Denis LeBlanc is a Research Hydrologist with the New England Water Science Center.
Denis presently coordinates a multidisciplinary research effort at the USGS Cape Cod Toxic Substances Hydrology Research site at the Joint Base Cape Cod (JBCC) near Falmouth, Mass. He also provides technical support to Air Force and Army National Guard environmental restoration programs at JBCC and participates in several projects with the U.S Environmental Protection Agency on nitrogen and other wastewater contaminants in Cape Cod's groundwater.
Denis received his B.S. in Hydrology from the University of New Hampshire and his M.S. in Civil and Environmental Engineering from the Massachusetts Institute of Technology. He is a member of the National Ground Water Association and the Geological Society of America, where he is a GSA Fellow. He has focused on Cape Cod's freshwater resources since joining the USGS in 1975.
Professional Experience
1975 - present, U.S. Geological Survey - Research Hydrologist
Education and Certifications
M.S. Civil and Environmental Engineering, Massachusetts Institute of Technology
B.S. Hydrology, University of New Hampshire
Science and Products
PFAS Transport, Exposure, and Effects
The team is determining the movement and behavior of per- and poly-fluoroalkyl substances (PFAS) from their sources in the environment, as they move through exposure pathways in ecosystems including watersheds and aquifers, their incorporation into food webs, and molecular to population scale effects on fish and wildlife. These studies are accomplished at a variety of spatial scales from regional...
Research on Per- and Polyfluoroalkyl Substances (PFAS) in the New England Water Science Center
Per- and polyfluoroalkyl substances (PFAS) are a diverse group of over 4,000 different compounds. Since the 1940s, PFAS have been manufactured and used around the globe, including in the United States. PFAS are resistant to chemical and thermal breakdown and impart stain and water-resistance properties, making them useful for a variety of commercial applications, but also persistent in the...
Large Fraction of Unidentified Organofluorine in a Coastal Watershed has Implications for River to Marine Ecosystems
A group of scientists investigated per- and polyfluoroalkyl substances (PFAS) in watersheds on Cape Cod and identified a unique signature for aqueous film forming foams (AFFF) from legacy firefighting and fire training. A combination of statistical modeling and laboratory measurements indicates that unidentified organofluorine constitutes a large fraction of PFAS in the river systems that...
Measurement and Modeling of Nitrogen Discharge to Cape Cod Rivers to Identify High-Priority Nitrogen Reduction Areas
In 2019 USGS and the U.S. Environmental Protection Agency (EPA) Region 1 initiated a study to measure spatial and temporal patterns of nitrogen loading in selected rivers on Cape Cod and then determine whether the measured patterns can be related to nitrogen source areas in the surrounding watersheds to prioritize nitrogen reduction efforts. Study results will improve understanding of nitrogen...
Hydrologic Monitoring in the Three Bays Watershed in Support of Nutrient Management Activities, Cape Cod, Massachusetts
In 2019 the USGS began a partnership with the U.S. Environmental Protection Agency (EPA) Office of Research and Development (ORD), EPA Region 1 Southeast New England Program for Coastal Watershed Restoration (SNEP), Barnstable Clean Water Coalition (BCWC), and other stakeholders to conduct hydrologic monitoring and assessment in support of multifaceted nutrient-management activities in the Three...
Assessment of Potential Effects of Water-Supply Withdrawals on Groundwater Levels near the Hyannis Ponds Complex, Barnstable, Massachusetts
The USGS, in cooperation with the Town of Barnstable and MassWildlife, is assessing the potential effects of new water-supply withdrawals on groundwater levels in the Hyannis Ponds Wildlife Management Area on Cape Cod. A groundwater-flow model is being used to simulate the effects of several possible withdrawal and wastewater-return flow scenarios developed by the Town of Barnstable and...
Hydrologic Site Assessment for Passive Treatment of Groundwater Nitrogen with Permeable Reactive Barriers, Cape Cod, Massachusetts
In 2019 USGS completed a study designed to develop and evaluate a phased site-assessment approach for determining the hydrologic suitability of sites being considered for permeable reactive barrier installation on Cape Cod. The approach provides a template for town officials and other stakeholders to follow when considering PRBs for passive treatment of nitrogen in groundwater on Cape Cod and...
USGS Publications on the Water Resources of Cape Cod and Southeastern Massachusetts
The U.S. Geological Survey (USGS) has been investigating groundwater and surface-water resources on Cape Cod for more than 50 years. Recent studies have focused on the sources of water to public-supply wells, ponds, streams, and coastal areas; transport and discharge of nitrogen and contaminants of emerging concern derived from domestic and municipal wastewater disposal; fate and transport of...
Per- and Polyfluoroalkyl Substances From Firefighting and Domestic Wastewater Remain in Groundwater for Decades
New study explores the persistence and transport of poly- and perfluoroalkyl substances (PFASs) that originated from both firefighting and domestic wastewater sources. Although the fire training area and wastewater facility were decommissioned over 20 years ago, both sites continue to be sources of PFASs to groundwater.
Science and Products
- Publications
- Science
PFAS Transport, Exposure, and Effects
The team is determining the movement and behavior of per- and poly-fluoroalkyl substances (PFAS) from their sources in the environment, as they move through exposure pathways in ecosystems including watersheds and aquifers, their incorporation into food webs, and molecular to population scale effects on fish and wildlife. These studies are accomplished at a variety of spatial scales from regional...Research on Per- and Polyfluoroalkyl Substances (PFAS) in the New England Water Science Center
Per- and polyfluoroalkyl substances (PFAS) are a diverse group of over 4,000 different compounds. Since the 1940s, PFAS have been manufactured and used around the globe, including in the United States. PFAS are resistant to chemical and thermal breakdown and impart stain and water-resistance properties, making them useful for a variety of commercial applications, but also persistent in the...Large Fraction of Unidentified Organofluorine in a Coastal Watershed has Implications for River to Marine Ecosystems
A group of scientists investigated per- and polyfluoroalkyl substances (PFAS) in watersheds on Cape Cod and identified a unique signature for aqueous film forming foams (AFFF) from legacy firefighting and fire training. A combination of statistical modeling and laboratory measurements indicates that unidentified organofluorine constitutes a large fraction of PFAS in the river systems that...Measurement and Modeling of Nitrogen Discharge to Cape Cod Rivers to Identify High-Priority Nitrogen Reduction Areas
In 2019 USGS and the U.S. Environmental Protection Agency (EPA) Region 1 initiated a study to measure spatial and temporal patterns of nitrogen loading in selected rivers on Cape Cod and then determine whether the measured patterns can be related to nitrogen source areas in the surrounding watersheds to prioritize nitrogen reduction efforts. Study results will improve understanding of nitrogen...Hydrologic Monitoring in the Three Bays Watershed in Support of Nutrient Management Activities, Cape Cod, Massachusetts
In 2019 the USGS began a partnership with the U.S. Environmental Protection Agency (EPA) Office of Research and Development (ORD), EPA Region 1 Southeast New England Program for Coastal Watershed Restoration (SNEP), Barnstable Clean Water Coalition (BCWC), and other stakeholders to conduct hydrologic monitoring and assessment in support of multifaceted nutrient-management activities in the Three...Assessment of Potential Effects of Water-Supply Withdrawals on Groundwater Levels near the Hyannis Ponds Complex, Barnstable, Massachusetts
The USGS, in cooperation with the Town of Barnstable and MassWildlife, is assessing the potential effects of new water-supply withdrawals on groundwater levels in the Hyannis Ponds Wildlife Management Area on Cape Cod. A groundwater-flow model is being used to simulate the effects of several possible withdrawal and wastewater-return flow scenarios developed by the Town of Barnstable and...Hydrologic Site Assessment for Passive Treatment of Groundwater Nitrogen with Permeable Reactive Barriers, Cape Cod, Massachusetts
In 2019 USGS completed a study designed to develop and evaluate a phased site-assessment approach for determining the hydrologic suitability of sites being considered for permeable reactive barrier installation on Cape Cod. The approach provides a template for town officials and other stakeholders to follow when considering PRBs for passive treatment of nitrogen in groundwater on Cape Cod and...USGS Publications on the Water Resources of Cape Cod and Southeastern Massachusetts
The U.S. Geological Survey (USGS) has been investigating groundwater and surface-water resources on Cape Cod for more than 50 years. Recent studies have focused on the sources of water to public-supply wells, ponds, streams, and coastal areas; transport and discharge of nitrogen and contaminants of emerging concern derived from domestic and municipal wastewater disposal; fate and transport of...Per- and Polyfluoroalkyl Substances From Firefighting and Domestic Wastewater Remain in Groundwater for Decades
New study explores the persistence and transport of poly- and perfluoroalkyl substances (PFASs) that originated from both firefighting and domestic wastewater sources. Although the fire training area and wastewater facility were decommissioned over 20 years ago, both sites continue to be sources of PFASs to groundwater. - Data
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