Grays Harbor County, WA Accessory Structures: ADU Impact Fees (2026)

Grays Harbor County's utility rate chapter, 13.20/13.22, prices water and sewer capacity in Equivalent Residential Units (ERUs) rather than a flat per-ADU impact fee. Under § 13.22.120, an accessory dwelling unit larger than 600 square feet counts as one full ERU for the general facility charge, the one-time capacity charge new connections pay; the same 600-square-foot threshold applies again for ongoing service billing, where each accessory dwelling unit over that size is also billed as one ERU. A principal residence under 4,000 square feet is one ERU on its own, and a residence of 4,000 square feet or more counts as two ERUs, so a large house with a qualifying ADU can be billed as three ERUs combined.

No property is charged less than one full ERU regardless of use, per § 13.22.120(I). The actual dollar value of an ERU, both the connection charge and the monthly rate, is set by resolution of the board of commissioners under § 13.22.100, and new connections are also billed a separate connection charge covering meters, piping and installation labor at the county's time-and-materials rate plus a 15 percent administrative charge. Delinquent utility charges draw a 10 percent penalty plus 8 percent annual interest under § 13.22.400, and the county may suspend service 45 days after delinquency under § 13.22.500 following written notice and a hearing opportunity.