...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.
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.”
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.”
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...
