The risk of human illness from contact with surface waters is correlated to the concentrations of certain species of bacteria found in those waters. The relative presence of Fecal Coliform, Enterococcus, and Total Coliform are used as indicators for the possible presence of microbial human pathogens. 

DRBC has adopted water quality criteria for bacteria (unit of measurement is cfu/100mL) protective of primary contact uses, such as swimming and kayaking, and secondary contact uses, such as fishing.