Rental rates of equipment shall be reviewed annually, or every two years for counties that budget on a biennial basis, by the county's legislative authority. Rental rates must include, but are not limited to, the following:

(1) Estimated service life in years and service life remaining;

(2) Replacement cost;

(3) Salvage value;

(4) Estimated operating and maintenance cost;

(5) Direct and indirect cost of maintaining and operating facilities specific for ER&R equipment;

(6) ER&R program administration.

ER&R rates for equipment shall be determined by the county engineer or other appointee of the county legislative body. However, if the rates are set by an appointee other than the county engineer, the county engineer shall review the proposed rates and certify to the legislative body that the proposed rates are an appropriate use of county road funds as required by RCW 36.80.030 prior to adoption of the proposed rates by the legislative authority.

The resolution by the legislative authority adopting the rental rates must include reference to the fact that the rental rates for county road equipment have been reviewed by the county engineer and certified as an appropriate use of county road funds as required by RCW 36.80.030.