WY FLAP SHE 26(2) Red Grade Road - Geotechnical Drilling

The project consists of geotechnical drilling for 7.6 miles of the gravel Red Grade Road between Mileposts 3.3 and 10.9 in Sheridan County, Wyoming (see attached County map). Milepost 0 is at the intersection of Red Grade Road with Wyoming State Highway 335 and Lower Hideaway Lane (6 miles southwest of the town of Big Horn, WY).

The drilling to consist of sixteen shallow borings up to 5-foot depth (or until refusal) plus one deep boring up to 30-foot depth (or until refusal). The drilling to consist of hollow stem auger (HSA) drilling using a truck mounted drill rig able to advance to 30-foot depth. The soils beneath the road are believed to consist of silty, clayey sand with gravel and cobbles. Borings may encounter boulders and bedrock. A two-man drill crew is anticipated. Shallow borings are intended to penetrate through the existing structural section and into the underlying material for the purpose of gathering bulk subgrade samples (in 5 gallon buckets with 50-70 pounds of material each). It is estimated that these borings will be on 0.50 mile increments or as marked. The deep boring is intended to collect split barrel samples (in 1 gallon ziplock bags) and to measure the SPT resistance of the soil at increments of 5’ depth. Drill cuttings can be dispersed at the site. Borings to be backfilled with excess cuttings for depths less than 5 feet and imported pea gravel or bentonite chips for depths greater than 5 feet and compacted. The boring to be topped with at least 6 inches of compacted crushed aggregate road base. FHWA personnel to log the samples and transport the sample buckets to a shipping location. FHWA to

provide the 5-gallon buckets with lids and 1-gallon ziplock bags.