William Stansfield

Centredale Manor Superfund Site, North Providence, Rhode Island — Collected sediment samples for the characterization of dioxin-contaminated sediments using a variety of instruments, including a hand auger, piston sediment corer, and gas-powered hand probe. Samples were collected from wetlands, floodplains, and active stream channels associated with a Superfund site in Rhode Island.

Groundwater Sampling, Connecticut, Massachusetts, and Colorado — Sampled groundwater for water quality and a variety of constituents of concern from a variety of sites across several states using peristaltic pumps, bladder pumps, bailers, and passive diffusion bags.

Landfill Closures, Connecticut — Analyzed data related to long-term environmental monitoring programs associated with several Connecticut landfill closures. Updated quarterly and biannual reports for regulatory agencies with analysis and discussion of groundwater leachate chemistry.

Hydrologic Data Processing, Jacksonville, Florida — Processed groundwater elevation data collected by pressure transducers in a tidally influenced coastal aquifer. Developed a method for estimating the amplitude and phase of tidal oscillations in groundwater elevation in different wells. Results were used to understand the degree of tidal influence on different areas of the aquifer and the impact that tidal variability may have on contaminant transport.

Monitoring Well Design, Eastern Oregon — Designed two replacement monitoring wells at a large nitrate-impacted agricultural site in eastern Oregon. Prepared a technical memorandum with specific replacement monitoring well construction details, figures, and technical justification.

GIS Analysis, Bureau of Land Management, Oregon — Analyzed light detection and ranging (LiDAR) data to identify likely locations of headwater streams within the Cascade foothills to generate buffers around surface water features for timber harvesting. Ground-truthed suspected stream locations and collected field data using a handheld GPS. Digitized field-verified streams and other hydrologic features using field data and remote sensing data in ArcGIS Pro.

Numerical Modeling and Geochemical Evaluation of a Fresh–Brine Alluvial Aquifer, Altiplano, Argentina — Supported updates to a 3-dimensional flow and transport numerical model to optimize freshwater withdrawals from a fresh-brine alluvial aquifer. Prepared and reviewed geochemical diagrams and aquifer-scale water level trends to evaluate aquifer impacts due to withdrawals and alternate pumping scenarios. Evaluated changes in aquifer storage and provided recommendations for alternative consumption based on assessment results.

Contaminant Fate and Transport Numerical Modeling, Multiple Sites, Minnesota — Built and optimized groundwater flow and transport models for sites near the Mississippi River in Minnesota. Represented complex geology, including large offsets due to regional faulting, using Leapfrog and generated MODFLOW-USG input files using GMS and Groundwater Vistas. PFAS transport was simulated using the BCT package in MODFLOW-USG Transport. Models are used to evaluate and optimize hydraulic capture.

Numerical Modeling Investigation of Long-Term Hydrologic Change, Southern Peru — Applied numerical modeling techniques to assess the impact of mining-related groundwater extraction on a high-altitude headwater basin in the Peruvian Andes. Simulated surface water–groundwater interactions and evaluated the impact of pumping on freshwater resources and vegetation using a 3-dimensional, transient MODFLOW model.

Phase I Environmental Site Assessments, Multiple Sites, Connecticut — Performed multiple Phase I environmental site assessments on a variety of sites, including former manufacturing facilities, agricultural areas, dry cleaning facilities, and service stations in Connecticut.

Remediation Construction, Multiple Sites, New England — Performed construction oversight for the excavation of contaminated material and instillation of engineered controls, including impervious asphalt caps, sediment isolation sheet piles, retaining walls, and geotextiles, for a variety of sites in New England.

Sea Level Rise Modeling Assessment, San Francisco Bay Area, California — Evaluated a variety of modeling methods for estimating the impact of sea level rise (SLR) on coastal flooding due to SLR-driven increases in coastal groundwater levels. Approaches considered included simple GIS-based approaches and more complex numerical models. The evaluation was summarized in a technical memorandum that was used to inform the development of a numerical groundwater model for a region of the San Francisco Bay in California.

Injection Oversight, Denver, Colorado — Oversaw multiple subcontractors for a colloidal activated carbon injection event designed to immobilize PFAS in vadose zone soils. Responsibilities included monitoring injection pressures and volumes, serving as an onsite health and safety representative, and logging confirmation soil cores collected in the vicinity of injection locations to assess the radius of influence and injection effectiveness. Supervised the installation of confirmation monitoring wells used to evaluate injection effectiveness.

Natural Resource Damage Assessments, Multiple Sites, Maryland — Provided hydrogeological guidance for estimating the magnitude of natural resource damages associated with MTBE releases at approximately 50 individual focus sites throughout Maryland. Estimated the vulnerability of groundwater and nearby drinking water supply wells using site-specific conceptual site models. The analysis was performed using analytical contaminant fate and transport models and by reviewing documentation obtained through the discovery process at each focus site.

Discharge to Groundwater Permit by Rule, Gloucester County, New Jersey — Prepared an application for a discharge to groundwater permit by rule from New Jersey Department of Environmental Protection.