SGER: Characterization of the Precambrian Aquifer at the Homestake DUSEL

SGER：Homestake DUSEL项目总结前寒武纪含水层的特征目前在南达科他州Black Hills的Homestake Dusel地下水文研究存在一个前所未有的机会之窗。该地点的岩石主要由破碎的前寒武纪变沉积组成，并形成了一个区域地下水系统，具有很大程度上未知和未定义的水文特性。如果在不久的将来不加以利用，这一独特的机会将会丧失。前身为Homestake金矿于1876年至2001年连续运营。金矿的采矿工作沿着霍姆斯塔克地层，沿着4英里的倾角，穿透了1.7x1.9x3.1英里的地壳，漂移了320英里。在前寒武纪，岩层被多次褶皱并向东南倾斜。拉莱姆构造作用将黑山抬升到目前的形态，并伴随着脆性断裂，最有可能造成目前在矿山中观察到的裂缝。在矿井运行期间，地下水从前寒武纪含水层连续抽出，并在2003年矿井关闭后关闭了水泵。关闭后的洪水已导致超过3000英尺的水位上升，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英尺的水位。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2/3来自通过裂隙含水层岩石的流动。根据流入率和矿井开采量，估计体积渗透率约为10-6至10-7厘米/秒。这项建议中所述的研究试图测量矿井在脱水时下降的水位，并确定前寒武纪含水层的水文性质。压力传感器将被放入6号竖井的水柱中，或者延伸至5000英尺的3号竖井。水平井或延伸至6800英尺水平面的维修井(维修井可能无法接近)，延伸至7400英尺的4号井。以及延伸至6200英尺的5号进气井。水平。随着抽水的进行，传感器将根据需要被放入下降的水柱中。传感器的准确位置将取决于访问情况，并将在SDSTA的合作下确定。将使用各种模型分析水位数据，并测试水力传导性测定的适当性，包括对裂缝流动和其他因素的修正。还将使用为流入隧道而设计的模型。反过来，这些结果可以提供关于地壳内流体流动的水文学的新信息，并在确定当地前寒武纪含水层的水文性质方面提供新的信息。地下空间的小气候条件(温度、湿度、压力和湿球温度)将与降水数据同时测量。地下气象站将设在400、1200、2400、3600和4850英尺的地方。级别(或最近的可访问级别)。每一层将放置两个站点，一个靠近竖井，一个在漂移中，最高可达1000英尺。随着矿井水位降低，地表来水被截流，地下气候开始发生变化。随着矿井从目前的非通风状态进入完全通风状态，还将发生进一步的变化。随着该矿为长期科学和工程计划做准备，这些气候变化将对各种实验具有重要意义。这些早期监测工作将提供有关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。所有收集到的与水文和小气候有关的数据将放在Homestake或SDSM&amp；T的网络服务器上，供所有感兴趣的各方使用。

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.