Neighbors ask Thurston County to reverse preliminary plat approval over groundwater mounding concerns

Thurston County commissioners on Wednesday heard oral arguments in an appeal of a hearing examiner's April 30, 2026 approval of a preliminary plat and forest land conversion that would allow roughly 105 single-family lots on about 22 acres within the Salmon Creek Drainage Basin.

Jim Weston, one of the appellants who lives across the street from the project, told the board he and neighbors have experienced repeated groundwater flooding in the area and that the preliminary drainage report before the examiner did not include a groundwater mounding analysis the drainage manual requires for sites in the Salmon Creek basin. "Without the mounding analysis, the record before the hearing examiner had no evidence of whether this project will cause groundwater flooding to surrounding properties," Weston said, urging the board to reverse the examiner, remand for a new hearing after a compliant mounding analysis is submitted, and ask county planning staff to clarify whether tree clearing will be prohibited until final drainage approval.

Counsel for the applicant, Heather Burgess, urged the board to deny the appeal and said the hearing examiner properly applied county code and the county's Drainage Design and Erosion Control Manual (DDECM). Burgess said public works staff reviewed the preliminary drainage design and that the record included staff recommendations and expert testimony confirming the design met applicable DDECM standards subject to a mounding analysis during final engineering. "The applicant is going to do a mounding analysis. It will be submitted, it will get through a thorough review," Burgess said, adding that no clearing or grading will occur before that engineering review and required permits are in place.

Both sides pointed to the Salmon Creek interim standards adopted after high groundwater flooding in the late 1990s. Appellants said those basin-specific rules require early submission of a groundwater mounding analysis so the public and outside experts can review potential impacts before preliminary approval; the applicant said the county's consistent practice has been to complete the mounding analysis during final engineering review and to enforce compliance through conditions attached to preliminary-plat approvals.

Commissioners asked clarifying questions of counsel about how basin standards are applied and whether county planning and public works procedures prevent premature clearing. Appellants repeated concerns that lack of a public mounding analysis at the preliminary stage limited meaningful public comment and could allow irreversible tree removal before groundwater impacts are fully assessed.

The board did not vote at the hearing. The chair said the board will issue a written decision on or before July 13, 2026. The hearing record includes references to the county's drainage manual and Salmon Creek interim standards, and appellants cited state subdivision criteria and RCW provisions in their materials.

The board's written decision will determine whether the hearing examiner's preliminary-plat approval stands, is reversed, or is remanded for further proceedings. If the board affirms the approval, the record indicates the applicant must complete the required mounding analysis and obtain final engineering approval before any clearing or construction permits issue.