Association of Environmental & Engineering Geologists CHICAGO CHAPTER
“Serving Professionals in Engineering, Environmental and Groundwater Geology Since 1957”
March 2017 AEG Dinner Meeting
LOCATION: Emmett’s Brewery, 5200 Main Street, Downers Grove, IL, (630) 434-8500
Groundwater Modeling of the Troy Bedrock Valley in DeKalb County, Illinois
Chris Greer, Ph.D., Groundwater Geologist, Fermi National Accelerator, Laboratory
WHEN: Monday, March 20, 2017, Cocktails @ 5:15 pm, Dinner @ 6:15 pm, Presentation following dinner
COST: $35 Members, $40 Non-Members, $15 Students and Professors, RSVP: By email As soon as possible, but no later than 5 PM Friday, March 10, 2017 email@example.com
PROGRAM SUMMARY: The western portion of DeKalb County, including the Troy Bedrock Valley, is a key recharge area into the regional Cambrian-Ordovician Aquifer that supplies drinking water to northeast Illinois. An extensive network of preglacial bedrock valleys was eroded into the bedrock surface of Illinois, creating the potential to focus recharge into bedrock aquifer systems along these valleys. A groundwater flow model of DeKalb County was developed to evaluate the role of the Troy Bedrock Valley in DeKalb County in recharge of the regional Cambrian-Ordovician Aquifer.
The conceptual model of groundwater flow in DeKalb County, based on previous studies, is that recharge into the Cambrian-Ordovician Aquifer in DeKalb County is mostly through the Troy Bedrock Valley. This numerical model of groundwater flow in DeKalb County tests the hypothesis of the conceptual model through calibration and verification to observed groundwater elevations. Calibration of the steady state model to 1959 conditions and verification of the transient model to groundwater elevations measured from 1960-2014 has increased the resolution and certainty of groundwater elevations in this portion of the Cambrian-Ordovician Aquifer recharge area as compared to regional modeling efforts.
The numerical model indicates that while the Troy Bedrock Valley serves to locally funnel recharge into the Cambrian-Ordovician Aquifer through the Upper Bedrock Aquifer, the Troy Bedrock Valley is not the predominant route of recharge in DeKalb County as hypothesized in the conceptual model. Simulated recharge is also distributed through a significant portion of the Galena-Platteville dolomite units outside of the Troy Bedrock Valley, both in the DeKalb-Sycamore heavy pumping center as well as areas underlain by the Maquoketa shale units.
Errors in the verification of 1960-2014 transient model, particularly in the vicinity of the DeKalb-Sycamore heavy pumping center, revealed limitations of the numerical representation of the conceptual model. Future improvements to the model calibration would allow further clarification of the recharge pathways into the Cambrian-Ordovician Aquifer in DeKalb County either primarily through the Troy Bedrock Valley or over a more diffuse area.
Chris Greer is a groundwater geologist in the Environmental Protection Group at Fermi National Accelerator Laboratory (Fermilab). His work at Fermilab draws on both his groundwater research and teaching in northern Illinois and his previous career as an environmental consultant. Chris worked for more than eight years as an environmental consultant, focusing on hydrogeologic field and modeling work across the United States. He earned his master’s degree in 1997 from Wright State University in Dayton, Ohio, developing a three-dimensional geostatistical model of the bi-modal heterogeneity within the White River buried valley aquifer beneath Indianapolis, Indiana. As part of his doctoral work at Northern Illinois University, Chris enjoyed learning about and educating students on the bedrock and glacial hydrostratigraphy of northern Illinois. The DeKalb County groundwater flow model was the major component of his doctoral research, but was complemented by a comparison of recharge estimation methods and an isotopic groundwater mixing analysis. Chris completed his doctoral degree in December 2016.