Former Waddell Compressor Station Accelerated Site Closure Via Transmissivity Testing and Plume Stability Analysis: Former Waddell Compressor Station International Petroleum Environmental Conference Denver, Colorado October 31, 2018

Overview Site Location and Conditions Approach to Closure LNAPL Transmissivity (oil/water ratio) LNAPL Transmissivity (mobile dual phase extraction) Groundwater stability analysis Path Forward Slide 2

Waddell Site History West Texas Permian Basin 1995 first groundwater monitoring wells installed 2009 biosparge remediation system installed 2017 additional GW delineation wells installed 2018 LNAPL transmissivity, mobile dual phase extraction, and plume stability analysis Key points: Site has been monitored for over 20 years and active remediation for 9 Robust dataset to perform risk-based evaluation Site is appropriate to close using risk-based evaluation per the RRC Operator Cleanup Guidance Slide 3

Site Location Slide 4 Waddell Key points: Northwest of Crane, TX In active oil field Permian basin Surrounded by other pipelines No occupied structures for miles Waddell Source: http://www.rrc.state.tx.us Slide 4

Texas Regulatory Setting TCEQ provides detailed guidance for risk-based NAPL management (TRRP-32) Extensive analysis, reporting and documentation required Allows closure with NAPL in place on a site-specific basis RRC does not specifically address NAPL, but does provide options… No specific NAPL guidance like TCEQ Allows risk-based closure within Operator Cleanup Program Transmissivity can be a key line of evidence to stop hydraulic recovery and achieve closure Since we’re in Texas, here are the specific programs that address site cleanup and NAPL transmissivity in Texas Slide 5

Approach to Closure Perform a risk-based evaluation of the Site: Waddell Perform a risk-based evaluation of the Site: Evaluate NAPL transmissivity and recoverability Plume delineation Plume stability Deliver risk-based analysis to RRC to support site closure Implement institutional controls to prevent exposure to GW exceeding RRC MCLs (work with landowner) Achieve Site closure Key points: Site has been monitored for over 20 years and active remediation for 9 Robust dataset to perform risk-based evaluation Site is appropriate to close using risk-based evaluation per the RRC Operator Cleanup Guidance Slide 6

LNAPL Transmissivity Provides quantitative value that is widely accepted and endorsed Analogous to aquifer (groundwater) transmissivity Tells us “how much how fast” can be recovered Can indicate the point where hydraulic recovery is infeasible (ITRC, 2009) Acceptable to RRC as line of evidence for closure Key Point: RRC may already know this, but here is a refresher on Tn concepts…background of what Tn means and why we test for it. Hawthorne, J.M., Kirkman, A., (July 2011). Demystifying NAPL Science for the Remediation Manager. Applied NAPL Science Review (ANSR) Vol 1, Issue 7. Download at: http://www.h2altd.com/ansr Slide 7

Multiple transmissivity measurement methods are available in ASTM E2856 We used two methods at Waddell Measuring LNAPL Tn Now that we have the concepts down, let’s talk about common ways to test Tn and their pros/cons depending on the setting Three methods are most commonly used and are discussed further in the next few slides Slide 8

LNAPL Transmissivity Extensive network of monitoring wells with data beginning in 1995 Overall lateral extent of NAPL body is stable to decreasing Performed oil/water ratio transmissivity testing at five wells in April 2018 Re-emphasize here that MW-21R is not a surprise to see LNAPL Lateral extent of LNAPL is stable to diminishing except for MW-21R (we can explain this further if needed) Apparent LNAPL thicknesses range from 0.16 ft (MW-17) to 1.35 ft (MW-24). That’s typical of the past few years. MW-32 Slide 9

LNAPL Tn Testing (oil/water ratio) Performed oil/water ratio testing using GEI’s patented H2AWK™ Key point: NAPL/water ratio test is a direct way of measuring Tn and provides reliable, accurate results. Tn calculations in accordance with ASTM E 2856-13. Hydraulic recovery is not feasible based on low transmissivity Slide 10

LNAPL Tn Testing (MDPE) Landowner requested mobile dual phase extraction (MDPE) Extracted at 3 wells in August 2018 for ~6.5 hrs each Collected necessary data to calculate Tn LNAPL Tn Testing (MDPE)

LNAPL Tn Testing (MDPE) Well ID Tn MW-4 2E-05 MW-11 1E-05 MW-21R 3E-02 <0.01 gals of LNAPL recovered as fluid (sheen) ~1,180 gals of water recovered ~0.5 gals of LNAPL recovered as vapor ~42 gals of propane used to destroy <1 gal LNAPL Fairly unique circumstance where we were able to calculate transmissivity using two different methods (MDPE and NAPL/water ratio) The results are similar and we draw the same conclusion: NAPL is not hydraulically recoverable Tn <0.03 ft2/day Confirms oil/water ratio results LNAPL is not hydraulically recoverable

Groundwater Elevation and Quality Class 2 aquifer GW ~50-55 ft below ground surface Flow is generally south LNAPL present in some wells BTEX and TPH detected in some wells Key points: GW flow is consistently to the south/southeast. Highest benzene concentrations are near the center of the Site. LNAPL presence/absence Slide 13

Dissolved Phase Delineation - Benzene MCL exceedances location in the interior of the monitoring network MW-21R did exceed for benzene NAPL has been observed in this well Additional delineation well recently installed down-gradient New well installed recently for delineation MW-32 Slide 14

Dissolved Plume Stability Analysis Stability evaluated for benzene, ethylbenzene, toluene, and TPH Used last 10 years of data (2006 to 2017) Groundwater Spatiotemporal Data Analysis Tool (GWSDAT) (Jones et al. 2014). Mann-Kendall trends for individual wells The spatiotemporal tool for plume scale analysis Slide 15

Mann-Kendall Evaluation Benzene increasing trend at MW-02, MW-05, MW-08 (near center of plume) MW-02, MW-08 historically exhibited LNAPL Toluene increasing trend at MW-13 (upgradient), but well below MCL Does not represent significant deviation from historic conditions Overall, BTEX and TPH are stable to decreasing across the site Discuss outliers and where they’re located. And why we’re not concerned with them (i.e., they are in the middle of the Site nearby residual LNAPL) Talk about delineation to the north and east plus 21 and 21R Slide 16

Spatiotemporal Evaluation Slide 17

Evaluation Summary Delineation is complete for LNAPL and dissolved phase with one data gap: Additional well recently installed downgradient of MW-21R LNAPL body is laterally and vertically stable Remaining LNAPL is not recoverable Dissolved phase plumes are stable to decreasing Key Points: Discuss data gaps Emphasize the site is well characterized Slide 18

Path Forward Confirm delineation in downgradient direction (ongoing) Shut down biosparge system (July 2018) Deliver transmissivity and plume stability results to RRC (Fall 2018) Finalize deed restriction with land owner (Fall 2018) Achieve site closure (Spring 2019) Slide 19

Questions? Thomas Daigle (tdaigle@geiconsultants.com) Mike Hawthorne (mhawthorne@geiconsultants.com) Lisa Reyenga (lreyenga@geiconsultants.com) (GEI Consultants, Denver, CO, USA) David White (David_white@kindermorgan.com) (Kinder Morgan, Houston, TX, USA)