One in three. That's the chance the U.S. Army Corps of Engineers has given King County that heavy rainfall could exceed the damaged Howard Hanson Dam's reduced capacity during the three to five years it will take for repairs.
To increase the protection of people, businessees, and county facilities and services in the event of a flood in the Green River Valley, King County Executive Kurt Triplett yesterday announced that he is sending three pieces of legislation to the King County Council and will request $40 million for 2009 flood preparation costs. He sent a motion to the council seeking affirmation and extension of the Proclamation of Emergency he signed on Sept. 10.
The valley is at increased risk of flooding due to damage to the Howard Hanson Dam, which is located 34 miles upstream of Auburn and operated by the U.S. Army Corps of Engineers. Damages were discovered when water behind the dam rose six feet higher than ever before during record rainfall last January. The Army Corps has advised King County and cities in the Green River Valley to prepare for possible flooding if water into the Howard Hanson Dam exceeds 12,000 cubic feet per second. (Flows in the river reached above that level 15 times between 1932 and 1962 when the dam started operating. Calculations estimate flows would have exceeded that level 17-20 times since 1962 without the dam.)
Triplett will request $8.4 million to temporarily increase the height of Green River levees and more than $32 million to plan and provide for continuity of regional services such as Superior Court, elections, animal control, wastewater treatment and public health. The $32 million will also help protect county facilities such as the Maleng Regional Justice Center, the South Wastewater Treatment Plant in Renton and the Black River Pump Station.
Triplett will transmit legislation requesting the $8.4 million to be paid from the $35 million collected annually from the Flood Control District’s countywide property tax. The $8.4 million Triplett is requesting would augment or replace the federal money Governor Christine Gregoire requested if Triplett's request is denied.
Wastewater flood preparations would be paid for with existing sewer fund balance if the council grants it appropriation authority.
Plans are underway to keep the Wastewater Treatment South Plant in Renton operating if a flood occurs; these include keeping enough staff on site and leasing enough power generators to ensure the plant continues to operate if underground sewage pipelines are inundated with flood waters. The plant treats an average 110 million gallons a day of sewage from south, east, and north King County as well as parts of south Snohomish County.
It is estimated the Green River Valley generates almost $46 million of economic activity per day and a major flood could cause up to $3 billion in damages. Approximately 26,000 residents would have to be evacuated from the lower valley and several hundred more who live in the unincorporated upper Green River Valley if a flood is anticipated.
Triplett was joined by a number of people as he made the announcement, including Governor Gregoire, Army Corps Seattle District Manager Anthony Wright, King County Flood District Chair Julia Patterson and King County Council Chair Dow Constantine.
