2023 0515 cibola uranium monitoring report.pdf

United States

Department of

Agriculture

Forest

Service

Southwestern

Regional Office

333 Broadway SE

Albuquerque, NM 87102

505-842-3292

FAX (505) 842-3800

Caring for the Land and Serving People Printed on Recycled Paper

File Code: 2160 Date: May 31, 2023

Subject: Cibola Uranium Mines Remediation – 2023 Post-Construction Completion

Monitoring Report

To: Steven Hattenbach, Forest Supervisor, Cibola National Forest

From: Steven McDonald, On-Scene Coordinator

2023 Post-Construction Completion Monitoring Report

Response Authority: CERCLA

Incident Category: Inactive Mine Site

Category of Removal: Non-Time Critical

Action Memorandum Status: Completed/signed November 6, 2015

Contract No.: AG-8371-S-15-0033

Removal Action Start Date: February 29, 2016

Removal Action Completion Date: June 20, 2016

I. Summary of Events

A. Background

The Cibola Uranium Mines Remediation (Site) project includes five abandoned mines located in two mining districts, the Grants Mining District and the Scholle Mining District. Past mining activities left the five mines littered with waste rock piles and mine features such as adits and open pits. All the sites are typical of high New Mexico desert and are dry with ephemeral streams. The land within these sites is primarily used for grazing and outdoor recreation.

Grants Mining District

Four of the five mines are in the Grants Mining District near Grants, New Mexico, within the Mt.

Taylor Ranger District of the Cibola National Forest. The Zia, La Jara, and Taffy Mines are in

Cibola County. The Vallejo Mine is in McKinley County. The mine sites are located on the southwestern side of the La Jara Mesa.

• Zia Mine: Uranium deposits occur in the Todilto Limestone and upper part of the Entrada

Sandstone. The Zia Mine produced uranium, vanadium, fluorine-fluorite, and barium-barite from

1952-1958. The mine consists of two moderately sized excavations: the first pit, 150 feet by 90 feet by 6 feet deep, and the second pit is 150 feet by 60 feet by 25 feet deep. Two small adits are in the second pit, one on the south wall and one on the west wall. Approximately 56 significant features were identified during the field investigation including two adits, 46 waste rock piles, two trenches mining debris piles, and open pits. There was approximately 39,670 cubic yards of uncontained and uncontrolled waste rock material. This mine is located in the SW ¼ of Section 15

T12N R9W.

• La Jara Mine: Small uranium deposits were found in the Todilto Limestone. The mine consists of one open excavation 75 feet by 125 feet by approximately 6 feet deep. There were 28 significant features identified during the field investigation including 22 waste rock piles, 3 open pits, and a trench. There was approximately 4,460 cubic yards of uncontained and uncontrolled waste rock material. The mine is located northeast of the Zia Mine in the NE ¼ of Section 15 T12N R9W.

• Taffy Mine: Uranium is within sandstone deposits of the Morrison Formation. The Taffy Mine consists of two lateral cuts into the side of the mesa. The downslope cut is approximately 250 feet by 25 feet by a maximum of 15 feet high. There was an originally estimated 760 cubic yards of uncontained and uncontrolled waste rock material. This mine is located in the SW ¼ of Section 11

T12N R9W.

• Vallejo Mine: The mine is also known as Section 34, Farris, and Double Jerry Mine. The uranium deposits occur in the Todilto Limestone and the ore was mined from an inclined shaft from 1957 to

1962. The mine area consists of a single large peninsula approximately 290 feet by 200 feet by 10 feet containing partially buried waste rock piles scattered throughout and bordered on the north, east, and west by arroyos. Mine features include 7 waste rock piles of that were originally estimated to be 1,725 cubic yards. The mine is located in the SW ¼ of Section 34 T13N R9W. This mine is also known as Double Jerry Mine and Farris Mine.

Open pit and waste rock piles at Zia Mine before removal

Scholle Mining District

The Abo Mine is in the Scholle Mining District located west of Mountainair, New Mexico, in the

Mountainair Ranger District of the Cibola National Forest. The mine area is located on the east side of the Cañon Salado at the southern tip of the Manzano Mountains in Torrance County.

• Abo Mine: The mine is also known as the Pioneer Copper Mine and Hannie Mine. Uranium was noted in sandstone deposits of the Abo Formation at the abandoned Pioneer Copper Mine in 1949 and this mine was renamed the Hannie Mine. The area was investigated by the Atomic Energy Commission in 1953 and 1955 for uranium potential through a drilling program but no economic deposits were discovered. There is no record of any uranium ore being shipped. The district has been inactive since

1961. The waste rock pile was estimated at approximately 1,510 cubic yards. This mine is in the NE

¼ of Section 22 T3N R5E. This mine should not be confused with the Abo Mine on BLM land located further south.

In 2012, the Forest Service prepared a Preliminary Assessment/Site Investigation and a field gamma walkover survey at the Cibola Uranium Mines Site. Analytical results concluded concentrations of radionuclides and heavy metals were significantly greater than background concentrations at each of the five mine sites. Gamma radiation and radium-226 were the primary concerns at each site. These concentrations presented a significant risk to frequent site visitors and ecological receptors.

In 2014, the Forest Service prepared an Engineering Evaluation/Cost Assessment (EE/CA) at the Site.

Additional field gamma survey results and soil analysis confirmed gamma radiation, radium-226, and arsenic levels in waste rock piles were significantly greater than background concentrations and potentially presented a significant risk to frequent site visitors and ecological receptors. Gamma radiation, radium-226, and arsenic were the contaminants of concern at each site.

On November 6, 2015, the Forest Service decided to conduct an environmental remediation (cleanup) at the Site. Based on the analysis and findings of the EE/CA, the following Removal Action Objectives for the response action were developed for the Site:

• Reduce risk to site visitors from direct contact with radium-226 in waste rock material.

• Reduce the potential for contaminant transport from contaminant source material to the surrounding environment.

To accomplish these objectives, the Forest Service selected cleanup action levels based on the

UMTRCA soil standard of 5 pCi/g of radium 226 plus background. The UMTRCA soil standard is based on residential land use and is protective of human health. Based on background studies, the cleanup action level for the site will be 5.83 pCi/g of radium-226 averaged over the first 15 cm of soil.

The Forest Service hired an environmental firm to perform the remediation (cleanup) at the Cibola

Uranium Mines in 2015.

Waste rock with elevated levels of radiation at La Jara Mine before removal

B. Response Actions

In 2015, Engineering Remediation Resources Group, Inc. (ERRG), was awarded the contract for remediation of four of the smaller mines, not including the Zia Mine. The original cost of the remediation for the four mines was $754,446.95. In February 2016, additional funds became available, and the cleanup of the Zia Mine was added to the project for an additional cost of $657,593.16. ERRG mobilized to the site on February 29, 2016, and began reconstruction of the access roads on the Mount

Taylor Ranger District on March 2, 2016. Waste rock was hauled from Taffy Mine to the open pits at

Zia Mine which served as the repository for contaminated material. This location was selected because the open pits were on top of a small flat mesa that was high and dry. Zia Mine also had most of the contaminated material so it minimized the transport of contaminated material. A total of 3,801 cubic yards of radioactive waste was hauled from Taffy Mine to the Zia Repository to achieve the cleanup standards.

The work shifted to the cleanup at Abo Mine on the Mountainair Ranger District. The old mine road was reconstructed to allow access for the clean-up. A total of 1,596 cubic yards of contaminated waste rock material was excavated and hauled to Zia repository. Approximately 609 cubic yards of clean cover soil from a nearby borrow source was spread over the former mine. Radiological soil testing was conducted, the access road to the Abo mine was obliterated, and disturbed areas were seeded with native grass to complete the cleanup at this mine site.

The Vallejo Mine was next on the schedule for cleanup. Excavation at Vallejo Mine revealed thick deposits of waste rock extending approximately fifteen feet below the ground surface that had been intermixed with the native sand. Test holes indicated that there was possibly 4,000 to 15,000 cubic yards of radioactive material buried in the area. Hauling operations were suspended to further evaluate the discovery of additional contaminated material. Work shifted to La Jara and Zia Mines.

La Jara Mine after completion of cleanup in 2016

Approximately 4,552 cubic yards of contaminated waste material was hauled from the La Jara Mine to the Zia Repository. Some 3,153 cubic yards of clean overburden material was spread at La Jara to restore the site to natural appearing contours and cover the radioactive bedrock. Soil testing indicated that the overburden material had slightly elevated levels of radionuclides so an additional 3,237cubic yards of clean material from the main borrow area was brought in and spread to cover the area to ensure all cleanup goals were achieved.

Nearly 39,670 cubic yards of contaminated waste material was removed from the land surrounding the open pits at Zia Mine and placed in the Zia Repository. The contaminated material was placed into the two open pits and compacted. The Zia Repository was shaped into twin circular mounds that rise above the former open pits. About 4,407 cubic yards of clean overburden material that had been left in piles was spread to natural contours over disturbed areas of the mine.

The contractor began constructing the Zia Repository cap in mid-May. The cap is a three-and-a-half-foot layer of silty sand from the main borrow area with gravel blended into the top foot of the cap. The cap is an evapotranspirative cover that will soak up any rainwater like a sponge and keep the contents of the repository dry. Slopes of the repository were a maximum of 20% to reduce the chance of erosion.

Construction of the cover required 15,640 cubic yards of soil from the main borrow area and an additional 1,624 cubic yards of gravel that was hauled in. The gravel reduces both wind and water erosion and is blended with the soil to encourage a good vegetative growth. A barbed wire fence was constructed around the repository to keep out ATVs and allow for plant revegetation.

During construction at Taffy Mine, the loose contaminated waste rock was stripped, exposing large areas of radioactive bedrock. These areas were covered with clean borrow material from the main borrow area to achieve cleanup goals. This required an additional 2,520 cubic yards of material. The area was then seeded, the old mine road closed off, and water bars constructed along the road.

Zia Repository at former location of Zia Uranium Mine in 2016

The main borrow area was reshaped to a more rounded and natural appearance. About 1,390 cubic yards of salvaged topsoil that had been stockpiled were spread over the area to a depth of 6 inches. The borrow area was drilled with native grass seed along with the disturbed areas at La Jara and Zia Mines to ensure revegetation. A two-foot-high berm was added to the south edge of the main borrow pit at the request of the District staff to prevent possible water diversion from nearby Lobo Creek.

In June, the contractor mobilized back to Vallejo Mine. Previously 2,304 cubic yards of material containing elevated gamma levels had been hauled to the Zia Repository. The remaining contaminated material at Vallejo was mixed with adjacent soil and gamma levels were similar to the background soil.

Approximately 5,592 cubic yards of contaminated material was consolidated and placed in the Vallejo

Repository. A three-foot soil cap was constructed over the repository using 6,503 cubic yards of cover material. The repository was further protected with 265 cubic yards of rock riprap. The area was seeded with native grass. Erosion control blankets made of coconut fiber were placed on the slopes to complete the project.

The cost to dispose of the additional waste at Vallejo Taffy and La Jara Mines along with the additional cover soil increased contract costs by $567,303.11. The final cleanup cost was $1,979,343.22. The cleanup was completed on June 20, 2016.

II. 2023 Monitoring Inspection

Zia Repository has natural appearance in 2023

Grants Mining District

A monitoring inspection trip was made on May 4, 2023, to the Grants Mining District to investigate the continued effectiveness of the removal action. The Zia Mine and Zia Repository were inspected.

The several acres that was previously covered by radioactive waste piles was now covered with good stands of native grass and shrubs. This flat area had been seed drilled and the area has filled in nicely over the last few years and now resembles a natural landscapes. The twin mounds of the Zia Repository are now presenting a more natural appearance and blend into the landscape. Vegetation is mostly shrubs on the repository rather than grass and there is a good number of weeds such as knapweed in evidence. These should gradually diminish as native vegetation takes over. The barbed wire fences that encircle the repository are intact and effective in preventing motor vehicles from climbing the slopes.

Vehicle tracks on cover soil at La Jara Mine in 2023

The La Jara Mine remediation was also inspected. Cover soil has some minor rill erosion and vegetation is very poor. Vegetation has decreased considerably since the last monitoring inspection.

Cover soil here was a silty sand that does not seem as amenable to grass growth as a sandier soil.

Vehicle tracks were apparent over the former mine area which might be impacting the revegetation.

The mine cover soil is mostly intact and performing its function in cutting off radiation from a few small areas of radioactive bedrock.

Taffy Mine with poor vegetation on steeper slopes in 2023

Taffy Mine remediation was also inspected. The access road had been blocked off with dirt berms and stump piles, but users have simply gone around these piles and created bypasses on the flat terrain.

Roadblocks on the steeper terrain have been completely effective as they cannot be bypassed and utilized large boulders. Accessing the mine requires a hike of over one mile. Vegetation on the portion of the old access road that was successfully blocked off is good with much native grass in evidence.

Water bars have been effective in reducing soil erosion. The mine itself was capped with the same silty sand used at La Jara and vegetation is poor. Little native grass growth has occurred. The mine cover soil is mostly intact and performing its function in cutting off radiation from a few small areas of radioactive bedrock associated with the sandstone. This area shows no sign of visitation.

The borrow source for the Zia Repository and cover soil for La Jara and Taffy mines was inspected.

This borrow source currently resembles and acts as a stock pond but was entirely dry at the time of this inspection. Some erosion was noticed at the northeast corner of the borrow pit which will need to be monitored to prevent possible gully formation and stream capture. Vegetation was poor as the bottom of the depression appears to be flooded often enough to prevent successful grass growth and resembles a mud flat.

Borrow source for Abo Mine in 2023 blends into surrounding area

Scholle Mining District

A monitoring inspection trip was made on May 11, 2023, to the Scholle Mining District to investigate the continued effectiveness of the removal action. The borrow source for the mine cap material was inspected and presents a natural and pleasing appearance that shows little indication of man-made disturbance. Vegetation resembles the surrounding area except that the low part of the depression has lusher vegetation due to water capture in the depression.

Abo Mine in 2023 with good vegetation on mine cover soil

The access road to Abo Mine is effectively blocked off to motor vehicles and vegetation has largely reestablished itself on the road. The mine adit remains blocked with rocks and the mine cover material is intact with little sign of erosion. Vegetation is good with some grass growth and other native vegetation. This mine site shows no sign of visitation. Areas surrounding the mine have naturally elevated levels of radiation due to erosion of uranium deposits over the millennia.

III. Recommendations

• The Regional Office will continue monitoring the site until vegetation is fully successful on all mine sites, and all cleanup goals are achieved.

• Addition of a better cover soil at La Jara is recommended as the existing soil is not conducive to vegetative growth. This is demonstrated by good grass growth on the former waste pile area at Zia in striking contrast to the very poor revegetation at La Jara with the only significant difference being the soil. Using the already disturbed soil at Zia is recommended as the borrow source, although it will be necessary to check the level of radiation to ensure it meets the cleanup goal.

• Erosion at the Zia borrow source will continue to be monitored and will be repaired if it becomes significant.

Any work necessary will be funded, designed, and inspected by the Regional Office staff in consultation with the District and Forest staff. Comments on this report are welcome.

/s/ Steven John McDonald

Steven John McDonald

New Mexico On-Scene Coordinator

(505) 842-3838 cc:

Project Mailing List