KDHE explains how contamination can move from a spill to ground water.
Ground water flows much more slowly than surface water, such as rivers. Unlike surface water that runs mainly in a straight line from higher to lower elevations, ground water does not move through an open channel. Instead, ground water moves between soil particles or through fractures in rock. Soil at the Barsol property is composed of clay and silt near the surface and sand farther below the surface, where ground water is encountered. In the area around the Barsol property and Valley Center, ground water, which is approximately 15 to 22 feet below the ground surface, moves through the sand aquifer at approximately one foot per day to the south-southwest towards the Little Arkansas River.
Ground water becomes contaminated as chemicals move from a source through the soil and into the ground water. This can occur when rainwater infiltrates into contaminated soil and dissolves the contaminant. Infiltration rates depend on several factors including precipitation, the type of soils, and how fast water can travel through the soil. The response work being conducted at the Barsol property, including the removal of water, spilled chemicals, and contaminated soil will minimize the potential for contaminants to migrate through the soil to the ground water.