Yesterday, the Portland Water Bureau (PWB) received preliminary laboratory results indicating the presence of Cryptosporidium in water samples from the Bull Run source collected on December 30, 2011. The lab results show that one Cryptosporidium oocyst was present in a sample collected at the raw water intake. A second oocyst was present in a sample collected from a location further upstream. Follow-up lab results received today from samples taken at the raw water intake on January 1st, 2012 and January 3rd, 2012 showed no further evidence of Cryptosporidium.
PWB has informed (see letter) the the Oregon Health Authority (OHA) and the Multnomah County Health Department of the preliminary lab results and neither agency has indicated a concern regarding any public health effects. No special precautions are necessary for Portland’s drinking water customers.
In the midst of a high volume sampling program, it is not unexpected that a small number of Cryptosporidium organisms would occasionally be found in untreated surface water. Wildlife is present in the watershed and can be a source of Cryptosporidium. Detections of Cryptosporidium in water from the Bull Run, however, are rare.
Today’s results are the first to indicate the presence of Cryptosporidium at the Bull Run raw water intake since 2002. Since the last detection of Cryptosporidium, PWB has collected over 725 samples totaling over 19,269 liters without finding it. PWB is now conducting increased monitoring at the raw water intake according to the terms identified in the Interim Sampling Plan which has been in effect since December 2010.
PWB is arranging for additional analysis of the positive sample including DNA testing which may provide genotype information which could help PWB better understand and characterize the significance of this detection and indicate the possible animal source.
PWB will continue to implement the interim monitoring plan as it awaits a final decision from OHA regarding a potential variance to the treatment requirements of the federal Long Term 2 Enhanced Surface Water Treatment Rule (LT2). OHA has indicated that it intends to issue a final decision on the variance by the end of this month. Based on the comprehensive information and monitoring data compiled and transmitted by PWB in its variance request, we do not believe these isolated detections which have prompted no public health concerns affect the City’s underlying case for a variance.
PWB will continue to closely track and report Bull Run water quality monitoring results as we seek to understand and provide additional information about this rare, but not extraordinary event.
David G. Shaff, Administrator, Portland Water Bureau
