Webinar: Open-Loop Ground Source Heat Pumps – Hydrogeology & Modeling in Washington State
Tuesday, September 15, 2026
12:15 to 1:15 PM PT
An open-loop ground source heat pump (GSHP) system involves pumping groundwater from an aquifer through a heat exchanger and injecting the water back into the same aquifer. Pumping is done through an extraction well, and injection is done through a separate return well. The heat exchanger can either extract heat from the groundwater in the winter, or transfer heat to the groundwater in the summer. GSHP systems can be designed to operate at a campus or business park scale and provide an energy efficient heating and cooling option. In Washington State, GSHP systems have benefited from passage of the Climate Commitment Act targeting a 95% reduction in greenhouse gas emissions by 2050 with a focus on large emitting sources and industries. Grant funding has been available to assist with program implementation. Within this legislative backdrop, multiple university campuses have started the process of reducing greenhouse gas emissions through implementation of campus-wide GSHP systems. Completing the projects requires a multidisciplinary team of mechanical, electrical, water resource, planning, and administrative professionals. Permitting and design of the wellfield system is a critical component of a GSHP system. These groundwater-related technical aspects are addressed through the requirements of a non-consumptive water right permit issued by the Department of Ecology. The permit requires a demonstration of water availability and non-impairment. Water availability is demonstrated through aquifer characterization. Non-impairment is typically demonstrated through groundwater flow and heat transport modeling that predicts temperature impacts associated with long-term operation of the GSHP system. Modeling can be accomplished using the numerical groundwater flow modeling program MODFLOW to model hydraulic impacts and the contaminant transport model MT3DMS to model temperature impacts. We will demonstrate the permitting and technical requirements of implementing a GSHP system on a campus-wide scale through case studies of recent projects in alluvial and basalt aquifer systems.
Presenter:
Sarah Weeks
Hydrogeologist
Landau Associates
Sarah Weeks is a hydrogeologist with Landau Associates. She earned her B.S. in Geology from Western Washington University (2010) and her M.S. in Geology from Northern Arizona University (2016). Sarah has extensive experience in groundwater resources, hydrogeologic testing and analysis, well design, and contaminant fate and transport. After seven years in remediation at the Port of Tacoma, she rejoined Landau Associates, where she supports hydrogeologic evaluations, geothermal heat exchange projects, and water rights work.
Host:
Tom Mathis, PE, PH
Senior Environmental Engineer
Landau Associates
Tom Mathis, PE, PH, is a Senior Environmental Engineer with more than a decade of experience in hydrodynamics, hydrology, water quality, sediment transport, and environmental fate and transport modeling. His work spans complex water-resources and remediation projects, including major Superfund sites, reservoirs, floodplain studies, and groundwater–surface-water systems. He specializes in applying advanced computational modeling, data analysis, and practical engineering judgment to help clients understand complex environmental systems and make defensible decisions. Tom is a licensed Professional Engineer and Professional Hydrologist with an MSc in Hydrologic Sciences from the University of California, Davis.
Participation Details:
You will receive a link to participate via a Microsoft Teams meeting the day before and the day of the program.
Registration Fees:
Registration is free with a suggested donation of $10. We are non-profit, and your donation helps us provide events and programming. Thank you for supporting AWRA-WA!
Thank you to Greene Economics for sponsoring the event!
