3. a landfill is leaking an effluent with a concentration of sodium of 1250 mg/l. it seeps into an aquifer with a hydraulic conductivity of 9.8 ml day, a gradient of 0.0040, and an effective porosity of 0.15. a downgradient monitoring well is located 25 m from the landfill. what would the sodium concentration be in this monitoring well 300 days after the leak begins? note: in this problem you will fetter, c. w.. applied hydrogeology (p. 440). waveland press, inc.. kindle edition.