CPT Explorations on the Coweeman LeveeCornforth Consultants was retained by the Portland District, US Army Corps of Engineers to perform geotechnical field explorations and laboratory investigations and prepare a Geotechnical Data Report for five Cowlitz River levees. The investigations were conducted to determine existing levee foundation conditions and embankment properties for future stability analyses on the Castle Rock, Longview, Coweeman, Kelso, and the Lexington Levees.
The work consisted of drilling and sampling, Standard Penetration Tests (SPT), Cone Penetrometer Tests (CPT), laboratory testing to develop material properties, and falling head tests in the field to determine in-situ permeability. The program consisted of 14 borings and 17 CPT probes. SPT’s and falling head tests were conducted in each of the hollow-stem auger boreholes. The CPT data was processed and interpreted to establish correlations with soil behavior classification, angle of internal friction, and equivalent SPT, N60 values. Friction angle strengths were also obtained by correlating blowcount data obtained from SPT tests.