​About 3:28 p.m., Pacific daylight time, on June 10, 1999, a 16-inch-diameter steel pipeline owned by Olympic Pipe Line Company ruptured and released about 237,000 gallons of gasoline into a creek that flowed through Whatcom Falls Park in Bellingham, Washington. About 1 1/2 hours after the rupture, the gasoline ignited and burned approximately 1 1/2 miles along the creek. Two 10-year-old boys and an 18-year-old young man died as a result of the accident. Eight additional injuries were documented. A single-family residence and the city of Bellinghams water treatment plant were severely damaged. 

We determined that the probable cause of the June 10, 1999, rupture ​of the Olympic pipeline in Bellingham, Washington, was 

1. ​Damage done to the pipe by IMCO General Construction, Inc., during the 1994 Dakin-Yew water treatment plant modification project and Olympic Pipe Line Company s inadequate inspection of IMCOs work during the project; 
2. Olympic Pipe Line Company s inaccurate evaluation of in line pipeline inspection results, which led to the company s decision not to excavate and examine the damaged section of pipe; 
3. Olympic Pipe Line Company s failure to test, under approximate operating conditions, all safety devices associated with the Bayview products facility before activating the facility
4. Olympic Pipe Line Company s failure to investigate and correct the conditions leading to the repeated unintended closing of the Bayview inlet block valve, and 
5. Olympic Pipe Line Company s practice of performing database development work on the supervisory control and data acquisition system while the system was being used to operate the pipeline, which led to the system s becoming non-responsive at a critical time during pipeline operations.
   

​As a result of its investigation of the June 10, 1999, rupture of an Olympic Pipe  Line Company pipeline in Bellingham, Washington, we made the following safety recommendations:

To the Research and Special Programs Administration:

• ​Develop and issue guidance to pipeline operators on specific testing procedures that can (1) be used to approximate actual operations during the commissioning of a new pumping station or the installation of a new relief valve, and (2) be used to determine, during annual tests, whether a relief valve is functioning properly. (P-02-4)
• Issue an advisory bulletin to all pipeline operators who use supervisory control and data acquisition (SCADA) systems advising them to implement an off-line workstation that can be used to modify their SCADA system database or to perform developmental and testing work independent of their on-line systems. Advise operators to use the off-line system before any modifications are implemented to ensure that those modifications are error-free and that they create no ancillary problems for controllers responsible for operating the pipeline. (P-02-5)