The City of Independence, Missouri operates a well field within the city limits of Sugar Creek, Missouri, in the Missouri River alluvial aquifer (fig. 1). About 250,000 people in several communities are supplied water from the 23 million gallons per day (mgal/d) average daily production from the well field. Planned development in the vicinity of the well field has heightened awareness of potential sources of ground-water contamination and created the need to monitor ground-water quality near the well field. Development includes extension of an existing landfill 0.5 to 1.0 mile south of the alluvial plain and within the Mill Creek watershed that drains into the alluvial plain, commercial development near the existing well field, highway construction adjacent to the well field, and expansion of the well field to the west and north of the river. In addition, nearby highway and rail line traffic, the use of fly ash for mine stabilization south of the well field, a closed oil refinery south of the well field, land application of solid waste across the river to the west, and nearby agricultural activity have raised concerns about accidents and human activity that may adversely impact ground-water quality.
Figure
1. Location of the Independence, Missouri well field and study area.
Seasonal changes in ground-water quality of the alluvial aquifer can be caused by changes in land use activities such as the seasonal use of agricultural chemicals, changes in aquifer recharge caused by seasonal changes in the rate of rainfall and evapotranspiration, river stage fluctuations that can cause river water to enter the aquifer or cause the aquifer to drain into the river, or the application of salt to roads during winter months. Agricultural chemicals commonly are applied in the spring before planting but recharge can occur in late fall or winter. The most widespread sources of potential ground-water contamination to the Independence well field are non-point source areas related to agricultural use of fertilizers and pesticides. Numerous potential point sources also exist near the well field. The types of potential sources of ground-water contamination within the contributing recharge area of the Independence well field are agricultural, commercial, highways, industrial, landfills, rail roads, residential, solid waste land application, mining, and water ways (Kelly, 1996b). The long-term presence of these potential sources of ground-water contamination increases the probability that contamination of the aquifer may occur. However, the quality of ground-water in the ZOC (zone of contribution), the part of the aquifer from which the well field obtains its water, was unknown at the beginning of this study.
In response to the ground-water quality concerns, the U.S. Geological Survey and the dity of Independence, Missouri completed a study of ground-water flow to the well field (Kelly, 1996b). Results of the study include types and locations of potential ground-water contamination source areas, analysis of changes in ground-water flow, changes of ground-water travel time and contributing recharge areas from planned well-field expansion, and the design of a ground-water monitoring network for the Independence well field consisting of 75 wells in 35 clusters.
To maximize the effective use of the monitoring well network to detect ground-water contamination, a detailed sampling plan was developed. In addition, overall ground-water quality and seasonal variations of agriculturally derived chemicals in the 10-year ZOC were characterized by analyzing ground-water samples from monitoring wells in the network during 1998, 1999, and 2000. Regular sampling and analysis of ground water from the monitoring well network, analysis of water quality of the Missouri River, and periodic updating of the sampling plan according to the criteria described above can be used to detect ground-water contamination in the future.
Kelly and Blevins, 1995, Vertical hydraulic conductivity of soil and potentiometric surface of the Missouri River alluvial aquifer at Kansas City, Missouri and Kansas--August 1992 and January 1993, USGS Open-File Report 95-322.
Kelly, 1996a, Simulation of ground-water flow and contributing recharge areas in the Missouri River alluvial aquifer at Kansas City, Missouri and Kansas, USGS Water Resources Investigations Report 96-4250
Kelly, 1996b, Design of a monitoring well network for the City of Independence, Missouri well field using simulated ground-water flow paths and travel times, USGS Water Resources Investigations Report 96-4264.
This study was jointly funded by the city of Independence, Missouri, and the U.S. Geological Survey.
Brian P. Kelly
U.S. Geological Survey
401 NW Capital Drive
Lee's Summit, Missouri 64086
PHONE: (816) 554-3489
FAX: (816) 554-9273
E-MAIL: bkelly@usgs.gov
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