1. Scope

1.1 This practice covers the method for delineating the subsurface presence of nonaqueous phase liquids (NAPL) consisting of petroleum hydrocarbons, coal tars, and similar products using an optical image profiler (OIP) system. The OIP probe is advanced into soils and unconsolidated formations using direct push (DP) methods. The system provides data approximately each ~15 mm [0.05 ft] of log depth to support high-resolution site characterization. 1.2 The logging system uses an ultraviolet (UV) light-emitting diode (LED) or a green laser diode mounted inside the probe to induce fluorescence in polycyclic aromatic hydrocarbons (PAHs). Pulsed UV or green light is directed out of the probe through a sapphire window mounted on the side of the body. UV or green light causes fluorophores in the subsurface to fluoresce. A complementary metal-oxide semiconductor (CMOS) camera sensitive in the visible light region is used as a fluorescence detector. Fluorescence from the PAHs in the NAPL passes back through the window to the CMOS camera inside the probe. The CMOS camera captures images of the visible range fluorescence. The images are sent through the trunkline cable to the instruments and computer system uphole. The instruments and computer system provide real-time viewing, analysis, and acquisition of the images and data. 1.3 The optical logging system provides real-time qualitative to semi-quantitative results of the presence of hydrocarbon nonaqueous phase liquid (NAPL) in the subsurface in the field. The CMOS camera will detect other fluorophores that fluoresce in the visible spectrum region under UV or green light. The computer system records images of the fluorescence at discrete intervals. The fluorescence images can be viewed in real time or the saved images can be reviewed after the log has been completed. The fluorescence images may help to discriminate between petroleum hydrocarbon fluorescence and other fluorophores. Targeted sampling (Guides D6001 and D6282) should be used to confirm the optical image profiler results. 1.4 The optical logging system can detect nonaqueous phase hydrocarbons in the subsurface at concentrations in the parts per million range. Detection limits will vary with the degree of weathering, different types of hydrocarbon products, and the soil matrix. Dissolved phase hydrocarbons are not detected. 1.5 OIP logging is limited to soils that can be penetrated with the available direct push equipment. The ability to penetrate strata is based on carrying vehicle weight, density of soil, and consistency of soil. Penetration may be limited or damage to sensors can occur in certain ground conditions. DP tools are not designed to penetrate consolidated rock (Guides D6001 and D6282 and Practices D7352 and D8037). 1.6 Practice D6187 was an early standard on laser-induced fluorescence that used a complex nitrogen laser system uphole combined with fiber optics to induce fluorescence of PAHs downhole. Practice D6187 was withdrawn in 2019. 1.7 This practice offers a set of instructions for performing one or more specific operations. This standard cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this practice may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without the consideration of a projects many unique aspects. The word standard in the title means that the document has been approved through the ASTM consensus process. 1.8 Units--The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values state in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard. This standard is written primarily in SI units but depths are noted in dual units. 1.9 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026, unless superseded by this standard. 1.10 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 1.11 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

Keywords

groundwater; hydrocarbons; fluorescence; NAPL; logging; direct push; PAH; CMOS; LED; ultraviolet

Rationale

The OIP system provides a new and innovative tool and method for the detection of LNAPLs in the subsurface. Geo-environmental professionals and regulators will use the OIP system to detect and define the extent of LNAPL contamination, which is critical for defining hazards, human and environmental risks at many contaminated facilities. OIP logs can be used to develop accurate conceptual site models and remediation actions for site cleanup.

The title and scope are in draft form and are under development within this ASTM Committee.