Lessons Learned from Groundwater Modeling to Support Engineered Solutions for Post-Excavation CCR Basin Water Management

For CCR basins constructed in steam valleys in the southeastern United States and planned for closure by excavation, post-closure groundwater control is often required. Numerical simulations suggest that groundwater elevations may intersect planned final grades, creating uncertainties in future groundwater-surface water interactions and requiring proactive engineered solutions supported by a solid understanding of complex geology and hydrology.

This presentation reviews lessons learned from recent projects in the Carolina Piedmont, emphasizing targeted field data collection, conceptual site model (CSM) development, and iterative numerical modeling to guide closure design. High-quality water level and flow data are critical for defensible hydrologic analysis. Case studies show how heterogeneous and transient site conditions, such as shallow bedrock, uncertain historical channel geometry, evolving basin conditions, and water management, affect groundwater responses, reinforcing the need for a well-defined CSM to support reliable model predictions.

Water budget analysis links field data, modeling, and design by quantifying surface and groundwater contributions, evaluating storm and recharge variability, and identifying controlling factors in model calibration. Catchment basin delineation is critical, as the magnitude of inflow directly affects drainage sizing and long-term performance. Integrating those insights into groundwater models improves accuracy when evaluating closure elements such as groundwater collection systems, stormwater channels, sumps, soil backfill quantities, and performance goals.

By comparing results across multiple projects, this presentation highlights recurring challenges, strategies to reduce uncertainties, and practical considerations in developing effective, regulator-ready engineered designs. These lessons can help streamline future monitoring, design, permitting, and performance evaluation for CCR basin closure across the region.

A Cost-Effective, Low-Impact Remedial Approach for Metals: Utilizing Phyto-Enhancement to Accelerate pH Adjustment of Shallow Groundwater

Thomas Colton, P.E., and Jerry Wylie, P.G., will present a unique remediation strategy that accelerates natural attenuation processes. The approach employs pH adjustment of groundwater using agricultural lime coupled with the use of daikon radish to augment lime contact time and to increase depth of soil augmentation. This method is designed to be a more sustainable, less resource-intensive, and less technically challenging remedial alternative with lower estimated overall costs.

The primary corrective action—source removal—has been completed. However, the oxidation of residual sulfide-bearing minerals has resulted in persistent low-pH groundwater, which increases the solubility and mobility of metal constituents of interests (COIs). While long-term natural attenuation is expected, low-pH conditions could persist for decades; therefore, an evaluation of remedial options was completed to accelerate COI attenuation mechanisms.

The selected remedy is the application of agricultural lime (CaCO₃) to the shallow subsurface to increase pH and buffering capacity in groundwater and unsaturated soil, thereby decreasing COI mobility and concentrations. Application dosage rates and details were developed following a baseline evaluation and analysis of subsurface soil conditions.

Although infiltrating rainwater will naturally carry the higher-pH water deeper into the water-bearing unit, SynTerra developed a simple, low-cost enhancement using daikon radish root channels (phyto-enhancement) to accelerate lime movement into the groundwater. This enhancement is expected to expedite the buffering capacity of the water-bearing unit and the time needed to decrease COI mobility. A robust monitoring well program is already established to track performance. The final assessment design, site characterization results, and lime application calculations will be presented, along with initial observations from the novel pilot study. 

Fully custom GIS tool helps land management firms navigate complex challenges

SynTerra’s latest project for a conservation land management firm involves digitizing and georeferencing physical maps into an interactive ArcGIS Online tool and augmenting those maps with layers of essential data such as property boundaries, infrastructure details, and environmental features. SynTerra will also integrate freshly captured aerial imagery and LIDAR data obtained through advanced drone technology.

This comprehensive GIS platform is designed to facilitate efficient and informed decision making for future master planning and land management of our clients’ holdings. By integrating historical data, applicable GIS layers, and cutting-edge technology, our fully custom tool empowers our conservation land management clients to navigate complex challenges and embark on new development projects with precision and confidence.

Business executive Travis Waters is SynTerra’s new president.

Posted July 14, 2022

GREENVILLE, SC — SynTerra Corp., a science and engineering consulting firm, announced today that Travis Waters is the company’s new president.

SynTerra has made significant efforts to streamline business operations over the past couple of years. Today, the firm has approximately 100 employees and five offices in three states with the ability to serve clients nationwide.

The SynTerra Board of Directors searched nationwide for top-tier candidates who shared the same vision and values as the company. “I am both humbled and excited about the opportunity to help this great organization further expand and grow to become the premier environmental and engineering consulting firm in the Southeast,” said Waters.

Waters, who has led companies in sales, marketing, and business operations for the past 20 years, is experienced in attracting new business segments and negotiating strategic contracts. Waters has managed multimillion-dollar global accounts and has developed key business verticals with revenue exceeding $900 million. Waters also brings an entrepreneurial spirit; he has succeeded in several business ventures of his own.

Waters has given back to his community over the years through volunteer work. He served as the Chairman of the Board of Directors at the Big Brothers Big Sisters Foundation and volunteered as a driver for Meals on Wheels America.

Founded in 1992, SynTerra is employee‐owned. SynTerra engineers, geologists, scientists, and data professionals help clients meet business objectives and address technical challenges. Clients include manufacturers, mining operations, utilities, pulp and paper companies, developers, and government agencies. Capabilities include environmental consulting, water and wastewater design, civil engineering design, air and wetlands permitting, surveying and drone applications, and more. Headquartered in Greenville, SC, SynTerra also has offices in Cary, NC, Charlotte, NC, Lexington, KY, and Pikeville, KY. Learn more about SynTerra at www.synterracorp.com.

Get the report — Coal Combustion Residuals: Environmental Risk and Remedy

ABSTRACT: Coal combustion residuals (CCR), commonly known as coal ash, are created when coal is burned by power plants to produce electricity. Coal ash is one of the largest types of industrial waste generated in the United States, with several sites in the Carolinas having coal ash impoundments and landfills. Coal ash can contain constituents like mercury, selenium, and arsenic. Without proper management, these constituents can contaminate waterways, groundwater, drinking water, and air.

The EPA finalized national regulations to provide a comprehensive set of requirements for the safe disposal of CCR from coal-fired power plants. The federal CCR Rule establishes technical requirements for CCR landfills and surface impoundments, and it addresses risks from coal ash disposal, e.g., leaking of contaminants into groundwater, blowing of contaminants into air as dust, and the possible failure of coal ash surface impoundments. This rule also supports the responsible recycling of CCRs by distinguishing safe, beneficial use from disposal.

This presentation will provide an overview of the federal CCR rule and associated state regulations, and it outlines many of the CCR compliance activities we are conducting at current and former coal-fired power plants. Activities include comprehensive site assessments focused on groundwater flow characterization and the nature and extent of coal ash constituents occurring in groundwater, soil, surface water, and sediments. Based on the comprehensive site assessments, corrective action plans have been developed in coordination with the state regulatory agencies. Corrective action plans were based in part on human health and ecological risk assessments that determined whether the occurrence of specific coal ash constituents necessitates remedy.


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The EPA finalized national regulations to provide a comprehensive set of requirements for the safe disposal of CCR from coal-fired power plants. The federal CCR Rule establishes technical requirements for CCR landfills and surface impoundments, and it addresses risks from coal ash disposal, e.g., leaking of contaminants into groundwater, blowing of contaminants into air as dust, and the possible failure of coal ash surface impoundments. This rule also supports the responsible recycling of CCRs by distinguishing safe, beneficial use from disposal.

This presentation will provide an overview of the federal CCR rule and associated state regulations, and it outlines many of the CCR compliance activities we are conducting at current and former coal-fired power plants. Activities include comprehensive site assessments focused on groundwater flow characterization and the nature and extent of coal ash constituents occurring in groundwater, soil, surface water, and sediments. Based on the comprehensive site assessments, corrective action plans have been developed in coordination with the state regulatory agencies. Corrective action plans were based in part on human health and ecological risk assessments that determined whether the occurrence of specific coal ash constituents necessitates remedy.

Get the full report