Down-To-Earth Job -- Sea-Tac's Third Runway To Get Its Fill Of Dirt

Let's say you've been looking for a better view, but you don't want to leave the neighborhood.

Instead, you bring in fill dirt to raise your property so you can see over all your neighbors. Somehow you get the dirt to form a nice column straight up from your typical 5,000-square-foot city lot.

Only you get a little carried away. As you sit and watch, hundreds of thousands of truckloads of dirt are dumped on your yard, raising it 77,000 feet - more than five times the height of Mount Rainier.

What you're looking at is 14.25 million cubic yards of dirt, an amount that might be unimaginable to you, but not to Michael Cheyne, a project manager at Seattle-Tacoma International Airport.

That's the amount of fill dirt Cheyne says must be moved to the airport to accommodate the $455 million third runway, approved by the Port of Seattle and Puget Sound Regional Council.

The Port's current projection is that more than 17 million cubic yards of fill is needed for the project, but staffers say at least 3 million of that will come from airport property, by flattening a hill that sits on one part of the new-runway site.

In the Seattle area, we don't shy away from moving a little dirt. Early this century, civic architects decided Denny Hill provided too much of an obstruction downtown, so they washed 5 million cubic yards of it into Elliott Bay.

Two decades later, another 5 million cubic yards in the Denny area was lopped off, and by the time it and other regrade projects were completed, some 16 million cubic yards of dirt had been moved to give the city a more user-friendly profile.

Sea-Tac needs fill dirt because the planned third runway will sit on a plateau that simply isn't there now. Instead, the corridor is a string of dips and valleys, as deep as 145 feet.

By month's end, crews will begin to clear brush and move earth on property the airport already owns, and a consultant will gather information to appraise property the Port needs to purchase.

Opponents, which include most of the nearby cities, will stop the project if they can, and this week they filed their second legal challenge to it. They say the plan is based on faulty information that understates the harm the project will do to the environment and surrounding communities.

As the earth-moving job is examined, Cheyne says he knows how much fill dirt is needed and has an idea how much that part of the project will cost: $120 million.

But there are two key things he doesn't know: where the dirt will come from and how it will get here.

"We are talking to everybody and anybody who will talk to us," Cheyne said. "We're looking at a number of options, examining the environmental, political and economic implications."

Sources of dirt include gravel pits on Maury Island, at North Bend, at Black Diamond, at Maltby or at DuPont - even as far away as Vancouver Island.

Finding the dirt isn't the biggest challenge; moving it is.

Trucks, barges, a new pier, a new rail spur and a giant conveyor belt up to four miles long all are being examined in a study the Port staff hopes to complete by mid-September.

The report won't select a method, but may eliminate some that could be too costly or too difficult.

Each delivery method presents what Cheyne calls "some pretty significant hurdles." And each would undoubtedly add ammunition to the lawsuit filed by third-runway opponents seeking to block the project.

Some of the most intriguing possibilities involve moving the dirt on a giant conveyor belt to reduce the congestion caused by the nearly 800,000 truck trips that would be required.

Where the conveyor would go depends on where the dirt comes from. For example, a conveyor from a waterfront location could be useful if the dirt arrives by barge.

Possible routes are:

-- From Des Moines. A conveyor nearly three miles long could carry dirt from a pier that would be built on the Des Moines waterfront. The route would follow a sewer-district maintenance road up the Des Moines Creek drainage to Port property.

-- From the Tukwila/Renton area. If the dirt is carried by rail from an inland area, a rail spur may be built near the former Longacres racetrack site where the fill could be unloaded. Then a three-mile conveyor would carry it on a path following Interstate 405 and Highway 518, traveling through a tunnel under Interstate 5.

-- From the Duwamish Waterway. The longest conveyor route examined, about four miles, may be used if the dirt is barged to an off-loading facility along the Duwamish, then transferred to a conveyor running along Highway 509.

Engineer Hank Hopkins, who has built conveyors at the Hanford nuclear reservation and on a Valley Freeway project in South King County, already has secured the right of way for a route through sewer-district property at Des Moines.

He envisions a 7-foot-wide conveyor, enclosed and fenced to keep children and animals out, and says it would be safer and quieter than using trucks.

Des Moines city officials, however, oppose the runway and have indicated they may refuse a permit for the conveyor.

If the dirt is hauled to the airport on trucks, opponents fear the noise, congestion and damage to roadways from up to 70 truck trips per hour each workday for three years.

The terrain around the airport and the Federal Aviation Administration's (FAA) requirements for separation distance between runways explain the need for the massive earth-moving project.

Under FAA rules, Sea-Tac's two existing runways are too close together to allow streams of traffic to land on each when low clouds hamper visibility, which occurs about 45 percent of the time.

Achieving the required 2,500-foot separation pushes the new runway off the plateau the airport sits on, meaning that before the runway can be built, the plateau must be extended westward.

"The public perception is that you pile up dirt and put a runway on it. It's not that simple," said Michael Feldman, director of aviation planning for the Port.

Each 1-foot layer has to be placed and then compacted to 40 percent of its original volume.

The quality of the dirt is an important consideration. Earth with a high silt content is more vulnerable to erosion and less desirable as fill, though it can be used for part of the job.

A higher-quality fill, such as gravel and sand, that compacts and drains well is needed for ground directly under the runway, to bear the weight of planes loaded with passengers and fuel, such as a 300-ton DC-10.

The runway itself will be a layer of concrete 18 inches thick sitting on an 8-inch base of crushed rock.

Space for the runway and a buffer zone around it will mean demolishing more than 600 homes and apartments. Still uncertain is whether the Port also will need to acquire some 100 light-industrial businesses south of the runway, or just purchase easements to fly over them.

Construction is likely to take five to seven years, Cheyne estimates, meaning that if legal challenges don't halt or delay the job, the first planes might touch down in 2001.

Opponents say it's a short-sighted solution to handling the area's air traffic, calling it the most expensive runway ever built in the U.S.

And while Port officials admit the job is extremely expensive, they hope to secure $267 million in federal money from airline-ticket taxes and say the additional runway will reduce the costs of airline delays. ----------------------------------------------------------------- Third runway: growing plans

Seattle-Tacoma International Airport has two runways. However, because they are close together, only one runway now can be used for landings during the 44 percent of the time when the weather is poor. Building a third runway will permit landings on two runways in all weather. It also will make runway maintenance easier. Now, maintenance is done a few hours at the time in the middle of the night. With three runways, one could remain closed until the work was finished.

Going west

Because the new runway must be 2,500 feet from the primary runway so both can be open to landings, the plateau the airport sits on must be extended westward. That area is a series of valleys that must be filled for construction of the extensive reinforced fill embankment. Hundreds of properties in the path will be condemned and demolished.

Building a hill

Constructing the embankment will require a massive earth-moving project to fill those valleys. The 14.25 million cubic yards of fill that must be hauled to the site is 1.4 times as much as was sluiced or hauled away during both phases of the Denny Regrade. Fill thicknesses will range from 30 to 100 feet, with a maximum depth of 145 feet. Fill depth will be greatest to the north. In areas where there are seismic concerns, fill must be removed and replaced.

Bottom layer: Low-quality, fine-grained soil, such as silt and clay.

Because it doesn't compact well, heavy equipment will compress each one-foot layer to 40 percent of its original volume.

Top layer: Coarse-grained soil, such as crushed rock and sand, which compact and drain well.

Runway construction

The runway will be built from concrete-block panels connected by dowels. It is designed to last at least 40 years.

Pavement: 18 inches of heavily reinforced concrete (Portland cement) on an 8-inch base of crushed rock Segments: 20-by-20-foot concrete-block panels; smooth steel dowels (1 1/2 by 20 inches) at joints will transfer weight from block to block.

Moving fill to the site

The project requires 17.5 million cubic yards of fill. Some is available on site, but 14.25 million cubic yards must be hauled there. The Port of Seattle is studying several methods, considering impact on traffic and cost.

Hauling options:

Truck: Each truck holds 18 cubic yards of fill, requiring 70 truck trips per hour, 15 hours a day, five days a week for nearly three years.

Conveyor: Three routes being considered:

-- From Des Moines: A pier would be built on the waterfront. A conveyor nearly three miles long could carry fill along a sewer-district maintenance road up the Des Moines Creek drainage to port property.

-- From the Tukwila/Renton area: A rail spur would be built near the former Longacres site, where fill could be unloaded. A three-mile conveyor would carry it on a path following I-405 and Highway 518, then through a tunnel under I-5.

-- From the Duwamish Waterway: Fill would be barged to an existing or new off-loading facility along the Duwamish, then transferred to a conveyor about four miles long running along Highway 509.

Visualizing the hauled fill: The 14.25 million cubic yards that must be hauled compared to:

-- 1.4 times the amount of fill removed during both phases of the Denny Regrade. -- 5.75 times the volume of the Kingdome

-- 60 percent of the mud underpinning Harbor Island (dredged from Duwamish Waterway and taken from top of Beacon Hill)

Facts about the third runway Length: 8,500 feet (Runway 1 is 11,900, Runway 2 is 9,425 feet long) Width: 150 feet with 35-foot shoulders on each side. Height: 14 feet lower than 2nd runway (16R-34L) Distance from first (primary) runway: 2,500 feet (allows landings on both runways under instrument flight rules) Runway safety area: 250 feet each direction from center of runway Accommodation: Estimated 99 percent of fleet in year 2020; only certain large jets, such as the future MD12, couldn't land. Cost: Construction, $405 million ($120 million of that would pay for fill and transporting it); acquiring additional land for mitigation, $35 million; wetlands construction and other mitigation, $15 million. To help pay for the project, the port is seeking $267 million in federal money already collected from airline-ticket taxes. Condemnation: 388 single-family homes, 260 apartment units and some businesses will be demolished. Wetlands destruction: Ten acres of wetlands will be filled and 26 acres created in Auburn to make up for the loss. Estimated time for completion: Five to seven years.

Source: Port of Seattle; reporting by Karen Kerchelich and Jack Broom; Seattle Times research ----------------------------------------------------------------- CHRIS SOPRYCH / SEATTLE TIMES: