It’s difficult to visualize 150,000 cubic yards of dirt, but try this:
That’s enough to fill 45 Olympic-sized swimming pools. Or cover 70 football fields — end zones included — a foot deep.
Or, it’s the amount of dirt being dug out and hauled from a field near the Brush Prairie/Hockinson area in only a matter of weeks. At its peak, the work meant up to 400 daily truckloads rumbling along quiet rural roads.
“It’s this constant stream of large trucks going by,” said Janet White, who lives in Brush Prairie. “It’s stunning how many trucks are going in and out of there constantly.”
The excavation is a little-known part of the $133 million Salmon Creek Interchange Project. Washington State Department of Transportation crews are transforming the 16-acre area — through an agreement with the private property owner — into a wetland. The work, required by state environmental rules, is intended to make up for another wetland impacted by the main project at the Interstate 5/Interstate 205 interchange.
The new wetland site is several miles away, but it’s in the same Salmon Creek watershed, said project manager Allen Hendy. That’s one of several things planners look at in locating a wetland mitigation project, he said.
The excavation took plenty of Brush Prairie residents by surprise when it began this summer. Some have complained of the noise, dust and congestion caused by the dozens of trucks hauling dirt away by the hour. White said she’s heard of neighbors who used to run in the area but now steer clear.
WSDOT reached out to inform residents before the excavation began, Hendy said. Crews have also tried to alleviate at least one of residents’ concerns by spraying down access roads with water to limit the amount of dust and dirt kicking up, he said.
The speed of the excavation means the worst of those impacts will be short-lived. Workers should finish digging by the end of next week, Hendy said.
“It’s quite an operation out there,” said Heidi Sause, a WSDOT spokeswoman.
One recent afternoon saw a well-organized parade of dump trucks roll through what used to be a grassy field, now dug down 6 to 9 feet, to a field of dirt. As a line of trucks pulled in from Northeast 159th Street, they formed a small queue, received their loads, then exited through another driveway onto Northeast 152nd Avenue. Each load is taken to one of several locations in Clark County, Hendy said, including other development sites. A “truck orchestrator” helps coordinate the one-way loop, he said.
Despite the steady stream of trucks, the vehicles lined up only about five deep Thursday.
“This is really slow compared to where we were a couple weeks ago,” Hendy said.
Once the entire area is dug out, workers will spread topsoil, then mix it with compost. A planting, coordinated with the state Department of Ecology’s Washington Conservation Corps, is planned for before rains return to fill what will be a seasonal wetland, Hendy said.
Most people associate WSDOT with roads, highways, concrete and the like — not wetlands. But the transportation agency often finds itself overseeing environmental work, including wetland mitigation, Sause said. Just about any major project buries or changes a natural area, she said, and broadening regulations apply much more scrutiny than a generation ago.
“It’s not something that people necessarily think about right off the bat,” Sause said. “We do a lot of work on the environmental side of the house.”
In this case, the section of wetland, just west of I-5, that’s going to be affected hasn’t been touched yet. That will change when crews extend Northeast 139th Street with a bridge over the busy freeway interchange, beginning later this year.
The Washington executive order driving much of the state’s wetland policy today dates back to 1990. Still, some haven’t quite gotten used to the idea of creating a wetland from scratch.
“I always think of wetlands as being more naturally occurring,” White said.
Project moves ahead
The Salmon Creek Interchange Project is WSDOT’s biggest active project. After Clark County coordinated its first two stages, WSDOT has taken the lead for stages three and four.
Stage 3, now under way, will add one lane to both directions of I-5 between Northeast 139th and 179th streets. Plans also call for a new lane on the northbound off-ramp from I-205 to Northeast 134th Street.
Drivers can expect nightly lane closures on I-5 starting Monday as crews begin widening the freeway. Traffic will be shifted to the outer shoulder on both sides of the freeway.
Multiple stormwater ponds and other facets of the project are also in progress.
Stage 4, the new 139th Street bridge, will begin later this year.
The entire Salmon Creek project is scheduled to wrap up in 2014.
Eric Florip: 360-735-4541 or firstname.lastname@example.org.