Sequim city councilors unanimously agreed to a letter of support for the Dungeness Off-Channel Reservoir at their Nov. 28 meeting.
Carol Creasey, Clallam County senior planner and stormwater project manager, told the six councilors — with mayor Tom Ferrell excused from the meeting — the design is at the 30 percent preliminary design phase.
“Letters of support are very important,” she said.
The county has received about $12.8 million for the project with an estimated $36 million required to complete construction of the project.
The city has been a partner of the project through its development, with the council’s letter stating to potential grantors: “Please accept this letter indicating Sequim City Council’s strong support of funding this visionary and popular off-channel reservoir project because of its scale, location, cost/benefit, and feasibility.”
City officials previously said the project would capture stormwater and help prevent flooding in the city.
“We’re still doing field work to tweak the design as more information becomes available and more work is done on modeling,” Creasey said.
The latest design updates a 2016 conceptual design, she said, with the proposed reservoir moving about 1,000 feet further south and east. At its highest point, it’d be 30 feet tall, according to county staff.
Designers couldn’t place the project further south because of existing power lines and east because of the proximity to the bluffs and the river, Creasey said.
Updated designs, she said, bring the structure 23 feet below ground surface — 8 feet shorter than the conceptual design — and “there may be more tweaks as we progress with the design.”
When asked about making the reservoir deeper, Creasey said water is moved using gravity flow and if they go deeper then they’d have to add pumps and pipes that would add to the project’s costs.
However, designers might be able to go six inches deeper with the design, she said.
Creasey reiterated a few times that county staff and partners “take safety very seriously” and that the reservoir is not a dam holding back a river, but an irrigation ditch that can be shut off.
The reservoir, she said, must be built to sustain the once-in-a-million year seismic event, such as a Cascadia earthquake.
“There’s always a risk,” she said.
However, with Sequim getting about 16 inches of rain a year, she said a once-in-a-million year event with 14 inches of rain in an hour or two is unlikely. But they’re still designing and planning for those situations, she said.
Read more about the project at clallamcountywa.gov/188/Dungeness-Off-Channel-Reservoir.
