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III IIIIIIIIIIIII III !~ ~ ~~ 6~ ~n1~ ~ <br />i <br />' NOV 3 0 1S°0 <br />INTRODUCTION <br />N+in2d Land <br />Wyoming Fuel Company's (WFC) Canadian Strip Mine is located in Jac(issrt`County? Cdlff(3~(TSN, <br />R78W). The mint was projected to utilize a phased open pit mining icchnique with two general areas of <br />production. Pit #1 lies in Section 2 (T8N, R73W) and has been mined out with reclamation activities <br />' completed in 1987. The proposed Pit #2 lies in Section 10 (T8N, R78W} with no development occurring. <br />WFC discontinued all mining operations at the mine site in mid 1982 because of coal marketing difficulties. <br />To comply with Stipulation 1 of the permit issued by CMLRB, an annual report of water resources <br />' monitoring must be submitted. The intent of this report is to comply with this requirement by presenting the <br />data collected to date for groundwater investigations. The following sections contain the materials, methods <br />and results of the groundwater and NPDES monitoring program in the Pit #1 area during the 1990 water year. <br />GROUNDWATER , <br />The Canadian Strip Mine lies in the northeast corner of North Park, a large basin underlain by thick <br />' sequence of sediments. These sediments fill the large synclinal depression between the surrounding mountain <br />ranges. Within this synclinal depression tic numerous smaller structural features. One such feature is the <br />McCallum anticline with the mine site being located on its southern terminus. At this location, the anticline <br />'' is breached such chat the older rocks of the Pierre Formation are exposed in the center of the younger strata <br />of the Coalmont Formation. As a result, this area acts as a groundwater recharge zone for the Coalmont <br />Formation. However, being at a high topographic elevation with no perennial streams, the recharge potential <br />' is limited to snow melt and major precipitation events. <br />Fifteen groundwater monitoring wells were installed within the vicinity of the Canadian Strip Mine <br />(Exhibit C-2) all of which arc completed in the Coalmont Formation. Four wells were initially installed for <br />' monitoring the Pit #1 area. Wells 1 and 1C arc completed below the Sudduth Coal Seam, Well lA is <br />completed in the seam and Well 1B is above the scam. The rationale for locating the wells where they are <br />was to monitor the down dip and down gradient effects on the groundwater system before, during and after <br />!,' mining. <br />In addition to those four wells, ten wells were installed in the proposed Pit #2 area. Wells 4A, SA and <br />' 6A are completed in the underburden below the coal; Wells 46, 5B and 6B are completed in the coal; Wells <br />4C, SC and 6C are completed in the overburden immediately overlying the coal; and Well 2 is located in <br />unconsolidated surface material adjacent to Weir #1. All of these wells (except Well 2) were reclaimed in <br />September 1989, while Well 2 was reclaimed in April 1990. <br />' Well 7 was installed in late 1980. It is located in the reclaimed area of Pit #1 to monitor groundwater <br />beneath the backfill. Additional information and lithology logs for each well have been provided in the <br />' permit document. <br />Water Icvcls in each of the wells have been monitored monthly during 1981 and 1982 and annually from <br />' 1984 through 1989. Water Icvcls were measured with a Soiltcst, Inc. Model DR-762A electric line to the <br />nearest hundredth of a foot from the top of the well casing. Water samples were collected with a hand bailer. <br />Prior to sample collection, a minimum of three columns of water were evacuated to obtain a representative <br />sample. All samples were filtered wish glass fiber filters, preserved and stored in bottles, and analyzed at Core <br />' Laboratories. <br />The physical characteristics of each well are listed in Table 1. Water levels in each of the wells (see <br />' attached Figure and Data Tables) have exhibited a relative increase in water level through 1987 and a slight <br />decrease in water Icvel from 1987 through 1990. These water levels may be affected by the artesian head which <br />exists because of the down dip locations o(the wells. The discontinuation of mining operations has eliminated <br />pumping and dewatcring of Pit # 1 which was anticipated to increase water levels in the down dip Wells 1, lA, <br />' 1B and 1C. The stabilization of water Icvcls and slight decrease over the past three years indicates that no <br /> <br />