Surface Water Contaminant Transport

Exponent has gained a strong reputation for solving technically challenging environmental and water resource problems involving groundwater, surface water, and vadose-zone systems. Our comprehensive understanding of the physical and chemical intricacies throughout the entire water cycle allows us to address our clients' water-related problems accurately and efficiently.

Our services include:

  • Water quality modeling (rivers, lakes, reservoirs, estuaries)
  • Sediment transport modeling (rivers, lakes, reservoirs, estuaries)
  • Stormwater runoff modeling
  • Outfall dispersion modeling
  • Watershed and basin-scale hydrological modeling and management 
  • Nutrient and veterinary pharmaceutical runoff analyses 
  • Offshore aquaculture impact analyses
  • Sediment remediation cost allocation
  • Historical reconstruction
  • Natural resource damage assessment
  • Water supply reliability and resource planning and management 

The transport and fate of contaminants in surface water systems must be understood to evaluate the potential impacts to water and sediment quality, to select appropriate remedies, and to effectively manage water resources. Exponent has extensive experience in analysis of surface water quality and contaminant transport in both litigation and non-litigation projects. Exponent scientists and engineers have evaluated dispersion and fate of discharges from existing or proposed wastewater outfalls, water quality conditions in existing and proposed reservoirs, basin-wide impacts of nonpoint source runoff, impacts of natural and man-made hydrologic changes on water quality, and alternative water resource management strategies.

In litigation cases, the nature of contaminated sediment deposition is often a central issue in certification of class action toxic tort claims while the extent of contaminant deposition is a key component of determining contaminant exposure in individual claims. An analysis of the contaminant transport pathway is often essential to establishing a linkage between the contaminant source(s) and receptors in class action and individual claims, as well as in source apportionment studies.

In addition to strong capabilities in hydrodynamics and in sediment and contaminant transport modeling, Exponent staff have been pioneers in the utilization of tracers and chemical fingerprints and in the use of environmental forensics tools, as complementary or as stand-alone approaches to resolve linkage questions. A tracer is any substance that is associated with the alleged source and whose transport characteristics are the same as the contaminant that is the subject of the investigation. For example, caffeine can be a tracer for municipal sewage. A specific dioxin or furan congener uniquely associated with an industrial process can be an effective tracer. Isotopic ratios of metals, such as mercury, lead, and zinc can also be used as tracers. A chemical fingerprint is similar to a tracer, but focuses on the unique assemblage (fingerprint) of specific chemical compounds that make up organic contaminants such as petroleum hydrocarbons, PCBs, dioxins and furans, or brominated flame retardants.

Exponent's scientists and engineers provide clients with clear answers and real solutions to their water resource problems. We start with quality assessment and effective management of project data. We use accepted, appropriate tools, including models of hydrodynamics, water and sediment quality, and geochemistry; geographic information systems; bench- and pilot-scale experiments; and focused field studies, to address site-specific issues.

Exponent places a premium on presenting our work clearly and understandably, and we are known for our ability to present complex technical findings using concise language and clear graphics that are tailored to the audience. We use a variety of media to present our work, ranging from traditional written reports to oral presentations to detailed graphics and computer animations, depending on the nature of the issue and the target audience. Exponent works with clients to convey information that promotes understanding and acceptance to regulatory agencies and the public. In addition, Exponent has worked closely with attorneys to provide valuable expert witness testimony during trial, deposition, arbitration, and alternative dispute resolution proceedings.