Figure_6_-_RGE_Remediation_Status_Report_(Modified)_0002.pdf

New Mexico Arizona 8100 Wyoming Blvd., Albuquerque, NM 87113 T: (505) 344.2366

1921 S. Alma School Road Ste. 212, AZ 85210 T: (480) 834.5717

Monday, September 21, 2023

George Padilla, Regional Environmental Scientist Branch of Environmental Management Bureau of Indian Affairs-Navajo Region P.O. Box 1060 301 W. Hill Room 324 Gallup, NM 87305-1060 Phone: 505-863-8434 George.Padilla@bia.gov

Lynelle Benallie, Supervisory Contract Specialist BIA, Navajo Region, Acquisitions Phone: 505.863.8404 Lynelle.Benallie@bia.gov

RE: Submittal #13: Final Report for OU-1, OU-2, and OU-3

Rock Gap Engineering, LLC (RGE) is submitting the final bioremediation report for OU-1, OU-2 and OU-3.

In this report you will find a summary of all work completed along with recommendations and for future work still needing to be completed. This comprehensive report also includes all tests and supporting documents completed throughout the project.

There were three types of remediation required for this project with two types of remediation outstanding and will need to be completed in the future. Rock Gap Engineering, LLC., performed asbestos containing materials (ACM) remediation at OU-2 and OU-3, petroleum containing materials (PCM) remediation at OU-2 and groundwater remediation testing at OU-1, OU-2 and OU-3. During the course of remediation, RGE found additional work that would need to be completed outside the scope of work for each task. Through meetings with BIA, it was determined that OU-3 work be completed and OU-1 and OU-2 work be performed at a later date when more funding is available as outlined in Modification #4.

Respectfully, Tasha Preston, Intern Architect tashap@rockgap.com 8100 Wyoming Blvd.

Albuquerque, NM 87113

New Mexico Arizona 8100 Wyoming Blvd., Albuquerque, NM 87113 T: (505) 344.2366

1921 S. Alma School Road Ste. 212, AZ 85210 T: (480) 834.5717

Attachments:

2023-09-21-Remediation Status Report for OU-1, OU-2 and OU-3

CC:

Lynelle Benallie, CO Dalphianna Prettysongs, Assistant PM Keith Keetso, Principal

Rock Gap Engineering, Inc.

6759 Academy Road NE, Albuquerque, NM 87109 Tel (505) 344-2356 rockgap.com

Emergency Environmental Services, LLC 563 E Juanita Avenue, Mesa, AZ 85204 Tel (480) 809-4687 emergencyenv.com

Animas Environmental Services, LLC 624 E Comanche Street, Farmington, NM 87401 PO Box 8, Farmington, NM 87499 Tel (505) 564-2281 animasenvironmental.com

Remediation Status Report OU1 Former Tuba City Motors OU2 Tuba City Agency Heating Plant OU3 BIA Roads Maintenance Yard Solicitation #140A0921R0012; Contract 140A0921C0002

BIA Tuba City Remediation Status Report September [18], 2023; p. 1

Contents

1.0 Introduction

1.1 Location and Legal Description

2.0 Site Background

2.1 OU1, Former Tuba City Motors Property

2.2 OU2, Former BIA Heating Plant

2.3 OU3, BIA Road Maintenance Yard

3.0 2022 and 2023 Site Activities

3.1 OU1, Former Tuba City Motors

3.1.1 Groundwater Monitoring and Sampling by AES, June 2022

3.1.2 Iiná Bá Groundwater Monitoring and Sampling, May and November 2022

3.1.3 Bioremediation Recommendations

3.2 OU2, Tuba City Agency Heating Plant

3.2.1 Test Pits near Former Shed Location, June 2022

3.2.2 AES Groundwater Monitoring and Sampling, June 2022

3.2.3 Iiná Bá Groundwater Monitoring and Sampling, May and November 2022

3.2.4 OU2 Bioremediation Recommendations

3.3 OU3 - BIA Road Maintenance Facility

3.3.1 Groundwater Monitoring and Sampling by AES, June 2022

3.3.2 Excavation and Removal of Asbestos-Containing Soils, February-April 2023

3.3.3 Iiná Bá Groundwater Monitoring and Sampling, May and November 2022

3.3.4 OU3 Bioremediation Recommendations

4.0 Recommendations

5.0 References

Tables Table 1. OU3 Asbestos Waste Disposal Manifests

Figures Figure 1A. Topographic Site Location Map Figure 1B. Aerial Site Map Figure 2 OU1, Tuba City Motor Company Figure 3 OU2, Tuba City Agency Heating Plant Figure 4 OU3, Tuba City BIA Road Maintenance Facility Figure 5 OU3, Asbestos Excavation Areas

September [18], 2023; p. 2

Appendices OU3 Asbestos Waste Disposal Manifests OU3 Asbestos Air Monitoring Maps and JRM Asbestos Air Analytical Results OU3 SME Abatement Project Oversight and Air Monitoring Report, March 2023 OU3 Fiberquant Soil Analytical Reports

(7/30/2025 Manifest in separate file.)

7/30/2025 Appendices in separate file due to size.

September [18], 2023; p. 3

1.0 Introduction

Rock Gap Engineering (Rock Gap) has prepared this Remediation Status Report for the Bureau of Indian Affairs (BIA) Tuba City Remediation Project at Operational Units (OUs):

OU1, the Former Tuba City Motors Property; OU2, the Tuba City Agency Heating Plant;

and OU3, the BIA Road Maintenance Yard.

This report details the current groundwater conditions at the three OUs, using data from samples collected by Animas Environmental Services, LLC (AES), as well as data compiled from previous environmental reports submitted to BIA through 2022 by various contractors. Additionally, recommendations for further groundwater remediation efforts have been provided.

1.1 Location and Legal Description

The three OUs are located to the east and west of Oak Street, to the south of Birch Street, in Tuba City, Coconino County, Arizona. The site is in Section 29, Township 32N, Range 11E. The latitude and longitude of the center point of each OU is given below:

OU1: 36.13333697628487, -111.23885066630793

OU2: 36.13171441738949, -111.23891772153956

OU3: 36.13200037145465, -111.23805941470407

A Topographic Site Location Map is included as Figure 1A, and an Aerial Site Map is included as Figure 1B.

2.0 Site Background

The history of environmental investigation and remediation activities conducted at the three OUs is summarized in the following sections.

2.1 OU1, Former Tuba City Motors Property

A release of gasoline and/or diesel fuel from an underground storage tank (UST) system was discovered in the late 1990s or early 2000s (Terranext, 2012).

In 2001, Iiná Bá, Inc. (Iiná Bá) performed a subsurface investigation which included the installation of at least seven monitor wells (Terranext, 2012).

September [18], 2023; p. 4

2011, Terranext installed 10 soil borings and collected 20 soil samples at depths ranging from 4 to 12 feet (ft) below ground surface (bgs). Samples were analyzed for total petroleum hydrocarbons (TPH) gasoline-range organics (GRO), diesel-range organics (DRO), motor oil-range organics (MRO), and benzene, toluene, ethylbenzene, and total xylenes (BTEX) (Terranext, 2012).

In 2016, approximately 1,760 cubic yards (CY) of petroleum-impacted soil was excavated from OU1 and transported for offsite for disposal by Rock Gap Construction, subcontractor for EW Wells Group, LLC (EW Wells) (BIA, 2021).

The majority of impacted soils in OU1 was encountered at depths of 5 to 10 feet bgs which extended to bedrock interface. The base of the excavation was backfilled with processed gravel, which was covered with non- impacted shallow site soils and other imported soils. A buried infiltration gallery was installed to allow for injection of bioremediation products into shallow groundwater.

Residual soil impacts remained at the base of the excavation (bedrock interface), as well as inaccessible areas including a water line and building (EW Wells, 2017).

OU1 is shown on Figure 2.

OU1 Excavation Area and Remediation Infiltration Gallery Piping, EW Wells (April 2017)

September [18], 2023; p. 5

2.2 OU2, Former BIA Heating Plant

In the past, heating oil was used as the fuel source for the steam plant machinery and equipment within the former the Tuba City Agency Heating Plant. Product was stored on-site in two 50,000-gallon above ground storage tanks (ASTs) adjacent to Building 193

(BIA, 2021).

In 1999, an explosion in one of the on-line boilers resulted in the release of an unknown quantity of heating oil at OU2. A subsurface investigation was performed by Geotechnical and Environmental Consultants (Terranext, 2012) and included the installation of 39 groundwater monitor wells and 11 extraction wells (BIA, 2021). OU2 is shown on Figure 3.

In 2011, Terranext installed 10 soil borings in OU2 and collected 20 soil samples at depths ranging from 4 to 12 ft bgs. Samples were analyzed for TPH GRO, DRO, MRO, and BTEX (Terranext, 2012).

In 2015 and 2016, approximately 7,500 CY of petroleum impacted soils were excavated from OU2 and transported for disposal by RGE. Most of the impacted soils were encountered at depths of 5 feet or more. Impacted soils were excavated down to bedrock interface (10 to 12 feet bgs), and the base of the excavation was backfilled with an approximately 2-foot bed of processed gravel.

Several lengths of perforated pipes were laid on the gravel to provide for option future injections of bio amendment fluids. Residual petroleum impacted soils remain at the base of the excavation, as well as in some perimeter and inaccessible areas, such as below a sewer line and tool shed. The excavated area above the gravel was filled with original overburden non-impacted shallow site soils and soils imported from off site.

In 2019, the tool shed was removed (Wells, 2017).

September [18], 2023; p. 6

OU2

Excavation Area and Remediation Infiltration Gallery Piping, EW Wells (April 2017)

2.3 OU3, BIA Road Maintenance Yard

The BIA Road Maintenance Yard is developed with Office Building #199, Supply Building #314 and a Storage Barn, which stores heavy equipment and is currently fenced. This facility provided centrally located equipment storage for road construction. OU3 is shown on Figure 4.

Terranext performed a site investigation in 2008-2010, which concluded that benzene was present in groundwater at concentrations exceeding the U.S. Environmental Protection Agency (USEPA) Preliminary Remediation Goal (PRG) of 0.35 micrograms per liter (µg/L). A groundwater gradient of 0.02 feet per foot (ft/ft) to the southeast was determined. No detectable soil contamination or non-aqueous phase liquid (NAPL) were reported (Terranext, 2012).

In June 2018, Cherokee CRC, LLC (CCRC) and Envirotech, Inc. (Envirotech) excavated approximately 2,808 CY of petroleum contaminated soil (PCS) from approximately 9 to 12 ft bgs in the parking lot of OU3. During this excavation, suspected asbestos-

September [18], 2023; p. 7 containing materials (ACM) were discovered in the overburden stockpile that was created during the PCS excavation. Work was stopped and the suspected ACM was investigated. The source was determined to be a former burn pit, and sample analysis confirmed that ACM was present. Envirotech removed a total of 6,440 CY of asbestos-contaminated soils (ACS) from the overburden stockpile. It was noted at the time of this work that additional ACM and ACS remained in-place at OU3.

3.0 2022 and 2023 Site Activities

3.1 OU1, Former Tuba City Motors

3.1.1 Groundwater Monitoring and Sampling by AES, June 2022

On June 23, 2022, AES collected one groundwater sample from Well MW-311, which was submitted to Hall Environmental Analysis Laboratory of Albuquerque, New Mexico (Hall) to be analyzed for total/dissolved iron and manganese per USEPA Method 200.7, sulfate and nitrate per USEPA Method 300.0, biological oxygen demand (BOD) per SM 5210B, and chemical oxygen demand (COD) per Method 410.4. These analytical results were intended to inform the development of a groundwater remediation strategy. The Hall analytical results were presented in the August 31, 2022 Soils Report: Tuba City OU2

(EES, 2022).

3.1.2 Iiná Bá Groundwater Monitoring and Sampling, May and November

Iiná Bá conducted groundwater monitoring and sampling across the combined site in May and November 2022 under a separate BIA contract. This discussion for OU1 is excerpted from the Draft Fourth Semi-Annual Groundwater Monitoring and Sampling Event Report (Iiná Bá, 2022):

The only detection of petroleum in groundwater at or near this OU remains to be in monitoring well MW-302 along Oak Street off the eastern side of the subject area. The minor impacts appear to be more gasoline like than fuel oil like, with none of the analytical parameters exceeding the NNEPA Water Cleanup Standards.

September [18], 2023; p. 8

OU1 Dissolved Total BTEX (left) and Naphthalene (right), November 2022 (Iiná Bá)

3.1.3 Bioremediation Recommendations

To address residual dissolved-phase concentrations in MW-302, advance direct push chemical injections into shallow soils and groundwater in 5 points surrounding the well.

Several different chemicals can be considered for injection. Hydrogen peroxide, diluted to a safe concentration, would provide a chemical oxidation reaction that would quickly reduce contaminant concentrations. If a more natural injection product is preferred, the Regenesis product PetroFix is made from natural sources of carbon (such as coconut husks) and would produce a slower, biologically mediated reduction in dissolved-phase contamination.

3.2 OU2, Tuba City Agency Heating Plant

3.2.1 Test Pits near Former Shed Location, June 2022

EES and AES provided a soil sampling plan to BIA and NNEPA that was intended to determine the volume of PCS remaining beneath the shed that was removed in 2019.

The original estimate of remaining impacted soil was approximately 500 CY.

On June 21, 2022, EES and AES excavated 21 test pits in OU2, near the former Tuba City Agency Heating Plant. The purpose of the test pits was to delineate the area of impacted soils surrounding the former location of a shed. EES excavated the test pits using a backhoe, and AES took measurements of volatile organic compounds (VOCs) using a photoionization detector (PID) organic vapor meter (OVM). AES also collected grab soil samples from approximately 4 and 8 ft below ground surface (bgs) from pits near the edges of the predetermined delineation area.

Previous reports have described the geology at the site as consisting of primarily overburden soils comprised of sandy silts and clayey silts, which are transitional both laterally and vertically in various locations, with lenses of silty fine sands. These soils extend to depths of between approximately 10 to 15 feet below ground, at which point

September [18], 2023; p. 9 bedrock is encountered (EW Wells, 2017). Bedrock has been identified as silty sandstones and mudstones, part of the Moenkopi Formation (Petersen & Pipiringos, 1979). AES field notes from the June 2022 soil sampling event confirms these descriptions, with fine-grained sands ranging in color from red at shallow depths to black and brown at deeper locations. Groundwater was encountered near the bottom of the test pits, at approximately 7 to 8 ft bgs.

PID-OVM headspace readings from the soil samples ranged from non-detect to 1,093 parts per million (ppm). Soil samples were submitted to Hall Analytical Environmental Laboratory (Hall), Albuquerque, New Mexico, and analyzed for total petroleum hydrocarbons (TPH) gasoline range organics (GRO), diesel range organics (DRO), and motor oil range organics (ORO) per U.S. Environmental Protection Agency (USEPA) Method 8015 M/D. Test pit locations, PID-OVM readings, and the proposed extents of excavation were previously presented to BIA (EES, 2022).

Laboratory analytical results demonstrated that 10 of 12 perimeter sampling locations had TPH concentrations below the NNEPA Soil Cleanup Standards (SCSs) for the three TPH ranges of 500 milligrams per kilogram (mg/kg). Two sampling locations, SB-8 and SB-9, had exceedances of the 500 mg/kg standard for TPH-DRO, with concentrations at SB-8 of 1,300 mg/kg at 4 ft bgs and 4,600 mg/kg at 8 ft bgs and 9,000 mg/kg at SB-9 from 8 ft bgs. There were no exceedances of the NNEPA SCSs for TPH-GRO or TPH-ORO.

Additionally, AES collected one waste characterization sample from Test Pit 5, which was placed directly under the former shed. This sample was analyzed for TPH (GRO/DRO/ORO) per USEPA Method 8015 M/D, soluble cations and sodium adsorption ratio per USEPA Method 6010B, and resistivity and electrical conductivity per the American Society of Agronomy method as described in Methods of Soil Analysis:

Chemical and Microbiological Properties (1982). This sample was intended to be used to generate a waste profile for excavated soils.

Test pit excavation samples indicate that the remaining area of contaminated soil measures approximately 100 feet (ft) wide by 60 ft long by 8 ft deep. The revised estimated volume of soil that would need to be excavated was approximately 1,800 CY, including the 500 CY from the original proposal.

These results were presented in the August 31, 2022 document Soils Report: Tuba City

OU2 (EES, 2022).

3.2.2 AES Groundwater Monitoring and Sampling, June 2022

On June 23, 2022, AES collected one groundwater sample from Well MW-307, which was submitted to Hall to be analyzed for total/dissolved iron and manganese per USEPA Method 200.7, sulfate and nitrate per USEPA Method 300.0, BOD per SM 5210B, and COD per Method 410.4. These analytical results were intended to inform the

September [18], 2023; p. 10 development of a groundwater remediation strategy. The Hall analytical results were presented in the August 31, 2022 Soils Report: Tuba City OU2 (EES, 2022).

3.2.3 Iiná Bá Groundwater Monitoring and Sampling, May and November Iiná Bá conducted groundwater monitoring and sampling across the combined site in May and November 2022 under a separate BIA contract. This discussion for OU2 is excerpted from the Draft Fourth Semi-Annual Groundwater Monitoring and Sampling Event Report (Iiná Bá, 2022):

This unit still contains a plume that is oriented from the northwest to the southeast along the prevailing groundwater flow direction. The plume is centered around the east-central portion of the unit. The plume crosses Oak Street and is present within the western limits of OU-3 near its southern boundary. There are isolated occurrences of impact along the southern boundary as well as two occurrences of NAPL (very southeastern corner at MW-227 and offsite south of OU-3 at MW-20).

September [18], 2023; p. 11

OU2 Dissolved Total BTEX (left) and Naphthalene (right), November 2022 (Iiná Bá)

Based on a review of available dissolved phase concentration data from Iiná Bá, it appears that there are two monitor wells with residual concentrations slightly above applicable standards:

MW-1: 7 µg/L methyl tert-butyl ether (MTBE) and 8 µg/L naphthalene; and, MW-307: 11 µg/L naphthalene.

One well, MW-227, is located at the southeast corner of OU2 and has an unknown thickness of NAPL.

September [18], 2023; p. 12

3.2.4 OU2 Bioremediation Recommendations

Based on available site information, AES recommends the following to complete remediation of soil and groundwater within OU2:

1. Excavate approximately 1,800 cubic yards of PCS beneath and adjacent to the footprint of the former shed (removed in 2019). Transport and dispose of PCS at Contract Environmental Services Landfarm, near Aneth, Utah (CES).

2. While the excavation is open, and upon agency approval, treat the sides and bottom of the excavation with a remediation product to prevent the influx of TPH via contaminated groundwater into the clean backfill. AES recommends a product produced by Regenesis called PetroFix. PetroFix is a combination of micron‐scale activated carbon and the terminal electron acceptors (TEAs), sulfate and nitrate. When blended into a liquid and sprayed into the excavation, the activated carbon coats the soil particles and will adsorb hydrocarbons from the dissolved phase plume. The TEAs will stimulate hydrocarbon degradation by native soil bacteria, freeing the carbon to absorb more contaminants.

3. To address residual dissolved phase concentrations in MW-1 and MW-307, advance direct push chemical injections into shallow soils and groundwater in 5 points surrounding each well, for a total of 10 injection points. Several different chemicals can be considered for injection. Hydrogen peroxide, diluted to a safe concentration, would provide a chemical oxidation reaction that would quickly reduce contaminant concentrations. If a more natural injection product is preferred, the Regenesis product PetroFix is made from natural sources of carbon (such as coconut husks) and would produce a slower, biologically-mediated reduction in dissolved-phase contamination.

4. Measure NAPL in MW-227 (southeast corner of OU2). Depending on thickness of NAPL and depth of well, install either a passive skimmer or an absorbent oleophilic/hydrophobic sock to collect residual product.

September [18], 2023; p. 13

3.3 OU3 - BIA Road Maintenance Facility

3.3.1 Groundwater Monitoring and Sampling by AES, June 2022

On June 23, 2022, AES collected one groundwater sample from Well RMF-MW-4, which was submitted to Hall to be analyzed for total/dissolved iron and manganese per USEPA Method 200.7, sulfate and nitrate per USEPA Method 300.0, BOD per SM 5210B, and COD per Method 410.4. These analytical results were intended to inform the development of a groundwater remediation strategy. The Hall analytical results were presented in the August 31, 2022 Soils Report: Tuba City OU2 (EES, 2022).

3.3.2 Excavation and Removal of Asbestos-Containing Soils, February-April

Based on the results of the Asbestos Soils Report (EES, 2022), EES excavated three areas of the parking lot at the BIA Road Maintenance Facility (OU3) that were impacted with ACM and/or ACS. Prior to starting excavation activities, EES installed construction fencing and barricades to isolate the excavation area. Warning tape and signs were used to alert workers and the general public to the presence of asbestos. Traffic control measures to guide truck traffic flow were placed in accordance with the Site Traffic Control Plan. Air monitors were placed downwind of excavation and loading activities along the fenceline and near excavation equipment to collect air samples for asbestos analysis.

EES excavated the three identified areas on the following days:

Area 1: February 7 and 8 and March 6-9, 2023 Area 2: March 13, 14, and 27-29, 2023 Area 3: April 4 and 5 and July, 2023

The excavated areas are presented on Figure 5.

During all excavation and loading activities, amended water was applied to excavated soils to reduce the release of dust and fibers. Excavated soils were direct-loaded into 20-CY dump trucks, which were lined with double layers of 6-mil poly sheeting before soils were loaded. Prior to transport, the poly sheeting was burrito-wrapped around the soils and the entire load was tarped before leaving the excavation work area. ACM-impacted soils were transported to CES. The following table summarizes the volumes of soils that were removed; a full table detailing all loads transported is included as Table 1.

September [18], 2023; p. 14

OU3 Excavation and Disposal Summary of Asbestos Containing Soils

Area Start Date End Date Total Volume Disposed of at CES Landfarm (CY) 1 2/7/2023 3/10/2023 1,044 2 3/13/2023 3/31/2023 810 3 4/5/2023 7/21/2023 922 Total 2,776

A total of 2,776 CY of ACM/ACS was removed for disposal. The waste manifests are included in the Appendix.

The air samples collected during excavation and loading activities were submitted to JRM Environmental of Scottsdale, Arizona (JRM) for asbestos analysis via phase contrast microscopy (PCM) per National Institute of Occupational Safety and Health (NIOSH) Method 7400. All analytical results for air monitoring samples indicated that airborne fibers did not exceed the Occupational Safety and Health Administration (OSHA) and NIOSH regulatory limits of 0.1 fibers per cubic centimeter (f/cc). As a secondary confirmation of project safety controls, EES hired Sevee and Maher Engineers of Phoenix, Arizona (SME) to prepare an Abatement Project Oversight and Air Monitoring Report (SME, 2023). In their report dated March 22, 2023, SME concluded that “the abatement work by EES was conducted in general accordance with EPA/Asbestos- NESHAP requirements”. SME collected four air samples which were analyzed via PCM per NIOSH Method 7400. These air samples confirmed that airborne fibers did not exceed the OSHA and NIOSH regulatory limits of 0.1 f/cc. The JRM analytical reports and SME report are included in the Appendix.

When the excavations were complete, EES collected one 5-point composite sample from each area to confirm that all asbestos-impacted soils had been removed. The three confirmation samples were transported to Fiberquant Analytical Services of Phoenix, Arizona for quantification of asbestos in soil via polarized light microscopy per USEPA Method 600/R-93/116. No asbestos were detected in any of the confirmation samples.

The Fiberquant analytical reports are included in the Appendix.

3.3.3 Iiná Bá Groundwater Monitoring and Sampling, May and November

OU3 discussion is excerpted from the Draft Fourth Semi-Annual Groundwater Monitoring and Sampling Event Report (Iiná Bá, 2022):

Besides the naphthalene emanating upgradient from OU-2 along its southwestern limits, there is a small naphthalene plume along the eastern limits of this unit that slightly crosses First Street.

September [18], 2023; p. 15

Based on a review of available dissolved phase concentration data from Iiná Bá, it appears that there are five monitor wells with residual concentrations slightly above applicable standards:

RMF-MW-2: 83 µg/L naphthalene (May 2022); well damaged in November 2022;

MW-211: 10 µg/L naphthalene (May 2022); well damaged in November 2022;

MW-235: 15 µg/L naphthalene (May 2022);

MW-237: 12 µg/L naphthalene (May 2022); well damaged in November 2022;

and, MW-239: 10 µg/L naphthalene (November 2022).

One well, MW-20, is located at the south of OU3 and has an unknown thickness of

NAPL.

OU3 Dissolved Total BTEX, November 2022 (Iiná Bá)

September [18], 2023; p. 16

OU3 Dissolved Naphthalene, November 2022 (Iiná Bá)

3.3.4 OU3 Bioremediation Recommendations

Based on available site information, AES recommends the following to complete remediation of petroleum contaminated soil and groundwater within OU3:

1. To address residual dissolved phase concentrations in RMF-MW-2, MW-211, MW-235, MW-237, and MW-239, advance direct push chemical injections into shallow soils and groundwater in 5 points surrounding each well, for a total of 25 injection points. These wells are not located within the area of the existing OU3 infiltration gallery, so direct injections are the most effective way to treat residual contaminant impacts in shallow groundwater. As discussed previously, either hydrogen peroxide or PetroFix would be appropriate injection chemicals.

2. Measure NAPL in MW-20 (south of OU3). Depending on thickness of NAPL and depth of well, install either a passive skimmer or an absorbent oleophilic/hydrophobic sock to collect residual product.

September [18], 2023; p. 17

4.0 Recommendations

Bioremediation applications appear to have been effective in site remediation efforts, and additional applications should be further effective in treating residual areas of contaminant impacts which remain outside the existing infiltration galleries. Several different chemicals can be considered for injection. Hydrogen peroxide, diluted to a safe concentration, would provide a chemical oxidation reaction that would quickly reduce contaminant concentrations. If a more natural injection product is preferred, the Regenesis product PetroFix is made from natural sources of carbon (such as coconut husks) and would produce a slower, biologically-mediated reduction in dissolved-phase contamination.

OU1: To address residual dissolved-phase concentrations in MW-302, advance direct push chemical injections into shallow soils and groundwater in 5 points surrounding the well. See Section 3.1.3 for more detail.

OU2: Based on available site information, AES recommends:

o Advance direct push chemical injections into shallow soils and groundwater in 5 points surrounding MW-1 and MW-307, for a total of 10 injection points. See Section 3.2.4 for more detail.

o Measure NAPL in MW-227 (southeast corner of OU2). Depending on thickness of NAPL and depth of well, install either a passive skimmer or an absorbent oleophilic/hydrophobic sock to collect residual product.

o The removal of the NAPL layer on groundwater at monitoring wells MW- 227 and MW-20 should be performed to eliminate this condition as a source of possible dissolved-phase impacts to local groundwater;

o Excavate approximately 1,800 cubic yards of PCS beneath and adjacent to the footprint of the former shed (removed in 2019).

o While the excavation is open, treat the sides and bottom of excavation with a remediation product to prevent the influx of TPH via contaminated groundwater into the clean backfill.

OU3: To address residual dissolved phase concentrations:

o Advance direct push chemical injections at RMF-MW-2, MW-211, MW- 235, MW-237, and MW-239 into shallow soils and groundwater in 5 points surrounding each well, for a total of 25 injection points.

o Measure NAPL in MW-20 (south of OU3). Depending on thickness of NAPL and depth of well, install either a passive skimmer or an absorbent oleophilic/hydrophobic sock to collect residual product. See Section 3.3.4 for more detail.

September [18], 2023; p. 18

Begin to consider reducing the footprint of the existing, long-term groundwater monitoring well network by: 1) plugging and abandoning those groundwater monitoring wells with a history of being dry to eliminate these locations from being a liability (direct conduit to the water table); and 2) then further reduce the number of monitoring wells no longer needed to monitor plume migration, reduction, or degradation. Based on the most recent monitoring report along with historic reports, the following 40 monitor wells should be considered for plugging and abandonment (i.e. wells that are either dry or have had at least 8 consecutive sampling events with concentrations below applicable standards):

Monitor Wells Proposed for Plugging and Abandonment

MW-8 MW-34* MW-208 MW-225 MW-239

MW-12 MW-201 MW-210 (dry) MW-226 MW-301

MW-15 MW-202 MW-211* MW-229 MW-303

MW-24 MW-203 MW-212* MW-230 MW-305

MW-26 MW-204 MW-214 MW-232 MW-306

MW-28 MW-205 MW-215 MW-233* MW-309

MW-32 MW-206 MW-220* MW-234 (dry) MW-310

MW-33* MW-207 MW-222* MW-238 MW-311

Note: this is a preliminary list only; monitoring reports do not have full cumulative data reported. This list has been assembled by comparing various historic reports.

* Well damaged.

All remaining flush-mount groundwater monitoring wells along Oak Street and First Street should be evaluated for existing conditions and markers or barricades of some sort need to be erected to prevent any more wells from becoming damaged or destroyed. All monitor wells should have general routine maintenance performed to maintain their integrity, including locks for security and painting of protective covers/housings.

September [18], 2023; p. 19

5.0 References

BIA. (2021). Scope of Work, OU-1 former Tuba City Motors Property, OU-2 Tuba City Agency Heating Plant, OU-3 BIA Roads Maintenance Yard, Bioremediation and Waste Removals. Tuba City, Arizona: Bureau of Indian Affairs, Western Navajo Agency.

EES. (2022). Asbsestos Soils Report, Tuba City OU2 & OUe. Farmington NM: Emergency Environmental Services LLC.

EES. (2022). Soils Report, Tuba City OU2. Farmington NM: Emergency Environmental Services LLC.

EW Wells. (2017). Groundwater Bioamendment Injection Final Workplan: Operational Units No. 1 and 2. Albuquerque, New Mexico: EW Wells Group, LLC.

EW Wells. (2017). Groundwater Bioamendment Program Report For Operable Units OU- 1 and OU-2. Albuquerque, New Mexico: E W Wells Group, LLC.

Iiná Bá. (2022). Draft Fourth Semi-Annual Groundwater Monitoring and Sampling Event Report, BIA OU1, OU2 and OU3, Tuba City, Coconino County, Arizona.

Petersen, F., & Pipiringos, G. (1979). Stratigraphic Relationships of the Navajo Sandstone to Middle Jurassic Formations in Parts of Southern Utah and Northern Arizona. In U. G. Survey, Unconformities, Correlations, and Nomenclature of Some Triassic and Jurassic Rocks, Western Interior United States. Washington, DC: Professional Paper 1035-B.

SME. (2023). Abatement Project Oversight and Air Monitoring. Phoenix AZ: Sevee & Maher Engineers.

Terranext. (2012). Petroleum Hydrocarbon Release Report, P.O. No. A11PD00042.

Tempe, Arizona: Terranext, LLC.

Tables

September [18], 2023; p. 1

Table 1.

OU3 Asbestos Waste Disposal Manifests

Date Time Manifest No. Area Volume (CY)

2/7/2023 15:20 15248 1 18 2/7/2023 16:40 1 18 2/8/2023 14:15 1 18 2/8/2023 14:55 1 18 2/8/2023 16:00 1 18 2/9/2023 11:20 17126 1 18 2/9/2023 13:00 17128 1 18 2/9/2023 14:00 17129 1 18 2/9/2023 14:30 17127 1 18 2/9/2023 14:30 17130 1 18

2/10/2023 8:35 17131 1 18 2/10/2023 13:15 17132 1 18 2/10/2023 13:45 17133 1 18 2/10/2023 14:30 17134 1 18 2/20/2023 15:30 17135 1 18 2/20/2023 16:05 17136 1 18 2/21/2023 8:15 17137 1 18 2/21/2023 8:45 17138 1 18 2/21/2023 12:00 17139 1 18 2/21/2023 12:30 17140 1 18 2/21/2023 15:50 17141 1 18 2/22/2023 7:00 17144 1 18 2/22/2023 7:50 17143 1 18 2/22/2023 9:15 17142 1 18 3/6/2023 14:30 17145 1 18 3/6/2023 14:45 17146 1 18 3/6/2023 15:35 17147 1 18 3/6/2023 15:40 17148 1 18 3/7/2023 8:45 17149 1 18

16490 16491 16480 16492

September [18], 2023; p. 2

Date Time Manifest No. Area Volume (CY)

3/7/2023 8:45 17152 1 18 3/7/2023 11:15 17150 1 18 3/7/2023 12:15 17151 1 18 3/7/2023 13:00 17153 1 18 3/7/2023 16:50 17154 1 18 3/8/2023 8:45 17155 1 18 3/8/2023 8:45 17156 1 18 3/8/2023 12:30 17158 1 18 3/8/2023 12:45 17157 1 18 3/8/2023 16:05 17159 1 18 3/8/2023 16:45 17161 1 18 3/8/2023 16:50 17162 1 18 3/8/2023 17:00 17163 1 18 3/9/2023 10:30 17160 1 18 3/9/2023 11:10 17166 1 18 3/9/2023 11:15 17164 1 18 3/9/2023 11:55 17165 1 18 3/9/2023 13:15 17167 1 18 3/9/2023 13:20 17168 1 18 3/9/2023 13:30 17169 1 18 3/9/2023 16:05 17170 1 18

3/10/2023 8:45 17172 1 18 3/10/2023 8:45 17174 1 18 3/10/2023 9:25 17171 1 18 3/10/2023 10:40 17173 1 18 3/10/2023 12:30 17175 1 18 3/10/2023 13:00 17176 1 18 3/10/2023 13:05 17177 1 18 3/10/2023 13:45 17178 1 18

Subtotal, Area 1: 1,044

3/13/2023 13:40 17179 2 18 3/13/2023 14:00 17180 2 18

September [18], 2023; p. 3

Date Time Manifest No. Area Volume (CY)

3/13/2023 14:20 17181 2 18 3/13/2023 16:00 17183 2 18 3/13/2023 16:40 17182 2 18 3/14/2023 11:43 17185 2 18 3/14/2023 11:45 17184 2 18 3/14/2023 12:30 17186 2 18 3/14/2023 12:35 17187 2 18 3/14/2023 13:45 17189 2 18 3/14/2023 14:00 17188 2 18 3/15/2023 9:00 17190 2 18 3/15/2023 9:00 17191 2 18 3/15/2023 9:15 17192 2 18 3/15/2023 9:30 17193 2 18 3/15/2023 10:05 17194 2 18 3/27/2023 14:40 17196 2 18 3/27/2023 14:45 17197 2 18 3/27/2023 15:15 17198 2 18 3/27/2023 15:40 17199 2 18 3/28/2023 8:45 17200 2 18 3/28/2023 10:30 17195 2 18 3/28/2023 11:00 17201 2 18 3/28/2023 11:30 17204 2 18 3/28/2023 11:35 17202 2 18 3/28/2023 12:15 17203 2 18 3/28/2023 15:30 17205 2 18 3/29/2023 8:45 17206 2 18 3/29/2023 8:45 17207 2 18 3/29/2023 10:10 17209 2 18 3/29/2023 10:45 17210 2 18 3/29/2023 12:00 17208 2 18 3/29/2023 12:15 17211 2 18 3/29/2023 16:15 17212 2 18 3/29/2023 16:35 17213 2 18

September [18], 2023; p. 4

Date Time Manifest No. Area Volume (CY)

3/30/2023 8:45 17215 2 18 3/30/2023 8:45 17216 2 18 3/30/2023 8:45 17217 2 18 3/30/2023 9:30 17214 2 18 3/30/2023 14:30 17218 2 18 3/31/2023 9:15 17219 2 18 3/31/2023 11:15 17220 2 18 3/31/2023 12:20 17221 2 18 3/31/2023 13:00 17222 2 18 3/31/2023 16:00 17223 2 18

Subtotal, Area 2: 810

4/5/2023 12:35 17224 3 18 4/5/2023 15:00 17226 3 18 4/5/2023 15:05 17225 3 18 4/6/2023 8:45 17227 3 18 4/6/2023 10:15 17228 3 18 4/6/2023 13:50 17229 3 18 4/7/2023 8:45 17231 3 18 4/7/2023 8:45 17230 3 18 4/7/2023 11:20 17232 3 18 4/7/2023 15:40 17233 3 18

4/10/2023 15:45 17235 3 18 4/10/2023 15:45 17234 3 18 4/10/2023 17:00 17236 3 18 4/11/2023 8:45 17237 3 18 4/11/2023 9:30 17238 3 18 4/11/2023 11:45 17239 3 18 4/11/2023 12:00 17241 3 18 4/11/2023 12:55 17240 3 18 4/11/2023 16:15 17242 3 18 4/12/2023 8:45 17245 3 18 4/12/2023 8:45 17244 3 18

September [18], 2023; p. 5

Date Time Manifest No. Area Volume (CY)

4/12/2023 8:45 17243 3 18 4/12/2023 11:05 17246 3 18 4/12/2023 12:45 17247 3 18 4/12/2023 15:45 17248 3 18 4/12/2023 17:15 17251 3 18 4/13/2023 8:40 17252 3 18 4/13/2023 8:40 17250 3 18 4/13/2023 8:40 17249 3 18 4/13/2023 11:40 17253 3 18 4/13/2023 11:45 17254 3 18 4/13/2023 16:05 17255 3 18 4/13/2023 17:20 17256 3 18 4/14/2023 8:45 17257 3 18 4/14/2023 9:45 17258 3 18 7/18/2023 8:35 16400 3 18 7/18/2023 13:00 16396 3 18 7/18/2023 16:00 16397 3 18 7/18/2023 16:00 16398 3 18 7/18/2023 16:00 16399 3 18 7/19/2023 12:15 17271 3 18 7/19/2023 12:30 17272 3 18 7/19/2023 14:45 17273 3 18 7/19/2023 16:00 17274 3 18 7/20/2023 11:30 17275 3 18 7/20/2023 13:00 17276 3 18 7/20/2023 13:00 17277 3 18 7/20/2023 14:15 17278 3 18 7/21/2023 8:30 17279 3 18 7/21/2023 9:00 17281 3 20 7/21/2023 11:55 17280 3 20

Subtotal, Area 3: 922

Figures

OU1

OU3

TUBA CITY SE QUADRANGLE

ARIZONA - COCONINO COUNTY

TUBA CITY QUADRANGLE

ARIZONA - COCONINO COUNTY

MOENAVE QUADRANGLE

ARIZONA - COCONINO COUNTY

N

DRAWN BY: DATE DRAWN:

CHECKED BY:

A. Todd

DATE CHECKED:

APPROVED BY:

E. McNally

DATE APPROVED:

REVISIONS BY: DATE REVISED:

C. Lameman

C. Lameman

TOPOGRAPHIC SITE LOCATION MAP

BUREAU OF INDIAN AFFAIRS

WASTE REMOVAL AND BIOREMEDIATION

OU1 FORMER TUBA CITY MOTORS

OU2 TUBA CITY AGENCY HEATING PLANT

OU3 BIA ROADS MAINTENANCE YARD

TUBA CITY, ARIZONA

FIGURE 1AApril 21, 2022

0 2,000

SCALE

(1 INCH = 2,000 FEET)

1,0002,000

August 24, 2023

August 24, 2023

August 24, 2023

LIBRARY

BIRCH AVE.

O

AK

S T.

PI

N

E

ST

M

AI

N S

T.

OU2

TUBA CITY AGENCY

HEATING PLANT

OU3

BIA ROAD

MAINTENANCE

FACILITY

OU1

TUBA CITY

MOTOR

COMPANY

FORMER OIL TANK

FORMER ASTs

FORMER

STEAM

PLANT

TUBA CITY MOTORS BUILDING

N

DRAWN BY: DATE DRAWN:

March 22, 2022

CHECKED BY:

A. Todd

DATE CHECKED:

APPROVED BY:

E. McNally

DATE APPROVED:

REVISIONS BY: DATE REVISED:

C. Lameman

C. Lameman

LEGEND

AERIAL SITE MAP

BUREAU OF INDIAN AFFAIRS

WASTE REMOVAL AND BIOREMEDIATION

OU1 FORMER TUBA CITY MOTORS

OU2 TUBA CITY AGENCY HEATING PLANT

OU3 BIA ROADS MAINTENANCE YARD

TUBA CITY, ARIZONA

FIGURE 1B

AERIAL SOURCE: © 2023 GOOGLE EARTH PRO, AERIAL DATE: APRIL 24, 2023.

August 24, 2023

August 24, 2023

August 24, 2023

TUBA CITY BIA PROJECT OPERABLE

UNIT (OU) BOUNDARY

GAS LINE

WATER LINE

SEWER LINE

STEAM LINES

ELECTRIC LINES (BURIED/OVERHEAD)

NOTE: UTILITIES ARE APPROXIMATE.

0 10050100

SCALE

(1 INCH = 100 FEET)

TUBA CITY AGENCY

HEATING PLANT

OU1

TUBA CITY

MOTOR

COMPANY

TUBA CITY MOTORS BUILDING

N

DRAWN BY: DATE DRAWN:

CHECKED BY:

A. Todd

DATE CHECKED:

APPROVED BY:

E. McNally

DATE APPROVED:

REVISIONS BY: DATE REVISED:

C. Lameman

C. Lameman

OU1 TUBA CITY MOTOR COMPANY

BUREAU OF INDIAN AFFAIRS

WASTE REMOVAL AND BIOREMEDIATION

OU1 FORMER TUBA CITY MOTORS

OU2 TUBA CITY AGENCY HEATING PLANT

OU3 BIA ROADS MAINTENANCE YARD

TUBA CITY, ARIZONA

FIGURE 2March 23, 2022

AERIAL SOURCE: © 2023 GOOGLE EARTH PRO, AERIAL DATE: APRIL 24, 2023.

August 24, 2023

August 24, 2023

August 24, 2023

LEGEND

TUBA CITY BIA PROJECT OPERABLE

UNIT (OU) BOUNDARY

GAS LINE

WATER LINE

SEWER LINE

STEAM LINES

NOTE: UTILITIES ARE APPROXIMATE.

ELECTRIC LINES (BURIED/OVERHEAD)

0 402040

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OU2

TUBA CITY AGENCY

HEATING PLANT

OU3

BIA ROAD

MAINTENANCE

FACILITY

FORMER OIL TANK

FORMER

ASTs

FORMER

STEAM

PLANT

TUBA CITY

MOTORS

BUILDING

LIBRARY

N 0 804080

SCALE

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DRAWN BY: DATE DRAWN:

CHECKED BY:

A. Todd

DATE CHECKED:

APPROVED BY:

E. McNally

DATE APPROVED:

REVISIONS BY: DATE REVISED:

C. Lameman

C. Lameman

OU2 TUBA CITY AGENCY HEATING PLANT

BUREAU OF INDIAN AFFAIRS

WASTE REMOVAL AND BIOREMEDIATION

OU1 FORMER TUBA CITY MOTORS

OU2 TUBA CITY AGENCY HEATING PLANT

OU3 BIA ROADS MAINTENANCE YARD

TUBA CITY, ARIZONA

FIGURE 3March 23, 2022

AERIAL SOURCE: © 2023 GOOGLE EARTH PRO, AERIAL DATE: APRIL 24, 2023.

August 24, 2023

August 24, 2023

August 24, 2023

LEGEND

TUBA CITY BIA PROJECT OPERABLE

UNIT (OU) BOUNDARY

GAS LINE

WATER LINE

SEWER LINE

STEAM LINES

NOTE: UTILITIES ARE APPROXIMATE.

ELECTRIC LINES (BURIED/OVERHEAD)

S T.

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TUBA CITY AGENCY

HEATING PLANT

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ASTs

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CHECKED BY:

A. Todd

DATE CHECKED:

APPROVED BY:

E. McNally

DATE APPROVED:

REVISIONS BY: DATE REVISED:

C. Lameman

C. Lameman

OU3 BIA ROAD MAINTENANCE FACILITY

BUREAU OF INDIAN AFFAIRS

WASTE REMOVAL AND BIOREMEDIATION

OU1 FORMER TUBA CITY MOTORS

OU2 TUBA CITY AGENCY HEATING PLANT

OU3 BIA ROADS MAINTENANCE YARD

TUBA CITY, ARIZONA

FIGURE 4March 23, 2022

AERIAL SOURCE: © 2023 GOOGLE EARTH PRO, AERIAL DATE: APRIL 24, 2023.

August 24, 2023

August 24, 2023

August 24, 2023

LEGEND

TUBA CITY BIA PROJECT OPERABLE

UNIT (OU) BOUNDARY

GAS LINE

WATER LINE

SEWER LINE

STEAM LINES

NOTE: UTILITIES ARE APPROXIMATE.

ELECTRIC LINES (BURIED/OVERHEAD)

S T.

PI

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OU2

TUBA CITY AGENCY

HEATING PLANT

OU3

BIA ROAD

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ASTs

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PLANT SAMPLE #001

SAMPLE #002

SAMPLE #003

1 4

N 0 804080

SCALE

(1 INCH = 80 FEET)

DRAWN BY: DATE DRAWN:

CHECKED BY:

A. Todd

DATE CHECKED:

APPROVED BY:

E. McNally

DATE APPROVED:

REVISIONS BY: DATE REVISED:

C. Lameman

C. Lameman

OU3 BIA ROAD MAINTENANCE FACILITY

ASBESTOS EXCAVATION AREAS

BUREAU OF INDIAN AFFAIRS

WASTE REMOVAL AND BIOREMEDIATION

OU1 FORMER TUBA CITY MOTORS

OU2 TUBA CITY AGENCY HEATING PLANT

OU3 BIA ROADS MAINTENANCE YARD

TUBA CITY, ARIZONA

FIGURE 5August 24, 2023

AERIAL SOURCE: © 2023 GOOGLE EARTH PRO, AERIAL DATE: APRIL 24, 2023.

August 24, 2023

August 24, 2023

August 24, 2023

LEGEND

TUBA CITY BIA PROJECT OPERABLE

UNIT (OU) BOUNDARY

GAS LINE

WATER LINE

SEWER LINE

STEAM LINES

NOTE: UTILITIES ARE APPROXIMATE.

ELECTRIC LINES (BURIED/OVERHEAD)

5-POINT COMPOSITE EXCAVATION

SAMPLE LABEL

SAMPLE POINTS FOR EXCAVATION

COMPOSITE SAMPLE

ASBESTOS EXCAVATION AREAS

Air Sampling 3/6- 3/9/23 Write a description for your map.

Legend

Air Monitor(North Fence Line)

Excavation Area

Fence Line

Navajo Nation Animal Shelter

OU-3

300 ft

N

N