As the leaves change and the excitement of football season fills the air, we welcome the arrival of fall! With Thanksgiving approaching, we want to take a moment to express our heartfelt gratitude to all our clients who have trusted us with their projects this year.
We invite you to read about an intriguing project we recently completed. Additionally, don’t miss our upcoming webinar next week as part of our fall series. We’ll be discussing heavy metals remediation, where we’ll share valuable insights and remediation options.
Optimization and Modification of Remedial Design through qHRSC for a Large, Complex Combined Remedy Project
Project Overview AST’s scope of work for this project included quantitative High Resolution Site CharacterizationAbreeviated as qHRSC. High-resolution quantitative groundwater and soil sampling and analysis, geophysical methods, and aquifer characterization are combined to develop... (qHRSC), development of a 3-dimensional (3D) Conceptual Site ModelAbbreviated as CSM. The conceptual site model (CSM) is the communication tool that presents the understanding of the fate and... (CSM), CAT 100 injections, excavation and disposal of over 14,000 tons of arsenic-impacted soil, and construction of a 2-foot (ft) soil cover.
Historical operations at the manufacturing facility in the Midwest (USA) led to the release of trichloroethylene (TCE) into groundwater and arsenic into shallow soil (<2 ft below grade). The near-surface soil consists of clay fill with sand lenses, and groundwater is approximately 8 ft below grade, flowing north-northeast.
Remedial Design CharacterizationAbbreviated as RDC. One of the most common mistakes that leads to an unsuccessful remediation program is an inaccurate and... (RDC) From July 2022 to July 2023, three phases of RDC sampling activities were conducted (see figures below). The iterative RDC process identified data gaps and delineated the horizontal and vertical extents of TCE (and daughter product) impacts in groundwater and saturated soil, as well as potential source areas. A total of 551 soil samples and 110 groundwater samples were collected and analyzed across the three RDC phases. All samples were analyzed at the RPI Project Support Laboratory at no additional cost to the project.
qHRSC Model Insights The qHRSC model identified an additional source area with significantly higher TCE concentration and mass than initially identified in earlier investigations—800 µg/L TCE using traditional methods versus 300,000 µg/L using the qHRSC process. Without the qHRSC, this additional source area would have gone undetected, jeopardizing the success of groundwater remediation at the site.
CAT 100CAT 100 is a fusion of RPI’s BOS 100® and biotechnology to produce technology capable of achieving results beyond the capabilities... Treatment Implementation The CAT 100 treatment area (see figure below) was defined using data from the phased RDC process and qHRSC models developed by AST. Amendments were applied via direct push injections on a 6 ft or 7.5 ft spacing within an approximate 51,000 ft² area. Since this project was recently implemented, the data set is immature – however initial TCE and daughter product groundwater concentrations in the most impacted monitoring well have been reduced by 89-99% to date.
Further Learning Opportunity While this newsletter focuses on the delineation and remediation of TCE and its daughter products, we invite you to join us next week for our upcoming webinar in the fall series: “Mackinawite Structured Iron Sulfide for Heavy Metals Remediation: Abiotic vs. Biotic Formation and Case Studies“, where we’ll discuss treatment options for heavy metals such as arsenic and chromium.
AST would like to thank and acknowledge our clients for this project – Richard Christensen, PhD and Steven Irvin of Acuity Environmental Solutions.
The left and center images represent the TCE concentrations in groundwater and soil and the right image represents the injection area layout. The reagent loadings varied in the treatment areas based on the mass detected during the RDC and modeling.
This image represents the B-B’ cross section (yellow North/South line on the site map). This figure was created using the vertical soil profiling data generated during he RDC phases.
