Watertight

New Dewatering Plant Keeps Vegas Wastewater under the Surface

The Clark County Water Reclamation District awarded its largest project to date last year. The three-year, $119.3 million wastewater solids dewatering project is being completed by contractor MMC Inc.

By Tony Illia

People flush toilets and take showers without a second thought or care in the world, but the Clark County Water Reclamation District has plenty to think about on the other end of the drain.

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The agency collects and treats 100 million gallons of wastewater daily from thousands of homes, schools and businesses throughout the Las Vegas Valley. It’s also responsible for half of Southern Nevada’s return flow credits to the Colorado River.

“We’re an unobtrusive service,” says Richard Mendes, district general manager. “If people know what we are doing then there is usually a problem. They should be able to go about their business, and we’ll take care of the waste.”

The Clark County Water Reclamation District is going through its most ambitious expansion to date with a five-year, $1.34 billion capital improvement program in order to keep up with the rapid pace of residential and resort construction in Las Vegas.

Photo courtesy CCWRD

The district is currently undertaking a five-year, $1.34 billion capital improvement program in order to make sure that its presence remains invisible. It’s the largest, most ambitious construction undertaking in the agency’s 52-year history, and the work is needed to keep pace with the valley’s residential growth and Strip resort construction. The agency has seen its customer base more than double since 1996.

A large hotel-casino development can add up to 5 million gallons of wastewater daily to the district’s system. And $39 billion worth of hotel, resort and high-rise projects are currently planned between 2008 and 2011, adding 41,921 rooms and 2,002 timeshare units, according to the Las Vegas Convention Visitors Authority.

To keep up with the growth, the district will spend $624 million on expansion projects in the Las Vegas area in upcoming years, with over $561 million going toward replacing or rehabilitating existing facilities. It will additionally spend $114 million on upgrading rural-area treatment facilities.

The agency 14 months ago awarded its single largest contract to date - a $119.3 million wastewater solids dewatering facility - to MMC Inc. of North Las Vegas. The multiphase project is located at the district’s 600-acre main treatment plant at 5857 E. Flamingo Rd., Las Vegas.

“The solids dewatering project plays a key role in helping us service the region’s booming growth demands, while still meeting federal and state water-quality standards,” says Brent Moser, the district’s principal civil engineer and construction management supervisor.  

Construction of the new 190 mgd facility consists of a sludge pumping transfer station, underground pipelines and a five-story, cast-in-place building with over $50 million worth of high-tech equipment. Work on the three-year project began in December 2006. 

“The project has eight major milestones that carry up to $11,000-a-day in liquidated damages,” says Jason House, MMC’s project manager, who adds that work is currently on schedule. “We are allowed a limited number of eight-hour shutdowns to tie into the existing facility.”

The undertaking, which will see 110 tradespeople during the peak of activity, entails building a new sludge-transfer pumping station containing six progressive cavity pumps each with a 290-gallon-per-minute capacity. Raw waste is pumped roughly a mile to the solids-dewatering building through six underground pipelines that are up to 48 in diameter.

The piping six-pack crosses underneath the Las Vegas Wash, a feat that entailed extensive microtunneling with six months of dewatering up to 200,000 gallon a day. The contractor additionally experienced some flooding in the process.

“There were some heavy rain days where the wash would run over,” says Blaine Stewart, MMC’s project superintendent. “A 20-ft-wide section of wash would rapidly expand to 200 ft wide.”

The 75-ft tall solids dewatering building will house two, 376,000 gal waste storage tanks. The project was designed by CH2M HILL and is being built by MMC Inc.

Photo by Tony Illia

The pipes feed sludge into the solids dewatering building, which rests atop a 3-ft-thick concrete slab foundation with 92 piers, each 48 in. in diameter and 60 ft deep. The 75-ft-tall structure houses two, 376,000-gallon waste storage tanks, plus four screens, three air blowers and four, 225-cu-yd caked storage bins that weigh 105,000 lbs each.

Sludge goes through a process where waste solids are separated through screening and eight, 50,000-lb centrifuges on the fourth floor. Caked solids then travel via a conveyance system to the ground level where trucks cart them away to a landfill. The building, which has two truck bays, will see up to 18 truck trips daily, each loaded with 30 tons of waste.

Designed by CH2M HILL of Englewood, Colo., the facility is specifically built around the heavy-waste treatment machinery with room for growth. It’s expandable to treat up to 320 mgd in the future.

There is also an elaborate odor-control system. The district’s treatment facility is now surrounded by residential subdivisions. The building, as a result, is under negative air pressure to prevent foul scents from escaping. There are additionally two biotowers that remove hydrogen sulfide and other unpleasant smells via an organic media or biofilter. Cleaned air is then exhausted from the building’s rooftop.

“We must continue growing our capacity, otherwise we’ll top-out in another couple of years,” says Mendes. “We want to remain an unseen service.”

Key Players

Owner: Clark County Water Reclamation District
General Contractor: MMC Inc.
Program Manager: MWH Global
Design/ Engineer: CH2M HILL
Electrical: Acme Electric
Steel: Steel Engineers Inc.
Mechanical: United Team Mechanical
Concrete: Coreslab Structures Inc.
Earthwork: Tab Contractors Inc.

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