Soil bioventing is one of the most popular modern techniques for removing contaminants from soil. It has recently emerged as one of the most cost-effective and efficient technologies available for vadose zone remediation of petroleum-contaminated sites. This book explains in practical terms how to carry out a bioventing program. It is an interdisciplinary treatment of the subject, covering everything from basic physical and chemical properties of soils to site evaluation, project design, and post-bioventing monitoring.The wide breadth of coverage makes Soil Bioventing useful to a large audience, including consulting firms, students, contractors, environmental managers, and anyone who is responsible for supervision of soil cleanup for regulatory reasons.

1,4‐Dioxane is a volatile organic compound that is fully miscible in water, allowing it to sequester in vadose zone pore water and serve as a long‐term source of groundwater contamination. Conventional soil vapor extraction (SVE) removes 1,4‐dioxane; however, substantial 1,4‐dioxane can remain even after other colocated chlorinated solvents have been remediated. A field demonstration of “enhanced SVE” (XSVE) with focused extraction and heated injection was conducted at former McClellan AFB, CA, achieving 94% reduction in soil concentrations. A screening‐level tool, HypeVent XSVE, was created to assist in system design and data reduction and to anticipate how operating factors affect XSVE performance (e.g., cleanup level, remediation time, etc.). It assumes well‐mixed conditions, and combines an energy balance, mass balances for water and contaminant, and a temperature‐dependent 1,4‐dioxane Henry's Law constant. User inputs include the target treatment zone size, initial 1,4‐dioxane and soil moisture concentrations, and ambient site and injection/extraction conditions (temperature, humidity). Projections based on inputs representative of demonstration site conditions adequately anticipated the observed macroscopic field results. Sensitivity analyses show that removal increases with increasing heated air injection temperature and relative humidity and decreasing initial soil moisture content.

1,4-Dioxane is totally miscible in water, sequestering in vadose pore water that can serve as a source of long-term groundwater contamination. Although some 1,4-dioxane is removed by conventional soil vapor extraction (SVE), remediation is typically inefficient. SVE efficiency is hindered by low Henry's Law constants at ambient temperature and redistribution to vadose pore water if SVE wells pull 1,4-dioxane vapors across previously clean soil. It was hypothesized that heated air injection and more focused SVE extraction (Enhanced SVE or XSVE) could increase the efficiency of 1,4-dioxane vadose treatment, and this new process was tested at former McClellan Air Force Base, CA. The XSVE system had four peripheral heated air injection wells surrounding a 6.1m x 6.1m x 9.1m deep treatment zone with a central vapor extraction well. After 14months of operation, soil temperatures reached as high as similar to 90 degrees C near the injection wells and the treatment zone was flushed with similar to 20,000 pore volumes of injected air. Post-treatment sampling results showed reductions of similar to 94% in 1,4-dioxane and similar to 45% in soil moisture. Given the simplicity of the remediation system components and the promising demonstration test results, XSVE has the potential to be a cost-effective remediation option for vadose zone soil containing 1,4-dioxane.

Soil gas sampling for 1,4‐dioxane at elevated soil temperatures, such as those experienced during in‐situ thermal treatment, has the potential to yield low results due to condensation of water vapor in the ambient temperature sampling vessel and the partitioning of 1,4‐dioxane into that condensate. A simple vapor/condensate sampling apparatus was developed to collect both condensate and vapor samples to allow for determination of a reconstituted effective soil gas concentration for 1,4‐dioxane. Results using the vapor/condensate sampling apparatus during a heated air injection SVE field demonstration are presented, along with those of a comparable laboratory system. Substantial 1,4‐dioxane mass was found in the condensate in both the lab and field (as high as ~50% in field). As soil temperatures increased, less 1,4‐dioxane mass was detected in field condensate samples than expected based on laboratory experiments. Extraction well effluent sampling at the wellhead by direct vapor canister sampling provided erratic results (several biased low by a factor of 5 or more) compared to those of the vapor/condensate apparatus. Direct vapor canister sampling of extraction well effluent after the air‐water separator, however, provided results reasonably comparable (within 35%) to those using the vapor/condensate apparatus at the wellhead. Soil gas sampling at elevated temperatures using the vapor/condensate apparatus alleviates potential low sampling bias due to condensation.

Abstract : This project demonstrated a paradigm for assessing source zone natural attenuation (SZNA) at chlorinated aliphatic hydrocarbon (CAH) impacted sites. SZNA is often used as a basis for assessing the performance and relative benefits of engineered remediation and is also a component of the cleanup strategy at most CAH-impacted sites. Thus there is a need for a well-defined and accepted assessment approach. The data-driven method anticipates that decision makers will be interested in the following questions: 1-Is SZNA occurring and what processes contribute?; 2-What are the current SZNA rates?; and 3-What are the longer-term implications of SZNA? The approach uses multiple lines-of-evidence and macroscopic mass balances, and these lead to confirmation of SZNA and quantification of the total mass loss rate resulting from degradation, dissolved phase transport, and volatilization. Application of the approach was demonstrated at three CAH impacted sites through four events per site over about three years. The mass loss rates were relatively consistent over time for each site, but varied from site to site, ranging between about 1 10 kg/y at two sites and as high as about 600 kg/y at the third site. When applying the generalized CAH-SZNA method, it is likely that different practitioners will choose the number and locations of samples in different ways. For example, this could happen at a site over different sampling events. This then raises the question: Is the calculated SZNA mass loss rate likely to be dependent on the sampling strategy?, and if so, how should sampling plans be designed to ensure consistency in results across practitioners? As a result, the high spatial-density data collected from the demonstration sites in this project were used to examine the effect of different sampling strategies on the quantification of mass loss rates at those sites. That experience, and lessons-learned from previously published studies on this topic, were used as the basis for new

This article quantifies the nature, frequency, and cost of environmental remediation activities for onshore oil and gas operations, as determined from over 4,100 environmental remediation cases in Texas, Kansas, New Mexico, and Colorado. For the purpose of this article, "remediation" refers to cleanup efforts that entail longer-term site characterization, monitoring, and remedial action beyond the initial spill cleanup or emergency response stage. In addition, data are also also presented regarding short-term spill cleanup activities in two of the four states. (C) 2011 Wiley Periodicals, Inc.

: The following Frequently Asked Questions (FAQs) document provides a concise overview of current knowledge regarding management of subsurface chlorinated solvent releases. The envisioned audience is state regulators, federal regulators, consultants, Department of Defense (DOD) staff, and community members involved in selecting remedies for chlorinated solvent sites. In the interest of brevity, the FAQs and the companion document Guide for Selecting Remedies for Subsurface Releases of Chlorinated Solvents assume that the reader has a general understanding of hydrogeology, the movement of chemicals in porous media, remediation technologies, and the overall remedy selection process.