[Home]
[Table of Contents] [Next Section]
Three-Tiered Long Term Monitoring Network Optimization Evaluation
Section 1 - Introduction
Groundwater monitoring programs have two primary objectives (U.S. Environmental Protection Agency [USEPA], 1994; Gibbons, 1994):
Evaluate long-term temporal trends in contaminant concentrations at one or more points within or outside of the remediation zone, as a means of monitoring the performance of the remedial measure (temporal objective); and
Evaluate the extent to which contaminant migration is occurring, particularly if a potential exposure point for a susceptible receptor exists (spatial objective).
The relative success of any remediation system and its components (including the monitoring network) must be judged based on the degree to which it achieves the stated objectives of the system. Designing an effective groundwater monitoring program involves locating monitoring points and developing a site-specific strategy for groundwater sampling and analysis to maximize the amount of relevant information that can be obtained while minimizing incremental costs. Relevant information is that required to effectively address the temporal and spatial objectives of monitoring. The effectiveness of a monitoring network in achieving these two primary objectives can be evaluated quantitatively using statistical techniques. In addition, there may be other important considerations associated with a particular monitoring network that are most appropriately addressed through a qualitative assessment of the network. The qualitative evaluation may consider such factors as hydrostratigraphy, locations of potential receptor exposure points with respect to a dissolved contaminant plume, and the direction(s) and rate(s) of contaminant migration.
This report presents a description and evaluation of the groundwater monitoring program associated with the Camp Stanley Storage Activity (CSSA) in Boerne, Texas. A 97-well monitoring network containing 139 sampling points was evaluated to identify potential opportunities to streamline monitoring activities while still maintaining an effective monitoring program. A three-tiered approach, consisting of a qualitative evaluation, an evaluation of temporal trends in contaminant concentrations, and a statistical spatial analysis, was conducted to assess the degree to which the monitoring network addresses each of the two primary objectives of monitoring, and other important considerations. Results of the three evaluations were combined and used to assess the optimal frequency of monitoring and the spatial distribution of the components of the monitoring network, and were also used to develop recommendations for optimizing the monitoring program at CSSA.