Portland currently has no system for treating cryptosporidium. That makes it the only place in the country where water is taken from surface-level sources (i.e. not underground) and passed on to consumers without treating it for crypto.
For a long time, that wasn’t a major problem, because Bull Run water is so high-quality and the watershed heavily protected.
But in December 2011, water monitors detected a lone crypto parasite for the first time since 2002. A federal EPA regulation created in 2006 mandates that crypto treatments be installed wherever an outbreak is possible. However, another federal law allows states to give certain bureaus an exception if the general water quality is outstanding.
After the 2011 detection, the Portland Water Bureau requested such an exception – or variance – from the Oregon Health Authority. OHA granted that variance in early 2012, citing the quality and protection of Bull Run.