Spatial and Temporal Variability in Seepage Between a Contaminated Aquifer and Tributaries to the Ohio River

Abstract

Although ground water discharge‐can limit plume migration and transfer contaminants to streams, interactions among ground water, rivers, and tributaries in contaminated watersheds have received relatively little attention. We used multiple methods to delineate seepage along Little Bayou and Bayou Creeks, tributaries to the Ohio River in McCracken County, Kentucky, from July 1996 through July 1998. The Paducah Gaseous Diffusion Plant (PGDP) lies between the creeks. Trichloroethene (TCE) and technetium‐99 plumes within the underlying Regional Gravel Aquifer (RGA) extend several kilometers from PGDP toward the river. Both creeks tend to gain flow where they are incised into the RGA or contiguous strata in the Ohio flood plain. Bayou Creek also gains flow upstream of PGDP; other reaches of both creeks tend to lose flow. Local storms, river floods, and seasonal dry periods caused temporary changes in seepage rates and reversals in hydraulic gradients. Gaining conditions were indicated by seeps, springs, and boils, by upward hydraulic gradients from bank wells and bed piezometers to the stream, and by mixing models using chloride and oxygen‐18. Mixing models and downward hydraulic gradients from the stream to wells indicated losing conditions. Annual ranges of stream, bed, and bank temperatures tended to be narrower, bed and bank temperatures in summer and early autumn tended to be cooler, and maximum values of specific discharge measured by seepage meters were greater along gaining than along losing reaches. Estimates of specific discharge from stream gauging and one‐dimensional flow‐modeling did not conclusively identify losing and gaining reaches, but absolute values of those estimates fell within the range of seepage‐meter measurements. Contaminants discharging to Little Bayou Creek were diluted downstream by uncontaminated ground water. Volatilization, biodegradation, or sorption probably removed TCE from stream water. These results indicate that discharge to tributaries can limit seepage of contaminants to rivers.

Using Tracer Tests to Assess Natural Attenuation of Contaminants along a Channelized Coastal Plain Stream

“…This article describes potential processes of natural attenuation in Little Bayou Creek, a first-order perennial stream in McCracken County, KY. Little Bayou Creek is fed by springs containing trichloroethene (TCE) and technetium-99 ( 99 Tc) from past activities at the U.S. Department of Energy's (DOE) Paducah Gaseous Diffusion Plant (PGDP), a uranium-enrichment facility (Fryar et al, 2000;LaSage, 2004). Observed TCE concentrations decrease downstream of the springs, suggesting natural attenuation by one or more processes, including dilution, volatilization, sorption, and microbially mediated reduction within anaerobic microsites of the otherwise oxygenated streambed sediments.…”

Integrating seepage heterogeneity with the use of ganged seepage meters

“…Since the advent of the "Lee-type" or "half-barrel" seepage meter (Lee 1977), this device has been widely used for measuring seepage fluxes in lakes (Connor and Belanger 1981;Erickson 1981;Woessner and Sullivan 1984;Loeb and Hackley 1988;Welch et al 1989;Isiorho and Matisoff 1990;Lesack 1995;Rosenberry 2000;Sebestyen and Schneider 2001), wetlands , estuaries (Lee 1977;Zimmerman et al 1985;Yelverton and Hackney 1986;Simmons Jr. 1992;Land and Paull 2001;Linderfelt and Turner 2001), and near-shore ocean margins (Cable et al 1997;Shinn et al 2002;Taniguchi 2002;Chanton et al 2003;Michael et al 2003). The device also has been used in river settings where currents were small (Connor and Belanger 1981;McBride 1987;Belanger and Walker 1990;Duff et al 1999;Fryar et al 2000).…”

A Technical Assessment of the Current Water Policy Boundary at U.S. Department of Energy, Paducah Gaseous Diffusion Plant, Paducah, Kentucky

“…This is the likely explanation for the very low concentrations of the TCE sampled in springs along the Little Bayou Creek (see Fig. A-1 where Little Bayou Creek has cut deeply into the Metropolis Formation, almost reaching the RGA), as reported by Fryar, et al 2000;Mukherjee, et al 2005;and LaSage, et.al. 2008a and b.…”

“…The general geology is illustrated in the cross-section presented as Fig hence do not present continuing concerns regarding the surface water (Fryar, et al 2000;Mukherjee, et al 2005;LaSage, et al 2008a and b). Further, field work in the area north of the PGDP facility to the Ohio River have found no indications to date of liquefaction features (or other indications of surface sediment disruption) that would suggest the area has been subjected to shallow sediment faulting or associated depressurization of groundwater in confined sediments within or above the RGA.…”