title: Ground and surface water interaction near a plywood manufacturing facility on the Lake Roosevelt shoreline, Kettle Falls, Washington
Creators: name: Humphreys, Paul W. D.
Publisher: name: Western Washington University
Year: 1998

description: <p>From April 1994 to December 1996, a water quality investigation was performed at the Boise Cascade Plywood Plant in Kettle Falls, Washington. This investigation was required by the Washington Department of Ecology to assess possible contamination from the process water lagoon and wet log storage area on the groundwater and nearby Lake Roosevelt. Water samples were collected from 11 groundwater monitoring wells, the lagoon, and two lake-shore seeps, and the samples were analyzed for a variety of chemical parameters. Water elevation data were also collected to evaluate the physical nature of the interaction between ground and surface water. The primary water bearing zone at the site is the coarse-grained lower aquifer beneath the lagoon area where the occurrence and behavior of groundwater is strongly correlated with Lake Roosevelt. The groundwater elevations in the wells which monitor this aquifer rise and fall with the lake, and very little groundwater gradients were observed between wells. The groundwater beneath the log storage area also rises and falls with Lake Roosevelt, but more substantial groundwater gradients were observed. These gradients appear to be at least partly caused by the finer-grained sediments in this area, where the wells respond more slowly to changes in lake level. The groundwater beneath the log storage area is also generally higher than beneath the lagoon area. This is likely caused by additional groundwater entering the site from the hills to the east. The finer-grained sediments in the log storage area presumably retain this added head longer than the sediments in the lagoon area where the additional head would dissipate relatively quickly in the coarser-grained sediments. The direction of groundwater flow in the lagoon area is toward Lake Roosevelt when the lake is falling and away from Lake Roosevelt when the lake is rising. In the log storage area, the groundwater gradients indicate groundwater flow toward both the lagoon and the lake. However, a thick section of silt and clay separates the log storage area from the lake, so the majority of groundwater flow out of the log storage area is likely northward via the coarser-grained sediments beneath the lagoon area. A silt and clay layer overlies the lower coarse-grained aquifer and forms a basin of unconfined perched groundwater beneath the lagoon. This perched groundwater appears to have been impacted by the lagoon with respect to chemical oxygen demand, chloride, total dissolved solids, tannin and lignin and dissolved manganese. The lower aquifer in the lagoon area also appears to have been secondarily impacted to a lesser degree by gradual seepage of these contaminants from the overlying perched groundwater. However, the thick layer of silt and clay at the site largely mitigates surface impacts on the lower aquifer in the lagoon area and on all of the groundwater beneath the log storage area. Activities in the log storage area do not appear to have significantly impacted the groundwater beneath the site. The perched groundwater beneath the lagoon does not appear to discharge into Lake Roosevelt, and this groundwater is unlikely to directly impact the lake. The groundwater in the lower aquifer beneath the lagoon area is in direct communication with the lake, and over time, any contamination in this groundwater will eventually discharge into the lake. The seeps do not appear to represent discharge locations for any of the water bearing zones monitored at this site. Rather, the seeps appear to be discharge locations for a second perched groundwater zone which probably exists between the seeps and an unlined storm water collection area. Infiltrating storm water would contribute a relatively high organic load to any underlying perched groundwater and would explain the elevated chemical oxygen demand and tannin and lignin concentrations found in the seep water as well as the iron and manganese precipitation observed at the seep outlets.</p>