Wash. Rev. Code § 17.10.154
It is recognized that the prevention, control, and eradication of noxious weeds presents a problem for immediate as well as for future action. It is further recognized that immediate prevention, control, and eradication is practicable on some lands and that prevention, control, and eradication on other lands should be extended over a period of time. Therefore, it is the intent of this chapter that county noxious weed control boards may use their discretion and, by agreement with the owners of land, may propose and accept plans for prevention, control, and eradication that may be extended over a period of years. The county noxious weed control board may make an agreement with the owner of any parcel of land by contract between the landowner and the respective county noxious weed control board, and the board shall enforce the terms of any agreement. The county noxious weed control board may make any terms that will best serve the interests of the owners of the parcel of land and the common welfare that comply with this chapter. Agreements made under this section must include at least a one thousand foot buffer for all adjacent agricultural land uses. Noxious weed control in this buffer must comply with RCW 17.10.140(1).
RCW 17.10.154