A rapid response was promised Wednesday by representatives of the state and federal governments, as they briefed members of a King County Council committee on preparations already under way in case water from the strom-damaged Howard Hanson Dam inundates the Green River Valley.

The dam is owned by the federal government.

Jim Mullen, Director of the state Emergency Management Division, told members of the council’s Committee of the Whole that his agency and the state’s Military Department are already offering training and preparedness workshops to threatened communities, as well as preparing shelter and mitigation plans.

Mullen said the state’s assistance involves several state agencies, from the Department of Transportation’s preparation of evacuation routes and search and rescue plans to the Department of Social and Health Services arrangement of assistance for those with special needs who are displaced by flooding.

Other state agencies involved range from the Department of Commerce and the Department of Health to the Department of Fish and Wildlife, which would assist in identifying personnel and equipment for swift water rescue.

According to Mark Carey, Federal Emergency Management Agency (FEMA) Mitigation Division Director for this area, the potential property and economic loss from major flooding in the Green River Valley could go as high as $4 billion.

County agencies affected range from the regional justice center in Kent to the county’s election headquarters in Renton. Also affected would be the county jail attached to the justice center and the county’s main animal shelter, also in Kent.

King County council member Julia Patterson, whose district includes the valley, said flooding could impact transportation corridors throughout the Puget Sound region.

“Evacuating thousands of people from the Green River Valley, along with shifting transportations routes for those who depend on State Route 167 everyday, will push I-5 to the limit. We must take every step necessary to ensure people can safely evacuate the Valley.”

Emergency officials acknowledged that while they will assist the county in several aspects of flood preparation, King County will have the primary responsibility for setting up shelters for displaced residents.

Lon Biasco, Division X Director of Disaster Operations for FEMA, told the committee that FEMA is not a first responder, but rather an agency that supports and coordinates federal response through state officials who come to FEMA with specific needs. For example, he said FEMA is now assisting with locating generators to keep the county’s South Treatment Plant operating to process wastewater in the event of a flood-related power failure.

FEMA’s Carey noted that his agency rates King County as the second most-prepared community in the nation in the ability to manage flood risk — from early warning to flood fighting to levee maintenance.

FEMA already has been providing technical assistance and is prepared to provide financial assistance where needed. Carey said up to $14 million would be available to assist with mitigation.

Both the state and federal officials stressed that preparation is the best weapon in advance of floods, and encouraged community outreach efforts on the preparation of evacuation kits, discussion of where to go in case of flooding, and the purchase of flood insurance.

The Army Corps of Engineers discovered the problem with the earthen abutment next to the dam after January’s record rain. According to the Army Corps a temporary fix to inject grout into the earthen material to control seepage is under way but dam storage capacity will be limited until the repair can be tested next spring. A long-term fix could take the federal government three to five years and hundreds of millions of dollars.