Four of Weston’s top remediation professionals, Client Account Manager, Jeff Henke; Practice Leader- Vapor Intrusion/Project Manager, Ryan Wahl; Client Account Director, Pixie Newman; and Project Geoscientist, Shaun Cwick attended the Remediation Technology (REMTEC) Summit in February 2019.
Weston has company-wide Technical Communities of Practice (COPs) that provide the ideal communication platform to connect employees where we grow our technical excellence by sharing best practices and pool our resources to deliver what each project requires. Employees gain exposure to diverse projects throughout Weston through these COPs and share knowledge with others working through similar technical challenges. We stay attuned to regulatory updates, take the lead to anticipate future guidance, and proactively implement services today so that our clients are in compliance tomorrow. We use external conference forums to extract the latest in key technical areas to share within our COPs, across our clients, and the market in general. REMTEC moved us forward on this path via sessions covering hot remediation topics: Non-aqueous phase liquid (NAPL) Recovery Optimization, High-Resolution In-Situ Site Characterization, Data Management, Vapor Intrusion, and PFAS.
NAPL Recovery Optimization
In recent years there has been a renewed emphasis on effective, efficient removal of NAPL in subsurface media, in part owing to continued progress in distributing the science and engineering laid out in the Interstate Technology and Regulatory Council (ITRC) guidance and other associated national-scale guidance documents. Natural Source Zone Depletion (NSZD) is recognized as a major factor in reducing NAPL mass in the subsurface, with continued improvements in the methods used to determine NSZD rates. Renewed emphasis is also on reinvigorating Conceptual Site Models (CSMs) relating to NAPL, including such parameters as light non-aqueous phase liquid (LNAPL) transmissivity distribution, 3-D geologic models, and using hi-resolution subsurface characterization.
Weston scientists and engineers are proficient with the data collection, analysis, and presentation tools that will drive your NAPL challenges to a remediation endpoint.
High-Resolution In-Situ Site Characterization
The use of high-resolution, multi-tool probes combined with direct-push drilling techniques is becoming more frequently used in the industry. Traditional soil coring and observer-based geologic logging is recognized as limited when dealing with precise characterization of geologic materials, NAPL distribution, and saturation profiles. In addition, data management and data visualization technology are advancing to support more real-time analysis of the datasets and flexible management of investigations. The cost of these multi-probe investigations are typically higher than for traditional methods, but the substantial additional value provided by a continuous vertical record and fine-scale resolution of multiple chemical indicator parameters is recognized, especially at sites where progress has stagnated or substantial risk remains unqualified as a result of inadequate subsurface data. Real-time soil redox for mapping cyclical LNAPL degradation is also recognized as a promising innovative data collection tool, as well as ceramic down-well samplers that allow groundwater to be sampled where it is in contact with LNAPL or DNAPL.
Weston scientists and engineers are proficient in the sampling design, implementation, and optimization of these advanced tools and can accelerate your progress to closure.
Several speakers discussed an increased interest in better collection and use of more data and Big Data analytics on remediation projects. The era of Big Data has arrived in remediation. Integration of traditional data (boring logs, sample data) with digital data, multi-probe data, and project management data, such as correspondence, orders, maps and notes—all in one database and available to view and review in a GIS format for spatially-related viewing.
Weston programmers and data management experts are highly proficient in capturing, organizing, and presenting client data in ways that drive project effectiveness. In fact, our Information Management team recently developed a tool that provides a robust modularized dashboard that displays real-time progress as tasks are completed and is adaptable to many of our service applications, including Remediation, Fuels, Emission Testing, Emergency Response, Logistics, and others.
The United States Environmental Protection Agency (USEPA) conducts ongoing attenuation studies, which often result in more cautious screening levels. State regulatory agencies are encouraging investigators to consider the variability of evolving Vapor Intrusion screening guidance over time. This can be critical during site strategy and remedy decisions where historic trends indicate more stringent action levels over time. Analytical concentrations that do not trigger further action today can become an issue if an applicable standard decreases below the same concentration that was once acceptable. Precautionary measures, such as the installation of a mitigation system, can be the most cost-effective remedy during the new construction of properties with regulations continually changing regarding acceptable indoor air quality.
Indoor air volatile organic compound (VOC) sources provide ongoing challenges with Vapor Intrusion investigations. Building VOC sources can be invisible, non-removable, and in many circumstances, only detectable intermittently because of many variables. Recent research demonstrates that Paraffin, Isoparaffin, Aromatic, Naphthene, Olefin (P-I-A-N-O) analysis can be used as a forensic tool to provide a line of evidence. The analysis can provide different signatures in the indoor air and sub-slab vapor to determine if a correlation exists between detected contaminants.
A well supported CSM based on multiple lines of evidence is essential to moving beyond initial screening levels. A comprehensive CSM can include the evaluation of project components such as the source, concentrations, geology, hydrology, weather, building, and HVAC system, for example. Understanding building pressure is key because negative pressure induces Vapor Intrusion and positive pressure inhibits Vapor Intrusion. Measurements of indoor air should be collected during seasonal and temperature variability to identify different building pressure conditions. Indoor air concentrations collected during times of negative building pressure should be used for risk characterization.
PFAS emerging contaminants are receiving a great deal of attention because of their potential toxicity at low concentrations. Their ubiquitous nature, solubility, and the lack of approved testing methodologies for environmental media contributes to the challenges. Although health advisory values have been set by the EPA for subsets of this suite of 4,000+ constituents in drinking water, EPA recognizes this is not enough. Over the next couple of years, EPA has committed to working on multiple fronts—strategy development, research and risk communication, and creating tools to assist states, tribes, and communities (ranging from possibly adding PFAS to the Toxic Chemicals Inventory list to approving testing methodologies and setting cleanup standards). Many states are moving ahead with their own standards. Public and private entities are implementing testing and mitigation/remedial actions to limit the spread of these constituents in the environment. In Australia, the government is aggressively moving forward on sites it controls. According to ITRC’s special session on PFAS (conducted immediately after the conference), there are no “silver bullets” for remediation in place. Groundwater extraction and treatment by Granular Activated Carbon (GAC), membrane filtration, or ion exchange are being used as interim measures to protect drinking water supplies and integrated into existing treatment trains to remove PFAS. Excavation and incineration or containment of soil is being implemented while the remediation community waits for additional treatment technologies to be developed and verified.
Weston is working closely with laboratories and the regulatory community to refine workable approaches to testing methodologies while monitoring progress on new technologies to address PFAS in more effective and efficient ways. As a recognized leader in PFAS investigation and remediation, we are advancing knowledge in this arena that will prove helpful for all of our clients and advance the topic for our industry.