AMERICAS | PROJECTS


Right:


PacWave South project’s offshore bore plan with geophysical data along the alignment


geological features. These challenges include marine


sedimentary rock formations, which pose difficulties due to their swelling nature, as well as characterized by reactive and bentonitic properties. Additionally, the presence of basalt formations significantly impacts the drilling rate of penetration, adding another layer of complexity to construction. To overcome this challenge, it was crucial to


understand the composition of the ocean bed and the material that the project team would drill through. In an ideal scenario, a drill rig would be used to


collect samples of the soil and rock below the seafloor during the project’s design, requiring the installation of a platform in the surf zone. This approach was not


feasible due to permitting, as well as the cost and schedule delays required to mobilize the specialized equipment required, which would have taken years to plan and execute. Instead, the team conducted a thorough analysis


of the local geology, studied similar projects in the area, and utilized geophysical data collected on land and from boats. Though this did not provide physical samples to review and test, this effort gave the team an understanding of the seabed composition, revealing the presence of two key substances – basalt and mudstone. Mudstone can be particularly challenging to drill


through. Some mudstones react with fresh water to swell and can close in on the drill bit, locking it in place.


Right:


HDD Drill rig advancing the onshore bore between the State Park and the Utility Connection and Monitoring Facility


22 | Summer 2024


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