Hydrologic characteristics and response of fractured till and clay confining a shallow aquifer

Ground-water hydrology and subsurface migration of radioisotopes at a low-level solid radioactive-waste disposal site, West Valley, New York

“…The difference between simulated pressure heads and those observed at piezometers in February 1976 was least when the model included two layers, the upper layer (which corresponded in thickness to the distance from land surface to the base of the oxidized fractures) being 10 times more permeable than the lower layer, and both layers being anisotropic with a 100:1 ratio of horizontal to vertical hydraulic conductivity. Simulating the upper layer as more permeable than the unweathered till is consistent with the presence of fractures and root tubes near land surface, and also with results of studies elsewhere (Grisak and Cherry, 1975) that showed that fractures in till significantly increase its permeability. However, the indication of strong anisotropy in the unweathered till seems inconsistent with the lack of regular stratification and the lack of evidence for widespread horizontal migration of water from the trenches (discussed in section "Subsurface migration of radioisotopes").…”

A GIS-based vulnerability assessment of brine contamination to aquatic resources from oil and gas development in eastern Sheridan County, Montana

“…One of the primary goals of this project was to include surficial geology in the vulnerability assessment as the STEPPE project and previous studies (Beal et al, 1987) have shown that brine contamination can migrate further in coarse-grained glacial outwash deposits than clay-rich glacial till. The upper portion (top 6.1 m) of glacial tills and lacustrine deposits in the PPR are often oxidized and vertically fractured which increases the hydraulic conductivity (Grisak and Cherry, 1975); however, glacial outwash deposits have a much greater hydraulic conductivity compared to unfractured and fractured till; 1.2 × 10 −7 -1.2 × 10 −3 m/s compared to 1 × 10 − 12 -1.2 × 10 − 5 m/s, respectively (Schwartz and Zhang, 2003). Additionally, glacial till is the predominate deposit and much more prevalent than glacial outwash in the PPR (76.1% and 10.4% in our study area, respectively) and the majority of oil wells are located in glacial till.…”

Prediction of soil salinity risk by digital terrain modeling in the Canadian prairies

“…Extensive deposits of unfractured glacial clayey and silty till and glaciolacustrine clay can isolate buried aquifers. However, in some locations, these groundwaters can discharge through networks of vertical and nearly vertical fractures passing through layers of till and clay (Grisak and Cherry 1975;Grisak et al 1976). The hydraulic conductivity of fractured till and clay can provide significant secondary permeability to depths of hundreds of meters (Williams and Farvolden 1967;Freeze and Cherry 1979).…”