The U.S. Geological Survey, in cooperation with the Missouri Department of Conservation and the city of Columbia, Missouri, collected hydrologic data from September 1993 through October 1996 as part of a hydrologic characterization of the Columbia/Eagle Bluffs Wetland Complex. The wetland complex was constructed in the Missouri River alluvial plain adjacent to the Columbia municipal supply wells. Part of the wetland complex was designed to treat sewage effluent from Columbia, with the treated effluent being used as the primary water source for wetland management practices on the Eagle Bluffs Wildlife Area. This report presents hydrologic data and the procedures used to collect the data, which include water-quality analyses of samples collected quarterly from 28 wells and 2 surface-water sites. Four additional wells were incorporated into the monitoring network in November 1994 and also were sampled quarterly. Data from these 4 wells also are included.

Water samples were analyzed for specific conductance, pH, temperature, dissolved oxygen, bacteria, alkalinity, major cations and anions, nutrients, trace elements, and total and dissolved organic carbon. Dissolved nitrite plus nitrate as nitrogen concentrations were equal to or less than 5.2 milligrams per liter for all ground-water samples and were equal to or less than 2.7 milligrams per liter in surface-water samples. Dissolved phosphorous concentrations ranged from less than 0.01 to 2.2 milligrams per liter in the ground-water samples, and from less than 0.01 to 0.19 milli-grams per liter in the surface-water samples. Fecal coliform bacteria counts ranged from less than 1 to 39 colonies per 100 milliliters for ground-water samples, and from 1 to greater than 6,000 colonies per 100 milliliters for surface-water samples. Fecal streptococcus bacteria counts ranged from less than 1 to 92 colonies per 100 milliliters for ground-water samples, and from 2 to greater than 10,000 colonies per 100 milliliters for surface-water samples. Samples for well USGS-6 had dissolved arsenic concentrations that exceeded 50 micrograms per liter. Dissolved manganese concentrations exceeded 50 micrograms per liter at least once for each site except for USGS-9S. Dissolved iron concentrations exceeded 300 micro-grams per liter at least once for 28 of 34 sites.

Samples from 8 of the 32 wells and both surface-water sites were analyzed for base/neutral/ acid semi-volatile organic compounds, selected pesticides, selected organochlorine compounds, and purgeable volatile organic compounds. All but one of the organic compounds detected in the samples collected from the monitoring wells or surface-water sites were pesticides. Atrazine was detected consistently at both surface-water sites. Other frequently detected pesticides include metolachlor, diazinon, chlorpyrifos, prometon, and simazine.

Following the 1993 Missouri River flood samples of residual flood water and flood-deposited sediments were collected from the Columbia/ Eagle Bluffs Wetland Complex. A brief description of the flooding and damage to the study area is presented. Methods of collection of the four residual flood water and the four flood-deposited sediment samples, as well as the analytical results of these samples, are included in this report. Data from two continuous water-level recorders and from quarterly water-level measurements in wells also are included.