2023 0130 FINAL red bluff monitoring report.pdf

United States

Department of

Agriculture

Forest

Service

Tonto National Forest

Supervisor’s Office

2324 E. McDowell Rd.

Phoenix, Arizona - 85006

Phone (602) 225-5200

America's Working Forests - Caring Every Day in Every Way Printed on Recycled Paper

File Code: 2160 Date: January 30, 2023 Route To:

Subject: Red Bluff Mine Monitoring Report

To: The Project File

FEDERAL ON-SCENE COORDINATOR 2022 MONITORING REPORT

From: Ernesto Maldonado, Arizona On-Scene Coordinator

Response Authority: CERCLA

Incident Category: Abandoned Mine Clean Up

Category of Removal: Non-Time Critical

Action Memorandum Status: Completed/signed: 09/28/2018

Contract No.: 12837118D0008

Removal Action Start Date: 10/28/2018

Removal Action Completion Date: 02/05/2019

I. SUMMARY

A. Background

Uranium was first prospected in the Sierra Ancha Mountains as early as 1950. Uranium ore was extracted from the former Red Bluff Mine between 1953 and 1956. From 1959 until 1973, the mining claimant unsuccessfully appealed for a patent on three additional lode claims and two mill sites. The property was then transferred and subsequently leased, then subleased, from 1974 until 1980. During this time the mine site was subject to exploratory drilling in preparation for further development, but it had become economically unfeasible to do so by 1980.

The former Red Bluff Mine is located approximately 87 miles east of Phoenix, Arizona; 26 miles north-northwest of Globe, Arizona; and 33 miles south of Young, Arizona. The site covers approximately 42 acres in Gila County, Arizona, in Section 31, Township 5 North, Range 14

East, Gila and Salt River Meridian.

The site is situated on a bluff above the Warm Creek canyon in the Sierra Ancha Mountains southwest of Aztec Peak and north of the Salt River at elevations ranging from approximately

3,500 to 3,800 feet above mean sea level. Approximately 8,000 cubic yards of uncontained uranium ore was piled on the Upper Mine Site where open mine features were also located. The

Lower Mine Site was located in the Tonto Basin Ranger District, approximately 1/4 mile south-southwest of the Upper Mine Site above Warm Creek and featured two unstable buildings.

Overlooking Warm Canyon and Lake Roosevelt with Red Bluff in the center

B. Response Actions

In 2016, the Forest Service hired HelioTech to conduct a Preliminary Assessment/Site

Inspection (PA/SI) at the Red Bluff Mine. The PA/SI report confirmed the presence of radionuclides, specifically uranium, radon, 230thorium, 226radium along the access road, mine workings, house/pond, and waste rock piles. Concentrations of metals including antimony, arsenic, cadmium, chromium, copper, lead, manganese, nickel, selenium, silver, vanadium, and zinc at were found to exceed ecological benchmarks throughout the site. The contaminants of concern for human receptors were arsenic, lead, uranium, radon, 230thorium, and 226radium. These contaminants of concern are hazardous substances as defined by Section 101(14) of CERCLA, 42 U.S.C § 9601(14).

Following the PA/SI, in 2017 the Forest Service commissioned HelioTech once again to assist in developing removal action alternatives in the EE/CA. Further testing was performed to evaluate the extent of contamination of heavy metals, radon gas, and gamma radiation throughout the site. No surface water was present during the evaluation period.

The report concluded that 266Ra was the primary radionuclide of concern (ROC) with the highest concentrations at the Upper Mine Site and central portion of Warm Creek. The

EE/CA also concluded that the site posed an unacceptable risk to human and ecological receptors. Migration of radionuclide and metal impacted soils and mine waste rock from the site to the surrounding area was also confirmed.

A decision was reached by the Forest Service on September 25, 2018 to execute a Non-

Time Critical Removal Action. ERRG was hired to perform the work from October 28, 2018 – February 5, 2019.

Final Site Overview

A Backfilled Adit and Repository Construction

II. 2019 MONITORING INSPECTION

The OSC reported that it was too early to tell if revegetation of the cell (repository) sites had been thoroughly successful. The fences were intact and there were no signs of foot traffic around the site.

Site Fencing and Site Access Obstruction

III. 2020 MONITORING INSPECTION

On October 21st, 2020, Ernesto Maldonado, a Civil Engineer with the U.S Forest Service conducted a monitoring inspection at the Red Bluff Site. Fencing around the perimeter of the Site was still intact and there appeared to be no sign of humans entering the area, though deer tracks were visible inside the perimeter.

Site Fencing and Postings

The consolidation cell appeared to be in good condition with little erosion present and vegetation resembling the more natural areas. The area vegetation is generally dry because of the lack of rain. From the southeast corner of the cell, there appears to be a channel of white precipitate leading from the cell to the road that leads to the upper workings. This precipitate is similar in appearance to the precipitate observed emanating from the faces of the workings before the removal action began.

View of the Cell in the Foreground and Borrow Area from Above (Left) View of the East Side of the Cell

(Right)

Rocks Covered in Precipitate Leading from the Site (Left) Close up of Precipitate Further down the Road from the Cell (Right)

Two barb wire fences had to be crawled under to reach the upper workings from the cell area.

There was significant water erosion of the clean fill material from the borrow areas and little vegetation. Erosion seems to be local to the areas with clean fill and not to the surrounding bedrock areas. Specifically, the main eroded area was where the open cuts were filled during the removal action. Water likely flows from both the cell area and the road. The boulders set in place to obstruct the road and prevent erosion were still present and one of the shafts filled with waste rock material and clean fill had settled. Elsewhere, the borrow area erosion control measures and lower workings appear to be intact.

Erosion Leading from the Cell above the Main Eroded Area (Left) Main Eroded Area Approximately 3-4 feet bgs at the Lowest Point (Right)

Clean Fill Cover Eroding away at the Portal in the Upper Workings (Left), Erosion Adjacent to Main Eroded

Area (Right)

More Erosion Below Upper Workings (Left), Settled Shaft about 2-3 Feet Deep Above Upper Workings

(Right)

Lower Workings Portal Covering (Left) Borrow Area (Right)

IV. 2022 MONITORING INSPECTION

On November 30th, 2022, Ernesto Maldonado, the OSC (detailer), visited the Site to perform a monitoring inspection. The gate at the Site entrance was open upon arrival, a Forest Service lock was installed to keep vehicular traffic out. Walking through the Site, one set of vehicle tracks was noted going through the access road north of the repository. The perimeter of the repository was walked, and the fence, signs, and vegetation on the repository appeared intact.

Views of the Site Entrance

More vegetation is generally present at the Site than in the 2020 visit. The winze or small shaft in the upper workings could not be found this visit, and more care had to be taken to traverse the

Site for safety. Various animal droppings were found throughout the Site and a colony of rabbits was encountered.

Views of the Repository and Fence

Adit 7 and Surrounding Area with Recovered Vegetation

Adit 8 and Open Cut with Recovered Vegetation

Another visit was conducted on December 14th, 2022, to determine a course of action to address the erosion issues encountered at the Upper Workings Area. Generally, the backfill used as cover for the Upper Workings has little cohesiveness in contrast to the hard rock surfaces of the workings and surrounding native ground. These conditions are causing increased surface runoff with little infiltration taken by the native surface. Open cuts 2, 3, 4, and 5 have a loss of cover 2-

3 ft with waste rock potentially exposed.

A radiation meter was brought but its last calibration date is unknown. It was brought for general awareness of radioactivity levels at different areas of the Site so readings were not documented.

Open Cuts 2, 3, 4/5 Showing Erosion

Toe of Open Cuts 4/5 and 3 Looking Upslope

Readings from Radiation Meter (Calibration Status Unknown)

IV. RECOMMENDATIONS

It would be beneficial to keep surface runoff from reaching the Upper Workings Area by constructing an earthen berm along the existing fence. The berm would tie into a V-Ditch or wider channel improvement that will direct much of the runoff north, away from the eroded areas.

The berm could be constructed from smaller riprap and the cover material used in the original construction; these materials are present at the former pit north of the repository. Preliminary estimates of material quantities are as follows:

• 150 LF of Earthen Berm

• 200 LF of Drainage Improvement

• 80 CY (compacted, in-place) backfill of workings

• 1 LS Cut and Repair Fencing as Needed

Diagram of Proposed Runoff Diversion

Proposed Material Source Adjacent to Site

/s/ Ernesto Maldonado Arizona Statewide On-Scene Coordinator (Detailer)

Note: This report was prepared for the Project File and was not distributed to the Project

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