U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993, Water-Resources Investigations Report 94-4015

Use of a Borehole Color Video Camera to Identify Lithologies, Fractures, and Borehole Conditions in Bedrock Wells in the Mirror Lake Area, Grafton County, New Hampshire

Abstract

A submersible color camera was used to describe bedrock lithologies and fractures in boreholes at the U.S. Geological Survey fractured-rock research site near Mirror Lake, Grafton County, New Hampshire. From June through August 1992, video surveys were completed in 29 bedrock wells that ranged in depth from 60 to 230 meters. Use of the submersible camera was prompted by a need to verify and provide additional descriptions of rock types identified in the wells. In two of the wells from which bedrock core was collected, video images together with drill cuttings were used to determine lithologies. These lithologies corresponded to lithologies determined directly from bedrock core samples collected from two wells. For wells from which core was not obtained, video images were used to improve the interpretations of the rock types that were based only on initial logs made at the time of drilling and later detailed examinations of drill cuttings. In addition, the images were used to inspect the conditions of the borehole walls for angularity, stability, or blockage.