Geotechnical Investigation for HDD Pipeline Construction

GES geotechnical borings on Lake Sakakawea, North Dakota
GES barge deployment Lake Sakakawea
GES barge workers during geotechnical investigation

Client Challenge

A national midstream energy company is pursuing the development of pipeline infrastructure to transport oil produced in the Bakken Shale Play. The proposed pipeline route includes a 12,000-foot crossing beneath a large reservoir using horizontal directional drilling (HDD) construction methods. Our client, the HDD contractor, required a comprehensive geotechnical investigation to confirm the subsurface conditions beneath the lake prior to beginning construction later that year.

GES Solution

GES managed the geotechnical exploration activities in the field as well as subsequent laboratory analysis and reporting, including 10 water-based boring locations within the lake. GES mobilized two dedicated field crews to support 24-hour-a-day drilling operations. The approach yielded significant productivity gains while reducing the project schedule by four weeks. The drilling work was scheduled to coincide with the migratory season of the federally-protected Least Tern and Piping Plover known to inhabit the lake.

Geotechnical borings were located at set intervals across the lake and advanced to a prescribed termination of approximately 160 feet below the lake mudline, using fluid rotary methods through a casing. Borings were advanced into weathered rock, with limited soil sampling, to classify soil and for laboratory testing. GES prepared the final report documenting the subsurface conditions for use in overall construction planning efforts.

Client Value

GES’ approach to staffing the drilling operations on the lake resulted in significant time and cost savings benefits for the client, while also avoiding potentially unfavorable weather conditions on the lake in the late fall season. The expedited submittal of GES’ geotechnical inspection report provided the HDD contractor with more time to consider and incorporate findings in the overall construction approach. GES’ implementation of Loss Prevention System (LPS) health and safety training and procedures facilitated an incident-free project within a high-risk environment, underscoring the importance of pre-planning and LPS tools.