The Kennewick Irrigation District has solved the mystery of what's wrong with the Edison Street pipeline.
It's clams, clams and more clams that have muscled their way into KID's system.
The freshwater shellfish are growing inside the 33-inch concrete pipe that carries irrigation water to about 5,000 customers.
Ed Everaert, KID engineering manager, told the board Tuesday that the clams have piled up where the pipe connects with a 21-inch mainline, creating a natural place for the bivalved aquatic creatures to attach and grow.
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That many clams in one place slow down the flow enough to affect delivery of irrigation water, Everaert said.
The answer is surgical -- replace the joint with a specially designed tapered connection, he said.
KID uncovered the problem last week while fixing a few leaks and examining about 400 feet of the concrete pipe that passes beneath the Burlington Northern Santa Fe tracks just north of Kamiakin High School along Edison Street.
The KID board last month authorized spending up to $60,000 to install a special inflatable liner in the concrete pipe, believing its steel inner pipe had rusted away.
But Everaert said a remote camera inspection of the concrete pipe showed no need for a new liner.
"The pipe integrity is good, so there is no need to line it," he said.
Instead, the camera found the clams, which Everaert said should be taken out.
Monarch Machine of Pasco will build the 6-foot-long tapered connection, also known as a reducer, and KID's crews will install it Friday.
That will be quick enough to keep from delaying work by the city of Kennewick's contractor to widen Edison Street and install turn lanes in the same area, Everaert said.
"We've got the city wanting us to get out of their way by Monday," he said.
The cost for the clam fix is $4,800 for parts and whatever it costs KID's crew to install it.
And that is much less than the $60,000 that was expected for lining the pipe, Everaert noted.