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On June 6, 2011, the Portland Water Bureau submitted a detailed request for a treatment variance to the federal and state requirements of the Long Term 2 Enhanced Surface Water Treatment Rule (LT2).
The request, submitted to the Oregon Health Authority Drinking Water Program (OHA), provides substantial data and analysis in support of the assertion that treatment to address the parasite Cryptosporidium in Portland’s drinking water is unnecessary due to the nature of the City’s Bull Run source. Operating under a variance allows Portland to avoid the costs of building a water treatment facility to comply with the LT2 rule.
Portland’s request shows that the circumstances of the Bull Run watershed significantly limit the risk of Cryptosporidium exposure from the water source.
A year–long intensive water monitoring program for the Bull Run that detected zero instances of Cryptosporidium served as the central basis for Portland’s variance request and substantiates the effectiveness of the natural and policy protections in place for the Bull Run watershed in limiting Cryptosporidium in the drinking water source.
The technical information submitted with the request provides the details of the testing program that characterize the conditions in the Bull Run watershed that account for the consistent low -detection of Cryptosporidium in Bull Run water. The request also presents public health data about infection from Cryptosporidium in the Portland Water Bureau service area and the lack of any documented transmission of the pathogen through drinking water.