A New Method for Identification of Preferential Flow Paths at Sites of Groundwater Contamination

9903103管家渗透系数的空间分布对污染物在地下的运动起着重要的控制作用。为了量化渗透系数的空间变化对污染物运移的影响，已经发展了许多理论，通过使用随机过程或分形表示来模拟渗透系数的变化。这一点变得越来越明显；然而，在由复杂的岩性组成的单元中，对一个地点的电导率变化的模拟可能会有很大的局限性。显然，需要对更大范围内特定地点的水力传导性分布进行量化，以可靠地预测污染物在这种系统中的运动。特别是，对作为优先流动路径的高水力传导性横向毗连区的了解往往是至关重要的。然而，事实证明，此类区域的实地识别很困难。常规现场技术提供高度平均的信息或仅限于测试井附近的信息。该研究将为井间导水率的空间估算提供一种新的现场方法。虽然是为估计饱和地层中水力传导性变化的一般任务而开发的，但这对于识别优先流动路径是有效的。这种方法包括三个基本要素：1)最近提出的水力层析成像方法，2)用于多水平采样井的油管压降测量的低成本压力传感器，以及3)用于地层控制的地球物理测量数据。水力层析成像有可能产生比以前更详细的井间水力传导性分布的图像。有关抽水引起的扬程变化的垂直变化的详细信息将从低成本的压力传感器中获得。将通过使用跨孔探地雷达测量来限制反演过程来解决不唯一性问题。这项研究的主要目的是对这一前景看好的新方法进行彻底的理论和实地评估。将这些特征纳入场地模型应能极大地提高模型预测的质量，从而导致更可靠的风险评估和为场地定性和补救活动更有效地分配资源。对地下水力传导性变化的描述将具有以前不可能实现的详细程度。此外，这些信息应该有助于更好地将水力传导性的变化与其地质来源联系起来，从而促进将地质信息纳入水文地质调查。为了量化渗透系数的空间变化对污染物运移的影响，已经发展了许多理论，通过使用随机过程或分形表示来模拟渗透系数的变化。这一点变得越来越明显；然而，在由复杂的岩性组成的单元中，对一个地点的电导率变化的模拟可能会有很大的局限性。显然，需要对更大范围内特定地点的水力传导性分布进行量化，以可靠地预测污染物在这种系统中的运动。特别是，对作为优先流动路径的高水力传导性横向毗连区的了解往往是至关重要的。然而，事实证明，此类区域的实地识别很困难。常规现场技术提供高度平均的信息或仅限于测试井附近的信息。该研究将为井间导水率的空间估算提供一种新的现场方法。虽然是为估计饱和地层中水力传导性变化的一般任务而开发的，但这对于识别优先流动路径是有效的。这种方法包括三个基本要素：1)最近提出的水力层析成像方法，2)用于多水平采样井的油管压降测量的低成本压力传感器，以及3)用于地层控制的地球物理测量数据。水力层析成像有可能产生比以前更详细的井间水力传导性分布的图像。有关抽水引起的扬程变化的垂直变化的详细信息将从低成本的压力传感器中获得。将通过使用跨孔探地雷达测量来限制反演过程来解决不唯一性问题。这项研究的主要目的是对这一前景看好的新方法进行彻底的理论和实地评估。将这些特征纳入场地模型应能极大地提高模型预测的质量，从而导致更可靠的风险评估和为场地定性和补救活动更有效地分配资源。对地下水力传导性变化的描述将具有以前不可能实现的详细程度。此外，这些信息应有助于更好地将水力传导性变化与其地质来源联系起来，从而促进将地质信息纳入水文地质调查。

9903103ButlerThe spatial distribution of hydraulic conductivity is a significant control on the movement of contaminants in the subsurface. A number of theories have been developed to quantify the influence of spatial variations of hydraulic conductivity on contaminant transport by using stochastic processes or fractal representations to model the conductivity variations. It is becoming increasingly apparent; however, that the modeling of the conductivity variations at a site be inadequate may have significant limitations in units composed of a complex mixture of lithologies. Clearly site-specific hydraulic conductivity distribution at a larger scale need to be quantified to reliably predicts contaminant movement in such systems. In particular, knowledge on laterally contiguous zones of high hydraulic conductivity, which serve as preferential flow paths, is often critical. The field identification of such zones, however, has proven difficult. Conventional field techniques provide information of a highly averaged nature or restricted to the vicinity of the test well. This research would develop a new field method for the estimation of spatial in hydraulic conductivity between wells. Although developed for the general task of estimation of hydraulic conductivity variations in saturated formations and this effective for the identify of preferential flow paths. This methodology involves three primary elements: 1) a recently proposed method for hydraulic tomography, 2) low-cost pressure sensors for drawdown measurements in the tubing used in multilevel sampling wells, and 3) geophysical survey data for stratigraphic control. Hydraulic tomography has the potential to produce images of the hydraulic conductivity distribution between wells at most detail than previously possible. Detailed information about vertical variations in pumping-induced head changes would be at obtained from the low-cost pressure sensors. Nonuniqueness would be addressed by using cross-hole ground-penetrating radar surveys to constrain the inversion process. The primary purpose of the research is a thorough theoretical and field assessment of this promising new methodology. The incorporation of such features into a site model should dramatically improve the quality of model predictions, thus leading to more reliable risk assessments and a more efficient allocation of resources for site characterization and remediation activities. The descriptions of hydraulic conductivity variations in the subsurface would have a level of detail that has not previously been possible. In addition, the information should help better relate hydraulic conductivity variations to their geologic origins and thus facilitate incorporation of geologic information into hydrogeologic investigations.9903103ButlerThe spatial distribution of hydraulic conductivity is a significant control on the movement of contaminants in the subsurface. A number of theories have been developed to quantify the influence of spatial variations of hydraulic conductivity on contaminant transport by using stochastic processes or fractal representations to model the conductivity variations. It is becoming increasingly apparent; however, that the modeling of the conductivity variations at a site be inadequate may have significant limitations in units composed of a complex mixture of lithologies. Clearly site-specific hydraulic conductivity distribution at a larger scale need to be quantified to reliably predicts contaminant movement in such systems. In particular, knowledge on laterally contiguous zones of high hydraulic conductivity, which serve as preferential flow paths, is often critical. The field identification of such zones, however, has proven difficult. Conventional field techniques provide information of a highly averaged nature or restricted to the vicinity of the test well. This research would develop a new field method for the estimation of spatial in hydraulic conductivity between wells. Although developed for the general task of estimation of hydraulic conductivity variations in saturated formations and this effective for the identify of preferential flow paths. This methodology involves three primary elements: 1) a recently proposed method for hydraulic tomography, 2) low-cost pressure sensors for drawdown measurements in the tubing used in multilevel sampling wells, and 3) geophysical survey data for stratigraphic control. Hydraulic tomography has the potential to produce images of the hydraulic conductivity distribution between wells at most detail than previously possible. Detailed information about vertical variations in pumping-induced head changes would be at obtained from the low-cost pressure sensors. Nonuniqueness would be addressed by using cross-hole ground-penetrating radar surveys to constrain the inversion process. The primary purpose of the research is a thorough theoretical and field assessment of this promising new methodology. The incorporation of such features into a site model should dramatically improve the quality of model predictions, thus leading to more reliable risk assessments and a more efficient allocation of resources for site characterization and remediation activities. The descriptions of hydraulic conductivity variations in the subsurface would have a level of detail that has not previously been possible. In addition, the information should help better relate hydraulic conductivity variations to their geologic origins and thus facilitate incorporation of geologic information into hydrogeologic investigations.