The City of Port Angeles says:
The Water Utility maintains the city drinking water system from a well on the Elwha River to the meter by your house... The water system has approximately 189 miles of pipe ranging from 2 to 30 inches in diameter, 3 water booster pump stations, 5 reservoirs with 18 million gallons of storage and about 7,928 service connections. The water is disinfected using sodium hypochlorite (household bleach) and no other chemicals are added. The water supply is obtained from a 60 foot deep Collector Well next to the Elwha River which is a few miles west of town. The well and pumping system is designed to provide 11 million gallons per day (mgd).
Newspaper article from the Peninsula Daily News helps clarify the question of the PA water supply and the construction projects which are prerequisite to the Elwha Dam removals. Aha: this very recent article amends the question of what chemicals they are using, and says the water treatment plant completion dates are 2009 and 2010. (The dams don't come out until the plants are operating, you understand...)