Mullan Road Sewer Project
Missoula, Montana
Project included construction of a corridor sewer main with
interceptors/collectors, force mains, and 3 lift stations. The
investigation was performed using Orion Engineering drill. Subsurface
conditions consisted of alluvial deposits and terraces of lacustrine
deposits consisting of plastic silts and clays. Groundwater levels
were variable. Performed limited research regarding potentiometric
groundwater surface mapping. The geotechnical report included
subsurface conditions along the main line, anticipated groundwater
levels during construction, earthwork and trenching guidelines,
constructed slopes, and foundation recommendations for the pump
stations.
Pipeline River-Crossing Investigation
Thompson Falls and East Missoula, Montana
Project included feasibility evaluation of replacing two overhead
pipeline river crossings with underground crossings. Currently, the
pipeline crosses the river at these locations via an overhead
pier-supported system that has been in-place for over 30-years. The
underground system is to be installed using directional drilling
technology. A secondary purpose of our investigation was to evaluate
the capability of existing pier foundations to withstand current
seismic design standards. Due to the poorly graded cobble/gravel
conditions, traditional rotary auger drilling and wireline coring were
not considered effective methods of advancing boring holes. Utilized a
tri-cone HQ casing advancement system and percussion air rotary
methods to advance holes to required depths. The maximum boring depth
was 100-feet.
