Annual report of monitoring at Barnes, Kansas, in 2011.

Barnes, Kansas, is a small rural community (population approximately 150) located in Washington County, in north-central Kansas (Figure 1.1). The city lies in a transition zone between the Flint Hills and the glaciated region. The area's topography consists of gently sloping hills of Pleistocene loess (< 20 ft) overlying a shale unit and interbedded shale, limestone, and siltstone of the Permian Chase Group. Groundwater for the public water supply is obtained from wells PWS2 and PWS3 at reported depths of 155 ft and 160 ft, respectively, located in the northwestern portion of the city. The water is produced from the bedrock aquifer of the Chase Group. Section 2 summarizes of the hydrogeologic conceptual site model. The findings of the monitoring events at Barnes in 2011 continued to support the following previous conclusions: (1) Measurements of groundwater levels obtained manually and through the use of automatic recorders have consistently indicated that the flow direction is strongly influenced by pumping of the public water supply wells. The results have demonstrated an apparent groundwater flow direction to the northeast when the public wells are not pumping and a northwesterly groundwater flow trend when the public wells are pumping. (2) Evaluation of manual water level measurements and carbon tetrachloride concentrations continues to suggest that three vertically distinguishable aquifer zones are present at Barnes: shallow, intermediate, and deep (Table 4.1). The highest concentration of carbon tetrachloride occurs in the intermediate zone, in wells near the former CCC/USDA grain storage facility. Lower concentrations have been detected in the deep aquifer zone (where the public water supply wells are screened), and no carbon tetrachloride has been detected in the shallow zone. (3) The conceptual model of the groundwater flow system at Barnes, as postulated on the basis of the accumulated results, suggests that the observed vertical hydraulic gradients and higher carbon tetrachloride concentrations in the intermediate zone might reflect generally lower permeability and hence less effective groundwater and contaminant migration in the intermediate zone than in the deep aquifer zone. (4) As it has since March 2008, intermediate-zone well MW10S, in the eastern portion of the former CCC/USDA facility, contained the highest concentrations of carbon tetrachloride. (5) Overall, the lateral distribution of carbon tetrachloride in groundwater in 2011 is similar to the distribution during previous sampling events. The accumulated data, including a trend analysis conducted in 2009, indicate stable contaminant concentrations, with no imminent impact to the public wells