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between the two logging dates, and the GR logging tool's datum or zero point may be
<br />slightly different. The casing collar logs overlay each other fairly well, with minor
<br />differences noted in the perforated casing zone 1,877-1,917 ft., which was perforated
<br />after the baseline log was run.
<br />In August, 2015, NS was unable to install a groundwater sampling pump to an
<br />appropriate sampling depth in the DS -4. Jet West Geophysical Services, LLC, out of
<br />Farmington, New Mexico, was contacted and scheduled to run a video log survey and
<br />visual casing inspection of the well. At and below a depth of 1,763 ft. bgs the casing was
<br />noted to be parted in four separate places. All four partings were full circumferential
<br />breaches in the casing at the collar locations. The first parting appeared to be
<br />approximately 0.1 ft wide with cement grout and some formation visible. A second
<br />parting was seen at approximately 1,783.6 ft, with generally intact annular cement visible
<br />through the parted casing. At this depth the casing was deviated with a slight physical
<br />deformation in the casing visible at approximately 1,797 ft. A third parting was observed
<br />at approximately 1,804 ft. Annular cement was visible through this parting and appeared
<br />to be generally intact. A fourth parting was noted at 1,824 to 1,825.5 ft, once again,
<br />cement was clearly visible and appeared mostly intact on borehole walls. At 1,825.5 ft,
<br />the casing was slightly off center, and the camera would not advance beyond this depth.
<br />It was deemed prudent to run a GR/CCL log to evaluate the well because the DS -4 well
<br />location is proximal to the casing shoes of the NS 1OH-1 and 101-1-11 wells. On August
<br />25, 2015, DLD Pipe Recovery out of Fruita, CO, ran a GR/CCL log to approximately 1,916
<br />ft, where they could go no further. The three GR/CCL logs (WFD July 12, 2009, RMWS
<br />March 15, 2011, and DLD August 25, 2015) were plotted side by side and correlated. The
<br />DLD CCL log was consistent with the video log, showing that the casing collars had shifted
<br />down below a depth of 1,763 ft GL. The lowest casing collar logged at approximately
<br />1,890 ft, had dropped approximately 4-5 ft. from the July 2009 CCL logs which shows the
<br />collar at 1,885.5 ft. The gamma ray trace from the August 25, 2015 log correlates to the
<br />previous two GR logs until approximately 1,850 ft GL. The shape of the curve is
<br />consistent with the shape of the previous two curves. A correlation point 67 ft above the
<br />DS (at 1,922 ft) at 1,858 feet on the 8/25/15 log indicates a three foot downward shift
<br />compared to the 7/12/2009 log. This may indicate a localized and slight formation shift
<br />downward and is believed to result from the proximal nature of location of the vertical
<br />monitor well to the horizontal mining interval. This localized subsurface subsidence may
<br />migrate a short distance up vertical monitor well bores which are proximal to horizontal
<br />mining intervals and may explain the casing partings with apparent intact cement on the
<br />borehole walls. The formation may have shifted below a depth of 1,850 ft GL, pulling the
<br />casing with it. The casing was pulled down independent of the formation up to a depth
<br />of 1,763 ft GL, the location of the first parting. The annular cement had a stronger bond
<br />with the borehole walls allowing the casing to slide through the cement, leaving behind
<br />the cement sheath on the borehole walls as seen in the video log.
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