Current Officers

These are the people currently working at CEMS.

Maggie Mandell
Maggie MandellPresident

Current Employer: Environmental Engineer, Environmental Works, Inc., (301)943-2830

Maggie Mandell is a registered Professional Engineer (PE) with more than 15 years of experience in environmental engineering and consulting. She began her career with a 7 year stint as a consultant with Booz Allen Hamilton, conducting environmental compliance audits and providing environmental management support to mostly DoD clients. She then transitioned to Potomac-Hudson Engineering, a small business engineering firm, followed by Versar (formerly J.M. Waller), where she supported dozens of EPA Superfund Site projects and was also co-chair of the Versar Sustainability Program.  Maggie joined Environmental Works, Inc. (EWI) in October 2019 and has been supporting a variety of environmental compliance and remediation projects.  Maggie recently became a certified FAA Part 107 drone pilot and looks forward to expanding EWI’s environmental services to include this technology.

Maggie earned a BSE in Civil & Environmental Engineering from Duke University and a MS in Environmental Engineering from Northwestern University. Originally from Bethesda, MD, she and her husband moved to Denver in 2013; they spend their free time taking advantage of all that beautiful Colorado has to offer… hiking, biking, and skiing… with their daughter, son, and furbaby.


Suzanne Gabriele
Suzanne GabrieleVice-President

Secondary Position: Committee Chair – Fall Conference

Current Employer: Geosyntec Consultants, Inc., 44 Union Blvd, Suite 620, Lakewood, CO 80228, (303) 790-1340

Suzanne Gabriele’s consulting practice focuses on environmental, health, safety (EHS) management for a variety of industries including mining, oil & gas, food processing, electrical utilities, manufacturing, health services, and municipal governments.

Having worked as a strategic advisor to private and public sector clients at both the corporate and operational levels, Suzanne has extensive experience helping clients manage risks and recognizing opportunities to improve EHS performance. Examples of Suzanne’s experience include managing numerous policy and management system development, implementation, and improvement projects including systems conforming to and certified under International Organization for Standardization (ISO) standards. Suzanne has also managed numerous projects where the U.S. Environmental Protection Agency (EPA) compliance-focused environmental management system standard is required. Suzanne’s practice also includes advising on operational management plans, and performance and compliance monitoring and auditing programs.

In addition, Suzanne has extensive knowledge of regulatory programs and the ways in which their regulations apply in the built world. Ms. Gabriele works with clients to design programs to manage obligation under these laws and also voluntary commitments relative to environmental, social, and governance (ESG). She directs and manages compliance audit programs and supports clients in identifying root cause and corrective actions for noncompliance.

To advance the state of the practice, Suzanne is the chair of Geosyntec’s Environmental Management Action Group Steering Committee and a mentor to mid-career practitioners within Geosyntec.

Suzanne relocated to Denver in 1992 from the New York metropolitan area with her husband with the intent of returning there in 3 – 5 years, but around 20 years in, they decided to stay. They’re nearly done raising three self-reliant, intelligent young women and enjoy travel, food, music, backpacking, and backcountry skiing as a family.

Erik Gessert
Erik GessertPast President

Secondary Position: Committee Chair – Fall Conference, Co-Chair – Membership, Networking, and Outreach Committee

Current Employer: Terracon Consultants, Inc., 10625 W. I-70 Frontage Road N, #3, Wheat Ridge, CO, 80033, (303)454-5277

Erik grew up in Madison, Wisconsin where he developed a passion for all things outdoors, spending summers on backpacking trips with friends and discovering firsthand the reasoning of A Sand County Almanac. His enthusiasm for the environment lead him to the University of Wisconsin-Madison where he earned a BS in Environmental Engineering with a minor in Environmental Studies.

Erik is a registered Professional Engineer in the State of Colorado and works for Terracon Consultants, Inc. as a senior environmental engineer where he leads the national LNAPL practice group and provides technical expertise on local, regional and national environmental projects.  Erik is passionate about incorporating and advancing 21st century concepts and methods including conceptual site model development, green and sustainable remediation practices, advanced site characterization technologies and SMART objective development to address environmental concerns.  Previously, Erik was the supervisor of the petroleum remediation group for the Colorado Division of Oil and Public Safety.  In this role, Erik developed and implemented some major program initiatives including enhanced risk-based closure criteria and the Recognized Environmental Professional program.

Through good fortune, Erik has been able to work with the Interstate Regulatory Technical Council (ITRC) as a Team Lead for the Light Non-Aqueous Phase Liquid (LNAPL) team.  In this role, Erik had the opportunity to present two day LNAPL training classes with a group of nationally recognized experts as well as deliver internet-based training on the topic to thousands of participants across the world.  As a Team Lead, Erik was responsible for leading the team in the development of an updated, web-based guidance on LNAPL from proposal submittal through project closeout.  LNAPL Site Management: LCSM Evolution, Decision Process, and Remedial Technologies was published in March 2018.

When away from work, Erik can still be found outdoors spending time with his children reexperiencing the reasoning of A Sand County Almanac.

John Fontana, CPG, CWD
John Fontana, CPG, CWDTreasurer

Current Employer:  Vista Geoscience LLC, 130 Capital Drive, Suite A, Golden, CO 80401, (303) 277-1694

John Fontana is a Certified Professional Geologist (CPG #11985), an NGWA Certified Well Driller (CWD #12270)), a licensed water well driller (NM, NE, UT, SD, OK, KS), and serves as President/CEO and owner of Vista GeoScience LLC, based in Golden, Colorado.  John oversees all business operations at Vista, including environmental drilling (Geoprobe®), injection remediation services, soil gas investigations, and High-Resolution Site Characterization (HRSC) and 3D data modeling services.  John pioneered and introduced many of these services in the Rocky Mountain region and has supervised many Triad type environmental site characterizations and remediation projects at major DOD, DOE, and commercial/industrial sites across the country.

John has served as co-chair on the CEMS Program Committee, and on the Board of Directors as a Director, President, Past President, and currently as Treasurer.  He also serves as a Board Member/Advisor on the Executive Committee for the Colorado Section of the American Institute of Professional Geologists (AIPG).  John is also a member of CGWA, CWWCA, NGWA, AAPG, AEG, RMAG, RMAEP, ITRC (IAP), SAME, and SWANA. He served on the EPA Scientific Advisory Board on the Impacts of Hydraulic Fracturing on Drinking Water, and has also provided expert testimony in the area of stray gas (methane) migration issues.  Most recently John served on the Interstate Regulatory Technical Council (ITRC) teams and assisting in writing two guidance documents;  Implementing Advanced Site Characterization Tools (2019, ASCT-1) and Optimizing Injection Strategies and In-Situ Remediation Performance (2020, OIS-ISRP-1 ).

John’s 40 years of experience includes: 35 years as a business owner/manager, well-site geologist, laboratory management, managing domestic and international geochemical exploration programs, environmental site investigations, geotechnical and environmental drilling technologies, in-situ remediation injection design and implementation, analysis of soil gas for trace natural gases or contaminants, forensic analysis including stable isotopes, environmental baseline studies, carbon sequestration monitoring, statistical data analysis, mapping and 3D data modeling to create conceptual site models from integrated data sets.

John earned his BS degree in Geology, Oceanography and Physics from Humboldt State University in 1981.  Originally from California, John and his wife moved to Colorado in 1981, and now live in the Ken-Caryl Valley area.  Empty nesters, they enjoy time with their daughter Christina and son David whenever possible.  John volunteered for several years as a Cub Master and Scout Master where he enjoyed backpacking, camping and canoeing in the Rocky Mountains while teaching leadership and outdoor skills to young men.  He enjoys skiing, boating, fishing, hiking, SCUBA diving, as well as the occasional Rockies game. 

You can link up with John at


President & CEO


130 Capital Drive, Suite A, Golden, Colorado 80401
Work Phone: 303-277-1694,

Karen Trantow Lim, P.G.
Karen Trantow Lim, P.G. Secretary

Current Employer: Program Manager, Environmental Compliance; CDH Consulting, LLC  303-501-3415

Karen Trantow Lim, P.G. is an environmental compliance program manager and senior geologist with 33 years of environmental consulting experience including due diligence audits, Phase I/II environmental site assessments, stormwater permits and plans, complex NPDES permitting, FRP/SPCC plans, SARA Title III Tier 2 and TRI reporting, hydrogeologic investigations, reclamation, pollution prevention and waste management, tank removals and remediation, comprehensive regulatory review and interpretation, and hazardous waste site investigations. Her clients operate nationwide, primarily in the oil&gas industry in Colorado, Louisiana, North Dakota, Texas, Utah, and Wyoming.

Karen grew up in Santa Barbara, California and migrated out to Colorado after college and a semester abroad in Sweden.  She began her environmental consulting career in California, then worked for EnecoTech Inc here in Denver, primarily focused on underground storage tank assessments.  While her husband got his masters degree in Pennsylvania, Karen worked for Versar and HLA in Philadelphia on army and air force facility assessments, large industrial client remediation and hydrogeologic assessments, due diligence projects and overall compliance efforts.  Returning to Denver, she had the opportunity to work for the oil&gas industry, focusing on environmental compliance for oilfield service companies, midstream and upstream oil&gas clients while at LT Environmental, Inc.  In 2021, Karen joined CDH Consulting to continue this pursuit.  She has a Bachelor of Science degree in Geology and is a registered Professional Geologist in Pennsylvania, Texas and Wyoming.

Karen enjoys hiking and skiing in the Rocky Mountains along with any time spent with their son, a senior at CU Denver.  Prior to covid, she completed an 8-day hiking trek along the coast of Northern Ireland. And she’s a diehard Bronco fan!

Board Members and Liaisons

Our board members and liaisons

Fonda Apostolopoulos
Fonda ApostolopoulosBoard Member and CDPHE Liaison

Secondary Position: Committee Member – Co-Chair Scholarship
Current Employer: CDPHE, 4300 Cherry Creek Drive South, Denver, CO 80246-1530, (303)692-3411

Fonda Apostolopoulos works for the Colorado Department of Public Health and Environment (CDPHE). He runs the Voluntary Cleanup program and is the Brownfields coordinator. He has worked for CDPHE for over 29 years and has worked as an On-Scene Coordinator and Project Manager on various Superfund Sites. His sites vary from metals smelting sites, Solid Waste Landfills, to volatile organic compounds in groundwater, to radioactive cleanup sites.

Rachel Blomberg
Rachel BlombergBoard Member and CDHPE Liaison

Current Employer: CDPHE, 4300 Cherry Creek Drive South, Denver, CO 80246-1530, (303)691-4024

Rachel Blomberg is a registered professional engineer (P.E.) and serves as a hydrologist and project manager for the Colorado Department of Public Health and Environment (CDPHE) in the Hazardous Materials and Waste Management Division Remediation Program. She has been employed by CDPHE since 2017, and worked for the USGS in their Colorado Water Science Center before joining the State. Rachel’s primary duties range from asbestos mitigation to contaminated groundwater cleanup on active military bases and formerly used defense sites, but she primarily focuses on emerging contaminants through her PFAS response efforts at Colorado’s Air Force Bases and through her involvement in drafting new site specific groundwater standards.

Rachel earned a BS from Cornell University and a MS from Colorado School of Mines. Originally from Northern California, she has lived in NY, AK, ME, Denmark and finally Colorado. She spends much of her free time renovating her century old home in Denver. When she is not doing that, she is most likely hiking or cross country skiing with her American Bulldog, fishing, cooking a new recipe, or enjoying a local show or game night.

Mike Jahn
Mike JahnBoard Member

Current Employer: Tasman Geosciences, Inc., 6899 Pecos Street, Unit C, Denver, CO, 80221, (303)487-1228

Evan Singleton
Evan SingletonBoard Member

Current Employer: Gablehouse Granberg, LLC , 410 17th Street, #275, Denver, CO, 80202-4449, (303)572-0050

Evan has been an attorney with Gablehouse Granberg, LLC since 2015. He assists clients on a wide range of environmental matters, including NEPA, clean air, clean water, and hazardous and solid waste.

Evan earned his law degree from the Sandra Day O’Connor College of Law at Arizona State University, where he was on the university’s Energy Policy Innovation Council (EPIC), a joint program between the law school and other grad programs focusing on law, engineering/science, sustainability, and public policy in the energy sector. Evan  also competed in the Inter-American Sustainable Development Moot Court Competition in Bogotá, Colombia in 2013 and presented on international environmental law at the UN Framework Convention on Climate Change conference in Bonn, Germany in the same year.

Glen Vallance
Glen VallanceBoard Member

Current Employer: Principal / Environmental Services Manager, CGRS Inc.

Michael Whelan
Michael WhelanBoard Member

Secondary Position: Committee Member – Fall Conference

Current Employer: Principal Engineer, Anchor QEA, LLC, 12596 West Bayaud Ave., Suite 450, Lakewood, Colorado 80228, Direct (303) 952-4850, Mobile (760) 845-2983

As a leader for Anchor QEA’s work in the Rocky Mountain region and with numerous West Coast project involvements, Mr. Whelan has 23 years of experience specializing in dredging and civil earthwork design for lakes and shorelines, restoration of stream habitat, development of waterfront facilities, and upland and offshore environmental remediation. His career originated with a bachelor degree from Colorado School of Mines, supplemented by graduate studies in environmental and geotechnical engineering at Georgia Tech and MIT, respectively. Today, after multi-year stints in Seattle and San Diego, he has a strong understanding of regulatory, environmental, and permitting-related issues, frequently applied to multi-party mediation and legal deposition settings. He currently lives in Evergreen with his wife and has two sons, one at Mines and one finishing high school.

Stephen Dyment
Stephen DymentUS Environmental Protection Agency, Region 8 - Liaison

Current Employer: US EPA Region 8,  1595 Wynkoop Street, Denver, CO, 80202-1129, (303)312-7044

Stephen Dyment is a chemist with more than 20 years of experience including 4 years in a commercial analytical laboratory and 8 years in environmental consulting. He joined EPA in 2005 with a focus towards enhancing acceptance and use of emerging analytical technologies and sampling strategies. His perspective draws upon years of practical laboratory and field experience to apply EPA’s Triad approach and associated best practices at sites in Superfund, Brownfields, RCRA, UST and State programs. Mr. Dyment’s efforts have resulted in the development of numerous EPA case studies, profiles, and training courses that outline successful strategies for the use and understanding of high resolution/collaborative data sets, adaptive QC programs, and real time analytics. He provides direct project support for sites in Superfund, RCRA, and Brownfields, conducts research on issues of national significance while connecting regional research needs with national ORD expertise, and teaches classes on sampling design, x-ray fluorescence, high resolution site characterization, 3D visualization and other technical subjects (see Mr. Dyment holds a B.S. in Environmental Science/Toxicology from the University of Massachusetts at Amherst.

Tom Fox
Tom FoxColorado Division of Oil and Public Safety - Liaison

Current Employer: Colorado Division of Oil and Public Safety,  633 17th Street, Suite 500, Denver, CO, 80202, (720)346-1885

Tom is an Environmental Protection Specialist with the Petroleum Program for the Colorado Division of Oil and Public Safety (OPS). He earned a BS in Earth Sciences from Millersville State College (PA) and an MS in Geology from Michigan State University. After four years as a petroleum exploration geologist with Atlantic Richfield (ARCO) in Denver, Tom transitioned to environmental consulting. His dominant focus has been petroleum assessment and remediation, varying from corner gas stations to refineries and (often remote) pipeline pumping stations. Miscellaneous work, no less interesting, has included landfills, Phase I ESAs, SPCC Plan preparation, and CVOC sites. Traveling to most of the states, and experiencing a variety of weather and regulatory climates, was a particularly fun and educational side benefit.

Tom joined OPS in 2007. His work at OPS has involved updating cost guidelines for reimbursement; supporting the introduction of electronic, standard format reports; and investigation into the efficacy of activated carbon injection in Colorado. By 2015, Tom began working with the Interstate Technology and Regulatory Council (ITRC) updating the LNAPL document released in 2018; Tom has participated in all of the webinars on this topic to date and also traveled to China in 2019 to present the ITRC classroom training. Most recently, Tom has assisted with OPS’ Recognized Environmental Professional (REP) program.

Committee Members

Our committee members

Josh Lee
Josh LeeCommittee Chair - Golf

Current Employer: Department Manager, Burns & McDonnell, 9785 Maroon Circle, Suite 400, Centennial, CO 80112, (970) 210-6571

Andy Horn
Andy HornCommittee Chair - Monthly Program

Current Employer: PG, Principal Hydrogeologist, Environmental Works, Inc., (301)943-2830

Andy has been a consulting hydrogeologist since 1991 performing groundwater studies for a variety of water resources and environmental assessment and remediation projects. Andy has performed hydrogeologic investigations on hazardous waste sites / facilities including US EPA Superfund, RCRA, PFAS contamination, manufacturing, fueling & maintenance, chemical storage & distribution, real estate due diligence, and for basic scientific research. Andy’s areas of expertise include defensible data collection program design and management, data analysis and synthesis, and study reporting and presentation. He has been a CEMS Board member since 2017. Andy is a licensed Professional Geologist in Kansas and Wyoming; he earned his B.S. in Geology from the University of Alabama in 1990, and his M.Sc. in Geology from the University of Colorado in 1997. Andy enjoys the outdoors and can often be found skiing in the winter and whitewater rafting in the spring, summer, and fall.

Juliana Reid
Juliana ReidCEMS Administrative Assistant

Secondary Position: Website Administrator
Current Employer: Administrative Assistant, CO Environmental Management Society (CEMS), PO Box 2426, Evergreen, CO 80437-2426

Born in England to Italian and American parents, Juliana immigrated to the U.S. in 1972. She was raised in New Jersey and received a Bachelor of Science degree in Computer Science (with a minor in Philosophy) from Lehigh University in Bethlehem, Pennsylvania. After moving to Colorado in 1992, she and her husband Dave raised two children while enjoying all that the Centennial state has to offer. She enjoys skiing, movies, reading, author lectures, and travel. She is also enjoying being an empty nester.

Juliana has been happily employed by CEMS since September 2009.