SOW_TBC_Groundwater_MW_Closurer1.pdf

SCOPE OF WORK

Former Tuba City Motors Operable Unit (OU-1) Groundwater Monitoring Well Abandonment

Bureau of Indian Affairs, Western Navajo Agency Tuba City, Arizona

1.0 Introduction:

The Bureau of Indian Affairs (BIA), Navajo Region (NRO), Branch of Environmental Management (BEM), is seeking the services of a qualified and experienced environmental firm to conduct the proper closure and decommissioning of nine (9) groundwater monitoring wells associated with the former Tuba City Motors Leaking Underground Storage Tank (LUST) site.

The wells designated for abandonment within Operaable Unit (OU-1) include MW-15, MW-28, MW-32, MW-216, MW-301, MW-302, MW-303, MW-304, and MW-311.

Since 2004, the site has been under active remediation and monitoring, overseen by the United States Environmental Protection Agency (USEPA) Region 9 and the Navajo Nation Environmental Protection Agency (NNEPA). After two decades of environmental oversight, both agencies have determined the site is eligible for closure, contingent upon the proper abandonment of all monitoring wells associated with Tuba City Motors, Operable Unit 1 (OU-1).

1.1 Project Location:

The former Tuba City Motors site is situated at the intersection of Birch and Oak Streets in Tuba City, Coconino County, Arizona, within the Tuba City Headquarters area. The site is embedded in a mixed-use community that includes commercial establishments, a hospital, residential neighborhoods, and educational institutions. This proximity to sensitive receptors underscores the critical importance of ensuring environmental safety and regulatory compliance throughout the well abandonment process.

Given the site's geographic and environmental context, strict adherence to federal, tribal, and state regulations is essential to mitigate potential risks and prevent residual contamination. The closure activities must be executed with precision and care to protect public health and preserve the integrity of surrounding land and water resources.

1.2. Background:

The Tuba City Headquarters petroleum release site comprises three designated operable units:

Operable Unit 1 (OU-1): Former Tuba City Motors Operable Unit 2 (OU-2): Bureau of Indian Affairs (BIA) Heating Plant Operable Unit 3 (OU-3): Department of Transportation (DOT) Roads Maintenance Yard OU-1, located to the north and upgradient of OU-2 and OU-3, was the site of a former underground storage tank. As a result of petroleum contamination associated with this tank, OU- 1 was classified as a LUST case by USEPA.

Despite the distinct characteristics of each operable unit, the BIA NRO manages the release across all three units as a single, integrated remediation project to ensure cohesive planning, regulatory alignment, and effective environmental response.

In 1999, a boiler explosion occurred at the OU-2 heating plant which resulted in the release of an unknown amount of heating oil to the subsurface. Site investigation and cleanup activities were identified as part of the Tuba City Comprehensive Environmental Response Compensation Liability Act (CERCLA) site. Initial response to the release included installation of groundwater monitoring wells and removal of petroleum contaminated soil in the vicinity of OU-2. Methyl Tertiary Butyl Ether (MTBE) was detected in up gradient monitoring wells of OU-2 and since MTBE is not a constituent of heating oil; further investigation revealed an underground storage tank (UST) located within OU-1. The UST tank and its underground piping system were found to be leaking and determined to be a potential source of groundwater contamination. The UST at OU-1 was removed on July 12-13, 2004.

Over the years, BIA NRO has conducted significant remediation efforts at the Tuba City CERCLA site to include bioremediation injections and removal and disposal of petroleum-impacted soils from all three operable units. In addition, the BIA NRO has been monitoring the groundwater at the Tuba City CERLCA site since 1999. The most current semi-annual groundwater sampling event occurred in April 2025, and a summary of the analysis indicated non-detect for NNEPA water cleanup standards, USEPA MCL, or ADEQ Tier 1 Water Cleanup Standard for OU-1. Two (2) groundwater monitoring wells (MW-216 and MW-311) associated with OU-1 were reported as inaccessible and could not be sampled because they are either covered, destroyed, or damaged.

In May 2025, USEPA and NNEPA jointly determined that the Tuba City Motors LUST site, designated as EPA Site ID NAV-233, meets the criteria for site closure. As part of the closure process, all monitoring wells associated with OU-1 shall be identified, evaluated, and properly abandoned in accordance with applicable federal, tribal, and state regulations. Abandonment procedures must ensure protection of groundwater resources and compliance with environmental standards.

1.3 Geology

The subsurface geology at the former Tuba City Motors site is characterized primarily by sandy silts and clayey silts, which exhibit lateral and vertical transitions across the area. Interspersed within these sediments are lenses of silty fine sands, contributing to variable permeability. These unconsolidated soils extend to depths of approximately 10 to 15 feet below ground surface, where bedrock is encountered (Terranext, 2011; E.W. Wells Inc.).

Beneath the site lies the principal regional aquifer known as the N-Aquifer, composed of weakly cemented and variably permeable Navajo Sandstone. This formation serves as a critical groundwater resource for the region. In the vicinity of Tuba City, natural springs emerge along the geologic contact between the Navajo Sandstone and the underlying Kayenta Formation, notably in Pasture Canyon and Moenkopi Wash (Peterson et al., 1979).

Understanding the site's rock layers and aquifer characteristics is essential for ensuring that well abandonment procedures do not compromise groundwater integrity or facilitate contaminant migration into deeper formations.

Period of Performance: The period of performance shall be 180 days from the notice to proceed.

TASK I: Pre-Submittals Pre-work submittals shall be submitted to the Navajo Region BEM within 30 working days from the Notice to Proceed.

A. The Contractor shall provide a Health and Safety Plan (HASP) in accordance with 29 CFR

1910.120 to ensure the protection of workers, employers, and the public throughout the duration of the project.

a. The HASP shall include documentation for all required certifications and licensures of personnel assigned to the project.

b. The plan shall identify task-specific personnel protective equipment (PPE) for all tasks and provide procedures for proper usage. PPE shall be selected based on hazard assessment and conform to OSHA standards.

c. The plan shall address both physical and environmental hazards that may be encountered during site activities. There are known and potentially occurring environmental hazards including exposure to petroleum hydrocarbons, potentially explosive atmospheric conditions, and tripping/falling hazards, presence of heavy equipment, utility lines, biological hazards, chemical hazards, venomous insects, and snakes/spiders. Other known and potentially environmental hazards are asbestos, PCBs, lead-based paint, and mold.

B. The Contractor shall prepare a detailed Work Plan with Project Schedule for BIA NRO BEM to review and approve prior to commencement of work.

a. The work plan should document the proposed off-site disposal activities and certified landfill locations. Name and locations of any recycling facilities for any material deemed recyclable, along with documentation of their certification and compliance status.

b. The work plan shall include a traffic management plan, dust control strategies, and a public communication plan to inform and public who live in this area. This area is surrounded by businesses, a hospital, residential area and schools.

c. The work plan shall provide a complete listing of all sub-contractors involved in the project. Each subcontractor’s certifications, licensures, and qualifications shall be included.

TASK II - Work

I. The contractor shall furnish the necessary personnel, materials, equipment, services, and facilities to successfully perform the proper plugging and abandonment of the listed monitoring wells associated with OU-1 at the former Tuba City Motors LUST Site. Wells to be abandoned are MW-15, MW-28, MW-32, MW-216, MW-301, MW-302, MW-303, MW-304, and MW-311.

All abandonment activities shall be conducted in accordance with applicable federal, tribal, and state regulations.

II. The Contractor shall ensure that all well abandonment activities are conducted by qualified personnel using approved methods and materials to prevent future risks to groundwater quality, subsidence, or surface infiltration. Prior to initiating fieldwork, the Contractor shall notify and consult with the Navajo Nation Department of Water Resources (NN DWR) to determine and document the appropriate closure methodology for each monitoring well.

III. The Contractor shall also notify the Navajo Tribal Utility Authority (NTUA) to identify and verify the presence of any underground or overhead utilities within the designated work area.

Utility clearance must be obtained prior to any subsurface activity to ensure safety and prevent service disruption.

IV. The contractor shall be responsible for the accurate identification and physical location of all groundwater monitoring wells associated with OU-1. The use of a magnetometer is recommended to assist in locating buried or obscured well casings, particularly in areas where surface markers may be missing or degraded. Alternatively, manual locating methods may be employed as needed. Once located, each well shall be properly decommissioned.

V. The contractor shall remove and dispose of the well protector (flush mounted road box or steel casing protector, if present), the well cap, all sampling materials, remediation equipment (if present), and any other obstructions in the well in accordance with applicable regulations.

VI. Implement the agreed well abandonment method. To include removal of the upper portion of the riser/casing to below ground surface, adding sealing material in accordance with regulatory requirements.

VII. Complete a Retained Well/Borehole Closure Report.

TASK III- Reports

All reports are the property of the BIA.

A. All written deliverables shall be submitted in electronic draft format for the COR’s review and comments.

B. Final copies will be due within ten (10) working days after receipt of COR’s comments.

Final copies shall be submitted in two (2) final bound copies and two (2) electronic versions (one pdf and one MSWord). Other quantities and formats may be requested from the COR. BIA shall be the owner of all documents prepared by the Contractor. The Contractor shall not copyright or write protect any documents or utilize any data from the project without consent of the Government.

C. If reports are lost, the Contractor shall reissue copies at their expense.

D. At the conclusion of the period of performance, the final report shall summarize objectives achieved, significant issues, and any recommendations. The final report shall include any drawings associated with the site, and other pertinent data generated in the performance of the contract. Profiles and the manifest forms for disposed items at permitted landfills are to be included in the final report. The volume and weigh tickets of recycled materials.

E. All final reports shall be signed and stamped by a Professional Engineer or equivalent to certify the work was conducted in accordance with the Work Plan and in accordance with all applicable environmental federal regulations and construction standards.

F. All correspondence shall be protected and secured. It shall not be made available to the public or any other agency without the permission of the BIA NRO.

G. Other written and technical deliverables shall be submitted according to their schedules.

H. The Contractor shall submit a weekly report of progress and expenditures to the CO and COR. Report shall be submitted in an electronic pdf format. The contractor shall be available for meetings as directed by the CO or COR.

INSTRUCTIONS, CONDITIONS, AND NOTICES TO CONTRACTORS

Special Conditions

The contractor shall obtain all necessary drilling, and other use permits if required.

The contractor shall adhere to all applicable tribal laws and regulations and payment of the Navajo Nation Tribal and Arizona Gross Receipts.

The contractor is responsible for any utilities that are damaged during work and should repair them immediately at no cost to the Government. Any damage to grassed areas or concrete structures other than those directly affected by the project shall be repaired at the Contractor's expense.

All contact with the public, private or regulatory community shall be made through the BIA Navajo Region. No information may be released without the written consent of the BIA Navajo Region.

Requirements

Pre-work Conference

Reference Material

The contractor may review any previous report for the Tuba City CERCLA site available from

BIA NRO BEM.