ICON Environmental Services News

Subsurface Assessment Using Innovative Technology US NAVY, Jacksonville, FL

Developed innovative procedure for subsurface assessment utilizing direct push methods. Lithology was determined through sealed casing using borehole geophysics. A small diameter permanent direct push well (DPW) was installed through the sealed casing, and included proper grout to surface. Two sites were characterized using the new technology, and using conventional technology. The results of the two methods were compared, and results were presented to the FDEP and EPA, and were used to fulfill contaminant investigation requirements as per the site HSWA permit. US Patent Pending. This comparison indicated:

  • Excellent correlation of through-casing natural gamma logs to core samples at each site.

  • Laboratory results for DPWs were approximately 20% to 30% higher as compared to samples concurrently acquired from adjacent conventional wells, but intrawell variability upon resampling all DPWs and conventional wells was approximately 50%. Laboratory and/or sampling variability was higher than variability between DPWs and the conventional wells.

  • Field-measured groundwater turbidity was evaluated because the DPWs rely on development of native soils for a filter pack. The maximum observed difference in turbidity in twinned DPW/conventional wells was 3 NTU. Most DPWs yielded samples less than 14 NTU, with a few higher readings in DPWs installed in carbonate/shell zones.

  • The difference in field-measured groundwater specific conductance readings in twinned DPW/conventional wells was within 6.5%.

  • Hydraulic head in twinned DPW/conventional wells were within 0.03 feet NVGD.

  • The actual volume of grout used compared to the calculated annular volume at each DPW was 1.05 to 3.5 times the calculated annular volume. This suggests that an excellent seal was installed.

  • Hydraulic conductivity testing conducted in twinned DPW/conventional wells, calculated using the Bouwer and Rice method of data evaluation yielded hydraulic conductivity values for DPWs 20% to 50% lower as compared to conventional wells. Drawdown data of the DPWs lacked the characteristic filter sand drainage curve inflection commonly observed in conventional well data, allowing a more reliable curve pick for calculations.

  • The implementation was successful, even in very dense sands (>200 blows/foot).

  • Costs, including materials, labor and equipment for installation, and IDW and are dependent on the site-specific geology. Costs at the site with dense beach sands averaged 75% less than conventional wells, and at the site with silt/clay backswamp sediments averaged 82% of less than conventional wells.

Risk Assessment, North Louisiana Refinery

All historical environmental data ever generated at the refinery was validated and a database was created. Boring logs from environmental and geotechnical borings was used to develop a site-specific fate and transport model, to which resulting historical constituent concentrations at the point of exposure were evaluated using the Louisiana RECAP protocol. Project tasks pending regulatory review include additional assessment and more rigorous RECAP evaluation.

Deep Subsurface Assessment, Baton Rouge Area Oil Drilling Location

Annular disposal of drilling fluids at a zone 3200 feet below land surface resulted in some surface breaching several hundred yards from the wellhead. ICON designed and installed a 3100 foot deep well, had the boring geophysically logged and tested all significant aquifers between 3100 feet and ground surface. Each aquifer was tested by perforating the zone, acquiring samples, setting a bridge plug beneath the next shallower zone and cementing beneath the plug prior to perforating the next shallower zone. All area water wells were sampled. The project indicated only minor impacts to surrounding soils associated with fluid migration through zones of poor integrity of the casing cement.