Data updated daily between midnight and 6 am.Ohio EPA Division of Drinking and Ground Waters maintains the Ambient Ground Water Quality Monitoring Network as part of an effort to characterize general water quality conditions in Ohio. This program was established in 1967 to measure seasonal and annual water quality changes in the state's major aquifers. The network initially consisted of 12 large production wells, and was expanded to 60 wells in 1972. In 1986, the network was further expanded to around 90 wells. A large number of public water supply wells were added to the network in the late 1980s and early 1990s to provide better representation of the major aquifers in Ohio. The program currently includes over 200 wells (stations). Of the total stations, roughly 85 percent are public water systems and 15 percent are industrial or commercial enterprises or residential. Raw water is analyzed for a suite of inorganic parameters every six, 18, or 36 months depending on the total number of samples that have been collected and the stability of the geochemistry of major elements at the site. Samples are also analyzed for volatile organic compounds once every 18 or 36 months. Some ambient sites have historical semi-volatile organic compounds and pesticide data.