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Fred D Tillman, Jr., Ph.D.

Fred Tillman joined the USGS Arizona Water Science Center in Tucson, AZ in 2006 after two-plus years as a National Research Council (NRC) fellow with the USEPA Office of Research and Development (ORD) in Athens, Georgia. 

 Fred's current projects include investigating potential changes in groundwater recharge under projected climate change in the Colorado River basin and understanding the potential for uranium mining effects on regional water resources in the Grand Canyon area.

Prior to joining the USGS, Fred was a post-doctoral researcher with the Ecosystems Research Division of USEPA’s ORD from 2004 through mid-2006, working with Dr. James W. Weaver on issues related to soil vapor intrusion, particularly from leaking underground storage tanks.  Fred joined EPA after completion of his doctoral degree in Environmental Engineering at the University of Virginia in 2003, where he worked with Dr. James A. Smith on the response of volatile organic compound (VOC) vapors in the unsaturated zone to natural barometric pressure fluctuations (barometric pumping).

Education and Certifications

  • Ph.D. 2003, Environmental Engineering, University of Virginia, Charlottesville, VA

  • M.S. 1998, Environmental Engineering, University of Virginia, Charlottesville, VA

  • B.S. 1990, Electrical Engineering, Florida State University, Tallahassee, FL

Science and Products

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Salt Wash in the San Rafael Swell with white surface salts

Salinity

Studies of Sources and Transport of Dissolved Solids (Salt) in the Colorado River Basin using the Spatially Referenced Regressions on Watershed Attributes (SPARROW) Model The Upper Colorado River Basin (UCRB) encompasses about 112,000 mi2 and discharges more than 6 million tons of dissolved solids (salt) annually to the lower Colorado River Basin. It has been estimated that between 32 and 45...
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Utah Water Science Center
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Salinity

Studies of Sources and Transport of Dissolved Solids (Salt) in the Colorado River Basin using the Spatially Referenced Regressions on Watershed Attributes (SPARROW) Model The Upper Colorado River Basin (UCRB) encompasses about 112,000 mi2 and discharges more than 6 million tons of dissolved solids (salt) annually to the lower Colorado River Basin. It has been estimated that between 32 and 45...
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Colored map showing Colorado River Basin watersheds

Baseflow

The Colorado River has been identified as the most overallocated river in the world. Considering predicted future imbalances between water supply and demand and the growing recognition that base flow (a proxy for groundwater discharge to streams) is critical for sustaining flow in streams and rivers, there is a need to develop methods to better quantify present-day base flow across large regions...
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Utah Water Science Center
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Baseflow

The Colorado River has been identified as the most overallocated river in the world. Considering predicted future imbalances between water supply and demand and the growing recognition that base flow (a proxy for groundwater discharge to streams) is critical for sustaining flow in streams and rivers, there is a need to develop methods to better quantify present-day base flow across large regions...
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Air Force Plant 44 Samping

Air Force Plant 44

Industrial activity at Air Force Plant 44 (AFP 44), a manufacturing facility located on property owned by the U.S. Air Force and operated by a major defense contractor, resulted in extensive contamination of groundwater with the industrial solvent trichloroethylene (TCE) and other organic compounds. The sole-source regional aquifer underlying AFP 44 provides potable water for municipal, commercial...
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Arizona Water Science Center
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Air Force Plant 44

Industrial activity at Air Force Plant 44 (AFP 44), a manufacturing facility located on property owned by the U.S. Air Force and operated by a major defense contractor, resulted in extensive contamination of groundwater with the industrial solvent trichloroethylene (TCE) and other organic compounds. The sole-source regional aquifer underlying AFP 44 provides potable water for municipal, commercial...
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Water Quality Data from Select Spring and Stream Sites and Water and Sediment Quality Data from Major Tributaries of the Colorado River in Grand Canyon, Northern Arizona

This USGS Data Release represents water and sediment quality data collected in the Grand Canyon region of northern Arizona. There are 3 separate datasets associated with this Data Release: Water and sediment quality data from major Colorado River tributary monitoring sites in and near Grand Canyon from 2015 through 2019. Water quality results from spring and stream sites in Grand Canyon that w
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Ecosystems Mission Area, Contaminant Biology, Environmental Health Program, Environments Program (unpublished), Toxic Substances Hydrology, Arizona Water Science Center

Soil-Water Balance Groundwater Infiltration Model Results for the Lower Colorado River Basin

This USGS Data Release represents Soil-Water Balance (SWB) groundwater infiltration modeling results for the Lower Colorado River Basin (LCRB). The data release was produced in compliance with 'open data' requirements as a way to make the scientific data associated with USGS research efforts and publications available to the public. There are 3 separate datasets associated with this Data Release
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Arizona Water Science Center

Supplemental Discrete Dissolved-Solids Data and Monthly Mean Dissolved-Solids Data for Lower Colorado River (1928-2016)

Monthly Mean Dissolved-Solids Concentration and Monthly Mean Dissolved-Solids Load Data Flow weighted monthly mean dissolved-solids concentrations (mg/L) data and monthly mean dissolved-solids load data from 1928-2016 were computed by USGS using raw data from the Bureau of Reclamation. These data were computed by USGS for all of the seven sites (listed below). Colorado River above Imperial Dam,
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Arizona Water Science Center

Concentration and trend of 1,4-dioxane in wells sampled during 2002–2017 in the vicinity of the Tucson International Airport Area Superfund Site, Arizona

Industrial activities causing extensive groundwater contamination led to the listing of the Tucson International Airport Area (TIAA) as a Superfund Site in 1983. Early groundwater investigations identified volatile organic compounds (VOCs), including the chlorinated solvents trichloroethylene (TCE) and perchloroethylene (PCE), in wells in the area. Several responsible parties were identified and c
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Water Resources Mission Area, Arizona Water Science Center

Concentration of 1,4-Dioxane in Wells Sampled During 2002-2009 in the Vicinity of the Tucson International Airport Area Superfund Site, Arizona

Extensive groundwater contamination resulting from industrial activities led to the listing of the Tucson International Airport Area as a Superfund Site in 1983. Early investigations revealed elevated levels of volatile organic compounds (VOCs) including the chlorinated solvents trichloroethylene (TCE) and perchloroethylene (PCE) in wells in the area. Several responsible parties were identified an
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Water Resources Mission Area, Arizona Water Science Center
Photo of Havasu waterfall dropping into a light blue pool of water.
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Image: Processing Water-Quality Samples
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Image: View from Sowats Point
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Filter Total Items: 37

A review of current capabilities and science gaps in water supply data, modeling, and trends for water availability assessments in the Upper Colorado River Basin

The Colorado River is a critical water resource in the southwestern United States, supplying drinking water for 40 million people in the region and water for irrigation of 2.2 million hectares of land. Extended drought in the Upper Colorado River Basin (UCOL) and the prospect of a warmer climate in the future pose water availability challenges for those charged with managing the river. Limited wat
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Ecosystems Mission Area, Water Resources Mission Area, Arizona Water Science Center, Southwest Biological Science Center, Utah Water Science Center

An assessment of uranium in groundwater in the Grand Canyon region

The Grand Canyon region in northern Arizona is a home or sacred place of origin for many Native Americans and is visited by over 6 million tourists each year. Most communities in the area depend upon groundwater for all water uses. Some of the highest-grade uranium ore in the United States also is found in the Grand Canyon region. A withdrawal of over 1 million acres of Federal land in the Gran
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Ecosystems Mission Area, Water Resources Mission Area, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology, Arizona Water Science Center, New Mexico Water Science Center

Recent and projected precipitation and temperature changes in the Grand Canyon area with implications for groundwater resources

Groundwater is a critical resource in the Grand Canyon region, supplying nearly all water needs for residents and millions of visitors. Additionally, groundwater discharging at hundreds of spring locations in and near Grand Canyon supports important ecosystems in this mostly arid environment. The security of groundwater supplies is of critical importance for both people and ecosystems in the regio
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Water Resources Mission Area, Arizona Water Science Center

Trends in recent historical and projected climate data for the Colorado River Basin and potential effects on groundwater availability

Understanding recent historical and projected trends in precipitation and temperature in the Colorado River Basin, and estimating what the projected changes in these climate parameters may mean for groundwater resources in the region, is important for water managers and policymakers to sustainably manage water resources in the basin. Historical (1896–2019) precipitation and temperature data for th
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Water Resources Mission Area, Arizona Water Science Center

Assessing uranium and select trace elements associated with breccia pipe uranium deposits in the Colorado River and main tributaries in Grand Canyon, USA

Assessing chemical loading from streams in remote, difficult-to-access watersheds is challenging. The Grand Canyon area in northern Arizona, an international tourist destination and sacred place for many Native Americans, is characterized by broad plateaus divided by canyons as much as two-thousand meters deep and hosts some of the highest-grade uranium deposits in the U.S. From 2015–2018 major su
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Ecosystems Mission Area, Water Resources Mission Area, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology, Arizona Water Science Center, Geology, Geophysics, and Geochemistry Science Center

Geochemical characterization of groundwater evolution south of Grand Canyon, Arizona (USA)

Better characterization of the geochemical evolution of groundwater south of Grand Canyon, Arizona (USA), is needed to understand natural conditions and assess potential effects from breccia-pipe uranium mining in the region. Geochemical signatures of groundwater at 28 sampling locations were evaluated; baseline concentrations for select trace elements (As, B, Ba, Cr, Li, Mo, Rb, Se, Sr, Th, Tl, U
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Water Resources Mission Area, Arizona Water Science Center, Utah Water Science Center

Investigation of recent decadal-scale cyclical fluctuations in salinity in the lower Colorado river

Beginning in the late 1970s, 10- to 15-year cyclical oscillations in salinity were observed at lower Colorado River monitoring sites, moving upstream from the international border with Mexico, above Imperial Dam, below Hoover Dam, and at Lees Ferry. The cause of these cyclical trends in salinity was unknown. These salinity cycles complicate the U.S. Bureau of Reclamation's (Reclamation) responsibi
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Water Resources Mission Area, Arizona Water Science Center

Effect of spatial and temporal scale on simulated groundwater recharge investigations

Hydrologic model input datasets such as climate, land use, elevation, soil, and geology information are available in a range of scales for use in water resources investigations. Smaller spatial and temporal scale input data allow groundwater recharge models to simulate more physically realistic processes and presumably result in more accurate estimates of groundwater recharge. Projected climate da
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Water Resources Mission Area, Arizona Water Science Center

Managing salinity in Upper Colorado River Basin streams: Selecting catchments for sediment control efforts using watershed characteristics and random forests models

Elevated concentrations of dissolved-solids (salinity) including calcium, sodium, sulfate, and chloride, among others, in the Colorado River cause substantial problems for its water users. Previous efforts to reduce dissolved solids in upper Colorado River basin (UCRB) streams often focused on reducing suspended-sediment transport to streams, but few studies have investigated the relationship betw
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Water Resources Mission Area, Arizona Water Science Center

Changes in projected spatial and seasonal groundwater recharge in the upper Colorado River Basin

The Colorado River is an important source of water in the western United States, supplying the needs of more than 38 million people in the United States and Mexico. Groundwater discharge to streams has been shown to be a critical component of streamflow in the Upper Colorado River Basin (UCRB), particularly during low-flow periods. Understanding impacts on groundwater in the basin from projected cli
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Water Resources Mission Area, Arizona Water Science Center

Geochemical characterization of groundwater discharging from springs north of the Grand Canyon, Arizona, 2009–2016

A geochemical study was conducted on 37 springs discharging from the Toroweap Formation, Coconino Sandstone, Hermit Formation, Supai Group, and Redwall Limestone north of the Grand Canyon near areas of breccia-pipe uranium mining. Baseline concentrations were established for the elements As, B, Li, Se, SiO2, Sr, Tl, U, and V. Three springs exceeded U.S. Environmental Protection Agency drinking wat
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Water Resources Mission Area, Contaminant Biology, Environmental Health Program, Toxic Substances Hydrology, Arizona Water Science Center

Geochemistry and hydrology of perched groundwater springs: assessing elevated uranium concentrations at Pigeon Spring relative to nearby Pigeon Mine, Arizona (USA)

The processes that affect water chemistry as the water flows from recharge areas through breccia-pipe uranium deposits in the Grand Canyon region of the southwestern United States are not well understood. Pigeon Spring had elevated uranium in 1982 (44 μg/L), compared to other perched springs (2.7–18 μg/L), prior to mining operations at the nearby Pigeon Mine. Perched groundwater springs in an area
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Water Resources Mission Area, Ecosystems Mission Area, Toxic Substances Hydrology, Environmental Health Program, Arizona Water Science Center

Non-USGS Publications**

Tillman, F.D and Weaver, J.W., 2007, Parameter sets for upper and lower bounds on soil-to-indoor-air contaminant attenuation predicted by the Johnson and Ettinger vapor intrusion model.  Atmospheric Environment, 41, no. 27, p. 5797–5806.
Tillman, F.D and Weaver, J.W., 2007, Temporal moisture content variability beneath and external to a building and the potential effects on vapor intrusion risk assessment.  Science of the Total Environment, 379, no. 1, p. 1-15.
Tillman, F.D and Weaver, J.W., 2006, Uncertainty from synergistic effects of multiple parameters in the Johnson and Ettinger (1991) vapor intrusion model.  Atmospheric Environment, 40, no. 22, p. 4098–4112.
Tillman, F.D and Weaver, J.W., 2005, Review of recent research on vapor intrusion.  U.S. Environmental Protection Agency Publication No. EPA/600/R-05/106, 40 p.
Weaver, J.W. and Tillman, F.D, 2005, Uncertainty and the Johnson-Ettinger model for vapor intrusion calculations.  U.S. Environmental Protection Agency Publication No. EPA/600/R-05/110, 43 p.
Tillman, F.D and Smith, J.A., 2005, Vapor transport in the unsaturated zone, in Lehr, J.H., and Keely, J., eds., Water Encyclopedia: Ground Water. New Jersey, John Wiley & Sons, p. 543–548
Tillman, F.D and Smith, J.A., 2005, Site characteristics controlling airflow in the shallow unsaturated zone at Picatinny Arsenal, NJ.  Environmental Engineering Science, 22, no. 1, p. 25–37.
Tillman, F.D, Bartelt-Hunt, S.L., Craver, V.A, Smith, J.A., and Alther, G.R., 2005, Relative metal ion sorption on natural and engineered sorbents:  Batch and column studies.  Environmental Engineering Science, 22. no. 3, p. 400–410.
Alther, G.R., Tillman, F.D, and Smith, J.A., 2005, Evaluation of Two Organoclays, Clinoptilolite, and Hydroxy-Apatite as Sorbents for Heavy Metal Removal from Water, in Calabrese E.J., Kostecki P.T., Dragun J. (eds) Contaminated Soils, Sediments and Water. Springer, Boston, MA, p. 457–468.
Tillman, F.D, Bartelt-Hunt, S.L., Smith, J.A., and Alther, G.R., 2004, Evaluation of an organoclay, an organoclay-anthracite blend, clinoptilolite, and hydroxy-apatite as sorbents for heavy metal removal from water.  Bulletin of Environmental Contamination and Toxicology, 72, no. 6, p. 1134–1141.
Tillman, F.D and Smith, J.A., 2004, Design and laboratory testing of a chamber device to measure total flux of volatile organic compounds from the unsaturated zone under natural conditions.  Journal of Contaminant Hydrology, 75, no. 1-2, p. 71–94.
Tillman, F.D, Choi, J.-W., and Smith, J.A., 2003, A comparison of direct measurement and model simulation of total flux of volatile organic compounds from the subsurface to the atmosphere under natural field conditions.  Water Resources Research, 39, no. 10, p. 1284–1294.
Choi, J.-W., Tillman, F.D, and Smith, J.A, 2002, Relative Importance of Gas-Phase Diffusive and Advective Trichloroethene (TCE) Fluxes in the Unsaturated Zone under Natural Conditions.  Environmental Science and Technology, 36, no. 14, p. 3157–3164.
Olson, M.S., Tillman, F.D, Choi, J.-W., and Smith, J.A., 2001, Comparison of three techniques to measure unsaturated-zone air permeability at Picatinny Arsenal, New Jersey.  Journal of Contaminant Hydrology, 53, no. 1-2, p. 1–19.
Tillman, F.D, Choi, J.-W., Katchmark, W., Smith, J. A., and Wood, H.G.III, 2001, Unsaturated-zone airflow:  Implications for natural remediation of ground water by contaminant transport through the subsurface, in Smith, J.A., and Burns, S.E., eds., Physicochemical Groundwater Remediation.  New York, Kluwer Academic/Plenum Publishing, ISBN 978-0-306-46928-2, p. 307–340.

**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.

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Levels of Possible Human Carcinogen Declining in Most Wells in Tucson International Airport Superfund Site

Levels of a potential human carcinogen, 1,4-dioxane, have mostly declined in wells in the commercial and residential areas of the Tucson International...

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Groundwater Recharge in Upper Colorado River Basin May Hold Steady Under Climate Change

Future groundwater replenishment in the Upper Colorado River Basin may benefit from projected increases in future basin-wide precipitation under...

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