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r <br />Update of Toxicity Testing on outfall 011 <br />Somerset Mining Company is required by the facility's National <br />Pollutant Discharge Elimination Systems (NPDES) permit to conduct <br />routine acute biomonitoring quarterly for outfall 011 with P. <br />oromelas (fathead minnow) and Ceriodaohnia dubia. outfall 011 has <br />a history of high alkalinity which is believed to be a source of <br />toxicity for C. dubia at this site. <br />Second quarter biomonitoring testing was conducted on samples taken <br />June 11, 1995. Testing protocol for C. dubia was modified with a <br />procedure designed to lower the alkalinity level and to remove <br />toxicity associated with total dissolved solids levels in the <br />effluent. This modification allows the removal of Bi-Carbonates by <br />lowering the pH to 3.0. Allowing for at least one hour for COz <br />dissipation, the sample was then adjusted to it's initial pH and <br />then routine testing was conducted using this adjusted effluent for <br />t~~tirg with C. dubia. <br />The effluent from June 11, 1995 was not toxic to fathead minnow but <br />the modified effluent was toxic to C. dubia. In accordance with <br />this facility's permit to discharge a Toxicity Identification <br />Evaluation (TIE) was scheduled for July 18, 1995. Due to <br />insufficient numbers of organisms the complete TIE was not run on <br />this date. <br />-1- <br />COM MERCIAL TESTING & ENGIN EE RING GO. <br />=-066 ~~~ <br />Original Watermerketl For Vour Protection , , <br />