Last week’s mineral oil spill at The Dalles Dam may have caused the deaths of 185 juvenile shad — but that cannot yet be proven.
“It is entirely possible that these shad could have died before this spill and until we get a toxicology report we just won’t know,” said Matt Rabe, spokeperson for the U.S. Army Corps of Engineers.
As of press time on Tuesday, he said Oregon and Washington state wildlife officials had not found any birds with oiled wings or other injured animals.
And both the Wasco-Sherman Health Department and the Agency for Toxic Substances and Disease Registry, affiliated with the Center for Disease Control, have rated the risk to humans as “extremely low.” Rabe said the Corps will announce the exact cause of death for the shad as soon as it gets the official word from scientists.
“We take these matters very seriously and we have coordinated a cleanup effort with state and federal agencies that we feel is going very well at this point,” he said.
Last Thursday, an unknown volume of oil was discharged into the Columbia from above The Dalles Dam. The problem was blamed by the Corps on the seal failure of an electrical transformer.
The unit was located on the roof of the powerhouse and was exposed to freezing temperatures that cracked the seal. The light-grade mineral oil that was used as a coolant for the transformer contains polychlorinated biphenyls in a concentration of 8 parts per million. Rabe said that level is considered by the the U.S.
Environmental Protection Agency to be non-hazardous.
Rabe said the exact amount of oil that escaped into the river is unknown, although officials plan to pinpoint that number this week. He said the transformer contained three large boxes that each held up to 6,000 gallons oil.
However, the unit had been shut down last fall and one of the boxes completely drained at that time. A maintenance crew had also removed a large quantity of fluid from another box just prior to the spill. The contents remaining after the spill have since been removed and officials are reviewing work records to determine the amount of seepage.
“We’re still doing the math to figure out how much and hope to have a number within the next day or two,” said Rabe.
NRC Environmental (formerly Foss Environmental) is conducting the cleanup and has placed 4,000 “booms” of absorbent materials at sites where the oil has pooled and along the mouth of tributaries to prevent contamination. Rabe said oil has been collected at Bonneville Dam and some sheen has been observed downriver from that hydropower plant.
However, he said both Oregon and Washington environmental protection agencies have determined those patches of oil are small enough to be “nonrecoverable,” according to Rabe.
The mop-up effort is expected to be completed by the end of the week.