Senior Scientists

Mr. Tymchak is a Hydrologist at Gradient who specializes in analyzing the source, transport, and fate of  a broad range of chemicals through soil, groundwater, and bedrock. As a consultant for the past 10 years, he has managed investigations at a variety of sites including upstream oil and gas development, refineries, solid waste landfills and one of the nation’s largest groundwater National Priorities List sites. Mr. Tymchak's water resources background includes evaluating impacts of agricultural pumping on aquifer storage and streamflow, and conducting data analysis and modeling studies of rainfall runoff dynamics in a variety of watersheds.  He has applied his expertise in water resources to solve complex challenges in a large-scale water-allocation cases and in a national-scale case involving contaminate transport to water suppliers throughout the country.

Water Rights Dispute:  Provided technical evaluation for an equitable water allocation request before the U.S. Supreme Court (Original Action 142). Evaluations included assessments of watershed hydrology, groundwater flow and human water use.

Hydraulic Fracturing Risk Evaluation:  Provided a review of potential risks to water resources related to hydraulic fracturing in the Marcellus Shale in Pennsylvania.  Analyses included potential land use impacts and risks related to fluids migrating upward from the hydraulically fractured formation.

Stray Gas Migration Investigation:  Evaluated whether methane migrated upward from the Marcellus Shale to shallow water supply wells in Pennsylvania.  Analyses included methane, gas isotope, and groundwater geochemistry data, in addition to an evaluation of hydraulic fracture growth in the vicinity of shale gas wells.

Remedy Evaluation and Cost Analysis:  Performed remedy alternative analysis for addressing TENORM waste in a landfill.  Developed remedial action objectives for the impacted media and analyzed costs for each remediation alternative.  Resulted in the acceptance of a Corrective Action Plan by the state agency.

NCP Consistency Evaluation:  Evaluated the NCP consistency of response actions and their costs undertaken by a municipal water purveyor at one of the nation's largest groundwater NPL sites.

Product Release at a Refinery:  Evaluation at a refinery to determine the timing, storage and transport of a product release.  The analysis included forensic chemical data, potential groundwater and contaminant transport pathways, and a review of historical site information to understand the nature and extent of contaminants.

Former Petroleum Storage Facility:  Analyzed potential pathways for pollutant transport from a petroleum storage facility to nearby surface water body.  Estimated chemical travel times and evaluated other sources of contamination to quantify the proportion of contaminants attributable to the facility.