Site Assessment, Design Considerations, and Performance Results from a Colloidal Activated Carbon Barrier Application at a Large Chlorinated Plume Regulated Under CERCLA
Carlos Ortiz, Senior Technical District Manager, REGENESIS
Tuesday, April 11, 2023, 11:45am-1pm
Hybrid Format – In person and virtual
CEMS has received one (1) general CLE credit for this presentation
A large chlorinated solvent plume situated in a sandstone bedrock aquifer and migrating under a residential neighborhood required a remedial strategy to be implemented to prevent further migration of the plume towards private water wells. Strategies considered included groundwater extraction, ERD, and an in situ colloidal activated carbon (CAC) barrier. Numerous water wells had dispersed the solute plume throughout the site, so arresting plume migration utilizing groundwater extraction for hydraulic control was ruled out. Of the technologies considered, a passive CAC barrier provided the most cost-effective, innovative solution to prevent biofouling of the downgradient potable wells that may develop from typical ERD in situ remedies. This presentation will discuss the importance of pre-application assessments, design considerations when implementing a CAC barrier, and performance results.
A passive barrier of colloidal activated carbon was applied using injection wells at the distal edge of a chlorinated solvent plume to prevent further contaminant migration into private water wells. Prior to the barrier application, extensive site characterization and application calibration were performed to determine the placement of injection wells and to optimize design parameters to ensure product delivery and performance. This included geophysical logging to clearly identify the target zone and determine the optimal placement of the screen. Once injection wells were emplaced, the wells were sampled using an innovative array of passive diffusion bags (PBDs) to vertically and horizontally profile the VOC distribution in the aquifer across the proposed barrier. Additionally, field calibration injection testing was conducted ahead of the application to confirm the injection porosity and optimize the injection rates necessary to achieve the required ROI for complete coverage of the product in the sandstone bedrock unit. Performance wells were installed to evaluate the contaminant concentrations entering and leaving the barrier.
The extensive site characterization that guided the injection well placement resulted in the barrier design being completed with 24 injection wells on 12.5 feet on-center well spacing. Results from the field injection calibrations and vertical passive sampling dialed in the injection volumes and product dosing design. Performance monitoring data over 15 months from 5 monitoring wells has shown excellent results from the CAC barrier, with the results meeting the project performance objectives (below MCLs) and preventing the downgradient migration of PCE. The presentation will include a comparison of performance monitoring data to a CAC predictive model developed using site specific conditions (i.e., groundwater velocity, degradation rates, etc.). The model was used to confirm long-term performance objectives compliance and optimize additional CAC applications at specific injection intervals for improved remediation performance.
Carlos Ortiz attended The Pennsylvania State University, where he received a BS in Earth Science.
Carlos has over 22 years of experience in the environmental field providing leadership and technical expertise in the areas of site assessment and characterization, analytical data interpretation, geological and hydrogeological analysis, environmental risk evaluation, soil and groundwater remedial plan evaluation, design, implementation and project management of insitu remediation projects. His experience includes projects in throughout the US, and internationally in Mexico, Puerto Rico and Nicaragua.
Carlos currently serves as the South Central District Senior Technical Manager with REGENESIS. In his capacity, Carlos works closely with environmental consulting, construction, and engineering firms to collaboratively develop successful remedial approaches for their clients by offering design, application, and performance review services for in-situ applied groundwater and soil remedial strategies across a broad spectrum of technology classes.
Fun Fact: While attending Penn State, Carlos balanced his time as a student-athlete as a member of the Men’s Volleyball team. His biggest accomplishment as a student-athlete was winning the NCAA Men’s Volleyball National Championship in 1994 and receiving All-American honors.
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