Denis R LeBlanc
Biography
Denis LeBlanc is a research hydrologist with the New England Water Science Center of the U.S. Geological Survey in Northborough, Mass. He 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.
He 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.
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...
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...
Assessment of Hydrologic Conditions 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...
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...
Poly- and Perfluoroalkyl 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.
New England WSC seminar series LeBlanc 20161207
The Cape Cod unconsolidated sand and gravel aquifer is pitted with more than 400
groundwater-flow-through kettle lakes. In groundwater-flow models of western and central
Cape Cod, about 25 percent of the total simulated recharge to the aquifer from precipitation
discharges into lakes and subsequently seeps back into the groundwater before discharging to
streams and the...
Public and private tapwater: Comparative analysis of contaminant exposure and potential risk, Cape Cod, Massachusetts, USA
BackgroundHumans are primary drivers of environmental contamination worldwide, including in drinking-water resources. In the United States (US), federal and state agencies regulate and monitor public-supply drinking water while private-supply monitoring is rare; the current lack of directly comparable information on contaminant-mixture exposures...
Bradley, Paul; LeBlanc, Denis R.; Romanok, Kristin; Smalling, Kelly; Focazio, Michael J.; Cardon, Mary C.; Clark, Jimmy; Conley, Justin M.; Evans, Nicola; Givens, Carrie E; Gray, James L.; Gray, L. Earl; Hartig, Phillip C.; Higgins, Christopher P.; Hladik, Michelle; Iwanowicz, Luke R.; Loftin, Keith; McCleskey, R. Blaine; McDonough, Carrie A.; Medlock-Kakaley, Elizabeth; Weis, Christopher P.; Wilson, Vickie S. Isolating the AFFF signature in coastal watersheds using oxidizable PFAS precursors and unexplained organofluorine
Water supplies for millions of U.S. individuals exceed maximum contaminant levels for per- and polyfluoroalkyl substances (PFAS). Contemporary and legacy use of aqueous film forming foams (AFFF) is a major contamination source. However, diverse PFAS sources are present within watersheds, making it difficult to isolate their predominant origins....
Ruyle, Bridger J; Pickard, Heidi M.; LeBlanc, Denis R.; Tokranov, Andrea K.; Thackray, Colin P.; Hu, Xindi C.; Vecitis, Chad D.; Sunderland, Elsie M. Characterizing the diverse hydrogeology underlying rivers and estuaries using new floating transient electromagnetic methodology
The hydrogeology below large surface water features such as rivers and estuaries is universally under-informed at the long reach to basin scales (tens of km+). This challenge inhibits the accurate modeling of fresh/saline groundwater interfaces and groundwater/surface water exchange patterns at management-relevant spatial extents. Here we...
Lane, John W.; Briggs, Martin; Maurya, PK; White, Eric A.; Pedersen, JB; Auken, Esben; Terry, Neil; Minsley, Burke J; Kress, Wade; LeBlanc, Denis R.; Adams, Ryan F.; Johnson, Carole D. Hillslope groundwater discharges provide localized ecosystem buffers from regional PFAS contamination in a gaining coastal stream
Emerging groundwater contaminants such as per- and polyfluoroalkyl substances (PFAS) may impact surface-water quality and groundwater-dependent ecosystems of gaining streams. Although complex near-surface hydrogeology of stream corridors challenges sampling efforts, recent advances in heat tracing of discharge zones enable efficient and informed...
Briggs, Martin A.; Tokranov, Andrea K.; Hull, Robert B.; LeBlanc, Denis R.; Haynes, A.; Lane, Jr., John W.
Simulated water-table and pond-level responses to proposed public water-supply withdrawals in the Hyannis Ponds Wildlife Management Area, Barnstable, Massachusetts
The glacial kettle ponds in the Hyannis Ponds Wildlife Management Area in Barnstable, Massachusetts, support a community of rare and endangered plants. The ponds are hydraulically connected to the unconfined aquifer that underlies Cape Cod. The plants are adapted to the rise and fall of water levels in the ponds as the water table fluctuates in...
LeBlanc, Denis R.; McCobb, Timothy D.; Barbaro, Jeffrey R.
Lithostratigraphic, geophysical, and hydrogeologic observations from a boring drilled to bedrock in glacial sediments near Nantucket Sound in East Falmouth, Massachusetts
In spring 2016, a 310-foot-deep boring (named MA–FSW 750) was drilled by the U.S. Geological Survey near Nantucket Sound in East Falmouth, Massachusetts, to investigate the hydrogeology of the southern coast of western Cape Cod. Few borings that are drilled to bedrock exist in the area, and the study area was selected to fill a gap between...
Hull, Robert B.; Johnson, Carole D.; Stone, Byron D.; LeBlanc, Denis R.; McCobb, Timothy D.; Phillips, Stephanie N.; Pappas , Katherine L. ; Lane, Jr., John W.
Hydrologic site assessment for passive treatment of groundwater nitrogen with permeable reactive barriers, Cape Cod, Massachusetts
Wastewater disposal associated with rapid population growth and development on Cape Cod, Massachusetts, during the past several decades has resulted in widespread contamination of groundwater with nitrogen. As a result, water quality in many of the streams, lakes, and coastal embayments on Cape Cod is impaired by excess nitrogen. To reduce...
Barbaro, Jeffrey R.; Belaval, Marcel; Truslow, Danna B.; LeBlanc, Denis R.; Cambareri, Thomas C.; Michaud, Scott C. Seasonal and spatial variation in the location and reactivity of a nitrate-contaminated groundwater discharge zone in a lakebed
Groundwater discharge delivering anthropogenic N from surrounding watersheds can impact lake nutrient budgets. However, upgradient groundwater processes and changing dynamics in N biogeochemistry at the groundwater-lake interface are complex and difficult to resolve. In this study, hydrograph variations in a groundwater flow-through lake...
Smith, Richard L.; Repert, Deborah A.; Stoliker, Deborah; Kent, Douglas B.; Song, Bongkeun; LeBlanc, Denis R.; McCobb, Timothy; Böhlke, John K.; Hyun, Sung Pil; Moon, Hee Sun
Geochemical conditions and nitrogen transport in nearshore groundwater and the subterranean estuary at a Cape Cod embayment, East Falmouth, Massachusetts, 2013–14
Nitrogen transport and transformation were studied during 2013 to 2014 by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, in a subterranean estuary beneath onshore locations on the Seacoast Shores peninsula, a residential area in Falmouth, Massachusetts, served by septic systems and cesspools, and adjacent...
Colman, John A.; LeBlanc, Denis R.; Böhlke, John K.; McCobb, Timothy D.; Kroeger, Kevin D.; Belaval, Marcel; Cambareri, Thomas C.; Pirolli, Gillian F.; Brooks, T. Wallace; Garren, Mary E.; Stover, Tobias B.; Keeley, Ann Evaluating long-term patterns of decreasing groundwater discharge through a lake-bottom permeable reactive barrier
Identifying and quantifying groundwater exchange is critical when considering contaminant fate and transport at the groundwater/surface-water interface. In this paper, areally distributed temperature and point seepage measurements are used to efficiently assess spatial and temporal groundwater discharge patterns through a glacial-kettle lakebed...
McCobb, Timothy D.; Briggs, Martin A.; LeBlanc, Denis R.; Day-Lewis, Frederick D.; Johnson, Carole D. Geochemical and hydrologic factors controlling subsurface transport of poly- and perfluoroalkyl substances, Cape Cod, Massachusetts
Growing evidence that certain poly- and perfluoroalkyl substances (PFASs) are associated with negative human health effects prompted the U.S. Environmental Protection Agency to issue lifetime drinking water health advisories for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in 2016. Given that groundwater is a major source of...
Weber, Andrea K.; Barber, Larry B.; LeBlanc, Denis R.; Sunderland, Elsie M.; Vecitis, Chad D. Microbial-sized, carboxylate-modified microspheres as surrogate tracers in a variety of subsurface environments: An overview
Since 1986, fluorescent carboxylate-modified polystyrene/latex microspheres (FCM) have been co-injected into aquifers along with conservative tracers and viruses, bacteria, and (or) protozoa. Use of FCM has resulted in new information about subsurface transport behaviors of microorganisms in fractured crystalline rock, karst limestone, soils, and...
Harvey, Ronald W.; Metge, David W.; LeBlanc, Denis R.
New Journal Article from Cape Cod Toxics Site Examines Fate of Groundwater Nitrogen Discharging to a Lake
On July 19, a new journal article from the Cape Cod Toxic Substances Hydrology team was published online in the Journal of Geophysical Research—Biogeosciences. New England WSC co-authors include Denis LeBlanc and Tim McCobb. The study was partly supported by the Korea Institute of Geoscience and Mineral Resources in Daejeon, South Korea.