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MiHPT Case Study

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Modified version of MiHPT case study presented at Geoprobe\'s DI Seminar, April 18, 2012

Modified version of MiHPT case study presented at Geoprobe\'s DI Seminar, April 18, 2012


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  • 1. S2 C2 inc. High-Resolution Site Characterization Using MiHPT Logging to Optimize an Electrical Resistance Heating System Todd Morgan and Tom Koester
  • 2. S2 C2 inc. Site Location ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 3. S2 C2 inc. Site Location Investigation Area ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 4. S2 C2 inc. Cluster 13 Site History  1920s to 1950s – US Army Chemical School used site for chemical weapons testing  1,1,2,2-tetrachloroethane (TeCA) solvent used on-site for decontamination and laundry operations  Site removal actions and interviews verified dumping and accidental releases of TeCA occurred on-site ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 5. S2 C2 inc. Site Hydrogeology  Aquifer exists between fine-grained vadose zone and basal clay  Saturated material primarily silty sand • Silt/clay lenses and fine-grained materials throughout aquifer  Aquifer is thin and discontinuous in the north and east  Aquifer thickens southward in channels  Groundwater discharges through organic silt in northern and southern tributaries of Bush River ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 6. S2 C2 inc. Conceptual Hydrogeology ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 7. S2 C2 inc. MiHPT Technology  New combo of Geoprobe®’s Membrane Interface Probe (MIP) and Hydraulic Profiling Tool (HPT) – 2 field-verified and trusted direct- sensing technologies  MIP used to log VOCs in soil and groundwater  HPT used to log soil hydraulic properties  In a single push, the MiHPT practitioner can: • Detect impacted sub-surface material with respect to hydraulic conductivity • Identify contaminant preferential pathways • Target zones for remediation • Select appropriate designs for monitor well installation • Log up to 150 linear feet/day – the same rate as standalone MIP or HPT! ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 8. S2 C2 inc. Cluster 13 MiHPT Investigation  High-resolution data and confirmatory analytical data needed to optimize proposed electrical resistance heating (ERH) system  Prior Electrical Conductivity (EC) borings at times inadequately showed inter-fingered sands and silts  Regulatory agency required higher resolution data to prove the contaminant mass was bound up in fine-grained, low permeability materials  Sovereign Consulting contracted S2C2 to deploy the new MiHPT logging system  Doug Koehler (Geoprobe®-DI) on-site to assist with operation of new MiHPT probe and Acquisition software ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 9. S2 C2 inc. MiHPT Investigation Goals  Delineate vertical and horizontal extent of cVOC impacts  Determine cVOC impacts with respect to hydraulic conductivity  Identify depth and occurrence of basal clay unit  Identify the presence of the clay ridge transecting the site ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 10. S2 C2 inc. MiHPT Logging at Cluster 13 ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 11. S2 C2 inc. Limited Access MiHPT Logging ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 12. S2 C2 inc. Let’s take a look at some data…. ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 13. Little variation in EC values (range from ~10-15 mS/m) offers little insight into subsurface variation______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 14. HPT data shows these 3 areas of relatively equal EC values have distinctly different hydraulic properties______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 15. HPT data and dissipation tests used to estimate K______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 16. MIP detections found in low permeability soil. Groundwater sample from this interval had 11.3ppm total cVOC______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 17. Again, little variation in EC values may lead to the conclusion that the sub-surface material is somewhat homogeneous______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 18. HPT data shows two completely different hydraulic units______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 19. Estimated K derived from HPT data and dissipation tests shows very high permeability in upper unit and low permeability in lower unit______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 20. Highest MIP detections correspond with lowest permeability soil. Groundwater sample from deeper interval had 1216ppm total cVOC______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 21. This EC log appears to have two distinct units, the upper consisting of a primarily finer-grained material than the lower______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 22. Without the HPT data, the operator would likely conclude the upper, finer-grained unit would have a lower permeability than the deeper unit______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 23. When the K is estimated, we see that the opposite is true; the upper unit actually has a higher permeability than the lower unit______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 24. While MIP detections again occur in low permeability unit, the low hydraulic conductivity of the unit was confirmed when an attempt to collect groundwater yielded no water______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure
  • 25. S2 C2 inc. MiHPT Investigation Summary  17 MiHPT locations advanced to a depth of 40-50ft bgs  29 depth-discrete groundwater samples collected with SP22 to confirm MiHPT results  C Tech’s Mining Visualization Software used to visualize in 3-D the aquifer characteristics and contaminant distribution  Identified basal clay, clay ridge, and low permeability zones within the aquifer  ERH electrode configuration shifted to focus on southwest based on findings  Optimized ERH system currently in full implementation ______________________________________________________________________________________________________________________________________________________________ Streamlined Site Characterization and Closure