Blasting and groundwater contamination - Case study

ANFO was being used as one of the blasting agents on a construction site in New England. Groundwater was encountered in numerous blast holes. The blasting contractor was employing typical explosives loading procedures for wet conditions. An abutter to the project complained that blasting caused her well water to have an odd taste and smell. Through testing, it was determined that there were hydrocarbons and nitrates in the well water. Several days later a second neighbor complained of foul tasting water; again it was determined that hydrocarbons and nitrates were present. The project's owner installed a series of groundwater monitoring wells in the vicinity of the water well contamination and the site's property boundary. Groundwater samples showed the area of contamination to be concentrated around the two homeowners' wells. The project owner alleged that blasting was the cause of the problem. The owner began to pump the groundwater monitor wells in an attempt to lower the assumed groundwater table so that explosives could be placed in dry blast holes. In doing so, the contamination plume was drawn onto the construction site. Groundwater samples also began to detect increased concentrations of nitrates. Again, the owner alleged that ANFO was the source. Continental Placer Inc. (CPI) conducted extensive review of the blasting contractors field practices, blast log data, the owner's geologic data and existing research on nitrate contamination from ANFO. We applied site-specific parameters to the available research data to prove that ANFO was not the source of either the hydrocarbon or nitrate contamination.