SIMULATING BACTERIAL AND VIRUS TRANSPORT THROUGH THE RIVERBED DURING STORM EVENTS, AT A SITE OF INDUCED INFILTRATION

Riverbeds have the capacity to filter contaminants from infiltrating river water in losing streams because of their low hydraulic conductivity. The filtration processes in the riverbed, combined with the filtration capacity of the underlying aquifer material, have been globally utilized to supply clean drinking water at sites of riverbank filtration. These are sites where production wells have been placed close to rivers in order to induce river water infiltration and increase groundwater supplies. It has, however, been demonstrated that storm events can compromise the integrity of riverbeds (scour, increased riverbed conductivity) and potentially increase the risk of groundwater contamination. This study investigates the potential effects of storm events on groundwater quality at a site of riverbank filtration along the Great Miami River (GMR) in Fairfield Ohio. At this site, riverbed scour of up to 6 inches have been observed (using load cell pressure transducers) while riverbed conductivity has been modeled (using temperature modeling in VS2DH) to increase up to two orders of magnitude during storm events. Transport of bacteria and viruses were modeled to assess the potential movement of these contaminants from the GMR to a monitoring well located between the river and the production well. Preliminary results predicted an increase (by more than a factor of 2) in the breakthrough of these contaminants during storm events at the above mentioned well. The transport of these contaminants is directly related to the flux increase during different storm events. Even though the well used in this study is not a drinking water production well (the production well is much farther away from the river), such a predicted increase in bacteria and virus break through would have more serious impacts at a site where the production well is very close to the river.