Compilation and preliminary interpretation of hydrologic data for the Weldon Spring radioactive waste-disposal sites, St Charles County, Missouri — A progress report

This report presents hydrologic and water-quality data collected during an investigation of the Weldon Spring radioactive waste-disposal sites and surrounding area in St. Charles County, Missouri from 1984 to 1986. The data consists of water-quality analyses of samples collected from 45 groundwater and 28 surface-water sites. This includes analyses of water from 4 raffinate pits and from the Weldon Spring quarry. Also included in the report are the results of a seepage run on north-flowing tributaries to Dardenne Creek from Kraut Run to Crooked Creek. Mean daily discharges from March 1985 to April 1986 are presented for two springs located about 1.5 miles north of the chemical plant. Nitrate concentrations ranging from 53 to 990 milligrams per liter as nitrogen were found in 5 monitoring wells near the raffinate pits. In most cases, water from these wells also had elevated concentrations of calcium, magnesium, sodium, sulfate, lithium, strontium, and uranium. Uranium concentrations in ground water were less than 5 micrograms per liter except for 5 sites near the raffinate pits where concentrations ranged from 6.0 to 86 micrograms per liter and 13 sites near the quarry and north of Femme Osage slough where concentrations ranged from 8.9 to 14,000 micrograms per liter. Water from the 6 observation wells sampled south of the slough all had uranium concentrations less than 5 micrograms per liter. This report contains data collected for a hydrologic investigation of the We!don Spring radioactive waste sites and surrounding area from 1984 to 1986. During the first year of the investigation historical information was compiled about the chemical plant, raffinate pits, and the quarry as well as the geology and hydrology of the area. Reconnaisance water-quality and groundwater level data also were collected in 1984. This information and data are presented in an interpretive progress report (Kleeschulte and Emmett, 1986). In 1985 and 1986 additional detailed field data were collected to describe the groundwater flow system, hydrogeologic and water-quality characteristics of the aquifers underlying the area, surface-and groundwater relationships, and quality of surface water. STUDY AREA The study area is located in St. Charles County in eastern Missouri (fig. 1). Two distinct radioactive waste-disposal sites are in the Weldon Spring area. One site consists of the Weldon Spring chemical plant and the four raffinate pits that are located just north of the Mississippi-Missouri River drainage divide. The other site is an abandoned rock quarry (referred to as Weldon Spring quarry) in the bluff adjacent to the Missouri River flood plain and about 3 miles southwest of the chemical plant (fig. 1). Surface drainage at the chemical plant and raffinate pits is toward the north by intermittent tributaries. These tributaries flow into the August A. Busch Memorial Wildlife Area lakes 35, 36, or both, then into Schote Creek, then Dardenne Creek, and eventually into the Mississippi River (fig. 2).

Hydrologic data for the Weldon Spring radioactive waste-disposal sites, St. Charles County, Missouri; 1984-1986

Kleeschulte¹,

Emmett²,

Barks³

1986

Geochemical data for the Weldon Spring Chemical Plant site and vicinity property, St. Charles County, Missouri-1989-1990

Schumacher¹

1990

This report presents geochemical data collected during an investigation of contaminant attenuation within the unconsoidated overburden and shallow bedrock at the Weldon Spring chemical plant site. The data consist of chemical analyses of water samples from 20 groundwater and 5 surface-water sites, mineralogic and chemical analyses of about 70 overburden samples, results from laboratory sorption experiments, and chemical and mineralogic characterization of sludge and interstitial water samples from raffinate pit 3. Concentrations of dissolved nitrite plus nitrate ranging from 24 to 1,100 milligrams per liter as nitrogen were detected in samples from four shallow (less than 110 feet deep) bedrock monitoring wells near the raffinate pits. The samples from these wells generally had increased concentrations of calcium, magnesium, sodium, sulfate, dissolved solids, lithium, and strontium. Concentrations of dissolved uranium (3 to 1 10 micrograms per liter) were detected in samples from all four of these wells. Samples from unconsolidated overburden units at the site consist mainly of silt-size particles (as much as 82 percent of the less than 2-millimeter size fraction) with lesser quantities of clay-and sand-size particles. The predominant mineral in the bulk (less than 2 millimeters) fraction is quartz (36 to 98 percent) with lesser quantities of feldspars, clay minerals, and calcite. Quartz also was the predominate mineral in the clay-size (less than 2 micrometers) fraction. Generally, clay minerals comprise less than 10 percent of the overburden, with the clay till containing the largest average quantities. The predominant clay type is montmorillonite (50 to 95 percent of the total clay minerals). Calcite and other carbonate minerals constitute between an average of 0.7 percent (Ferrelview Formation) and 20 percent (residuum) of the overburden mineralogy. Average contents of Iron ranged from 1.4 percent in the loess to 2.4 percent in the Ferrelview Formation and clay till. More than 95 percent of the lead and 89 percent of the vanadium in a simulated leachate was removed from solutions equilibrated with the Ferrelview Formation or clay till at fixed pH values ranging from 4.5 to 9.0 in laboratory experiments. The maximum sorption of molybdenum (greater than 97 percent) occurred at a fixed pH 4.5 in solutions in contact with either unit. Less than 41 percent of molybdenum was removed at a fixed pH of 7.0 in solutions in contact with either unit and less than 5 percent was removed at a fixed pH of 9.0. At fixed pH values, the maximum sorption of uranium (greater than 97 percent) occurred in solutions at pH 4.5 in contact with the clay till. Slightly larger quantities of sorption (more than 98 percent) occurred in unadjusted solutions in contact with the Ferrelview Formation at initial pH values of 4.5 and 7.0. Conditions least conducive to uranium sorption were at a fixed pH of 7.0 in contact with the clay till where only 52 percent of uranium was removed. Less than 15 percent of sulfate, 19 percent of nitrite plus n...

Geochemical data for the Weldon Spring training area and vicinity property, St. Charles County, Missouri, 1990-92

Schumacher¹,

Sutley²,

Cathcart³

1993

This report presents geochemical and hydrologic data collected during a preliminary investigation of the environmental fate of trinitrotoluene (TNT) and other nitroaromatic compounds at the Weldon Spring training area and vicinity property. Pressure-vacuum lysimeters were installed in the unsaturated zone at four locations along former TNT production lines at depths ranging from 1.9 to 14.2 feet. Large concentrations of TNT from 120 to 31,000 mg/kg (milligrams per kilogram) were detected in surficial soil samples from these areas; however, concentrations in soil-core samples decreased to less than 2 percent of the surface concentrations at depths below 2 feet. Concentrations of TNT (0.46 to 3,070 mg/kg) were detected in 20 of 25 subsurface soil-core samples collected during lysimeter installation. Trinitrobenzene (TNB) was detected in 10 of the soil-core samples at concentrations ranging from 0.21 to 46.2 mg/kg. Six of the soil core samples contained detectable concentrations of 2-amino-4,6-dinitrotoluene (2-Am, 0.34 to 60.2 mg/kg) and one of the samples contained 0.30 mg/kg of 4-amino-2,6-dinitrotoluene (4-Am). Two soil-core samples contained small (2.15 and 4.41 mg/kg) concentrations of 2,4-dinitrotoluene (2,4-DNT) and only one soil-core sample contained a detectable (3.22 mg/kg) concentration of 2,6-dinitrotoluene (2,6-DNT). Total organic carbon contents decreased from an average of 0.17 percent (by weight) in near surface soil core samples to less than 0.05 percent in samples below 1.5 feet in two of the areas instrumented. Although concentrations of TNT decreased rapidly in soil within a few feet of land surface, water samples collected from lysimeters at depths between 1.0 and 4.0 feet contained large concentrations of TNT (4.1 to 6,250 ug/L; micrograms per liter), 4-Am (less than 3.0 to 1,740 ug/L), and 2-Am (5.9 to 246 |ig/L); concentrations of TNB ranging from less than 3.0 to 1,130 |ig/L also were detected in the lysimeter samples. No DNT, nitrobenzene (NB), or nitrotoluene (NT) were detected in any of the lysimeter water samples. A sample from one of the lysimeters (LY05) contained 120 mg/L (milligrams per liter) dissolved sodium, 96 mg/L sulfate, and 80 jig/L copper.