SGER: Characterization of the Precambrian Aquifer at the Homestake DUSEL

目前，南达科他州布莱克山Homestake DUSEL地下水文研究出现了前所未有的机遇之窗。该遗址的岩石主要由断裂的前寒武纪变质沉积物组成，形成了一个区域地下水系统，其水文性质在很大程度上是未知的。如果在不久的将来不加以利用，这个独特的机会将会失去。前霍姆斯特克金矿从1876年到2001年连续经营。金矿的开采跟随Homestake地层，沿着4英里的纵深，穿过1.7 x 1.9 x 3.1英里的地壳，有320英里的漂移。前寒武纪岩石层序多次褶皱，向东南方向倾斜。拉拉米构造运动使布莱克山上升到现在的形状，并伴有脆性断裂，很可能造成了目前在该矿中观察到的裂缝。在矿井运行期间，从前寒武纪含水层连续抽取地下水，2003年矿井关闭后，水泵关闭。关闭后的洪水导致水位上涨超过3000英尺，目前水位在4850英尺到5000英尺之间。目前的计划是在2007年12月中旬启动水泵，将水位降至5300英尺的高度。前寒武纪含水层的水文特性相对未知。关闭前的研究表明，目前750加仑/分钟的流入速率中约有三分之二来自裂缝性含水层。根据流入速率和矿井开口的体积，估计总体渗透率约为10-6至10-7厘米/秒。本提案中描述的研究旨在测量矿井脱水时下降的水位，并确定前寒武纪含水层的水文特性。压力传感器将被放入6号井井的水柱中，或者是延伸至5000英尺深的3号井井。或延伸至6800英尺高度的维修竖井（维修竖井可能无法进入）、延伸至7400英尺高度的4号竖井。5号进气井延伸至6200英尺。的水平。随着泵送的进行，传感器将根据需要降低到下降的水柱中。准确的传感器位置将取决于访问情况，并将在SDSTA的合作下确定。对水位数据的分析将使用各种模型，并测试水力导电性测定的适用性，包括对裂缝流量和其他因素的修改。为流入隧道而设计的模型也将被使用。结果，反过来，可以提供新的信息，在地壳内的流体流动的水文学和确定当地的前寒武纪含水层的水文性质。地下空间的小气候条件（温度、湿度、压力和湿球温度）将与减水量数据同时测量。地下气象站将分别位于400、1200、2400、3600和4850英尺。关卡（或最近的可访问关卡）。每一层将设置两个监测站，一个靠近竖井，另一个位于1000英尺深的漂流区。由于矿井水位下降，地表涌流被截流，地下气候将开始发生变化。随着矿井从目前的不通风状态进入完全通风状态，还会发生进一步的变化。由于该矿是为长期的科学和工程项目做准备，这些气候变化对各种实验都很重要。这些早期监测工作将提供有关研究设施初始条件的宝贵信息，同时有助于建立长期监测工作。所有收集到的有关水文和小气候的数据将放在Homestake或sdsm&； T的网络服务器上，并向所有感兴趣的各方开放。

SGER: Characterization of the Precambrian Aquifer at the Homestake DUSELProject SummaryAn unprecedented window of opportunity currently exists for subsurface hydrological studies at the Homestake DUSEL in the Black Hills, South Dakota. Rocks at the site consist primarily of fractured Precambrian metasediments and form a regional groundwater system possessing largely unknown and undefined hydrologic properties. If not instrumented in the near future, this unique opportunity will be lost. The former Homestake Gold Mine operated continuously from 1876 to 2001. Mine workings in the gold deposit followed the Homestake formation along 4 miles of plunge, penetrating through a volume of crust 1.7 x 1.9 x 3.1 miles with 320 miles of drift. The rock sequence was folded several times and tilted toward the southeast during the Precambrian. Laramide tectonism raised the Black Hills to their current configuration and was accompanied by brittle fracture, most likely creating the fractures presently observed in the mine. Groundwater was pumped continuously from the Precambrian aquifer during the operation of the mine and pumps were turned off in 2003 after the mine closed. Post-closure flooding has resulted in more than 3000' of water rise and is currently between the 4850-ft level and the 5000-ft level. Current plans are for pumps to be turned on in mid-December 2007 to reduce the water level to the 5300-ft level. Hydrologic properties of the Precambrian aquifer are relatively unknown. Pre-closure research has shown that about 2/3 of the current 750 gal/min inflow rate originate from flow through the fractured aquifer rocks. Bulk permeability has been estimated, based on inflow rates and the volume of mine openings, at about 10-6 to 10-7 cm/sec. The research described in this proposal seeks to measure falling water levels in the mine as it is dewatered and to determine the hydrologic properties of the Precambrian aquifer. Pressure sensors will be lowered into the water column at the No. 6 shaft, either the No. 3 shaft which extends to the 5000-ft. level or the service shaft which extends to the 6800-ft level (service shaft may not be accessible), the No. 4 shaft which extends to the 7400-ft. level, and the No. 5 air intake shaft which extends to the 6200-ft. level. Sensors will be lowered, as required, into the falling water column as the pumping proceeds. Exact sensor placement will depend on access and will be determined with the cooperation of the SDSTA. Analysis of water-level data will be achieved using various models and tested for appropriateness of hydraulic conductivity determinations, including modifications for fracture flow and other factors. Models designed for flow into tunnels will also be used. The results, in turn, can provide new information about the hydrology of fluid flow within a volume of the crust and in determination of hydrologic properties of the local Precambrian aquifer.Microclimatic conditions (temperature, humidity, pressure, and wet bulb temperature) in the underground spaces will be measured concurrently with water reduction data. Meteorological stations underground will be located on the 400, 1200, 2400, 3600, and 4850-ft. levels (or nearest accessible levels). Two stations will be placed on each level, one near the shaft and one up to 1000 feet in the drift. As the water level in the mine is reduced, and the surface inflow is intercepted, subsurface climatic changes will begin to occur. Further changes will occur as the mine goes from its current non-ventilated state into a fully ventilated sate. These climatic changes will be important to various experiments as the mine is prepared for the long-term science and engineering program. These early monitoring efforts will provide valuable information on the initial conditions of the research facility, while helping to establish a long-term monitoring effort. All collected data pertaining to hydrology and microclimate will be placed on a web server, either at Homestake or SDSM&T, and be made available to all interested parties.