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Battle Mountain Resources—San Luis SL-SOP-Groundwater Well Decommissioning <br /> STANDARD OPERATING PROCEDURES 11 REVISION: 0-May 6,2019 <br /> • A hollow-stem auger with outward facing carbide cutting teeth having a <br /> diameter two to four inches larger than the casing. <br /> Prior to over-drilling, the bottom of the well should be perforated or cut away, and <br /> the casing filled with grout as with casing removal by pulling. <br /> In all cases above, over-drilling should advance beyond the original bore depth by <br /> a distance of half a foot to ensure complete removal of the construction materials. <br /> Oversight attention should be focused on the drill cuttings, looking for fragments of <br /> well materials. Absence of these indicators is a sign that the drill has wandered off <br /> the well. If wandering is suspected, having previously filled the well with grout, the <br /> remaining portion which cannot be over-drilled can be considered grouted in-place. <br /> When the over-drilling is complete, grout should be tremied within the annular <br /> space between the augers and well casings. The grout level in the borehole should <br /> be maintained as the drilling equipment and well materials are sequentially <br /> removed. As with all the other methods, the upper five feet of borehole should be <br /> restored according to the procedures in Section 9. <br /> 5. SELECTION PROCESS AND IMPLEMENTATION <br /> The decommissioning procedure selection flow chart, Attachment 13-2, is to be used to <br /> select decommissioning methods. The selection process first identifies the basic <br /> monitoring well type. There are only two types of monitoring wells described in this <br /> guidance, overburden wells and bedrock wells. Bedrock wells typically have an <br /> overburden portion which in the selection process is to be treated as an overburden <br /> well. Techniques are specified for wells based upon their type and the other physical <br /> conditions present. Decommissioning techniques called for by the selection process <br /> have their practical limits; construction details dictate when a well stem can be pulled <br /> without breaking and when it cannot be pulled. The project manager has the discretion <br /> to deviate from the flow chart, (Attachment 13-2), based on site conditions, budgetary <br /> concerns and professional judgment. The remainder of this section will discuss types of <br /> monitoring wells in various settings along with recommended decommissioning <br /> techniques. <br /> 5.1. Bedrock Wells <br /> Referring to Attachment 13-2 and Section 4.1, if the well extends into bedrock, the <br /> rock hole portion of the well is to be grouted in-place to the top of the rock. The grout <br /> mix, however, may vary according to the conditions. A thicker grout may be required <br /> to fill voids and a thinner grout may be necessary to penetrate well screen and sand <br /> pack. Refer to the grout mixture specifications given in Section 8.1 and 8.2. <br /> Prior to grouting, the depth of the well will be measured to determine if any silt or <br /> debris has plugged the well. If plugging has occurred, all reasonable attempts to <br /> clear it should be made before grouting. The borehole will then be tremie grouted <br /> according to Section 8.4 from the bottom of the well to the top of bedrock to ensure <br /> a continuous grout column. <br /> SL-SOP Well Decommissioning EA, Inc. <br /> Battle Mountain Resources, Inc. Page 9 of 21 Ma 6,2019 <br />