Coliform bacteria are microorganisms found in surface water, soil and in feces of humans and animals.  They do not usually cause disease.  However, their presence indicates that fecal wastes may be contaminating the water and means pathogenic organisms could be present.  If human or animal wastes are contaminating the water, gastrointestinal disease, hepatitis, or other diseases may result.  The presence of E. coli in a water sample is more conclusive evidence of fecal contamination which represents an even greater risk than the presence of total coliform bacteria.

Acceptable results: <1 coliform/100 milliliters of water.  If you have coliform bacteria present in a water sample, you should resample.  If a second test shows coliform, take corrective action.

Sources:  Coliform bacteria occur in soils and in the feces of humans and animals.  In areas using fractured bedrock or coarse sand and gravel aquifers, coliform bacteria may contaminate groundwater.  More often, they are an indication of well construction and maintenance faults.

Recommended testing:  Annually for coliform, annually for E.coli is even better.