Questions_Tuba_City_OU2_OU3_08252025_0002.pdf

140A0925R0003 Tuba City OU 2&3 Remediation

Question: Is there current groundwater data available for the site?

Two sampling events (December 2024 and April 2025) have been conducted by Eastern Shawnee Professional Services.

Question: When was the last groundwater sampling event performed (2022)?

Two sampling events (December 2024 and April 2025) have been conducted by Eastern Shawnee Professional Services.

Question: Are there 40 groundwater monitoring wells to be abandoned or 37?

According to the Two sampling events (December 2024 and April 2025) have been conducted by Eastern Shawnee Professional Services, (29) wells could not be sample during the field events.

Question: Is the well construction information readily available? (Will need to determine cost of abandonments) The wells installed are 2-4” in diameter and the top of the groundwater table 7-30 ft bgs with a bottom of 3-5 ft screen.

Question: Would the BIA require a groundwater sampling event to determine the current groundwater conditions? (Will be needed to determine the correct remediation strategy - bio versus chemical ox) Semi-annual monitoring should be performed.

Question: For soil samples to document completion of the excavation activities, what analytical methods are required?

The following are to be analyzed Gasoline Range Organics, Diesel Range Organics, Oil Range Organics, Benzene, Toluene, Ethylbenzene and Xylenes, Methyl tert-butyl ether, Polycyclic Aromatic Hydrocarbons.

Question: What jurisdiction/regulatory limits are being adhered to for this site?

The 500 ppm is the Navajo Nation Environmental Protection Agency standard cleanup goal for heating oil. The cleanup standards are located in the Navajo Nation Leaking Storage Tank Soil and Water Cleanup Standards (2012).

Questions relating to Solicitation No. 140A0925R0003 Tuba City OU1 OU2 OU3 Bio-Remediation

1. Could you please provide the unit of measure in the provided Price Schedule to enable accurate cost rates? CY, is stated in the price schedule. This is dependent of the amount to be excavated.

2. What quantities of Petrofix that is expected to be injected at OU-2 and OU-3?

Or provide a table listing the concentrations of petroleum contamination in order to estimate the amount of appropriate Petrofix product to order from Regenesis?

The wells installed are 2-4” in diameter and the top of the groundwater table 7-30 ft bgs with a bottom of 3-5 ft screen.

3. Is 500 ppm the target for cleaning up heating oil?

The 500 ppm is the Navajo Nation Environmental Protection Agency standard cleanup goal for heating oil. The cleanup standards are located in the Navajo Nation Leaking Storage Tank Soil and Water Cleanup Standards (2012).

4. What is the cleanup goal for TPH and other chemicals of concern?

If there is no cleanup goal within Navajo Nation Cleanup standards, use the USEPA Regional screening levels for cleanup.

5. Are benzene and methyl tertiary butyl ether (MTBE) chemical concerns?

They are regulated substances and if a given contaminant did not have a Navajo Nation Cleanup standard, concentrations are to be compared to the USEPA Regional Screening Levels for soil or water contamination.

6. Was there a baseline data collection for groundwater prior to the first bioremediation application that can be shared to determine concentrations of chemical of concern, which will assist with the upcoming bioremediation application?

The bioremediation project originally started with Operational Unit 1, which required the installation of groundwater monitoring wells. Prior no baseline data was available when this project started, until recently BIA through their contractor under a separate contract, has been collecting groundwater data for all three of the operational units.

7. Can you provide Figures 4 and 5 as the ones provided were not complete.

Figures 4 and 5 are attached.

8. The SOW states that 33 and 40 wells are to be plugged and abandoned, however, the Price Schedule states that 37 wells are to be removed, which is the correct number?

There are 29 wells to be removed.

9. Is the sewer line at OU-2 in the planned excavation area? If so, is it active or inactive? Does it need to be removed during the excavation process?

The waste line is owned by Bureau of Indian Education Facility Management. Contractor will have to blue stake and work with the BIE Facility Manager, possibly Navajo Tribal Utility Authority (NTUA).

10. To confirm, the planned excavation area at OU-2 is contaminated with TPH and ACM or just

TPH or just ACM? Yes

11. Can you provide a figure showing the plume and the isolated impacts of the two NAPL areas at

OU-2?

The south area of OU-2, BEM contractor conducted 6 events for the southern area that showed high amounts of NAPL at MW-20 and 227. The GW monitoring wells are outside of the OU-2 property.

12. What are the COCs for the site to be analyzed and monitored?

The following are to be analyze Gasoline Range Organics, Diesel Range Organics, Oil Range Organics, Benzene, Toluene, Ethylbenzene and Xylenes, Methyl tert-butyl ether, Polycyclic Aromatic Hydrocarbons.

13. Should the bidder assume the excavated contaminated soil will be managed by the awarded contractor? Yes

14. Should contractors assume the awarded contractor will manage aqueous waste generated from the groundwater sampling events? Yes

15. How many more monitor wells should be planned to be installed for groundwater assessment?

No, new GW monitoring wells should be necessary unless the areas of concern south of OU-2 demonstrates further assessment. This has to be demonstrated through sampling, possibly treating this area with bioremediation retrogensis. Currently, BEM has contractor Eastern Shawnee conducting ground water sampling, the potential contractor for this project can be contacted.

16. How many injection events should be conducted at both OU-2 and OU-3? Sampling data shows contamination at both OUs sites, the injections will be use to reduce or contain the contamination from heating oil, gas, and diesel. Sampling reports are available for review.

17. How many performance monitoring events should be conducted after each injection event and for how long?

Semi-annual monitoring should be performed by Eastern Shawnee, current monitoring contractor.

18. Can you provide information on the monitoring wells in the monitoring well network? Yes, information is available in the GW monitoring reports for guidance.

19. Are confirmation samples required before backfilling? Yes

20. Are the past monitoring Reports from the site able to be downloaded from the NN EPA or US

EPA?

No, 2025 monitoring reports are available from a different contractor.

21. Is there a UIC permit for the site the awarded contractor will use for the injection work?

No

22. Can BIA please provide recent and historical NAPL thicknesses and groundwater monitoring well sampling results?

Two monitoring events (December 2024 and April 2025) from Eastern Shawnee Professional Services, LLC

23. Can BIA provide drawings of recent and historical NAPL thickness contour maps and ground water monitoring well sampling results contour maps? Yes, information is available April 2025 sampling event.

24. Can BIA provide drawings of recent and historical NAPL thickness contour maps and ground water monitoring well sampling results contour maps? Yes, information is available April 2025 sampling event.

25. Does BIA expect the contractor to determine the quantities of bioremediation chemicals that will be introduced into the excavation and the injection points, or can BIA provide a quantity to use for bidding purposes? Yes

26. If the base of the excavation under the former shed indicates that there is significant NAPL remaining in the soil, can the contractor install horizontal piping so that additional bioremediation chemicals can more easily be introduced into the NAPL area in the future as needed? Yes

27. Please provide Figure 6 (which is referenced in the SOW) Figure 6 was provided 07/30/2025.

28. Please provide the following reports:

• Fourth Semi-Annual Groundwater Monitoring and Sampling Event Report (iina Ba’, 2022)

• Source report(s) for the figures provided

• Terranext site investigation report