Evaluation of the Hydraulic Fence System for Groundwater Remediation near a Stream Using Analytical Method

The protection of groundwater resources against pollution is an important and essential issue. One of the effective methods in the treatment of aquifers is the utilization of the injection-extraction well pair system (hydraulic fence system). In this study, the remediation system of a pair of injection and extraction wells near a stream was analytically analyzed. The potential and stream functions were analyzed together with the capture and release zones of the wells in three configurations. The base flow rate (i.e. the minimum flow rate to initiate the circulation cell between the recharge and pumping wells) was calculated and analyzed in different modes. The critical flow rate (i.e. the allowable maximum flow rate for the extraction region of the pumping well without intercepting the stream) was also specified and interpreted in the configurations for the problem. In the first configuration and when the wells were located at the dimensionless distance of 2×0.4 from each other, the critical flow rate (QCR=1.07) was more than the base flow rate (QBS=0.22). In the second configuration, equality of base and critical flow rates causes a common stream line passed through the stagnation points of the recharge and pumping wells, while the stagnation point of the pumping well was tangential to the stream. In such a situation, the dimensionless value of the distance between the injection-extraction well pair and the dimensionless value of the critical flow rate (which in this case is also equal to the base flow rate) were achieved as 2×1.04 and 0.61, respectively. In the third configuration and when the dimensionless distance between the wells was equal to 2×1.2, the critical flow rate (QCR=0.59) was less than the base flow rate (QBS=0.70). According to the results, the flow rate was determined while the remediation system captured stream’s water and the conditions of entrance of the pollution into the stream from the aquifer were created. Also, the minimum flow rate was determined for the well pair system which can has full and gapless coverage against pollution.