This study applies innovative methods to characterize and quantify the magnitude of groundwater flow in a fractured and variably cemented sandstone aquifer to inform an in-situ remediation strategy for trichloroethene (TCE) contamination. A modified active-distributed temperature sensing (A-DTS) approach in which fiber optic cables were permanently grouted in the borehole was used to quantify groundwater flow rates. Two additional tracer tests were conducted: 1) fluorescein tracer injection followed by rock coring and sampling for visual mapping and porewater analysis, and 2) deployment of passive flux meters in conventional monitoring wells to evaluate groundwater velocity and mass flux distributions. Forced gradient injection of fluorescein tracer suggests a dual porosity flow system wherein higher rates of groundwater flow occur within discrete features including highly permeable bedding planes and fractures, with slower flow occurring within the rock matrix. Tracer was observed and detected in the unfractured matrix porewater >1.5 m away from the injection well. Beyond this distance, >6 m radially away from the injection hole, tracer was primarily detected within and adjacent to high transmissivity fractures serving as preferential flow paths. The Darcy flux calculated using active distributed temperature sensing (A-DTS) shows depth-discrete values ranging from 7 to 60 cm/day, with average and median values of 23 and 17 cm/day, respectively. Passive Flux Meters (PFMs) deployed in three conventional monitoring wells with slotted screens and sand filter packs showed groundwater flux values ranging from 2 to 11 cm/day, with an overall average of 4 cm/day and are likely biased low due to spreading in the sand pack. The study results were used to inform an in-situ remediation system design including the proposed injection well spacing and the amendment delivery approach. In addition, the results were used to build confidence in the viability of delivering an oxidant to the rock matrix via advective processes. This is important because 1) the matrix is where the majority of the TCE mass occurs, and 2) it provides insights on processes that directly affect remedial performance expectations given advective delivery to preferential pathways and the matrix overcomes diffusion only conditions.

本研究采用创新方法来表征和量化裂缝性和可变胶结砂岩含水层中地下水流量的大小，为三氯乙烯 (TCE) 污染的原位修复策略提供信息。一种改进的有源分布式温度传感 (A-DTS) 方法，其中光纤电缆在钻孔中永久灌浆，用于量化地下水流量。还进行了两项额外的示踪剂测试：1) 荧光示踪剂注入，随后进行岩石取芯和取样，用于可视化绘图和孔隙水分析，以及 2) 在常规监测井中部署被动通量计以评估地下水速度和质量通量分布。荧光素示踪剂的强制梯度注入表明了双孔隙度流动系统，其中较高的地下水流动速率发生在离散特征内，包括高渗透性的层理平面和裂缝，而在岩石基质内发生较慢的流动。在距注入井>1.5 m 的未压裂基质孔隙水中观察并检测到示踪剂。超过此距离，距注入孔径向 > 6 m，主要在作为优先流动路径的高透射率裂缝内和附近检测到示踪剂。使用主动分布式温度传感 (A-DTS) 计算的达西通量显示的深度离散值范围为 7 至 60 厘米/天，平均值和中值分别为 23 和 17 厘米/天。在三个带有开槽筛网和砂滤器组件的常规监测井中部署的无源通量计 (PFM) 显示地下水通量值范围为 2 至 11 厘米/天，总体平均值为 4 厘米/天，并且可能由于扩散而偏低沙包。研究结果用于为原位修复系统设计提供信息，包括建议的注入井间距和修正输送方法。此外，这些结果用于建立对通过平流过程将氧化剂输送到岩石基质的可行性的信心。这很重要，因为 1) 基质是大部分 TCE 质量发生的地方，2) 它提供了对直接影响补救性能预期的过程的见解，因为对流输送到优先路径，并且基质克服了仅扩散条件。