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Sonic Drilling Field Standard Operating Procedure SWE-FSOP-302;Revision 0 Ahtna Southwest Environmental Operations Refer to project work plans to confirm equipment required for the specific drilling activity. This may include but is not limited to various field forms, sample containers, incremental sampling devices, and sample homogenizing equipment. 4.0 Procedures Procedures are provided for: • Pre-Field Tasks (Section 4.1) • Mobilization and Setup (Section 4.2) • Drilling Procedures (Section 4.3) • Borehole Abandonment (Section 4.4) • Demobilization/Site Restoration (Section 4.5) Sonic drilling is commonly used where the Project Geologist deems issues around difficult drilling and intact core sample recovery affect the success of the work. Sonic drilling is a method of drilling that employs two opposite-rotating elements (oscillators) in the drill head that act as counterweights working against one another. By adjusting or tuning the oscillations, high- frequency resonance is generated down the tool string to the end of the core barrel (bit), driving the bit downwards. Cuttings are recovered as core samples or displaced outside of the borehole. Cuttings are usually transferred into a polyethylene sample bag or Lexan liner for logging and storage. The core barrel is advanced, and the casing is advanced over the core barrel before retraction.Water may be added when working at greater depths, but it is beneficial to drill dry if the depth to groundwater needs to be determined. A continuous core provides a detailed look at the soil at the depths drilled. This results in a better understanding of the subsurface conditions. Cuttings produced by this method are typically intact as a core sample, allowing for accurate logging. Additional considerations in using sonic drilling techniques include the potential of volatilizing contaminants due to the heat generated by the oscillating bit. 4.1 Pre-Field Tasks Preparation and coordination tasks for sonic drilling generally include the activities described below. 4.1.1 Clearances Before starting any sonic boring, confirm that drilling locations have been appropriately cleared of potential overhead, surface, and subsurface hazards per the project work plans. This should include a utility locating subcontractor to identify subsurface infrastructure and anomalies. The clearance process also includes completing public utility locating service calls (e.g., Dig Alert, USA North 811, etc.) and completing any coordination and permitting procedures with the onsite Department/Directorate of Public Works personnel required by the project contract. Page 6 of 11