Theme: 01. Remediation Technology Innovations

Topic Area: 01r. Thermal Conductive Heating: Best Practices and Lessons Learned

Formatted Title:

It’s Dark Down There! Three-Dimensional Tracking of 196-foot Long Borings Used to Optimize ISTR Performance

Background/Objectives:

Thermal conduction heating (TCH) for a 120-ft deep TCE source area beneath a clean room was perfomed using direction drilling techniques. Heaters were installed at angles between 90 and 30 degrees from horizontal, with boring lengths up to 200 ft. The site had fine to coarse sand with boulders which could deflect the drill bit and alter the path of each boring. The team used innovative tools to monitor the resulting heater placement and to decide where additional drilling was needed to cover gaps which appeared by deflections resulting in heater spacing above 20 ft.

Approach/Activities:

Innovative drilling methods were used to install 135 steel casings under the building from an adjacent room. Four compact drill rigs operated simultaneously to meet the aggressive project schedule. Heater boring lengths ranged from 87 to 196 ft at angles between 90 and 30 degrees from horizontal. After each casing was installed, the exact trajectory and position of the casing was determined using the Devi-Flex tool. The trajectories were analyzed using a three-dimensional viewer (EVS) which allowed views from all directions and measurement of distance between the installed steel casings. If the deviations exceeded design parameters, additional borings were installed to ensure that the heater spacing was acceptable.

Results/Lessons Learned:

Our presentation will cover the major challenges and the solutions developed for them, including:

Drilling as much as 196 feet at angles of up to 30 degrees from horizontal and installing heater casing suited for TCH.
Custom-built TCH heaters with minimum heat output in the uncontaminated zone above the treatment interval.
Use of a Devi-Flex tool to survey boreholes as completed – and displaying the path in a three-dimensional viewer.
Analysis and optimization. An additional eight borings were installed to cover gaps caused by deflections.

The operations and results will be covered in a separate presentation.

Luis Hidalgo

Affiliation

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(Group 1, Poster Board #257) It’s Dark Down There! Three-Dimensional Tracking of 196-foot Long Borings Used to Optimize ISTR Performance