The Coffey County Kansas Portion of the Neosho River Alluvial Aquifer
by Wade Camp
GO571 Geohydrology (Spring 2007)
The purpose of this project is to discuss the groundwater in Coffey County, Kansas; with an emphasis on the Neosho River Alluvial Aquifer. The hydrological setting, hydrologic, and geologic properties of the aquifer will be described. There will be a discussion of the aquifer as a water source for domestic agricultural and industrial uses. Lastly, sources of ground water contamination including radionuclides from Wolf Creek Generating Station will be discussed.
Hydrologic Setting and History
The Neosho River begins in Morris County, Kansas. It then flows for about 95 miles and is joined by the Cottonwood River, its major tributary in Kansas. It will later be joined by the Spring River and Elk River in Oklahoma prior to becoming a tributary to the Arkansas River just North of Muskogee, Oklahoma. The river historically has had severe variations in flow such as periods of zero flow and periods of severe flooding(6). The record flood occurred in June and July of 1951. Flow was 408,000 cfs(3). It flooded most of downtown Burlington including the Post Office.
The Flood Control Act of 1950 led to the creation of a system of three flood control reservoirs on the Neosho River. Though the primary reason for the reservoirs was flood control, they were also to improve water supply and quality in addition to providing recreation. The John Redmond Reservoir is one of these three and is located in Coffey County three miles northwest of Burlington.
Coffey County Lake, which serves as the Wolf Creek Generating Station cooling lake, was formed by damming Wolf Creek four miles upstream of where it joins the Neosho River. The watershed area for Coffey County Lake is not enough to sustain the lake at the levels required for Wolf Creek Generating Station so water is purchased from John Redmond Reservoir and periodically pumped via large lake Make Up Pumps to fill and maintain level in Coffey County Lake. In the aerial photograph, John Redmond Reservoir is located to the left and Coffey County Lake to the right. The Neosho River can be seen exiting John Redmond Reservoir to the southeast and is joined by Wolf Creek near the bottom of the photo.
Meteorology and Aquifer Recharge
Coffey County, Kansas is known for long hot humid summers dominated by tropical air from the gulf of Mexico and moderate winters dominated by dry air from the northwest. Heavy rainfall of up to 11 inches in as little as 24 hrs can occur, however, precipitation normally ranges from 30-38 inches per year with 10- 20 inches of snow. This is the primary method of aquifer recharge with a recharge rate of 6-8 inches per year. Stream bed leakage and leakage from the reservoirs also recharge the aquifer(7).
The Neosho River Basin is made up of alluvial and terrace deposits. The Neosho River aquifer is a stream-valley aquifer. Stream-valley aquifers are generally unconfined and made up of unconsolidated sediments with high hydraulic conductivity. Many stream-valley aquifers have yields of up to 3000 gpm. In general the larger the river valley, the larger the yield.(4). The Neosho River stream-valley aquifer, where it flows through Coffey County, is relatively small, the depth to the water table is about 20 ft with yields of about 0-10 gpm(7). The water level in the Neosho aquifer rises and falls with the flow of the river just as it does with many alluvial aquifers due to the high hydraulic conductivity(4).
As can be seen from the map above, the specific yield is about 0.15 and since the aquifer is unconfined it would be expected that storativity value is similar.
Storativity is equal to specific yield plus aquifer thickness times specific storage. Specific storage is normally a small number for an unconfined aquifer. This leads to a storativity of about .15 for the Neosho River alluvial aquifer(1). The water flow rate is limited and it has a high mineral content so most large users opt for surface water treatment plants. It is mostly farms and very small towns that use wells for drinking water. There is very limited agricultural use of the aquifer(7).
The area of Coffey County outside the Neosho Valley aquifer is made up of layered sedimentary deposits of Plattsmouth Limestone, which yields less than 1 gpm to wells; Toronto Limestone, which yields less than 2 gpm; the Ireland member of the Lawrence formation which yields about 0.5 gpm; and Tonganoxie Sandstone which yields less than 3 gpm. Layers are relatively flat and flow of ground water outside the Neosho River Basin is determined more by surface features than underground deposit configuration. From this it can be seen that the Neosho River alluvial aquifer is the dominant groundwater source in Coffey County(7).
Possible aquifer contaminates include agricultural runoff of pesticides, herbicides and fertilizers. There is also the possibility of leaky underground fuel tanks and many above ground tanks used for local oil wells(6). The area of Coffey County has the additional concern of possible radioactive contaminants from Wolf Creek Generating Station. Wolf Creek Nuclear Operating Corporation personnel perform periodic monitoring of areas adjacent to the plant for possible radioactive releases. Kansas Department of Health and Environment personnel perform additional monitoring and their monitoring is compared against the WCNOC monitoring to verify consistency(2). There has been considerable attention recently given to the problem of tritiated waste from nuclear facilities. All U.S. nuclear power plants including Wolf Creek Generating Station have recently increased their groundwater monitoring because of issues that have been discovered with tritium at other plants.
Tritium is a radioactive form of hydrogen with one proton and two neutrons. It can be formed as water flows through a nuclear reactor and hydrogen atoms absorb neutrons. Chemically it reacts just like hydrogen in the form of tritiated water. This water will taste and smell just like regular water but will be radioactive. The main problem with tritium is that since it reacts just like hydrogen it is impossible to remove using demineralizers. Demineralizers are cation and anion resins that are used to remove radioactive ionic impurities from water prior to discharge. Tritium is a beta emitter with a 12.5 yr half life. Normally any tritium that is discharged from a nuclear power plant is diluted to such an extent that it poses no harm to local residents. Some Nuclear Power Plants have had problems with leaks from the pipes that carry tritiated water for discharge prior to the dilution occurring. The plants mentioned in NRC INFORMATION NOTICE 2006-13 had various leaks to groundwater that resulted in tritium being detected in local wells. In most cases the levels were below drinking water standards but any elevated levels is a cause for concern(5). Wolf Creek generating station is uniquely located such that ground water flows toward the station and cooling lake and away from local wells. The cooling lake almost surrounds the generating station offering a very large dilution volume. There is limited groundwater use in Coffey County due to the limited resources and the availability of surface water as mentioned earlier(7). This coupled with groundwater monitoring by the KDHE and WCNOC personnel should ensure that those same events do not happen there.
1. Fetter, C. W., 2001, Applied Hydrogeology 4th Ed. Upper Saddle River: Prentice-Hall Inc., p.102
2. Kansas Department of Health and Environment, 2005, Report of Radiological Environmental Monitoring of the Environs Surrounding Wolf Creek
Generating Station. World Wide Web. < http://www.kdheks.gov/radiation/download/2005_ERS_Report.pdf>accessed 5/1/2007
3. United States Army Corps of Engineers(USACE). John Redmond Website. <http://www.swt.usace.army.mil/projects/civil/civil_projects.cfm?number=18>accessed 5/1/2007
4. Miller, James A. and Appel, Cynthia L., 2005, United States Geological Survey. Ground Water Atlas of the United States Kansas Missouri Nebraska. World Wide Web<http://capp.water.usgs.gov/gwa/ch_d/D-text1.html>accessed 5/1/2007
5. United States Nuclear Regulatory Commission, 2006, NRC INFORMATION NOTICE 2006-13: GROUND-WATER CONTAMINATION DUE TO UNDETECTED LEAKAGE OF RADIOACTIVE WATER. World Wide Web <http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/2006/in200613.pdf>accessed 5/1/2007
6. United States Public Health Service Office of Stream Sanitation. Grand (Neosho) River Investigation Cincinnati. 1940
7. Wolf Creek Nuclear Operating Corporation, 2007, Wolf Creek Generating Station Updated Safety Analysis Report (USAR) Rev. 20, Ch 2
All photographs taken by the author with the exception of the aerial photograph.