table of contents - azdeq.govstatic.azdeq.gov/wqarf/wcp_prap.pdftable of contents 1.0 introduction...

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Table of Contents

1.0 INTRODUCTION .................................................................................................................................... 1

1.1 PURPOSE OF DOCUMENT ................................................................................................................. 1

1.2 SITE DESCRIPTION ............................................................................................................................ 2

2.0 SITE CHARACTERISTICS ....................................................................................................................... 4

2.1 NATURE AND EXTENT OF CONTAMINATION .................................................................................. 4

2.1.1 Source of Releases ...................................................................................................................... 4

2.1.2 Soil/Soil Vapor ............................................................................................................................. 4

2.2.3 Groundwater .............................................................................................................................. 6

2.2.4 Surface Water ............................................................................................................................ 7

3.0 NEED FOR REMEDIAL ACTION ............................................................................................................ 8

3.1. SOIL/SOIL VAPOR ............................................................................................................................. 8

3.2 GROUNDWATER ............................................................................................................................... 9

3.3 SURFACE WATER .............................................................................................................................. 9

4.0 REMEDIAL OBJECTIVES ..................................................................................................................... 10

4.1 REMEDIAL OBJECTIVES FOR LAND ............................................................................................... 10

4.2 REMEDIAL OBJECTIVES FOR GROUNDWATER ............................................................................ 10

4.3 REMEDIAL OBJECTIVES FOR SURFACE WATER ........................................................................... 10

4.4 REMEDIATION LEVELS AND BASIS FOR SELECTION ................................................................... 11

5.0 EVALUATION OF REMEDIAL ALTERNATIVES ................................................................................... 12

5.1 PROPOPSED REMEDY ..................................................................................................................... 12

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5.2 RATIONALE FOR SELECTION OF REFERENCE REMEDY ............................................................... 17

5.3 PERFORMANCE MONITORING RECOMMENDATIONS ................................................................ 18

5.4 ACHIEVEMENT OF REMEDIAL OBJECTIVES .................................................................................. 21

5.5 ACHIEVEMENT OF REMEDIAL ACTION CRITERIA ......................................................................... 22

5.6 CONSISTENCY WITH WATER MANAGEMENT PLANS .................................................................. 23

5.7 CONSISTENCY WITH GENERAL LAND USE PLANNING ................................................................ 23

5.8 SUMMARY OF COSTS TO IMPLEMENT THE PROPOSED REMEDY .............................................. 23

5.9 LEAD AGENCY STATEMENT FOR PROPOSED REMEDY ............................................................... 24

5.10 CONTINGENCY FOR PROPOSED REMEDY ................................................................................... 24

6.0 COMMUNITY INVOLVEMENT............................................................................................................ 25

6.1 PUBLIC COMMENT PERIOD OF PRAP............................................................................................ 25

6.2 PUBLIC MEETINGS .......................................................................................................................... 25

6.3 ADMINISTRATIVE RECORD ............................................................................................................ 25

6.4 OTHER CONTACT INFORMATION ................................................................................................. 25

7.0 REFERENCES ...................................................................................................................................... 26

TABLES Table 4-1 Relevant Soil and Groundwater Standards for Primary Contaminants of Concern Table 5-1 Existing Wells Which May be Sampled to Evaluate ERD Performance and for Periodic

Sampling

FIGURES Figure 1-1 Site Location Map Figure 1-2 Site Boundary Figure 2-1 Upper MAU PCE Plume (March 2014)

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Figure 2-2 Upper MAU TCE Plume (March 2014) Figure 2-3 Upper MAU 1,1-DCE Plume (March 2014) Figure 2-4 Middle MAU PCE Plume (March 2014) Figure 5-1 SVE Well Locations Figure 5-2 Reference Remedy: Soil Vapor Extraction, Enhance Reductive Dechlorination, and

Monitored Natural Attenuation APPENDICES Appendix A. Detailed Costs to Implement the Proposed Remedy

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ACRONYMS § Section A.A.C. Arizona Administrative Code ADEQ Arizona Department of Environmental Quality AWQS Aquifer Water Quality Standard A.R.S. Arizona Revised Statute BGS Below Ground Surface COC Contaminants of Concern DCA Dichloroethane 1,1-DCE 1,1-Dichloroethene Cis-1,2-DCE cis-1,2-dichloroethene DNAPL Dense Non-Aqueous Phase Liquid EOS Edible Oil Substrate ERA Early Response Action ERD Enhanced Reductive Dechlorination F&B F&B Manufacturing Company FS Feasibility Study GPL Groundwater Protection Level GSC Glenrosa Service Center Hill Brothers Hill Brothers Chemical Company MAU Middle Alluvial Unit MEK Methyl Ethyl Ketone μg/L micrograms per liter mg/kg milligrams per kilogram MNA Monitored Natural Attenuation PCE Tetrachloroethene PRAP Proposed Remedial Action Plan Pyramid Pyramid Industries, Inc. RI Remedial Investigation Rinchem The Rinchem Company RO Remedial Objective(s) ROD Record of Decision SRL Soil Remediation Levels SVE Soil Vapor Extraction Tarr Tarr Acquisitions, LLC TCA 1,1,1-trichloroethane TCE Trichloroethene VOC Volatile Organic Compounds WCP NP West Central Phoenix North Plume WQARF Water Quality Assurance Revolving Fund

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1.0 INTRODUCTION

1.1 PURPOSE OF DOCUMENT

The Arizona Department of Environmental Quality (ADEQ) has completed a Feasibility Study (FS) for the West Central Phoenix North Plume (WCP NP) Water Quality Assurance Revolving Fund (WQARF) Site (the Site). The next step in the restoration process required under Arizona Revised Statute (A.R.S.) Section (§) 49-287.04 is to issue a proposed remedial action plan (PRAP) describing the proposed Site remedy to the public for review and comment. The Matrix-CALIBRE Team has been retained by ADEQ to prepare this PRAP for the Site which is located in Phoenix, Arizona (see Figure 1-1). This PRAP was prepared in accordance with Arizona Administrative Code (A.A.C.) R18-16-408 and is based on information contained in the following documents:

• Final Remedial Investigation Report, West Central Phoenix North Plume, Phoenix, Arizona (LFR, 2009) (RI)

• Final Feasibility Study, West Central Phoenix North Plume, Phoenix, Arizona (Matrix-CALIBRE, 2016)

The information contained in the PRAP is drawn from and, in many cases, quotes directly from the above-referenced reports without attribution other than that noted here. The detailed history of environmental investigations, early response actions (ERAs), and preliminary screening of remedial alternatives completed for the Site are presented in the referenced documents and are not reiterated in detail here. The latest Site-related information, documents and notices can be found in electronic format at: http://www.azdeq.gov/node/1062.

The purpose of the PRAP is to describe:

1. The boundaries of the site or portion of the site that is subject to the remedial action. 2. The results of the RI and FS. 3. The proposed remedy and its estimated costs. 4. How the remediation goals and selection factors and rules have been considered.

The PRAP is part of the final remedy selection process under WQARF where public input is solicited on the proposed remedy and on the rationale/basis used for the remedy selection. New information that ADEQ receives during the public comment period will be incorporated in the selection of a final remedy and the final remedy could differ from the proposed remedy

http://www.azdeq.gov/node/1062

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presented in this document. Information on public participation activities associated with this PRAP is provided in Section 6.0.

ADEQ will review the public comments and prepare a responsiveness summary to address the public comments. The responsiveness summary will be part of the Record of Decision (ROD). In the ROD, ADEQ will finalize and document its decision regarding the remedy for the Site.

1.2 SITE DESCRIPTION

The Site is located in an industrialized area of west central Phoenix (Figure 1-1). It is approximately bounded by West Highland Avenue to the north, Indian School Road to the south, 37th Avenue to the east, and 43rd Avenue to the west, covering an area of approximately 280 acres (Figure 1-2). Releases of volatile organic compounds (VOCs) are known to have occurred at four primary locations/facilities at the Site as follows:

1. F&B Manufacturing Company (F&B) is an aircraft and spacecraft parts manufacturing facility that used tetrachloroethene (PCE) in a vapor degreaser from approximately 1967 to 1987, after which time 1,1,1-trichloroethane (TCA) was used.

2. Pyramid Industries, Inc. (Pyramid) operated an electrical components manufacturing facility from 1977 to 1994. The facility used various chemicals including acids, caustics, heavy metals, paints, and methylene chloride. The 2009 RI notes that PCE use at this facility has not been documented. However, elevated concentrations of PCE have been detected in soil in the southwestern portion of the facility.

3. The Rinchem Company (Rinchem) operated a chemical warehouse and distribution facility from 1982 to 1993. The facility handled solvents, oils, and fuels including blended custom solvents. Chemicals were stored in a tank farm located on the western side of the property. A repackaging area and chemical processing area were located immediately adjacent to the tank farm. PCE use was documented at this facility. Tarr Acquisition, LLC (Tarr) took over operations in June 1993 as a chemical distributor, conducting the same types of operations as Rinchem, including handling of PCE and trichloroethene (TCE). Tarr reportedly constructed a new bulk chemical storage tank farm and did not use the former Rinchem tank farm. Tarr reportedly discontinued sales of PCE and TCE in the summer of 2015 (HGL, 2016).

4. Hill Brothers Chemical Company (Hill Brothers) operates a chemical repackaging and distribution facility. The business started operations at this location in 1969 and remains in operation today. Bulk chemicals are received via railroad cars and tanker trucks and stored in aboveground storage tanks prior to transfer into containers for distribution. Chemicals handled at the facility have included solvents (acetone,

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methylene chloride, PCE, toluene, and TCA), acids, bases, alcohols, and other compounds. The handling of solvents and repackaging of TCA was discontinued in 1989.

Multiple site assessments and RIs have indicated that the largest VOC release occurred at F&B, which formerly used PCE in a vapor degreaser. Current and anticipated future land use is industrial.

PCE is the primary contaminant of concern (COC) identified at the Site. Other COCs identified in the 2009 RI include TCE, TCA, and 1,1-dichloroethene (1,1-DCE). These COCs have been identified in soil, soil vapor, and groundwater. Some of the earlier investigation reports identified other COCs but subsequent sampling and analyses has shown reduced concentrations (below the Aquifer Water Quality Standards [AWQS]) and they are no longer on the COC list. Groundwater is the most significantly impacted environmental medium based on the areal extent of COCs detected at concentrations above the AWQSs. The boundaries of the impacted area of the Site are defined by the current extent of the VOC plume in groundwater covering approximately 30 acres (Figure 2-1).

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2.0 SITE CHARACTERISTICS

2.1 NATURE AND EXTENT OF CONTAMINATION

2.1.1 Source of Releases

Data collected during the RI indicate that contaminant releases occurred in soil and groundwater at the Site (Figure 2-1). No other media of concern other than soil, soil vapor, and groundwater have been identified for the Site. COCs which have been detected above regulatory or risk-based levels at the Site include PCE, TCE, and 1,1-DCE. The largest identified source of the COCs at the Site is from the F&B property.

2.1.2 Soil/Soil Vapor

The distribution of COCs in the vadose zone has been defined by soil and soil gas samples collected from numerous soil borings drilled across the Site. Based on these investigations, PCE, TCE and 1,1-DCE were the dominant chemicals detected in soil. The contaminant distributions in soil resulting from COC releases at the Site are described in the following paragraphs.

Soil. At the F&B property, the results of previous investigations indicate that soil directly beneath the degreaser is the primary source for PCE in the vadose zone and in underlying groundwater. PCE was detected in a soil sample collected beneath the degreaser from a depth of approximately 5 feet below ground surface (bgs) at a concentration of 5,400 milligrams per kilogram (mg/kg). PCE was also detected at 710 mg/kg (40 feet bgs), 180 mg/kg (80 feet bgs), and 66 mg/kg (100 feet bgs) beneath the degreaser. Highly contaminated soils from beneath the vapor degreaser sump were removed by excavating to a depth of approximately 11 feet bgs. The removed soil contained concentrations as high as 1,100 mg/kg of PCE. The deeper sampling data indicate that PCE released from the degreaser likely migrated vertically through the vadose zone to groundwater.

At the Pyramid facility, elevated concentrations of PCE and methylene chloride have been detected in the southwestern portion of the facility. The highest concentrations of PCE in soil were detected at 80 feet bgs (2.5 mg/kg) and were detected at concentrations above the minimum groundwater protection level (GPL). Although PCE use at Pyramid has not been documented, analytical results of shallow soil samples collected from the southern and western portions of the facility indicate that possible releases occurred near the loading dock/dry well, paint room, and historical hook cleaner areas. Methylene chloride and PCE were detected in the dry well sediment sample. Samples collected from soil borings drilled near the

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dry well also had detectable concentrations of these contaminants, indicating that contaminants may have been introduced to the subsurface through the dry well. An on-site source area for 1,1-DCE and TCE was not clearly identified.

Rinchem operated a chemical warehouse and distribution facility that handled solvents, oils, and fuels. Chemicals were stored in a tank farm located on the western side of the property. A repackaging area and chemical processing area were located immediately adjacent to the tank farm. Tarr took over operations of the facility in June 1993 and conducted similar operations as Rinchem. Tarr reportedly constructed a new bulk chemical storage tank farm and did not use the former Rinchem tank farm. Soil samples collected at the facility indicate the presence of VOCs such as PCE, 1,1-DCE, TCA, dichloroethane (DCA), and cis-1,2-dichloroethene (cis-1,2-DCE). The highest concentrations of PCE, TCE, TCA, and methylene chloride were detected in soil samples from boring B-13 at 30 and 50 feet bgs, located near a concrete sump in the former repackaging area. The VOCs were detected at 21 mg/kg, 1.2 mg/kg, 17 mg/kg, and 0.78 mg/kg, for PCE, TCE, TCA, and methylene chloride, respectively. Surficial soil samples collected in the former tank farm area also contained concentrations of benzene, toluene, ethylbenzene, total xylenes, and petroleum hydrocarbons.

Analytical results for soil and soil-gas samples collected in May 2002 near the former repackaging area and Sump-1 suggest that contaminated soils still exist in the subsurface. Concentrations of VOCs were detected in soil samples to a depth of 130 feet bgs. PCE was detected above its soil remediation level (SRL) and/or minimum GPL to a depth of 40 feet bgs. TCE was detected above minimum GPLs at 20 and 25 feet bgs. Concentrations of acetone, cis-1,2-dichloroethene, 1,1-dichloroethane, methyl ethyl ketone (MEK), 4-methyl-2-pentanone, toluene, ethylbenzene, and total xylenes were also detected in soil samples.

Hill Brothers operated a chemical warehouse and distribution facility that handled solvents, oils, and fuels. Chemicals were stored in a tank farm located on the western side of the property. A repackaging area and chemical processing area were located immediately adjacent to the tank farm to the north. Soil samples collected at the facility indicated the presence of VOCs. PCE has been detected at low concentrations in soil from 5 to 100 feet bgs in the former solvent repackaging area.

Soil Vapor. A soil vapor plume extends from the ground surface to the water table (approximately 150 feet bgs) in the source area at F&B. As an ERA, a soil vapor extraction (SVE) system has operated at the F&B facility for more than 15 years at the primary area of the PCE release (the location of the former vapor degreaser). Historical soil vapor concentrations at F&B are indicative of a dense non-aqueous phase liquid (DNAPL) release. DNAPL is likely

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present as ganglia (i.e., disconnected tiny droplets of PCE trapped in the pore space of the soil) as opposed to a continuous pool within the vadose zone beneath the source area. These PCE residues act as a continuing source of soil vapor and groundwater contamination.

2.2.3 Groundwater

Based on groundwater monitoring data collected at the Site, concentrations of 1,1-DCE within groundwater monitoring wells located at the Site currently exceed Arizona’s AWQS of 7 micrograms per liter (µg/L). Concentrations of PCE and TCE in groundwater exceed the AWQS of 5 µg/L. The VOC plume in groundwater is primarily present in the upper and middle intervals of the middle alluvial unit (MAU). The highest VOC concentrations are located in the area near the former vapor degreaser at F&B. Lower concentrations are found near the other three identified facilities. As of 2014, approximately 70 percent of the PCE plume footprint (at a 1,000 μg/L contour) had migrated outside the boundary of the F&B property due to groundwater transport (see Figure 2-1, the F&B property extends to the N 40th Avenue approximately 240 feet to the west of the Building outlined). Additionally, both TCE and 1,1- DCE have been detected in the upper interval of the MAU (see Figures 2-2 and 2-3, respectively).

In the middle MAU (approximately 250 feet bgs), a smaller lobe of the PCE plume extends to the west (about 900 feet) to the area near the Glenrosa Service Center (GSC). PCE concentrations are lower than in the upper MAU (see Figure 2-4). It appears that VOC plume migration is continuing in this area.

Groundwater analytical data collected in February 2000 indicated an increase in TCE and PCE concentrations in groundwater beneath the Rinchem/Tarr facility. The highest TCE concentration detected was 140 µg/L. The highest PCE concentration detected was 23 µg/L. Concentrations steadily declined following the highest detections. In the area around the Rinchem/Tarr facility, ongoing reductive dechlorination processes were identified in the Final RI Report. Natural attenuation parameters and the presence of the degradation “daughter products” cis-1,2-DCE and vinyl chloride downgradient from the source area indicate that dechlorination processes are occurring. Although not described in more recent sampling reports, the measured concentrations were less than the AWQS for cis-1,2-DCE, which is important to note because it indicates that dechlorination processes are likely occurring. Analytical data from the 2013 sampling event identified cis-1,2-DCE in and around the Rinchem facility and downgradient toward the Hill Brothers facility. This degradation daughter product (cis-1,2-DCE) was detected in the following wells: GSC-46, WCP-54, WCP-75, WCP-221, WCP-222, and WCP-224.

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In general, the VOC plume is not believed to extend below the MAU. While some of the multi-level sampling wells installed in the early 1990s (Westbay Wells) have had VOC detections at depths below the MAU, those detections are thought to be associated with well construction rather than plume migration to those depths.

2.2.4 Surface Water

Surface water was not identified as a media of concern for the Site in the RI or the FS. However, the following information regarding surface water as an environmental media is provided for perspective and completeness. The Grand Canal is located approximately 1 mile to the south of the Site. Historically, the canal had influenced groundwater flow in the immediate area. A concrete liner was placed in the canal in January 1998. The canal was originally constructed above grade to prevent surface-water runoff from entering the canal. Prior to emplacement of the concrete liner, a considerable quantity of water percolated through the bottom of the canal into the vadose zone. It was generally believed that this caused a groundwater mound along the axis of the canal creating horizontal gradients to the north and south of the canal axis. However, since the emplacement of the concrete liner, the canal’s influence on local groundwater flow has diminished.

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3.0 NEED FOR REMEDIAL ACTION

The purpose of this section is to summarize the risks at the Site and the major goals of remedial action at the Site as presented in the Site RI and FS.

3.1. SOIL/SOIL VAPOR

Multiple investigations and ERAs have been implemented at the Site to target potential areas with soil contamination. The ERAs include excavation of approximately 210 cubic yards of VOC-contaminated soil at the F&B facility, installation of an SVE system at the F&B facility; and installation of a SVE system at the Hill Brothers facility. The soil contact exposure pathway was found to be generally in compliance with standards for industrial land use at each of the areas/facilities investigated (i.e., concentrations of COCs were less than the nonresidential SRLs). In addition, contaminated soil is located beneath paved (generally inaccessible) areas at each industrial facility.

COC concentrations in deeper soil samples from F&B exceeded the minimum GPLs. These samples were collected near the area of DNAPL release and significant remedial actions (SVE operations) have occurred since that time (starting in 2001). COC concentrations in soil samples from Rinchem also exceeded minimum GPLs. COCs were detected in soil samples from Pyramid but did not exceed minimum GPLs. Similarly, COCs were detected in soil samples from Hill Brothers but did not exceed minimum GPLs.

Based on soil sample and soil vapor data, soil remediation is necessary at the F&B facility. Because current groundwater quality data indicate that COC concentrations are stable or decreasing at groundwater monitor wells at and downgradient of Rinchem, soil contamination remaining in soils at Rinchem are not affecting groundwater quality and do not require remediation. Because soil data do not exceed non-residential SRLs and minimum GPLs at Pyramid and Hill Brothers, soil remediation is not required at these facilities.

A soil vapor plume extends from the ground surface to the water table (approximately 150 feet bgs) in the source area at F&B. An SVE system has operated at the F&B facility for more than 15 years at the primary area of PCE release (the location of the former vapor degreaser). Historical soil vapor concentrations at F&B are indicative of a DNAPL release. These PCE residues act as a continuing source of soil vapor and groundwater contamination.

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3.2 GROUNDWATER

Multiple investigations and a recent ERA have been implemented at the Site to target VOCs in the groundwater. The ERA included the installation of three injection wells at the F&B source area for enhanced reductive dechlorination (ERD) using a carbon based substrate. Currently PCE, TCE and 1,1-DCE concentrations in groundwater exceed their respective AWQS of 5 µg/L for PCE and TCE and 7 µg/L for 1,1-DCE. Although groundwater at the Site is not currently used as a drinking water supply, the regional aquifer is considered a water supply for municipal and irrigation purposes in the vicinity of the Site. Therefore, the aquifer must be protected and a remedial action for groundwater is required.

3.3 SURFACE WATER

Surface water was not identified as a media of concern for the Site in the RI or the FS. Therefore, no remedial action for surface water is required.

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4.0 REMEDIAL OBJECTIVES

Remedial Objectives (ROs) for the Site were developed by ADEQ to meet requirements established under A.A.C. R18-16-406 and were originally presented in the Remedial Objectives Report (ADEQ, 2008).

ROs were established for the current and reasonably foreseeable uses of land and waters of the state that have been or are threatened to be affected by a release of a hazardous substance. The final remedy must be able to achieve the ROs.

4.1 REMEDIAL OBJECTIVES FOR LAND

The land use throughout the WCP NP area has long been established and is designated as A-2 Industrial with no foreseeable changes in the land use zoning.

ROs for land use are established for those properties known to be contaminated with hazardous substances above a SRL or a risk-based level. The RO for soils and land use established for the Site are to protect against possible exposure to hazardous substances in surface and subsurface soils that could occur during typical industrial uses. This action is needed for the present time and for as long as the level of contamination in the soil threatens its use as a non-residential property.

4.2 REMEDIAL OBJECTIVES FOR GROUNDWATER

Groundwater is not currently used on Site, however, the regional aquifer is considered to be a municipal and irrigation water supply in the vicinity of the Site which must be protected. The RO for current and reasonably foreseeable future groundwater use in and near the Site is to protect the supply of groundwater for municipal and irrigation use and for the associated recharge capacity that is threatened by contamination emanating from the WCP NP Site. To restore, replace or otherwise provide for the groundwater supply lost due to contamination associated with the WCP NP site. This action will be needed for as long as the need for the water exists, the resource remains available and the contamination associated with the WCP NP Site prohibits or limits groundwater use.

4.3 REMEDIAL OBJECTIVES FOR SURFACE WATER

Surface water was not identified as a media of concern for the Site in the RI or the FS. Therefore, no ROs are needed for surface water.

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4.4 REMEDIATION LEVELS AND BASIS FOR SELECTION

As previously noted in the beginning of Section 2.0, the COCs identified at the Site are PCE, TCE, and 1,1-DCE. The soil and groundwater standards for the COCs are shown in Table 4-1.

Table 4-1. Relevant Soil and Groundwater Standards for Primary Contaminants of Concern

Media: Groundwater Soil Contaminant of

Concern AWQS (μg/L)

Minimum GPL (mg/kg)

Non-residential

SRL (mg/kg)

PCE 5 0.80 13 TCE 5 0.76 65

1,1-DCE 7 0.85 410

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5.0 EVALUATION OF REMEDIAL ALTERNATIVES

In accordance with the Remedy Selection Rule (A.A.C. R18-16-407), the FS must identify at least three alternative remedies capable of achieving the ROs. As documented in the FS, three alternatives were evaluated for remediation of soil and groundwater at the Site. These alternatives are as follows:

• Reference Remedy: Vadose zone source control (SVE for the source area soil/soil vapor at F&B), Saturated zone source/plume treatment (using biological treatment/ ERD for in-situ plume treatment in groundwater), and Plume migration monitoring (monitored natural attenuation (MNA) to verify degradation of COCs and plume stability),

• More Aggressive Remedy: Vadose zone source control (SVE for the source area soil/soil vapor at F&B), Saturated zone source/plume treatment (using biological treatment/ERD) for the VOC plume out to an estimated level of the 100 μg/L contour, and Plume migration control/monitoring using groundwater extraction and treatment,

• Less Aggressive Remedy: Vadose zone source control (SVE for the source area soil/soil vapor at F&B), Plume migration monitoring (MNA to verify degradation of COCs and plume stability); and, a Contingency for well-head treatment at a supply well at some time in the future.

The FS also contained a Contingency for well-head treatment if a municipal supply well is installed within the Site at some time in the future.

5.1 PROPOSED REMEDY

The Reference Remedy consisting of Vadose zone source control (SVE for the source area soil/soil vapor at F&B), Saturated zone source/plume treatment (using biological treatment/ERD for in-situ plume treatment in groundwater), and Plume migration monitoring (MNA to verify degradation of COCs and plume stability) is the proposed remedy for the Site.

As noted in the summary of groundwater conditions and the remedial objectives, groundwater at the Site is not currently used for water supply but the regional aquifer is considered a potential water supply for municipal and irrigation purposes. Based on this future-use consideration, a remedial action for groundwater is warranted but the specific timing required is less certain. ADEQ needs to balance current/future Site risks and resources required/available for groundwater restoration. The timing of remedial activities for groundwater restoration may be adjusted or revised based on these considerations. The approach and cost estimate in this PRAP is based on incremental implementation of the ERD

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remedy. The proposed remedial action is based on an adaptive management approach where the treatment wells are installed incrementally along with data collection to further refine the required treatment area; in-situ treatment wells would be installed over a 4-year period with treatment starting in the first year. The estimated duration of treatment operation is a 10-year period (this includes continued ERD treatment for 6 years after completion of the initial 4-year period used for treatment system expansion and the adaptive management plume characterization). This approach is expected to be a cost-effective strategy to achieve the ROs. Other schedules/strategies for ERD implementation at the Site are feasible and may be considered as necessary based on Site risks and resources available.

Vadose Zone Source Control (SVE). Continued operation and optimization of the SVE system at F&B should contain the soil vapor plume and will continue to remove VOC mass present in the vadose zone; the benefit derived from this SVE operation is primarily the control and removal of PCE residues from the vadose zone that would otherwise serve as a long-term source of groundwater contamination. The required operating period for the SVE system will depend on performance data collected associated with system operation. For the purpose of this PRAP the SVE system is estimated to operate for a 20-year period with optimization and reduction in the frequency of SVE system operation in the later years. The decrease in groundwater elevations at the Site over the past several decades has resulted in a recently exposed vadose zone (at depth near the zone that is a suspected DNAPL source area), and the recent installation of three deeper SVE wells will likely be beneficial for continued mass removal to reduce the source of groundwater impact. The SVE system had removed approximately 51,000 pounds of VOCs as of January 2017. Recent SVE system operation (in the first quarter of 2017) is removing approximately 9 pounds of VOCs per day (primarily as PCE).

The existing SVE system consists of eight SVE wells placed at varying depths within the vadose zone beneath the former vapor degreaser at F&B (the primary source of release of PCE to the subsurface). The layout of the SVE system based on recent SVE system inspections and operational tests is shown in Figure 5-1.

Optimization of the SVE system would likely include the following techniques or combination of techniques:

• Focused Extraction: The existing SVE system can be optimized to enhance the removal of the remaining mass by focusing extraction on existing wells that are more effective at extracting source area VOCs (as evidenced by regular field monitoring) and by shutting off extraction wells that no longer appear to be effective in removing VOCs.

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Routine monitoring will allow periodic shifting of active wells to maximize source removal. This type of remedial optimization is presently underway and an additional planned change is the use of existing selected SVE vent wells as air infiltration points to change the vapor flow paths. This is expected to last for a period of seven years.

• Pulsed Operation: As the remaining VOC mass becomes more diffusion-limited, SVE operation can be transitioned to a periodic or “pulsed” operation such that active extraction occurs in intervals separated by periods of no extraction. Pulsed extraction is unlikely to increase the mass removal rate but may significantly decrease the operating expense (for a reduced, but sufficiently effective, mass removal rate). The intent of pulsed SVE operation is to allow diffusion from low-permeability lenses into more permeable pathways and then periodically remove the vapors from those more permeable layers. An example is that an SVE system may be operated for 1 week once every 2 months (an ~11 percent run-time operation cycle), which could reduce the operating costs by 75 to 80 percent. This later phase of SVE operation is expected to last for a period of 13 years.

• Additional SVE Wells: Three SVE wells (SVE-6, SVE-7, and SVE-8) were installed in 2013 deeper than the previously installed SVE vent wells to target the deeper vadose zone because the groundwater elevation has declined approximately 30 feet since the mid-1990s. Recent testing/remedial optimization indicates that these new extraction wells appear to be effective in recovering additional VOC mass that has been more recently exposed. Additional SVE wells are not deemed necessary at this time, however additional SVE vent wells may be added to the system if warranted in the future.

As described in Section 3.1, soil remediation is not required in other areas of the Site because the ROs for soils and land use are met.

Saturated Zone Source/Groundwater Plume Remediation (ERD). Implementation of an ERD remedy for groundwater plume remediation is proposed for the area of the plume with PCE concentrations greater than 1,000 μg/L in the upper MAU plume (red plume contour shown in Figure 5-2). ERD is a remedial technology based on injecting substrates/nutrients into groundwater to promote anaerobic biodegradation. Anaerobic reductive dechlorination is a naturally occurring biodegradation process whereby microbes can degrade chlorinated VOCs in groundwater. The microbes use a primary substrate as a carbon and energy source, producing enzymes and provide electron donors to facilitate degradation of the target chlorinated compounds present in groundwater. Most applications use a bio-stimulation substrate (such as a soluble food-grade sucrose-based solution or edible oil substrate [EOS]) to provide a carbon source for driving the aquifer redox conditions lower and at the same

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time provide a fermentation substrate that releases hydrogen to serve as an electron donor (required for the dechlorination reactions).

A limited amount of additional data are required to characterize and quantify the areal extent requiring treatment at the target action level. As shown in Figure 5-2, groundwater treatment would be implemented in a series of injection well transects located perpendicular to the primary groundwater flow direction (to the northwest). The network of ERD wells will be installed/expanded using an adaptive management approach. Using this approach, the new treatment wells will be installed and sampled and then included as a treatment well or retained as a new plume boundary monitoring well. The wells would be installed sequentially so that the results of the wells installed first could be used to inform decisions about where to put subsequent wells. The cost estimate shown in Appendix A includes as many as twenty treatment wells that would be installed for this portion of the remedy (the cost estimate also includes 5 new monitoring wells described further in the discussion of the MNA phase of the project). The wells would be installed over a four-year period so that data from early treatment wells could be used to optimize plume treatment. The wells would be constructed with two or three screened zones in each well with a seal between the screened intervals to allow depth-specific injection in zones with the highest COC concentrations. Groundwater treatment would be implemented in phases at various treatment wells by injecting bio-remediation agents over a ten-year period. After the start of ERD treatment, groundwater samples would be collected at the treatment wells and other nearby monitoring wells to track the progress of the remedy. As noted in the introduction to this section, differing schedules/strategies for ERD implementation will be considered for groundwater restoration as necessary which would also modify the schedule and corresponding costs for the MNA elements of the remedy.

Plume Monitoring (MNA). Degradation is currently occurring in the downgradient portions of the plume, as documented by the presence of PCE daughter products (TCE, cis 1, 2-DCE, vinyl chloride, and 1,1-DCE) and will continue to be monitored until the cleanup levels are achieved, which is calculated to take 30 years. The combination of MNA in areas of the plume with lower COC concentrations and more active source control (SVE) and plume remediation (ERD) in areas of the plume with higher concentrations is a reasonable approach to Site remediation.

During the ERD phase (proposed as years 0-10 in the baseline schedule), monitoring is expected to include semi-annual monitoring of key monitoring wells used for ERD performance monitoring and annual monitoring that includes a more comprehensive plume-wide monitoring well network, primarily in the upper and middle MAU for a period of 10 years.

16

MNA would be the primary remedy component for groundwater in years 10-30. Annual monitoring of 20 wells (approximately) would be implemented in years 11-20 with a smaller group (approximately 10 wells) monitored in years 21-30.

MNA as part of the reference remedy would involve routine groundwater monitoring of key monitoring wells, including monitoring of natural attenuation parameters and the collection of analytical data for chlorinated VOCs. MNA is a remedial measure that involves routine groundwater sampling and analysis to monitor the results of one or more naturally occurring physical, chemical, and/or biological processes that reduce the mass, toxicity, volume, or concentration of chemicals in groundwater. MNA is a mechanism by which COCs are reduced (often slowly) by natural means without other control, removal, treatment, or aquifer-modifying activities. These in-situ processes may include biodegradation, dispersion, dilution, sorption, and volatilization of contaminants. Natural dechlorination is occurring in some downgradient portions of the plume as evidenced by the presence of PCE daughter products (TCE, cis 1, 2-DCE, vinyl chloride, and 1,1-DCE). These processes causing dechlorination are likely to persist. However, the plume is actively moving at the Site such that ROs cannot be met within a reasonable restoration time frame relying on MNA alone. Therefore, MNA is not a viable stand-alone measure and will be utilized at the Site in the plume areas outside of the 500 µg/L PCE contour. This remedial measure will involve annual groundwater monitoring at select wells throughout the plume to verify that attenuation continues to occur at the Site. Calculations indicate that the COCs should be remediated to ROs within 20 years of the last substrate injection. Therefore, Site-wide monitoring is included for an additional twenty years, for a total of thirty years. The monitoring duration would be shortened as warranted by the monitoring results.

It may be necessary to install an additional five monitoring wells for sufficient monitoring of the upper MAU because several wells have been dry in recent years due to the declining water table. These monitoring wells may be installed in addition to the treatment/monitoring wells installed as part of the ERD component of the remedy. The implementation of ERD combined with MNA in the reference remedy is anticipated to have synergistic effects because the ERD process will accelerate degradation processes (dechlorination) that are the basis of the MNA component. The benefits from the ERD portion of the remedy are expected to include a 95-99 percent reduction in source zone concentrations and, at the same time, more rapid dechlorination rates over a wider footprint of the VOC plume where the MNA will be implemented (i.e., the VOC plume derived from F&B which is the primary target of the remedial actions).

17

5.2 RATIONALE FOR SELECTION OF REFERENCE REMEDY

Based on comparisons of the remedial alternatives contained in the FS, the Reference Remedy is the most feasible and practicable remedial approach for the Site given current and future use scenarios. This remedy is considered protective of public and ecological health; the current exposure pathway to Site groundwater is incomplete and active measures along with monitoring would be implemented to restore water quality. Since the fate and transport of Site contaminants is reasonably well known, and remedial actions are implemented to restore water quality to levels below AWQS standards, the residual risk to the aquifer is anticipated to be low.

The reference remedy includes a combination of SVE for source-area soils, hot spot or expanded plume area groundwater treatment (using ERD) and MNA. It is a feasible and practicable remedial solution for the Site. It provides both short- and long-term effectiveness for plume remediation, vadose zone control, and plume monitoring. The reference remedy combines proven and reliable technologies known to effectively reduce contaminant concentrations in both soil and groundwater to meet the ROs. In accordance with ACC R18-16-407 (G), these actions are consistent with plans of potentially affected water providers and their long-term water management plans.

Given that this remedy uses the currently installed SVE system at F&B, the practicability and effectiveness of continued operation of the SVE system is known. The optimization of the SVE system, including the recent addition of more extraction wells to the network, will increase the overall performance of the system, resulting in greater long-term effectiveness.

The ERD component of this remedy has been used effectively across the United States to substantially reduce chlorinated solvent concentrations in groundwater; concentration reductions of 99+ percent have been documented on large chlorinated solvent plumes. Thus, the technology has been proven and shown to be reliable. By specifically targeting the highest concentrations of PCE in the groundwater plume, this remedial approach will provide both short- and long-term effectiveness in reducing VOC concentrations and plume expansion in groundwater.

The MNA component of this remedy is a proven remedial strategy when the site conditions are appropriate. It provides both short- and long-term effectiveness. The existing Site data indicate that select downgradient portions of the plume demonstrate attenuation by both degradation and dispersion. Long-term monitoring (the monitoring portion of MNA) has been occurring over the past 20 years, and it is anticipated to continue for years into the future. When coupled with the ERD component of the plume treatment, the MNA component of the

18

reference remedy is anticipated to provide reliable short-term and long-term effectiveness/performance.

The SVE system is already installed at F&B and operating successfully; therefore, current risks from a vapor pathway are low and have been mitigated. Multiple Site assessments and remedial investigations have defined the nature and extent of VOCs in soil. The fate and transport of soil vapor at F&B is readily predicted under the influence of the SVE system. The SVE system removes contaminants from soil and treats them with granular activated carbon before discharge to air. Future land use at the Site is not expected to change from the current mixed industrial; therefore, the risk of exposure to any other COC residues in subsurface soils is considered low.

The ERD component of the remedy is an in-situ treatment process (no discharges), and the COC degradation will reduce future risks (i.e., the concentration and related toxicity of Site contaminants will be reduced).

The MNA component of the remedy is considered protective of public and ecological health because the current exposure pathway to Site groundwater is incomplete. Based on current and historical groundwater data, PCE appears to be slowly attenuating near the leading edge of the plume as a result of degradation and dispersion. The groundwater in the area of the Site is not used for drinking water; however, groundwater is designated as a potable resource for the future, if needed. Residual risk during implementation and after the completion of remediation is low; there is no current exposure pathway.

In summary, the combined components of the reference remedy are consistent with current and anticipated future land and resource use. All known exposure pathways are addressed, and the remedial actions will reduce concentrations such that future foreseeable use of land and the groundwater resource will meet the acceptable risk thresholds. Groundwater monitoring (as part of MNA) is included to verify that the remedy is protective of public health and the environment during and after remedy implementation.

5.3 PERFORMANCE MONITORING RECOMMENDATIONS

ERD will be implemented by completing substrate injection events in the three wells that were installed in early 2016 (ERD-IW1, ERD-IW2, and ERD-IW3, see Figure 5-2) as part of an optimization of the source area ERA. During each injection event, the field crew will add a sugar-based substrate solution with a goal of achieving approximately 1,000 mg/L (0.1 percent) sugar solution in an assumed radius of 25 ft around each well. Based on experience from the first two injection events in 2016, this will require between 1,000 and 1,500 gallons

19

of solution per well (Matrix-CALIBRE 2016b) targeted between the multiple screen intervals. The solution will be mixed in an onsite tank. Volumes and type of substrate will be adjusted based on remedial progress.

Initially spacing of additional injection wells is based on aquifer characteristics determined by the aquifer tests conducted during the RI. However, data collected during initial injection well installations and initial injections indicate that the coarser grained lenses within the aquifer may be thinner than previously calculated. Therefore, additional injection wells will be installed based on results of the initial injections and sampling along with previously determined aquifer characteristics.

Performance monitoring will be used to judge the effectiveness and adequacy of the remedy proposed for groundwater at the Site. Existing wells and new wells installed as part of the remedy will be monitored to evaluate the progress of the remedy. Monitoring will continue as long as contamination is present in groundwater, although it is anticipated that the number of wells to monitor and the frequency of monitoring will be adjusted over time in response to changing groundwater conditions.

A.R.S § 49-282.06(A) defines the overall performance requirements for the proposed remedy which include: 1) Protect public health and welfare and the environment; 2) To the extent practicable, provide for the control, management, or cleanup of the hazardous substances in order to allow the maximum beneficial use of the waters of the state; 3) Be reasonable, necessary, cost-effective, and technically feasible. This last factor, technical feasibility, is a key consideration in establishing performance metrics for the proposed remedy.

The primary hazardous substance release identified at this Site involves chlorinated VOCs released from a vapor degreasing operation at the F&B facility. This type of release (i.e., a neat solvent [PCE] from a degreasing operation), the historical groundwater concentrations, and the historical soil vapor concentrations indicate the presence of solvent as DNAPL. It is anticipated that some DNAPL remains as ganglia within finer grained layers in the vadose zone, and it is possible that some may have migrated down to and into the saturated zone. Treatment of DNAPL source areas is challenging because of the difficulty of identifying the location and distribution of DNAPL. Experience at hundreds of sites nationally has demonstrated that full restoration at DNAPL sites is often not possible. Based on technological limitations, practicable remedies for DNAPL sites must consider source reduction and/or containment of the source areas.

Source reduction is typically preferred over containment remedies because source reduction (removal of VOCs in the source area) will result in a reduction in mass flux, a reduction in

20

source longevity, a reduction in risk, and potential enhancement in post-treatment biodegradation potential. Even with large reductions in source area VOC mass (up to the limit that is technically feasible) the remaining contaminant mass after treatment can still continue to serve as a continuing source of groundwater contamination. Therefore, additional source-zone treatment, containment, and/or long-term monitoring is often required to achieve compliance with the required cleanup objectives.

The recommended remedy includes source control, plume treatment for higher concentration portions of the VOC plume, and controlled migration (including MNA) for lower concentration areas of the VOC plume. The recommended remedy also includes a contingency for well-head treatment options if future supply wells are impacted by the VOC plume and are intended for use as a drinking water source. As a DNAPL site, all remedial actions need to be planned for multiple years of operation. The general performance metrics and associated monitoring are described below. An initial list of wells to be sampled are shown in Tables 5-1. The final list of wells and appropriate sampling frequency will be developed in the remedial design.

Source Area Treatment

This element of the remedy will operate for up to 10 years with the objective to achieve concentration reductions of 95% to 99+% in the key source areas; concentrations in some wells may still be above the AWQS. Multiple wells will be monitored in this area during the treatment period.

Plume Wide Treatment

This element of the remedy will operate for up to 10 years with the objective to achieve concentration reductions of 95% to 99+% throughout the areas treated; concentrations in some wells may still be above the AWQS. Multiple wells will be monitored in this area during the treatment period.

MNA Phase

This element of the remedy may operate for a period of 30 years with the objective to achieve a stable plume at the AWQS boundary/iso-concentration contour. The MNA program would start in the plume periphery areas in years 1-10 while the ERD remedy was implemented. The later MNA sampling would include annual sampling from up to 20 wells and decline over time. Table 5-1 lists 16 existing monitoring wells to be included in the MNA program, additional wells may be added (or changed) with further plume characterization in the remedy

21

implementation. The number of wells included in the MNA program is expected to be reduced over time.

Contingency for Well-Head Treatment

If the resource is used for water supply, the extracted water is treated to meet the quality standards for the intended use. Monitoring of the water supply would be implemented in accordance with the applicable regulations and other site-specific procedures/frequency.

5.4 ACHIEVEMENT OF REMEDIAL OBJECTIVES

Per A.C.C. R18-16-408(B)(3), the proposed remedy will achieve each of the ROs established by ADEQ for the Site as described in Sections 4.1 and 4.2 of this PRAP.

22

Table 5-1 Existing Wells Which May be Sampled to Evaluate ERD Performance and for Periodic Sampling

Well VOCs Field Parameters Selected

Attenuation Parameters

ERD-IW1 X X X

ERD-IW2 X X X

ERD-IW3 X X X

F&B-1 X X X

WCP-237 X X X

GSC-25A X X

GSC-22A X X

GSC-39 X X

GSC-48 X X

GSC-34 X X

WCP-224 X X

GSC-40 X X

GSC-01A X X

GSC-23 X X

WCP-72M X X

FB-2-259 X X

The initial group of “selected attenuation parameters” includes Dissolved Oxygen, Redox Potential, pH, Total Organic Carbon and Sulfate; changes to this analyte list may be developed in the remedial design and/or adapted over the project lifecycle.

5.5 ACHIEVEMENT OF REMEDIAL ACTION CRITERIA

A.R.S. § 49-282.06 requires that remedial actions shall:

Assure the protection of public health and welfare and the environment. To the extent practicable, provide for the control, management or cleanup of the

hazardous substances in order to allow the maximum beneficial use of the waters ofthe state.

Be reasonable, necessary, cost-effective and technically feasible.

23

As demonstrated in this PRAP, the proposed remedy meets the requirements of A.R.S. § 49-282.06. The proposed remedy is protective of human health and the environment, compliant with applicable laws, and allows for the maximum beneficial use of the waters of the State with the lowest cost. Further, the proposed remedy is the best combination of practicability, risk, cost, and benefit to achieve the ROs.

5.6 CONSISTENCY WITH WATER MANAGEMENT PLANS

The proposed remedy is consistent with water management plans; no active supply wells are currently impacted by the plume and remedial actions are proposed to restore water quality. This remedy will allow for the maximum beneficial use of the waters of the State, protect the groundwater supply for future use, and ensure that wider areas are not impacted for future water development options. A contingency is included for well-head treatment if a production well should be installed within the Site and its use is restricted by existing groundwater contamination.

5.7 CONSISTENCY WITH GENERAL LAND USE PLANNING

With regard to land use impacts, minor new construction (well installation) is necessary to implement the proposed remedy. The proposed remedy is consistent with the existing commercial land use and is not anticipated to negatively impact current or future land use at the property.

5.8 SUMMARY OF COSTS TO IMPLEMENT THE PROPOSED REMEDY

The proposed remedy is a cost-effective remedial alternative for the Site. The active operation of the SVE system is expected to continue for up to 7 years with additional optimization and reduced operation for up to the next 13 years. The treatment of the groundwater via ERD is expected to take place over a 5- to 10-year time frame, with groundwater monitoring (MNA) expected over the entire 30-year time frame. The overall costs of the proposed remedy based on the planned well configurations (see Figure 5-2) is expected to be approximately $6,041,600.

• ERD Remediation $2,565,000 • SVE Remediation $1,685,000 • Long-Term Monitoring (MNA) $1,076,000 • Closure $715,600

24

A detailed cost breakdown is presented in Appendix A.

5.9 LEAD AGENCY STATEMENT FOR PROPOSED REMEDY

Based on the information currently available, ADEQ believes the proposed remedy provides the best approach among the other alternatives with respect to the comparison criteria. ADEQ expects the proposed remedy will satisfy the remedial action criteria pursuant to A.R.S. § 49-282.06 (Section 6.3) and the ROs (Section 4).

5.10 CONTINGENCY FOR PROPOSED REMEDY

Two contingencies have been developed for the Proposed Remedy. The first contingency is to accelerate the in-situ treatment if future groundwater use requires it and/or added resources are available. If additional funding is available, an additional 10 to 15 wells can be installed throughout the core and fringe areas of the contaminant plume and ERD injections conducted at six month intervals for a period of approximately five years at a cost of $818,000 to $1,261,000. The cost range noted would depend on the timing of contingency implementation, the specific objectives, and the number of wells installed. This contingency is calculated to reduce the timeframe of the proposed remedy by as much as 10 years.

The second contingency is to provide wellhead treatment for a new City of Phoenix or other municipal well that could theoretically be installed within the plume at an additional cost of $2,625,000.

25

6.0 COMMUNITY INVOLVEMENT

6.1 PUBLIC COMMENT PERIOD OF PRAP

The public comment period will be no less than 90 days. ADEQ will accept written and/or verbal comments on this PRAP that are postmarked within the comment period and submitted to:

Arizona Department of Environmental Quality ATTN: Kevin Snyder, Project Manager 1110 West Washington Street Phoenix, Arizona 85007

6.2 PUBLIC MEETINGS

ADEQ may present the PRAP in a West Central Phoenix North Plume WQARF Site Community Advisory Board meeting and/or public meeting. If a meeting is held, oral and written comments will also be accepted at the meeting from Community Advisory Board members and from the public.

6.3 ADMINISTRATIVE RECORD

Interested parties can review the PRAP and other Site documents online at: http://www.azdeq.gov/node/1062 or at the ADEQ Main Office located at 1110 West Washington Street, Phoenix, Arizona. With 24-hour notice, an appointment to review related documentation is available Monday through Friday from 8:30 a.m. to 4:30 p.m. at the ADEQ Records Management Center. Please contact (602) 771-4380 or (800) 234-5677 to schedule an appointment to review these documents.

6.4 OTHER CONTACT INFORMATION

Name/Title Phone/Fax E-mail

Kevin Snyder, ADEQ Project Manager (602) 771-4186 / (602) 771-2302 [email protected]

Isabel Gutierrez, ADEQ Community Involvement Coordinator

(602) 771-4257 / (602) 771-2302 [email protected]

http://www.azdeq.gov/node/1062

mailto:[email protected]

mailto:[email protected]

26

7.0 REFERENCES

ADEQ, 2008. Proposed Remedial Objectives Report, West Central Phoenix North Plume WQARF Site. July 2008.

LFR, 2009. Final Remedial Investigation Report, West Central Phoenix North Plume Site. January 2009.

Matrix-CALIBRE, 2016. Feasibility Study, West Central Phoenix North Plume WQARF Site. August 2016.

FIGURES

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GSC-48PCE =135 ug/L

WCP-77PCE =23.9 ug/L

WCP-237PCE =458 ug/L

GSC-49PCE =9.66 ug/L



GSC-01APCE =369 ug/L

WCP-38SPCE =5.45 ug/L



GSC-25APCE =1230 ug/L

GSC-22A-160PCE =735 ug/LGSC-22A-192PCE = 699 ug/L

WCP-78PCE =1.2 ug/L

GSC-17PCE =< 5 ug/L





WCP-81PCE =< 0.5 ug/L WCP-75

PCE =< 0.5 ug/L

WCP-57PCE =< 0.5 ug/L



GSC-27PCE =< 0.5 ug/L




GSC-23PCE =< 2.5 ug/L



FB-1-160PCE =7380 ug/LFB-1-185

PCE = 8370 ug/LFB-1--210

PCE = 9160 ug/L

FB-4-159PCE = 63.4 ug/LFB-1

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APPENDIX A Detailed Costs to Implement the Proposed Remedy

West Central Phoenix North Plume Site

Proposed Remedy Expanded Plume Coverage—Enhanced Reductive Dechlorination, Continued Operation and Optimization of SVE System, and MNA

Source Area Remediation Tasks Quantity Unit Unit Cost 1 Extended Cost 2,3 DetailERD REMEDIATION Year 1: Install five wells, in situ treatment at two wells.Site Survey/ Utility Locate 1 LS 2,438$ 2,500$ Traffic Permits and Traffic Control 1 LS 8,000$ 8,000$ Includes NOI, COP permits/fees, PE certified plans, COP inspection, and traffic control

operation Well Installation and development 5 Well 33,280$ 166,400$ Assumes 4-inch diameter injection wells to be installed to depth of 170 feet; wells are to be

screened at multiple depth intervals to allow for injections to be completed throughout the well depth column.

Field Oversight Well Install and Development 23 Day 1,875$ 43,200$ Includes 1 FTE for 10 hours per day plus expenses (truck, field instruments, health and safety), 4 days per well installation, development of 2 wells/day.

IDW Management and Disposal (soil, Subtitle D) 4 Rolloffs 975$ 3,900$ Assume rental of roll-off container, transport and disposal at Subtitle D landfill.IDW Management and Disposal (water) 1 LS 4,875$ 4,900$ Assumes frac tank and carbon treatment system rental, treatment and discharge to sanitary

sewer.Sample and Analysis during drilling 5 LS 1,040$ 5,200$ Characterization of materials for disposal and initial well sampling (for new wells)Drilling Report and Wells Logs 1 LS 7,500$ 7,500$ Bioaugmentation 0 Event 19,500$ -$ Bioaugmentation after Year 1, one time after all wells are at reducing conditionIn Situ Treatment 1 Event 24,563$ 24,600$ Treatment at 5 wells Treatment Performance Sampling 1 LS 3,947$ 4,000$ Monitor 5 wellsReporting,Project Management, and Permitting 1 LS 40,000$ 40,000$ Year 1 Total 311,000$

Year 2: Install five wells, in situ treatment at five wells.Site Survey/ Utility Locate 1 LS 2,438$ 2,500$ Traffic Permits and Traffic Control 1 LS 8,000$ 8,000$ Includes NOI, COP permits/fees, PE certified plans, COP inspection, and traffic control



Field Oversight Well Install and Development 23 Day 1,875$ 43,200$ Includes 1 FTE for 10 hours per day. 4 days per well installation, development of 2 wells/day.


sewer.Sample and Analysis during drilling 5 LS 1,040$ 5,200$ Characterization of materials for disposal and initial well sampling (for new wells)Drilling Report and Wells Logs 1 LS 7,500$ 7,500$ Bioaugmentation 1 Event 19,500$ 19,500$ Bioaugmentation , Year 1, one time after all wells are at reducing conditionIn Situ Treatment 3 Event 38,627$ 115,900$ Treatment at 10 wellsTreatment Performance Sampling 2 LS 6,578$ 13,200$ Monitor 10 wellsMNA monitoring 1 LS 6,578$ 6,600$ Monitor 10 wellsReporting,Project Management, and Permitting 1 LS 40,000$ 40,000$ Year 2 Total 437,000$

Year 3: Install five wells, in situ treatment at nine wells.Site Survey/ Utility Locate 1 LS 2,438$ 2,500$ Traffic Permits and Traffic Control 1 LS 6,000$ 6,000$ Includes NOI, COP permits/fees, PE certified plans, COP inspection, and traffic control



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sewer.Sample and Analysis during drilling 5 LS 1,040$ 5,200$ Characterization of materials for disposal and initial well sampling (for new wells)Drilling Report and Wells Logs 1 LS 7,500$ 7,500$ In Situ Treatment 3 Event 48,729$ 146,200$ Treatment at 13 wells each event, 3 events in year including different wellsTreatment Performance Sampling 2 LS 10,196$ 20,400$ At 13 wellsMNA monitoring 1 LS 10,196$ 10,200$ Monitor 13 wellsReporting,Project Management, and Permitting 1 LS 40,000$ 40,000$ Year 3 Total 457,000$

Year 4: Install five wells, in situ treatment at 13 wells.Site Survey/ Utility Locate 1 LS 2,438$ 2,500$ Traffic Permits and Traffic Control 1 LS 6,000$ 6,000$ Includes NOI, COP permits/fees, PE certified plans, COP inspection, and traffic control





sewer.Sample and Analysis during drilling 5 LS 1,040$ 5,200$ Characterization of materials for disposal and initial well sampling (for new wells)Drilling Report and Wells Logs 1 LS 7,500$ 7,500$ In Situ Treatment 3 Event 48,729$ 146,200$ Treatment at 13 wellsTreatment Performance Sampling 2 LS 10,196$ 20,400$ At 13 wellsMNA monitoring 1 LS 10,196$ 10,200$ Monitor 13 wellsReporting,Project Management, and Permitting 1 LS 40,000$ 40,000$ Year 4 Total 457,000$

Year 5: No new wells, in situ treatment at 13 wells.In Situ Treatment 3 Event 48,729$ 146,200$ Treatment at 13 wellsTreatment Performance Sampling 3 LS 10,196$ 30,600$ At 13 wellsMNA Monitoring 1 LS 29,765$ 29,800$ Monitor 15 wellsReporting,Project Management, and Permitting 1 LS 30,000$ 30,000$ Year 5 Total 237,000$

Year 6: No new wells, in situ treatment at eight wells.In Situ Treatment 3 Event 32,698$ 98,100$ Treatment at 8 wellsTreatment Performance Sampling 3 LS 5,262$ 15,800$ At 8 wellsMNA Monitoring 1 LS 29,765$ 29,800$ Monitor 15 wellsReporting,Project Management, and Permitting 1 LS 30,000$ 30,000$ Year 6 Total 174,000$

Year 7: In situ treatment at eight wells.In Situ Treatment 2 Event 32,698$ 65,400$ Treatment at 8 wellsTreatment Performance Sampling 2 LS 5,262$ 10,600$ At 8 wellsMNA Monitoring 1 LS 25,983$ 26,000$ Monitor 12 wellsReporting,Project Management, and Permitting 1 LS 30,000$ 30,000$ Year 7 Total 132,000$



Year 8: In situ treatment at eight wells.In Situ Treatment 2 Event 32,698$ 65,400$ Treatment at 8 wellsTreatment Performance Sampling 2 LS 5,262$ 10,600$ At 8 wellsMNA Monitoring 1 LS 25,983$ 26,000$ Monitor 12 wellsReporting,Project Management, and Permitting 1 LS 30,000$ 30,000$ Year 8 Total 132,000$

Year 9: In situ treatment at five wells.In Situ Treatment 2 Event 24,563$ 49,200$ Treatment at 5 wellsTreatment Performance Sampling 2 LS 3,947$ 7,900$ At 5 wellsMNA Monitoring 1 LS 25,983$ 26,000$ Monitor 12 wellsReporting,Project Management, and Permitting 1 LS 30,000$ 30,000$ Year 9 Total 114,000$

Year 10: In situ treatment at five wells.In Situ Treatment 2 Event 24,563$ 49,200$ Treatment at 5 wellsTreatment Performance Sampling 2 LS 3,947$ 7,900$ At 5 wellsMNA Monitoring 1 LS 25,983$ 26,000$ Monitor 12 wellsReporting,Project Management, and Permitting 1 LS 30,000$ 30,000$ Year 9 Total 114,000$

Subtotal: $2,565,000SVE REMEDIATION IN MAIN SOURCE AREA4

Optimize, Operate and Maintain SVE System for Vadose Zone, Years 1-7 7 YR 195,000$ 1,365,000$ Assumes active optimization, operation, and maintenance (including carbon and electricityLimited Operation and Maintenance, Years 7-20 13 YR 23,400$ 304,200$ Assumes limited operation for years 8-20. (run 10% of time)Equipment Replacement and Maintenance 1 LS 15,000$ 15,000$ Assumes periodic replacement of SVE components (ie blower replacement, hoses, valves,

etc.)Subtotal: $1,685,000

$4,250,000LONG TERM MONITORING COSTS (MNA) after years 1-10Monitoring Well Installation 5 Well 32,500$ 162,500$ Assumes 4-inch diameter, 170-foot monitoring wells. Per well cost from vendor.Field Oversight for Monitoring Well Install and Development 23 Day 1,950$ 44,850$ Includes 1 FTE for 10 hours per day. 4 days per well installation, development of 2 wells/day

(truck, field instruments, health and safety)IDW Management and Disposal (soil, Subtitle D) 4 Rolloffs 975$ 3,900$ Assume rental of roll-off container, transport and disposal at Subtitle D landfill.IDW Management and Disposal (water) 1 LS 4,875$ 4,900$ Assumes frac tank and carbon treatment system rental, treatment and discharge to sanitary

sewer.Annual Key Monitoring Well Sampling (Years 11-20) 10 Event 48,877$ 488,800$ Monitoring of key wells (assume 20) to be completed annually, years 11-20. Includes labor,

equipment, and laboratory analysis. Annual Key Monitoring Well Sampling (Years 21-30) 10 Event 37,036$ 370,400$ Monitoring of key wells (assume 10) to be completed annually, years 21-30. Includes labor,

equipment, and laboratory analysis. Subtotal: $1,076,000CLOSURE COSTSPermitting/Oversight 1 LS 50,000$ $50,000Monitor Well Abandonment 75 well 6,500$ $487,500 closure by groutingInjection Well Abandonment 20 well 6,500$ $130,000 closure by groutingSVE Well Abandonment 7 well 5,200$ $36,400SVE System Removal 1 LS 7,800$ $7,800IDW Management and Disposal (soil, Subtitle D) 3 bins 1,300$ $3,900 For equipment, concrete, wellhead monuments, etc.Subtotal: $715,600

$6,041,600

Remediation Cost

TOTAL REMEDIATION COST



Notes:1 All cost values are estimates and should not be interpreted as final construction or project costs. Costs are in present dollar and do not include inflation costs.2 Total values are rounded up to the nearest $10,000.3 ERD cost estimates are based on current interim action costs and additional vendor information.4 SVE system cost estimates are based on experience from past site operations and current estimates for SVE operations.5 Anticipated costs for permitting, engineering design, reporting, and construction oversight are assumed as 20% of the estimated source area remediation cost.

Abbreviations:

ERD Enhanced reductive dechlorinationIDC Indirect costLS Lump sum

SVE Soil vapor extractionYR Year

LTM Long term monitoringMNA Monitored natural attenuation


Contingencies

Quantity Unit Unit Cost 1Extended Cost 2,3 Detail

Contingency for Accelerated Cleanup (Install an additional 10 wells as low end of range)Site Survey/ Utility Locate 1 LS 2,344$ 2,400$ Well Installation and development 10 Well 32,000$ 320,000$ Assumes 4-inch diameter injection wells to be installed to depth of 190 feet;

wells are to be screened at multiple depth intervals to allow for injections to be completed throughout the well depth column.


IDW Management and Disposal (soil, Subtitle D) 10 Rolloffs 750$ 7,500$ Assume rental of roll-off container, transport and disposal at Subtitle D landfill.

IDW Management and Disposal (water) 1 LS 3,750$ 3,800$ Assumes frac tank and carbon treatment system rental, treatment and discharge to sanitary sewer.

In Situ Treatment 7 Event 37,141$ 260,000$ Treatment at 10 wells: 7 events twice in years 1,2 and once in yrs 3,4,5Treatment Performance Sampling 7 Event 6,641$ 46,500$ At 10 wellsPermitting/Oversight 1 LS $ 50,000 50,000$ Well Abandonment 10 Well $ 6,000 60,000$ Of the 10 wellsIDW Management and Disposal (soil, Subtitle D) 2 Rolloffs $ 750 1,500$ Subtotal for Contigency Accelerated Cleanup 818,000$

Contingency for Accelerated Cleanup (Install an additional 15 wells, upper end of range)Site Survey/ Utility Locate 1 LS 2,344$ 2,400$ Well Installation and development 15 Well 32,000$ 480,000$ Assumes 4-inch diameter injection wells to be installed to depth of 190 feet;

wells are to be screened at multiple depth intervals to allow for injections to be completed throughout the well depth column.


IDW Management and Disposal (soil, Subtitle D) 15 Rolloffs 750$ 11,250$ Assume rental of roll-off container, transport and disposal at Subtitle D landfill.

IDW Management and Disposal (water) 1 LS 4,550$ 4,600$ Assumes frac tank and carbon treatment system rental, treatment and discharge to sanitary sewer.

In Situ Treatment 7 Event 64,414$ 450,900$ Treatment at 15 wells: 7 events twice in yrs. 1,2 and once in yrs. 3,4,5Treatment Performance Sampling 7 Event 9,962$ 69,800$ At 15 wellsPermitting/Oversight 1 LS $ 50,000 50,000$ Well Abandonment 15 Well $ 6,000 90,000$ Of the 15 wellsIDW Management and Disposal (soil, Subtitle D) 3 Rolloffs $ 750 2,300$ Subtotal for Contigency Accelerated Cleanup 1,261,000$

Contingency for Wellhead Treatment at a new well Assumes City of Phoenix or other party installs well within the plume.

Wellhead Treatment (Construction 1 LS $ 550,000 $ 550,000Wellhead Treatment (O&M for 10 years) 1 LS $ 2,000,000 $ 2,000,000Compliance Monitoring 1 LS $ 75,000 $ 75,000Subtotal for Contingency Wellhead Treatment $ 2,625,000Notes:

1 All cost values are estimates and should not be interpreted as final construction or project costs. Costs are in present dollars and do not include inflation costs.2 Line item costs are rounded up to the nearest $100. Subtotal and total costs are rounded up to the nearest $1,000.3 Extended cost include costs for permitting, engineering design, and construction oversight, which are assumed as 25% of the unit cost.4 The wellhead treatement contingency could be applied to any of the alternatives.

03-07-17

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