Washington Stormwater has a section of their webpage designated to Spokane County, with information on properly disposing of waste water. The name of the program is Dump Smart.
To see other resources
Eastern Washington Stormwater Resources
Eastern Washington LID Guidance Manual
City Of Spokane Low Impact Development Ordinance
Eastern Washington Stormwater Organizations: Several groups meet and coordinate in Eastern Washington to share ideas and resources for compliance with the Eastern Washington Phase II Municipal Permit.