Nickels ordered the Seattle Department of Transportation to continue to use liquid de-icer, but use salt under the following conditions:

- if 4 inches or more of snow are predicted - if ice is predicted - if extreme cold is predicted to last longer than 3 days - on hills, arterials, and designated snow bus routes - on routes to hospitals and other emergency facilities indicated by fire and police - on other facilities as dictated by the professional judgment of the Director of the Seattle Department of Transportation.

VIDEO: Nickels' New Strategy For Winter Storms

"This once-in-a-decade storm presented tough challenges for all our city services," said Nickels. "While our crews performed well, we want to make sure we'fre using best practices."

Since 1998, SDOT adopted a practice of avoiding direct use of salt to melt snow and ice.

Salt is well-documented to cause corrosion and adversely impact fresh-water marine ecosystems, the mayor's office said.

SDOT currently uses Geomelt de-icer, which only contains a small element of salt. This has proven effective in normal weather patterns of trace to 4 inches of snow lasting 1-3 days, the mayor's office said.

Regarding the last storm, Nickels said additional private contractors will be hired to speed clean-up of city streets that were sanded.

Nickels also instructed all city departments involved with winter storm operations - transportation, police, fire, human services, City Light, and Seattle Public Utilities - to review their performance and make policy recommendations by Jan. 30.

Nickels said the SDOT needs to improve coordination with King County Metro.

Following the most recent storm, SDOT and Metro agreed that during periods of winter weather, Metro will assign a staff liaison to SDOT's operations office at Charles Street to provide SDOT with timely information.