CEMS June Luncheon – Rapid Site Closure of a Large Gas Plant Using In-Situ Bioremediation Technology in Low-Permeability Soil and Fractured Bedrock – June 20
June 20 @ 11:30 am - 1:30 pm
Topic: Rapid Site Closure of a Large Gas Plant Using In-Situ Bioremediation Technology in Low-Permeability Soil and Fractured Bedrock
Speaker: Thomas A. Harp, P.G, P.E., Principal, Remediation Risk Reduction, LLC
Date/Time: Thursday, June 20, free lunch at 11:30am, presentation from 12:00-1:30pm (no 2nd Tuesday of the month meeting in June)
Location: Geotech Field Days, Geotech Environmental Equipment, 2650 East 40th Avenue, Denver, CO 80205 (parking is free)
Please note that this meeting occurs on Thursday, June 20 (not the second Tuesday of the month)
CEMS has received one (1) CLE for this presentation
Background/Objectives. Natural-gas condensate and other natural-gas liquids released to the subsurface from a large gas-processing plant generated a petroleum-hydrocarbon plume approximately 30 acres in area. The affected matrix was complex and included low permeability, residual clays overlying shallow, fractured limestone bedrock. Solute concentrations indicative of light-non-aqueous-phase-liquid (LNAPL) were observed at depths as shallow as 4 feet below ground surface. Undulating surface topography with paleo-channels (incised, erosional features) and a relatively steep groundwater gradient caused a dissolved-phase plume of benzene, toluene, ethybenzene, and xylenes (BTEX) to extend more than 1/4-mile downhill from the source. The Railroad Commission of Texas (RRC) was the agency providing regulatory oversight of the project. Closure criteria was established by the RRC.
Approach/Activities. The initial Remedial Action Plan prepared by a predecessor and submitted to the RRC was to install soil-vapor extraction and groundwater recovery and treatment systems to achieve site cleanup. Instead, an in-situ, carbon-based injection program was implemented to expedite remediation for a pending property sale. The remedy is a granular, activated carbon injectate inoculated with cultured microbes (consortia of facultative microorganisms), electron acceptors (nitrate and sulfate), and nutrients (phosphorus and nitrogen) designed to quickly biodegrade BTEX compounds.
Subtle facies changes in overlying, low-permeability soil and thin bedding planes and complex fractures in highly weathered bedrock resulted in solute concentrations that varied by orders-of-magnitude in distances of only several millimeters. The first step was to conduct a high-resolution, quantitative-data assessment to characterize plume strength and geometry. The outcome was an accurate conceptual site model used to: 1) apply (continuous) soil and groundwater data to design a discrete remedial design; 2) inject carbon-based slurry; 3) complete confirmatory/performance borings to observe remedy distribution and evaluate if “the target was hit” (or adjust subsequent injections, accordingly); 4) analyze corresponding groundwater samples; and 5) calculate mass reduction. This sequence was repeated until cleanup goals were met in a subject area.
The site was subdivided into six regions, based on constituent concentrations. Treatment was implemented in three phases over a 15-month period. Approximately 4,800 injections were completed at 1,230 locations throughout the 30-acre plume. The remedy consisted of 185,875 pounds of carbon slurry, 5,650 pounds of supplemental sulfate (gypsum), and 352 gallons of microbes.
Results/Lessons Learned. The project was a success because of the effectiveness of the carbon-based remedy and the quantity and quality of data gathered to demonstrate treatment performance. The primary petroleum constituent, benzene, was reduced from concentrations of over 70,000 micrograms per liter (µg/L), i.e., LNAPL, to less than 1 µg/L. Following 24 months of post-treatment groundwater monitoring, a No Further Action determination was issued for the site by the RRC.
Thomas Harp, P.G, P.E., has a B.S in Geology from Tulane University, an M.S in Civil Engineering in groundwater hydraulics and chemical transport from Colorado State University, and an M.B.A. from the University of Missouri. He’s a Principal at Remediation Risk Reduction, LLC. and has over 35 years of experience providing practicable solutions to issues related to contaminated soil and water. His expertise is in assessing and remediating petroleum and chlorinated hydrocarbon sites.
Location: CEMS hopes you will join us for our monthly meeting on Thursday, June 20 from during the 11th Annual Geotech Field Days. Lunch starts at noon, and our presentation will run from 12:30-1:30pm. Or, come for the day and check out some of the other interesting presentations during Field Days. Geotech Field Days Information
Please note we will not be having our regularly scheduled meeting in June. Please see the attachment below to register. CEMS members need to register for FREE with Geotech directly to attend our presentation. Geotech Field Days Registration Form
MEETING FORMAT: Attendance and lunch at Geotech Field Days is absolutely FREE! Detailed information for all Geotech Field Days presentations with abstracts are attached. Geotech Field Days – Abstracts (coming soon)
RESERVATIONS: You will need to directly register for the Geotech Field Days. CEMS will not be taking reservations this month. A registration form can be found attached below or by following this link: Geotech Field Days Registration Form
For more information regarding Geotech Field Days, please see this link: Geotech Field Days