Our Goal

Our goal is to provide innovative, science-based solutions for complex environmental issues. 

Hire Us

Whether you are a private landowner, utility, municipality, state or federal agency, developer, non-profit, engineering firm, or another consulting group; we will identify the best solutions for your environment issues.

Thomas Gast, Principal Scientist

Mr. Gast formed Thomas Gast & Associates Environmental Consultants (TGAEC) after working for four years at Normandeau Associates as a Senior Scientist and 14 years at Thomas R. Payne and Associates.  Mr. Gast received a B.A. in Marine Resource Management from the University of California at Santa Cruz in 1988 and has worked on and led numerous freshwater fisheries and marine biology field crews in rigorous environments such as Antarctica, the Bering Sea, Yukon Territory, the High Sierras, and Sacramento San Joaquin Delta over the last 27 years.  Mr. Gast is particularly adept at implementing complex studies that require intricate logistics to provide innovative solutions.  Mr. Gast has had training in IFIM implementation; PHABSIM, SEFA, and RHABSIM analysis, and has been involved with all aspects of instream flow studies including study design, stakeholder meetings, field data collection, data analysis, interpretation, report writing, time series analysis, impact analysis, and results presentation.  Mr. Gast has worked extensively with the Acoustic Doppler Current Profiler (ADCP) collecting flow measurements and PHABSIM data, as well as developing several methods of deployments in challenging habitat types including shallow turbulent transects.  Mr. Gast has collected ADCP data for numerous instream flow projects and has traveled to the eastern U.S and northern Canada with the ADCP.  Mr. Gast is a licensed captain through the USCG, utilizing that capacity to implement instream flow, fish tracking, and monitoring studies on both large and small rivers.  Mr. Gast has also implemented fisheries and water quality monitoring studies utilizing multiple detection techniques such as direct observation, electrofishing, netting, and trapping as well as installing and maintaining data loggers and transmitters.

Our Staff

Mark Bowen, Ph.D.

Dr. Bowen is a senior associate scientist with extensive expertise in study design and quantitative methods.  He has 25 years of experience with water delivery and recovery projects, the preservation of aquatic ecosystems, conservation of listed species, habitat assessment and restoration, and support for governments to accomplish these same goals.  Dr. Bowen’s career history includes 16 years with the US Bureau of Reclamation and 9 years in the private sector as a project manager and technical team leader. He has led interdisciplinary teams that researched and solved biological problems and provided the best available scientific information. Dr. Bowen has also contributed to products for environmental review and analysis including NEPA and CEQA.Dr. Bowen has acted as a science liaison for the DWR. He has also conducted many projects for the DWR to meet Biological Opinion (BO) requirements, create and implement adaptive management plans, and determine water project operations’ effects on economically important and listed species and their habitats.

Our Vision

Julia Petreshen, M.S., Hydrologist

Ms. Petreshen is a hydrologist with extensive field and academic experience in forest ecohydrology. She earned her B.S. in Hydrology from the University of Wisconsin-Stevens Point  and worked several years as a Hydrologic Technician for the U.S. Forest Service. Ms. Petreshen gained specialized experience performing electrofishing surveys, identifying barriers to aquatic organism passage, and working in a water quality laboratory. Between 2017 - 2019, Ms. Petreshen worked for the Pacific Southwest Research Station monitoring turbidity during peak streamflow events in northern California. Ms. Petreshen gained critical skills associated with maintaining long-term research stations, monitoring streamflow, and collecting water quality samples. In 2021, Ms. Petreshen earned her M.S. in Earth Sciences from the University of Minnesota-Duluth, where she worked with the Dymond Watershed and Tree Ecohydrology Lab to investigate the effects of timber harvest on fog precipitation in the coast redwood forest.

Dr. Isidro Bosch, Associate Scientist

Dr. Bosch is a marine invertebrate biologist and Lake Ecologist with considerable experience working in the marine environment as well as lakes and streams and SCUBA diving in Antarctica, California, the Caribbean and the Mediterranean.  He has published 25 papers in peer-reviewed journals and completed more than a dozen technical reports on various aspects of lake ecology and watershed management.  At SUNY Geneseo, Dr. Bosch teaches courses in Invertebrate Zoology, Marine and Freshwater Community/Ecosystem Ecology, Principles of Ecology, General Biology and more. He has received various awards for teaching, mentoring and research and obtained competitive grants from the NSF to study the effects of ozone depletion on marine invertebrate larvae in Antarctica and from the USDA and other funding agencies to study the effects of watershed management on growth of algae, macrophytes and cyanobacteria in temperate lakes.  His current research is on the cyanobacteria microbiome that occurs in association with sea star larvae in the open ocean, and on the effects of partial mixing of the lake water column in triggering the onset of cyanobacterial blooms in shallow lakes.

Dr. Isidro Bosch obtained his Bachelor’s degree in Aquatic Biology from the University of California at Santa Barbara in 1981 and his Ph.D. in Biology from U.C. Santa Cruz in 1989.  In 1992 Dr. Bosch joined the biology faculty at the State University of New York College at Geneseo, where he is currently a full Professor.

Our Strength


Our commitment to excellent service: we will team with you throughout each project to ensure the best, most cost-effective, and timely results possible.

Joshua Cahill

Deliver science-based, economical, and on-time environmental consulting solutions for every client.

Nicholas Easterbrook is an experienced fisheries biologist with a demonstrated history of working with multiple consulting companies in the private sector as well as for state and federal agencies. His skills include scientific research, collaboration with stakeholders, aquatic species population and habitat monitoring, creative problem solving, state and federal permitting, technical report preparation and project oversight. Mr. Easterbrook has expertise in working with anadromous salmonids, conducting environmental compliance studies, and applying fisheries fieldwork techniques. He has extensive knowledge and experience handling special status species including Coho and Chinook salmon, Tidewater Goby, Pacific Lamprey, Steelhead and Coastal Cutthroat Trout, Sierra Nevada and Foothill Yellow-Legged Frogs, and Western Pond Turtles throughout their life history stages. Mr. Easterbrook collects, analyzes, and reports high quality data through rigorous methodology, attention to details, and professionalism.

Melati Kaye, M.A., Environmental Spatial Analyst
Melati Kaye is an experienced field tech with a demonstrated history of working in various ecosystems, as well as for state and federal agencies. Her skills include scientific research, collaboration with stakeholders, creative problem solving, state and federal permitting, technical report preparation and project oversight. Ms. Kaye has expertise working with anadromous salmonids, and identifying Coho and Chinook salmon, Pacific Lamprey, Steelhead and Coastal Cutthroat Trout, and Foothill Yellow-Legged Frogs. Ms. Kaye collects and reports high quality data with attention to details.