The Dalles Public Works Department says operations at the municipal wastewater treatment plant are improving but are not yet back in compliance after a recent plant upset that resulted in discharge to the Columbia River of treated wastewater exceeding the plant’s limit for E. coli.   On Tuesday samples were taken at pre-arranged locations in the Columbia River to determine the effect of the discharge on water quality in the river.  Tests on five samples taken between River Mile 186.5 and 189.5 show that E. coli levels at the sample locations were well below bacterial criteria set by the Oregon Department of Environmental Quality for freshwater recreation.  The Dalles Public Works says plant staff is working to restore the biological balance so that the plant can quickly return to normal operations.  As a precaution, signs advising no water contact will remain in place at locations of public river access until the discharge from the wastewater treatment plant returns to compliance.  Signs are posted on the Oregon shore of the Columbia River, from The Dalles Riverfront Park to West Mayer Park boat launch.