Your King County Well Drilling Contractor
King & Snohomish County work essentially the same way First & foremost, jump through all the hurdles - it's not fun, it's not easy, but you'll be wishing you had if you don't.
Get a septic designer on site to determine the possible locations for a septic system & well - they will probably end up having to contact the County so that a biologist can confirm that there are no Critical Areas in the vicinity of either system. Check with King County Deparment of Development & Environmental Services (DDES) for other questions, regarding grading, filling, driveways, critical areas, etc. They will also handle your building permit application.
Water Well Covenant - For Residential Water Supply Wells
King County Health requires that King County water wells be placed & protected by a 100-foot radius where no possible sources of pollution are & a covenant attached to the property showing this radius, in order to protect the well from potential sources of pollution. In plain English - they ask that you show on a map where the well is, and that you not build any buildings, install any drainage or sewer systems, nor install any roads within this radius. In fact, they require that NO 'potential' sources of contamination be installed within this 100 foot radius. King County also requires you to record a document in the permanent record for your property, mapping the location of the well & the radius around it.
King County has no special rules for the construction of irrigation wells, and in fact, these types of wells are often easier to site in King County than a domestic water supply well.