13 Final_Site_SD031_OES_ICER_04Mar2020_DK01Submittal.pdf

TRAVIS AIR FORCE BASE, CALIFORNIA

PERFORMANCE-BASED CONTRACT

Final

Site SD031 Optimized Exit Strategy Implementation Completion and Effectiveness Report

USACE Contract No. W912QR-12-D-0005

Task Order DK01

Prepared for:

U.S. Army Corps of Engineers Air Force Civil Engineer Center Omaha District

Prepared by:

March 2020

F i n a l

Site SD031 Optimized Exit Strategy Implementation Completion and

Effectiveness Report

Travis Air Force Base, California

Prepared for

U.S. Army Corps of Engineers, Omaha District and

Air Force Civil Engineer Center

March 2020

2485 Natomas Park Drive Suite 600

Sacramento, CA 95833

SITE SD031 OES ICER i

AX1218192002SAC/482366CH

Contents

Section Page

1 Introduction .......................................................................................................................1-1

1.1 Site Background ...............................................................................................................1-1

1.2 Optimized Exit Strategy Implementation Completion and Effectiveness Report

Guidance ..........................................................................................................................1-2

2 Performance and Technical Objectives ................................................................................2-1

3 Overview of Remedial Progress and Status ..........................................................................3-1

3.1 Overview of Site Advancement .......................................................................................3-1

3.2 Performance Model Update ............................................................................................3-3

3.3 Continual Improvement Efforts .......................................................................................3-6

4 Discussion of Performance and Effectiveness.......................................................................4-1

Tables

3-1 Site SD031 Gravel Chimney and Injection Well Construction Details .........................................3-3 3-2 Site SD031 1,1-DCE Concentration Changes since 2012 Baseline...............................................3-5

Figures

1-1 Site SD031 Map

3-1 2012 Baseline and 2019 1,1-DCE Distribution at Site SD031 3-2 Site SD031 Geologic Cross Section A-A’ 3-3 Site SD031 Updated Performance Model

Appendixes

A Acronyms and Abbreviations B References

SITE SD031 OES ICER 1-1

SECTION 1

Introduction

This Site SD031 Optimized Exit Strategy (OES) Implementation Completion and Effectiveness Report (ICER) documents the implementation and effectiveness of the contracted Site SD031 optimization activities presented in the Optimized Exit Strategy Performance Plan Sites SD031 and SD034 (OES Plan) (CH2M HILL, 2018a). The OES Plan describes the optimization activities that will occur at Sites SD031 and SD034 under the Performance-based Contract (PBC) W912QR-12-D-0005, Task Order DK01, Modification 10 to reduce the time required to achieve site closeout (SC). The OES Plan also summarizes the remaining activities that are expected to be required after the PBC has ended (post-PBC).

The Site SD031 OES was developed by completing an optimization evaluation that considered historical site data, performance of the existing remedy, potential risk posed by the site, and projected life-cycle costs. The OES presented in the OES Plan was determined to be the most efficient and cost-effective way to reduce the long-term cost and risk associated with Site SD031. As indicated in the OES Plan, a technology demonstration (TD) has been initiated at Site SD031 to expedite the path to SC. Operation of the TD is expected to reduce cleanup times for the known groundwater chemicals of concern (COCs).

1.1 Site Background

Site SD031 is located in the northeastern portion of Travis Air Force Base (AFB) and encompasses Facility 1205 (Figure 1-1). Facility 1205 was constructed in 1957, and operations included the maintenance and repair of diesel-powered generators. Historical aerial photographs taken from 1958 to 1963 indicate that Facility 1205 may have also been used as an aircraft maintenance hangar during this time. Wastes generated at the facility include oils, antifreeze, and solvents. A wash rack, located south of the facility, is still used to clean diesel engine parts; the wash rack discharges to an oil/water separator (OWS). Historical accidental releases in the vicinity of this wash rack appear to have been the cause of known groundwater contamination. Since the discovery of contamination at the site, proper material handling and process controls were implemented to prevent additional releases. Site SD031 is being addressed under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) program. The East Industrial Operable Unit Remedial Investigation Report (EIOU RI Report) (Roy F. Weston, Inc. [Weston], 1995) and North/East/West Industrial Operable Unit Soil, Sediment, and Surface Water Record of Decision (NEWIOU Soil ROD) (Travis AFB, 2006) determined that no further action (NFA) was required to address Site SD031 soils; however, COCs exceeded cleanup goals in groundwater.

Based on the NFA designation for site soil in the EIOU RI Report (Weston, 1995) and NEWIOU Soil ROD (Travis AFB, 2006), groundwater was the only media identified as requiring remediation at Site SD031 when the PBC was awarded. However, during the initial installation of the Site SD031 TD in 2014, soil staining was unexpectedly encountered. Based on the subsequent review of historical records/ reports and interviews conducted with long-time Civil Engineer Maintenance Inspection and Repair Team personnel, it is likely that spillage occurred during cleaning and refueling of the interceptor jets and transport planes in the laydown area, as well as potentially during historical maintenance activities of the diesel generators and large heating, ventilation, and air conditioning (HVAC) systems at Facility 1205.

A soil RI was initiated at Site SD031 in 2015 and was completed in 2017. Investigation results are documented in the Site SD031 Soil Remedial Investigation/Feasibility Study (Site SD031 Soil RI/FS) (CH2M HILL, 2019). Because no decision document addressing the recently discovered soil contamination exists, the Site SD031 OES Plan focuses on the groundwater contamination addressed in the Final Groundwater Record of Decision (Groundwater ROD) (Travis AFB, 2014). The soil contamination will be

SECTION 1: INTRODUCTION

1-2 SITE SD031 OES ICER

AX1218192002SAC/482366CH

addressed under a separate contract. Groundwater COCs at Site SD031 documented in the Groundwater ROD are 1,1-dichloroethene (DCE), 1,2-dichloroethane (DCA), benzene, carbon tetrachloride, chloroform, cis-1,2-DCE, trichloroethene (TCE), and vinyl chloride. 1,1-DCE is the most widespread of the COCs and is expected to have the greatest impact on the goals of the OES.

1.2 Optimized Exit Strategy Implementation Completion

and Effectiveness Report Guidance

This OES ICER was prepared in accordance with the relevant components of the Optimized Exit Strategy Compendium for Performance-Based Remediation (Air Force Civil Engineer Center [AFCEC], 2014).

Based on AFCEC guidance, this report includes the following:

• Performance and technical objectives

• Overview of remedial progress and status

• Discussion of performance

• Discussion of effectiveness

MW574X31

MW573X31

MW571X31

MW569X31

MW568X31

EW565X31

MW798X28

MW02SX06

MW02DX06

IW2331X31

MW1731X31

MW1730X31

MW1729X31

MW1726X31

MW1725X31

MW1743X06

MW134X04

MW752X04

MW265X04

MW302X03

MW206X03

MW205X03

MW133X03

MW1030X04

MW1002X04

MW572X31

MW570X31

EW567X31

EW566X31

IW2332X31

IW2203X31

IW2202X31

IW2201X31

IW2200X31

IW2199X31

IW2198X31

IW2197X31

MW1741X31

MW575X31

MW1727X31

IW2776X31

IW2777X31

IW2774X31

IW2775X31

BAKER

ST

A

A'

VICINITY MAP

FIGURE 1-1

SITE SD031 MAP

SITE SD031 OPTIMIZED EXIT STRATEGY

IMPLEMENTATION COMPLETION AND

EFFECTIVENESS REPORT

TRAVIS AIR FORCE BASE, CALIFORNIA

UNK \\BROOKSIDEFILES\GIS_SHARE\ENBG\00_PROJ\A\AIRFORCE\TRAVISAFB\MAPFILES\2019\SD031_ICER_REPORT\FIGURE1-1_SITEMAP_SD031.MXD SSCOPES 1/8/2020 11:43:03 AM

0 230115

FEET

Legend

? INJECTION WELL INSTALLED IN 2017

? INJECTION WELL INSTALLED IN 2015

! GROUNDWATER MONITORING WELL

_̂ EXTRACTION WELL

+ GRAVEL CHIMNEY INSTALLED IN 2015

A A' CROSS SECTION LINE

GROUNDWATER FLOW DIRECTION

SURFACE WATER

FENCE

TREATED WATER PIPING

INACTIVE UNTREATED WATER PIPING

INACTIVE TREATED WATER PIPING

ERP SITE BOUNDARY

WETLAND FEATURES

VERNAL POOL

EW566X31

GC2339X31

GC2338X31

GC2337X31

GC2336X31

GC2335X31

GC2334X31

IW2332X31

IW2198X31

SITE SD031 OES ICER 2-1

SECTION 2

Performance and Technical Objectives

The PBC-awarded performance objective for Site SD031 is to implement an OES. The following PBC and post-PBC technical objectives will be achieved to advance the site toward SC (CH2M HILL, 2018a):

• Strive to achieve a 90 percent reduction in the mean 1,1-DCE concentration by the end of the period of performance (POP) of the PBC (PBC objective).

• Determine nature and extent of any previously unidentified groundwater COCs that may have leached to groundwater from the recently identified contaminated soil (post-PBC objective).

• Select and implement remedy for recently identified soil contamination (post-PBC objective).

• If applicable, select groundwater remedy (which would require preparation of a Groundwater Proposed Plan and Groundwater ROD) and implement for newly identified groundwater COCs (post-PBC objective).

• Continue the reduction of groundwater monitoring costs through optimization evaluations conducted at appropriate intervals, and decommission monitoring wells as they are no longer needed for the Groundwater Remediation Implementation Program (GRIP) (post-PBC objective).

• Achieve regulatory and U.S. Air Force (Air Force) definition of response complete (RC) (post-PBC objective).

• Achieve unrestricted regulatory site closure (post-PBC objective).

• Perform final well decommissioning of all remaining monitoring wells and remediation infrastructure after regulatory site closure to achieve the Air Force definition of SC (post-PBC objective).

The following performance monitoring metric was identified to assess progress toward achieving performance objectives: The mean concentration of 1,1-DCE in the source area should be reduced by 70 percent by 2019 and by 90 percent by the end of the POP of the PBC (PBC metric).

SITE SD031 OES ICER 3-1

SECTION 3

Overview of Remedial Progress and Status

At the time of this report, the primary PBC objective listed in the OES Plan has been completed.

This section summarizes the activities completed to achieve this objective and the remedial progress made to date at Site SD031.

3.1 Overview of Site Advancement

The primary objective of the OES activities during the PBC is to achieve a 90 percent mean reduction in 1,1-DCE concentrations from the 2012 baseline within the source area, as monitored at a minimum of annually by the performance monitoring wells. The Groundwater ROD (Travis AFB, 2014) selected monitored natural attenuation (MNA) as the final remedy to address residual groundwater contamination at Site SD031. In addition to the selected MNA remedy, a TD was initiated at Site SD031 in 2014 to evaluate if a gravel chimney recirculation system could reduce the time and life-cycle costs required to achieve SC. The objective of the TD is to use emulsified vegetable oil (EVO) injection wells and recirculation of groundwater through gravel chimneys to distribute dissolved organic carbon (DOC) horizontally in the subsurface to support enhanced reductive dechlorination (ERD) of 1,1-DCE.

Prior to implementing the TD, the Site SD031 Technology Demonstration Work Plan (Site SD031 TD Work Plan) (CH2M HILL, 2014) was prepared and submitted for review and approval by the U.S. Army Corps of Engineers (USACE), the Air Force, and the regulatory agencies, which include the U.S. Environmental Protection Agency (EPA), the California Department of Toxic Substances Control (DTSC), and the San Francisco Bay Regional Water Quality Control Board (Water Board). The Site SD031 TD Work Plan provided a detailed conceptual site model (CSM), summarized the pre-design investigation activities, and presented the TD design. Installation of the physical components of the TD was performed between October 2014 and April 2015 and included the following:

• Installation of six (6) gravel chimneys (GC2334x31 through GC2339x31) in the northwestern portion of the plume to target the highest 1,1-DCE concentrations in groundwater. Iron pyrite sands were added to the gravel chimneys to support abiotic degradation of 1,1-DCE.

• Installation of nine (9) injection wells (IW2197x31 through IW2203x31, IW2331x31, and IW2332x31) downgradient of the gravel chimneys.

• Installation of electric submersible pumps to replace the old educator pumps in existing extraction wells EW566X31 and EW567X31.

• Installation of new groundwater conveyance lines to facilitate recirculation through the gravel chimneys.

• Installation of a new electrical panel and pump control panels for EW566X31 and EW567X31 inside the control room at the former North Groundwater Treatment Plant (NGWTP).

• Collection of baseline groundwater samples from the six (6) gravel chimneys (GC2334x31 through GC2339x31), nine (9) new injection wells (IW2197x31 through IW2203x31, IW2331x31, and IW2332x31), and seven (7) performance monitoring wells (EW565x31, EW566x31, EW567x31, MW568x31, MW571x31, MW572x31, and MW574x31).

• Injection of approximately 118,877 gallons of 3.5 percent EVO solution, followed by injection of approximately 41,269 gallons of chase water, into the six (6) gravel chimneys and nine (9) new injection wells.

SECTION 3: OVERVIEW OF REMEDIAL PROGRESS AND STATUS

3-2 SITE SD031 OES ICER

AX1218192002SAC/482366CH

Following TD startup, performance monitoring results indicated that aquifer conditions had become more reducing within the TD area at Site SD031. However, a widespread, sustained increase in DOC concentrations above 2015 baseline values was not evident. It appeared that DOC was being consumed at close to the rate at which it was being supplied (CH2M HILL, 2017). Thus, while ERD appeared to be successful at reducing COC concentrations, the DOC initially introduced to the TD area was insufficient to evaluate the effectiveness of the DOC distribution method. Consistent with the design logic and contingencies presented for Site SD031 in the OES Plan, the TD was optimized in 2017 to increase the amount of DOC in circulation within the aquifer by installing additional injection wells and injecting a new EVO product with a smaller (nano- to micron-scale) droplet size (NanoEVO). NanoEVO was selected as the injectant because it allows for greater distribution of DOC into finer sediment matrices compared to the previous EVO product used during the TD. Installation of the injection wells and injection activities were completed in accordance with the Site SD031 TD Work Plan (CH2M HILL, 2014). Installation of the physical components of the follow-on TD optimization to support the OES was performed between April and December 2017 and included the following:

• Installation of four (4) new injection wells (IW2774x31 through IW2777x31) within the portion of the plume where 1,1‐DCE concentrations exceeded 20 micrograms per liter (μg/L).

• Collection of baseline groundwater samples from the four (4) new injection wells.

• Injection of approximately 2,005 gallons of 18.5 percent NanoEVO solution into the six (6) gravel chimneys; injection of approximately 27,151 gallons of 4.2 percent NanoEVO solution followed by 11,265 gallons of chase water into the four (4) new injection wells.

The locations of the gravel chimneys, injection wells, and conveyance lines installed during the 2015 TD implementation and new injection wells installed during the 2017 optimization are shown on Figure 1-1.

Table 3-1 presents the construction details for the gravel chimneys and injection wells installed in 2015 and injection wells installed in 2017. The 2012 baseline 1,1-DCE concentrations and 2019 performance monitoring 1,1-DCE concentrations detected at Site SD031 are presented on Figure 3-1.

Following installation of the TD infrastructure in 2015 and follow-on optimization in 2017, the Site SD031 Technology Demonstration Construction Completion Report (Site SD031 TDCCR) (CH2M HILL, 2015) and Emulsified Vegetable Oil Sites FT004, SS015, SD031, and SD036 Injections Technical Memorandum (EVO Sites FT004, SS015, SD031, and SD036 Injections TM) (CH2M HILL, 2018b) were prepared and submitted to USACE, the Air Force, and the regulatory agencies for review and approval. The Site SD031 TDCCR and EVO Sites FT004, SS015, SD031, and SD036 Injections TM provide detailed documentation of the Site SD031 TD installation and subsequent TD optimization. Any additional optimization activities will be documented in a technical memorandum or the Annual Groundwater Remediation Implementation Status Reports (GRISRs).

As mentioned previously, a soil RI was initiated at Site SD031 in 2015 to investigate the area of soil contamination identified during the installation of the TD infrastructure in 2014. Prior to implementing the RI, the Site SD031 Soil Remedial Investigation Work Plan (CH2M HILL, 2016) was prepared and submitted for review and approval by the USACE, the Air Force, and the regulatory agencies. The main purpose of the RI was to identify the Human Health Risk Assessment and Ecological Risk Assessment– related COCs in soil, soil vapor, and groundwater, and support an evaluation of remedial alternatives in an FS. Following completion of the RI in 2017, the Site SD031 Soil RI/FS (CH2M HILL, 2019) was prepared and submitted to USACE, the Air Force, and the regulatory agencies for review and approval. The Site SD031 Soil RI/FS provides detailed documentation of the RI analytical results, risk assessment conclusions, and remedial alternatives evaluated during the FS. The soil contamination and remedial action will be addressed under a separate contract.

3-3

TABLE 3-1

Site SD031 Gravel Chimney and Injection Well Construction Details Site SD031 Optimized Exit Strategy Implementation Completion and Effectiveness Report, Travis Air Force Base, California

Well Location

Screen Interval

(feet bgs)

Filter Pack Interval

(feet bgs)

Borehole Depth

(feet bgs)

Borehole Diameter (inches)

Well Casing Diameter (inches)

Top of Casing Elevation

(feet amsl)

2014–2015 Gravel Chimneys*

GC2334x31 13.5 to 33.5 5 to 34 34 18 2 61.87

GC2335x31 13.9 to 33.9 5 to 34.4 34.4 12 2 62.10

GC2336x31 15.3 to 35.3 5 to 35.8 35.8 12 2 61.95

GC2337x31 15.5 to 35.5 5 to 36 36 12 2 61.98

GC2338x31 17.5 to 37.5 5 to 38 38 12 2 62.25

GC2339x31 17 to 37 5 to 37.5 37.5 18 2 61.97

2014–2015 Injection Wells

IW2197x31 14 to 39 12 to 39.5 39.5 8 2 62.32

IW2198x31 16 to 36 14 to 39 39 8 2 62.39

IW2199x31 17 to 37 15 to 39 39 8 2 61.80

IW2200x31 16 to 36 13 to 39.5 39.5 8 2 61.65

IW2201x31 17 to 37 14 to 39 39 8 2 61.80

IW2202x31 17 to 37 15 to 39 39 8 2 61.00

IW2203x31 17 to 37 14 to 38.5 38.5 8 2 61.05

IW2331x31 14.5 to 34.5 12.5 to 35 35 8 2 62.25

IW2332x31 16 to 36 14 to 37.5 38.5 8 2 62.24

2017 Injection Wells

IW2774x31 19.5 to 39.5 15.5 to 40 40 8 2 60.01

IW2775x31 11 to 31 9 to 34.5 34.5 8 2 59.76

IW2776x31 11 to 31 9 to 32 35 8 2 59.99

IW2777x31 11 to 31 9 to 35 35 8 2 60.51

* The 2-inch-diameter wells are internal to the gravel chimney.

Notes:

amsl = above mean sea level bgs = below ground surface

3.2 Performance Model Update

The performance model for the Site SD031 TD was presented in the OES Plan. Performance monitoring of the TD is executed under the GRIP. The most recent GRIP sampling event was conducted in the fourth quarter (4Q) of 2019. Data collected through 4Q19 were used to update the performance model discussed in this section.

SITE SD031 OES ICER

3-4 SITE SD031 OES ICER

AX1218192002SAC/482366CH

The following performance monitoring metric is used to assess progress toward achieving performance objectives: the mean concentration of 1,1-DCE should be reduced by 70 percent by 2019 and by 90 percent by the end of the POP of the PBC (PBC metric). Concentration reduction goals are monitored at the following performance monitoring wells: EW565x31, EW566x31, EW567x31, MW571x31, and MW574x31 (CH2M HILL, 2018a). Achievement of the concentration reduction metrics are determined by calculating the sum of 1,1-DCE concentrations from the performance monitoring wells to determine the mean concentration reduction from these wells as a whole. Concentration reductions in the performance monitoring network are evaluated against 2012 baseline 1,1-DCE concentrations.

The 1,1-DCE concentrations at each of the performance monitoring wells, calculated sum of 1,1-DCE concentrations, and mean of the sum of 1,1-DCE concentrations through 4Q19 are provided in Table 3-2.

The OES requirement during the PBC of a 70 percent mean concentration reduction is considered fulfilled once the mean 1,1-DCE concentration listed in Table 3-2 reaches 20.6 µg/L or less. The 90 percent mean concentration reduction is considered fulfilled once the mean 1,1-DCE concentration listed in Table 3-2, reaches 6.9 µg/L or less. As indicated in Table 3-2, the 70 percent reduction was achieved in April 2016 (86 percent), and the 90 percent reduction objective was achieved in April 2017 (92 percent).

Figure 3-1 presents the most recent 1,1-DCE distribution (4Q19) for Site SD031 and provides a comparison to the 2012 baseline 1,1-DCE distribution. Figure 3-1 shows that 1,1-DCE concentrations have decreased within the targeted area, as anticipated, such that a 94 percent mean concentration reduction has been achieved. Figure 3-2 is a cross section through the Site SD031 1,1-DCE plume.

The updated performance model illustrating the observed changes in 1,1-DCE concentrations compared to expected trends in concentration reductions is presented on Figure 3-3. As indicated on Figure 3-3, the 1,1-DCE reduction trend has significantly improved since 2015, and the PBC contract requirements have been achieved.

The performance model presents expected concentration reduction trends in a simple graphical format for the following scenarios:

• Ideal Range: performance monitoring data that plot within this range indicate that concentration reductions are proceeding under the ideal scenario where concentration reductions are quickly achieved. This portion of the graph is created by considering the remedial design, site-specific CSM, experience at similar enhanced in situ bioremediation (EISB) sites, available literature values, expected longevity of the substrate selected, and the expected substrate enhancement frequency.

• Potential Process Improvement Range: performance monitoring data that plot within this range indicate that observed concentration reduction trends are outside of the ideal range, but are still proceeding as needed to achieve PBC contract milestones. Performance monitoring data trending within this range should be closely monitored to evaluate whether additional action should be considered in the future.

• Contingency Action Range: performance monitoring data that consistently plot within this range indicate that observed concentration reductions may not be trending toward contract requirements and a contingency action (e.g., additional remedy optimization) may need to be considered. The upper bound of this range is estimated from historical concentration data suitable for calculating baseline degradation rates from pre-OES treatment conditions (e.g., status quo condition based on pre-optimization degradation rates).

3-5

TABLE 3-2

Site SD031 1,1-DCE Concentration Changes since 2012 Baseline Site SD031 Optimized Exit Strategy Implementation Completion and Effectiveness Report, Travis Air Force Base, California

Well Name

Baseline

(µg/L)

April

(µg/L)

April

(µg/L)

January

(µg/L)

October

(µg/L)

April

(µg/L)

April

(µg/L)

April

(µg/L)

April/October

(µg/L)

EW565x31 0.51 0.26 J 1.7 1.7 0.96 J 0.22 J 0.8 (U) 0.2 J 0.23 (U)

EW566x31 307 43.5 21.5 60 J 54 5 0.8 (U) 0.8 (U) 0.23 (U)

EW567x31 34.4 J+ 73.6 195 120 110 29 J- 2.7 0.8 (U) 0.28 J

MW571x31 1.2 0.19 (U) 0.33 J 0.4 (U) 0.8 (U) 0.8 (U) 0.8 (U) 0.8 (U) 0.23 (U)

MW574x31 0.9 3.5 8.6 6.1 5.7 13 22 24 18

Sum of 1,1-DCE Concentrations 344 121 227 188 171 48 27 27 19

Mean of the Sum of 1,1-DCE Concentrations 68.8 24.2 45.4 37.6 34.3 9.6 5.4 5.3 3.8

1,1-DCE Concentration Representing a 70 Percent Reduction of the Mean

20.6 -- -- -- -- -- -- -- --

1,1-DCE Concentration Representing a 90 Percent Reduction of the Mean

6.9 -- -- -- -- -- -- -- --

Percent Reduction 0% 65% 34% 45% 50% 86%a 92%b 92%b 94%b a 70 percent concentration reduction objective achieved.

b 90 percent concentration reduction objective achieved.

Notes:

J = estimated value J+ = estimated value, biased high J- = estimated value, biased low U = nondetect; the detection limit was used to calculate the mean

SITE SD031 OES ICER

3-6 SITE SD031 OES ICER

AX1218192002SAC/482366CH

3.3 Continual Improvement Efforts

As described in Section 3.1, performance monitoring results following the 2015 TD implementation indicated that while aquifer conditions had become more reducing within the TD area, a widespread, sustained increase in DOC concentrations above 2015 baseline values was not evident. It appeared that DOC was being consumed at close to the rate at which it was being supplied (CH2M HILL, 2017). Thus, while ERD appeared to be successful at reducing COC concentrations, the DOC initially introduced to the TD area was insufficient to evaluate the effectiveness of the DOC distribution method. Consequently, Contingency 1 from the OES Plan was implemented:

• Contingency 1 – Further actions, such as the installation of additional injection wells to improve the EVO substrate distribution in groundwater, and additional EVO injection(s), will be evaluated.

Performance monitoring results following the TD optimization indicate the performance metric of a 90 percent reduction in the mean 1,1-DCE concentration has been achieved. Periodic remedy performance reviews will also be conducted using monitoring data to validate or update the CSM and exposure assumptions, and evaluate progress toward achieving remedial action objectives (RAOs). The results will be presented in five (5)-year review reports. The first post-Groundwater ROD five (5)-year review occurred in 2018 as scheduled. In addition to the contracted performance monitoring metric, the Site SD031 plume continues to be monitored under the GRIP for achievement of the RAOs identified in the Groundwater ROD (Travis AFB, 2014). Results of the GRIP monitoring and progress toward RAO achievement are reported in the Annual GRISRs.

Because the performance metric of a 90 percent reduction in the mean 1,1-DCE concentration has been achieved, Contingency 2, identified in the OES Plan, is no longer applicable:

• Contingency 2 – Further actions, such as completing a second round of EVO injection with bioaugmentation (or other amendments) to speed 1,1-DCE reductions, will be evaluated.

If evaluation of the monitoring well network shows redundancies in the number of monitoring wells, analytes sampled, or sampling frequencies at Site SD031, then Contingency 3 will be implemented:

• Contingency 3 – Reduce the monitoring network, analyte list, or sampling frequency, as appropriate based on groundwater monitoring results to optimize the number of wells or analytes sampled, as approved by the regulatory agencies.

FIGURE 3-1

2012 BASELINE AND 2019 1,1-DCE

DISTRIBUTION AT SITE SD031

SITE SD031 OPTIMIZED EXIT STRATEGY

IMPLEMENTATION COMPLETION AND

EFFECTIVENESS REPORT

TRAVIS AIR FORCE BASE, CALIFORNIA

LEGEND

? INJECTION WELL INSTALLED IN 2017

? INJECTION WELL INSTALLED IN 2015

! GROUNDWATER MONITORING WELL

_̂ EXTRACTION WELL

") PIEZOMETER

+ GRAVEL CHIMNEY INSTALLED IN 2015

!( MANHOLE

6 APPROXIMATE 1,1-DCE ISOCONCENTRATION

CONTOURS (µg/L)

GROUNDWATER FLOW DIRECTION

CONVEYANCE PIPELINE TO GRAVEL CHIMNEYS

INACTIVE TREATED WATER PIPING

INACTIVE UNTREATED WATER PIPING

A A' CROSS SECTION LINE

ERP SITE BOUNDARY

BASE BOUNDARY

0 200100

FEET ±

\\BROOKSIDEFILES\GIS_SHARE\ENBG\00_PROJ\A\AIRFORCE\TRAVISAFB\MAPFILES\2019\SD031_ICER_REPORT\FIGURE3-1_DCE_SD031_BASELINE.MXD SSCOPES 1/8/2020 10:39:31 AM

KEY MAP

Performance Monitoring Results (2019)

Baseline (2012)

NOTE:

J = REPORTED ANALYTICAL DATA IS ESTIMATED

ND = NOT DETECTED; THE 1,1-DCE METHOD

DETECTION LIMIT FOR NON-DETECTS

IS 0.23 µg/L EXCEPT FOR MW1030X04 WHERE IT IS 0.46 µg/L AND MW206X03 WHERE IT IS 1.2 µg/L

SAMPLE LOCATION -------- MW591X04

1,1-DCE (µg/L) -------------------- 0.21 J

FLAG __________________________|

EW567X31

0.28 J

EW565X31

ND

MW574X31

MW02SX06

MW205X03

ND

MW1725X31

MW752X04

ND

MW134X04

27 J-

MW302X03

MW206X03

ND

MW133X03

37 J-

MW1731X31

ND

MW1730X31

MW1729X31

ND

MW1743X06

ND

MW1030X04

ND

MW1002X04

ND

EW566X31

ND

MW573X31

MW571X31

ND

MW575X31

2.5 J-

MW572X31

36 J-

MW570X31

MW569X31

MW568X31

ND

MW02DX06

ND

IW2331X31

IW2332X31

IW2203X31

3.4 IW2202X31

IW2201X31

9.9

IW2200X31

IW2199X31

IW2198X31

0.23 J

IW2197X31

2.6

MW1741X31

MW1727X31 MW1726X31

IW2775X31

IW2774X31

IW2777X31

IW2776X31

A

A'

6 6

GC2338X31

GC2337X31

GC2336X31

ND

GC2335X31

ND

GC2334X31

IW2198X31

0.23 J

IW2332X31

EW566X31

ND

GC2339X31

DETAIL

MW798X28

ND

EW565X31

0.51

MW134X04

ND

MW1731X31

ND

MW1730X31

ND

MW1729X31

ND

MW574X31

0.9

MW571X31

1.2

EW566X31

EW567X31

34.4 J+

MW575X31

MW573X31

MW570X31

MW569X31

MW02SX06 MW02DX06

MW752X04

MW204X04

MW302X03

MW206X03

MW205X03

MW133X03

MW1742X31

MW1741X31

MW1740X31

MW1727X31 MW1726X31

MW1725X31

MW1743X06

MW1030X04

MW1029X04

MW1002X04

MW572X31

MW568X31

SD031

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800

CLAYEY GRAVEL (GC)

A'

SANDSTONE

SHALE

SOIL AND LITHOLOGY

ELASTIC SILT (MH)

LEAN CLAY (CL)

WELL GRADED SAND (SW)NO SAMPLE/NO RECOVERY FAT CLAY (CH)

SILTSTONE

NOTE: SAMPLES WERE COLLECTED FROM MIDSCREEN

6.7

0.6

3.1

2.1

El ev at io n (fe et m sl

A

ALLUVIUM (NO DATA)

POORLY GRADED SAND (SP)

SILTY SAND (SM)

ESTIMATED BEDROCK SURFACE

C:\USERS\LPRATT.JEG\DESKTOP\GINT_GRISR\2019_GRISR\TRAVIS_2019.GPJ;

Distance (feet)

CLAYEY SAND (SC)

SILT (ML)

WELL GRADED GRAVEL (GW)

FILL/ASPHALT

TOPSOIL/ORGANIC SOIL

POORLY GRADED GRAVEL (GP)

SILTY GRAVEL (GM)

APPROXIMATE 1,1-DCE

ISOCONCENTRATION

CONTOUR (µg/L)

M W

3X

M W

4X

M W

2X

M W

4X

M W

2X

M W

5X

M W

5X

M W

3X

M

W

2X

31EW

5X

EW

6X

M W

X3

M W

X3

G C x3

EW

7X

IW

x3

IW

x3

SCREEN INTERVAL

APPROXIMATE 2Q19

GROUNDWATER ELEVATION (ft MSL) 1,1-DCE CONCENTRATION (µg/L) DETECTED

IN 2019

CIS-1,2-DCE CONCENTRATION (µg/L) DETECTED

IN 2019

VINYL CHLORIDE CONCENTRATION (µg/L) DETECTED IN 2019 TOTAL ORGANIC CARBON CONCENTRATION (mg/L)

DETECTED IN 2019

ND NOT DETECTED

NA NOT ANALYZED

SCALE EXAGGERATION - 14:1 (H:V)

NOTE: SEE FIGURE 3-1 FOR CROSS SECTION LINE

FIGURE 3-2

SITE SD031 GEOLOGIC

CROSS SECTION A - A'

SITE SD031 OPTIMIZED EXIT STRATEGY

IMPLEMENTATION COMPLETION AND

EFFECTIVENESS REPORT

TRAVIS AIR FORCE BASE, CALIFORNIA

ND

0.3 J-

NA

37 J-

ND

ND

NA

27 J-

20 J-

0.68 J-

2.8

36 J-

8.2

0.7 J

ND

ND

NA

2.5 J-

ND

ND

NA

ND

ND

ND

ND

NA

ND

ND

1.2

ND

ND

ND

ND

9.4

1.2 J

ND

0.23 J

5.8 1.3

9.9

0.28 J

ND

2.9

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

De c-

Ju n-

De c-

Ju n-

De c-

Ju n-

De c-

Ju n-

De c-

Ju n-

De c-

Ju n-

De c-

Ju n-

191, 1-

DC

E Co nc en tr a� on R ed uc �o n (P er ce nt ag e)

Date

Status Quo Poten�al Process Improvement Range Ideal Range Observed Data

2015 TD Startup 2017 TD Op�miza�on

*TD Startup completed October 2014 - April 2015. TD Op�miza�on completed April - December 2017.

FIGURE 3-3

SITE SD031 UPDATED PERFORMANCE MODEL

SITE SD031 OPTIMIZED EXIT STRATEGY IMPLEMENTATION

COMPLETION AND EFFECTIVENESS REPORT

TRAVIS AIR FORCE BASE, CALIFORNIA

ES010214014200SAC

SITE SD031 OES ICER 4-1

SECTION 4

Discussion of Performance and Effectiveness

As the data presented in Section 3.2 indicate, the Site SD031 TD was successfully installed in 2015 and further optimized in 2017. 1,1-DCE concentrations in the target treatment area have significantly declined as a result of these actions. Performance monitoring data demonstrate that the mean concentration of 1,1-DCE was reduced by greater than the 70 percent objective in April 2016 (86 percent), and following optimization of the TD, by 92 percent in 2017 and 2018, and 94 percent in 2019 to achieve the 90 percent concentration reduction objective.

The OES performance objective is complete for Site SD031. Implementation and optimization of the TD have reduced 1,1-DCE concentrations by 94 percent, which exceeds both the 70 percent by 2019 and 90 percent by the end of the POP of the PBC performance objectives. Consequently, the effectiveness of the OES has exceeded the performance objective.

Optimization evaluations will continue to be conducted at appropriate intervals to reduce groundwater monitoring costs, and monitoring wells no longer needed for the GRIP will be decommissioned. In order to achieve SC in accordance with the Air Force’s definition at Site SD031, land use controls (LUCs) must be removed, which would require achieving cleanup levels for all COCs and the subsequent decommissioning of all remaining extraction wells, injection wells, monitoring wells, gravel chimneys, and groundwater pipelines after regulatory site closure.

Appendix A Acronyms and Abbreviations

SITE SD031 OES ICER A-1

APPENDIX A

Acronyms and Abbreviations µg/L microgram(s) per liter

4Q fourth quarter

AFB Air Force Base

AFCEC Air Force Civil Engineer Center

Air Force U.S. Air Force amsl above mean sea level bgs below ground surface

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

COC chemical of concern

CSM conceptual site model

DCA dichloroethane

DCE dichloroethene

DOC dissolved organic carbon

DTSC California Department of Toxic Substances Control

EIOU East Industrial Operable Unit

EISB enhanced in situ bioremediation

EPA U.S. Environmental Protection Agency

ERD enhanced reductive dichlorination

EVO emulsified vegetable oil

FS feasibility study

GRIP Groundwater Remediation Implementation Program

GRISR Groundwater Remediation Implementation Status Report

HVAC heating, ventilation, and air conditioning

ICER Implementation Completion and Effectiveness Report

J estimated value (data flag)

J- estimated value, biased low (data flag)

J+ estimated value, biased high (data flag)

LUC land use control

MNA monitored natural attenuation

NEWIOU North, East, and West Industrial Operable Unit

APPENDIX A: ACRONYMS AND ABBREVIATIONS

A-2 SITE SD031 OES ICER

AX1218192002SAC/482366CH

NFA no further action

NGWTP North Groundwater Treatment Plant

OES optimized exit strategy

OWS oil/water separator

PBC performance-based contract

POP period of performance

RAO remedial action objective

RC response complete

RI remedial investigation

RIP remedy in place

ROD Record of Decision

SC site closeout

TCE trichloroethene

TD technology demonstration

TDCCR Technology Demonstration Construction Completion Report

TM technical memorandum

U nondetect (data flag)

USACE U.S. Army Corps of Engineers

Water Board San Francisco Bay Regional Water Quality Control Board

Weston Roy F. Weston, Inc.

Appendix B References

SITE SD031 OES ICER B-1

APPENDIX B

References

Air Force Civil Engineer Center (AFCEC). 2014. Optimized Exit Strategy Compendium for Performance-Based Remediation. Version 1.0. October.

CH2M HILL. 2019. Site SD031 Soil Remedial Investigation/Feasibility Study. Prepared for Travis Air Force Base, California. Draft. September.

CH2M HILL. 2018a. Optimized Exit Strategy Performance Plan for Sites SD031 and SD034. Prepared for Travis Air Force Base, California. Final. December.

CH2M HILL. 2018b. Emulsified Vegetable Oil Sites FT004, SS015, SD031, and SD036 Injections Technical Memorandum. Prepared for Travis Air Force Base, California. Final. November.

CH2M HILL. 2017. 2016 Annual Groundwater Remediation Implementation Status Report. Prepared for Travis Air Force Base, California. Final. December.

CH2M HILL. 2016. Site SD031 Soil Remedial Investigation Work Plan. Prepared for Travis Air Force Base, California. Final. July.

CH2M HILL. 2015. Site SD031 Technology Demonstration Construction Completion Report. Prepared for Travis Air Force Base, California. Final. August.

CH2M HILL. 2014. Site SD031 Technology Demonstration Work Plan. Prepared for Travis Air Force Base, California. Final. November.

Travis Air Force Base. 2014. Groundwater Record of Decision. Final. June.

Travis Air Force Base. 2006. North/East/West Industrial Operable Unit Soil, Sediment, and Surface Water Record of Decision. Final. May.

Weston, Roy F., Inc. (Weston). 1995. East Industrial Operable Unit (EIOU) Remedial Investigation Report.

Prepared for Travis Air Force Base, California. Final. October.