Pump & Circumstances

Aurora’s highly complex Prairie Waters project should calm fears of a drought

A $1.1–billion pump, pipeline and purification project will revitalize Aurora’s water system by adding 3.3 billion gal. of annual capacity.

By Dan DeCristoforo

Aurora is taking a big step to keep itself from becoming a dry city.

Water levels in Aurora reservoirs sank to within 26% of empty during the drought year of 2002, a critical level the city is unlikely to suffer again, even in dry spells.

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Led by former Director Peter D. Binney, Aurora Water quickly responded to the most recent drought by launching the ambitious Prairie Waters project to capture water it already owns by virtue of long-standing water rights on the South Platte River. Once recovered, the water will be transported to an advanced purification facility north of Aurora Reservoir.

Prairie Waters, part of a $1.1-billion, 10-year capital improvement project to reinforce the reliability of Aurora’s water system, adds 3.3 billion gal. (10,000 acre-ft) annually to the city’s water supply—a 20% increase. “This idea brings Colorado’s most valuable resource—water—to Aurora’s most valuable asset, our residents,” Aurora Mayor Ed Tauer says. The project is designed to meet Aurora’s water needs through 2020.

Long and Winding Road Water collected by 17 high-capacity alluvial wells drilled by Garney Construction, Littleton, Colo., within 200 yd of the banks of the South Platte River in Weld County is sent first to the North Campus aquifer-recharge-and-recovery basin, then, via 34 miles of pipeline and three pump stations, to the Peter D. Binney Purification Facility. Finally, purified water is transferred from Binney to the Robertsdale Tank and Pump Station for distribution to residential customers.

Binney and Robertsdale are located adjacent to each other on the same site immediately north of Aurora Reservoir near the corner of Powhaton Road and E. Quincy Avenue.

CH2M Hill of Denver designed the North Campus and managed the overall project. MWH Americas Inc., Denver, designed the conveyance system (pipeline), and Brown & Caldwell, Golden, the Robertsdale Tank & Pump Station.

The pipeline was laid in three segments: Segment 1, 68,830 ft, by Reynolds-Tierdael, Denver; Segment 2, 46,566 ft, by S.J. Louis Construction of Texas Ltd; and Segment 3, 49,368 ft, by Garney Construction Inc. Portions of two segments parallel a 14-mile stretch of E-470. Garney Construction built North Campus and Robertsdale; Western Summit Constructors, Denver, did Binney.

Design work began in August 2005, construction in 2007. Construction is expected to wrap up in April, followed by a requisite six-month startup and testing period.

Budgeted for $754.8 million, the Prairie Waters Project will come in well under that figure and be fully operational by October 2010, nearly three months ahead of the scheduled December completion date.

In March, crews broke through the bedrock on the east side of the South Platte River, drilling a 78-in. diameter hole, 260 ft long—the longest waterway crossing of the Prairie Waters project. (Photo courtesy of Aurora Water)

“The $754.8-million figure represents a value-engineering effort that shaved $100 million off our initial budget,” says Dave Marciniak, public involvement representative with Aurora Water. “Included in that figure is a $75-million loan from the Colorado Conservation Board. Other than that, just $426 million in bonds were sold to ensure that any debt incurred would not run higher than absolutely necessary.”

Well Water Marciniak adds that “water collected by the source wells is not South Platte water per se” but naturally filtered water from the alluvial beds below the river bottom. “The level of biological purification achieved in just this first filtration step is remarkable,” he says.

Water is then pumped into the aquifer-recharge-and-recovery basin, a second purifying sand-and-gravel zone at the 200-acre North Campus and recovered by a second series of wells along the basin rim.

The exact number of recovery-basin wells has not been determined, but the program is similar in scope to the river wells with Garney doing the drilling.

Approximately 34 miles of buried pipeline are being installed to transport water from the North Campus to the purification facility near the Aurora Reservoir. Measuring about 60 in. in diameter, the pipeline consists of mortar-lined, urethane-coated steel pipe. (Photo courtesy of Aurora Water)

After being piped from the North Campus to Pump Station 1, west of the river, near Highway 7, the naturally filtered water passes under the South Platte. Forty-five-ft deep pits were dug on opposite banks to allow crews of 10 from BT Construction Inc., Henderson, Colo., working 12-hour shifts to begin drilling the 78-in., 260-ft-long tunnel through impermeable blue claystone beneath the river. Work was completed in just seven days.

“The claystone proved to be fracture-free, a pleasant surprise that gave us a nice, clean hole through which to run our 60-in., urethane-coated water pipe,” says Darrell Hogan, project director with Aurora Water.

In all, 22 tunnels were drilled under different infrastructure components—primarily highways, railways, future utility lines and waterways. Tunneling posed the greatest risks, including the threat of settling roadbeds and breached waterways that could flood the tunnels.

“Our contractors did a terrific job of crossing all obstacles without serious incident,” Hogan says. “In every instance, crossing procedures were identical to those used for the South Platte with casing pulled behind the boring tool. Pipe was then run inside the casing.”

The last segment of pipeline that leads from Smith Road near E-470 down Powhaton Road ties into the state-of-the-art Aurora Reservoir Water Purification Facility. (Photo courtesy of Aurora Water)

Advanced System Water is lifted 1,000 ft by the three pump stations between North Campus and Binney. Forebay tanks at each pump station provide extra storage capacity—9 million gal. in all—in the event of pipeline shutdown and to compensate for pump-rate imbalances between stations.

Two pumps of different capacities will be delivered to each pump station in December for installation. The dual-pump configuration provides flexibility and a 25-million-gal.-per-day capability.

“Prairie Waters is somewhat unique in its use of multistep purification and puts Aurora center stage in the application of advanced water-treatment technology,” Marciniak says. “At Binney, up to 50 million gal. of water, depending on demand, is passed through a succession of 13 treatment buildings. From start to finish, the processing cycles are: softening, chemical pretreatment, ultraviolet disinfection, natural sand-and-gravel filtering and granular activated-carbon adsorption.

“The ultimate goal is to ensure that water from Binney be indistinguishable from the mountain-sourced water stored in Aurora Reservoir.”

The Aurora Reservoir Water Purification Facility will treat up to 50 million gal. of water per day. Located on 80 acres north of the Aurora Reservoir, the facility uses softening, advanced ultraviolet oxidation, filtration and granulized activated carbon adsorption. (Photo courtesy of Aurora Water)

Custom manufactured in Toronto by Trojan Technologies Inc. of Canada,UV oxidation units remove as-yet-unregulated pharmaceuticals and trace elements that are likely to be regulated in the future. Carbon adsorption accomplishes “final polishing” of the water, removing pollutants that affect odor and taste.

The system can be monitored and operated by a single technician from the control center at Binney. Data is transmitted via fiber-optic cable running parallel to the pipeline. “The high-tech control system, including numerous valves and monitoring devices, was a huge component of the project,” Marciniak says.

No Eminent Domain Other than the UV units, the majority of materials came from local manufacturers and suppliers. Pipe was fabricated locally by Northwest Pipe.

Permit applications had to be routed through numerous municipalities: Weld, Adams and Arapahoe Counties, in addition to the cities of Brighton, Denver and Commerce City, each with different review procedures. But an early start and proactive approach helped prevent delays, including acquiring approximately 150 easements and small parcels of land.

Although part of the Prairie Waters campus, treatment buildings were designed to resemble an office park rather than an industrial facility. (Photo courtesy of Aurora Water)

“We are proud that we never had to make demands, use threats or resort to eminent domain to obtain land,” Marciniak says. “Pipe was carefully threaded through the area to avoid major impacts to landowners. No homes were threatened or demolished. Of course, buried pipe is easier, because after installation, the surface remains unobstructed.”

Even though they are part of a “campus,” Prairie Waters’ buildings are intended to resemble an office park rather than an industrial facility, and they blend with the surroundings. At Binney, that would be Aurora Parks and Recreation land.

Linked by paved roads, the buildings at Binney feature handsome standing-seam metal roofs and cultured-stone siding that resembles rock outcroppings. Native landscaping between buildings enhances the office-park ambiance. The pump stations mimic farm buildings to fit their pastoral settings.

Project Team:

Overall Construction Manager: CH2M Hill
Construction Managers: Carollo Engineers: Peter D. Binney Water Purification Facility; HDR Engineering Inc.: North Campus and conveyance system (pipeline); Brown and Caldwell: Robertsdale Tank and Pump Station
Architects/Designers: Brown & Caldwell, CH2M Hill, MWH Americas
Contractors: Garney Construction Inc., Western Summit Constructors Inc., Reynolds-Tierdael, S.J. Louis Construction of Texas Ltd.
Major Subcontractors: Bemas Construction: North Campus and pump stations; BT Construction Inc.: tunneling work on North Campus and pipeline segments 1 and 3; ERS: pump stations; Lillard and Clark: Peter D. Binney Water Purification Facility, Robertsdale Tank and Pump Station
Others: Concrete Express, T-P Enterprises, Northwest Pipe, ERO