an emergency project, Phase 3 of the North Coast System Rehabilitation made strategic use of trenchless technology to minimize the environmental impact on wetlands, creeks, and environmentally and/or culturally sensitive areas.
The project helped restore an important source of drinking water during historic drought conditions.