HAZARDOUS WASTE SITE ASSESSMENT
Using the USEPA Flux Chamber Technology to Perform Air Pathway Assessments (APA) Supporting Remedial Investigations and Feasibility Studies at Hazardous Waste Sites
Site air emission assessments conducted at hazardous waste sites are typically performed during the Remedial Investigation (RI) phase of the program, and are often referred to as an Air Pathway Analysis (APA). Like the focus of RI work, the APA includes site assessment in order to understand the nature of the air emissions from the waste material (source characterization), but it also includes assessing the migration of the gas phase or particulate matter emissions from the source (hazardous waste) to the environment, specifically to workers on site and to occupants in structures off site.
Assessment using the USEPA flux chamber technology generates emission rate data which can be used as input to a dispersion model in order to predict potential impact to the surrounding community before, during, and after site remediation. Surface characterization typically involves assessing the air emissions from the waste material as found or in the 'baseline condition' using the USEPA surface emission flux chamber (photo 1).
In addition, the APA can include assessing air emissions from the waste material as it may be disturbed during site remedial activities (photo 2). This emission factor data set is very useful and necessary for the process of site remediation. Subsurface waste material can be access by 'dental' excavation if the waste is close to the surface (photo 3) and tested using the surface flux chamber. Trenching is often performed to test for buried waste in conjunction with observation, inspection, and bulk sample collection (photo 4). Buried waste can also be accessed using the USEPA downhole flux chamber technology (photo 5).
The advantage of the downhole flux chamber assessment is that this test can be performed at the same time and in the same hollow stem boring as a geologic investigation; likewise it can utilize the same boring as a groundwater well installation. Further, there is little concern that an unacceptable air release will occur during the downhole flux chamber assessment activity provided that cuttings are picked-up and drummed during the assessment, and good-house keeping practices are followed. That isn't always the case with a trenching activity.
The APA can include solid, sludge (photo 6), or liquid hazardous waste material, and these assessments often include assessing contaminated soils and groundwater associated with the hazardous waste materials. A variety of chemical species can be tested for during RI APA activities, including a host of VOCs, SVOCs, and inorganic compounds. Typically regulatory accepted methods are used, and laboratories capable of producing contract laboratory program (CLP) data deliverables that work within analytical method specifications are employed. APA data are a vital component of any complete and successful RI program.
Photo 1. Flux Chamber testing to Identify the 'Hot' Emission Zones
Photo 2. Air Pathway Analysis Includes Assessing Average and Maximum Emissions
Photo 3. Flux Chamber Testing of Petroleum-Based Hazardous Material Beneath Synthetic Cover for Feasibility Study
Photo 4. Flux Chamber Testing on Treated Solid Hazardous Waste
Photo 6. Flux Chamber Testing on Hazardous Petroleum Lagoon
Photo 5. Downhole Flux Chamber Testing in Hollow Stem Auger