Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
Tuba City Open Dump
EPA #: NND982400145
City: Tuba City
Congressional District: 03
Environmental Investigation at the Dump is complete. Evaluation of cleanup options has begun.
Please read the factsheet below for more information.
TCD - Factsheet 4_16.pdf
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Description and History
NPL Listing History
NPL Status: Not on the NPL
The Tuba City Dump (TCD) is located near Tuba City, Arizona. It is off of US Highway 160, about one mile east of the State Highway 264 junction. The site is on land under two jurisdictions and is approximately 30 acres, of which, 2 acres are in Navajo Nation and 28 acres on Hopi tribal lands. Originally, the landfill was entirely on Navajo Nation. However, with the resolution of the Bennett Freeze by US Courts, the tribal reservation boundary near the TCD was adjusted, and the TCD came to be located mostly on Hopi tribal lands.
The TCD was operated by the Bureau of Indian Affairs (BIA) from the 1950s until 1997. The site was a dumping area where local businesses, schools, agencies, and the public dumped waste. During this time, it was not regulated or supervised as a solid waste disposal site. The landfill received waste from the Tuba City area and, to a lesser extent, from the Moenkopi area. In addition, waste from other areas may have been disposed of at the TCD due to its unrestricted access and location along a major highway. The BIA periodically provided limited maintenance to the site by constructing and back filling trenches at the dump site. Disposed municipal waste was burned to ash that was mixed with soil and non-burnable wastes in the TCD.
Since the TCD was unmanned and unsecured during its operation, and since BIA did not keep formal records of what was dumped; Information about the disposed wastes is limited. The BIA closed the TCOD to additional waste disposal in 1997.
Today the dump waste is covered by one to four feet of clean soil, but the TCD was never closed permanently under landfill laws. The waste is distributed between two cells, and is between one foot and 15 feet thick.
Tribal residents recalled waste dumping and fires when the dump operated. Discarded iron and ceramic balls from a mill grinding machine were found at the TCD. These are not toxic or radioactive, but people wondered whether the TCD may contain uranium waste from the former Rare Metals uranium mill that was located four miles to the east of the TCD on Highway 160. In 2008, moderately elevated levels of uranium were found in very shallow groundwater immediately adjacent to the TCD, within about 100 feet of the west edge of the dump waste. The community asked whether the dump may have received uranium wastes and whether the TCD may threaten drinking water supplies.
Over the 13 years before 2010, many environmental studies were performed at and near the Dump by various parties, including the Hopi Tribe, Navajo Nation, U.S. Geologic Survey, BIA, and EPA. While useful, these studies were not comprehensive and were not conducted under a consistent strategy, and as a result, some studies reached differing conclusions.
To complete the understanding of the Site, in 2010 EPA and BIA signed an order requiring that BIA pay for and perform a remedial investigation and a feasibility study under the Superfund law, subject to EPA’s oversight and approval. The Superfund process considers previous studies, collects new information, and leads to selecting and performing a cleanup action. The remedial investigation is a comprehensive and detailed evaluation of the nature and extent of contamination, how or where it may be moving, and any health risks it may pose. The feasibility study identifies, evaluates, and compares cleanup alternatives.
The following is a summary of findings about contamination from the extensive remedial investigation, which is discussed in more detail in a later section:
- Drinking water from wells and springs is safe and is not affected by the Tuba City Dump (TCD);
- The water and soils in the Pasture Canyon area are not affected by the TCD;
- The TCD is primarily soil, debris, and ash from burning trash many years ago;
- Extensive investigation has revealed no uranium waste in the TCD, and uranium was not found in soils or wastes above background levels;
- No buried radioactive materials were found in areas around the TCD;
- Very shallow groundwater close to the west edge of the TCD has elevated uranium levels made possible by leaching of salts and other chemicals in the landfill; and
- The deeper groundwater is clean and is not affected by the TCD.
As mentioned, the TCD is not properly closed as a solid waste landfill and proper closure will be necessary to ensure the temporary soil cover does not erode and to prevent people from contacting the solid wastes in the long term. The landfill creates some leachate to shallow groundwater, although this groundwater impact is very limited in size and the groundwater does not significantly move away from the TCD. The feasibility study is considering alternatives that would limit infiltration of rainwater through the TCD and/or place a liner under the waste.
Who is Involved
The United States Environmental Protection Agency (U.S. EPA) and the BIA are working with the Hopi Tribe and Navajo Nation to investigate and address the contamination. Other federal agencies monitoring the investigation and closure of the site include:
- U.S. Geological Survey (USGS)
- Indian Health Service (IHS)
- Department of Energy (DOE)
Investigation and Cleanup Activities
As mentioned above, over the 13 years before 2010, many environmental studies were performed at and near the Dump by various parties, including the Hopi Tribe, Navajo Nation, U.S. Geologic Survey, BIA, and EPA. While useful, these studies were not comprehensive and were not conducted under a consistent strategy, and as a result, some studies reached differing conclusions.
To complete the understanding of the Site, in 2010 EPA and BIA signed an order requiring that BIA pay for and perform a remedial investigation and a feasibility study under the Superfund law, subject to EPA’s oversight and approval. The Superfund process considers previous studies, collects new information, and leads to selecting and performing a cleanup action.
The remedial investigation (RI) is a comprehensive and detailed evaluation of the nature and extent of contamination, how or where it may be moving, and any health risks it may pose. The feasibility study (FS) identifies, evaluates, and compares cleanup alternatives.
The remedial investigation for TCD was completed in 2015 and the feasibility study is planned for completion in the summer of 2016. Both the Navajo Nation and Hopi Tribe have been regularly involved with EPA and BIA in the planning, development, execution, and writing of the RI and the FS.
What Type of Work Was Performed During the Remedial Investigation?
To supplement studies done in the past, major additional work performed included:
- More than 360 borings and exploratory trenches into the TCD waste, as well as under and adjacent to the waste;
- Thousands of waste and soil samples looked for contamination at multiple depths; including tests for hundreds of different chemicals, including uranium and other radioactive substances;
- Scans for radioactivity from hundreds of cores in the TCD waste;
- Tests and surveys revealing the dump contents, waste thickness and locations;
- Thousands of samples from hundreds of boring holes at all depths in the sands and sediments downhill from the dump and in the Pasture Canyon;
- Installation, sampling, and groundwater testing at more than 70 monitoring wells in both the shallow and deep groundwater from east of the TCD to west of the Moenkopi water supply wells, and from southern Tuba City south to Moenkopi Wash;
- Many borings and cores deep into the ground that reveal the nature of the layers of rock under the ground that carry groundwater (aquifers);
- Many aquifer pumping tests that show where and how fast groundwater can move, and whether groundwater is able to move from near the TCD to drinking water wells;
- Surface radiological scans to look for buried waste; and
- Many other tests, sampling, modeling and procedures that were used to evaluate TCD contents, compare naturally- and non-naturally occurring uranium, calculate background levels, and provide other pertinent information.
What Did the Remedial Investigation Find?
The data and evaluations in the RI indicate that:
The drinking water from the Moenkopi supply wells and Tuba City wells is safe, and cannot be affected by the TCD.
- The data show that groundwater cannot flow from the Dump to the supply wells that lie west of Pasture Canyon, even when the supply wells are pumping.
The drinking water from the Moencopi Springs is safe, and cannot be affected by the TCD.
The data shows that the Moencopi Springs are fed by clean water from an aquifer that is deep under the ground. It is separate from the very shallow groundwater affected by the TCD. The data and modeling show that the shallow groundwater very near the dump does not travel to the Moencopi Springs.
What Is In The Dump?
Extensive investigation has shown no uranium-bearing mill waste in the TCD, and the groundwater chemistry indicates against mill waste being present.
- The investigation included samples, scans, analyses and tests from hundreds of soil and waste cores and trenches, and also a technically advanced study called isotopic ratio analysis. Uranium mill waste has not been observed, and none of the extensive investigation data indicate the presence of mill waste.
The dump is primarily composed of soil, ash, glass, brick, and burned municipal debris. These materials are not mobile and while the TCD needs to be properly closed, they do not pose a significant threat to the public.
- Levels of uranium and radioactivity in the TCD waste are similar to levels found naturally in soils in areas not near the TCD. Also, radioactivity scans more than a mile wide found no evidence of buried radioactive waste.
The TCD does not pose a health risk to people in its current state.
- The dump has an intact temporary cover of soil that prevents people from making contact with the waste. However, the TCD has not been closed in accordance with federal landfill laws to prevent long-term exposure to wastes.
Uranium levels in the very shallow groundwater right next to the TCD have uranium levels that are higher than usual.
- As rainwater has moved through the dump waste, the ash and other debris in the TCD has released ionic salts to the very shallow groundwater very near to the dump. These salts are commonly released from dumps in what is referred to as leachate. Their presence allows uranium present in rocks or soils to dissolve in the shallow groundwater more than normal.
While the TCD allows extra dissolving of uranium right next to the dump, there are other small areas of elevated uranium in shallow groundwater nearby that are not related to the TCD at all. This phenomenon is not uncommon in this immediate area and tends to be seen in shallow locations with previous ponding, in drainages, and in thinning or dense rock where water cannot easily flow.
- Groundwater affected by the TCD lies mostly within the dump fence line. Investigation shows that this groundwater stays very near the dump and does not migrate into the drainages or Pasture Canyon.
Water and sediments in Pasture Canyon are not affected by the TCD.
- The sands and sediments downhill from the TCD are not contaminated. Sampling and monitoring wells show that water affected by the TCD does not flow into Pasture Canyon.
The deeper aquifer (layer) of groundwater, which is most useful for drinking, is not contaminated.
- Groundwater in the shallower groundwater does not flow downward to the deeper groundwater. There is pressure in the deeper groundwater that pushes the groundwater upward. There is also a thick layer of tight rock that separates the shallow and deep groundwater.
What Kinds of Alternatives are Being Considered in the Feasibility Study?
The feasibility study report compares several cleanup alternatives for the TCD material. This report will be issued to the public soon. Cleanup alternatives for the TCD waste currently being considered are depicted generally in the table below. The feasibility study will also contain alternatives for the groundwater. The table is only an introduction to initiate discussion about the alternatives. The feasibility study and fact sheets EPA will issue in the future will provide more detail about the alternatives, their benefits and drawbacks, and their costs. No decision has been made yet on which alternative will be chosen for the TCD, for either the waste or the groundwater.
There are drawbacks as well as benefits to each of the alternatives considered. For instance, some alternatives would require larger amounts of scarce groundwater just to keep dust suppressed and to condition landfill covers, whereas some alternatives use less water. Similarly, some alternatives would place thousands of very large trucks on the highway, one truck every five minutes, for years. Others would produce less traffic or take less time to implement. Some alternatives would free up more land that the Hopi Tribe could use for other purposes, compared to other alternatives. And some alternatives would cost more than others. The feasibility study takes all these factors, and many more, into account when comparing the alternatives.
What Comes Next?
After the release of the feasibility study, EPA will hold additional public meetings with both tribal communities, with community leaders and tribal officials to discuss the cleanup alternatives and receive public input. We will also hold formal consultation sessions with the tribal governments. This is expected in fall 2016. In the late fall or early winter, EPA plans to open a formal public comment period on the cleanup options. EPA plans to formally select a cleanup alternative in late 2017. We anticipate that BIA will design and carry out the cleanup action. The design will require about 1-2 years to complete, and then the cleanup will take 1.5-2.5 years to complete.
Cleanup Results to Date
There has been no formal EPA cleanup action at the TCD. The process described here leads to the selection of a cleanup action during 2017 or early 2018.
Potentially Responsible Parties
Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.
The United States Bureau of Indian Affairs is currently taking the lead as PRP for ongoing work at the site.
Documents and Reports
Public Meetings: Both the Hopi Tribe and Navajo Nation representatives, contractors, and counsel have been regularly engaged with EPA and BIA during the remedial investigation and feasibility study process, and have regularly provided written and verbal input to the process and on drafts of plans and reports.
EPA has a Community Involvement Plan for the TCD site. This plan was based on direct input from residents and government as to how they prefer to receive information, and which methods of outreach are most effective. EPA has different strategies to meet the needs of the Hopi Tribe and Navajo Nation, as well as slightly different approaches for the Upper Village of Moenkopi and the Village of Lower Moencopi.
EPA has held many public meetings since the early 2000s, providing updates on progress on the TCD project, and issued many fact sheets to post all office boxes in the area.
In early May 2016, EPA held six public outreach meetings in three days, to describe EPA’s process, give an update on the project status, explain the results of the remedial investigation and lay out the characteristics of the cleanup alternatives that are under consideration. A corresponding fact sheet on all of these issues was also issued. Meetings were held for 1) Village of Upper Moenkopi, 2) Lower Moencopi,Village, 3) The To’Nanees’Dizi Navajo Chapter, 4) the Moenkopi Senior Center, 5) the Moenkopi Developers Corporation, and 6) the Hopi Tribal Council in Kykotsmovi.
EPA will be the lead in conducting community involvement activities throughout the remainder of the cleanup selection process.
Public Information Repositories
The public information repositories for the site are at the following locations:
Tuba City Public Library
78 Main Street
Tuba City, AZ
EPA Site Manager
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
After Hours (Emergency Response)