Astoria bought its own watershed in 1893, securing 3,700 acres of hills and streams around Nicolai and Wickiup mountains feeding an abundant water supply into three reservoirs and the Bear Creek Dam 12 miles east of town.
In 1895, workers trenched a transmission line winding through the wooded hills, carrying water from the dam to the city’s finished-water reservoirs.
Making sure that pipe isn’t damaged in one of the region’s many landslide zones, much less a large earthquake, is one of the most serious issues Astoria hopes to address in a 20-year update of its water system master plan.
The city recently advertised for firms that could complete the state-mandated update, expected to be conducted over the next couple of years. Firms will look at several issues identified in the 2000 water master plan. Questions around supply and demand will be fairly straightforward, said Jeff Harrington, the city’s public works director.
“We have plenty of water,” he said.
The city’s 2000 water plan projected a demand of 15,000 people, Harrington said. But Astoria hasn’t topped 10,000 people since the 1990 census. Water demands in the city are largely driven by seafood processing. The city has never run out of water and once served twice the 2.5 million gallons it currently averages, he said.
But commingled with the water study are several mandates from the state and federal governments around natural disaster resiliency and security. One is an analysis of earthquake risks to the city’s water supply.
“That’s a big problem for us, with our landslide terrain here,” Harrington recently told the City Council. “We actually have sections of water line that fail due to landslides without having an earthquake happen.”
During heavy rains four years ago, a section of pipe crossing Little Bear Creek and buried along a steep bank just below a nearby clearcut became exposed by erosion. The city was granted federal emergency funds to armor the bank with rocks.
But a resiliency study found 45 such areas where the 12-mile transmission line is at risk, Harrington said. A seismic risk analysis will look at those and other points of concern, and what the city should do to mitigate the risk, he said.
In addition to the seismic analysis, federal mandates require the city to prepare for all manner of risks to the water supply, be they natural disasters or cybercrime, Harrington said. The city must also create a plan to respond in case of an emergency.
Astoria dodged a seismic bullet when an analysis of the 107-year-old Bear Creek Dam indicated it did not need upgrades to reach current seismic codes.
“That was projected to be a little over $2 million at the time,” Harrington said. “So we were very fortunate … that we didn’t need to do that project.”
The last water master plan resulted in a fourth cell being added to the slow-sand filtration pond built in the 1990s at the main reservoir above the dam, covered reservoirs for treated water nearer to town, new water storage tanks and a small grant-funded hydroelectric plant that powers the dam.
Projects not completed from the last plan include a clear well system, the final stage in purification; an upgraded chlorine purification system previously voted down by the City Council; and upgrades to water lines for issues such as getting more water to seafood processors at the Port of Astoria, Harrington told the City Council.
“The new plan will capture those projects, update those costs and of course add new projects that will be identified,” he said.
The dam is stable and has never overtopped. But the city still needs to design an emergency spillway around the dam in preparation for 1,000-year storm, Harrington said.
“We don’t want it going over the top of the dam, because that could cause erosion on both sides of the dam,” Harrington said of heavy rains.
The city is planning to dig an emergency spillway, about 120 feet wide and at least 2 feet lower than the top of the dam, from Main Lake to Cedar Creek, a smaller feeder creek just east of the dam that connects downstream with Bear Creek.
“It was talked about 20 years ago, so (the state) is finally saying, ‘Hey, let’s get moving on this.’ So we’re just working on the concept right now. It will probably be built in the next couple of years.”