January 12, 2012

Anacortes building a $56M water plant

Photo courtesy Sky-Pix Aerial Photography [enlarge]

The project is challenging, particularly because the new plant must be built between an existing water treatment plant and the Skagit River while the existing plant operates.

The largest water treatment project in Washington is under way in Mount Vernon.

The new $56 million plant will serve Anacortes and is being built on a site at 14489 Riverbend Road between the existing plant and the Skagit River.

Imco General Construction of Ferndale is the general contractor. HDR is the design engineer. MWH is the owner's representative and construction manager.

Construction started a year ago and is expected to be done by spring of 2013.

The contractor is on time and will come in under budget: the engineer's estimate was $67 million.

Imco shaved six months off the planned timeline, and so far change orders have been less than one half of one percent.

Members of the team credit their success to good communication. Todd Pike, project manager at Imco, said everyone is willing to work together to solve problems, and Fred Buckenmeyer, Anacortes public works director, said the camaraderie at project meetings is real. Matt Reynolds, assistant city engineer, said projects don't always work like this. “When you start out on a project, you try to build trust. That's happened.”

Buckenmeyer said the plant is the largest publicly funded project ever built in Skagit County, except for work on Interstate 5, and is its largest economic engine. Water from the plant goes to 56,000 people. The places it serves include Anacortes, Oak Harbor and Whidbey Island, as well as the Shell and Tesoro refineries.

Photo by Katie Zemtseff [enlarge]

The team said it has shaved six months off the planned timeline, and so far change orders have been less than one half of one percent.

Other than a small loan, the cost is being funded entirely by the utility. “This is born and bred and provided for locally,” Pike said.

The city had outgrown its old plant, which was built in 1970 to treat 20 million gallons a day and was upgraded to handle 30 million gallons a day. The new plant is designed to treat up to 42 million gallons, and can be expanded to treat 55 million.

Buckenmeyer said the existing plant reached capacity twice in the last six years. Despite difficult economic times, the city council decided to replace it.

The plant draws water from the Skagit River. It is processed and screened at an intake station before it flows into sedimentation basins that resemble ice cube trays. After the dirt settles, the water moves into a filtration system where layers of anthracite, sand, garnet and gravel filter more material. Water goes to a well and a high service pump station sends it to Anacortes and other customers.

The new system is quicker and more effective, Reynolds said. It uses Actiflo, a ballasted sedimentation process, to accelerate settling.

The Anacortes plant was traditionally bid. Pike said the construction process is becoming more open in part because of the influence of new contracting methods like GC/CM and design-build. Imco would like to work on more of those types of contracts, but Pike said the key is having everyone on board.

“You (can't) miss one person... It's a purposeful, intentional effort on all sides of the contract,” he said. “We don't have to have a design-build contract or GC/CM contract to reach out and have this positive, open communication with the owners and the design team.”

Brandt Barnes, construction manager with MWH, said the project is challenging, particularly because the new plant must be built while the existing plant operates. “That's the biggest one-ticket item. We can't mess with their ability to deliver water to their customers.”

Another challenge is the tight site. The existing treatment plant building is on piles but the large sediment basin next to it is on earthen fill. The team had to drive 350 piles next to the existing basin. They installed monitoring equipment, and part of the basin was drained at one point because there was some movement.

Imco and MWH created a pile-driving sequence to protect the existing plant. Instead of driving piles from north to south along the length of the plant, they moved in horizontal lines away from the plant from east to west. This gave ground near the plant more time to heal.

Water from the nearby river was another concern. The Skagit River is the third largest on the West Coast. It has flooded in the past and plant operators have an emergency standby system. To further protect the new plant, an interior ring dike has been built around it and all electrical components are located above flood stage elevation.

“Even if the river did food and inundated the plant, no electrical components would get hurt or interrupted,” Barnes said.

The new plant also has an emergency backup system and could run at 50 percent capacity for seven days without interruption.

The project also required a complex dewatering system.

Pike said Imco has experience with wastewater plants and does a lot of work in-house — like pile driving and dewatering — that other contractors generally subcontract. Pike said Imco's experience helps it anticipate problems earlier.

Another unique element is the plant pumps. The city required a hydraulic model study of the big pumps, which Clemson University in South Carolina did. Barnes said the university's work helped make the pump can design more efficient, which minimizes wear, reduces maintenance and makes them more cost effective.

Running the pumps costs about $80,000 a month, Barnes said, so efficiency makes a big difference.

Barnes said the plant is also unique because the water comes from the river. The turbidity of the water changes dramatically and dealing with changing levels was another challenge for the team.

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