A Tualatin-based subcontractor took responsibility Thursday for breaching an underground natural gas pipeline that caused a destructive explosion a day earlier in Northwest Portland, but a spokesperson said the company obtained utilities location information and made necessary notifications before digging began.

Two explosions Wednesday morning ripped apart two buildings near Northwest 23rd Avenue and Glisan Street less than an hour after the gas leak was reported.

Loy Clark Pipeline Co. of Tualatin stopped short of blaming any entity for the explosion, saying the incident is under investigation.

On Thursday, investigators for the Oregon Public Utilities Commission, along with NW Natural representatives and others, sifted through piles of debris at the blast site along the trendy commercial strip, looking for clues. A NW Natural spokesperson said investigation results - explaining how the rupture occurred and how the blasts were ignited -- would not be known for weeks or even months.

Loy Clark is working with Bremik Construction Co. of Portland, the buider of a mixed-used building at the southeast corner of 23rd and Glisan, the former site of a Plaid Pantry.

"In terms of where you dig and don't dig -- that's information our crew would need and have before they would dig," Loy Clark spokesperson Andrea Fonkert said.

Asked if the crew had correct location information or may have dug inadvertently in the wrong location, Fonkert said, "that's under investigation," referring several questions to NW Natural.

Bremik posted a statement Wednesday night on its Facebook page noting that the subcontractor's work preceded the explosion, saying, "We understand utility notifications, locates and protocols were in place and clearly marked before work proceeded."

"Locate" is a term used in the utilities and construction industry to describe the process of utilities marking the location of lines -- for the use of construction crews -- to avoid damaging those lines.

NW Natural issued a statement Thursday evening saying the source of ignition for the blasts was part of the ongoing investigation.

In an interview, NW Natural spokesperson Melissa Moore said, "It is possible somebody could have a locate and still accidentally hit a line."

NW Natural's statement also said Loy Clark contacted NW Natural on Sept. 12 requesting information about the location of the utilities underground lines near the construction site at 23rd and Glisan and that the locations were marked Sept. 13.

The NW Natural release also says the line that was damaged was a 1-inch coated steel pipe installed in 1985. In 1996, at the request of a customer, NW Natural moved the meter and replaced six feet of service line.

The statement says a scheduled leakage and atmospheric corrosion survey was completed on this pipe on Jan. 15, and no leaks or corrosion were found.

The NW Natural statement says the utility has received questions about Oregon locate requirements, which can be found at www.digsafelyoregon.com. In summary, the statement says, the law requires the following for excavation:

Call for a locate 48 business hours before digging

Get the area marked and maintain the markings

If a pipe is present, hand excavation is needed to maintain the pipe's integrity.

The investigation will determine if "procedures and requirements were followed," the statement added.

Bremik is the contractor for a three-story plus penthouse retail commercial building at 23rd and Glisan in the Historic Alphabet District, according to Portland city records. The 36,000-square-foot structure, with a basement parking garage, is slated for the former Plaid Pantry site and its parking lot.

The project owner is Rosehill Investments Inc. LLC of Seattle, and the project applicant is Paul Jeffreys of Ankrom Moison Architects in Portland, city documents show. The project has a valuation of $14.8 million.

Two blasts ignited by a natural gas leak occurred in quick succession about 9:40 a.m. Wednesday in the 500 block of Northwest 23rd Avenue, rocking the entertainment and shopping district and sending up a smoke plume of billowing smoke visible across the city.

Eight people, including three firefighters, were injured, but none suffered life-threatening injuries.

-- Allan Brettman

503-294-5900

@allanbrettman