Contractor Rethinks Pipeline Bore, Saving $10 Million

Garney Construction’s creative approach proves to be a ‘win-win’ for Colorado water project
Contractor Rethinks Pipeline Bore, Saving $10 Million
In March 2014, a 105-inch-diameter tunnel boring machine was lowered into a vertical launch shaft — the starting point for the SDS pipeline's mile-long tunnel.

Using a three-in-one approach, Garney Construction has successfully bored a single tunnel through rock and beneath an interstate highway, two rail lines and a creek, as part of the Southern Delivery System (SDS) water project in Colorado.

The mile-long dig was the critical piece in a 50-mile pipeline which will transport freshwater from the Pueblo Reservoir to Colorado Springs and the nearby communities of Fountain, Pueblo West and the Security Water District. The bore was executed as a design-build contract, taking just over 10 months to complete. Cost was roughly $20 million.

Bill Williams, project manager for Garney, explains that the original design called for three separate bores, coupled with open-cut sections, and would have required extensive dewatering of the creek.

A rewarding alternate

“We submitted an alternate proposal, which grouped all three bores and the surface work into a single tunnel,” he says. The alternate came in nearly $10 million cheaper than the original design and avoided surface disruption and limited the required dewatering to a minimum. Brian Whitehead, project manager for SDS, says the single tunnel approach also ensured protection of environmentally sensitive Fountain Creek.

Additional precautions were taken to eliminate noise that would have bothered neighbors living near the construction site.

“Originally, the plan was to dig from east to west, but that would have put cranes and other equipment very close to ranchers and residents, 24 hours a day,” Whitehead says. To avoid that, plans were changed, and the dig started on the west end where there were no neighbors, and moved east. The only technical difference was that the dig went uphill, from a launch shaft depth of 85 feet, to a receiving shaft depth of 60 feet.

Chewing through rock

Subcontractor Michels Corporation used a 105-inch tunnel boring machine to chew through the rock at a pace of 15-20 feet per day, and a locomotive on tracks carried spoils out of the hole. The waste rock is being put to use for grading throughout the area. The tunnel was shored with a beam and rib system. The pipeline measures 66 inches in diameter, and consists of 32-foot sections of spiral wound carbon steel, lined with concrete and mortar. Joints were welded in-situ.

Williams says the 40-person crew worked two 10-hour shifts per day.

SDS chose the design-build approach to ensure that the engineers and contractors on the job worked closely together, Whitehead says. “We chose this model over design-bid-build because we didn’t want to spend a lot of money upfront on design, without the construction contribution. We wanted harmony and best value.”

Whitehead says water is scheduled to start moving from the reservoir to the communities sometime in spring 2016. The tunnel section of piping was tied into the rest of the pipeline in April. The other components in the water project — pumping stations and a new water treatment plant serving Colorado Springs —are in the process of being completed. Cost for the total project — including the pipelines, pumping stations and water treatment facility — is expected to come in at around $835 million, considerably less than the original estimate of $880 million (2009 dollars) or nearly $1 billion today. The expense is being shared by all four communities.

Good water planning

The new system will help ensure continued water supply for the area. Colorado Springs is one of the few major cities without a river running through it, Whitehead explains. For years, the city has pumped its water eastward from basins in the Rocky Mountains. Now, the water from Pueblo Reservoir — created on the Arkansas River in the early 1970s — can be made available as needed to support continued development and population growth in the region.

Garney Construction specializes in water and wastewater projects for public, private and industrial clients across the United States. The firm has headquarters in Kansas City, Missouri (www.garney.com).

Michels Corporation is an international utility, engineering, design and construction contractor based in Brownsville, Wisconsin (www.michels.us).

Southern Delivery System is a publicly owned municipal project of Colorado Springs Utilities (www.sdswater.org).



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