The Need for Groundwater Monitoring Systems
What is a Groundwater Monitoring System and What is it Used for?
A groundwater monitoring system is typically a series of wells completed into one or more aquifers, depending on the objectives of the system. Groundwater monitoring systems are installed for many different purposes, generally including evaluation of groundwater water quality and water levels. The monitoring can be in one aquifer, one stratum within an aquifer, or could be installed to monitor multiple aquifers.
Injection Well
Groundwater monitoring systems have long been used to characterize industrial sites and the potential for activities to degrade groundwater quality. The requirement has typically been “one up and three down," meaning one well has to be installed upgradient of site activities that are suspected or known to be causing groundwater contamination issues, and then three wells downgradient of the suspected/known contamination to characterize the fate and transport of contaminants in the groundwater. However, this general criterion would only apply to a very well-defined area of concern. If the potentially-affected area is large, or there is the potential for vertical migration from the uppermost aquifer into deeper saturated strata, the extent and scope of the monitoring well system has to be expanded to fully characterize the area and aquifers of concern.
The monitoring well system may initially be installed for detection monitoring to characterize any releases of constituents of concern into the uppermost aquifer, as well as potential vertical migration. The wells can then be used to collect water quality samples from the monitoring wells and analyzed for specific indicator parameters related to the potential release. These data can be used to evaluate if a release has occurred to the groundwater and the extent of that contamination. If releases are identified through the detection groundwater monitoring, then it is likely that compliance monitoring of the groundwater well system will be required.
Typically, concentrations at the upgradient well are compared to the concentrations at the downgradient wells so that inter-well statistical analyses can be developed to understand the statistical increase in concentrations in a downgradient direction. To conduct these types of analyses it is necessary to collect multiple samples to develop a baseline sample set. From that point forward, the water quality data can be utilized to assess statistically-significant increases (SSIs) from the upgradient to the downgradient wells. If there are suspected or known SSIs, compliance monitoring is then required, which is designed to control and remediate the groundwater contamination so the risk to human health and safety is protected.
Compliance monitoring is designed to ascertain whether the constituents released to the uppermost aquifer are exceeding acceptable concentration levels and threatening human health and the environment. Once an exceedance of an applicable standard has been confirmed, the facility must take action to bring the constituent concentration levels back into compliance with the standard, or standards, depending on the level of contamination. To achieve this, the facility typically must either remove the constituents of concern from the aquifer or treat the contamination in place. In either case, the monitoring system is designed to identify, characterize, and remediate groundwater contamination associated with a site so adjacent groundwater users are protected. Potential groundwater remediation techniques will be discussed in a future LWS blog.
This isn’t the only use of groundwater monitoring systems! In many cases, water level monitoring is also set up to establish groundwater level conditions, as well as transient changes in water levels with time. Two examples are monitoring well systems used in mining projects where the pre-mining hydrologic regime needs to be understood so the post-closure period baseline conditions can be re-established. Another example is the Denver Basin where the water in storage is being mined, i.e., water levels are generally declining and are not recovering on a seasonal basis because there is little to no recharge to the deep bedrock system.
Denver Basin
LWS has set up numerous water quality and water level monitoring networks and have tailored each monitoring system to the specific needs of the project, including understanding the target aquifer(s) characteristics.
If you have a need for a water resources firm to help with the design and/or implementation of an effective groundwater monitoring plan tailored to your needs, please reach out and we will be happy to put together a plan for your needs. We help with projects big and small.
Bruce Lytle, President of LWS: bruce@lytlewater.com
Chris Fehn, Senior Project Engineer: chris@lytlewater.com
Ben Bader, Project Hydrogeologist: ben@lytlewater.com
Anna Elgqvist, Senior Engineer: anna@lytlewater.com
