Deep Groundwater Monitoring Challenges and Best Practices After 30 Years of Westbay System Applications Worldwide

Instrumentation of the deep (>2000 ft) groundwater environment for purposes of hydrogeologic testing, in-situ characterization, regional and local characterization and performance monitoring presents formidable challenges. High costs for drilling and completions, difficult access conditions, high ambient pressures and temperatures, difficult in-situ chemistry conditions combined with heightened health and safety concerns make it mandatory to extract the most scientific value from every borehole. These present challenges in selection of appropriate borehole completion technology.

Given the significant investment in borehole drilling and completion there is significantly increased demand for reliable, modular instrumentation suitable for multi-level applications to deliver high-quality, verifiable, defensible measurements from all of the features intersected by the borehole. Nested monitoring wells, typically used in the environmental industry, are cost-prohibitive in such environments and cannot deliver on the requirements for ease of installation, modularity, verification and defensibility.

The Westbay System is a modular borehole completion technology that has been used worldwide on deep groundwater investigations for over 30 years. With a strong background in applications for geologic repository studies involving instrumentation to depths of 4000 ft or more the Westbay System has been accepted internationally as a reliable, high quality technology suitable to meet the performance and flexibility demanded by such high-visibility projects. Other deep groundwater applications include mining projects and hydrogeologic testing and monitoring of deep sub-permafrost environments in Canada's Arctic. From this breadth of experience comes an understanding of industry best practices and the challenges of operation in the deep groundwater environment. This paper describes the Westbay design, typical deep groundwater applications and limitations, and presents example data from several different sites to illustrate how the requirements for high-quality, defensible data are met, and how such data are used in implementation of data gathering and decision-making processes.