(1) In collecting and analyzing water quality data for any purpose identified in RCW 90.48.580(2), data is considered credible data if:

(a) Appropriate quality assurance and quality control procedures were followed and documented in collecting and analyzing water quality samples;

(b) The samples or measurements are representative of water quality conditions at the time the data was collected;

(c) The data consists of an adequate number of samples based on the objectives of the sampling, the nature of the water in question, and the parameters being analyzed; and

(d) Sampling and laboratory analysis conform to methods and protocols generally acceptable in the scientific community as appropriate for use in assessing the condition of the water.

(2) Data interpretation, statistical, and modeling methods shall be those methods generally acceptable in the scientific community as appropriate for use in assessing the condition of the water.

(3) The department shall develop policy:

(a) Explaining how it uses scientific research and literature for developing and reviewing any water quality standard or technical model used to establish a total maximum daily load for any water of the state;

(b) Describing the specific criteria that determine data credibility; and

(c) Recommending the appropriate training and experience for collection of credible data.