Determination of the key hydrodynamic parameters of the fault zone using colloidal borescope in the Dawu well field and strategies for contamination prevention and control

The Dawu well field is located in a large petrochemical production base area near the city of Zibo. Groundwater near the fault zone in the well field area was affected by the surface petrochemical pollutants, and it is in urgent need of targeted treatment. However, how to accurately determine the actual flow velocity, runoff velocity and hydraulic conductivity in the karst aquifer under the background of large-scale pumping is the key for effective pollution control. In this paper, based on the newly developed technology of colloidal borescope, seven detection wells are arranged in the selected 21 layers in the polluted section of the fault zone in the well field area and the dominant flow theory and geostatistical method are employed. The results show that (1) the strong runoff layer (easily polluted) of the aquifer near the fault zone in the Dawu karst groundwater well field area is located from the lower part of the Badou Formation (O_2-3b) to the upper part of the Gezhuang Formation (O₂g), and groundwater within 65 m is the main water source of karst groundwater pollution in the area. (2) Groundwater near the fault zone has multiple particle flows, and the runoff direction and flow velocity in different sections are quite different, which is related to the pumping intensity. (3) In the treatment of groundwater pollution in the Hougao section, optimization and adjustment of groundwater exploitation should be made: the transportation of shallow flow (70 m) should be reduced to greater than the runoff velocity of SW95 (50.30 m/d), and the transportation of 80~110 m should be reduced to less than the runoff velocity of SW99 (49.38 m/d).