ABSTRACT
Groundwater flow in the Eastern Snake River Plain aquifer in southeastern Idaho, USA takes place where the upper vesicular element of a basalt flow, with its partings, fissures, and broken basalt contacts the often-rubbly substratum of the overlying flow. This generally highly transmissive zone represents a small fraction of the aquifer, however, contaminants may diffuse throughout the whole aquifer thickness. Remediation in the Snake River Plain aquifer must take these transport and storage characteristics into account. To begin evaluating the consequences of this ftramework, 20 basalt core samples are being analyzed to determine porosity, hydraulic conductivity, and diffusivity. Porosity ranges from 4.3 to 9.7% for dense basalt and 6.9 to 11.8% for vesicular basalt. Hydraulic conductivity ranges from 1.4 × 10−8 to 3.6 × 10−6 cm/sec for dense basalt and 2.3 × 10−8 to 1.6 × 10 6 cm/sec for vesicular basalt. Experiments completed to date indicate diffusion formation factors ranging from 1.5 × 10−2 to 1.7 × 10−3 for dense basalt and 8.6 × 10−2 to 2.6 × 10−3 for vesicular basalt.
