groundwater protection council

May 4, 2022

SCS Engineers Environmental Consulting and Contracting
DWI and carbon sequestration are environmental solutions that permanently isolate fluids and gases in deep geologic formations. To ensure these materials stay there and don’t impact useable resources, groundwater, or the environment in any way, use SCS Engineers with experts in geologic consulting, reservoir engineering, and deep drilling to plan, permit and execute solutions that support your environmental objectives.


Join EPA, SCS Engineers, and the GWPC for the 2022 Annual GWPC & UIC Conference in Salt Lake City, from June 21 through June 23. This year’s event features two experts from SCS, Kacey Garber and Stephanie Hill. In today’s blog, we take a dive into their presentations, where both women use case studies to highlight safely using deep injection wells, and what can happen during operations to plan for more sustainable operations.

Thursday, June 23 at 8:30-10:00 Class VI UIC
Sensitivity of Aquifer Chemistry to Changes in Carbon Dioxide Partial Pressure: Implications for Design of Groundwater Monitoring Protocols,” Kacey, Julie O’Leary, and Charles Hostetler are all with SCS Engineers. The team will discuss Carbon Sequestration and Storage (CSS) solutions. Great care is taken in the design and operation of the injection of carbon compounds to ensure that the sequestration is effective and permanent. Each injection site also has permitting requirements for groundwater monitoring in any overlying aquifer as a protective measure. Because the duration of the injection and sequestration periods are long, it is essential for CSS projects to have a cost-effective groundwater monitoring program with a robust sensitivity to detect any leakage.

In this case study, the SCS team has examined the sensitivity of aquifer chemistry (major and minor cations and anions) to the partial pressure of carbon dioxide using an aqueous speciation/solubility/sorption model. They examined a number of hydrochemical facies, both natural and synthetic, to determine which geochemical parameters are most likely to be affected by changes in the partial pressure of carbon dioxide. The team anticipates that the regulatory framework and practice for CSS will be similar to that of Municipal Solid Waste (MSW) and Coal Combustion Residue (CCR) disposal sites. Prior to the injection of carbon compounds, the overlying aquifer is characterized and background values for key parameters are established. During the injection and post-injection phases of the project, there is periodic monitoring of the groundwater parameters, which they anticipate will be compared to the established background. When Statistically-Significant Increases (SSIs) are found, an Alternate Source Demonstration (ASD) will have to be prepared that attributes the SSIs to the CSS operation or to some other source. By establishing a groundwater monitoring protocol that is specific to the site, sensitive to changes in the partial pressure of carbon dioxide, and relative insensitive to natural variability and hydrochemical facies changes, optimal and cost-effective groundwater protection can be implemented.

Kacey Garber is an experienced groundwater project manager for active and closed landfills, including routine groundwater monitoring and statistical analyses; reports and permit applications; designing sampling and analysis plans; special groundwater studies; and conducting groundwater well construction planning and design. She has also been involved in PFAS workgroups. Ms. Garber has a Master’s in Geoscience from the University of Iowa, and a BS in Geology from Illinois State University  Her field experience includes collecting groundwater, surface water, landfill leachate, industrial and municipal wastewater, and soil; oversight of groundwater monitoring well installation; logging and sampling soils for well-drilling operations; groundwater well maintenance and development; inspection of final landfill covers for post-closure care; and routine wetland monitoring and delineation activities.


Thursday, June 23 at 10:30 – 12:00 Class I UIC
Microbially Influenced Corrosion in Injection Wells: A Case Study in a Class I Well for Coal Combustion Residuals,” with Stephanie Hill. Stephanie will discuss microbially influenced corrosion (MIC) is known as a direct cause of mechanical integrity failure in injection wells. While premature failures of expendable components, such as casing and packers, are inconvenient and expensive, this is not the only reason to proactively address downhole biological issues. Stringent control and mitigation of biological activity are imperative to minimizing borehole fouling and subsequent plugging of an injection reservoir. If left untreated, a well’s long-term reservoir health and operational efficiency may be jeopardized.

This presentation will summarize a case study of MIC-related failure in a Class I injection well used for leachate disposal from a coal combustion residuals facility. The well failed to maintain internal mechanical integrity just six months after being commissioned. We’ll walk through the investigation process, which includes annular pressure testing, downhole caliper logging, casing thickness detection, injection fluid analysis, and metallurgical analysis to identify the cause of failure. Following the replacement of the injection casing and packer, injection tests were conducted to assess the potential impacts of MIC on the reservoir’s ability to accept injected fluids. A proactive disinfection plan was customized based on the unique investigative results and implemented to prevent future MIC-related issues.

Stephanie HillStephanie Hill is a hydrogeologist, program leader for SCS Engineers’ Carbon Sequestration and Deep Well Injection practice, and licensed Professional Geologist. She earned a BS in Geosciences at the University of Texas, emphasizing hydrogeology and geomorphology. Stephanie’s early career focused on environmental compliance for mineral and fossil fuel industries at the Texas Commission on Environmental Quality (1996 to 2000) and the Railroad Commission of Texas (2000 to 2012). Currently, she leads a team of geologists and engineers to advise SCS clients of various industries on geologic storage options for carbon neutrality and disposal solutions for liquid residuals.





Posted by Diane Samuels at 6:00 am

January 14, 2019

Downhole scaling of organic compounds presents challenges in Class I disposal wells. Once chemical and physical conditions drive biological growth and mineral precipitation, the resulting downhole scale must be confronted with expensive workovers, stimulations, or even plugging and abandonment. In one Midwest case study, an electric utility is battling ferric, carbonate, and sulfate precipitate driven by fluctuating pH in its coal combustion residuals (CCR) leachate. Using a variety of geochemical models, we are taking a proactive approach to eliminate expensive fixes by simulating the saturation indices of key mineral species under defined parameters that drive the formation of downhole precipitate under temperature and pressure.

Using a variety of chemical equilibrium models such as PHREEQC, MINTEQ, WATEQ4F, and Geochemist’s Workbench, conceptual scenarios are run at the surface and in the mixing zone of the downhole reservoir using site-specific water-quality data, pressures, and temperatures. Each scenario provides anticipated mineral saturation states, used to estimate mass removal or chemical neutralization to prevent downhole precipitation. To mirror the dynamic nature of the CCR leachate water chemistry, modeling will continue as an iterative process whereby we will continue to collect data and run simulations to stay ahead of changes that could affect the downhole well chemistry.

This proactive approach will reduce the potential for downhole scaling to increase operational efficiency, reduce maintenance costs, and extend the life of this Class I well.

Meet Stephanie Hill and the SCS team at the Groundwater Protection Council’s 2019 Underground Injection Control conference. Tuesday, Feb. 26 from 10:30 a.m. – 12:00.


Stephanie Hill obtained a Bachelor of Science degree from the University of Texas at Austin in geological sciences with a focus on hydrogeology. She serves clients nationwide with the SCS Engineers team as a senior project manager and oversees the St. Louis area operations. Stephanie’s project experience includes hydrogeological evaluations, liquids management solutions, and Class I injection well permitting, design and operation.








Posted by Diane Samuels at 6:00 am