Baker City’s long-term project to replace the nearly century-old, leak-prone concrete pipe that carries drinking water from the Elkhorn Mountains to town is continuing this summer.
The city is spending an estimated $600,000 to install 3,880 feet of 20-inch diameter ductile iron pipe along the line between a settling tank near Elk Creek and the city, said Michelle Owen, public works director.
The installation, which is being done by city workers, primarily Justin Plumbtree and Brian Johnson, will complete the section of new pipe between the settling tank and the reservoir on the hill at the city’s southwest corner.
The city’s plan for 2020 is to return to what’s known as the “mountain line,” and install new pipe between Mill and Marble creeks, several miles north of Elk Creek, Owen said.
“We’ve kind of moved around on the mountain itself, but this summer’s project is the final connecting piece from Elk Creek,” Owen said.
The moving around was dictated in part by a legal conflict between the city and the U.S. Forest Service over the width of the easement the city has for the mountain pipeline, which is buried beneath a narrow road that runs across the eastern slopes of the Elkhorns from Goodrich Creek south to Elk Creek, Owen said.
The pipeline road, which forms the eastern boundary of the city’s 10,000-acre watershed, follows the route of a ditch originally built during the Civil War to transport water to mines in the Auburn area southwest of Baker City.
The city later bought that ditch and the water rights that went with it.
The open ditch was later replaced with a wooden flume and later, mainly in the 1920s and 1930s, with a concrete pipe, Owen said.
The problem with that pipeline is that it was made of three-foot segments, which necessitated thousands of joints. Over the decades many of these joints leaked, and tree roots also cracked the concrete in places.
When the city was applying in the early 2000s for a state permit for “aquifer storage and recovery” — diverting water from mountain streams and springs into a well during the winter and spring as a supplementary source — officials required the city to test the mountain line, Owen said.
That test showed that when the pipe is flowing at full capacity — which doesn’t happen often — as much as 22% of the water was lost to leaks, she said.
The precipitated the current replacement project, which includes about 17 miles of pipe.
So far the city has replaced less than one-third of that distance.
The new pipe is made of ductile iron on the section from the Elk Creek settling tank to town because that section, which has both uphill and downhill sections, can reach high water pressures, Owen said.
The mountain line, by contrast, which follows a very gentle grade, has little pressure, so the new sections are made of PVC.
The mountain line connects at the Elk Creek settling tank to a pipe that carries water from Elk Creek itself. That pipe, though made of concrete, is of much more recent vintage, having being installed in the early 1980s.
The city also has a pipe that runs from Goodrich Creek across Baker Valley to town. That steel pipeline was installed in 1961, and it carries water from Goodrich Lake, a source the city usually taps starting in August when flows from the watershed itself decline at the same time water use tends to peak.
The final part of the system is the Marble Creek Intertie, which runs down from Marble Creek and connects to the Goodrich pipeline.
The intertie allows the city to divert water from the north side of the watershed — between Marble Springs and Goodrich Creek — into the Goodrich pipeline if needed, Owen said.
The Marble Creek Intertie, made of steel, was built in 1983.
Once the city crews have finished the Elk Creek segment, probably in late August or early September, they will move an excavator to Goodrich Lake to start work on a seepage problem near the earthen dam the city built to increase the capacity of the natural lake.
On July 4, after a city worker noticed water coming into town was cloudy, the source was traced to seepage on a slope below Goodrich Lake that had caused rocks and dirt to partially block the water intake.
On July 5 two engineers from the U.S. Army Corps of Engineers, Troy Gilbert and Joy Hartl, examined the dam and found no structural problems.
The engineers also looked at the area where dirt and rocks had slid, an area measuring about 150 feet by 75 feet, according to a report written by Dwayne M. Weston, chief of the engineering and construction division, and dam safety officer for the Corps of Engineers’ Walla Walla, Washington, District.
“There were multiple active seeps from the slope failure area that appeared to be running clear water, and picking up sediment as it flowed down the face of the slope failure,” the report reads.
The engineers recommend the city clear the water outlet below the dam and rebuild the slope where debris slid.
Owen said the city’s plan is to remove rocks from the outlet this year and build a retaining wall in the area where seepage caused the slide in July.
Over the winter the city will work to design an improved drainage system for the site that could be built in 2020.
Owen said she visited the lake on Aug. 6 with Brandon Mahon, the city’s engineer from Anderson, Perry & Associates, and with Keith Mills, a dam inspector from the state.