Were springs more prone to parasite contamination than vertical wells?

Details

The authors stated that groundwater systems need careful monitoring until contamination levels and acceptable risk factors are determined. They compiled data from the detection of Cryptosporidium oocysts and Giardia cysts in 463 groundwater samples. The samples came from 199 sites in 23 of the 48 contiguous states. Groundwater sources included vertical wells, springs, infiltration galleries, and horizontal wells. Samples were analyzed using an immunofluorescence technique.

Across all sources, 12% of sites tested positive for Cryptosporidium, Giardia, or both. Cryptosporidium oocysts were found in 5% of vertical wells, 20% of springs, 50% of infiltration galleries, and 45% of horizontal wells. Giardia cysts were found in 1% of vertical wells, 14% of springs, 25% of infiltration galleries, and 36% of horizontal wells.

The data suggest that springs are at higher risk of contamination than vertical wells. The authors said infiltration galleries and horizontal wells warrant further study because pathogens occur frequently in these sources.