Specific indicator organisms can define the magnitude and origins of non-point pollution in rural environments

Graduation date: 1980A comprehensive study was made on the impact to surface and ground water pollution by a recently populated rural neighborhood located in the foothills of western Oregon. A stream originating in a limited access forest and flowing through a modern zoned housing development was routinely monitored. Sampling was performed during steady state low flow and high flow conditions, and during the rising and falling hydrograph of storm events. Bacterial levels were found to be one to two log units higher in the unprotected regions of the stream compared to levels in the protected forest. To determine the source of fecal pollution in the stream, fecal streptococci were randomly picked and biotyped. It was demonstrated that sources of fecal contamination in the stream included human feces, as evidenced by the presence of S. mitis and S. salivarius during stormwater runoff. This was attributed to use of septic drain-fields in soils unsuitable for such use. Other contributors were domestic livestock and wildlife, as manifested by the isolation of S. bovis and S. equinus. To determine the effects of seasonal variation and modern zoning criteria on drinking water supplies, six surveys over a fifteen month period were conducted. More than one third of the water supplies were unsatisfactory on at least one occasion in terms of standard plate counts over 10³ /ml, the presence of coliforms, fecal coliforms, and/or Staphylococcus aureus. Coliform contamination was found to be higher following periods of rainfall, while high standard plate counts were more prevalent during warmer weather. Consumer education and a twice yearly monitoring of private water supplies appear necessary to reduce the incidence of water-borne disease organisms in private water supplies