By B.G. Justus and Gregory P. Stanton
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SIR2004-5273 (2.53 MB)
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The Fort Chaffee Maneuver Training Center is a facility used to train as many as 50,000 Arkansas National Guardsmen each year. Due to the nature of ongoing training and also to a poor understanding of environmental procedures that were practiced in the World War II era, areas within Fort Chaffee have the potential to be sources of a large number of contaminants.
Because some streams flow on to Fort Chaffee, there is also the potential for sources that are off post to affect environmental
conditions on post. This study evaluates constituent concentrations
in water, fish tissue, and bed sediment collected from waterbodies on Fort Chaffee between September 2002 and July 2004.
Constituent concentrations detected in the three media and measured at nine stream sites and four lake sites were compared to national and regional criteria when available. Two of the larger streams, Big and Vache Grasse Creeks, were sampled
at multiple sites. All three sampled media were analyzed for insecticides, PCBs, explosives, and trace elements. Additionally,
water samples were analyzed for nutrients and herbicides.
The different constituents detected in the three sample media (water, fish tissue, and bed sediment) indicate that land-use activities both on and off post are influencing environmental
conditions. Contaminants such as explosives that were sometimes detected in water samples have an obvious relation to military training; however, the occurrence and locations of some nutrients, insecticides, and trace elements suggest that land use both on and off post also could be influencing environmental
conditions to some degree.
Constituent concentrations at sites on Vache Grasse Creek, and particularly the most upstream site, which was located immediately downstream from an off-post wastewater-treatment
facility, indicate that environmental conditions were being influenced by an off-post source. The most upstream site on Vache Grasse Creek had both the highest number of detections and the highest concentrations detected of all sites sampled. Event-mean storm concentrations and storm loads calculated from storm-flow samples at two sites each for Big and Vache Grasse Creeks indicate that storm loads were highest at the two Vache Grasse Creek sites for 24 of the 25 constituents detected. Further evaluation by normalizing storm loads at Big Creek to storm loads at Vache Grasse Creek by stream flow indicate that event loads at Vache Grasse Creek were about two or more times higher than those on Big Creek for 15 of the 25 constituents
measured. Low concentrations of arsenic and lead were detected in water samples, but all detections for the two trace elements occurred in samples collected at the upstream site on Vache Grasse Creek. The nickel concentration in fish livers collected
from the upstream site on Vache Grasse Creek was 45 percent higher than the median of a national study of 145 sites. Mercury concentrations in edible fish tissue, which are a widespread
concern in the United States, exceeded an USEPA criterion
for methylmercury of 300 µg/kg in four of nine samples; however, concentrations are typical of mercury concentrations in fish tissues for the State of Arkansas.
Constituent concentrations at some sites indicate that environmental
conditions are being influenced by on-post activities. Of the 55 (excluding total organic carbon) organic constituents analyzed in water samples, only 10 were detected above the minimum detection limit but four of those were explosives. Bed-sediment samples from one site located on Grayson Creek, and nearest the administrative and residential (cantonment) area, had detections for arsenic, copper, lead, manganese, nickel, and zinc that were above background concentrations, and concentrations for arsenic and nickel at this site exceeded lowest effect level criteria established by the U.S. Environmental
Protection Agency. The site on Grayson Creek also had the only detections of DDT metabolites in bed sediment.
Concentrations of some trace elements in all media sampled
for this study could also have a relation to on-post activities or conditions. Some trace elements detected may result from the combined effects of sedimentation (a possible consequence of soil erosion resulting from training activities and an extensive road system) and trace element concentrations in soils in western
Arkansas. Regarding sedimentation (and soil erosion), turbidity
data collected at the most downstream site on Vache Grasse Creek, and observations of substantial sediment deposition
in both Vache Grasse and Big Creeks indicate that turbidity and associated sedimentation is a chronic problem that is impairing the ecological integrity of Fort Chaffee streams. Trace element concentrations at some sites may be related to this chronic sedimentation and the associated redox potential of the aquatic environments sampled.
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