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Michael Sweetenham, P.G.

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Michael Sweetenham, P.G.
Consultant

Michael Sweetenham, P.G.

Consultant (720) 465-3322 Denver, CO msweetenham@integral-corp.com

Mr. Michael Sweetenham is a hydrogeologist with more than 10 years of experience in environmental assessment, investigation, characterization, modeling, remediation, and mining. His skill set combines the critical thinking ability and technical expertise of an analytical hydrogeologist with the computational skills of a modeler to develop conceptual site models (CSMs), 3-dimensional visualizations, and numerical groundwater models. He serves as a technical expert and works with multidisciplinary teams on small and large sites impacted with organic and inorganic constituents, including per- and polyfluoroalkyl substances (PFAS), 1,2,3-trichloropropane (1,2,3‑TCP), 1,4‑dioxane, chlorinated solvents, hydrocarbons, metals, and radionuclides. He has worked for industrial, commercial, municipal, and other clients under regulatory frameworks, including state-led cleanup programs, CERCLA, and RCRA.

Mr. Sweetenham has extensive field experience, including drilling oversight of direct push technology, hollow stem auger, sonic, air-rotary, and mud-rotary rigs to install monitoring, remediation, injection, and residential wells; collection of soil, sediment, rock, surface water, and groundwater samples; and use of high-resolution site characterization and geophysical methods to inform CSMs. He designs, implements, and manages successful projects involving in situ bioremediation (ISB)/‌bioaugmentation, in situ chemical oxidation (ISCO), pump and treat, phytoremediation, excavation, ex situ chemical oxidation, soil vapor extraction (SVE), sub-slab depressurization system (SSDS), and air sparging. In addition, Mr. Sweetenham is well versed with ArcGIS Pro, Leapfrog, and analytical and numerical models, including BIOSCREEN, BIOCHLOR, REMChlor, HELP, VS2DT, VLEACH, AnAqSim, ParFlow, MODFLOW, and MT3DMS.

Groundwater Modeling and Impact Assessment for Large-Scale Lithium Brine Operations in Northwestern Argentina

Case Study

December 20 2024

PFAS

Numerical Modeling and Remedial Evaluation of PFAS, Northeastern U.S. Served as lead groundwater modeler responsible for developing a 3-dimensional numerical flow model using MODFLOW to support remedy evaluation. Reviewed historical documents and regional USGS groundwater model to develop a groundwater CSM and establish model boundaries, stresses, and observations. Determined data needs and coordinated data collection with modeling team. Utilized Leapfrog model to develop representative grid honoring regional stratigraphy based on hundreds of borehole logs, geophysical data, and publicly available data. Developed a pneumatic slug testing standard operating procedure (SOP), coordinated large-scale aquifer testing event, evaluated data, and parameterized model hydraulic conductivity. Constructed groundwater model using GMS. Calibrated flow model to steady-state and transient conditions using a combination of manual and automated methods.  Extended model simulation period to incorporate historical aquifer stresses and potential future stresses.  Used MODPATH and MT3DMS to evaluate plume extents and capture to support remedial design.  
PFAS Site Investigation and Characterization, Confidential Location Managed site characterization activities to evaluate the nature and extent of PFAS impacts in sediment, soil, surface water, groundwater, and concrete related to aqueous film forming foam usage. Designed and oversaw a multichannel analysis of surface waves (MASW) geophysical survey to evaluate the presence of paleochannels and integrated results with stratigraphic units on borehole logs to prepare a 3-dimensional Leapfrog model and bedrock topography map. Designed and conducted non-contact falling head slug tests and constant-rate injection tests using a sonic water level meter and evaluated them using AQTESOLV. Combined aquifer testing results with the 3‑dimensional model outputs and depth-to-water measurements to calculate mass discharge of PFAS across various transects and theoretical concentrations at downgradient receptors. Oversaw a high-resolution site characterization (HRSC) event that included advancing a membrane interface hydraulic profiling tool, installing soil borings and temporary wells, and sampling of multimedia. HRSC corroborated the presence of paleochannels/depth to bedrock and aquifer properties calculated from the MASW and non-contact aquifer testing. Supported offsite investigation by securing access agreements, overseeing monitoring and stilling well installation, evaluating passive flux meter placement, and collecting soil and groundwater samples. Drafted predesign investigation sampling plan to support execution of successful excavation. Optimized routine monitoring by evaluating and selecting alternative groundwater sampling methods.
PFAS Site Investigation, Jackson, Wyoming Oversaw advancement of truck-mounted sonic drilling rig boreholes through alluvial deposits and installation of temporary monitoring wells adjacent to an active airport runway.  Logged continuous core and collected soil and groundwater samples following PFAS sampling protocol.  Discussed observations and advanced the CSM to support an evaluation of a proposed pump-and-treat system using MODFLOW.

Site Assessment

Union Pacific Railroad Facility, Kremmling, Colorado Oversaw monitoring well installation using a hollow stem auger rig to evaluate impacts related to a release of magnesium chloride from a railcar as part of the Voluntary Cleanup and Redevelopment Program.  Surveyed monitoring wells using a leveling rod and optical level.  Collected groundwater samples using low-flow methods and submitted samples for analysis of trace radionuclides.  Evaluated data, documented investigation, and attained site closure.
ASTM Phase I and Phase II Environmental Site Assessments (ESAs), Multiple Locations in Colorado, Kansas, and South Dakota Interviewed facility personnel, reviewed environmental database reports, and proposed soil boring and grab-groundwater locations.  Oversaw drilling using variety of drilling technologies, logged continuous core, screened soil using a photoionization detector (PID), collected soil samples, oversaw temporary well installation, collected groundwater samples, and submitted samples for laboratory analysis.  Documented field activities and results in Phase I/II ESA reports.

Fate and Transport

CSM Development and Fate and Transport Modeling, Cloquet, Minnesota Served as the technical lead in revising a CSM and predicting the maximum extent of groundwater impacts in relation to receptors. Oversaw HRSC using an ultraviolet optical screening tool (UVOST) to delineate a light nonaqueous-phase liquid (LNAPL) body containing a trace of cis‑1,2‑dichloroethene (cis-1,2-DCE), that appeared to be the source of a groundwater plume based on the calculated effective solubilities and observed concentrations. Generated a 3‑dimensional depiction of the horizontal and vertical extent of LNAPL using Leapfrog. Revised the simplified CSM based on the glacial depositional environment to differentiate between glacial till and outwash and incorporated the revised geological CSM into the Leapfrog model with the cis‑1,2‑DCE plume, which demonstrated that transport was occurring through outwash and the plume was in an early stage at the forefront. The LNAPL body was excavated and a grab groundwater investigation completed along the leading edge of the cis-1,2-DCE plume. Conducted slug tests in monitoring wells and calculated average linear groundwater velocities to calibrate a fate and transport model. Developed a simplified 2-dimensional, spreadsheet-based model that solved the advection-dispersion equation and accounted for retardation and decay; model was used to predict the downgradient extent of the cis-1,2-DCE concentrations above 0.006 ppm. Oversaw two rounds of grab-groundwater investigations, which confirmed the modeling results. Prepared technical reports and memoranda summarizing activities and results. Results suggested impacts would not reach receptors at concentrations above standards, groundwater monitoring was discontinued, site groundwater wells were plugged and abandoned, and the RCRA permit was closed.
Former New/Used Oil Branch Service Center, Los Alamitos, California Evaluated slug tests using AQTESOLV and used results to model transport and predict constituent concentrations at downgradient monitoring wells.  Calculated transport versus attenuation rates and reviewed remedial approaches.  Designed clean-water injection test to evaluate in situ remedy feasibility.  Proposed chemically oxidized granular activated carbon (GAC) injection for permeable reactive barrier to immobilize and remove chlorinated benzenes and ethenes.
CERCLA Superfund Site, Phoenix, Arizona Downloaded, reviewed, and digitized hundreds of borehole logs for a high-profile litigation project. Wrote a macro to efficiently process the logs in Excel for use in ArcGIS and Leapfrog to evaluate the sand/gravel percentages and presence/absence of a paleochannel. Developed groundwater elevation target files and reviewed aquifer-testing data in comparison to the grain size analysis completed using the macro to calibrate and parameterize a MODFLOW model. Reviewed aerial photography of nearby canal and developed canal conductance shapefile based on historical lining.
Used Oil Recycling Center, Denton, Texas Oversaw injection well installation using hollow stem auger, well development using bailing and surging, and sampling using low-flow techniques.  Led multiple successful ISB and bioaugmentation events targeting chlorinated ethenes.  Responsible for field fabricating injection equipment to optimize injection at individual wellheads and maximize total injection system throughput.  Evaluated plume migration using a 1-dimensional solution to the advection dispersion equation.  Calculated the plume total mass and center of mass for separate monitoring events by interpolating surfer grids and evaluated migration/degradation potential.
New/Used Oil Branch Service Center, St. Charles, Missouri Incorporated existing borehole data, total organic vapor, and trichloroethene (TCE) data into a Leapfrog model to advance the CSM.  Compared revised CSM to slug testing data and identified high-permeability mass transport zone.  Utilized revised CSM to evaluate remedial options and proposed ISB.
Used Oil Recycling Center, Manati, Puerto Rico Modeled 1,4-dioxane and vinyl chloride transport using REMChlor.  Evaluated borehole logs and prepared isopach grids for the primary high-permeability mass transport zones.  Coupled concentration grids with modeling outputs to calculate mass flux and discharge across multiple transects.  Calculated theoretical concentrations at nearby wells based on a range of possible pumping rates.
Salt Loading Calculations, Green River, Wyoming Evaluated slug testing data using AQTESOLV to calculate hydraulic conductivity of aquifer and resulting salt loading to nearby river.  Provided recommendations for salt loading mitigation.
Closed Refinery, Sunburst, Montana Calculated site-specific soil migration to groundwater (MTGW) standards for organic and inorganic constituents in exceedance of generic Montana Department of Environmental Quality (DEQ) standards.  Used the HELP model to calculate infiltration rates for use in the VS2DT model to support a risk assessment at a former refinery.  Compared results of the site-specific MTGW evaluation to generic Montana DEQ standards.  Suggested that site-specific standards were higher for some constituents in select areas and that they did not pose a risk to human health or the environment. Documented results in a memorandum to support the risk assessment and proposed no further remediation of those select areas.
Oil Refinery Landfill, Sinclair, Wyoming Developed MTGW spreadsheet using Wyoming DEQ guidance to evaluate potential impacts related to increased landfill permit limits for total petroleum hydrocarbon (TPH)-gasoline range organics and TPH-diesel range organics. Documented results in technical memorandum.
New/Used Oil Branch Service Center, Fresno, California Used VLEACH to model migration of soil impacts to groundwater to evaluate potential for groundwater impacts and need for deep groundwater wells.
Exploration and Production Exempt Landfill Liner Modification, Pawnee, Colorado Developed a cost-effective simplified approach to demonstrate a proposed landfill liner modification would not result in impacts to groundwater.  Liner modification was approved based on the approach.

Natural Resource Damage Assessment

Natural Resource Damage Assessment, Confidential Location Served as technical lead hydrogeologist to support a natural resource damage assessment and evaluate potential groundwater impacts resulting from volatile organic compound (VOC) releases at a historical facility. Reviewed regional and local groundwater models to evaluate water balance. Developed succinct transport CSM and calculated approximate size of source area to evaluate continuing impacts to groundwater.

Mining

Numerical Modeling and Geochemical Evaluation of a Fresh–Brine Alluvial Aquifer, 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 change in aquifer storage and provided recommendations for alternative consumption using results. Processed modeling results and documented numerical model. Evaluated placement of additional production well using model and reviewed proposed well construction.
Numerical Modeling of Water Resources and Surface Water Impacts in a Fresh–Brine Alluvial Aquifer, Argentina Served as lead groundwater modeler responsible for developing watershed-scale 3-dimensional geological and numerical models of a complex freshwater–brine system present in alluvial and volcanic deposits in the Altiplano-Puna region, Argentina. Compiled publicly available third-party geologic, geophysical, and analytical data with borehole logs into a 3-dimensional geological model using Leapfrog software. Used the geological model to update the CSM, establish model boundaries, and generate MODFLOW grid. Constructed numerical model using MODFLOW-USG and incorporated connected linear network and block centered transport with density driven flow. Iteratively calibrated model to steady-state water levels, streamflow, total dissolved solids, and transient water levels measured during aquifer testing using a combination of manual and automated methods. Evaluated effects on water levels, streamflow, and total dissolved solids under different potential pumping scenarios and provided recommendations, including implementation of a full-scale aquifer test. Documented construction, calibration, and predictions in numerical modeling report.
Resource and Reserve Disclosure for a Lithium Mine, Argentina Prepared the Securities and Exchange Commission (SEC) Regulation S-K Subpart 1300 compliant resource and reserve disclosure for a lithium mine in Argentina. Evaluated historical and current measured, indicated, and inferred resources using industry standard methodology for brine reservoir. Incorporated geophysical survey data to update a 3-dimensional geological reservoir model using Leapfrog. Created SEAWAT model grid using Leapfrog and supported numerical model development. Evaluated numerical model results and estimated proven and probable reserves. Calculated process efficiency. Documented results and recommended additional characterization. Converted SEC-compliant document into Australian Securities Exchange compliant foreign estimate for disclosure, and into Ontario Securities Commission-compliant document in accordance with National Instrument 43-101 guidance for mineral brine projects.
Numerical Modeling Support and Reporting for a Lithium Mine, Argentina Supported refinements and recalibration of a 3-dimensional flow and transport numerical model to provide guidance on sustainable brine pumping rates, predict future conditions, and provide assurance on best management practices for a lithium mine in Argentina. Documented hydrogeologic CSM, numerical model development, and predictive simulation results.
Geochemical Evaluation of an Artificial Lagoon, Argentina Project manager responsible for evaluating feasibility of spent brine management and disposal options at a lithium mine in Argentina. Managed and supported a team of hydrogeologists and geochemists to review operations data and evaluate the potential for pipe scaling, reduced porosity due to precipitate formation, and mass balance. Used operations data, aerial imagery, and geochemistry data to calculate lagoon mass balance and make management recommendations.

Groundwater Modeling

Numerical Modeling and Remedial Evaluation of Metals Impacted Groundwater, Confidential Location Served as lead groundwater modeler responsible for updating the CSM and numerical groundwater model for a site impacted with cadmium and zinc. Reviewed historical background investigation and modeling documents to revise the existing CSM using Leapfrog software. Prepared and updated 3-dimensional numerical flow model using a grid generated in Leapfrog and exported to MODFLOW. Calibrated the timing and magnitude of gross groundwater recharge rates with the HELP model using precipitation data and transducer data for inputs to the groundwater model. Calibrated groundwater model heads to water levels and fluxes to streams and utilities. Ran predictive simulations to evaluate remedial alternatives to the existing treatment. Prepared summary memorandum documenting results. Identified CSM data gaps required to constrain model and improve remedial design and designed successful site investigation. Updated transient model calibration using additional streamflow and hydraulic conductivity data collected during data gaps investigation. Extended model predictive simulation period to incorporate above- and below-average precipitation and evaluated effectiveness of remedial options under logistical constraints. Used model to evaluate well placement and recovery rates for 90 percent design.
Numerical Modeling and Remedial Evaluation of PFAS, Northeastern U.S. Served as lead groundwater modeler responsible for developing a 3-dimensional numerical flow model using MODFLOW to support remedy evaluation. Reviewed historical documents and regional USGS groundwater model to develop groundwater CSM and establish model boundaries, stresses, and observations. Determined data needs and coordinated data collection with modeling team. Wrote Python and Visual Basic scripts to efficiently download and process hundreds of pumping well records. Utilized Leapfrog model to develop representative grid honoring regional stratigraphy based on hundreds of borehole logs, geophysical data, and publicly available data. Developed pneumatic slug testing SOP, coordinated large-scale aquifer testing event, evaluated data, and parameterized model hydraulic conductivity. Constructed groundwater model using GMS. Calibrated flow model to steady-state and transient conditions using combination of manual and automated methods. Extended model simulation period to incorporate historical regional aquifer stresses and potential future stresses. Used MODPATH to evaluate advective transport and plume capture to support remedial design. Developed PFAS transport model using MT3DMS and calibrated to transient data for multiple species. Evaluating plume state, extent, and remedial options using transport model.
Numerical Modeling of Groundwater Withdrawals and Sustainability, Confidential Location Provided expert testimony support to evaluate impacts of groundwater withdrawals on groundwater levels and potential impacts to ecologically sensitive surface waterbodies. Served as lead groundwater modeler responsible for developing a hydrogeological CSM and 3‑dimensional numerical flow model using MODFLOW-USG. Reviewed publicly available data from the USGS and department of natural resources to develop watershed-scale CSM, preliminary water balance, and groundwater model objectives. Determined data needs and coordinated data collection with modeling team. Wrote Python and Visual Basic scripts to efficiently process large data sets for model input. Supported Leapfrog model development and generated representative grid honoring regional stratigraphy. Constructed groundwater model using GMS and incorporated lake and streamflow routing packages to simulate surface water-groundwater interactions in hundreds of lakes and multiple stream reaches. Calibrated flow model to transient conditions using combination of manual and automated methods. Used calibrated model to evaluate impacts to sensitive waterbodies and nearby monitoring/domestic wells without observation data. Predicted impacts under increased-stress scenario. Supported expert report preparation summarizing model results.
Litigation Support, PFAS Transport, Confidential Locations Provided expert testimony support to evaluate claims related to the occurrence and migration of PFAS in groundwater. Served as the lead groundwater modeler responsible for creating CSMs, and updating, refining, and/or recalibrating existing 3-dimensional numerical models developed by municipal and government entities to evaluate PFAS transport. Utilized models to simulate advective transport of PFAS using particle tracking and evaluated historical and future capture under a variety of pumping scenarios. Prepared expert report summarizing opinions formed from modeling results.  
Aquifer Storage and Recovery Feasibility Study, Confidential Location Supported a feasibility study of applying an existing 3-dimensional USGS-developed groundwater model for application on a proposed aquifer storage and recovery project. Reviewed regional and local hydrogeology documents, modeling input files, and conclusions in the modeling report. Provided recommendations on feasibility and path forward.
Former Pesticide and Fertilizer Distribution Facility, Confidential Location Served as technical lead and project manager for site investigation and routine monitoring and reporting. Supported the design of a groundwater extraction and treatment system for a large, dilute 1,2,3-TCP and nitrate groundwater plume. Evaluated pumping tests to confirm the well placement. Optimized design for plume capture in accordance with the treatment system design. Prepared and calibrated analytic element groundwater model using AnAqSim to evaluate system performance using particle tracking. Developed a 3-dimensional Leapfrog model using environmental sequence stratigraphy (ESS) and incorporated the 1,2,3-TCP concentrations to advance the CSM and evaluate the relationship between the hydrostratigraphy and plume. Monitored system that pumps 80 gallons per minute (gpm) through GAC and ion exchange vessels. Submitted National Pollutant Discharge Elimination System reports for discharge to a nearby lined canal. Oversaw deep well installation up to 500 ft below ground surface using truck-mounted sonic and mud-rotary rigs.
CERCLA Superfund Site, Confidential Location Prepared 3-dimensional hydrostratigraphic model and cross sections in Leapfrog using principles of ESS. Demonstrated to EPA that an aquitard present at depth was preventing downward migration of constituents into nearby replacement residential drinking water wells.
Numerical Modeling of a Chlorinated Solvent Plume, Central Valley, California Reviewed site background and modeling documents and evaluated options for existing model optimization. Supported model optimization by evaluating existing aquifer testing data and comparing to modeled hydraulic conductivity, updating recharge based on land use data, incorporating new stresses, and updating boundary conditions. Documented optimization in modeling report.
Municipal Solid Waste Landfill, Missoula, Montana Fabricated air sparging manifold and designed field implementation. Developed air sparging mass calculation tracking spreadsheet to evaluate air sparging effectiveness. Reviewed groundwater concentration data and trends, developed and calibrated 2-dimensional spreadsheet-based groundwater model, and presented results to Montana DEQ to support the successful remedy transition to monitored natural attenuation. Documented results in routine reports and technical memoranda.
Regional Potentiometric Surface Mapping, Confidential Location Evaluated and combined potentiometric surface maps from different dates at multiple sites into generalized regional potentiometric surface.

Groundwater Remediation

Solar-Powered ISB and Groundwater Extraction/Phytoremediation, Norfolk, Nebraska Served as the assistant project manager and lead hydrogeologist responsible for the monitoring and remediation program of a large, dilute, and commingled chlorinated solvent and 1,4-dioxane plume at a former municipal solid waste landfill. Conducted routine groundwater monitoring and landfill gas monitoring events. Repurposed an existing solar-powered groundwater extraction system (GWES) as an ISB system for treatment of the chlorinated solvent plume. Extracted groundwater from downgradient wells, mixed with emulsified vegetable oil, and reinjected at upgradient wells using solar-powered submersible pumps for ISB. Added bioaugmentation culture at select injection wells. Prepared a 3-dimensional Leapfrog model using the principles of ESS and incorporated the 1,4-dioxane groundwater plume to revise the CSM. Used the revised CSM and a basic MODFLOW model to evaluate capture and support a mass flux/discharge evaluation, which suggested new groundwater extraction wells were required for the downgradient 1,4-dioxane plume. Oversaw extraction well installation using a hollow stem auger rig and conducted constant rate pumping tests, which were evaluated in AQTESOLV to optimize pump size and extraction rates. Received approval to reinject impacted water in the subsurface within the plume source area and irrigate a phytoremediation tree stand under the existing underground injection control permit. Designed, wired, plumbed, and installed the repurposed GWES as a phytoremediation system for the treatment of 1,4-dioxane and chlorinated VOCs. The expanded system has the capacity to pump approximately 50 gpm of impacted groundwater through dual-contained, single-walled, high-density polyethylene pipe manifolded to subsurface irrigation drip tape and irrigate approximately 3,000 trees. Target chlorinated ethenes have been reduced from concentrations near parts per million (ppm) to below detection limits within the ISB treatment area and the modified GWES is successfully capturing downgradient groundwater impacts and preventing migration toward offsite private drinking water wells. Prepared routine reports and non-routine work plans.
Third-Party Review of Groundwater Extraction and Containment Systems, Mobile, Alabama Provided third-party review of modeling, design, and construction of a GWES built to contain and dewater impacts related to a landfill, and the contingency system designed to provide supplemental containment. Reviewed historical and current aquifer performance data with respect to assumptions used in HELP and MODFLOW numerical modeling files and well construction concerns to evaluate performance issues related to design. Documented findings in technical memoranda.
CSM Revision and ISCO Pilot Test for LNAPL Source Area, Kenai, Alaska Reviewed historical site information, developed comprehensive CSM, developed benzene plume maps, and scoped source area treatment for LNAPL body that is the ongoing source of the benzene plume.
Closed Refinery, Sunburst, Montana Drafted SOP for conducting LNAPL baildown tests.  Conducted LNAPL baildown tests and calculated LNAPL transmissivities to evaluate remedial options.  Collected site-wide synoptic fluid levels, supervised hollow stem auger drilling, logged continuous core, oversaw well installation, and sampled monitoring wells.
Former Natural Gas Compressor Station, Watkins, Colorado Served as the project manager responsible for expanding an SVE program at remote former compressor station to remediate soil and groundwater impacts related to a condensate release.  Oversaw shallow and deep SVE well installation and made on-the-fly well construction decisions resulting in successful well installation.  Collected soil samples for geotechnical analysis, collected groundwater samples using bladder pumps, and recovered LNAPL from monitoring and SVE wells.  Conducted LNAPL baildown tests, evaluated LNAPL transmissivities with respect to conventional pneumatic recovery methods, and proposed to install skimmer system at select well in addition to SVE.  Completed SVE system operation and maintenance (O&M).  Prepared semiannual progress reports.  Coordinated with local electrical company for power at the site.
Oil Refinery, Los Angeles, California Completed LNAPL feasibility and technology screen. Evaluated no further action, monitored natural attenuation, excavation, air sparging/SVE, LNAPL skimming, dual pump liquid extraction (DPLE), multiphase extraction (MPE), steam/hot air injection, water flooding, and three- and six-phase electrical resistance heating as remedial options for LNAPL mass removal. Retained LNAPL skimming, DPLE, and MPE for further consideration.
ISCO, Milwaukie, Oregon Supported the remediation program implemented at an active manufacturing facility with dense nonaqueous-phase liquid (DNAPL). Ran skid-mounted injection system and field-fabricated injection equipment to optimize oxidant delivery. Collected groundwater samples and calculated real-time sodium permanganate concentrations using a colorimeter to support field-scale injections. Evaluated the radius of influence and reaction kinetics of sodium permanganate with TCE and optimized oxidant delivery to undertreated areas using these real-time data. Calculated total TCE mass before and after each injection event to evaluate the change due to ISCO. Prepared technical report describing two rounds of successful ISCO.
Department of Energy Facility, Amarillo, Texas Developed code using Visual Basic to create tracking spreadsheets to allow for easy data entry and optimized pumping test analysis corrections.  Calculated head loss in pipes to select appropriate aboveground pump size for proposed system expansion at new injection wells.  Evaluated methods for dechlorination of site water.  Reviewed, analyzed, and summarized geophysical logs.  Drafted bioaugmentation work plan.

Vapor Intrusion

Sub-slab Depressurization System, Silver Spring, Maryland Provided technical support and oversight for installation of an SSDS to mitigate vapor intrusion related to tetrachloroethene (PCE)-impacted soil.  Measured differential pressure during SSDS installation to confirm sufficient system coverage.  Served as the primary author for the installation summary and O&M report.  Also served as the assistant project manager responsible for coordinating and completing routine monitoring and reporting events.  Evaluated depth of competent bedrock and presence of saprolite to evaluate offsite and onsite PCE migration related to nearby sources.

Planning and Permitting

Utah Pollutant Discharge Elimination System (UPDES) No Discharge Reporting, Aragonite, Utah Reviewed regional geology, hydrogeology, and water quality information to support a no‑discharge evaluation for an incineration facility.  Discussed results with the Utah DEQ and received approval to waive the UPDES permit.

Hydrologic Modeling

Landfill Cap Stability Evaluation, Casper, Wyoming Completed a soil saturation, infiltration, and stability analysis for a proposed landfill cap modification.

Modeling

Leapfrog Contaminant Mass Modeling, Confidential Location Estimated the total mass of metals present in soil, aquifer solids, and bedrock using Leapfrog contaminants extension. Evaluated dissolved phase mass removal and compared to in situ estimates to evaluate remedy time frame and optimization.
DyeLIF and DNAPL Model Development and CSM Revision, Cape Canaveral, Florida Prepared 3-dimensional ESS-based hydrostratigraphic model and incorporated results of a DyeLIF investigation. Mapped DNAPL horizontal and vertical extent. Incorporated DNAPL saturation results to predict the total volume of DNAPL present and support the remedial design.
LNAPL CSM, Oakland, California Oversaw a UVOST survey to delineate LNAPL extent due to an underground storage tank release. Prepared Leapfrog 3-dimensional visualization of the site and revised the LNAPL CSM. Presented results to the Department of Toxic Substances Control in a remedial options feasibility study and demonstrated that onsite impacts could be differentiated from a known offsite source.

Site Investigation and Soil Remediation

New/Used Oil Branch Service Center, Dodge City, Kansas Managed RCRA facility investigation under the streamlined EPA FIRST/Lean process to evaluate the extent of soil impacts related to an aboveground storage tank release. Oversaw soil boring investigation, logged continuous core, screened soil using a PID, and collected soil samples for analysis of VOCs. Modeled the horizontal and vertical extent of soil impacts and stratigraphy using Leapfrog and demonstrated their presence within coarse-grained soil. Prepared corrective measures study (CMS)/corrective measures implementation (CMI) work plan, CMS/CMI SVE pilot test, and full-scale design reports. Oversaw monitoring well and SVE well installation using a track-mounted sonic drilling rig. Constructed SVE system infrastructure, conducted SVE pilot test, completed SVE system O&M, collected air samples and submitted for laboratory analysis of TPH and VOCs, and changed out carbon. Calculated SVE system mass recovery in comparison to approximate total mass in subsurface based on soil concentrations to evaluate asymptotic mass recovery and progress toward remedy completion. Oversaw soil sampling to confirm effectiveness of SVE and remedy completion. Documented successful results in corrective measure completion report and calculated site-specific soil to groundwater standard using Kansas Department of Public Health and Environment guidance for the one limited vertical interval of soil in exceedance of the residential soil to groundwater to propose closure with no restrictive covenant.
Metals Impacted Groundwater, Confidential Location Served as technical and field lead on site investigation designed to fill data gaps required to constrain a numerical groundwater model and evaluate remedial alternatives. Outlined data gaps investigation and developed slug testing SOP. Oversaw piezometer installation and slug testing. Designed and installed weir structures to measure surface water flow rates. Measured flow rates and provided senior review of aquifer testing results.
Former Compressor Station, Dacono, Colorado Conducted closure soil boring investigation.  Oversaw drilling using dual-tube direct push drilling rig, screened samples using a PID, and collected soil samples.  Documented results and proposed excavation in site closure work plan.  Oversaw successful excavation and removal of impacted soil.
Closed Oil Refinery, Confidential Location Revised CSM to include two separate water-bearing zones separated by a low-permeability gray hard clay that prevented the downward migration of LNAPL-related impacts using Leapfrog.  Conducted LNAPL baildown tests and evaluated results relative to conventional pneumatic recovery.  Supported the design of a successful soil excavation and LNAPL treatment using ex situ soil shredding and chemical oxidation.

Site Investigation

CERCLA Superfund Site, Bridgeton, Missouri Served as the assistant project manager for more than 2 years on a CERCLA Superfund project to scope an RI/FS for one of the operable units (OU-3) at the site. Reviewed more than 40 years of historical literature and data, compiled these data into a comprehensive database, and developed a preliminary CSM to adequately scope and meet the objectives of the RI/FS. Applied principles of ESS to a 3-dimensional Leapfrog model to develop the preliminary CSM. Served as the primary author of the draft OU-3 RI/FS work plan and as a lead interface with EPA to communicate the proposed RI/FS approach. Provided support developing data quality objectives and drafting the sampling and analysis plan that included the field sampling plan and quality assurance project plan.
Former Wood-Treating Facility, North Carolina Served as a technical and senior lead on development and implementation of a supplemental remedial investigation for a Superfund site in North Carolina. Reviewed existing DNAPL distribution and proposed delineation and characterization of boreholes and samples. Supported development of extensive data quality objectives to address principal study questions. Evaluated DNAPL field screening methodology. Oversaw borehole advancement using direct push and sonic drilling techniques, logged boreholes, screened for DNAPL presence or absence, and collected soil samples. Conducted and evaluated pneumatic and traditional slug tests. Deployed telemetry-connected transducers for continuous monitoring. Completed senior review of 3-dimensional geological model prepared using Leapfrog software. Supported data evaluation, supplemental remedial investigation reporting, and feasibility study implementation.
Unlined Municipal Solid Waste Landfill, Larimer County, Colorado Served as the assistant project manager responsible for developing the CSM and site investigation work plan for an unlined landfill. Prepared a 3-dimensional Leapfrog CSM that incorporated high and low groundwater elevation surfaces to depict the extent of saturated waste and evaluate the source of organic and inorganic constituents present in onsite and offsite groundwater. Incorporated oxidation-reduction (redox) conditions, pH, and major ion chemistry into the site characterization work plan and proposed an iterative phased approach to temporary well installation and groundwater sampling. Prepared summary documents and supported remedial evaluation.
Used Oil Recycling Facility, Linden, New Jersey Oversaw drilling and installation of overburden and bedrock monitoring wells using track-mounted sonic and air-rotary drilling methods, respectively.  Collected grab-groundwater samples and analyzed using ColorTec for presence of VOCs.  Evaluated downhole borehole geophysics and ColorTec results to select screened intervals.  Collected soil samples for sieve and hydrometer analysis.  Deployed passive diffusion bags for VOC sampling.  Oversaw shallow soil borings and collected soil samples for VOC analysis to support facility redevelopment and expansion.
Unlined Municipal Solid Waste Landfill, Sheridan, Wyoming Served as the HRSC technical lead using the optical image hydraulic profiling tool to evaluate the extent of saturated waste in an unlined landfill and the potential source of groundwater impacts. Prepared a 3-dimensional Leapfrog CSM that incorporated the base of waste, top of saturated waste, and top of unsaturated waste and demonstrated that waste placement within a historical drainage was the likely source of saturated waste and impacts to groundwater. Reviewed historical data and generated a succinct CSM that described the presence of saturated waste; complicated geochemistry due to presence of pyrite, interbedded stratigraphy, and redox conditions; and uncertainty in the source of downgradient impacts to support a remedial evaluation.

Sweetenham, M.G., R.M. Maxwell, and P.M. Santi.  2017.  Assessing the timing and magnitude of precipitation-induced seepage into tunnels bored through fractured rock.  Tunnelling and Underground Space Tech. 65:62–75.

Sweetenham, M.G., F.J. Krembs, S.L. Lombardo, and G. Risse. 2022. Innovative treatment of a large, dilute, and commingled plume using a solar-powered in situ bioremediation and phytoremediation system. Battelle 12th International Conference on the Remediation of Chlorinated and Recalcitrant Compounds, Palm Springs, CA. May 22–26.

Sweetenham, M.G., and A.R. Riffel. 2022. Accelerating the path to site closure using a 3‑dimensional visualization tool and 2-dimensional spreadsheet model to revise the conceptual site model and predict extent of groundwater impacts. Battelle 12th International Conference on the Remediation of Chlorinated and Recalcitrant Compounds, Palm Springs, CA. May 22–26.

Sweetenham, M.G., and F.J. Krembs. 2018. Performance, cost, and emissions optimization using solar-powered in-situ bioremediation. Battelle 11th International Conference on the Remediation of Chlorinated and Recalcitrant Compounds, Palm Springs, CA. April 8–12.

Sweetenham, M.G., and F.J. Krembs. 2018. Successful TCE DNAPL source area remediation through real-time analysis of oxidant concentration during ISCO. Battelle 11th International Conference on the Remediation of Chlorinated and Recalcitrant Compounds, Palm Springs, CA. April 8–12.

Sweetenham, M.G., and A.R. Riffel. 2018. Streamlining the path to site closure using a 2‑dimensional spreadsheet model and a 3-dimensional visualization tool. Battelle 11th International Conference on the Remediation of Chlorinated and Recalcitrant Compounds, Palm Springs, CA. April 8–12.

Sweetenham, M.G.  2016.  LNAPL decision-making using a 3D UVOST visualization and LNAPL mobility assessment.  Battelle 10th International Conference on the Remediation of Chlorinated and Recalcitrant Compounds, Palm Springs, CA.  May 22–26.

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