Portions of the Navajo Nation are on geologic formations rich in radioactive uranium ores.  Beginning in the 1940s, widespread mining and milling of uranium ore for national defense and energy purposes on Navajo tribal lands led to a legacy of abandoned uranium mines.  The Site is one of approximately 520 abandoned uranium mines (AUM) located on the Navajo Nation.  Nearby residents have expressed concern to the Navajo Nation Environmental Protection Agency (NN EPA) regarding the potential for wind-blown and water-borne radioactive particles to migrate from the Site and impact their health as well as the health of their livestock and the environment.  During a site inspection performed by the NN EPA in July 2005, gamma radiation activity greater than two times the background level was detected in approximately 80 locations at the Site.  NN EPA requested assistance from the EPA in performing an investigation to determine the nature and extent of the contamination and to mitigate any potential impacts to human health and/or the environment. 

CERCLA incident category: Inactive production facility (abandoned uranium mine)

Time-Critical removal action

The Site encompasses the former Skyline Mine on top of Oljato Mesa (the Mesa), mine wastes on the eastern edge of the Mesa directly below the mine, mine wastes in the Skyline AUM Waste Piles (SMWP), and associated residential and pastoral areas east and down gradient from the foot of the Mesa.  The SMWP are located approximately 700 feet below the former mine at the eastern base of the Mesa and are characterized by talus slopes covered with waste rock and/or waste ore that was pushed over or fell from the top of the Mesa where the mine was located.  Portions of the cliff directly below the mine are visibly stained a grey-green color from this activity.  As part of regular mine operations, a gondola was used to transport ore down to the foot of the Mesa where it was loaded into trucks for transport to an offsite mill.  Portions of the gondola, including steel cables, remain at the foot of the Mesa.

Approximately five home sites with residential structures are located between 1,490 and 1,800 feet east and northeast of the SMWP.  Land use in the project area is characterized by low density of single-family residences surrounded by open grazing land.  The top of the Mesa and the SMWP area are used seasonally during the spring, summer, and fall by local residents as pastureland for grazing sheep and cattle and for gathering traditional herbs and plants.  The road to the top of the Mesa is in extremely poor condition and therefore access to the top of the Mesa is limited to 4-wheel drive vehicles, all terrain vehicles, or foot traffic.  There is no known permanent infrastructure on the top of the Mesa.

The Site is located in the Oljato Chapter on the Navajo Nation Indian Reservation, Township 43 South, Range 15 East, Section 26, NW ¼ (Latitude: 37.0205530°, Longitude: -110.2308250°), near Monument Valley, San Juan County, Utah.  See Figure 1 for a Site Location Map. 

Current Site conditions pose ongoing releases and the threat of future releases of hazardous substances, namely: uranium and its progeny (i.e., radium-226 and radon) and ionizing gamma and alpha radiation associated with those progeny.  The likelihood of direct human exposure, via ingestion and/or inhalation of hazardous substances, and the threat of future releases and migration of those substances, pose an imminent and substantial endangerment to the public health or welfare or the environment based on the factors set forth in the NCP, 40 CFR § 300.415(b)(2). 

In November 2008, EPA and the START Contractor conducted radiation assessments at the Site in coordination with NN EPA.   A background area was established 1.35 miles east-southeast of the SMWP in an area with no suspected impacts from mining.  First, 1-second total gamma radiation activity measurements using a GPS integrated ratemeter were collected in the background and SMWP areas.  Two areas were identified as having elevated gamma activity, and designated the talus slope decision area (TSDA) and the trans-loading decision area (TLDA).  Next, sampling grids were established that encompassed the TSDA, TLDA, and the background area respectively.  The grid size and number of samples to be collected within each grid were determined using the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) version of Visual Sample Plan software and were the same relative number, orientation, and spacing in each case.  A total of 42 surface soil samples were collected as grab samples and analyzed by GEL Laboratories, LLC for Ra-226 (Gamma Spec with In-growth) by EML HASL 300.4.5.2.3.

From July 2009 to March 2010, additional soil sampling and total gamma activity surveys were conducted to further delineate the lateral and vertical extent of contamination in the TLDA, the TSDA, and the unnamed arroyo that receives runoff from the Skyline AUM and the north side of the TSDA.  See Figure 2 for a Site Features Map.  Based on the assessment results EPA determined that a removal action was necessary.

2.1.1.1  Current Situation

“Monsoon Season” has officially begun at the Site.  Localized, intermittent thunderstorms moving through the Four Corners area have brought periods of heavy rainfall at and near the Site.  This has impacted roads at the site, especially the steep mesa access road where water torrents of water have washed away sections of the roadway, necessitating repairs.  Additionally, crews working on the top of the mesa are monitoring for lightning and will stop work if seen within five miles of the Site.The skyline yarder is being used with a dredge bucket attached to the carriage to excavate steep sections of the slope below the main opening on the edge of the Mesa that were inaccessible with an excavator.   

July 5 – 9, 2011

OSC Musante onsite this week.

This week ERRS:

-Skyline subcontractor completed re-rigging of cable yarder system.

-Completed excavation of contaminated soils in the TSDA area.

-Completed site-wide flood contingency improvements.

-Continued water conveyance system operations.

-Continued site-wide road improvements and maintenance.

-Continued dust control program using water for dust suppression.

-Continued transport of stockpiled mine waste materials to top of Mesa via the skyline cable yarder.

-Began excavation on lower portion of upper slope area below the mine opening using the skyline with a dredge bucket.

START performed air sampling around work zones as part of the effluent dust sampling program, and performed confirmation radiation surveys and sampling in the Arroyo and TSDA areas.

July 11 – 15, 2011

OSC Musante onsite this week.

This week ERRS:

-Continued water conveyance system operations.

-Continued site-wide road improvements and maintenance.

-Continued dust control program using water for dust suppression.

-Continued excavation on lower portion of upper slope area below the mine opening using the skyline with a dredge bucket.

-Began restoration of the soil borrow area on top of the mesa.

Mobilization for removal activities and site setup began the week of March 28, 2011.  Construction of the repository began the week of April 4, 2011, and was completed at the end of May.  Excavation of mine waste from the upper slope below the mine opening and valley floor areas on the north side of Oljato Mesa began in early June and continues.

EPA to date has been unable to identify any existing PRPs.  EPA will continue to analyze the voluminous responses to the information requests it sent to numerous parties associated with mining in general on the Navajo Reservation.  Because of the urgency of this removal, EPA is proceeding with a fund-lead action.  EPA will continue to review the information referenced above to determine whether viable and liable parties may be identified, and will pursue recovery of the removal costs if appropriate. 

There are no progress metrics to report at this time.  Off-site disposal is not planned for this removal.  Uranium tailing wastes at the Site will be transferred to the on-site repository.  Total volumes of waste moved into the repository may be reported in future POLREPs.

- Uranium mine waste from the slope below the mine and the foot of the mesa will continue to be moved into the repository.  A skyline yarder, like the old Skyline, will be used to transport the mine waste up to the top of the mesa.  Water will be used to control dust and make sure the mine waste doesn’t spread from the site.  Air sampling will be conducted around the work areas to check for any radioactive dust.

-Once all the tailings have been placed in the repository, another plastic liner will be installed over the top.  Then a soil cap will be placed over the top liner to protect it from sun and wind.

-Areas impacted by removal activities will be seeded with native plant species to help restore the land.

- Repository excavation was slowed due to hard rock formations underlying surface soils.  This delay has resulted in an extended project schedule and additional project costs.

-“Monsoon season” weather with heavy rains and thunderstorms have impacted site access roads and work progress.

-Need to inform nearby residents who were given temporary lodging of the extended project schedule.  Effluent dust sampling results to date have all been well below the site specific action level, which demonstrates that dust suppression has been effective and there is no risk of significant off-site exposure.  Based on this nearby residents will be given the option to return to their homes.  If the residents have concerns of potential exposure from effluent dust, regardless of the sampling results, then EPA will continue to provide temporary lodging.

On 7/10, OSC Musante gave a tour of the site to NN EPA Eugene Esplain.

On 7/13, OSC Musante gave a tour of the site to NN EPA Environmental Department Manager Diane Malone, Superfund Program Manager Freida White, and Project Manager Eugene Esplain and EPA Superfund Division Director Jane Diamond and Emergency Response Section Chief Harry Allen.

OSC Musante will attend the Oljato Chapter meeting on 7/10 to provide updates on project progress/schedule and answer question from the community.

OSC Musante is also working with CIC Brian Davidson to develop a written CIP that documents community outreach to date.

Navajo Nation EPA Superfund (NN EPA)

Navajo Nation Abandoned Mine Lands Reclamation Program (AML)

Navajo Nation Department of Water Resources

website: www.epaosc.org/SkylineAUM

The next POLREP will be submitted on 8/1/11.

-maps: Skyline Fig 1 Site Location, Skyline Fig 2 Site Features