Official says sewer tank had cracks
A concrete sewer tank lid that broke apart in a fatal explosion last May already had hairline cracks prior to the accident, according to a Spokane city official who is familiar with details of an independent investigation into the catastrophic failure.
The new detail emerged after members of the Spokane City Council were briefed Thursday in a closed-door session by investigators from Exponent Failure Analysis Associates of Menlo Park, Calif.
Councilwoman Cherie Rodgers, who attended the session, said the experts analyzed old aerial photographs and other evidence to discover the pre-existing faults in the damaged “digester,” one of three large tanks used to process sewage solids at the plant along Aubrey L. White Parkway. Two remaining tanks are still in operation.
Rodgers said the remaining tanks will need repairs, but are not in danger of failure.
It was not clear how much of a role the cracks may have played in the accident. Exponent inspected and analyzed pieces of concrete from the plant as part of its $443,000 investigation under contract with the city.
Additional details were expected to be made fully public at 1:30 p.m. today in Council Chambers at City Hall. The session will be broadcast live on Cable Channel 5 and in webcast at www.spokane city.org.
The report comes one month after the state Department of Labor and Industries issued 16 vio-lations of worker safety rules in connection with the accident.
Twelve of the violations carried fines totaling $66,600. The city has appealed some of the vio-lations, and is asking for additional time to implement required changes in written procedures, operating manuals, hazard analyses and training programs.
The accident claimed the life of maintenance mechanic Mike Cmos Jr. who went onto the roof of the overflowing No. 3 tank in an attempt to contain sewage as it was leaking from vents in the roof. Two other workers were seriously injured when the roof violently broke away from walls of the 2 million gallon tank, sending a wave of sludge across buildings, onto the ground and over nearby workers. Some of the sludge went into the Spokane River.
On Thursday, council members convened in a closed-door executive session for a briefing on potential legal liability in the case. L&I investigators did not identify a cause, but cited failures in overall supervision of the plant and its operations.
City officials this morning were planning to give a briefing to family members of Cmos as well as the two injured workers and their families as a courtesy prior to making the report public, said Mayor Jim West.
Workers at the plant had reported problems in a sludge processing system that had been installed more than a year ago to increase the plant’s efficiency. Operators were moving sludge into tank No. 3 just before the accident. Unexplained fluctuations in gas pressures and sludge levels were reported during the transfer. The spilling sludge was first spotted a short time before the lid burst along a seam connecting it to the walls. Cmos was trapped on top of the roof. His body was discovered near the bottom of the tank two days later after most of the remaining sludge was removed.