A recently issued report from a private commercial testing laboratory points to “design-build” alterations as a likely principle reason Orchard City’s new West Main water distribution line has experienced failures.
The pipeline project, which was originally planned as a $4 to $5 million improvement taking two years to complete, benefitted from federal stimulus money payments.
The town received an unsolicited “principle forgiveness loan” of $2 million for the work, and a bid came in at that amount for the entire line installation.
The pipeline, which runs from the town treatment plant to the Eckert storage tank, was completed in one construction season, not the originally planned two seasons.
The pipeline was commissioned in September 2011. The first failure of a “coupling device” occurred three months later.
That failure was followed by another one last September. A third failure occurring in frigid winter weather last December had crews scrambling to restore service due to a break that spilled over one million gallons of treated water into the freezing dark.
The private lab report on the cause of the three failures was distributed to town trustees at a work session last week. The manufacture of the HDPE polymer resin pipeline was done according to specifications, the report states. “No manufacturer workmanship defects were found within any portion of the EF (electro fused) couplings investigated.”
However, the report noted some contributing factors to the failures stemmed from installation:
• The use of “native backfill” without application of compaction work;
• Improper alignment within pipeline coupling devices and gaps exceeding manufacturer’s specifications present before sections were electrofused together; and
• The absence of “thrust blocking” to reinforce sections where directional flow of water in the pipeline was changed.
“Poor workmanship associated with the fabrication of the EF coupling joints and installation of the piping system were in evidence and contributed to the premature failure of the EF couplings,” the report states.
But those elements of the pipeline’s construction were not the “primary cause” for premature failure. That cause was the “design-build” alterations to the original engineering plans that were undertaken to accommodate elevation changes encountered during construction at certain pressure relief valve pits.
“We took a gamble at the time,” said Mayor Don Suppes about the design-build changes that were made. “We lost on that one, but re-engineering would have still cost more. I’m not totally sure we made the wrong decision.”
There are at least 50 of the couplings on the four-mile-long West Main line, reported public works staff.
According to the town’s public works staff, the failed couplings, which were attached to the HDPE polymer resin pipeline segments using an electrofusing weld, have been replaced with mechanical coupling devices that use toothed clamps and gaskets to secure fittings.