1941 - City's well No. 1 goes on line.
1942 - U.S. Public Health Service establishes arsenic standard in drinking water at 50 parts per billion.
1969 - State health officer in a news article "condemns" the city's water supply.
1974- Under Safe Drinking Water Act, U.S. Environmental Protection Agency issues national interim arsenic standard of 50 ppb.
1975 - City puts advisory question on election ballot asking if residents want to pay to treat arsenic. Vote is overwhelmingly no.
1979 - City commissions a study to determine feasibility and cost to remove arsenic. Study concludes that using reverse osmosis would cost $13.5 million, activated alumna would cost $5.3 million, and coagulation would cost $8.5 million.
1990 - City signs compliance agreement with state health department. City commits to treating arsenic once federal standard is published. Interim arsenic standard remains at 50 ppb. City agrees to add surcharge on water bills and collect $1 million in fund to treat arsenic. City agrees to notify public of arsenic content in municipal water.
1991 - City seeks commitment from U.S. Environmental Protection Agency to finance an epidemiological study of health effects of arsenic.
April 2000 - City contracts with water consulting firm Shepherd Miller to test water chemistry, design treatment facility, and choose a location.
August 2000 - Region 9 office of the U.S. Environmental Protection Agency issues city administrative order to treat arsenic by September 2003.
2001 - EPA adopts 10 ppb arsenic standard.
August 2002 - EPA gives city an extension of six months to complete arsenic plant, pushing the construction deadline to December 2003.
April 2004 -Treatment plant operating.