WA County Environmental Health Department Links
http://www.doh.wa.gov/LHJMap/LHJMap.htm

WA DOH Rules & Development Committee
www.doh.wa.gov/ehp/ts/WW/RDC.htm

WA Dept of Environmental Health (DOH)
http://www.doh.wa.gov/ehp/ts/WW/default.htm

Washington Department of Licensing : Onsite Waste Water Designers
Information
http://www.dol.wa.gov/business/onsitewastewater/

Find a licensed designer:
https://fortress.wa.gov/dol/dolprod/bpdLicenseQuery

Onsite Regulations in other States :
http://www.modelcode.org/rules.html