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A heavy rain fell throughout the Mad River Valley on Saturday night and Sunday, July 9, and 10, and is the likely contributor to high E. coli levels in many reaches of the watershed this week. Water samples taken by Friends of the Mad River volunteers on Monday morning, July 9, showed favorable swimming conditions in the middle reaches of the Mad River from the Lareau swim hole to the Meadow Road bridge, but equally unfavorable swimming conditions in Blueberry Lake, the upper reaches of the watershed in Warren, and the lower sections of the Mad River in Moretown down to the Winooski River.Twenty-one of 37 sampling sites tested were in violation of Vermont's water quality standard of 77 colonies per 100 milliliters of water. The bacterial pollution developed as water levels in the low river were sharply increased by heavy rain causing a low and rising (LR) flow condition. Flow readings at the USGS gage in Moretown (http://waterdata.usgs.gov/nwis/uv/?&site_no=04288000) increased from a low of 34 cubic feet per second on Saturday, July 7, to a high of 158 cubic feet per second recorded on Monday, July 9, at the time of the Mad River Watch sampling.