Real-Time High Resolution Characterization of Coal Tar DNAPL Impacts at the Søllerød Gasworks Site Using DPT Laser-Induced Fluorescence

Transcription

1 Real-Time High Resolution Characterization of Coal Tar DNAPL Impacts at the Søllerød Gasworks Site Using DPT Laser-Induced Fluorescence Neal D. Durant, Ph.D. 10 March 2014

2 Co-Authors and Partners Mariam Wahid Mads Terkelsen Torben Højbjerg Jørgensen Jarl Dall Jepsen Christian Buch Gary Wealthall Dave Liefl R. Dylan Walker Danielle Rowlands

3 Objectives Successfully perform LIF-TarGOST survey (TarGOST survey) of coal tar DNAPL source area, using intact soil core samples to calibrate; Improve spatial delineation of coal tar impacts; Develop a three-dimensional conceptual site model (CSM) of coal tar distributions at the Site; Estimate DNAPL mass using the LIF-TarGOST calibration and historic site data; and Generate a dataset to support surgical and efficient remedial design for DNAPL source area

4 Program Summary x 5.25 m sampling grid TarGOST borings to depths of 14 to 18 mbgs 3. Cone penetrometer (CPT) data collected at each boring location to improve understanding of lithology soil analytical samples collected from seven DPT soil cores, analyzed for TPH, BTEX, and naphthalene to calibrate the TarGOST profiles 5. Core samples screened for DNAPL via PID, visual inspection, and hydrophobic dye (Sudan IV) 6. Use ESRI ArcGIS and CTech Environmental Visualization Systems software (EVS) to visual results, estimate coal tar mass.

5 Introduction to Laser-Induced Fluorescence using Tar-Specific Green Optical Screening Tool (TarGOST)

6 Laser Induced Fluorescence (LIF) profiling

7 Laser Induced Fluorescence Tar-specific Green Optical Screening Tool, Tar-GOST Scatter Tar Fingerprint % Signal Reference Emitter Response = Σarea under SAMPLE fluorescence peaks/σarea under REFERENCE fluorescence pea Area under SAMPLE scatter peak/area under REFERENCE scatter peak

8 Converting LIF Response to DNAPL Saturation Calibration data from EPRI (2006) Data from EPRI (2004) PAH Concentration (ppm) NAPL Saturation PAH Concentration (ppm)

9 EPRI (2006) Indicators <10%RE c. 50%RE > 100%RE No indication of the presence of coal tar Marginally Coal Tar- Impacted Soils Definitive Indication of Coal Tar-Impacted Soils

10 TarGOST Calibration Curve Dakota Technologies Inc. PAH Concentration (ppm) LIF Tool and Green Laser Spiked NAPL Concentration (ppm)

11 Mass Calculation V = volume of DNAPL-impacted soil n = porosity (0.3) S r = average residual saturation calculated using the TarGOST data (4.6% for %RE 50 and 0.03% for %RE >10 and < 50) ρ DNAPL = DNAPL density (1,087 kg/m 3 )

12 Søllerød Gasværk Site, Holte

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14 Søllerød Gaswærk Site, 1954 Site of former tar lagoon Gas Holder

15 Total Petroleum Hydrocarbon (TPH) in Soil, Pre-TarGOST

16 Benzene in Groundwater, Pre-TarGOST

17 Cross-Section of Coal Tar Distribution, Pre-TarGOST

18 TarGOST Investigation Results

19 Sampling Network

20 Highlights from TarGOST Investigation Cores TarGOST Rig DPT Rig Coal tar from PB101 Coal tar in core C4B

21 Highlights from TarGOST Investigation CPT/TarGOST Rods exiting rig

22 Total Petroleum Hydrocarbon (TPH) in Soil, Post-TarGOST

23 xample TarGOST & CPT Profiles B2

24 Site Geology Cores, CPT, + EVS Fill Peat Clay/silt Fill Peat Clay/sil t Silt/san d San d Sand Silt/san d

25 %RE Site-Specific TarGOST Calibration Curve 50% RE ~ = 728 ppm LIF Tool and Green Laser Total Hydrocarbon Concentration (ppm)

26 %RE EPRI Residual Tar Saturation Curve with Site-Specific Analytical Data and Calculated TarGOST Saturation LIF Tool and Green Laser Hydrocarbon Concentration (ppm)

27 TarGOST Results

28 TarGOST Interpolation Results - EVS Data were interpolated using Environmental Visualization System (EVS) software TarGOST %RE > 50%

29 EVS enables 3-D, rotable view of DNAPL distribution TarGOST Signal (%RE) 100% 50% 10% 0% TarGOST Data Set with Lithology (Facing North-East) %RE > 50 Lithology Fill Peat Clay/Silt Silt/Sand TarGOST Data Set with Lithology (Facing South-East) %RE > 50

30 Visualizing Coal Tar Occurrence by Lithologic Layer

31 Estimated Mass Calculated by EVS EVS uses a kriging algorithm to estimate probable values at nodes across model grid Calculation Variables X/Y/Z Grid Resolution: 60/60/100 Horizontal/Vertical Weighting Factor: 10 Porosity: 0.3 Residual Saturation for >50%: Residual Saturation for >10% and <50%: NAPL Density: 1087 kg/m3 Soil Bulk Density: 1200 kg/m3

32 Estimated Mass Calculated by EVS % RE Range Concentration Range (ppm) Soil Volume (m 3 ) < 10 < 37 9,719 9,442 4,378 DNAPL Mass (tonnes) Min Nominal Max Min Nominal Max > 10 and < 50 > 37 and < , > 50 > TOTAL 10,307 10,303 10,

33 TarGOST Investigation Summary 1. TarGOST sampling improved spatial resolution (vertical discretization) of DNAPL distribution 2. DNAPL spread over a larger horizontal area than previously understood 3. DNAPL occurrence more vertically discrete than previously understood 4. The DNAPL is typically visualized in thin depth intervals of up to approximately 0.5 m in thickness and depths anywhere from approximately 1 to 14 mbgs. 5. The majority (66%) of the DNAPL mass is present in the shallow Peat unit, the remaining 34% in deeper silt and clay layers 6. Coal tar DNAPL mass in the investigation area at the site ranges from 2.1 to 3.2 tonnes

34 Questions?