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Backflow dike set for Tapps
Puget Sound Energy has started construction of a new dike, east of Inlet Island, which is designed to protect residents near the lake from flooding.
The $4 million dike, officially called a “backflow prevention structure,” is designed to prevent water from surging out of the lake during a major earthquake.
The planned concrete structure is 123 feet wide and 28 feet high and will be about 400 feet downstream (east) of the Printz Basin.
The new dike is intended to protect residents and property if a major earthquake caused a breach in dikes 14 and 15, which create the basin.
According to Frank Hella, PSE's project manager, the dikes are “essentially a dam. Dikes 14 and 15 were installed when the reservoir was built (about 1911).”
The protection dike will have two concrete gates, each one 6-by-6 foot with hinged tops. The gates will allow water to flow into the lake from the 10-mile diversion canal that begins at the White River diversion dam near Buckley.
If water were to surge out of the lake upstream, the gates would not flip open, blocking water from flowing out of the lake.
Hella said if one of the Printz Basin dikes failed from surging water, the backflow dike would close the flow in five minutes.
If the dikes failed and water flowed out of the basin and lake, flooding could occur along Sumner-Buckley Highway from 214th Avenue East to the Target store area and under state Route 410.
The construction site for the dike is about 3 miles northeast of the city and east from the 218th Avenue East bridge near Inlet Island.
Hella said PSE expects to have the project completed by June.
In a press release concerning the project, PSE stated the lake would be filled by Memorial Day weekend.
PSE has owned the lake and the surrounding structure for nearly 100 years as part the White River Hydroelectric Project, which was closed down in January 2004.