Wash. Rev. Code § 90.46.150
The permit to apply agricultural industrial process water to agricultural water use shall be the permit issued under chapter 90.48 RCW to the owner of the agricultural processing plant who may then distribute the water through methods including, but not limited to, irrigation systems, subject to provisions in the permit governing the location, rate, water quality, and purpose. In cases where the department of ecology determines that a significant risk to public health exists, in land application of the water, the department must refer the application to the department of health for review and consultation.
The owner of the agricultural processing plant who obtains a permit under this section has the exclusive right to the use of any agricultural industrial process water generated from the plant and to the distribution of such water through facilities including irrigation systems. Use and distribution of the water by the owner is exempt from the permit requirements of RCW 90.03.250, 90.03.380, 90.44.060, and 90.44.100.
Nothing in chapter 69, Laws of 2001 shall be construed to affect any right to reuse agricultural industrial discharge water in existence on or before July 22, 2001.
RCW 90.46.150