The City of The Dalles Wastewater Treatment Plant has experienced an upset which has resulted in discharge of effluent exceeding the plant’s limit for E. coli.  Public Works Department officials say that today one of the twice-weekly tests for E. coli in the plant’s effluent to the river exceeded 406 organisms per 100 milliliters, the limit for a single sample.  As required by the City’s federal permit for the plant, a series of five samples at 4-hour intervals was initiated, and that sampling is currently underway and will continue to be taken until E. Coli counts are back within permit limits.  Signs are being posted along the Columbia River as designated locations to notify the public about the potential contamination.  The cause of the upset is unknown at this time and under investigation.