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LIF Investigation Process

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Pre-Planning

If you are interested in UVOST, TarGOST and/or DyeLIF, and are unsure which LIF technology is most suitable for your site, feel free to Contact Us. For a general overview of the basic elements of the field investigation process, please see the General Investigation Process page.

Free Sample Check

We will usually request a sample of your site's NAPL(s) or, less optimally, NAPL-contaminated soil. A typical sample is a partially full 40 ml VOA, well labeled. We will analyze the sample with our LIF systems and quickly be able to tell you if LIF is a viable investigative tool for the site.

Be sure to include a detailed description of the product (any unusual hazards, etc.) and your full contact info. If your material is hazardous (PCBs, etc.) or we receive an excessive volume, you will be responsible for return shipment or for disposal by a local waste management company.

For a pdf with detailed shipping instructions, click here.

Hole Locations

Some customers like to pre-plan the hole locations, mark the site accordingly, and record all relevant x-y and elevation data. A plan of bounding the contamination based on results determined on-site is also viable. Regardless if the hole placement follows a grid or bounding procedure, Dakota strongly prefers to start LIF projects in what is believed to be the heart of the contamination. This gives everyone involved valuable information regarding how well the NAPL is going to respond to LIF delineation.

Confirmation Sampling

Dakota recommends discrete sampling at 10% of the hole locations if semi-quantitative values are to be assigned to the LIF signals. Soil sampling can be reduced to approximately 5% of total hole locations as a ground-truthing exercise. If an extensive sampling program is planned, the client should consider including a local driller and/or a second rig. Remember to build sampling time into your scope of work. We also recommend that you consider obtaining LIF responses to homogenized splits of your samples. If your site has heterogeneous lithology (very typical), the chance of you sampling soils/NAPL that are representative of that which the LIF probe passed through are near zero! If heterogeneity exists, and you try to compare lab results to LIF %RE of adjacent logs rather than LIF %RE of those same samples, the correlation will be poor (the expected result). We recommend doing duplicate logs at roughly 10% of the hole locations to gauge site heterogeneity.

If Dakota is contracted to collect soil samples, it will be prudent to do all the sampling at one time, preferably as the final stage of the field activities. Using LIF data, impacted zones can be identified and targeted for sampling, eliminating the need for continuous cores.

Expected Production

UVOST and TarGOST productivity can range anywhere from 200 to over 500 ft/day, while DyeLIF is slightly less. MIP and HPT production is typically in the range of 200 to 250 ft/day. If the pushes are fairly deep (>30 ft), and the obstructions or rubble are minimal, then the average is on the higher end because we spend a lot more time actually probing, not moving around from location to location and/or trying multiple times to get holes started through rubble. Other factors affecting production are grouting requirements, surface pavement, surface topography, and vegetation.

Start-Up Time

When the LIF system first arrives on site, it is powered up, and tested for proper function. If it is in Dakota’s Geoprobe, the LIF system is simply powered up and we’re ready to begin probing after a very short warm-up. If a CPT or other direct-push machine is used, the LIF system is integrated into the delivery platform, rods are strung with the Dakota’s optical fiber cable, and proper depth measuring connections are made (about a 2 to 3 hour procedure).

Barge Productivity

LIF operations on a barge usually limit daily production to 50 to 200 feet of logged depth. Additional factors affecting barge productivity are: location accuracy requirements, subsurface conditions, water depth, and presence of current or tide.

Hole Locations

Once Dakota leaves, our customers may wish to survey all the LIF probe locations if it wasn’t done prior to the job. Getting good positional information, including elevation, is key to any future CAD and visualization efforts.

Additional Services Available

Conceptual Site Model Visualization Option

Dakota now provides the capability to view TarGOST, UVOST and Dye-LIF site characterization data in unparalleled resolution. With our 3D models, the client has full control of the camera and is not limited by viewing static images.

Advanced Data Analysis Using NNLS Option

Many natural geologic materials fluoresce. In order to effectively interpret LIF logs we sometimes need to separate NAPL fluorescence from false positives such as peat, meadow mat, algae, crushed limestone, wood, and shell hash. Non-negative least squares (NNLS) analysis provides an effective solution.

Written Report Option

Dakota can summarize all on-site activity as well as provide detailed log and waveform analysis in the form of a written report.

Dakota Technologies

© Dakota Technologies, Inc.
2201-A 12th St N
Fargo, ND 58102
701-237-4908
info@dakotatechnologies.com

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