SR-18 Auburn/Black Diamond Road: DOT Contract No. 4354

This is a DOT project to widen SR-18 to four lanes from Auburn to I-90, approximately 25 miles.

General Information

Location -- Auburn, WA
Applicator -- Terra Dynamics
Prim -- WA-DOT
Specifier -- WA-DOT
Owner -- WA-DOT
Case History

The first stage is a two-mile stretch from Green River to the first major interchange. This section will require about 20 acres of Soil Guard® for erosion control. The major construction consists

of both cuts and fills to widen the road.

The project is oriented generally east-west. Cuts near the Green River bridge probably exceed 200 feet in length and vary from 1:1 to 3:1 in slope. Soil is primarily a sandy loam with gravel deposits running horizontally at various levels. Some heavy clays are apparent near road grade level.

Soil Guard® was first applied mid-September by Terra Dynamics. The application was done in stages as the large earth moving equipment would cut the hill down. When the second

cut was made some application could be done east of the main hill including a large fill area. By the end of October the rainstorms had started and application of Soil Guard® halted. By this time the first section was greening up nicely.

Just below the first cut and application a gravel vein had charged up with water and mud from heavy rains. By mid-November this perched water table "burped" the mud out through the gravel causing the mud to flow down the hill over the second application of Soil Guard®.

The Soil Guard® maintained integrity throughout this event and is now supporting a good growth of vegetation, including through the mud flow. There are a few small slumps and rills caused by saturated soils on the project but generally speaking the Soil Guard® has performed exceptionally well. Chief inspector Linda Blair is very pleased with Soil Guard® performance.

The erosion control portion of the project was winterized by straw mulching and will be continued in the spring of 1995.