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.

May 23 – 27, 2011

OSC Musante onsite this week.

This week ERRS:

-Continued screening plant operations.

-Continued water conveyance system operations.

-Continued site-wide road improvements and maintenance.

-Continued dust control program using water for dust suppression.

-Completed construction of access roads on north side of mesa to the TLDA, TSDA, and Arroyo areas.

-Completed installation of liner materials in repository.

-Began placement of liner cover soil.

-Began excavation and stockpiling of AML repository to create access to upper slope area below mine opening.  Stockpiled materials were coated with soil sealant and covered with visqueen to prevent migration.

-Began procurement of trailers to house nearby residents during temporary relocation.

START provided engineering design implementation support, conducted repository liner QC testing performed air sampling as part of the effluent dust sampling program, and performed radiation surveys as needed.

May 28 – 30

No work performed.  An extended weekend break was taken for the holiday because site workers have only had one day off per week since the end of March.

May 31 – June 4, 2011

OSC Zuroski onsite this week to cover for OSC Musante.

This week ERRS:

-Continued screening plant operations.

-Continued water conveyance system operations.

-Continued site-wide road improvements and maintenance.

-Continued dust control program using water for dust suppression.

-Completed placement of liner cover soil.

-Completed excavation and stockpiling of AML repository.

-Began moving stockpiled AML materials into repository.

-Began excavation on upper slope area below mine opening.

-Demarcated work zones in valley floor on north side of mesa (TLDA, TSDA, Arroyo).

-Began construction of a staging area for excavated soils in the TLDA.

-Began excavation of soils in small wash adjacent to the TSDA.

-Took delivery of temporary relocation trailers and set-up services at trailer parks.

In April 2010, the ERRS contractor was mobilized to stabilize unconsolidated radioactive tailings at the site.  A soil sealant was applied over the waste piles to prevent wind and water erosion, and fencing was erected around the piles to restrict access.  An Action Memorandum for a time-critical removal action at the site was approved in September 2010.  In November 2010, the ERRS contractor was mobilized to the site to improve the access road up to the top of Oljato Mesa.  Between November 2010 and March 2011, archaeological and biological surveys were performed across all areas expected to be impacted by removal activities.  The START contractor developed engineering design plans for the repository.  OSC Musante participated in Oljato Chapter meetings to provide updates on site progress to the community.  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 has been the main work activity to date.

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. 

- Uranium mine waste from the slope below the mine and the foot of the mesa will be moved into the repository, starting in late May/early June.  A high-line 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.  OSC Musante will submit a request to increase the Action Memo ceiling.

-Periods of gusty, high winds have made for difficulty working conditions and increased the need for maintenance on heavy equipment.

-Prior to excavation/transport of radioactive tailings, EPA is providing temporary relocation for residents within approximately 0.5 miles of the site.  This due to the nuisance associated with heavy equipment operations and to eliminate the exposure potential to any effluent dust. 

-EPA has derived site-specific clean-up action levels for the different areas at the site based on an excess cancer risk range of 1x10^-4.  These action levels will be proposed to NNEPA for concurrence. 

All site personnel attended a site-specific radiation training on 5/2.  The training was delivered by the radiation specialty subcontractor.

OSC Musante will attend the Oljato Chapter meeting on 6/12 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 6/20/11.

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