Improvements at Howard Hansom Dam have lessened the chances the Green River will flood this winter, according to the Army Corps of Engineers.

The Corps previously said there was a 1-in-4 chance that a flood would inundate the Green River Valley, but now those odds have been lowered to 1-in-25, the Corps estimates.

The Corps of Engineers hired two contractors to work on projects aimed at improving the integrity of the storm-damaged right abutment to the dam.

An $8.9 million contract went to Nicholson Construction for construction of a seepage barrier, a 450-foot-long, 90-to-160 foot-deep “grout curtain” in the right abutment.

Workers have been working nearly around the clock since Aug. 12 to reinforce the dam. They have been drilling holes in the abutment and filling them with a cement mixture called grout. The idea is to create a seepage barrier that will at least slow the water to acceptable levels.

Work also began to protect residents and businesses by raising flood protection levees at vulnerable spots in Auburn, Kent and Tukwila. The levee improvement work was paid for by $8.4 million in funding approved by the King County Flood Control District Board of Supervisors.

About 40 miles of levees have been raised with sandbags, evacuation routes and emergency warning systems have been established.