Rapid Assessment of Remedial Effectiveness and Rebound in Fractured Bedrock
ER-201330
Objective
The overall objective of this project is to develop and evaluate a novel “Push-Push” remedial assessment technique, coupled with compound specific isotope analysis (CSIA), for use as a rapid and cost-effective means to assess the limits of in situ remediation in fractured bedrock systems. This evaluation will be most relevant to evaluating the extent to which biological and chemical amendment delivery (e.g., biostimulation, chemical oxidation) can reduce groundwater concentrations for a given contact time and/or dosage. By carefully evaluating amendment distribution, rebound (in chlorinated solvent and isotopic signature), and isotopic analysis in both transmissive and low permeability zones, limits to remedial success will be identified early in the process, and the potential for contaminant rebound will be assessed without the need for long-term and costly testing.
Technology Description
Best suited for source areas where substantial DNAPL is not present, the Push-Push methodology is an adapted technique that is a hybrid of conventional push-pull tests coupled with the flushing and high-resolution sampling technique employed at Alameda Point in conjunction with SERDP project ER-1613. The Push-Push test involves the use of two wells: a standard injection well and a multilevel sampling (MLS) well located approximately 5 to 20 feet down-gradient of the injection well. Chemical oxidant (permanganate) is injected into the injection well, and oxidant distribution is measured in the MLS well. Permanganate reacts rapidly to oxidize tetrachloroethene (PCE) and trichloroethene (TCE) and will serve as a means to rapidly remove dissolved contaminants in conductive fractures. Since the purpose of the test is to measure rebound from mass-transfer limited zones, or from undissolved phases, the specific reaction employed (chemical or biological) is not expected to substantially impact the conclusions. After approximately 4 to 6 weeks of incubation to allow for oxidation of the contaminant, noncontaminated groundwater is injected into the injection well and contaminant concentrations are monitored in the MLS well to assess the extent of rebound. CSIA analyses on carbon are performed before, during, and after injection to determine the extent of reaction, as substantial isotopic fractionation of chlorinated solvents occurs due to reaction with permanganate. The changes in isotopic ratio, coupled with the observed contaminant rebound, will provide information regarding the fraction of mass treated, mass transfer limitations, rebound mechanisms (i.e., DNAPL versus back diffusion), and the potential benefits of additional remedial amendment injection or contact time. By using only two wells, and by performing the test within a relatively short time period (2 to 5 months), this approach offers substantial cost and time savings compared to conventional pilot testing approaches, especially in fractured bedrock.
Benefits
This demonstration is expected to provide the Department of Defense and stakeholders with management tools to improve the evaluation and treatment of contaminated plumes within fractured bedrock. By demonstrating this novel assessment technique and developing a protocol, a means to rapidly assess the limits of in situ remedial efforts will be realized. This will allow remedial strategies to be optimized, limits of remediation to be identified cost effectively, and improved estimates of natural attenuation time frames to be achieved. (Anticipated Project Completion - 2016)
Points of Contact
Principal Investigator
Dr. Charles Schaefer
Shaw Environmental, Inc.
Phone: 609-895-5372
Fax: 609-895-1858
Document Types
- Fact Sheet - Brief project summary with links to related documents and points of contact.
- Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
- Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
- Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
- Guidance - Instructional information on technical topics such as protocols and user’s guides.
- Workshop Report - Summary of workshop discussion and findings.
- Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
- Model/Software - Computer programs and applications available for download.
- Database - Digitally organized collection of data available to search and access.