PORTLAND, Ore. - Faced with contamination by a parasite, the city may have to install a water filtration and purification system for its two Bull Run reservoirs.

Much of Portland's drinking water comes from the reservoirs, in the Bull Run watershed near Mount Hood.

The city Water Bureau detected low levels of Cryptosporidium at the Bull Run source-water intake earlier this year.

Faced with this news, the Oregon Health Authority on May 19 revoked a variance that allowed the city to use the water without treating it.

The City Council will weigh options at a work session in June. Meanwhile, the OHA expects the city to take short-term measures to prevent the spread of the parasite.

The city Water Bureau insists that Bull Run water is still safe to drink.