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HomeMy WebLinkAboutRA-517_3274_CA_RPTS_202220831220 Old Dairy Road Wilmington, NC 28405 (910) 452-5861 www.CatlinUSA.com Wilmington, NC | Raleigh, NC | Washington, NC | Atlanta, GA ENVIRONMENTAL | CIVIL | GEOTECHNICAL Wilmington, NC | Raleigh, NC | Washington, NC | Atlanta, GA | Charleston, SC August 31, 2022 North Carolina Department of Environmental Quality Division of Waste Management UST Section Attn: Mr. Mark Petermann 1646 Mail Service Center Raleigh, NC 27699-1646 Re: Letter Report PetroMart #4 11455 US Hwy 15-501 N Chapel Hill, Chatham County, North Carolina NCDEQ Incident No. 3274 Risk Classification: H210A CATLIN Project No. 221139 Dear Mr. Petermann, CATLIN Engineers and Scientists (CATLIN) is pleased to provide you with this letter report documenting field activities performed in general accordance with CATLIN proposal number 221139.3P. Services were authorized by the North Carolina Environmental Quality (NCDEQ) Task Authorization (TA) #03, approved June 15, 2022 and accepted June 16, 2022, and Contract Number N122019D. The approved scope of services for this Task Authorization included: • Oversight of a Laser Induced Fluorescence (LIF) investigation; • LIF investigation conducted by Dakota Technologies (Dakota); and • Prepare a letter report documenting the findings. The PetroMart #4 site is located at 11455 US Hwy 15-501 North, Chapel Hill, NC (See Figures in Attachment A). Based on historical light non-aqueous phase liquids (LNAPL) and dissolved contaminant concentrations in monitoring well MW-3, CATLIN recommended a LIF investigation be conducted to help provide a better understanding of the residual contamination in the vicinity of MW-3. Field activities were conducted on July 14, 2022 in accordance with the approved TA. Potential hazards were evaluated before beginning field work and documented on an electronic Job Hazard Analysis (JHA) form, provided in Attachment B. Site photographs are presented in Attachment C. LIF Investigation On July 14, 2022, CATLIN oversaw the LIF investigation performed by Dakota. As part of the investigation, Dakota advanced five borings each to a depth of approximately 40 feet below land surface (BLS) utilizing direct push technology (DPT). During boring advancement, an Ultra-Violet Optical Screening Tool (UVOST®) combined with a hydraulic profiling (HP) sensor was used to evaluate LNAPL occurrence in the subsurface at various depths. Following the investigation, August 31, 2022 Page 2 of 2 NCDEQ; 3274_Petro Mart #4 CATLIN Engineers and Scientists CATLIN Project No. 221139 August 2022 Dakota prepared a High-Resolution Site Characterization (HRSC) Report, which is included in Attachment D. LIF Results The HRSC Report indicated that 4 of the 5 UVOST®-HP borings contained fluorescence waveforms that met the criteria to indicate at least some NAPL impact. A proprietary LNAPL mixture known as the Reference Emitter (RE) is used for quality assurance and quality control for the qualitative and semi-quantitative response of the UVOST. Based on the %RE, it appears that potential LNAPL is generally less than 1-foot BLS. The UVOST®-HP Logs are located on pages 22 through 26 of the HRSC Report and a map of the data showing the locations of the LIF points is included on page 32. Recommendations CATLIN recommends conducting a surfactant injection in MW-3 followed by either an aggressive fluid vapor recovery (AFVR) or mobile multi-phase extraction (MMPE) event to help mobilize any LNAPL trapped in the subsurface near MW-3. CATLIN Engineers and Scientists will proceed upon notification of your approval. Should you have any questions or require additional information, please contact us at (910) 452-5861. Sincerely, Sean O’Neil, PE Project Manager Attachments: A Figures B Job Hazard Analysis C Site Photographs D High-Resolution Site Characterization Report NCDEQ; 3274_Petro Mart #4 CATLIN Engineers and Scientists CATLIN Project No. 221139 August 2022 ATTACHMENT A FIGURES SITE LOCATION US HWY 15-501 NMANNS CHAPEL RD Copyright:© 2013 National Geographic Society, i-cubed FIGUREPROJECTTITLE 1PETROMART #411455 US HWY 15-501 NCHAPEL HILL, NC SITE VICINITY MAP 2,000 0 2,000 4,0001,000 Feet INCIDENT NO.JOB NO.DATE SCALE DRAWN BY/CHECKED BY3274221139AUG 2022 AS SHOWN KMC/SJO ³ !> !>!> !>!>!> !> !> !> !> !> !> ########## ############### ############### # # #### # # ## ################ ##### # # ### ###################### # ####### ### #### ### ##### #### ###### #### #### # # # ##### # ####### ## # # #US HWY 15-501 NMANNS CHAPEL RD MW-5 MW-1 MW-6 MW-8 MW-12 MW-2 MW-4 MW-3 MW-11MW-7 MW-10 MW-9 FORMER USTS CURRENTUSTS 04-LIF 05-LIF 03-LIF 02-LIF 01-LIF Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community FIGUREPROJECTTITLE 2PETROMART #411455 US HWY 15-501 NCHAPEL HILL, NC SITE MAP 60 0 60 12030 Feet INCIDENT NO.JOB NO.DATE SCALE DRAWN BY/CHECKED BY3274221139AUG 2022 AS SHOWN KMC/SJO NOTE: Well and tank locations were obtained from previous reports prepared by other consultants and are approximate. Monitoring Well (Type II)!> LEGEND Parcel Boundary ³ Approximate Location of UST Systems LIF/UVOST Boring# NCDEQ; 3274_Petro Mart #4 CATLIN Engineers and Scientists CATLIN Project No. 221139 August 2022 ATTACHMENT B JOB HAZARD ANALYSIS Source Exposure Limit Groundwater and/or soil vapor 0.5 ppm TLV-TWA ACGIH Groundwater and/or soil vapor 100 ppm TLV-TWA ACGIH Groundwater and/or soil vapor 20 ppm TLV-TWA ACGIH Groundwater and/or soil vapor 100 ppm TLV-TWA ACGIH Groundwater and/or soil vapor 50 ppm TLV-TWA ACGIH Groundwater and/or soil vapor 10 ppm TLV-TWA ACGIH Source Exposure Limit atmosphere N/A atmosphere N/A surroundings N/A Exposure Potential Likely Likely Likely Start Stop 7:00 8:00 8:00 8:15 8:15 17:15 17:15 18:30 Date and Time: 7/14/22 - 08:15 NAPHTHALENE ppm Physical Hazards Name of Physical Hazard Exposure Level/ Potential * Gas and/or Diesel TOLUENE ppm XYLENE, ALL ISOMERS ppm METHYL TERT-BUTYL ETHER ppm Potential Chemicals Concentration BENZENE ppm ETHYL BENZENE ppm Chemical Hazards Sunny 80s Site-Specific Job Hazard Analysis Location Where Task/Operation Performed PetroMart #4, Chapel Hill, NC Task/Operation Overisght of LIF Investigation Employee Certifying this JHA Print Name: Sean O'Neil, P.E.Signature: Operational Phase Monitoring Date(s) this JHA Conducted: 7/14/21 PERSONNEL ONSITE Name and Company (Print)Signature Nate Newman / CATLIN Likely Slips/Trips/Falls Likely surroundings Drive back to office and demob. Start:End: DAILY TASK Snakes surroundings Poison Plants (Ivy, Oak, and/or Sumac)surroundings Equipment Used:PPE D/water level indicator Van #40 Mileage: Weather: Mobe and Drive to site. Safety briefing. Watch for cars in parking lot and travelling down nearby side road and wear safety vest. Practice good housekeeping to avoid slips, trips and falls. Drink plenty of water. Be cautious around rig. Supervised LIF event. Spoke with property owner and employees. Oversaw movement of cars to allow access to necessary LIF locations. Biological Hazards Name of Biological Hazard Source Insect bites and stings Cold Weather Operations Unlikely Heat (ambient) NCDEQ; 3274_Petro Mart #4 CATLIN Engineers and Scientists CATLIN Project No. 221139 August 2022 ATTACHMENT C SITE PHOTOGRAPHS ATTACHMENT C SITE PHOTOGRAPHS – JULY 14, 2022 NCDEQ; 3274_Petro Mart #4_Site Photos CATLIN Engineers and Scientists CATLIN Project No. 221139 August 2022 View of 01-LIF, facing east. ATTACHMENT C SITE PHOTOGRAPHS – JULY 14, 2022 NCDEQ; 3274_Petro Mart #4_Site Photos CATLIN Engineers and Scientists CATLIN Project No. 221139 August 2022 View of 02-LIF, facing east. ATTACHMENT C SITE PHOTOGRAPHS – JULY 14, 2022 NCDEQ; 3274_Petro Mart #4_Site Photos CATLIN Engineers and Scientists CATLIN Project No. 221139 August 2022 View of 03-LIF, facing north. ATTACHMENT C SITE PHOTOGRAPHS – JULY 14, 2022 NCDEQ; 3274_Petro Mart #4_Site Photos CATLIN Engineers and Scientists CATLIN Project No. 221139 August 2022 View of 04-LIF, facing northeast. ATTACHMENT C SITE PHOTOGRAPHS – JULY 14, 2022 NCDEQ; 3274_Petro Mart #4_Site Photos CATLIN Engineers and Scientists CATLIN Project No. 221139 August 2022 View of 05-LIF, facing northeast. NCDEQ; 3274_Petro Mart #4 CATLIN Engineers and Scientists CATLIN Project No. 221139 August 2022 ATTACHMENT D HIGH-RESOLUTION SITE CHARACTERIZATION REPORT 1 High Resolution Site Characterization Report UVOST®-HP Investigation PetroMart #4 11455 US Hwy 15-501N Chapel Hill, NC DTC Project No: 0244.2022 July 18, 2022 Prepared For: NCDEQ 1646 Mail Service Center Raleigh, NC 27699-16465 Prepared by: Davis Ocana Reviewed By: Mike Jenson Dakota Technologies Company, LLC 713-448-9211 docana@dakotatechnologies.com Dakota Technologies Company, LLC 763-424-4803 mjenson@dakotatechnologies.com TABLE OF CONTENTS 1.0 General Site Information ................................................................................................................. 1 2.0 Laser-Induced Fluorescence - UVOST® Technology Overview ............................................................ 1 2.1 Reference Emitter .......................................................................................................................... 2 2.2 Waveforms ..................................................................................................................................... 3 2.3 Cluster Plots .................................................................................................................................... 5 3.0 Hydraulic Profiling (HP) Description ................................................................................................. 8 4.0 Site-Specific Results and Discussion ................................................................................................. 9 4.1 Site-specific Waveforms ................................................................................................................. 9 4.2 Site Cluster Plots ........................................................................................................................... 11 5.0 GPS Data/Survey Control .............................................................................................................. 15 6.0 Limitations.................................................................................................................................... 15 APPENDICES Appendix A UVOST®-HP Field Summary Appendix B UVOST®-HP Logs at 10% RE Appendix C Reference Log Appendix D ISO Map of UVOST Data Appendix E GPR Site Sketch Appendix F GPS Coordinates High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 1 version 6.2-April 2022 1.0 General Site Information Dakota Technologies Company, LLC (DTC) was contracted by the North Carolina Department of Environmental Quality (NCDEQ) to perform a High-Resolution Site Characterization (HRSC) study at the Petro Mart #4 site, located at 11455 US Hwy 15-501N, Chapel Hill, NC. The goal of the HRSC investigation was to identify any potential LNAPL source areas and to better define the horizontal and vertical extent of impacted soil and groundwater. A secondary goal of the HRSC investigation was to gather data to assist in determining potential preferential contaminant pathways and/or retention zones. Fieldwork included Laser Induced Fluorescence (LIF) to verify the presence of, and delineate the extent of, the LNAPL present in the subsurface. The LIF portion of the study employed the use of an Ultra-Violet Optical Screening Tool (UVOST®) combined with a hydraulic profiling (HP) sensor. A description of the UVOST® technology, waveforms, cluster plots, limitations of LIF, and a UVOST® Reference Log are included in this report. 2.0 Laser-Induced Fluorescence - UVOST® Technology Overview Fluorescence is a property of some compounds where absorbed excitation light stimulates the emission of light of a longer wavelength relative to the excitation source (laser). The stimulated release of light can be used to detect small amounts of polycyclic aromatic hydrocarbons (PAHs) in a larger matrix (soil, NAPL, water). This sensitive method of PAH detection has been used in laboratories for decades. With the commercial availability of lasers and optical fibers, this technology can also be applied in-situ in the field to identify the presence of non-aqueous phase liquids (LNAPL) that contain a wide variety of PAHs. The UVOST® system sends ultraviolet (UV) laser light (308-nanometer wavelength) through a fiber optic cable strung through probe rods on a direct push drill rig. The light is reflected by a parabolic mirror within the probe and out a sapphire window on the side of the SPOC. As the probe is advanced, soil that is contiguous to the sapphire window is exposed to the pulsed UV laser light. If PAHs (compounds in petroleum, oils and lubricants that fluoresce) are present, these PAHs absorb a portion of the UV light and enter an electronically excited state. When returning to ground state, the PAHs release excess High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 2 version 6.2-April 2022 absorbed energy by emitting photons of longer wavelength light than the original UV excitation light. This fluorescence is transmitted through a return fiber to the surface where the OST system transforms the fluorescence light into time-resolved multi-wavelength waveforms that capture the fluorescence intensity, wavelength, and lifetime (duration of the fluorescence). The UVOST system is particularly sensitive to NAPL (compared to dissolved phase for instance); in other words, it focuses on the source term contaminant at the site. Vapor, dissolved, and absorbed hydrocarbon phases are usually invisible to the UVOST system, with dissolved phase PAHs in the vicinity of heavy NAPLs like coal tar being a notable (and confounding) exception. In most cases, only the NAPL- entrained PAHs respond to the UVOST system. These PAHs fluoresce most intently in saturated free product in the soil pore spaces and the response drops off with saturation, down to sheens of product lightly coating the soil particles. LIF essentially “ignores” any water in the pore spaces. Therefore, valid fluorescence data can be collected both above and below the water table. 2.1 Reference Emitter The UVOST® system is checked for background signal (sources of fluorescence in the fiber, filter, mirror and sapphire window) and this signal is stored in the data file. A proprietary LNAPL mixture known as the Reference Emitter (RE) is used for quality assurance and quality control for the qualitative and semi- quantitative response of the UVOST. DTC has used this same RE for decades. During the pre-log calibration, a cuvette containing the RE fluid is placed over the sapphire window; the laser is adjusted to achieve optimal signal amplitude, and the response from the RE is then recorded. The RE’s fluorescence intensity (brightness) is then used as a definition of fluorescence intensity of 100% relative to the RE, or 100% RE. Typically, the RE’s raw total fluorescence will fall between 10,000 and 12,000 picovolt-seconds (pVs). The system background fluorescence can vary from 0.1% to 1%RE, or 0 to 100-pVs raw total fluorescence. The operator ensures the RE response has the correct shape and intensity so that the UVOST® system is “calibrated” for each log and minimizes system background by keeping the mirror and window clean and the SPOC purged of moisture. All the fluorescence responses obtained in the subsequent borehole are gauged against the RE’s fluorescence response. High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 3 version 6.2-April 2022 The relationship between the instrument responses from NAPL in the subsurface and the %RE depends on the NAPL type, age, and other factors. There are NAPLs that fluoresce much more brightly than the RE (>100%RE) at full pore saturation, such as gasolines, diesels, and crude. Other NAPLs might only fluoresce half as intensely as RE, such as heavy crudes which might fluoresce at 50%RE. One must be careful to “temper” their interpretations of fluorescence based on the fuel type, degree of weathering and other site-specific factors. Please ask for assistance with this and we’ll be glad to help you do site- specific calibration of your data set! The combined fluorescence of non-NAPL impacted natural soils and system background (the optic surfaces) generally fall in the range 0.25-0.75 %RE. A signal response greater than 1.0%RE typically indicates the presence of LNAPL, however, various natural materials including calcareous and carbonaceous soils may produce “false positive” results with signal responses as high as 10% to 20%RE. Lifetimes above the average baseline soils are often KEY indicators of NAPL. Buried wood and organics can be even more fluorescent than background soils but again, the lifetime information can assist in helping you “make the call” on whether it’s NAPL vs. natural fluorescence. Therefore, it is crucial that consumers of fluorescence data rigorously inspect the fluorescence responses (waveforms, fill colors, lifetimes, etc.) to distinguish the presence of NAPL from false positives from natural soils and organic materials. With a little practice and knowledge, it’s generally easy to sort out the false positive fluorescence from the actual NAPL, which is key to prevent over-estimation of NAPL impact. 2.2 Waveforms Waveforms are fluorescence “signatures” that are used to differentiate LNAPL types such as kerosene versus intact gasoline, weathered gasoline versus diesel fuel, etc. Waveforms also provide the capability to effectively differentiate false positives from intact LNAPLs. Various waveform patterns for pure PAHs, fuels/oils, weathered gasoline, and false positive substances can be viewed at Dakota’s website: http://www.dakotatechnologies.com/learn-more/intro-to-lif/data-interpretation. High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 4 version 6.2-April 2022 Figure 1 shows three sample waveforms used to characterize NAPL. Figure 1: Waveforms generated by gasoline, diesel and kerosene. The four colored peaks in the waveforms (referred to as channels) represent different PAH emission wavelengths (colors) that are filtered by the UVOST system into four categories: 350-nanometers (blue), 400-nanometers (green), 450-nanometers (orange), and 500-nanometers (red). In the waveform callouts (graphs from selected parts of a log) shown, the y-axis represents the intensity of the fluorescence signal (V) and the x-axis is time (approximately 350-nanoseconds). The relative contribution of each channel’s area to the total waveform area defines the Signal (%RE) fill color on the main UVOST log. For example, a waveform with a stronger contribution by the blue channel relative to the other three channels will plot with a bluish color on the UVOST log (see the kerosene waveform, and the resulting blue fill color in the upper right, in Figure 1). In the case of the gasoline waveform, the calculated color is a pale green that is displayed in a box in the upper right-hand corner of the waveform plot window. The shorter wavelength channels on the left (blue/green) represent smaller PAHs with two to three benzene rings; the middle two channels (green/orange) contain response from intermediate size PAHs with three to four benzene rings; the rightmost channels (orange/red) correspond to larger PAHs with four or more benzene rings. Note, the blue, green, orange, and red colors associated with the four channel wavelengths are not the actual color of fluorescence, they are placeholder colors. The true colors of the UVOST waveform’s four channels are ultraviolet, violet, indigo, and blue/cyan from left to right. The ultraviolet fluorescence in the first channel (invisible to the human eye or visible-light spectrum cameras such as the OIP (Optical Image Profiler)) is particularly useful for identifying “intact” gasolines at petroleum service stations. The waveform’s four channels are sequentially delayed pulses of fluorescence arriving as a “train” on the detector. The amplitude of each channel corresponds to the intensity of each fluorescence color High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 5 version 6.2-April 2022 being released by the PAHs following the excitation by the UVOST laser pulse. The pulse of each color starts out strongest immediately following the excitation laser pulse. But after the laser pulse is gone, the fluorescence quickly begins to decay, eventually returning to darkness (no more light being emitted). The time it takes for the laser excitation energy to dissipate (and the subsequent PAH fluorescence to fade away to darkness) is recorded on the times axis and leads to a “ski slope” on the right side of each channel or “peak”. The point in time at which each channel’s fluorescence has decayed to approximately 1/e of the maximum is classically referred to as that channel’s “lifetime”. In general, longer lifetimes (wide peaks) are indicative of intact “juicy” LNAPL with lots of intact solvent molecules such as aliphatics. False positive soils or highly weathered NAPLs with little very solvent left usually have shorter lifetimes (skinny peaks). Heavy NAPLs like coal tar are a notable exception, as they experience intramolecular energy transfer after excitation (due to their excessive PAH content), resulting in extremely low fluorescence (only a few %RE even when fully saturating the soil), extremely short lifetimes (narrow peaks) and domination by the orange and/or red channels. Atmospheric concentrations of molecular oxygen that are present under “bench-top” NAPL testing conditions artificially lower fluorescence lifetimes compared to in-situ conditions where oxygen is lacking due to bioremediation processes. You can always expect to see longer lifetimes (and larger overall %RE) from in-situ readings compared to NAPLs take from wells and tested under atmospheric oxygen (~20%) conditions. 2.3 Cluster Plots The hundreds, or thousands, of waveforms in each UVOST log are immensely useful, but with only five callouts in each log, it’s hard to take it all in and make sense of all of them. Cluster plots provide a method for viewing all the waveforms by converting them into simple color and lifetime data and plotting each waveform as a bubble on a Cartesian coordinate system. The cluster plot axis corresponds to fluorescence wavelength (λ) (or color) on the X-axis and the fluorescence lifetime (τ) on the Y-axis as measured and weighted in each the four channels. In this fashion, all data points from a UVOST log are sorted by their color and lifetime properties and can be viewed in a single figure, allowing intuitive comparisons to be made among potential fluorescence categories. Figure 2 demonstrates the relationship between data points in the log and how they appear in the cluster plot. High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 6 version 6.2-April 2022 Figure 2: The X-axis of the Cluster Plot (right) corresponds to the balance of the four colored channels in the waveform; the Y-axis relates to fluorescence decay or “lifetimes” of the four-waveform channels. Responses dominated in the blue/green channels (intact gasolines for instance) will plot in the left side of the cluster plot (see blue ovals in Figure 2). Likewise, if the orange and red channels make up bulk of the fluorescence response (background soils), the data point will plot on the right side of the cluster (see orange ovals in Figure 2). Waveforms with a relatively equivalent contribution from all four channels, or with the two central peaks dominating such as modestly weathered NAPLs or light staining of intact NAPLs, will plot somewhere in the middle (yellow ovals in Figure 2). Similarly, longer-lived responses from intact fuels (wide at the base of the waveform) will plot higher on the Y-axis and waveforms with shorter lifetimes (narrow at the base of the waveform) such as carbonaceous soils or heavily weathered NAPL, plot lower on the Y-axis. In a simple sense, if waveforms leave the “home cluster” of soils and highly weathered NAPL at lower right, they are highly suspect of indicating NAPL. To further aid in determining the source on the UVOST® log for a point cluster, the main callouts from the log with their respective depth intervals are depicted on the upper left corner of the cluster plot (not High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 7 version 6.2-April 2022 depicted here). Polygons (for depth ranges) and circled data points (for discrete depths) with the same coloration as the callout waveform enclose the point clusters included in that callout. Weathering and formulation of each LNAPL will influence where the LNAPL appears on the cluster plot. In other words, it is not possible to identify a fuel solely by its location on a cluster plot. In Figure 3, the formulation of the 2 different diesel signatures labeled 1995 and 2007, fall into different regions of the plot. This is due to the difference in lifetime and wavelength characteristics of the four channels that make up these slightly different diesel waveforms due to source, age, and oxygen levels when this data was recorded. Figure 3: Reference examples of LNAPL types that were placed on the window of a UVOST® system in a laboratory setting. The cluster plot positions displayed illustrates the cluster separation of LNAPL types achievable with the UVOST and is not indicative of exclusive plotting location—LNAPL may plot across multiple grid cells as the plume weathers or interacts with the native soil. High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 8 version 6.2-April 2022 3.0 Hydraulic Profiling (HP) Description The Hydraulic Profiling add-on is a logging tool that measures the pressure required to inject a flow of water into the soil as the probe is advanced into the subsurface. The injection pressure log is an excellent indicator of formation permeability. In addition to injection pressure, hydrostatic pressure can be measured under a zero flow condition, called a dissipation test. This allows a calculation of potentiometric surface (water table) upon successful completion of the dissipation test. Prior to starting a log, there is a quality assurance (QA) check on the down-hole transducer to ensure proper function. The probe is submerged in a reference tube and filled with water. A reading is taken at the hydraulic port when it is submerged to a depth of 1 foot and a second reading at 0 feet, or baseline, under zero flow conditions. The reading at 0 feet, or the baseline pressure, is equal to the measurement of atmospheric pressure. Subtracting reading 2 from reading 1 should produce a result of 0.433 psi (+/- 10%), which is the hydrostatic weight of a 1-foot column of water. The UVOST®-HP probe is advanced into the ground at a rate of approximately 2 cm/sec. The pump in the HP flow module draws water from the supply tank and pumps water down the trunk line at a constant flow rate (60 mL/min). The downhole transducer monitors the pressure generated by injecting water into the formation matrix. The log provides graphs of the pressure and flow rate versus depth alongside the fluorescence plot. If a dissipation test is performed below the water table and the test successfully stabilizes, the result can be corrected to an absolute hydrostatic value, from which a potentiometric surface (water table) can be calculated. Using the calculated water table to correct for hydrostatic pressure increase, a hydraulic conductivity (K) value for a given depth below the water table can be estimated using the following equation: K = ln(Q/P’) * 20.0 + 7.0 where P’= downhole pressure – (0.433 * depth below water table) – atmospheric pressure, and Q is equal to flow. K values above the water table are also reported after a successful dissipation test even though they are suspect due to varying permeability behavior of dry soils. These values still maintain High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 9 version 6.2-April 2022 some qualitative value to the eye, and may lend insight into preferential pathways in the vadose zone. HP data can be incorporated into a 4DIM visualization protocol. 4.0 Site-Specific Results and Discussion Field activities were completed on July 14, 2022, and included 5 UVOST®-HP borings. Breaks in fieldwork were due to probe maintenance and repair. The target depth for the UVOST®-HP locations was 40-ft below ground surface (bgs) and all of the locations achieved that depth. All UVOST®-HP borings were precleared by ESP associates using GPR. Approximately 10 waveforms per foot were captured continuously by the UVOST® system at all UVOST®-HP locations. These waveforms, combined with their corresponding Cluster Plots, are key to successful data interpretation. Based on review of the fluorescence versus depth logs, depth specific waveforms and cluster plots, 4 of the 5 UVOST®-HP borings contained fluorescence waveforms that met the criteria to indicate at least some NAPL impact. The criteria used to make this determination is elevated fluorescence of the color, blue- or red-shift and/or elevated lifetimes necessary to achieve “liftoff” away from the background cluster at all locations. The remaining UVOST®-HP borings (03-LIF) can be considered free of LNAPL (at least at levels detectable with UVOST). This “NAPL-free” determination is based on the low fluorescence intensity, short lifetimes, and waveform color that match the surrounding baseline soils, resulting in the classic tight bubble clustering at the lower right in the Cluster Plots (grids I0 and J0), indicating only background (i.e. natural soil) fluorescence. 4.1 Site-specific Waveforms Fluorescence across the site was generally low, indicating minimal or no NAPL presence. The waveforms that we did encounter indicate very weathered NAPL or background/soils generated fluorescence. These waveforms range from 450nm (orange channel) dominant waveforms to waveforms that stair step upwards through the 500nm (red channel) wavelength. High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 10 version 6.2-April 2022 Waveform average from 12.4 – 20.2 feet bgs at location 02-LIF. This waveform stair steps up towards the 450nm (orange channel) wavelength and decreases again at the 500nm (red channel). The waveform begins to red-shift as the NAPL begins to weather. With a 1% RE signal response the calculated fill color of this waveform is orange. Waveform average from 0.0 – 1.9 feet bgs at location 04-LIF. This waveform, when compared to the waveform above from location 02-LIF, has red-shifted a significant amount. This could be due to oxygen quenching from being near the surface. The waveforms calculated color fill is a and orange red color as a result. Waveform from 13.4 – 39.3 feet bgs at location 03-LIF. This waveform is typical of the “clean” background soil fluorescence in the subsurface throughout the site. Total fluorescence signal is 0.2%RE. The combined colors of the four peaks result in an orange fill color as indicated in the top right hand corner of the waveform callout box. Waveform average from 0.0 – 1.7 feet bgs at location 01-LIF. This waveform is similar to that of 04-LIF. This waveform also has a significant red shift indicated by the large step-ups in height from the 350nm channel through the 400 and 450nm channels. The waveform has a combined signal of 2.7% RE and a calculated color fill of orange. High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 11 version 6.2-April 2022 The above waveforms (or combination thereof) were the most common waveforms encountered at the site. It is important to note that even small fluorescence responses can indicate NAPL. Slight changes in waveform colors and wavelength lifetimes are the key indicators of NAPL versus background fluorescence. When reviewing UVOST waveforms to determine NAPL type, it is important to consider additional lines of evidence such as cluster plots, confirmation soil sampling and lab analysis. Consistent waveforms at a site typically indicate consistent product and saturation. 4.2 Site Cluster Plots Cluster Plots (bubble diagrams) are displayed on each individual log in Appendix B. Each “bubble” represents one of the waveforms from the corresponding UVOST log and the fill color of the bubble matches the fill color from the depth specific waveform associated with that bubble. The larger the bubble, the higher the %RE associated with that particular depth. Background and natural fluorescence signals are included in the clustering presentation and typically “cluster” in a tight group in the lower right of the cluster plot. Low NAPL signals will “drift away” from this group. The further away each waveform’s bubble is from the background cluster, the higher the likelihood it represents NAPL. In addition, bubbles that cluster close together typically represent the same NAPL type and/or degree of weathering. High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 12 version 6.2-April 2022 Figure 4: The image above, from location 03-LIF, shows the background cluster plot diagram from the site. The tight cluster of “bubbles” located in the lower right, grids H0 and I0, of the cluster plot represents the background fluorescence encountered throughout the fluorescence versus depth log at this location. High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 13 version 6.2-April 2022 Figure 5: Similar to the above cluster plot from location 03-LIF, location 02-LIF, shows just a short weathering trail stretching from the higher %RE bubbles and drifting down and right towards the background cluster in grids H0 and I0. The highest %RE bubbles are located in grid location H1. Despite not being very high, they create the short end of a weathering trail. This is attributed by the short wavelengths and low average lifetimes. High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 14 version 6.2-April 2022 Figure 6: The cluster plot from location 05-LIF shows what seems to be almost all background. Though they are close to the tight background cluster (grids H0 and I0), the bubbles in G0 could be possible remnants of a heavily weathered NAPL. In addition, the waveform callouts with above 1% RE are located within the background cluster. This could be due to extreme weathering of the NAPL and/or false positive from calcareous subsurface. Please do not hesitate to contact Randy St. Germain for additional assistance with interpretation of your site’s UVOST logs. He can be reached at stgermain@dakotatechnologies.com or 701-237-4908 and can assist you with unlocking the wealth of information in your UVOST logs with regard to fuel type, degree of weathering, removal of false positives, isolation of certain target fluorescence types from other types, relating NAPL saturation to %RE, and other common UVOST site data interpretation/processing approaches. High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 15 version 6.2-April 2022 5.0 GPS Data/Survey Control Dakota surveyed the UVOST® borehole locations using a Trimble Geo7x centimeter grade GPS. Differential correction was applied to enhance the accuracy of the field collected data points. This differential correction relies on publicly available base station data. The proximity of the site to the nearest high-quality base station can have an impact on positional accuracy. When possible, Dakota uses the Continuously Operating Reference Station (CORS) operated by the national Geodetic Survey (NGS). When a CORS base station is not available, Dakota uses the closest alternative selected based on the integrity index provided by the GPS Pathfinder Office processing software. Dakota provides coordinates in NAD 83 US Feet, with the appropriate state plane projection. 6.0 Limitations The UVOST® system is limited in that it responds in a highly preferential manner to non-aqueous phase liquid petroleum, making it an ideal tool for source delineation. UVOST® does not typically respond (to any useful degree) to dissolved phase VOCs or SVOCs. In addition, the soil matrix (soil grain size) can influence how a NAPL fluoresces. UVOST® responses are typically higher on coarse or poorly sorted sands than in fine grain clays and silts. The UVOST® system should never be used to delineate coal tars and creosotes due to a misleadingly small fluorescence response (due to internal quenching of fluorescence) while simultaneously encountering a heightened response to dissolved phase PAHs in and near to the heavy NAPL, which can easily be misinterpreted as the presence of refined LNAPLs. The use of specific language to identify UVOST® fluorescence such as LNAPL, gasoline, diesel or other specific petroleum, oil or lubricant types are intended to describe the fluorescence response within the limited context of the UVOST® data set, and the actual presence of these NAPLs must be verified with other lines of evidence (sampling, history, etc.) to confirm any stated interpretations. Signal identified and listed in this report as false positives, natural soil, etc. should also be viewed within these same constraints because extremely weathered fuels can occasionally mimic natural soil fluorescence. The analysis and opinions expressed in this report are based upon data obtained from the specific test High Resolution Site Characterization Report – UVOST®-HP Petro Mart #4, Chapel Hill, NC DTC Project No.: 0244.2022 Page 16 version 6.2-April 2022 locations and from other information discussed in this report. Exceptions, if any, are discussed in the accompanying comments section of this report. This report is prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted practices. Reported results shall not be reproduced, except in full, without written approval of Dakota. No warranties, expressed or implied, are intended or made. The hydraulic data acquired from UVOST® tool should be reviewed in conjunction with representative soil samples to best understand soil behavior. Appendix A UVOST®-HP Field Summary Stable Calculated Pre-Probe Final Depth Max Signal Max Signal Initial RE Background Dissipation Water File Log ID Date / Time (ft)(ft)(%RE)Depth (ft)Area (pVs)Area (pVs)(yes or no)Table (bgs) 01-LIF 7/14/2022 9:48 0.0 40.0 4 1 10727 24 N/A N/A 02-LIF 7/14/2022 11:01 0.0 40.1 4 0 10071 0 N/A N/A 03-LIF 7/14/2022 13:04 0.0 39.3 1 0 10742 24 N/A N/A 04-LIF 7/14/2022 13:46 0.0 40.2 5 0 10160 26 N/A N/A 05-LIF 7/14/2022 16:00 0.0 40.0 6 0 10287 12 N/A N/A Total Footage 199.6 (1) Signal responses in the indicated pre-probed regions may not be accurate due to soil disturbance *Indicates that water table data was manually entered from adjacent well measurement (not derived from a dissipation test calculation) Fluorescence UVOST®-HP Field Summary Log Petro Mart #4 Chapel Hill, NC 0-2.3 Top - Bottom (ft) 0-1.8, 11.8-18.4(?), 19.5(?) 0-1.8, 12.4-20.2 N/A 0-1.5 Appendix B UVOST®-HP Logs at 10% RE Appendix C UVOST® Reference Log Flow (Q)Dakota TechnologiesUVOST®‐HP Reference LogCalloutsMain PlotHydraulic PressureEst. KMain Plot:Signal (total fluorescence) versus depth where signal is relative to the Reference Emitter (RE). The total area of the waveform is divided by the total area of the Reference Emitter yielding the %RE. This %RE scales with the NAPL fluorescence. The fill color is based on the relative distribution of each channel’s area to the total waveform area (see callout waveform). The channel‐to‐color relationship and corresponding wavelengths are given in the upper right corner of the plot.Callouts:Waveforms from selected depths or depth ranges showing the multi‐wavelength waveform for that depth. The four peaks are due to fluorescence at four wavelengths and referred to as “channels”. Each channel is assigned a color. Various NAPLs will have a unique waveform “fingerprint” due to the relative amplitude of the four channels and/or broadening of one or more channels. Basic waveform statistics and any operator notes are given below the callout.Hydraulic Pressure (P Dwn):Downhole hydraulic pressure is measured in response to pumping water into the formation at a constant rate. Measurements are logged simultaneously with UVOST data. The resulting log gives insight into the permeability of the soils. Flow (Q):Water is pumped out of the port of the UVOST‐HP probe at a constant rate of 60 mL/min. A change in flow (usually accompanied by an inverse pressure change) is an indicator of hydraulic properties of the soil.Estimated K:The estimated hydraulic conductivity (K) is internally calculated by utilizing pressure and flow data in conjunction with dissipation test(s) performed at each location. The estimated K is calculated by the equation: K = ln(Q/P’)*20.0 + 7.0. Note A: The water table has been calculated and plotted at 24.4’ bgs.Note B:The circle on the Estimated K plot represents the location(s) of dissipation tests. Here, a single dissipation test was performed at 26.67 bgs’.Note C:The highest LNAPL response in this log is present in an area of relatively higher permeability, as indicated by low pressure and higher estimated k values at approximately 26’ to 28’.Note ANote BNote DNote D:The increase in pressure starting near 29’ (transducer is maxed out, 100 psi) is due to low permeability conditions. In this example, the increase in pressure below the LNAPL represents a potential confining unit.Note C *.lif.raw.bin Raw data file. Header is ASCII format and contains information stored when the file was initially written (e.g. date,  total depth, max signal, gps, etc., and any information entered by the operator). All raw waveforms are appended  to the bottom of the file in a binary format. *.lif.plt Stores the plot scheme history (e.g. callout depths) for associated Raw file. Transfer along with the raw file in  order to recall previous plots. *.lif.jpg A jpg image of the OST log including the main signal vs. depth plot, callouts, information, etc. *.lif.dat.txt Data export of a single Raw file. Tab delimited format. No string header is provided for the columns to make  importing into some programs easier. Each row is a unique depth reading. The columns are: 1‐Depth; 2‐Total  Signal (%RE); 3‐Ch1%; 4‐Ch2%; 5‐Ch3%; 6‐Ch4%; 7‐Rate; 8‐EC Depth; 9‐EC Signal; 10‐Hammer Rate Depth; 11‐ Hammer Rate; 12‐Color (RRGGBB). Summing channels 1 to 4 yields the Total Signal. *.lif.sum.txt A summary file for a number of Raw files. ASCII tab delimited format. The file contains a string header. The  summary includes one row for each Raw file and contains information for each file including: the file name, gps  coordinates, max depth, max signal, and depth at which the max signal occurred. *.lif.log.txt An activity log generated autmatically located in the OST application directory in the 'log' subfolder. Each OST unit  the computer operates will generate a separate log file per month. A log file contains much of the header  information contained within each seprate raw file, including: date, total depth, max signal, etc. Data Files Waveform Signal Calculation Common Waveforms (highly dependent on soil, weathering, etc.) Dakota Technologies UVOST® Reference Log An activity log generated automatically is located in the OST application directory in the ‘log’ subfolder. Each OST unit the computer operates will generate a separate log file per month. A log file contains much of the header information contained within each separate Raw file, including: data rate, total depth, max signal, etc. A summary file for a number of Raw files. ASCII tab delimited format. The file contains a string header. The summary includes one row for each Raw file and contains information for each filed including: the file name, GPS coordinates, max depth, max signal, and depth at which the max signal occurred. Data export of a single Raw file. Tab delimited format. No string header is provided for the columns to make importing into some programs easier. Each row is a unique depth reading. The columns are: 1-Depth; 2-Total Signal (%RE); 3-CH1%; 4-Ch2%; 5-CH3%; 6-Ch4%; 7-Rate; 8-EC Depth; 9-EC Signal; 10-Hammer Rate Depth; 11-Hammer Rate; 12-Color (RRGGBB). Summing channels 1 to 4 yields the Total Signal. A .jpg image of the OST log including the main signal vs. depth plot, callouts, information, etc. Stores the plot scheme history (e.g. callout depths) for associated Raw file. Transfer along with the Raw file in order to recall previous plots. Raw data file. Header is ASCII format and contains information stored when the file was initially written (e.g. date, total depth, max signal, GPS, etc., and any information entered by the operator). All Raw waveforms are appended to the bottom of the file in a binary format.*.lif.raw.bin *.lif.plt *.lif.jpg *.lif.dat.txt *.lif.sum.txt *.lif.log.txt CH1 CH2 CH3 CH4 Total 1522           3714         2625        1360                              9221 16.5            40.3          28.5         14.7                                100+               +             +                          = CH1 CH2 CH3 CH4 Total 2339           3585         3433        2674                             11,995 19.4            29.8          28.6         22.2                                100+               +             +                          = Reference Emitter (RE) Example Dakota Technologies UVOST® Reference Log Predominant response in 350nm (UV) and 400nm (violet) channels at 17 to  23‐foot depth interval indicate modest levels of diesel pore saturation.  Note fill color shift to green (as opposed to orange in the 4 to 5‐foot  interval) – visually indicating a difference in NAPL type. The shorter  lifetime in the 350 nm vs subsequent channels is only observed in diesel. Predominant response in 350nm (UV) channel and consistent lifetimes  across all channels at 9 to 13 foot depth interval is consistent with intact  (unweathered) gasoline or kerosene. However, intact gasoline can also be  observed with a blue‐green or slightly green dominant response. Predominant response in 450nm channel with consistent lifetimes  across all channels indicate that the NAPL from 4 to 5‐foot depth  interval is likely a weathered gasoline. An intact gasoline is typically UV  dominant (most fluorescence in the 350nm channel) as noted below. Note low intensity, distinct signal responses separated from zones of  higher NAPL saturation, indicating the presence of discontinuous,  residual NAPL. The waveforms confirm diesel signature – allows the  user to eliminate the possibility of calcite’s fluorescence, which has a  different waveform. Appendix D ISO Map of UVOST Data 21926007253900 LIF Locations LIF Response 0.82 - 1 1 - 2 2 - 3 3 - 4 4 - 5 LIF Locations LIF Response 0.82 - 1 1 - 2 2 - 3 3 - 4 4 - 5 Dakota Technologies LIF Acquisition PetroMart#4 Chapel Hill, NC for: NCDENR Map Prepared: 7/27/2022 Coordinate System: NAD83 North Carolina State Plane (CORS96) US Ft. Appendix E GPR Site Sketch Electric Communications, Telephone/CATV Water Sewer/Drainage Yellow – Gas/Petroleum Pipe Line Unknown ESP Associates, Inc. 2200 Gateway Centre Blvd., Suite 216 Morrisville, NC 27560 (919) 678.1070 2022 SUBSURFACE UTILITY LOCATION SKETCH PROJECT NAME:_______________________________________________ PROJECT Number:_____________________ Sheet ______ of ______ QUALITY CONTROL CHECK PERFORMED BY:_________________ DATE CHECKED:_________________ SURVEYING AND MAPPING PERFORMED BY:_________________ DATE CHECKED:_________________ PRELIMINARY -DO NOT USE FOR CONSTRUCTION THIS IS NOT A SURVEY. THE DASHED UTILITY LINES SHOWN HEREON WERE DESIGNATED AND PAINTED ON _________ ____, 2022, BUT WERE NOT SURVEYED. THE LOCATIONS ARE SCHEMATIC IN NATURE AND ARE NOT TO SCALE. THE DESIGNATED UTILITIES WERE NOT FIELD LOCATED BY ESP. Pedestal Transformer Water Meter Handhole Utility Pole Back Flow Preventer Manhole Light Pole Fire Hydrant Valve Gas Meter Pump Station EOI End of Information Test Hole Cleanout Utilities Legend E W CO SG W EOI EOI Petro-Mart Chapel Hill RD 1 1 July 14 Appendix F GPS Coordinates Location Name Easting Northing 01-LIF 1972918.7 763047.4 02-LIF 1972900.3 763049.3 03-LIF 1972877.5 763035.3 04-LIF 1972869.2 763067.5 05-LIF 1972860.1 763050.4 GPS Coordinates