9 Final_Site_LF007_OES_ICR_20Dec2016_DK01Submittal.pdf

TRAVIS AIR FORCE BASE, CALIFORNIA

PERFORMANCE-BASED CONTRACT

Final

Site LF007 Optimized Exit Strategy Implementation Completion 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:

December 2016

F i n a l

Site LF007 Optimized Exit Strategy Implementation Completion Report

Travis Air Force Base, California

Prepared for

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

Air Force Civil Engineer Center

December 2016

2485 Natomas Park Drive Suite 600

Sacramento, CA 95833

SITE LF007 OES ICR i

EN1027161135SAC/482366

Contents

Section Page

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

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

1.2 Performance and Technical Objectives ...........................................................................1-1

1.3 Optimized Exit Strategy Implementation Report Guidance ............................................1-2

2 Overview of Remedial Progress and Status ..........................................................................2-1

2.1 Overview of Site Advancement .......................................................................................2-1

2.2 Performance Model Update ............................................................................................2-2

2.3 Continual Improvement Efforts .......................................................................................2-4

3 Discussion of Performance ..................................................................................................3-1

Tables

2-1 Site LF007 TCE Concentration Changes Since 2012 Baseline........................................................2-2 2-2 Site LF007 Changes in Groundwater Monitoring Requirements Since 2012 Baseline .................2-4

Figures

1-1 Site LF007 Map

2-1 Reduction of TCE Concentrations Detected at the Site LF007 Treatment Area from 2012 to 2016 2-2 Site LF007 Updated Performance Model

Appendixes

A Acronyms and Abbreviations B References

SITE LF007 OES ICR 1-1

SECTION 1

Introduction

This Site LF007 Optimized Exit Strategy (OES) Implementation Completion Report (ICR) documents implementation of the contracted Site LF007 optimized remedy presented in the OES Performance Plan Sites LF007, LF008, SS014, SS015, SS016, ST018, ST027, SS029, SD033, SD036, SD037, DP039, and LF044 (OES Plan) (CH2M HILL, 2014). The OES Plan describes the optimization activities that will occur at each of these sites under the Performance-based Contract (PBC) W912QR-12-D-0005, Task Order DK01 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 LF007 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 LF007.

1.1 Site Background

Site LF007 is former trench-and-cover Landfill 2 and is located in the northern portion of Travis Air Force Base (AFB), California (Figure 1-1). Site LF007 is divided into several subareas, including Subareas LF007B, LF007C, LF007D, LF007E, and LF007G, as shown on Figure 1-1. Groundwater and soil contamination are present at Site LF007. Because of the presence of the landfill and a Corrective Action Management Unit (CAMU) that was constructed over the landfill cover, soil remediation is not being pursued at this time, because it is not the best value for the U.S. Air Force (Air Force). Therefore, the Site LF007 OES primarily addresses groundwater contamination at the site, which has been identified at Subareas LF007B, LF007C (the only subarea where the groundwater is actively being treated), and LF007D. Groundwater chemicals of concern (COCs) have not been detected in Subarea LF007B for several years. The primary groundwater COC at Subarea LF007C is trichloroethene (TCE). The primary groundwater COCs at Subarea LF007D are 1,4-dichlorobenzene (DCB) and benzene.

1.2 Performance and Technical Objectives

The PBC-awarded performance objective for Site LF007 is to implement an OES. The following PBC and post-PBC technical objectives will be achieved to advance the site toward SC:

• Obtain capture of the off-base portion of the TCE plume through optimization of the Site LF007 groundwater extraction and treatment (GET) system (PBC objective).

• Maintain higher pumping rates in focused plume areas to decrease off-base TCE levels and to reduce the active pumping period (PBC objective).

• Demonstrate that continued groundwater monitoring at Subarea LF007B is not necessary because COC concentrations are measured at levels below maximum contaminant levels (MCLs) (PBC objective).

• Strive to achieve a 40 percent reduction in groundwater monitoring requirements by 2018 (PBC objective).

• Strive to achieve a 60 percent reduction in the mean TCE concentration by the end of the period of performance (POP) of the PBC (PBC objective). Achievement of this objective will be measured

SECTION 1: INTRODUCTION

1-2 SITE LF007 OES ICR

EN1027161135SAC/482366

relative to the 2012 TCE concentrations at wells MW125x07, MW617x07, MW620x07, and MW2007x07 (see Section 2.2).

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

• Achieve regulatory and 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 after regulatory site closure to achieve the Air Force definition of SC (post-PBC objective).

1.3 Optimized Exit Strategy Implementation Report

Guidance

This OES ICR was prepared in accordance with the relevant components of the OES 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

HA

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VANDENBERG DR

VANDENBERG CT

VANDENBERG DR

COLLINS DR

COLLINS DR

COLLINS DR

NAPA ST

PERIMETER ROAD

COLLINS DR

MWGX07

MWFX07

MWDX07

MWCX07

MWBX07

MWAX07

MW619X07

MW620X07

MW2172X07

MW1731X31

MW1730X31

MW1729X31

MW618X07

MW617X07

MW616X07

MW613X07

MW612X07

MW602X07

MW601X07

MW600X07

MW303X07

MW284X07

MW261X07

MW201X07

MW129X07

MW128X07

MW126X07

MW125X07

EW615X07

EW614X07

MW258DX06

MW208DX06

MW1743X06

MW259X06

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MW01SX06

MW01DX06

MW264X04

MW2173X07

MW2007X07

MW2163X07

MW2170X07

MW2171X07

MW2169X07

APPROXIMATE

CAMU PROJECT

BOUNDARY

MNA AREA

MNA AREA

GET AREA

LF007C GWTP

LF007ELF007G

New Untreated Groundwater Pipeline

Treated and untreated groundwater lines to and from the NGWTP are no longer in use as of Novemeber 2013

To NGWTP

LF007

LF007B

LF007D

LF007

LF006

FT004

LF007C

1219 FIGURE 1-1

SITE LF007 MAP

SITE LF007 OPTIMIZED EXIT STRATEGY

IMPLEMENTATION COMPLETION REPORT

TRAVIS AIR FORCE BASE, CALIFORNIA

LEGEND

! MONITORING WELL

_̂ EXTRACTION WELL

UNTREATED WATER PIPING

TREATED WATER PIPING

INACTIVE UNTREATED WATER PIPING

INACTIVE TREATED WATER PIPING

FENCE

CAMU BOUNDARY

APPROXIMATE GROUNDWATER

FLOW DIRECTION

MAIN WATERLINE

SURFACE WATER

WETLAND FEATURES

SEASONAL WETLAND

VERNAL POOL

WETLAND SWALE

ERP SITE BOUNDARY

LF007 SUBAREA

BASE BOUNDARY

0 300150

FEET ±

\\BALDUR\PROJ\TRAVIS_AFB\MAPFILES\2016\OESICREPORT_2016\FIG1-1_LF007LOCATIONMAP.MXD SSCOPES 11/14/2016 3:43:31 PM

KEY MAP

SITE LF007 OES ICR 2-1

SECTION 2

Overview of Remedial Progress and Status

This section summarizes the remedial progress made to date under the PBC at Site LF007 and the current site status.

2.1 Overview of Site Advancement

The primary objective of the OES activities during the PBC is to reduce the TCE concentration in the Subarea LF007C plume that extends north across the Base boundary, as monitored by the performance monitoring wells listed in Section 1.2. The secondary objective during the PBC is to gradually scale back the existing GET and monitored natural attenuation (MNA) remedy to reduce the long-term cost, as appropriate, as risk associated with Site LF007 is sufficiently reduced. It was determined that the best value for the Air Force during the PBC is to treat the area shown on Figure 2-1, where the plume extends off-base, and to continue MNA at on-base locations where COCs remain elevated above MCLs.

As proposed, Subarea LF007B has been eliminated from GRIP events under the PBC because measured concentrations of groundwater COCs at the site have not been detected above cleanup levels since 1994.

Operation of the GET system will be phased out once COC concentrations at off-base monitoring locations are reduced to MCLs and plume stability is established, evidence of which will be presented in future performance monitoring reports. Over time, the groundwater plume will draw back toward the Base boundary, and the need for GET system operation will be phased out. The remedy will then move toward MNA with land use controls (LUCs) when it is demonstrated that the GET system is no longer needed to contain the plume within the Base boundary. MNA with LUCs will be the follow-on remedy that will be implemented until on-base MCLs are reached and SC is achieved.

To achieve the primary objective of providing hydraulic capture of the Site LF007 TCE plume that extends off-base, optimization of the existing GET system at Site LF007 was performed between November 2013 and January 2014. Optimization activities were performed in accordance with the Subarea LF007C and Site SS030 Remedial Process Optimization Work Plan (CH2M HILL, 2013) and are documented in the 2014 Annual Groundwater Remediation Implementation Status Report (GRISR) (CH2M HILL, 2016). Optimization activities included (1) installation of an upgraded extraction pump, solar panel, and battery system at extraction well EW614x07 to increase the extraction well pumping rate; (2) installation of new well head instrumentation at EW614x07 and EW615x07; (3) construction of the LF007C Groundwater Treatment Plant (LF007C GWTP), which is designed to more efficiently treat the volume of water extracted at Subarea LF007C; and (4) construction of a new, more direct, pipeline that bypasses the North Groundwater Treatment Plant (NGWTP) and cuts the extracted groundwater traveling distance by approximately 2,645 feet. These optimization activities have resulted in an approximately 2.5 times increase in the volume of groundwater extracted and treated. Further optimization of extraction well EW615x07 was performed in June 2016. During the June 2016 optimization, the solar panel, extraction pump, and pump controller at extraction well EW615x07 were upgraded to increase pumping rates from that well. Since coming online on June 27, 2016, EW615x07 has pumped approximately 95,000 gallons (through September 2016) and has achieved a nearly 12-fold increase in the extraction rate since the LF007C GWTP first came online in January 2014. The June 2016 optimization of EW615x07 is documented in the June 2016 Subarea LF007C Groundwater Treatment Plant Monthly Data Sheet. The optimized remedy also includes the potential installation of an additional extraction well on-base if increased pumping rates achieved by the optimized GET system do not achieve the Site LF007 performance monitoring metrics described in Section 2.2. Based on the improvement in

SECTION 2: OVERVIEW OF REMEDIAL PROGRESS AND STATUS

2-2 SITE LF007 OES ICR

EN1027161135SAC/482366

GET system capture and reduction in TCE concentrations between 2012 and 2016 illustrated on Figure 2-2, and progress toward achieving performance monitoring metrics discussed in Section 2.2, installation of an additional extraction well will likely not be necessary to meet the performance objectives.

Subarea LF007C and Site SS030 Remedial Process Optimization Work Plan (CH2M HILL, 2013) provided a detailed conceptual site model (CSM), outlined the pre-design investigation activities, and presented the optimized remedial design, which was consistent with both the optimized remedy presented for Site LF007 in the OES Plan and the remedy selected in the Groundwater Record of Decision (ROD) (Travis AFB, 2014).

The selected final groundwater remedy for Site LF007 is GET (Subarea LF007C) combined with MNA (Subareas LF007B and LF007D).

2.2 Performance Model Update

The performance model for the Site LF007 remedial optimization was presented in the OES Plan.

Performance monitoring of the optimized remedy is executed under the GRIP. The most recent GRIP sampling event was conducted in the second quarter 2016 (2Q16). Data collected through 2Q16 were used to update the performance model discussed in this section.

The following performance monitoring metrics are used to assess progress toward achieving performance objectives:

• Objective 1: The mean concentration of TCE in the GET area should be reduced by 30 percent by 2017 and by 60 percent by the end of the POP of the PBC (PBC metrics). Concentration reduction goals are monitored relative to four (4) consistent performance monitoring wells, as specified in the OES Plan: MW125x07, MW617x07, MW620x07, and MW2007x07.

• Objective 2: Groundwater monitoring requirements for Site LF007 should be reduced by 40 percent by 2018.

Achievement of Objective 1, concentration reduction metrics, is determined by calculating the sum of TCE concentrations from these performance monitoring wells to determine the mean concentration reduction from the wells as a whole. Concentration reductions are evaluated against the 2012 baseline TCE concentrations. The individual and mean TCE concentrations for these four (4) wells through 2Q16 are provided in Table 2-1. The OES requirement during the PBC of a 60 percent mean concentration reduction will be considered fulfilled once the mean TCE concentration in the wells listed in Table 2-1 reaches 7.62 micrograms per liter (µg/L) or less.

TABLE 2-1

Site LF007 TCE Concentration Changes Since 2012 Baseline Site LF007 Optimized Exit Strategy Implementation Completion Report, Travis Air Force Base, California

Well Name

2012 TCE

(µg/L)

2013 TCE

(µg/L)

2013-2014 GET

Optimization

2014 TCE

(µg/L)

2015 TCE

(µg/L)

2016 TCE

(µg/L)

MW125x07 22.7 24.6 11.9 7.7 2.3

MW617x07 8.6 9.6 7.8 9.1 9.2

MW620x07 5 5.2 1.7 17 8.1

MW2007x07 39.9 22.1 25.9 24 25

Mean 19.05 (Baseline)

15.38 11.83 14.45 11.15

Percent Reduction 0% 19% 38% 24% 41%

SITE LF007 OES ICR 2-3

EN1027161135SAC/482366

Figure 2-1 presents the most recent TCE distribution (2Q16) for Site LF007 and provides a comparison to the 2012 baseline TCE distribution (prior to the 2013–2014 GET system optimization activities). Figure 2-1 shows the improvement in the extent of hydraulic capture achieved by the optimized GET system and the resulting decrease in TCE concentrations within the plume, as well as the reduction in the plume extent.

The performance monitoring metric of a 30 percent TCE concentration reduction, targeted for 2017, was exceeded in 2016 (a 41 percent TCE concentration reduction was achieved in 2016). If the optimization continues to perform as expected, the performance monitoring metrics of a 60 percent TCE concentration reduction by the end of the POP of the PBC will be met.

The updated performance model illustrating the observed changes in the mean TCE concentrations compared to expected trends in concentration reductions is presented on Figure 2-2. As indicated on Figure 2-2, the 2016 mean TCE concentration reduction of 41 percent is within the expected range to be on track to achieve the PBC contract requirements.

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 the optimized GET system is performing as expected. This portion of the graph is created by considering the remedial design, site-specific CSM, and CH2M HILL experience at this and similar GET sites.

• 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 trends under pre-OES treatment conditions (e.g., status quo condition based on the pre-optimization rate of concentration decline).

Achievement of Objective 2, reduction in groundwater monitoring requirements, is determined by comparison of the number of wells sampled in the baseline year (2012) compared to the current year (2016). The changes in groundwater monitoring requirements from the baseline year (2012) to the current year (2016) are summarized in Table 2-2. Groundwater monitoring requirements in 2016 have been reduced from baseline requirements by 35 percent. This reduction was achieved through a combination of decreasing the number of wells sampled at the site and decreasing sampling frequencies.

Since 2012, wells MW129x07, MW613x07, MW616x07, MW619x07, and MW2173x07 were removed from routine sampling. Over the same time period, sampling frequencies at wells MW261x07, MW2163x07, MW2169x07, MW2170x07, and MW2171x07 were reduced from semiannual to annual. Over this time period, one well, MW128x07, was added to the routine monitoring network. Well MW128x07 is closer to the source area than MW129x07; consequently, the monitoring network was revised to include MW128x07 and exclude MW129x07. Routine monitoring of Subarea LF007B has been discontinued, as proposed. Additional reductions (from 35 percent in 2016 to 40 percent by 2018) are achievable, based on the observed contraction of the Site LF007 TCE plume. Achieving the reduction goal would require eliminating one (1) more well from the Site LF007 monitoring network. If the Site LF007 TCE plume continues to contract at the current pace, one (1) or more of these wells may no longer be needed for

2-4 SITE LF007 OES ICR

EN1027161135SAC/482366

routine monitoring of the plume: MW601x07, MW125x07, MW2169x07, and MW2172x07. It is anticipated that at least one (1) of these wells will be eliminated from routine monitoring by 2018.

TABLE 2-2

Site LF007 Changes in Groundwater Monitoring Requirements Since 2012 Baseline Site LF007 Optimized Exit Strategy Implementation Completion Report, Travis Air Force Base, California

2012 2013 2014 2015 2016

Number of Wells Sampled 26 25 20 20 17

Percent Reduction 0% 4% 23% 23% 35%

2.3 Continual Improvement Efforts

As described in Section 2.2, the remedial optimization is performing as designed, and contracted performance metrics are being met. Consequently, no modifications to the remedy optimization are planned at this time, and no contingency actions (discussed below) have been triggered. However, periodic remedy performance reviews will 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 is scheduled for 2018.

If annual groundwater monitoring results demonstrate that the Subarea LF007C plume expands rather than contracts after the completion of the optimized GET system, indicating that it is inadequate to remediate the plume, then Contingency 1 will be implemented:

• Contingency 1 – Implement further actions such as the installation of one (1) or more additional extraction wells within the portion of the plume with the highest TCE concentrations, or as necessary to achieve plume capture.

If annual groundwater monitoring results presented in annual GRISR reports indicate that the mean TCE reduction is less than 30 percent in 2017, then Contingency 2 will be implemented:

• Contingency 2 – Evaluate further actions such as the injection of emulsified vegetable oil (EVO) to treat the portions of the plume with the highest residual TCE concentrations.

If evaluation of the monitoring well network shows redundancies in the number of monitoring wells, analytes sampled, or sampling frequencies, 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.

Data collected through 2Q16 indicate that the remedial optimization is performing as designed and no contingency actions have been triggered.

LEGEND

! GROUNDWATER MONITORING WELL

_̂ EXTRACTION WELL

FENCE

APPROXIMATE GROUNDWATER

FLOW DIRECTION

APPROXIMATE EXTENT OF CAPTURE

UNTREATED WATER PIPING

TREATED WATER PIPING

INACTIVE UNTREATED WATER PIPING

INACTIVE TREATED WATER PIPING

5 APPROXIMATE TCE

ISOCONCENTRATION CONTOUR (µg/L)

TCE>5 µg/L

BUILDINGS

UNPAVED AREA

PAVED AREA

ROAD

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KEY MAP

FIGURE 2-1

REDUCTION OF TCE CONCENTRATIONS

DETECTED AT THE SITE LF007 TREATMENT

AREA FROM 2012 TO 2016

SITE LF007 OPTIMIZED EXIT STRATEGY

IMPLEMENTATION COMPLETION REPORT

TRAVIS AIR FORCE BASE, CALIFORNIA

MW591X04

0.21J

SAMPLE LOCATION

TCE (µg/L)

FLAG

Baseline for GET Optimization (2012)

MWFX07

MWDX07

MWAX07

MW618X07 MW600X07

MW303X07

MW284X07

MW201X07

MW128X07

MW126X07

MWCX07

ND

MWBX07

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MW2173X07

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MW2172X07

0.48 J

MW619X07

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MW616X07

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MW613X07

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MW612X07

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MW601X07

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MW261X07

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MW129X07

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EW615X07

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MW264X04

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MW617X07

8.6

MW202X04

15.6 J+

MW2007X07

39.9

MW620X07

5MW2170X07

ND

MW2163X07

ND

EW614X07

4.5

MW2171X07

1.2

MW125X07

22.7 J+

MW2169X07

ND

MWCX07

ND

MWBX07

ND

MW620X07

8.1

MW612X07

ND

MW601X07

ND

MW261X07

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MW201X07

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EW615X07

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MW2007x07

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MW2170X07

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NDMW2163X07

ND

MW617X07

9.2

MW125X07

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MW2171X07

0.68J

EW614X07

0.93J

Performance Monitoring Results (2Q16)

EN0817161114SAC LF007_Figure_2-2_V2.ai 11.11.16 tdaus

FIGURE 2-2

Site LF007 Updated Performance Model Site LF007 Optimized Exit Strategy Implementation Completion Report Travis Air Force Base, California

0%

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(P er ce nt ag e)

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Figure 2-5 Subarea LF007C Expected PBC Benefit versus Status Quo

Contingency Range Potential Process Improvement Range Ideal Range Observed Data

GET System Optimized

SITE LF007 OES ICR 3-1

SECTION 3

Discussion of Performance

As the data presented in Section 2.2 indicate, the Site LF007 optimized remedy was successfully implemented and, to date, is performing as designed. Following the 2013–2014 GET system optimization, TCE concentrations have declined significantly (42 percent mean reduction by 2Q16) and were within the expected range to achieve contractual requirements. If TCE concentrations continue to decline as expected, the performance monitoring metrics of a 30 percent TCE concentration reduction by 2017 and a 60 percent TCE concentration reduction by the end of the POP of the PBC will be met.

Appendix A Acronyms and Abbreviations

SITE LF007 OES ICR A-1

APPENDIX A

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

2Q16 second quarter 2016

AFB Air Force Base

AFCEC Air Force Civil Engineer Center

Air Force U.S. Air Force

CAMU Corrective Action Management Unit

COC chemical of concern

CSM conceptual site model

DCB dichlorobenzene

EVO emulsified vegetable oil

GET groundwater extraction and treatment

GRIP Groundwater Remediation Implementation Program

GRISR Groundwater Remediation Implementation Status Report

ICR Implementation Completion Report

LF007C GWTP LF007C Groundwater Treatment Plant

LUC land use control

MCL maximum contaminant level

MNA monitored natural attenuation

NGWTP North Groundwater Treatment Plant

OES optimized exit strategy

PBC performance-based contract

POP period of performance

RAO remedial action objective

RC response complete

ROD Record of Decision

SC site closeout

TCE trichloroethene

Appendix B References

SITE LF007 OES ICR 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. 2016. 2014 Annual Groundwater Remediation Implementation Status Report. Prepared for Travis Air Force Base, California. Final. March.

CH2M HILL. 2014. Optimized Exit Strategy Performance Plan Sites LF007, LF008, SS014, SS015, SS016, ST018, ST027, SS029, SD033, SD036, SD037, DP039, and LF044. Prepared for Travis Air Force Base, California. Final. March.

CH2M HILL. 2013. Subarea LF007C and Site SS030 Remedial Process Optimization Work Plan. Prepared for Travis Air Force Base, California. Final. November.

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