(1) A contract awarded in whole or in part for the purchase of compost products as a soil cover or soil amendment to state highway rights-of-way shall specify that compost products be purchased in accordance with the following schedule:
(a) For the period July 1, 1996, through June 30, 1997, twenty-five percent of the total dollar amount purchased;
(b) For the period July 1, 1998, through June 30, 1999, fifty percent of the total dollar amount purchased. The percentages in this subsection apply to the materials' value and include services or other materials.
(2) In order to carry out the provisions of this section, the department of transportation shall develop and adopt bid specifications for compost products used in state highway construction projects.
(3)(a) For purposes of this section, "compost products" means mulch, soil amendments, ground cover, or other landscaping material derived from the biological or mechanical conversion of biosolids or cellulose-containing waste materials.
(b) For purposes of this section, "biosolids" means municipal sewage sludge or septic tank septage sludge that meets the requirements of chapter
70A.226 RCW.