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Pipe to send waste farther from Redondo shoreline
Lakehaven Utility District has begun replacing an aged and corroding wastewater outfall pipe at its Redondo Wastewater Treatment Plant.
The pipe sends treated wastewater into the Puget Sound near the south end of the boardwalk on Redondo Beach Drive South. When completed, the $4.8 million project will extend the pipe significantly farther and deeper into the Puget Sound than the current pipe.
The current 30-inch diameter corrugated metal pipe was built in 1963. It delivers treated wastewater into the Puget Sound 1,030 feet off the Poverty Bay shoreline. The treated wastewater is dumped 123 feet below sea level. But as the pipe has aged, risk for corrosion has increased.
The pipeline is being lengthened, in part, to better protect marine life, said John Bowman, Lakehaven Utility District engineering and water manager.
The new pipeline will feature 24-inch diameter high-density polyethylene pipe that will place treated wastewater 2,420 feet offshore and 400 feet below sea level. The pipe is less susceptible to saltwater corrosion and is expected to last about 100 years, Bowman said.
“The pipe was becoming corroded and we wanted to replace it before any failure that would have short-circuited the flows (of treated wastewater),” Bowman said.
Lakehaven leases the land where the pipe rests from the state’s Department of Natural Resources.
An inspection of the corroding pipeline revealed a geoduck clam bed near the pipe system, Bowman said. The bed was tested by the Department of Natural Resources and not found to be contaminated by the treated wastewater or the corroding pipeline.
“There are no indications that we are harming the near-shore environment now,” Bowman said.
However, the close proximity of the pipeline to the shellfish’s home will not allow for the geoducks to be harvested and sold, if the department decided to do this, Bowman said. The Department of Natural Resources required Lakehaven to extend the pipeline beyond the animal’s habitat, he said.
“We needed to control the (water) flow so it got farther out and got the proper dilution,” he said. “The near shore is a little more sensitive than farther out in the deeper waters.”
Wastewater and sea lettuce
During the treatment of wastewater at the Lakehaven plant, the fecal matter and other solids are removed from the water, said Chris McCalib, Lakehaven wastewater operations manager.
Micro-organisms are then used to consume nutrients in the wastewater, he said. The third phase of treatment involves using an ultra-violet low intensity, low frequency light bulb to disinfect the remaining substance, McCalib said. Before 2001, chlorine and a compound to deactivate the chemical were used in this phase, he said.
What remains on the wastewater then empties into the Puget Sound.
Wastewater treatment plants add nutrients to any water body they discharge into, said Dave McBride, Washington State Department of Health toxicologist. An abundance of introduced nutrients, as seen in Federal Way’s Dumas Bay with the overgrowth of sea lettuce, can affect marine life.
Discharging the treated water at deeper depths allows it to better dilute and mix with the cooler salt water, said Ron Thom, Marine Sciences Laboratory of Pacific Northwest National Laboratory staff scientist.
“It would be discharging in a bigger volume of water and it would tend to not get as trapped in the eddies and currents,” Thom said.
Lakehaven expects to have the new pipeline completed by September. The project will cost $4.8 million. It will be paid for through the district’s utility rates, Bowman said. The rates will not be raised to pay for the extended pipeline, he said.
“We’ve been planning on doing this outfall for a number of years now,” Bowman said.
A similar project is in the planning for Lakehaven’s Lakota plant, Lakehaven Board President Ron Nowicki said. This wastewater enters Dumas Bay. The district is in the process of securing funding for this location, he said.
Contact Jacinda Howard: firstname.lastname@example.org or (253) 925-5565.
Project intended to better protect marine life in Puget Sound