Clark Public Utilities had a problem. It needed to replace a water main that connected wells in Salmon Creek Regional Park to a pipeline network to the north, but to get there it had to traverse Salmon Creek and a steep bluff to the north.
“So six years later, it’s still going on. Hopefully will be done in year seven,” said water engineering manager Russ Knutson. “It’s been the hardest job I’ve done in 25 years.”
Hard not because of the technical work involved but because of the permitting work associated with it.
It started in 2012 when a water main broke near Salmon Creek on the south side of the park. The broken line spilled some 11 million gallons of water before workers could find it — a challenge considering the line ran alongside the creek.
In 2013, the utility thought it could drill horizontally beneath the creek, run the pipe through the gap and then dig a trench up the slope, but that wouldn’t work. The slope material has evidence of an ancient landslide, its loose, rocky soil, choked with clays, mud and sand not conducive to the project. Project leaders then considered ramping a pipe into the ground and then drilling it out, but costs quickly ballooned.
“We got to looking at $700 per foot to drill. We estimate today’s time frame we spend … $120 a foot,” Knutson said. “That’s when we called a big timeout real fast.”
The utility couldn’t just not install the pipe — it’s part of the main water system, serving about 32,000 customers.
It was a challenging project. The bluff was too loose to go up directly, Interstate 5 hemmed in planners on one side, and they had an existing crossing at Salmon Creek that they essentially had to use. That creek crossing was created in the 1980s by diverting, digging up and reverting the creek, work that Knutson doubts current environmental regulations would allow.
With a team of biologists, geologists and geotechnical engineers, among others, and after walking around the wetlands and the problematic slope, Clark workers evolved a new route.
“Just trying to get a route that’s sensitive to the environment and the most cost-effective to the customers,” Knutson said.
The line runs to the northwest through the park and goes beneath the creek, then runs for several hundred feet before it takes a gentle left and then two hard rights. Ultimately, it goes northeast to run under Northwest Hermann Drive –still uphill, but a gentler slope than the original route they considered.
The original route would have replaced 2,300 feet of pipe. So far, the utility has already done about 1,300 feet of pipe in the project’s first phase. Last week, it awarded a contract to complete the second phase. That work will entail laying another 1,900 feet, which should be finished by next summer.
Including some extra work, the project landed at about $260 a foot; higher than normal, but still lower than where it started.
“It’s a good route,” Knutson said. “It’s not a direct route, but it’ll definitely serve its purpose.”
