Loy Clark Pipeline gave authorities the wrong location to mark utilities on Northwest Glisan Street, an error that led to mistakenly rupturing a natural gas pipeline and causing an explosion last year that obliterated one building, damaged others and seriously injured a Portland firefighter, an Oregon Public Utility Commission staff report concludes.

The report says Loy Clark requested utilities be marked on the south side of Glisan, but its crew dug on the north side. As a result, a Loy Clark backhoe excavator damaged the 1-inch-diameter steel NW Natural service line, 30 inches below the surface. The report does not name any Loy Clark employees.

While the Tualatin-based subcontractor has previously taken responsibility for the blast, the details of what led to the explosion had not been made public before the utility commission's staff report.

The report, posted Thursday to its website, also faults Loy Clark for giving insufficient notice to regulators about its excavation plans for installing a junction box in a sidewalk on Glisan for its client, Comcast. The project called for replacing a telecommunications and cable television main line.

The report says property damage and losses in the Oct. 19 explosion and aftermath totaled $17.2 million.

The commission staff made three recommendations:

"Before opening an excavation, an excavator should verify that it has identified the correct location and verify the presence of clearly visible field markings noting the presence or absence of underground facilities in the excavation area.

NW Natural should "ensure that all first responders have the skills and experience to quickly identify and actively participate in the Incident Command System that may be established by public officials during emergencies. NW Natural should engage in outreach to electric utilities and other utilities along its pipeline to coordinate emergency response. Roles and responsibilities must be clearly defined for all parties."

Excavators should "immediately call 9-1-1 if (pipeline) damage causes an emergency." The commission staff added that it would seek to change reporting rules to emphasize the importance of contacting emergency response authorities, noting that Loy Clark contacted emergency authorities 19 minutes after it contacted NW Natural about the line damage.

A spokesperson for Loy Clark said the company was reviewing the staff report's findings. A spokesperson for NW Natural said "we did follow all of our emergency response protocols effectively."

The staff report reviews the facts of the line breach, explaining that the Loy Clark crew "severed a pipe connection to a valve. The broken connection resulted in a release of natural gas that migrated under the sidewalk through a vault and began to accumulate in the basement of the building located at 500 N.W. 23rd Ave."

A first explosion in the building happened at 9:38 a.m., originating in the basement of the building, followed by a second explosion. The report says a third explosion "was recorded on the 9-1-1 dispatch log at or near the same time."

The report says that when a Loy Clark representative called the 9-1-1 Bureau of Emergency Communications, 19 minutes after notifying NW Natural, the caller reported hearing "a loud roaring out of the shutoff valve."

The utility commission is scheduled to discuss the staff report - which was produced about three months after its original expected completion date -- at its meeting Thursday in Salem. The spokesperson for Loy Clark said it has not been determined if a company representative would attend the meeting.

--Allan Brettman

503-294-5900

@allanbrettman