Our knowledgeable and proven team of consulting and testifying experts has vast experience in a wide range of issues involving environmental and natural resources and an established and successful track record navigating complex litigation and resolving disputes.

Clients rely on Nathan’s experts for key insights with compelling, objective expert testimony and consulting support in matters involving regulatory enforcement; environmental contamination; insurance coverage; and multiple elements of response cost recovery actions; including NCP consistency, state law compliance, and cost allocation.


Stehpen Johnson - Nathan Associates

Stephen A. Johnson

Senior Vice President
+1 650 260 5344
John Simon Nathan Associates

John Simon

Senior Vice President
+1 202 505 1906
Marcia Williams

Marcia Williams

Senior Vice President
+1 424 703 3067


Alternate Dispute Resolution is often required as part of the litigation process. Since the early 1970s, our experts have worked extensively with the U.S. EPA, state environmental agencies, and private sector parties to define and resolve issues in complex environmental disputes. We apply our broad perspective to work effectively with all parties, including different branches of government, community representatives, nongovernmental organizations, and private sector parties, to find common solutions to disputes and to reduce the need for, or narrow the scope of, further litigation.

Environmental Disputes Mediation

Our experts advise clients and their counsel on many aspects of regulatory agency enforcement actions. We analyze the complex regulatory issues associated with alleged violations of U.S. and state environmental laws and regulations, and we help counsel develop effective defenses to allegations. This work often involves extensive factual analyses of alleged violations. Our experts also analyze and rebut government penalty assessments, develop persuasive counteroffers, assist with negotiations to determine any final penalty amount, and, if needed, provide expert testimony. Our work involves addressing both the gravity component of penalties and the alleged economic benefit of non-compliance. We provide additional services to help clients settle environmental enforcement actions, including development and valuation of supplemental environmental projects, preparation of ability-to pay analyses, determination of appropriate injunctive relief, and advice on settlement agreement provisions addressing the development and implementation of environmental management systems.

Environmental Enforcement & Penalty Analysis

Our experts in environmental engineering and science provide clarity to clients in the most difficult technical areas of environmental issues. We advise and provide testimony on issues that include contaminant source and timing, data analysis and management, and remediation strategies. For our clients, we can make the difference between an environmental problem and a solution. 

Environmental Science & Engineering

Our experts include the President Emeritus of the Sustainable Remediation Forum and the ASTM Task Group Lead for the Greener Cleanup Standard Guide. This expertise enables us to provide our clients with unique insight into the emerging field of green and sustainable remediation.

Green & Sustainable Remediation

Our experts combine economic analysis with scientific and technical expertise to provide clients with robust estimation of potential liabilities stemming from environmental, tort, product liability, business interruption, property value diminution, and other issues. Our experts and consultants have advanced capabilities in financial modeling, Monte Carlo analysis, statistics, liability risk projections, and related disciplines. We bring these skills to bear in our consulting services and expert testimony in adversarial proceedings as well as in bankruptcy matters, transactional due diligence, financial reserving and disclosures, and internal risk management and analysis. 

Liability Estimation

Entities pursuing or defending cost recovery claims under CERCLA and many state statutes must evaluate whether cost expenditures and remedial actions were performed consistent with National Contingency Plan (NCP) and state statutes and regulations. Our experts have provided cost recovery analysis and testimony for nearly 20 years at well over 100 sites, including major National Priority List sites and many significant state hazardous waste sites. Our work includes analyzing past response costs to determine their necessity, assessing whether costs were incurred consistent with NCP, evaluating the reasonableness of past response costs and adequacy of supporting documentation, analyzing potential future response actions and estimating their potential costs, and performing focused analyses that assess compliance with particular provisions of the NCP and state statutes and regulations. Along with providing analyses and testimony about past work, our experts advise clients on ongoing site investigation and cleanup actions to ensure that work is performed consistent with NCP and state requirements.

National Contingency Plan Consistency & Cost Analyses

Our experts have been retained as consulting and testifying experts in numerous natural resource damages (NRD) cases and have extensive experience evaluating NRD claims. We have worked with individual potentially responsible parties (PRPs) and committees of PRPs and bankruptcy estates on cases involving damages to rivers, lakes, groundwater, marine, and estuarine environments. Our work on behalf of defendants includes evaluation of lost human use and recreational service loss claims, critiques of natural resource trustees’ NRD claims, and reviews of costs and scale of restoration alternatives. 

Natural Resource Damages

Our experts provide consulting and expert testimony in a multiplicity of matters involving real estate economics in litigation. We address claims related to contamination or proximity to contamination, exposure to electric and magnetic fields, catastrophic events such as fires and explosions, and changes in development potential. We are experienced in applying all approaches, from traditional appraisal techniques to state-of-the-art GIS mapping systems and statistical techniques that include repeat sales, hedonic regression models, and survey techniques.

Property Value Diminution

Our remediation experts include former EPA upper management level staff and the editor-in-chief of the Remediation Journal. These talented and respected professionals develop innovative remediation strategies that are economical, effective, and compliant with regulatory requirements, including NCP requirements. Our experts also routinely provide expert opinions on the reasonableness of remediation strategies and costs.

Remediation Strategies

As consulting and testifying experts for individual parties and for large and diverse potentially responsible party groups, our experts have been involved in allocating environmental response costs and other damages among multiple parties at over 250 contaminated sites. To help multiple parties agree to an allocation, we also work as a neutral fact finder. Our experts are adept at applying principled and proven cost allocation approaches that include causation analysis, cost allocation analysis, cost modeling, potentially responsible party investigation and nexus package development, response cost validation, and strategic planning for negotiation of response costs shares. We have performed cost allocations at many types of sites including landfills, mining sites, manufacturing plants, waste reclamation and recycling facilities, rivers, urban waterways, and areas with regional groundwater contamination.

Response Cost Allocation

Our experts include environmental professionals who have been actively involved in the field since the inception of the U.S. EPA. They provide litigation consulting support and expert testimony regarding company or governmental standard of care, evaluate the historical practices of companies in nearly every industry, and provide detailed and authoritative assessments of whether these practices were within the standard of care. Our professionals are supported by our large in-house library of historical environmental documents that includes journal articles, laws, regulations, and government reports. These documents are beyond the reach of standard research tools, and give our experts a unique ability to place a company’s practices in an appropriate historical context.

Standard of Care

Our experts have been evaluating the environmental aspects of corporate transactions for nearly 30 years. Their deep and holistic understanding of the issues allows us to offer clients strategic and tactical insight into identifying environmental liabilities and structuring the environmental aspects of transactions, as well as provide expert testimony on environmental due diligence. Our experts also provide post-transaction services when disputes arise over environmental liabilities and obligations related to purchase and sale agreements.

Transaction Expertise