2007 Ground Water Summit


Monday, April 30, 2007
4:30 p.m. - 7:30 p.m.

Tuesday, May 1, 2007
9:30 a.m. - 1:30 p.m.

Tuesday, May 1, 2007
4:30 p.m. - 7:30 p.m.

Incorporating Secondary and Tertiary Porosity Features to Simulate a Karst Aquifer using MODFLOW

Louis F. Vittorio Jr., M.S., P.G., Matthew S. Weikel, M.S. and William Y. Potter, PG, EarthRes Group Inc.

Various approaches have been used to numerically simulate groundwater flow in fractured bedrock and karst aquifers.  Modeling methods in the literature include explicit discrete fracture, dual continuum, discrete fracture network, and single equivalent continuum methods.  A review of each of these methods and available numerical codes can be found in Diodato (1994).  The applicability of a given approach is dependent largely on the scale and the objective of the model in question.  As model scale increases, it becomes increasingly cumbersome to simulate fracture flow discretely, both computationally and in terms of data collection.  Concurrently, as model scale increases with respect to fractures, the aquifer approximates an equivalent porous medium (Neuman, 1987, Gerhart, 1984).

For the current project, extensive site characterization, the scale of the project and found aquifer features enabled development of a continuum porous flow numerical model to simulate a karst aquifer that included secondary porosity and a tertiary conduit system.  Secondary (fracture) porosity features were modeled as anisotropic high hydraulic conductivity zones.  The main tertiary porosity (conduit) feature was modeled using the MODFLOW drain package.  Model construction and calibration were supported by extensive site characterization, including installation of twenty-two monitoring wells and five exploratory borings, continuous water level monitoring, stream and spring flow gauging, hydrograph analysis, electrical resistivity surveying, and various aquifer hydraulic testing methods.  The results indicate that a calibrated MODFLOW model, using characterization-based approximations of secondary and tertiary porosity, can be used to accurately simulate measured drawdown effects due to pumping in a karst aquifer.

Louis F. Vittorio Jr., M.S., P.G., EarthRes Group Inc. Mr. Vittorio is the Vice President and Principal Hydrogeologist at ERG and has more than twenty-two years of experience in environmental consulting. He holds a BS Degree in Geology/Geophysics from the University of Pittsburgh and an MS Degree in Geology from Lehigh University. Mr. Vittorio is a registered Professional Geologist in Pennsylvania, a NJ Certified Subsurface Evaluator and is a member of the Pennsylvania Council of Professional Geologists, American Water Works Association and NGWA. Specialized project areas include water and mineral resource permitting, quarry dewatering analysis, fractured rock/karst aquifer system characterization, and groundwater flow and contaminant transport modeling.

Matthew S. Weikel, M.S., EarthRes Group Inc. Mr. Weikel is a Project Scientist at ERG and has 3 years of experience in environmental consulting. He holds BS and MS Degrees in Geology from Temple University. Mr. Weikel is a member of the Geological Society of America and the Environmental Engineering Geophysical Society. Specialized project areas include water and mineral resource permitting, quarry dewatering analysis, fractured rock/karst aquifer system characterization, and groundwater flow and contaminant transport modeling.

William Y. Potter, PG, EarthRes Group Inc. William Potter is a Senior Geologist and Project Manager at EarthRes Group, Inc. and has more than eighteen years of experience in environmental consulting and geophysical data processing. He holds a Degree in Geology from Ohio Wesleyan University. Mr. Potter is a registered Professional Geologist in Pennsylvania, a New Jersey Certified Subsurface Evaluator and is a member of the Pennsylvania Council of Professional Geologists. His areas of specialization include mineral resource permitting, quarry dewatering analysis, fractured rock/karst aquifer system characterization, and groundwater flow evaluation. Mr. Potter has also worked extensively in the solid waste industry and in conducting environmental investigation.


The 2007 Ground Water Summit