Subsurface and Surface Migration of Drilling Additives Down Gradient from the OK Well Field, Moretown, Vermont
Jason O’Neill (ES & GL ’05)
During the early 1990’s, wells were drilled high in the Cox Brook drainage basin in Moretown, Vermont with the hope of obtaining sufficient groundwater to feed several artificial ponds. Depths reached more than 4000 feet in some cases. Complications during drilling required additives such as detergent, KCO 3 fertilizer, and driller’s soap as lubricants. In the fall of 2004, this study was conducted to determine the level of additives still present in the local groundwater and to determine if they had spread into the surface water of Cox Brook which flows through the area. Surface water was sampled from 30 sampling sites at 20-meter intervals through the area bordering the well field and at 3 locations upstream of the well field. Ephemeral tributary streams that passed through the well field were also sampled as were the 7 wells located on the property.
All samples were analyzed with an ICP (Inductively Coupled Argon Plasma Spectrometer) to determine their chemical composition. The study found that the two deepest wells where the abundant additives were used remain highly contaminated in Si, Mg, Ca, Na, and K with total dissolved solids (TDS) reaching 2686 ppm in the most contaminated well.
Evidence was also found that some contaminants have migrated through the groundwater and to wells downstream.
These elements with 86 ppm TDS were also found entering the surface water of the brook through a tributary stream, in lesser amounts. Previous research in the area however, has located a peak in the major elements approximately 1000 feet downstream of my sampling area, indicating that contaminated groundwater from the well field may be entering the surface water at that location.