Abstract: In 2000, a multi-year trial commenced in Bass River to evaluate the effects of a 30 meter grass buffer in filtering E. coli bacteria horizontally and vertically from fall applied liquid dairy manure. Treatments of a control and manure application of 4000 gal/ac were established on one-acre plots replicated two times on a uniform 5% slope. The soil type used was from the Mount Hope series, which has reduced permeability at a depth of approximately 30-cm. Downslope of the treatment area surface and subsurface collectors were established at 10 meter intervals and staggered across a 30-meter buffer. Following fall rain events, water samples were collected from each of these collectors. These samples were tested for E. Coli. A weather station was established at the site to record precipitation and minimum and maximum outside air temperatures. Initial trends suggest that the buffer does filter out much of the E. Coli over the 30 meters, both in the surface and subsurface samples. At the same time, temperature appeared to have a reducing effect on E. Coli populations when minimums went below zero over a period of 2 days or more. More detailed analysis over a longer period of time is required to evaluate such trends at a statistical level.