Jon Rohrer,

P.G., C.Hg.

  • Principal Hydrogeologist

Mr. Rohrer is a Principal Hydrogeologist with 20 years of experience. He has a M.S. in Subsurface Hydrology from the University of Arizona (1996) and a B.S. in Geological Sciences from Lehigh University (1993). Mr. Rohrer has provided State and Federal expert testimony on a number of technical topics including: historical operations and chemical usage relating to spills and/or releases to the subsurface; responsible party evaluations; fate and transport of contaminants in soil, soil vapor and groundwater; the extent, severity and longevity of groundwater impacts in relation to damage assertions; and, technical aspects underlying cost-allocation approaches. His clients include small businesses and property owners up through Fortune 500 companies that he has successfully assisted in resolving a range of environmental challenges. Mr. Rohrer has also implemented cost-effective and necessary investigation and remediation actions with buy-in from regulators using defined processes and end-points. For example, Mr. Rohrer assisted a PRP-consortium in acquiring a technical impracticability waiver for groundwater impacts in fractured limestone at a major Superfund Site. Mr. Rohrer has extensive experience with a range of contaminants, regulatory settings and geological environments.

Representative Expert Retentions/Appearances

  • Kvaerner Aronson, Inc. vs. Mammoth Mountain Ski Area, Mammoth Mountain Ski Area vs. Kvaerner Aronson, Inc. Emco Wheaton Retail Corporation, et al., Mono County Superior Court, Case Number 12928. 2000.
  • Cambria Community Services District vs. Chevron U.S.A., Inc., Chevron Products Company and ChevronTexaco Corporation, San Luis Obispo County Superior Case Number 109521. 2000
  • City of Morro Bay Nuisance Abatement Hearings, RE MTBE impacts to groundwater, January, 2001.
  • City of Morro Bay, California Energy Commission Application for Certification (00-AFC-12) Hearings for the Morro Bay Power Plant. January 29, 2002.
  • California Senate Select Committee on Perchlorate Contamination, February 27, 2004
  • Orange County Water District vs. Northrop Corporation et. al., Orange County Superior Court, Case Number 04CC00715, 2004.
  • Confidential Client, Insurance Review of Reasonableness of Site Investigation and Cleanup Costs, Henderson, NV, 2005.
  • Orange County Water District vs. Sabic Innovative Plastics, LLC et. al., Orange County Superior Court, Case Number 00078246, 2008.
  • Nammo Talley v. Allstate, United States District Court, District of Arizona, Case Number 2:11cv01007SMM, 2011.
  • Alcoa Inc. vs. Alcan Rolled Products-Ravenswood LLC, F/K/A Pechiney Rolled Products LLC, Pechiney Cast Plate Inc., and Century Aluminum Company, U.S. District Court for the District of Delaware (C.A. No. 06-451-SLR-SRF), 2007.
  • HTL Automotive Inc. vs. 1351 Orizaba Avenue LLC, Los Angeles County Superior Court, Case Number BC651307, 2017.

Representative Projects

  • Investigation/Remediation
  • Mr. Rohrer led all aspects of remedial investigation and design for a major gasoline release, including MTBE in a fractured volcanic aquifer. Due to the success of multiple-line of evidence technical investigation approach, a significant mass of contamination was recovered from deep in the vadose zone, after targeting a volcanic-flow related set of migration pathways.
  • Regulatory Support/Site Closure
  • Mr. Rohrer led a technical portfolio analysis and subsequent regulatory interactions that resulted in site-closure for eight MTBE impacted gasoline station sites for a major oil company. This included performing several avenues of technical analysis for existing data to break the cycle of low-effectiveness spending and regulatory inertia that was hindering closure of these sites.
  • PRP Searches
  • Mr. Rohrer in several cases has either performed detailed records searches for one-property or for an area resulting in identification of viable potentially responsible parties. This has involved certified manifest acquisition and non-traditional avenues of research.
  • NRDA
  • Mr. Rohrer was the field-leader for hydrogeology-aspects of a Natural Resource Damage Assessment at a site with millions of gallons of free-product and identified an aqueous discharge point to a local river. The technical work supported a settlement of more than $40M by the California State Attorney General, Department of Fish and Wildlife and the California Coastal Commission.
  • Emergent Contaminants
  • Worked on numerous of cases involving MTBE, TBA, perchlorate and 1,4-dioxane in the early stages of each of these contaminants developments as contaminants of concern.

Journal Publications and Recent Proceedings

  • Rohrer, J.W., with Aronovsky, R.A., Cheney, B.G., Nyquist, P.A., “Superfund Sleuths: Legal and Technical Methods for Securing Contribution,” 2012. Los Angeles County Bar Association, Environmental Law Section, Spring Symposium, April 27, 2012.
  • Rohrer, J.W. and Jonker, P.E., “Speaking their Language: Pollution Science for the Attorney.” 2007. Los Angeles County Bar Association, Environmental Section: 21st Annual Environmental Law Super Symposium. March 23.
  • Rohrer, J.W., Ausburn, M.P., Beal, N.B. and Hornick, D., “California MTBE Retrospective Evaluation: Predictions vs. 2005 Outcome,” 2006. NGWA 2006 Petroleum Hydrocarbons and Organic Chemicals in Ground Water®: Prevention, Assessment, and Remediation Conference, November.
  • Rohrer, J.W., Beck, R.M., Trudell, M.R. and Beal, N.B., “Prioritizing Perchlorate Cleanup of Water Resources in Southern California.” 2005. National Groundwater Resources Association, Conference on MTBE and Perchlorate: Assessment, Remediation, and Public Policy.
  • Hardisty, P.E., Dottridge, J. and Rohrer, J.W., “Application of Digital Borehole Imaging Data for Characterization of NAPLs in Fractured Rock.” 2001 Fractured Rock, 2001.


  • Contaminant Transport and Fate in a Source Zone of a Chlorinated-Solvent Contaminated Superfund Site: Overview and Initial Results of an Advanced Site Characterization Project. Chapter 19 in: Innovative Subsurface Remediation: Field Testing of Physical, Chemical, and Characterization Technologies, Brusseau, M.L., Sabatini, D.A., Gierke, J.S., and Annable, M.D., eds., American Chemical Society, Washington DC, 1999. (Co-Authored with Brusseau, M. L., Rohrer, J. W., Decker, T. M., Nelson, N. T., and Linderfelt, W. R.)
  • M.S., Subsurface Hydrology
  • University of Arizona, Tucson, AZ
  • B.S., Geological Sciences
  • Lehigh University, Bethlehem, PA
Areas of Expertise
  • Litigation Consulting
  • Litigation Expert Testimony
  • Contaminant Fate & Transport
  • Source Identification
  • Soil and Groundwater Investigation
  • Regulatory Negotiations
  • Portfolio Evaluation, Site Prioritization and Closure