MMA Staff and Associates
Michael Mobile, PhD, CGWP
President and Senior Groundwater Hydrologist
B.S., Hydrology - University of New Hampshire
M.S., Environmental Engineering - Virginia Tech
Ph.D., Civil Engineering - Virginia Tech
Mike has nearly 20 years of experience in the areas of quantitative hydrogeology and hydrology, contaminant fate-and-transport assessment, and water resources management. His professional experience has included model development in support of several large-scale, high-profile construction activities, natural resource management projects, and litigation/conflict resolution assignments. The sensitive nature of much of this work has allowed Mike to explore a wide variety of innovative and interdisciplinary approaches to meeting client needs and addressing site-specific challenges.
Prior to joining MMA, Mike worked for GZA GeoEnvironmental, Inc., where he acted as an in-house expert on Per- and Polyfluoroalkyl Substances (PFAS) and the evolving regulatory environment surrounding these compounds. Between 2014 and 2018, he served as project manager of two New Hampshire site investigations primarily focused on PFAS while providing technical support to other PFAS-related projects, including sites in Michigan, Connecticut, and Massachusetts.
Scott Simpson, PhD
Managing Senior Hydrologist / Senior Groundwater Modeler
B.A., Environmental Science - University of Virginia
M.S., Hydrology and Water Resources - University of Arizona
Ph.D., Hydrology and Water Resources - University of Arizona
Scott has over 15 years of experience in quantitative hydrology and hydrogeology. He is a well-rounded surface water and groundwater hydrologist with a diverse skillset encompassing many modeling and other technical analysis capabilities relevant to surface water, groundwater, and water quality applications. His groundwater modeling experience has ranged in complexity from applying site-based analytical and numerical models to developing regional scale density-dependent flow and transport models. Scott has considerable experience and a keen interest in applying cutting-edge model optimization and uncertainty analysis techniques.
Prior to joining MMA, Scott worked at Tetra Tech as a senior hydrologist/groundwater modeler and project manager. His experience with Tetra Tech included leading many groundwater flow and solute transport modeling projects, developing efficient (and often application-specific) computational workflows, water balance and geochemical modeling, and other various technical analyses.
Daniel Morrissey, RPG
Associate Senior Groundwater Hydrologist
B.A., Biochemistry - Southern Connecticut State University
M.S., Hydrology - Univeristy of New Hampshire
Dan has more than 40 years of experience as a hydrogeologist and in the use of numerical simulation techniques for analysis of groundwater flow and transport problems. While with MMA, he has worked on numerous hydrogeologic investigations at sites located throughout the United States. Recent experiences include projects involving interstate water rights litigation, cost allocation evaluations at Superfund sites, and optimization of water supply systems. Dan has served as an expert witness in a variety of forums regarding groundwater issues and in the application of numerical simulation models to evaluate hydrogeologic problems.
Prior to founding MMA, Dan served as Chief of the New Hampshire/Vermont District of the Water Resources Division of the U. S. Geological Survey (USGS). As District Chief, he supervised a staff of 30 hydrologists and technicians and was responsible for data collection, hydrogeologic investigations, and quality control for all work completed by the office. He has conducted training courses in basic hydrology, surface geophysics, and ground-water flow simulation for the USGS, for the National Ground Water Association, state and local water management districts, and private clients in the United States and abroad.
Charles Spalding, PG
Associate Senior Groundwater Hydrologist
B.S., Geology - Virginia Tech
M.S., Hydrology - New Mexico Tech
Chuck has more than 30 years of experience in the conduct of quantitative hydrogeologic investigations. During this time, he has applied many numerical and analytical models for the characterization of groundwater flow and solute transport, and performed hydrogeologic investigation management.
Prior to joining MMA, Chuck worked for HSI-GeoTrans, Inc. and was project manager for numerous hydrogeologic investigation projects including groundwater flow and solute-transport modeling for groundwater resource, plume delineation, and remedial design, site characterization of hazardous waste sites, and water resource development. Additional responsibilities included administrative management of the Site Characterization Group in the Sterling, Virginia office of HSI-GeoTrans.
Chuck is experienced in a broad range of field tasks, including well drilling and installation, groundwater sampling, soil sampling, geophysical surveys, and aquifer tests.
David Ahlfeld, PhD, PE
Associate Senior Groundwater Hydrologist
B.S., Environmental Resource Engineering - Humboldt State University
M.A., Civil Engineering - Princeton University
Ph.D., Civil Engineering - Princeton University
David has over 35 years of experience in groundwater modeling and analysis. He holds a Ph.D. from Princeton University where he studied with Prof. George Pinder, one of the developers of the earliest numerical groundwater simulation codes. He has held faculty positions at the University of Connecticut and at the University of Massachusetts Amherst where he is now Professor Emeritus. During his 31 years in these faculty positions, David taught and conducted research in groundwater and many other aspects of water resources modeling and engineering. His primary focus area has been groundwater modeling and the associated use of optimization methods for design of water resource management systems. In addition to over 50 referred publications and a reference book on groundwater management modeling, David is lead author of GWM, the MODFLOW-coupled groundwater management code distributed by the USGS (click here for more information).
During his career, he has worked on numerous consulting projects including modeling in Woburn, MA, Tom’s River, NJ, the San Fernando Valley of California, the Tucson, AZ region, and the Republican River basin.
David Simon
Groundwater Hydrologist and Modeling Specialist
B.S., Biology - Salem State University
M.S., Hydrology - University of New Hampshire
David has been with MMA since 2018, during which he has been focused in the areas of quantitative hydrogeology/hydrology, GIS analysis, and database management. David’s areas of specialization include Python scripting for modeling support and statistical data analysis, aquifer recharge modeling, and numerical model calibration and uncertainty estimation using advanced automated techniques.
Prior to joining MMA, David completed his graduate studies in hydrology at the University of New Hampshire, where he worked as a research assistant and specialized in numerical hydrologic modeling. As a graduate student, David’s research was a part of the multi-institutional, inter-disciplinary Future of Dams project, where he presented and collaborated on model results with both colleagues and the public.
Riley Hollenberg
Staff Geologist
B.S., Environmental Geosciences - University of Minnesota
Riley joined MMA in 2023 after earning her bachelor’s degree in Environmental Geosciences from the University of Minnesota (UMN) Twin Cities in 2023. As an undergraduate student, she gained experience teaching geology labs and participating in geologic field courses in Montana, Western Norway, and Hawaii. Additionally, she served as V.P. for the student chapter of the Geological Society of Minnesota. Her undergraduate research at UMN consisted of a GIS-based project where she interpolated Little Ice Age paleo-glacial surfaces for glaciers around the perimeter of Greenland to compute ice mass changes to present conditions.