Five Ways to Reduce CCR Remediation Costs Before Corrective Action Decisions Are Locked In
By the time a groundwater remedy is selected at a coal combustion residuals (CCR) site, some of the biggest opportunities to control its cost may already be gone.
The questions that shape decades of spending—what approach will work, how long it will operate, and what it will ultimately cost—often hinge on decisions made much earlier.
A conventional groundwater remedy such as pump-and-treat can be effective, but it can also be expensive and require decades of operation and maintenance. In some cases, a more targeted remedy, or monitored natural attenuation (MNA), may achieve the necessary results at considerably lower lifecycle cost. The key is developing enough understanding of site conditions and constituent behavior to identify the most appropriate approach before selecting the remedy and committing to remedy implementation.
Here are five early steps that can help utilities preserve options and better manage lifecycle costs:
1. Develop and continually refine the conceptual site model
A reliable conceptual site model (CSM) provides the foundation for virtually every decision that follows. It integrates site history, geology and lithology, hydrogeology, and groundwater chemistry to explain how groundwater flows and constituents move through the site. It also helps assess the risk associated with pathways leading to potential constituent exposure to human and ecological receptors.
The CSM should not be viewed as a static product. Initial site information can identify important data gaps, which can then be addressed through targeted investigation. The resulting information further refines the CSM and helps focus subsequent evaluation on the conditions most likely to affect remedy selection.
2. Evaluate potential sources
Understanding the source of CCR constituents found in groundwater can be an important early step. Elevated constituent concentrations may not necessarily be attributable to the CCR unit, and evaluating other potential sources can provide the technical basis for an alternative source demonstration.
Potential alternative sources are site-specific and may include other site activities, off-site influences, or naturally occurring sources. Constituents such as arsenic, cobalt, and lithium are often naturally occurring components of soil and rock and may be released to groundwater through natural geochemical processes.
Understanding these potential sources early can have significant implications for both the remedy and its lifecycle cost. A technically defensible alternative source demonstration may establish that some groundwater concentrations are not attributable to the CCR unit (e.g., may be naturally occurring), potentially avoiding unnecessary corrective action for those constituents.
3. Determine what natural processes are already accomplishing
Utilities should also evaluate whether natural attenuation processes can help meet groundwater protection standards within a reasonable time frame.
Evaluating the mechanisms, rates, and long-term effectiveness of natural attenuation through sufficient data and multiple lines of evidence can help determine whether MNA is a viable remedial approach and what additional investigation or active remediation, if any, may be needed. When site conditions support it, MNA may provide an effective corrective measure while avoiding unnecessary infrastructure and long-term operating costs.
4. Conduct targeted predesign investigations
Existing monitoring networks can provide a broad understanding of site conditions without necessarily providing all the detailed and localized information needed to evaluate and design a remedy. Targeted pre-design investigations focus on potential remediation areas and fill specific data gaps identified through the CSM.
This can be particularly important in complex hydrogeologic settings such as fractured bedrock, where groundwater flow and constituent transport may be controlled by discrete fracture networks. Targeted investigations can provide detailed information about constituent distribution, hydraulic connectivity and groundwater flow pathways that broader monitoring networks may not provide.
The key is reducing these uncertainties early, while utilities can still influence the approach and its lifecycle cost.
5. Perform treatability and pilot testing before remedy selection decisions are locked in
Laboratory treatability studies and field pilot testing provide site-specific information on treatment effectiveness, amendment selection and dosage, delivery methods, radius of influence, and potential secondary effects. Field pilot testing can also help evaluate how a treatment approach performs under actual site hydrogeologic and geochemical conditions. These results can help determine whether a prospective remedy is likely to perform as expected and can be used to evaluate and optimize potential treatment approaches before remedy selection decisions become locked in.
Better information supports better decisions
Reducing lifecycle remediation and compliance costs isn’t simply about finding a less expensive way to implement a remedy. It starts with developing the site-specific information needed to determine the appropriate corrective action.
By investing earlier in understanding site conditions, constituent sources, natural attenuation processes, risk assessment, and remedy performance, utilities can reduce uncertainty before it becomes embedded in corrective action—and potentially decades of lifecycle cost.
Joe Smith, PE, is a Managing Engineer and Wayne Weber, PE, PG, is a Principal Engineer at Anchor QEA.
Get in touch with Joe Smith to learn more about Anchor QEA’s CCR services.