Building Prairie Waters

Story by Carol Carder | September 28, 2010

The Prairie Waters Project is a huge undertaking that will boost the water supply of Aurora, CO, by 20 percent when it's completed in late 2010, but safety doesn't take a back seat to anything — not the aggressive schedule, not the complicated logistics — as the project team builds the $754-million system.

"Safety has been our top priority since the beginning of construction in May of 2007," said Aurora Water Program Director Darrell Hogan, P.E. "As of the end of October, we have logged 717,189 man-hours with only five recordable incidents, one lost-time incident and 14 utility strikes."

The total work hours are equivalent to 300 people working a full year on the construction. That enviable performance may result in a 0.25 experience modification rate for the project, while the national average is 1.0. EMR is the statistic used by the insurance industry to measure safety performance.

According to Hogan, the low EMR is an important money saver, since the project is operating with an owner-controlled insurance program. The lack of lost-time incidents also is keeping the project on schedule to finish by the end of 2010. By that time the project will have logged an estimated 2 million work hours.

Most of the 14 strikes were the result of unmarked or mis-marked utilities, Hogan added. That's not a bad record when one considers three pipeline contractors are installing 34 miles of 60-inch-diameter pipeline to transport water from the North Campus near Brighton to the Aurora Reservoir Water Purification Facility.

The project utilizes two natural purification processes — river bank filtration (RBF) and aquifer recharge and recovery (ARR) — as the first steps of a six-step purification strategy. CH2M Hill developed and conducted a pilot-testing program in coordination with several leading Colorado-based water quality researchers: Dr. Jörg Drewes of Colorado School of Mines; Dr. Gary Amy of the University of Colorado and the United Nations Educational, Scientific and Cultural Organization; and Dr. Ken Carlson of Colorado State University.

Although water providers have used natural water purification systems for decades, this project is a unique application of the science on a large scale up to 50 million gallons per day and is also unique in the combination of the two processes.

"In a year of testing starting in 2005, we confirmed that these natural filtration and purification processes would remove from 75 to 80 percent of the organic carbons without adversely affecting the environment," stated Rod Brauer, CH2M Hill program manager for the Prairie Waters Project.

The purification starts with 17 wells drilled into the South Platte River bank about 300 feet from the river. The water will take five to 10 days to travel through this collection and natural filtration process. Then from the riverbank filtration, the water will transfer into a 200-acre site where it will seep down through alluvial sands for 20 to 30 days, filtering out trace chemicals, pharmaceuticals and organic carbon compounds. From the natural purification system, the water will travel with the aid of three pumping stations in a 34-mile-long, 60-inch-diameter pipeline to the new water treatment plant at Aurora Reservoir.

The American Council of Engineering Companies of Colorado has awarded CH2M Hill, the designer of the filtration processes for this innovative project, an Engineering Excellence Award for design in its 2009 competition.

Safety Culture

The safety culture on the Prairie Waters Project starts with complete safety oversight from the top down through the holders of the seven major contracts and their subcontractors. In pre-qualifying the bidders, Aurora Water considered the EMR of each potential contractor. EMRs of the winning contractors averaged about 0.75, according to Hogan. Each contractor submitted its safety plan for review by Aurora Water.

An unusual aspect of every contract is requiring the contractor to have a safety officer.

"That duty is often tagged to a superintendent on a smaller contract as one of the regular duties, while on the seven prime contracts the contractor is required to employ a separate individual whose task is to make sure activities on each project are accomplished safely," Hogan explained.

The project's safety records show that more than 1,523 safety orientations have been held since the beginning of the project. Safety meetings form part of the orientation before the project and also take place at the beginning of each new activity. Each contractor conducts a weekly safety meeting with his crew. Also, the prime contractors conduct safety orientations with any consultants or other individuals such as public information officers who step foot on the job site, even occasionally.

Aurora Water has its own safety officer who roams all the projects on a daily basis, and Aurora Water's OCIP manager Lockton Companies LLC provides a safety person who visits once a week.

"With these different individuals looking at safety from different viewpoints, we have excellent oversight and a good safety culture," Hoganemphasized.

Western Summit Constructors Inc. used a vivid demonstration to emphsize the importance of safety at one of its weekly meetings. Unbeknownst to the employees, the company had bought a salvaged car and parked it close to the work site. During the meeting, a large earthmover pulled up and ran over the car, squashing it flat. The lesson: Yield the right of way to heavy equipment; the machines need a longer distance to stop. And yes, the consequences of ignoring that can be drastic.

Environment and Sustainability

"An important challenge we met was satisfying Aurora Water's goals to design a sustainable utility and to protect the environment during construction," CH2M Hill's Brauer stressed.

The riverbank filtration and aquifer recharge and recovery will effectively remove up to 80 percent of organic carbons, greatly reducing the chemicals used at the Aurora Reservoir Purification Facility. Creative scheduling sequenced construction to avoid wetlands and critical wildlife habitats such as bald eagle nesting areas and prairie dog colonies.

"We had to stay 150 feet from burrowing owl areas between March and October," added Tom Roode, P.E.,Aurora Water pipeline and pumpstation project manager.

According to Roode, the pipeline makes 14 crossings in its 34-mile-long journey. To protect waterways and transportation corridors, the contractors used tunnel boring machines, hand-mining of tunnels, and jack-and-bore methods. Each tunnel also posed safety and scheduling challenges to the project. Tunnels range from a couple of hundred feet to the 760-foot-long tunnel under Pena Boulevard.

When the Prairie Waters Project begins operations in 2010, the North Campus natural purification facility and the Aurora Reservoir purification facility will process 12 million gallons per day. As water demands grow, Aurora will increase capacity to 50 million gallons per day.

"From conception to completion in just five and a half years using the conventional design, bid, build method is an extraordinary accomplishment," Brauer concluded.

Author Information
Carol Carder is a Denver writer who covers Colorado construction for RMC.


Prairie Waters Project Components

Project cost estimate, including land acquisition, engineering, and construction: $754 million

Project management/engineering: CH2M Hill

Construction management: HDR Engineering, Carollo Engineers, Brown and Caldwell

System completion: late 2010

Will ultimately deliver 3.3 billion gallons of water annually

Three pumping stations

Construction began summer 2008

Designer: MWH (Montgomery Watson Harza) Americas Inc., Denver

Contractor: Western Summit Constructors Inc., Denver

Conveyance pipeline of 34 miles

Mostly 60-inch-diameter, mortar-lined, urethane-coated steel pipe

Designer: MWH Americas Inc.

Segment 1: 13 miles, began summer 2008, contractor: Reynolds Tierdael, Denver

Segment 2: 9 miles, began winter 2008, contractor: S.J. Louis Construction of Texas Ltd.

Segment 3: 10 miles, begins winter 2009, contractor: Garney Construction, Denver

North Campus Natural Purification

Construction began spring 2008

Designer: CH2M Hill

Contractor: Garney Construction, Denver

Aurora Reservoir Water Purification Facility

Construction began July 2007

Designer: CH2M Hill

Contractor: Western Summit Constructors Inc., Denver

Construction Progress

Pumping Stations 1, 2, 3

Construction started July 2008 with removal of more than 92,150 cubic yards of dirt Through October — 11 percent complete

Aurora Reservoir Water Purification Facility

About 1.7 million cubic yards of dirt excavated (equivalent to 18 cups of dirt for every person in U.S.) Through October — 59 percent complete

Conveyance Pipeline Segment 1

Pipe placed along 120th Avenue in Commerce City and working north Tunneling under US 85 has commenced Through October — 11 percent complete

Conveyance Pipeline, segment 2

More than 45,066 linear feet of 60-inch-diameter pipe installed Tunnel crossing at Pena Boulevard complete Through October — 96 percent complete

Conveyance Pipeline, Segment 3

Work commences in winter 2009 North Campus Facilities Construction 17 wells installed

Activities for interconnecting pipeline continue Through October — 25 percent complete