Other Recent Additions
Posted: March 2, 2015
This issue highlights approaches for improving and streamlining site cleanup through a broad strategy that begins with upfront planning with an eye toward project completion, as described in the U.S. EPA's fiscal year 2014 Superfund Remedial Program Review Action Plan. EPA's plan describes short- as well as long-term measures and activities the Agency is undertaking to maintain an effective remedial cleanup program under Superfund program budget constraints. An important component of the plan is the use of an adaptive management process-an iterative approach to site investigation and remedy implementation that facilitates responding to new information and conditions throughout the lifecycle of a site. The plan also focuses on assessment, study, design and construction phases of the remedial process and outlines modified priorities for related resource management to be combined with additional increases in efficiencies. The projects featured in this issue illustrate ways to more effectively compile information as part of optimizing the design, implementation and monitoring of remedies and to strategically schedule key activities accordingly.
Posted: March 2, 2015
The March 19 session in the SERDP and ESTCP webinar series will focus on developing a quantitative framework for selecting bioremediation approaches at chlorinated solvent sites. Dr. John Wilson and Ms. Carmen Lebron will give presentations on an ESTCP-funded project where data from more than 90 sites were evaluated to establish correlations between naturally attained rate constants and the abundance of specific parameters. A framework was then developed into an easy-to-apply screening tool for use at sites contaminated by chlorinated solvents.
Posted: February 10, 2015
These case studies provide examples of the use of multiple technologies to develop remedial approaches that address contamination resulting from the release to the subsurface of non-aqueous phase liquids (NAPLs) and other chemical species. Combining remedy approaches can be a two-part process. The first part ensures that the chosen technology or technologies are the ones best suited for the problem both initially and as the cleanup process evolves. The second part of the process is observational. It recognizes that the continued application of a cleanup technology in and of itself changes the subsurface conditions from the conditions that were present when the technology was first applied. Monitoring data need to be evaluated periodically to ensure that the original technology is still the most effective option for the current conditions and is not simply operating as designed. Combined remedies and/or treatment trains are deployed most effectively when the hydrogeological and chemical contaminant conditions in the subsurface are well defined. EPA has developed the Triad approach to gather data more cost effectively and recommends using tools that provide for high-resolution site characterization.
Posted: February 2, 2015
The U.S. EPA Office of Superfund Remediation and Technology Innovation released a report in 2014 that highlights select mining-influenced water (MIW) treatment technologies used or piloted as part of remediation efforts at mine sites. The Reference Guide to Treatment Technologies for Mining-Influenced Water includes short descriptions of treatment technologies and information on the contaminants treated, pre-treatment requirements, long-term maintenance needs, performance, and costs. Sample sites illustrate considerations associated with selecting a technology. Website links and sources for more information on each topic are also included. This online, searchable database lists technologies provided in Appendix A of the Reference Guide to Treatment Technologies for Mining-Influenced Water, which includes summary information for the technologies discussed in the body of the report, as well as additional technologies or products designed as passive or low cost treatment options.
Posted: January 20, 2015
Environmental impacts from historical smelting operations are present within and outside the site of the former ASARCO smelter (El Paso, Texas). In Parker Brothers Arroyo, the site contractor completed construction of two in situ zero-valent iron (ZVI)-based permeable reactive barriers (PRBs) in October 2012 and the performance monitoring network in June 2013. This status report presents construction details for the PRBs with subsequent performance results. The objectives of the field demonstration are to verify the effectiveness of the ZVI PRB technology for concentrations of arsenic, antimony, selenium, and thallium above regulatory requirements at this site, initiate groundwater remediation, and provide data to support the final site-wide groundwater remedy.
Posted: February 4, 2015
A demonstration of the use of shear-thinning fluid based technology to improve treatment within low-permeability (low-k) zones of heterogeneous subsurface environments was conducted in a test cell within the Area D TCE plume at Joint Base Lewis-McChord. Low-k zones, which can serve as a long-term secondary source of contamination when transport is diffusion-controlled, are difficult to target using standard injection-based treatment approaches. A shear-thinning fluid can be used to distribute a bioremediation amendment (e.g., lactate) around an injection well such that the solution achieves better penetration and delivers the amendments to zones of both high and low permeability. When injected at a relatively high velocity compared to natural groundwater flow velocities, the shear-thinning nature of the solution allows it to flow more readily, promoting cross-flow from high- to low-permeability zones. During the demonstration, the shear-thinning fluid improved amendment distribution by ~41% with enhanced persistence and treatment effectiveness within the lower-k zones of the heterogeneous aquifer. It is anticipated that permeability contrasts of 1-2 orders of magnitude are amenable to this technology (e.g., improving distribution to silt layers within a sand matrix, but not clay layers). Field work started in August 2013, and performance monitoring events were completed in February and May 2014.
Posted: February 4, 2015
One of the major limitations to the effectiveness of in situ bioremediation is that performance is dependent on effective amendment delivery. Practitioners generally have little knowledge of the subsurface distribution of amendments, however, and substantial uncertainty can arise about whether treatment design criteria have been met, or if (and where and when) additional injections are required. Uncertainty is addressed through dense sampling or through overly conservative remedial efforts, both of which are costly. The performance objectives of this technology demonstration were to show that automated electrical geophysical monitoring can be used as an alternative to existing methods to provide timely, volumetric, and cost-effective information on spatiotemporal behavior of amendments used in enhanced bioremediation. These objectives included quantitative and qualitative measures. Quantitative measures were formulated in terms of spatial resolution, temporal resolution, and data-processing time/turnaround. Qualitative measures pertained to timely delivery of actionable information to scientists/engineers in the field and the ability of geophysical monitoring to map amendment behavior.
Posted: February 4, 2015
This report proposes a systematic framework for developing and maintaining acid mine drainage (AMD) projects. It lists things to try when developing new projects, observing completed projects, or coming back to projects with problems. Successes and failures in passive AMD treatment systems have led to improvements in design of treatment measures, rules for selecting and sizing them, and methods to refurbish them when needed. A lifespan of 20 years is rare, but several projects have done well for five to seven years, lost efficacy, and resumed function after rejuvenation. This report aims to encourage watershed groups to develop plans for project operation and maintenance and resources to carry out those plans.