Thousands of sites in the United States and around the World are contaminated with petroleum hydrocarbons, volatile organic compounds, including chlorinated solvents and their breakdown products, and other substances. Unfortunately, the financial resources available to remediate these sites have been stretched to their limits. As a result, intrusive and expensive remediation projects can only be justified at sites with a present or impending risk to human health or the environment.
Many regulatory agencies have now issued more flexible cleanup standards which promote a risk-based approach to remediation. In 1995, the American Society for Testing and Materials released a Standard for Risk-Based Remediation that has gained acceptance, particularly among State agencies responsible for petroleum hydrocarbon spills. The success of the risk-based approach depends on many factors including careful site characterization, an evaluation of existing site characterization data, scientifically defensible evaluation of natural attenuation processes, and proper selection of effective low-cost remediation technologies.
T.H. Wiedemeier & Associate’s (THWA) approach to remediation is risk based. We believe that the decision to remediate a contaminated site and the degree of remediation required should be based on the present and predicted risk that chemicals pose to human health and the environment. This risk-based approach to remediation differs from the conventional assessment and remediation process by more efficiently integrating site investigation, risk analysis, and feasibility assessments into a single step. As a result, the entire assessment and remediation process focuses on how best to address actual, or perceived, site risks rather than becoming mired in an exhaustive analysis of how to return a site to an unrealistic “pristine” state. THWA is interested in assisting our clients in implementing this approach at contaminated sites.
For those sites where active remediation is required, THWA has extensive experience in evaluating and installing both proven and innovative remediation approaches. For example, in 1998, Mr. Todd Wiedemeier was the first person in the world to inject vegetable oil to stimulate the reductive dechlorination of chlorinated solvents in the subsurface. Since that time, vegetable oil injection has taken on many forms, including injection as neat vegetable oil as well as emulsions of vegetable oil with various nutrients and buffers added. This approach has developed into a go-to approach for remediating chlorinated solvents.
T.H. Wiedemeier & Associates is currently involved in providing innovative ways to quantify abiotic degradation of chlorinated ethylenes by reaction with magnetite. Specifically, THWA recently benchmarked the use of a downhole sonde (probe) that can be used in PVC or other wells constructed of non-iron or -steel bearing well materials (Wiedemeier et al., 2017, GWMR, In Press). This work resulted as a natural offshoot from ESTCP Project ER-201129, when it became obvious that the majority of sites did not have data that could be used to quantify degradation on magnetite. The Publications and Downloads page of this website contains the technical report for ER-201129 Development and Validation of a Quantitative Framework and Management Expectation Tool for the Selection of Bioremediation Approaches at Chlorinated Ethene Sites. This publication contains a decision framework (flowchart) that allows the reader to deduce degradation pathways for the chlorinated ethylenes. The Publications and Downloads page also contains the BioPIC Tool, which allows the user to "walk" through the decision framework presented in ER-201129 in a logical manner.