LYNNWOOD — Snohomish County expects to finish a key drainage repair at Lake Serene almost a year ahead of schedule, with work starting Tuesday.
Construction is expected to take about a week. The new outlet should bring down the lake about 2 feet from its current level by replacing the existing drain with a new one that sits lower in the water, county public works officials said. The new outlet will connect to the emergency bypass pipe the county built in March to replace a blocked outlet.
“We sped up the process so we could build this key piece before the next rainy season,” county surface water management director Will Hall said. “This will significantly reduce the risk of future flooding.”
When approved this spring, the fix wasn’t expected until 2018. To prepare for construction this year, the county obtained five permits from federal, state and local agencies.
County officials are inviting the Lake Serene neighborhood to the public boat launch from 4 to 6 p.m. Sept. 14 to celebrate the milestone. County staff also expect to discuss further drainage improvements planned over the next couple of years.
Lake Serene lies north of Lynnwood just west of Highway 99. Surface levels vary seasonally. Development during the 20th century significantly altered the west end of the lake, which used to flow naturally into Norma Creek.
A historically wet winter and a plugged pipe pushed the lake to an all-time high on Feb. 17. Flood waters ruined yards, seeped into crawl spaces and threatened foundations.
County leaders built an emergency bypass pipe in March along the road to the boat launch. Over the next couple of weeks, the lake level dropped by 9 inches, county officials reported.
In late March, the County Council approved a plan to pay for long-term drainage fixes at the lake. The cost-sharing arrangement imposed a $197 yearly fee over the next decade on affected properties. Some neighbors are upset that the fee applies only to 95 lakefront properties, instead of more broadly to the hundreds of nearby parcels that drain into the lake.
The fees the homeowners are paying should cover about one-fifth of an estimated $800,000 in repair costs.
With the new drain, lake levels should return to the range people were accustomed to since 1981, when the old 18-inch outlet pipe that had problems last winter was installed. The new pipe is the same size.
“We will maintain this in the future,” Hall said. “This is not just a one-time fix.”
In 2018 and 2019, the county hopes to repair about 600 feet of pipes and ditches between Serene Way and Beverly Park Road. That will require negotiating with property owners for access and some land.
Neighbors from the Lake Serene area of unincorporated Lynnwood are invited to visit the public boat launch from 4 to 6 p.m. Sept. 14 to learn about the installation of a new and improved outlet pipe. Snohomish County public works staff also plan to discuss future downstream drainage work planned in 2018 and 2019.