Crews cleared the hillside this week above Interstate 405 through downtown Renton where about 200,000 cubic yards of dirt will go to make room for a new onramp to the freeway.

Chippers were turning the trees and other vegetation into chips.

The actual work of moving all that dirt and rock is expected to begin on Monday, using excavators, dumps trucks and finally a conveyor system to move the dirt. This work will be done during the day.

The final destination for the dirt is the newly cleared hillside just below Cedar Avenue South on Renton Hill. The dirt will fill even with Cedar Avenue and extend out about 125 feet.

The clearing above I-405 near Renton City Hall is the most visible sign that the Stage 2 project to add lanes to I-405, replace the bridge at Benson Road and a new half-diamond interchange at Talbot Road is well under way.

Designing and constructing the project is I-405 Corridor Design-Builders, a partnership of CH2MHill and Gary Merlino Construction.

Total contract cost is about $83.6 million, although about $1 million represents the land that Gary Merlino will acquire where the fill dirt is going. How that land is developed is up to the company and not the other project partners, including the Washington state Department of Transportation.

As part of a later project, the state will build a three-tiered wall between the fill area and the freeway.

Without that wall, more land and perhaps more buildings would have had to be acquired for right of way, according to Chad Brown, the transportation department Stage 2 project engineer.

Even before this obvious work, the contractor has been working at the extensive site. There have been environmental and geotechnical assessments, a census of wildlife on the hillside and the acquisition of additional right of way, including at the Berkshire Apartments.

All the work on Stage 2 and the already under way Stage 1 is being directed from a “war room” filled with project maps and engineers working on the project design. The headquarters is on Raymond Avenue Southwest, right next to I-405.

Now, crews are keeping an eye on the calendar and the weather forecast.

Also this week, crews excavated the area around a city dump, long out of use along the freeway. Some workers wore protective gear because of the presence of toxic material, including lead.

Part of the initial assessment involved looking at old maps showing abandoned coal mines, which could pose a potential risk.

No “void” has been found, but if one is, “We would have to design around it,” said Brown.

The excavation for the northbound onramp from Talbot Road to I-405 is expected to take up to three months, or just before the rainy season starts.

The contractors have in place measures to control runoff at the site. Those measures include ponds, silt fence, a rocked-in dam and logs of hay.

Workers also will install permanent landscaping during the excavation, according to Alan Brown, project manager for the I-405 Corridor Design-Builders.

In the current hot weather, water trucks are routinely wetting down the work area to control dust.

Go here for updates on the Stage 2 I-405 project through downtown Renton.

THE NOISE HOTLINE

To report a noise concern or to comment, call the project 24-hour noise hotline number at 425-496-2010.