Holocene Tackles Subsurface Investigation
September 1, 2008
Holocene Drilling Inc., Tacoma, Wash., recently completed a boring project for Tacoma Rail’s Mountain Division at a crossing on the Nisqually River near Mt. Rainier National Park.
Tacoma Rail selected Exceltech in Lacey, Wash., to complete the structural design reports through a competitive bid process. Exceltech then teamed with GeoEngineers to perform the geotechnical engineering. GeoEngineers selected Holocene Drilling as the drilling contractor for the project. The remote location and difficult access to the boring locations required the team to develop an innovative solution to access the rail bridge embankments that failed due to heavy flooding. The team turned to Holocene Drilling for a solution to the problem.
Working with Tacoma Rail’s Mountain Division, Holocene Drilling devised a plan to load its CME-850 directly onto a flat rail car and transport it to the boring locations on each side of the river. By pre-fabricating a drill pad, and having the abutment in place so the rail car could couple itself to it, the CME-850 then was able to access the boring locations near each of the failed bridge embankments. Once in place, Holocene’s driller advanced a hollow-stem auger into heavily consolidated gravels and cobbles in glacial till formations, using an automatic hammer to obtain blow counts and samples. This allowed the engineering team to gather valuable information about the formations near each embankment, which will be used in the new design.
Tacoma Rail assumed operations for the City of Tacoma railroad’s Mountain Division to provide freight rail service along 132 miles of track. It’s called “Mountain” Division because the rail grade is considered mountain grade. The 3.3 percent grade means the rail gains 3.3 feet in altitude for every 100 feet in distance.
Recent rehabilitation projects made possible by federal grants facilitated rail and tie replacement. The Mountain Division interconnects and interchanges with the two transcontinental railroads – the Union Pacific Railroad and the Burlington Northern and Santa Fe Railway – in Tacoma at the north end of the line, and at Centralia/Chehalis in the south. The Mountain Division also is connected for interchange with the Puget Sound and Pacific Railroad that runs west to the Pacific Ocean.
Holocene Drilling Inc. is owned and operated by Jay Graham and Clay Griffith, and was established in 1996. It currently operates six drill rigs and a dewatering jet, performing geotechnical and environmental subsurface investigations using hollow-stem auger, mud rotary and rock coring for engineering clients and contractors throughout the state of Washington.