An investigation into low levels of an industrial solvent found in two now-closed city wells is entering its next phase as investigators try to determine how the chemical contaminated the aquifer supplying Columbus’ drinking water.
Officials from Intera, a geoscience and engineering solutions company with offices in Bloomington, completed a report on the status of the city’s south wellfield, where wells 14 and 15 were shut down last October after 1,4 dioxane was detected.
Columbus is one of several Indiana cities that tested above the .35 parts per billion Environmental Protection Agency recommended limit for the solvent, testing at .48 parts per billion in the city water system in 2013.
Through a variety of testing options, Intera officials had new information for Columbus Utility Board members Thursday about where the 1,4 dioxane is in the aquifer supplying Columbus’ water.
But the company cannot yet say where the chemical originated or how far north or south it may have spread, only that it has been detected at the bottom of the aquifer between the wells and the river.
To test water in the aquifer, the company installed a network of monitoring test wells and did soil borings looking for the location of the chemical and how far it had spread.
However, the company concluded that the results indicated the contamination was higher near the river and originated east of wells 14 and 15, believed to be at the bottom of the aquifer near those wells, Moore said.
Moore said it is possible the chemical could be found at new locations the city might consider for a well field.
Columbus’ drinking water is from groundwater obtained using 22 gravel-packed wells and two filtration plans, according to Columbus City Utilities.
Since there is some interaction between the river and the aquifer, investigators must also determine how that groundwater is moving and where.