All the usual forms of petroleum non aqueous phase liquids (NAPL) distributed in the soils and groundwater contain significant amounts of naturally fluorescent polycyclic aromatic hydrocar-bons (PAH), which can be detected by Laser-induced fluorescence (LIF) method. Gasoline, diesel fuel, jet fuel, and hydraulic fluids can be detected and their presence versus depth precisely logged in the subsurface sedimentary rocks via the fluorescence response of PAH constituents. The fluorescence signal scales proportionally with NAPL concentration. LIF systems do not detect aliphatic chlorinated compounds, polychlorinated bi-phenyls (PCBs), or dissolved phase petroleum hydrocarbons. For purpose of petroleum NAPL objects delineation in the subsurface via LIF method Dakota Technologies, Inc. (Dakota) was specifically designed the Ultra-violet optical screening tool (UVOST) system, which now is available in Latvia too since 2008. Typically UVOST System operates in conjunction with a wide variety of direct-push plat-forms. LIF sensors are deployed as a part of integrated mobile cone penetrometer (CPT) systems. Now percussion-based probes can be used after sapphire-windowed probe is employed. With LIF logging can be combined electrical conductivity (EC) instrument as a complimentary module for UVOST. The UVOST LIF method uses a fiber optic-based LIF sensor system. Light at a specific wavelength generated from a laser is passed down a fiber optic cable to a sapphire window in the tip of the CPT rod string as it is advanced into the subsurface. The laser light excites two- or three-ring aromatic compounds or polycyclic aromatic hydrocarbons (PAH), in the soil adjacent to the sapphire window, causing them to fluoresce. The relative response of the sensor depends on the specific analyte being measured because of the varying ratios of PAHs in each hydrocarbon mixture. The induced fluorescence from the PAHs is returned over a second fiber to the surface where it is quantified using a detector system. The peak wavelength and intensity provide information about the type of petroleum product or potential interferences. In the UVOST LIF system four unique wavelengths bands of light (350, 400, 450 and 500 nm) can be monitored in real-time to provide a signal which is an indicator of the relative contaminant composition. The waveforms that are continuously logged versus depth with UVOST contain a wealth of in-formation. To make this information easily interpretable in fluorescence versus depth (FVD) log format, it is necessary to reduce the data to a one-dimensional data set that can be plot in FVD log. For those purposes a special colorization (coding) technique is used - FVD log plot fill color is based on relative contribution of each channel's area to the total waveform area (see callout waveforms). That means – for the different petroleum hydrocarbons on the FVD log plot will match a consequent color. Figure 4 shows the typical calculated fill color for diesel which appears on the versus depth log plot. UVOST's LIF technique, in conjunction with direct push deployment, yields a detailed three-dimensional map of the NAPL distribution (Figure 5), in real time - offering a true "seek and find" adaptive site characterization capability as promoted by U.S. EPA's Triad Approach – Integration of systematic planning, dynamic work plans, and real-time analysis as applied to contaminated sites. The data obtained by UVOST provides the capability to view site characterization data in 3D or 2D in static or dynamic format. The site also can be overlay with aerial photographs or building CAD models over GIS terrain data to provide an accurate overall picture of the site with relevant subsurface features. UVOST data logs are typically acquired at 1 inch vertical resolution which is orders of mag-nitude higher resolution than traditional sampling methods. The data obtained by UVOST LIF’s method key advantage is high accuracy in the contamination models. When visualized in 3D, contaminants migrating in narrow seams or “stringers” of sand, silt, or gravel are easy to see. UVOST high data density reveals these types of contaminant distribution features often missed by conventional sampling methods. That allows reaching a high correlation between individual UVOST data logs and the 3D conceptual model.