INFLUENCE OF BOREHOLE CONSTRUCTION ON LNAPL SAMPLING

Electrical resistivity images taken at sites contaminated with light non-aqueous phase liquids (LNAPL) often image LNAPL being affected by the location of boreholes as either an attractive or repulsive feature in the subsurface. This mechanism results in an anomalously low or high estimate of the amount of LNAPL in the formation using data sampled from wells. A numerical model was constructed to determine if the hydraulic conductivity contrast between a borehole and natural media has a significant enough effect to create either a convergent or divergent two phase flow field around a borehole which would lead to inaccurate LNAPL measurements. This has significant implications regarding site closure standards at LNAPL contaminated sites.