Wash. Admin. Code § 516-32-050
Procedures shall be established for securing telephone, written, or electronic quotations from contractors on the appropriate small works roster to assure that a competitive price is established and to award contracts to the lowest responsible bidder. Bids may be solicited from all appropriate contractors on the roster or, alternatively, from at least five contractors who have indicated the capability of performing the kind of work being contracted. If the estimated cost of the work is from $250,000 to $350,000, and bids are not solicited from all appropriate contractors, all appropriate contractors must be notified that bids are being solicited. Detailed plans and specifications are not required as part of the bid invitation.
Wash. Admin. Code § 516-32-050