Wash. Rev. Code § 70.90.160
A permit is required for any modification to or construction of any recreational water contact facility after June 11, 1986, and for any other water recreation facility after July 26, 1987. Water recreation facilities existing on July 26, 1987, which do not comply with the design and construction requirements established by the state board of health under this chapter may continue to operate without modification to or replacement of the existing physical plant, provided the water quality, sanitation, and lifesaving equipment are in compliance with the requirements established under this chapter. However, if any modifications are made to the physical plant of an existing water recreation facility the modifications shall comply with the requirements established under this chapter. The plans and specifications for the modification or construction shall be submitted to the applicable local authority or the department as applicable, but a person shall not be required to submit plans at both the state and local levels or apply for both a state and local permit. The plans shall be reviewed and may be approved or rejected or modifications or conditions imposed consistent with this chapter as the public health or safety may require, and a permit shall be issued or denied within thirty days of submittal.
RCW 70.90.160