Vident Partners provides vetted water pollution and soil contamination expert witnesses for cases involving Clean Water Act citizen suits, NPDES permit violations, jurisdiction over wetlands and streams, discharges through groundwater, spills, and damage to land and surface water nationwide. Request a referral today.
Find a Water Pollution & Soil Contamination Expert →Overview
A water pollution expert answers three questions: what reached the water or soil, where did it come from, and did that breach a permit, a statute, or a duty? In federal Clean Water Act cases there is a fourth question that comes first: is this water covered at all? This page covers surface water, wetlands and soil damage. How groundwater moves belongs to a hydrogeologist, cleanup cost liability belongs to a hazardous waste expert, and human health effects belong to a toxicologist.
The statute starts with a flat rule. Except in compliance with listed sections, the discharge of any pollutant by any person shall be unlawful 1. A discharge of a pollutant means any addition of any pollutant to navigable waters from any point source 2. Most dischargers operate under a National Pollutant Discharge Elimination System permit 3. So many cases are about records: monitoring reports, permit limits, and whether the facility's own numbers show a violation.
This question changed in 2023 and is still moving. In Sackett v. EPA, the Supreme Court held that waters under the Act refers only to geographic features described in ordinary parlance as streams, oceans, rivers and lakes, and to adjacent wetlands indistinguishable from them because of a continuous surface connection 4. A party asserting jurisdiction over a wetland must show the adjacent water is relatively permanent and connected to traditional navigable waters, and that the wetland has a continuous surface connection with it 4.
The regulations are uneven. EPA's status page says the agencies are implementing the January 2023 rule, as amended, in 24 states, the District of Columbia and the territories, and in the other 26 states are interpreting the term consistent with the pre-2015 regime and Sackett 5. The agencies proposed a revised definition in 2025 and, on September 4, 2026, announced a supplemental proposal, with comments closing October 9, 2026 6. A site's status can depend on its state and on the date of the discharge, so an expert should state which rule was applied and confirm the current position before signing a report.
The expert's work is often fieldwork: surface flow, seasonal duration, soils, and mapped and observed connections.
A point source may reach navigable water indirectly. County of Maui v. Hawaii Wildlife Fund held that a permit is required when there is a direct discharge from a point source into navigable waters or the functional equivalent of a direct discharge 7. Many factors may be relevant, and time and distance will be the most important in most cases, along with the nature of the material through which the pollutant travels and how far it is diluted or chemically changed 7. That language calls for tracer studies, flow modeling and source analysis.
Private parties have a real role. Any citizen may commence a civil action, subject to stated limits, and must generally give 60 days' notice to EPA, the state, and the alleged violator 8. A court may award costs of litigation, including reasonable attorney and expert witness fees, to a prevailing or substantially prevailing party when appropriate 8. That makes expert costs part of the fee dispute. Government enforcement reaches civil penalties per day of violation, and criminal penalties for negligent and knowing violations 9.
For polluted water bodies, Section 303(d) has EPA assist states, territories and authorized tribes in listing impaired waters and developing Total Maximum Daily Loads 10. A plaintiff or defendant may need to explain how a discharge fits within a TMDL, and whether other sources explain the water's condition.
Soil cases usually arise under state tort law, leases, or sale contracts, or alongside cleanup statutes. The expert defines the extent of contamination with borings and samples, compares results with background conditions and applicable screening levels, and estimates the cost and duration of cleanup. Then comes value: how much did contamination reduce the property, and is it temporary or permanent? A real estate appraiser usually addresses stigma. Agriculture adds crop loss.
Where several facilities share a watershed, chemical fingerprinting and timing of releases help separate them. Isotopes, ratios of compounds and historical aerial photographs can all contribute. A strong report shows how alternative sources were excluded.
Look for an environmental scientist or engineer with direct field and permit experience, or a wetland scientist for jurisdiction. Licensing varies by state, so check whether a professional engineer or geologist license is required. A hydrogeologist addresses subsurface flow. An environmental chemist addresses fingerprinting. An appraiser addresses lost value. A toxicologist addresses risk to people or wildlife.
County of Maui held that a Clean Water Act permit is required for a direct discharge from a point source into navigable waters or for the functional equivalent of a direct discharge, with time and distance the most important factors in most cases.
Case Types
Clean Water Act citizen suits and government enforcement
NPDES permit exceedances and monitoring disputes
Wetlands and streams jurisdiction disputes after Sackett
Discharges to surface water through groundwater
Spills from pipelines, tanks, and industrial facilities
Stormwater and construction runoff claims
Soil contamination in property sale and lease disputes
Lost value, crop loss, and natural resource claims
Qualifications
Related Specialties
FAQ
Look for an environmental scientist or engineer with field and permit experience. For wetlands jurisdiction, look for wetland science training. Check whether the state requires a professional engineer or geologist license for the work. Ask how the expert ruled out other sources.
Sackett v. EPA held that waters refers to geographic features described in ordinary parlance as streams, oceans, rivers, and lakes, and adjacent wetlands indistinguishable from them due to a continuous surface connection. EPA reports two regimes applying by state, and further rulemaking was pending when this page was prepared, so confirm the current rule.
Sometimes. County of Maui held that a permit is required for a direct discharge from a point source into navigable waters or the functional equivalent of a direct discharge. Time and distance are the most important factors in most cases, along with the material the pollutant passes through and how it changes on the way.
Under the Clean Water Act, any citizen may commence a civil action subject to stated limits, and must generally give 60 days' notice to EPA, the state, and the alleged violator. A court may award costs of litigation, including reasonable attorney and expert witness fees. State tort claims may also apply.
An expert defines the extent of contamination, compares it with background and applicable screening levels, and estimates cleanup cost and time. A real estate appraiser may address reduced value, including whether the effect is temporary or permanent. The measure of damages depends on state law.
In general, water pollution expert fees are determined by the expert themselves, based on a variety of criteria. Among those criteria are technical experience, forensic experience, fieldwork needs, sampling costs, and publications. Vident does have some influence over expert fees by comparing experts within a specialty, but ultimately it is a personal decision by the expert.
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