Four new vapor probes sunk into the soil near the trans-Alaska Pipeline in Thompson Pass have detected petroleum vapors, adding to concerns raised earlier this week that the pipeline may have sprung a leak.
The four probes were installed after a single initial probe registered evidence of hydrocarbons in the soil near a section of the line that began vibrating last summer, shaking hard enough at times to alarm nearby residents.
Officials of Alyeska Pipeline Service Co., reiterated that readings by the probes Thursday are inconclusive, and could be caused by an old spill or refined oil left over from construction during the 1970s.
The probes cannot tell the type or source of the hydrocarbons detected.
“We’re not ruling out anything at this point,” Alyeska spokesman Mike Abbott said.
If the pipeline is leaking, repair is going to be a challenge, officials said. Although it is close to the road, the site - 1,500 above sea level on the south slope of Thompson Pass - is steep and treacherous.
With a tractor-mounted drill that was en route Thursday, investigators can pull up soil samples from the apparently contaminated area and install monitoring instruments, the company said.
State and federal officials, charged with monitoring pipeline safety, are watching over Alyeska’s shoulder.
There is no evidence yet that last summer’s shaking, several known dents in the pipeline and the hydrocarbon readings are related. Alyeska officials have said the shaking problem occurs because of reduced flow through the 800-mile line. At low flow, turbulence develops when the oil crests at the top of the pass.
The following fields overflowed: CREDIT = Scripps-McClatchy Western Service