(1) Purchases of any materials, supplies, or equipment by the district shall be based on competitive bids except as provided in RCW 87.03.435 and 39.04.280. A formal sealed bid procedure shall be used as standard procedure for the purchases made by irrigation districts. However, the board may by resolution adopt a policy to waive formal sealed bidding procedures for purchases of any materials, supplies, or equipment for an amount set by the board not to exceed fifty thousand dollars for each purchase.

(2) The directors may by resolution adopt a policy to use the process provided in RCW 39.04.190 for purchases of materials, supplies, or equipment when the estimated cost is between the amount established by the board under subsection (1) of this section and a maximum amount set by resolution adopted by the board for purchases up to fifty thousand dollars exclusive of sales tax.