Created as a detention pond to manage stormwater runoff from the north end of the Hewlett-Packard campus, Stewart Lake has become a popular destination for HP employees to stroll, jog or even do a little birdwatching on their lunch break.
Fish, waterfowl, turtles and other wildlife make their homes in the 5-acre lake, which allows for settling of stormwater before it flows to the nearby Willamette River and offers a scenic oasis in the midst of the 140-acre high-tech industrial park.
But now, more than three decades after HP’s Corvallis site opened for business in 1976, a thick layer of sediment has built up on the bottom of the lake, reducing its capacity to handle large amounts of runoff from a heavy rain.
To extend the useful life of the lake, HP wants to dredge more than 30,000 cubic yards of material — about 3,000 dump trucks’ worth — from the bottom and haul it offsite.
“Over the last 30 years since we’ve been here at this campus, it’s filled in approximately 4 to 5 feet,” said Tammy Casper, an environmental program manager for the company.
“If we don’t do this, it will fill in over time and not be an aesthetic feature.”
Much of the sediment on the lake bottom is silt, but there’s also a fair amount of organic material — think rotting leaves and accumulated goose poop — that could make Stewart Lake a less attractive place.
“It could become more odorous over time,” Casper said.
HP has applied for a dredging permit from the U.S. Army Corps of Engineers and a water quality certification from the Oregon Department of Environmental Quality. Both agencies are soliciting public comment on the proposal.
The permit application calls for the use of a backhoe or a suction dredge to remove the sediment and proposes disposing of the material at a mid-valley rock quarry, where it would be used as fill.
The material will be evaluated for potential contaminants, but the Corps of Engineers does not anticipate finding any waste from HP’s industrial operations, which is handled separately.
“There are no known sources of potential contamination upstream,” said Benny Dean, a project manager for the federal agency. “There’s nothing that suggests this material is contaminated.”
HP could be required to do some wetland mitigation to offset the impact of the dredging on fish or other aquatic life in Stewart Lake, but Dean doesn’t foresee any need for that.
Casper said the company would follow all applicable rules and use “environmentally sound options” to minimize harm to wildlife.