LYNNWOOD — Heavy rains this week pushed Lake Serene to its highest level recorded, as Snohomish County prepares to start emergency work to bypass a blocked drainage pipe.

Homeowners ringing the lake west of Highway 99 have watched since January as water levels rose.

A measurement Thursday morning showed it had gone up by 3.5 inches in just one day. That put the lake about an inch above the previous high from March 2014.

“Snohomish County continues to do all it can to ensure there is no damage to public infrastructure around Lake Serene and to ease the impacts of flooding on lakefront property,” public works officials said in a statement.

The county is measuring lake levels daily.

A nearby rain gauge showed that more than 2 inches of precipitation fell during 48 hours between Tuesday and Thursday. The National Weather Service predicted a 30 percent chance of rain Saturday, a 50 percent chance Sunday and likely rain Monday.

A blocked outflow pipe on private property on the west side of the lake appears to be to blame. Construction on a temporary bypass is scheduled to begin Tuesday. That work is expected to lower the current lake levels by more than a foot.

In performing that work, the county is trying to make sure it doesn’t send water to erode or flood downstream properties.

While some of the drainage problems involve private property, county officials want to protect Serene Way and a fire station from potential damage.

The failing outflow pipe was built some 50 years ago. It’s about 300 feet long.

The emergency fix would be built on public property next to the boat launch on the west end of the lake. It’s expected to take about two weeks to complete, depending on conditions.

A longer-term solution would require 95 property owners around the lake to chip in for the cost of repairs. That would require a new yearly payment of $197 per tax parcel over the course of 10 years.

County engineers estimate the long-term fix for the drainage system would cost about $850,000. If it moves ahead, work could stretch into next year.

Some homeowners around the lake wonder why it’s only owners of parcels next to the shore who are being asked to pay the extra fee, and not homeowners in the entire watershed that drains into the lake.

A hearing on establishing the special fee to pay for the permanent fix is scheduled at the County Council at 10:30 a.m. March 22.

Noah Haglund: 425-339-3465; nhaglund@heraldnet.com. Twitter: @NWhaglund.