SR3 Allyn Curves: Washington DOT Contract No. 4315

This is a DOT project to construct a four-lane highway section approximately one mile long to bypass an old section of highway that has been slumping for many years.

General Information

Location -- Allyn, WA
Applicator -- Terra Dynamics
Prim -- WA-DOT
Specifier -- WA-DOT
Owner -- WA-DOT

Case History

The project is about ten miles east of Bremerton, WA and is

oriented east to west. Cuts made in the hillside approach 100 feet in length and vary from 1:1 to 4:1 in slope. Soil type is sand and gravel originating from glacial outwash and sets on a very heavy impermeable clay which shows up at or near road grade.

The sand and gravel veins in the read cuts once supported underground water flow. Once the fall rains hit and the soil reached field capacity the water began lateral movement in the veins. The DOT had put in some rock channeling where previous flow

was apparent but other areas charged up and mass soil slump failures occurred on about 10% of the project. The DOT had these areas covered with plastic.

Soil Guard® application started September 1 and continued for about ten days to cover the seven-acre project. Terra Dynamics did the job. At times they had two crews working to try to get ahead of the paving crew which impacted their efficiency. They were also interrupted by light rains the first week and finished just prior to a mild rainstorm.

The following four weeks of dry weather helped the Soil Guard® set up before the heavy rains came.

Total precipitation from September to December 27 was 39.48 inches with 5.24 inches falling November 30 and 10.08 inches from December 15 through 20. These are the events that has caused the aforementioned damage. The remainder of the project which was protected by Soil Guard® held together great as seen on the photos above. The road cuts are not stabilized with lush green vegetation.