SGER: Characterization of the Precambrian Aquifer at the Homestake DUSEL

SGER：Homestake DUSEL项目总结的前寒武纪含水层的表征目前，南达科他州黑山的Homestake DUSEL存在一个前所未有的机会之窗，用于地下水文研究。 该地点的岩石主要由断裂的前寒武纪变质沉积物组成，并形成了一个区域地下水系统，该系统具有很大程度上未知和不确定的水文特性。 如果不在不久的将来加以利用，这一独特的机会将会丧失。 前Homestake金矿从1876年到2001年持续运营。 金矿存款中的采矿工作沿着沿着4英里的俯冲，穿过1.7 x 1.9 x 3.1英里的地壳，漂移了320英里。 在前寒武纪，该岩系多次褶皱，并向东南倾斜。 Laramide构造作用将黑山提升到目前的构造，并伴随脆性断裂，很可能造成目前在矿山中观察到的断裂。 在矿山运营期间，从前寒武纪含水层连续抽取地下水，2003年矿山关闭后，水泵被关闭。 关闭后的洪水导致水位上升超过3000英尺，目前水位在4850英尺和5000英尺之间。 目前的计划是在2007年12月中旬启动水泵，将水位降低到5300英尺的水平。 前寒武纪含水层的水文特性相对未知。 截流前的研究表明，目前750加仑/分钟的流入流量中约有2/3来自于通过裂隙含水层岩石的水流。 根据流入速度和矿井开口的体积，估计整体渗透率约为10-6至10-7厘米/秒。 本建议书中描述的研究旨在测量矿井中因脱水而下降的水位，并确定前寒武纪含水层的水文特性。 压力传感器将被降低到水柱在6号轴，无论是3号轴延伸到5000英尺。水平或服务轴延伸到6800英尺的水平（服务轴可能无法访问），4号轴延伸到7400英尺。水平，和5号进气轴，延伸到6200英尺。水平 当泵送进行时，传感器将根据需要降低到下降的水柱中。 准确的传感器放置将取决于访问情况，并将与SDSTA合作确定。将使用各种模型对水位数据进行分析，并测试水力传导率测定的适当性，包括裂缝流动和其他因素的修改。 还将使用为流入隧道而设计的模型。 结果，反过来，可以提供新的信息，水文流体流动的地壳体积内的水文和在确定当地前寒武纪含水层的水文性质。在地下空间的小气候条件（温度，湿度，压力和湿球温度）将同时测量与水减少数据。 地下气象站将位于400，1200，2400，3600和4850英尺。水平（或最接近的水平）。 每层将设置两个测站，一个靠近竖井，另一个位于漂移区1000英尺处。 随着矿井水位降低，地表流入被截断，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，将发生进一步的变化。 这些气候变化将是重要的各种实验，作为矿山准备长期的科学和工程计划。 这些早期监测工作将提供关于研究设施初始状况的宝贵信息，同时有助于建立长期监测工作。所有收集到的水文和小气候数据将放在Homestake或SDSM T的网络服务器上，并提供给所有感兴趣的各方。

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.