General Overview of Investigation Process
For a general overview of the basic elements of the field investigation process, please see the General Investigation Process page.
Membrane Interface Probe Investigation Process
System Transport and Setup
The investigative process for MIP involves several aspects that are unique to this specific technology. The main components of the MIP system are housed in a Sprinter van, truck or other similar vehicle. The MIP lab setup includes a computer, communication cables, a power inverter, tools, spare probes and trunklines, 4-foot rods, and various peripheral items. Since the MIP system is a relatively complex system (MIP probe/Trunkline integrated into lab grade PID, FID & XSD detectors) our operators are familiar with analytical laboratory systems and the setup, execution and interpretive aspects of the investigation process. The MIP detects many chlorinated volatile organic compounds (CVOCs) and non-chlorinated VOCs in vapor, sorbed, dissolved or non-aqueous phases, but is not able to distinguish between the phases. With careful selection of the detector suites, the MIP directly distinguishes CVOCs from non-chlorinated VOCs.
Upon arrival at the site, the MIP system (including laboratory) is turned on and warmed up for at least 15 minutes until all equipment is at optimal operating temperature and the detector baselines are stable. Next, the MIP system is quality checked and all tests must pass before logging begins. The EC (electrical conductivity) is tested and chemical response tests (membrane performance evaluation) are performed to evaluate the system and establish detector’s starting baselines.
MIP Membrane Performance Monitoring
The MIP’s membrane performance must be evaluated throughout the project to ensure as much consistency as possible between all MIP logs. It is changed (and response tests are repeated) every time the membrane fails to meet the required performance level. This is particularly important if the data are to be utilized in modeling the plume shape/size.
Direct Push Process
During MIP logging, the probe is advanced 1 foot and then allowed to reside in this zone for 45 seconds or longer before proceeding to the next 1-foot interval. In comparison, HPT requires less frequent stopping, only for the purpose of performing dissipation tests, and is otherwise pushed at the continuous standard direct sensing rate of 0.8”/sec. The UVOST, TarGOST and Dye-LIF systems require no stopping during data acquisition and logging. Highly contaminated locations may require extended wait time for MIP system 'clean-up,' baseline stabilization and changing of contaminated membrane before proceeding to next logging area.
MIP borings should ideally be performed in a “clean-to-dirty” rather than “dirty-to-clean” sequence to minimize increased wait times associated with system clean-up as described above when working in areas of elevated contamination. Preparations for real-time analysis, such as filtering data, performing baseline adjustments and preparing 2D figures to further guide the investigation are also performed. Typically, Dakota will setup a secure website for field data uploads. It is common for data to be uploaded twice a day, but this can be adjusted to be more frequent if requested.
Confirmation soil/water sampling is recommended and typically performed to confirm field data and further define contaminant concentrations and constituents. Dakota also recommends that EC data be compared to soil boring logs for lithology confirmation.
Generally, MIP total footage production is approximately 100 to 300 feet/day, which is somewhat lower than typical LIF averages of 200 to 500 feet/day.