Hydrogeology Experience - Darrel Dunn, Ph.D., PG

Table of Contents


Unaffiliated, Independent Hydrogeologist

Colorado Springs, Colorado, USA

Wyoming Registered Professional Geology License PG-679.

Email: ddunn@dunnhydrogeo.com. Inquiries are welcome.


Previous hydrogeology work experience includes:

  • Independent consulting hydrogeologist - geologist based in Colorado and Montana

  • Senior hydrogeologist for engineering and environmental firms based in Colorado and Pennsylvania

  • Senior hydrogeologist for a government water management and planning agency in Florida

  • University teaching and research in hydrogeology and geology at assistant and associate professor levels in Montana and Ohio

Performed hydrogeologic work in the following states and countries:

  • Colorado

  • Montana

  • New Mexico

  • Wyoming

  • Washington

  • California

  • Texas

  • Louisiana

  • Ohio

  • Pennsylvania

  • Florida

  • New York

  • Alberta, Canada

  • Tanzania, East Africa

To see geology (non-hydrologic) experience, press the button 🔳.


Red is states and provinces where I have worked. Dots are locations of offices where I have worked.


The following content shows types of hydrogeology work that I have done, with one or more examples for each type. The list not exhaustive and the examples are not all-inclusive.


Integrated Surface Water and Groundwater Modeling

  • Managed the development of an integrated surface water and groundwater model using the DHI (Danish Hydraulic Institute) Mike She and Mike 11 models and applied the integrated model to the operation of canal system control structures and municipal wellfields for water resource planning and management (Broward County, Florida).


Groundwater Modeling (Senior Groundwater Modeler)

    • Wrote computer code for a (finite-difference) model of a municipal wellfield with widely separated wells and calibrated it to wellfield data (Ph.D. Thesis).

    • Managed site-wide groundwater fate and transport modeling for the U.S. Department of Energy's Feed Material Production Center, Fernald, Ohio, using SWIFT III (Sandia Waste Isolation Flow Transport)

    • Performed quality assurance review of groundwater flow modeling (MODFLOW) for planning closure of a hazardous waste site (California).

    • Lead a peer review team in an evaluation of groundwater data and modeling used to support the DOE's Waste Isolation Pilot Plant (WIPP) Certificate of Compliance Application for radioactive nuclear waste disposal (New Mexico).

    • Performed groundwater flow modeling (MODFLOW/MODPATH) at Rocky Flats Plant, Golden, Colorado.

    • Developed a groundwater flow and contaminant transport model (MODFLOW/MT3D) of groundwater contamination by the solvent TCE (trichloroethylene) at Ft. Chaffee, Arkansas, for the U.S. Army Corps of Engineers. Simulated movement of contaminant plume to surface water. See MT3D TCE Model.

    • Supervised groundwater flow modeling in areas of contamination plumes at Edwards Air Force Base, California (MODFLOW).

    • Used my own finite-difference model to estimate groundwater inflow to a proposed open-pit coal mine (Wyoming).

    • Managed the development of a county wellfield protection model using MODFLOW and innovative Fortran code for groundwater capture zones (Broward County, Florida).

    • Performed site-wide analytical solute transport modeling at Hanford Superfund Site, Washington.

    • Investigated the use of UTCHEM to model DNAPL contamination of aquifers. See DNAPL Aquifer Contamination page.

    • Used an analytical element model to investigate water well interference in a subdivision. See Water Well Interference page.

    • Developed a MODFLOW model of groundwater flow in surficial sand and gravel and used MODPATH for particle tracking.

    • Taught graduate level course titled "Groundwater Modeling" at the University of Toledo, Ohio.


Watershed Hydrology

    • Performed comprehensive studies of representative mountain watershed hydrologic systems to support development of a watershed computer model (Montana).

    • Published paper titled "An Experiment in Deterministic Watershed Modeling": Water Resources Bulletin, 7.

    • Published paper titled "Hydrosim - Computerized Graphical Stream Hydrograph Simulation": report No. 22, Montana Joint Water Resources Research Center.

    • Taught graduate level course titled "Watershed Hydrology" at the University of Toledo, Ohio.

Water Well Testing

  • Tested an irrigation well at 1600 gpm, to estimate the potential yield of the well (Montana).

  • Tested groundwater exploration wells at Montana State Prison. Used step test procedures with inflatable packers to isolate aquifers.

  • Provided senior technical guidance and review for performing and analyzing pumping tests and tracer tests at a U.S. Department of Energy nuclear facility, Rocky Flats Plant, Golden, Colorado.

  • Pump tested surficial aquifer for residential subdivision central water supply (Missioula, Montana).

  • Pump tested new municipal water supply well to estimate effect of improper well construction (Montana.

  • Pump tested a water supply well in a fractured aquifer at a hospital. Used downhole flow meter to determine productive zones (Helena, Montana).

  • Step tested an industrial water supply well to determine well loss as part of a well rehabilitation project (Missoula, Montana).

  • Analyzed aquifer step test data for wells on Zanzibar, Tanzania, East Africa.

  • Designed web pages on step testing, water table aquifer testing, leaky aquifer testing, and fractured aquifer testing using modern computerized analysis.

Water Supply

    • Developed additional groundwater supply for Montana State Prison. Performed geologic investigation to select locations for test wells, supervised construction and testing using inflatable packers to isolate intervals, chose site for production well, wrote specifications for a large diameter production well using reverse rotary drilling, tested the well and selected pump size that would provide the needed water without pumping sand and silt or clogging. Others had failed to find and develop an additional groundwater supply at the Prison.

    • Performed numerous groundwater supply investigations for proposed real estate subdivisions, including water well drawdown calculations for safe yield and sustainability (Montana).

    • Wrote "Water Resources Report" for a Colorado Subdivision.

    • Performed a groundwater resource assessment for a Ranch in New Mexico.

Groundwater Quality

Groundwater Monitoring

  • Sampled domestic water wells in the vicinity of an oil well drilling site for groundwater contamination while the well was being drilled and reported the results (Gallatin County, Montana).

  • Designed a groundwater monitoring well system for a gold mine tailings site, step-tested the wells, and wrote a groundwater sampling protocol (Montana).

  • Supervised monitoring well construction staff at the Rocky Flats Superfund Site, Colorado.

Aquifer Safe Yield - Aquifer Depletion (Sustainability)

  • Supervised computer modeling to estimate safe yield of the Biscayne Aquifer in Broward County, Florida, without producing undesired effects on saltwater intrusion, wetlands, and Everglades Restoration.

  • Simulated aquifer depletion by proposed rural subdivisions (Montana).

Water Resources Management

    • Wrote the statement of work for development of the Integrated Water Resources Management Master Plan for Broward County, Florida. This was a $1 million contract involving a 25-year plan based on integrated surface water and groundwater modeling.

Groundwater Management

    • Utilized and integrated surface water and groundwater model to examine alternative operation of canal control structures to provide groundwater recharge to benefit municipal wellfields and reduce coastal saltwater intrusion in Broward County, Florida.

Water Resources Planning

    • Performed groundwater quality sampling and assessment to support areawide water resources planning for Gallatin County, Montana. See Montana Groundwater Gallatin Valley page.

    • Supervised the Groundwater and Surface Water Planning Section, Water Resources Division, Department of Environmental Protection, Broward County, Florida, for 11 years.

Saltwater Intrusion

    • Performed a three-dimensional mapping study of the historical progress of saltwater intrusion near a large municipal wellfield in Florida. See Saltwater Intrusion Pompano page.

    • Managed coastal saltwater intrusion monitoring and analysis for Broward County, Florida.

    • Managed saltwater intrusion modeling with SEAWAT (Broward County, Florida).

  • Investigated a claim that oil field enhanced recovery operations contaminated a drinking water well. Claim was settled to client's satisfaction (Wyoming).

  • Investigated contamination of water wells by Escherichia coli (Montana).

Water well construction

  • Investigated a claim that improper construction of municipal water well resulted in reduced yield of water, and testified in court. Used borehole imaging. (Montana)

Water logging of land

  • Investigated a claim that irrigation ditch maintenance practices were causing waterlogging of land due to water table mounding, and was deposed (Montana).

Water rights

  • Investigated the potential drawdown effects of operating an irrigation well on nearby irrigation wells and testified in court (Montana).

  • Investigated the potential depletion effect of operating an irrigation well on a nearby stream and testified at a water rights hearing (Montana).

  • Investigated the potential effects of operating a geothermal well, and testified at a water rights hearing (Montana).

  • Investigated the effects of upstream irrigation on senior downstream water rights (Montana).

  • Investigated whether upslope irrigation caused land slumping that endangered a motel, and testified in court (Montana).

  • Analysed the stability of slopes in numerous real estate subdivisions in Montana.

Mining effects

  • Investigated potential hydrologic effects of draining a subsurface gold mine (Montana).

Basement Flooding

  • Investigated basement flooding near irrigation ditches (Montana).


University Teaching - Hydrogeology

University of Toledo, Toledo, Ohio (Graduate level courses)

  • Groundwater hydrology

  • Groundwater modeling

  • Watershed hydrology

  • Hydrologic Measurements

Montana State University, Bozeman, Montana

  • Groundwater Hydrology

  • Advanced Hydrogeology