Effective porosity of unconsolidated sand; Estimation and impact on capture zone geometry

Abstract

Effective and total porosity were measured for three sand samples, and a computer model was used to evaluate the impact of effective porosity (ne) on the geometry of a groundwater capture zone. Estimates of effective porosity ranged from 90 to 94 percent of values obtained for total porosity. While the magnitude of effective porosity is inversely proportional to capture zone area, the upgradient radius of capture is most sensitive to changes in the magnitude ofne. Incremental changes in the magnitude ofne have the greatest impact on capture zone radii for low values ofne. The results of this study suggest that: (1) a simple permeameter and vacuum pump apparatus can facilitate the estimation of effective porosity for unconsolidated sands, (2) the magnitude of effective porosity is close to that of total porosity for unconsolidated sand, and (3) accurate estimates of effective porosity are important for modeling the remediation of contaminated groundwater with capture zones.