Subgrade Biogeochemical Reactors: Design and Performance of Multiple Configurations

Monday, December 3, 2018: 11:20 a.m.
N119/120 (Las Vegas Convention Center)
Jeff Fitzgibbons, PG , Global Environmental Solutions, Jacobs, Englewood, CO
Jeff Gamlin, PG , Global Environmental Solutions, Jacobs, Englewood, CO

Subgrade biogeochemical reactors (SBGRs) are a unique green and sustainable remediation (GSR) technology for treatment of contaminant source areas and groundwater plume hot spots. SBGRs have been configured for multiple in situ treatment methods, including: enhanced reductive dechlorination (ERD), sulfate-enhanced degradation, and aerobic degradation. SBGRs have been used to effectively treat chlorinated volatile organic compounds (CVOCs) and/or fuel related contaminants in soil and groundwater, and treatment of other contaminants continues to be evaluated.

This technology is used to address persistent source area contamination at a lower cost and in a sustainable manner. SBGRs consist of the following common elements: 1) excavation of contaminated source area soils, 2) backfill of the excavation with gravel and SBGR amendments tailored to the contaminant(s) of concern, and 3) installation of a solar- or wind-powered pumping system to recirculate groundwater through the SBGR for treatment. Use of locally sourced farm and tree byproducts, reclaimed construction materials, along with off-grid groundwater pumping, creates a low-cost, low‑maintenance, and sustainable remediation solution.

SBGRs have been constructed in multiple configurations, including designs capable of meeting limited access restrictions at heavily industrialized sites or at sites with land surface disturbance restrictions due to sensitive species and wetland habitat issues. The SBGR treatment media has also been selected for multiple contaminants based on site-specific conditions. For ERD approaches at CVOC sites, SBGR treatment media have contained various types of organic mulch, new or recycled vegetable oil, iron pyrite, or magnetite sands. For fuel-related sites, SBGR treatment media have included recycled gypsum products for sulfate-enhanced degradation, or oxygen-enhancing amendments for aerobic degradation. This presentation will summarize the advantages and limitations of the SBGR technology. We will discuss performance results from several SBGRs, which are achieving 95-99% total molar reduction of contaminants and rapidly cleaning up contaminant source areas.

Jeff Fitzgibbons, PG, Global Environmental Solutions, Jacobs, Englewood, CO
Mr. Fitzgibbons is a geologist and remediation technologist with Jacobs in Denver, Colorado. He is a licensed professional geologist in Illinois and Nebraska and has over ten years of experience in subsurface investigation, characterization, and remediation of petroleum hydrocarbon and chlorinated solvent impacted sites.

Jeff Gamlin, PG, Global Environmental Solutions, Jacobs, Englewood, CO
Mr. Gamlin is a certified hydrogeologist and professional geologist who is Jacobs' subject matter expert (SME) for in situ remediation delivery method and leads Jacobs' subgrade biogeochemical reactor (SBGR) design group. Mr. Gamlin is a SME for bioremediation and biogeochemical remediation, remedial process optimization (RPO), molecular and biological diagnostic tools, optimized exit strategies, green and sustainable remediation design, emerging contaminants characterization and treatment, groundwater age dating and tracer studies, aquifer test design and analysis, wellfield design and well hydraulics, and aquifer storage and recovery (ASR) projects.