That depends on what type of soil is between the ground water and the facility. If it is relatively organic free, coarse sand and gravel the pathway to the ground water is open. If you have organic rich fine material like clays and silt the contamination would be greatly retarded for traveling to the ground water. It also depends on the direction of flow and slope of the water table. Working in the field one of the biggest threats we are facing is the contamination of ground water from salt. States use large amounts of road salt and brine to keep our roads safe in the winter, unfortunately that salt has to go somewhere like surface water such as ponds and lakes or seep into the ground water.