Environmental Engineer
Environmental Engineer


Dr. Catherine Yonkofski is a Research Scientist within the Earth Systems Science Division at Pacific Northwest National Laboratory. Her technical specialty is in the development and application of subsurface simulation codes for use in characterization and interpretation of complex flow systems, predictive fate and transport modeling, and optimization of engineered subsurface systems.

Dr. Yonkofski works on a rich portfolio of projects predominantly supporting missions of the DOE Office of Fossil Energy and Carbon Management (DOE-FECM) and the DOE Office of Environmental Management (DOE-EM). She has particular interests in geologic carbon sequestration, subsurface contaminant remediation, and groundwater resource management. 

At PNNL, Dr. Yonkofski works to advance her professional mission: assimilating cutting-edge subsurface science into transformative tools that support industry and provide technical insight to regulatory stakeholders. She has been recognized for leading development of the Designs for Risk Evaluation and Management (DREAM) tool, which is included in the DOE-FECM’s National Risk Assessment Partnership (NRAP) Toolset. The NRAP Toolset has been honored with an R&D100 Award and lauded for representing the most complete suite of models ever assembled to assess the geological integrity and environmental risk performance of CO2 storage sites related to potential fluid leakage and ground motion. 

Dr. Yonkofski is currently a co-lead of the DOE-FECM’s SMART Initiative Task 4.  The Science-informed Machine Learning for Accelerating Real-Time Decisions in Subsurface Applications (SMART) Initiative is a 10-year, multi-organizational effort with the goal of transforming interactions within the subsurface and significantly improving efficiency and effectiveness of field-scale carbon storage and unconventional oil and gas operations. 

Dr. Yonkofski is the code custodian for UNSAT-H 3.0, a computer code used to understand the movement of water, heat, and vapor in soils so more informed decisions can be made about land use, waste disposal, and climate change.

Research Interest

  • Numerical modeling of multiple-phase subsurface flow and transport
  • Geologic carbon sequestration
  • Fate and transport of environmental contaminants
  • Groundwater resource assessments
  • Subsurface energy resource engineering


  • PhD in Environmental Engineering and Science, Clemson University
  • MS in Environmental Engineering and Science, Clemson University
  • BS in Mathematical Sciences, Clemson University

Affiliations and Professional Service

  • National Ground Water Association Groundwater Modeling Advisory Panel
  • Washington Hydrogeology Symposium

Awards and Recognitions

  • R&D 100 Award (2017)
  • PNNL Outstanding Performance Award (2015, 2016)



  • Bacon D.H., C. Yonkofski, C.F. Brown, D.I. Demirkanli, and J.M. Whiting. 2019. "Risk-based Post Injection Site Care and Monitoring for Commercial-Scale Carbon Storage: Reevaluation of the FutureGen 2.0 Site using NRAP-Open-IAM and DREAM." International Journal of Greenhouse Gas Control 90. PNNL-SA-140302. doi:10.1016/j.ijggc.2019.102784
  • White M.D., C. Yonkofski, J.A. Horner, and H.T. Schaef. 2019. Final Report for DOE NETL Gas Hydrate Project FWP 65213. PNNL-28462. Richland, WA: Pacific Northwest National Laboratory. 
  • Yonkofski C., D. Appriou, and J.L. Downs. 2019. Dust Control Planning. PNNL-29152. Richland, WA: Pacific Northwest National Laboratory. 
  • Yonkofski C., G.D. Tartakovsky, N.J. Huerta, and A.M. Wentworth. 2019. "Risk-Based Monitoring Designs for Detecting CO2 Leakage through Abandoned Wellbores: An application of NRAP's WLAT and DREAM tools." International Journal of Greenhouse Gas Control 91. PNNL-SA-140291. doi:10.1016/j.ijggc.2019.102807
  • Turner S., M.I. Hejazi, C. Yonkofski, S.H. Kim, and G.P. Kyle. 2019. "Influence of groundwater extraction costs and resource depletion limits on simulated global nonrenewable water withdrawals over the twenty-first century." Earth's Future 7, no. 2:123-135. PNNL-SA-129871. doi:10.1029/2018EF001105
  • Yonkofski C., and Z. Zhang. 2019. Hanford Surface Barrier Design Guidance. PNNL-29186. Richland, WA: Pacific Northwest National Laboratory.
  • Rockhold M.L., S.R. Waichler, J.L. Downs, X. He, J.D. Tagestad, Y. Fang, and V.L. Freedman, C. Yonkofski, et al. 2019. Information on Technical Impracticability for Remediation of Iodine-129 Contamination. PNNL-28057 Rev 1.0. Richland, WA: Pacific Northwest National Laboratory.



  • Loring J.S., D.H. Bacon, R.D. Springer, A. Anderko, S. Gopinath, C. Yonkofski, and C.J. Thompson, et al. 2017. "Water Solubility at Saturation for CO2-CH4 Mixtures at 323.2 K and 9.000 MPa." Journal of Chemical and Engineering Data 62, no. 5:1608-1614. PNNL-SA-122783. doi:10.1021/acs.jced.6b00999
  • Yonkofski C., C.L. Davidson, L.R. Rodriguez, E.A. Porter, S.R. Bender, and C.F. Brown. 2017. "Optimized, budget-constrained monitoring well placement using DREAM." Energy Procedia 114. PNNL-SA-121523. doi:10.1016/j.egypro.2017.03.1496
  • Rockhold M.L., C. Yonkofski, V.L. Freedman, and S.R. Waichler. 2017. Technical Basis for Remediation Endpoints: Status Report on the Development of the Iodine Technical Impracticability Waiver Request. PNNL-26925. Richland, WA: Pacific Northwest National Laboratory.


  • Yonkofski C., J.A. Horner, and M.D. White. 2016. "Experimental and Numerical Investigation of Hydrate-guest Molecule Exchange Kinetics." Marine and Petroleum Geology. PNNL-SA-115437. doi:10.1016/j.jngse.2016.03.080
  • Yonkofski C., J.A. Gastelum, E.A. Porter, L.R. Rodriguez, D.H. Bacon, and C.F. Brown. 2016. "An Optimization Approach to Design Monitoring Schemes for CO2 Leakage Detection." International Journal of Greenhouse Gas Control 47, no. 2019:233-239. PNNL-SA-110925. doi:10.1016/j.ijggc.2016.01.040
  • Yonkofski C., W. Xu, and T.P. Khangaonkar. 2016. Hydrogeologic Review of the Pelton Round Butte Hydroelectric Project Waterbodies and Potential Thermal Impacts of Groundwater Discharge. PNNL-25541. Richland, WA: Pacific Northwest National Laboratory.


  • Murdoch L., S. Xie, R.W. Falta, and C. Yonkofski. 2015. "Effects of Increased Upward Flux of Saline Water Caused by CO2 Storage or Other Factors." Journal of Hydrology 527. PNNL-SA-106621. doi:10.1016/j.jhydrol.2015.05.022
  • Bacon D.H., C. Yonkofski, H.T. Schaef, M.D. White, and B.P. McGrail. 2015. "CO2 Storage by Sorption on Organic Matter and Clay in Gas Shale." Journal of Unconventional Oil and Gas Resources 12. PNNL-SA-107851. doi:10.1016/j.juogr.2015.09.004