Statutes Authorizing the Agency to Adopt Rules on this Subject: The forest practices board's (FPB) authority to adopt forest practices rules is granted under RCW 76.09.040, [76.09].050, and [76.09].370. The pilot project process is authorized by RCW 34.05.313.

Reasons Why Rules on this Subject may be Needed and What They Might Accomplish: This rule is required to authorize the implementation of experimental harvest treatments that exceed the limits currently allowed under FPB rules (WAC 222-30-021) as part of the riparian characteristics and shade response (RCS) experimental research study. The study evaluates how stream shade responds to a range of riparian harvest treatments of varying intensity on commercial forestlands covered under the forest practices habitat conservation plan (FPHCP 2005). This [pre]proposal statement of inquiry pertains to four harvest units in western Washington that are scheduled to be harvested between June and August 2026 (Figure 1).

Washington's forest practices regulations include riparian prescriptions that establish no-harvest buffers of varying widths along streams. These rules allow for no-harvest riparian buffers to be applied independently or in combination with selective harvest (thinning) within the adjacent riparian management zone (RMZ). However, field research is limited regarding the combined effects of no-harvest zones and varying thinning intensities on stream shade within RMZs. This study will address a key question about how shade could be affected by using forest thinning as a riparian management tool (e.g., to promote old growth forest characteristics).

The four Type F (fish-bearing) streams under consideration for the RCS study are in western Washington. Sites are numbered in order of expected suitability, with the intent of implementing the study at two of the four sites. Site 1, Jim Creek, is a tributary to Jim Creek within the Pysht River Watershed Administrative Unit (WAU) and is under Merrill and Ring ownership. Site 2, West Fork Stevens Creek, is in the headwaters of Stevens Creek within the Stevens Creek WAU and is under Rayonier ownership. Site 3, Stevens Creek, is a tributary to Stevens Creek within the same WAU and is also under Rayonier ownership. Site 4, Little Deschutes, is a tributary to the Little Deschutes River and is under Weyerhaeuser ownership within the Upper Deschutes WAU. Reconnaissance surveys were conducted in January 2025 at Sites 1 and 2 to verify that basal area requirements are met and that three 325-foot research plots could be established along each stream segment.

Within each site, the three treatments will be randomly assigned to three research plots. Outside these plot locations, existing rules in WAC 222-30-021, including default RMZ widths specified by the discounted cash flow model, will still apply. The 30-foot equipment limitation zone will be maintained both inside and outside the plots, and outer zone leave tree requirements will remain unchanged.

Thinning will follow a "from below" approach, where the largest trees in the plot are designated as leave trees first, followed sequentially by the next largest, until the target curtis RD is achieved. Curtis RD is a comprehensive measure that integrates stand basal area and average tree size (quadratic mean diameter). Using curtis RD rather than trees per acre or total basal area offers a more nuanced understanding of tree competition across various forest types in Washington, accommodating the diverse range of tree species encountered in the region.

Other Federal and State Agencies that Regulate this Subject and the Process Coordinating the Rule with These Agencies: FPB is the oversight agency with the authority to approve this pilot activity. The pilot rule is being requested as part of the formal FPB adaptive management program, which includes representatives from state agencies, including the departments of fish and wildlife, ecology, and natural resources; federal agencies, including National Marine Fisheries Service, United States Fish and Wildlife Service, and the Environmental Protection Agency; forest landowners; the environmental community; county governments; and tribal governments.


•	Clearcut within the RMZ to a riparian buffer width of 25 feet from the stream's edge.
•	Heavy thinning to a curtis relative density (RD) of 20, to a riparian buffer width of 25 feet.
•	Moderate thinning to a curtis RD of 40, to a riparian buffer width of 25 feet.

Interested parties can participate in the decision to adopt the new rule and formulation of the proposed rule before publication by contacting Maggie Franquemont, Forest Practices Policy Program Manager, Department of Natural Resources, Forest Practices Division, 1111 Washington Street [S.]E., 4th Floor, P.O. Box 47012, Olympia, WA 98504-7012, phone 360-902-1413, fax 360-902-1428, email forest.practicesboard@dnr.wa.gov.

Additional comments: FPB has approved inclusion of the RCS study in the master project schedule. The RCS study has a peer-reviewed study design and is supported by the forest practices adaptive management program. The timber fish and wildlife policy committee and the cooperative monitoring, evaluation, and research committee are supportive of this study. Previously, FPB approved pilot rule making for the RCS study (February 2023, 2024, and 2025).

Figure 1. Maps of the four sites currently under consideration. Permission is being sought to implement the RCS study at all four potential sites, with the understanding that two sites will be selected for project implementation in 2026. Forest practices applications (FPA) were screened using the site selection criteria outlined in the approved study design. The preferred stream at Site 1 is designated as a fish-bearing stream in the FPA based on default physical criteria, despite being initially mapped as a nonfish stream (green) in the forest practices hydro layer.

Figure 2. Experimental design for the RCS study. A study site consists of three plots with a revised 25 foot no harvest core zone, measured from the stream edge (outer edge of bankfull width), which deviates from WAC 222-30-021 (western Washington; 50 foot core zone). Riparian forest thinning from 100 to 25 feet from the stream edge will be performed to a relative density of 0, 20, and 40 for each of the plots.