U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting Charleston South Carolina March 8-12, 1999--Volume 3 of 3--Subsurface Contamination From Point Sources, Water-Resources Investigations Report 99-4018C

Effects of Lithology and Fracture Characteristics on Hydraulic Properties in Crystalline Rock: Mirror Lake Research Site, Grafton County, New Hampshire

By Carole D. Johnson

ABSTRACT

A combination of subsurface borehole imaging data and drilling logs were used to characterize the fractures and lithology in 40 bedrock wells at the fractured-rock research site in the Mirror Lake area in Grafton County, New Hampshire. The purpose of the research was to determine whether subsurface lithology and fractures have an effect on the hydraulic conductivity of the crystalline-rock aquifer in the Mirror Lake area. The distribution of fractures and lithology was quantified with respect to depth, altitude, topographic setting, and spatial distribution. The density of fracturing was described and comparisons were made between lithology, fracture characteristics, and hydraulic-conductivity measurements. Fracturing was found to be related to lithology, depth, and topographic setting. No clear correlation was established between hydraulic conductivity and fracture properties including alteration, oxidation, aperture, orientation, and density.