Everett , WA — The key to pollution is dilution and environmentalists are applauding Everett Washington ‘s deep-water outfall project for accomplishing just that. The state-of-the-art pipeline is a joint effort by the cities of Everett and Marysville along with Kimberly-Clark Paper Mill to dispose of their wastewater. The pipeline will carry the waste deep into Port Gardner Bay and replace the old discharge locations along the Snohomish River . City ratepayers and the paper mill will save more than $10 million on the project by sharing the construction costs but the big winner is the habitat of the bay and the salmon fishery of the river.
Treated wastewater from Everett and Marysville will be pumped to Kimberly-Clark and mixed with the company’s wastewater before it is sent into the bay. As a further benefit, the municipal sewage will cool waste created in the pulp-bleaching process. That will allow Kimberly-Clark to stop using millions of gallons of fresh water as a coolant.
The pipeline will be able to carry about 105 million gallons a day, although less than half that volume is needed initially. By February, more than 45 million gallons of treated wastewater will rush through the pipe on its way to depths of 350-feet in the bay. There it will be diluted with seawater to prevent harm to marine life.
There is no other piping material in the world that could have handled a maneuver like that
Kimberly-Clark has long sent its wastewater into Port Gardner Bay , but two of the three pipes it uses are more than fifty years old. One is rotting and leaks, and the other sends waste only 50-feet from shore into water that is less than 30-feet deep.
Of the $60 million price tag, Everett, Kimberly-Clark and Marysville are all contributing. Marysville will lay new pipe to transfer its waste to the Everett facility and help with costs for the treatment plant’s pumping station. Marysville will also lease some of the pipeline’s capacity.
The partnership is not the only unique aspect of the project. The actual construction procedure of the pipeline is an engineering feat in itself and only possible with the help of high-density polyethylene (HDPE) pipe.
Advanced American Diving Service (AADS) is performing the work on the project. Based in Portland OR , AADS is recognized as an expert in marine construction and consulting. They specialize in projects that are in, on or around water.
“Polyethylene is playing a prominent role in this project”,” said Mike Johns, Vice President of AADS. Johns started with AADS as a diver and worked his way up to becoming a full partner in the company. He is still an on-site General Superintendent on larger developments and was involved with every aspect of this project. “I am amused when people question the physical toughness of polyethylene. We pursue projects like this that demonstrate innovation, community contribution and environmental sensitivity and this job was perfect for polyethylene. Its toughness is the key to this project that is improving the local environment in so many ways.”
4,400-feet of 63-inch-diameter HDPE was fused together on the banks of the Snohomish River about three miles from the discharge location in the bay. A McElroy 2065 MegaMc fusion machine was used to perform the task. The MegaMc can fuse pipe up to 65-inches in diameter. The key to the pipe’s strength is that once it is fused together, the joints are as strong as the pipe itself. This was particularly important for this project because the pipe would undergo tremendous stress during its deployment.
The ends of the pipe were capped and as the pipe was being pulled into the river, concrete weights were added to aid in the sinking of the pipe once it is positioned in the bay.
The pipe had to be towed down the river and the flexibility of HDPE to snake its way around the curves of the river is one of the reasons it was chosen for the project. HDPE is also impervious to buildup on its interior walls, which can restrict flow. It also will not corrode in the saltwater of the bay.
The deep-water section of the pipe is 2,800-feet long and will slope from 50-feet to a depth of 350-feet. The final 1,500-feet of it will be at a constant depth of 350-feet. This portion of the line will have 80, five-inch diffusers mounted to the top of the pipe to disperse the affluent. The deep-water section will simply lie on the floor of the bay. The intertidal section, which is 1,600-feet long will be in waters less than 50-feet deep and will be buried in a trench so that it is not an obstruction for marine life. The two sections will be joined together by divers under water.
The excavation of the trench presented a challenge for AADS. To deal with the unstable sediment in the bay and the tidal surges, they erected a trestle across the tidal flats from which to perform the excavation.
The deployment of the pipe was perhaps the most crucial procedure of the entire project. Once in position and floating in the bay, a precise amount of air had to be released from the pipe, as water was allowed in, to cause it to descend in a controlled manner. Divers were on hand to make sure the intertidal section settled exactly into the trench that was excavated.
From there, the deep-water section was deployed. As it settled to the bottom of the bay, it actually performed a slow-motion ‘S’ curve under water due to the slope of the bay floor. The movement was much like a garden hose when given a sharp downward tug.
“There is no other piping material in the world that could have handled a maneuver like that,” said Mark Theetge of ISCO industries. ISCO was the pipe and fusion machine supplier for the project. “Polyethylene always gets the tough jobs because it has unbelievable strength and durability. It’s a dream material to work with and people are starting to realize that if it is the material to be trusted for the most difficult of projects, then it could be used for other portions of the pipeline as well.”
After the pipeline is complete, workers will create a public beach from the nearby shoreline where the pipe enters the marine tidal flat. The excavated area will be restored to the contours of a sloped beach for habitat and public access.