Department of the Interior, Geological Survey, WRD, Arizona District: Termination of Material License; Finding of No Significant Impact and Notice of Opportunity for a Hearing

The U.S. Nuclear Regulatory Commission (NRC) is considering terminating Material License 02-08779-01. This would allow the United States Geological Survey (USGS) to discontinue licensed maintenance activities for a radioactive 2.5 Ci²⁴¹ Americium—Beryllium (Am-Be) well logging source that it was unable to retrieve from an artesian well (#10) in the San Bernardino National Wildlife Refuge (SBNWR), Arizona. As a condition for the license termination, USGS would need to satisfactorily implement abandonment procedures for the well logging source as described in 10 CFR 39.15(a)(5).

Summary of the Environmental Assessment

Identification of the Proposed Action

The proposed action would terminate USGS's Material License 02-08779-01. With this termination, the USGS would be able to discontinue licensed maintenance activities for a 2.5 Ci²⁴¹ Am-Be well logging source that was determined to be irretrievable from well #10 in the San Bernardino National Wildlife Refuge.

The Need for the Proposed Action

The proposed action would determine if the license should be terminated. USGS previously took action to fulfill its obligation under NRC regulations to implement abandonment as described in 10 CFR 39.15(a)(5) by attempting to seal the source in place with cement. However, follow-up visual examination of the well with a downhole camera produced no evidence that the cement plug actually formed. The radioactive source has been underwater in the well for almost 12 years and USGS has conducted periodic sampling. During that time, the intermittent monitoring by USGS has not conclusively indicated whether or not water from the well has been contaminated by the source.

USGS has requested permission from the NRC to cease its monitoring activities and end USGS responsibilities related to the Am-Be source. Because of uncertainties related to the condition of the stainless steel source container, the effectiveness of a cement plug already installed, the impact additional attempts to recover the source may impose, and concerns about the potential for future contamination, NRC decided to prepare an environmental assessment (EA) to analyze three alternatives for final disposition of the Am-Be source: (1) Abandonment in place; (2) source retrieval; and (3) the no-action alternative.

Alternatives

Two of the three alternatives, abandonment in place and source retrieval, could ultimately result in license termination. The recommended alternative is abandonment of the source in place subsequent to compliance with NRC requirements for abandonment. Another potential alternative for final disposition of the source is undertaking an additional attempt at source retrieval by overdrilling the borehole and overcoring the cement plug. Denial of the license termination, the no-action alternative, is also available to NRC, but could require that monitoring continue indefinitely.

Background

The SBNWR is located approximately 30 km (19 miles) east of Douglas in southeastern Arizona immediately north of the Mexican border. The nearest city in Mexico is Agua Prieta, approximately 35 km (21 miles) to the southeast. The 930-ha (2,300-acre) SBNWR lies near the center of the San Bernardino Valley, a surface water drainage basin that straddles the U.S.-Mexican border.

In 1986, the U.S. Fish and Wildlife Service (FWS) requested that USGS log an artesian well (Well 10) that feeds Twin Pond within the SBNWR to assess the water production capacity of the well. Water from the well initially flows into a pond containing three federally threatened or endangered fish species and water from this pond, in turn, feeds an adjacent pond/wetland containing an endangered plant species.

The USGS used a radioactive sealed source to conduct well logging for the purpose of quantifying the water production capacity of the artesian well. The source is composed of²⁴¹ Am (originally 2.53 Ci) and Be compressed into a cylindrical pellet, within a double-walled stainless steel container. The radioactive material in the source,²⁴¹ Am (half-life of 432 years), emits alpha radiation which dislodges neutrons from Be. The Am-Be source is part of a larger neutron emission/detection tool commonly used in well logging. On July 15, 1986, the Am-Be neutron well-logging source was “lost” by USGS in Well 10. The Am-Be tool was torn from the logging cable as it was being returned to the surface during a logging run and the logging probe containing the source fell back down the well.

Three series of attempts were made to recover the source between July 15, 1986, and October 21, 1987. During these recovery attempts, the logging probe was damaged and the source was separated from the body of the well logging tool. USGS declared the source irretrievable on October 20, 1987. After this decision was reached, and in accordance with 10 CFR 39.15(a)(5), a 0.76 m³ (1 yd³) cement plug was emplaced around and above the source (that was presumed to be at the bottom of the well) and an inverted tricone drill bit with a 5-ft drill pipe subassembly was placed in the well at the top of the cement to prevent intrusion into the source.

On March 30, 1988, USGS returned to the site to inspect the well. Video logging of the well produced no evidence of the cement plug previously installed by USGS, and found the bottom of the well at a depth of 176 m (577 ft)—some 14 m (46 ft) deeper than the well depth sounded after emplacement of the cement and drill bit in 1987. The unexpected depth at which the well bottom was located after source abandonment and the lack of cement at the depth where it was expected to be encountered might be explained in two ways: (1) the fact that the original total drilled depth of the well is unknown, and (2) the possibility that drill cuttings or collapsed borewall material may have formed a bridge in the well at the 178 m (583 ft) depth.

The USGS has sampled the Well 10 water for²⁴¹ Am. Three samples collected in 1989 and 1990 indicated only traces of²⁴¹ Am in the well water, while the last four samples taken in 1990 did not show the presence of²⁴¹ Am. Based on the results of sampling for²⁴¹ Am in the well, USGS believes that continued monitoring is unwarranted.

Environmental Impacts

Because of the limited scope of activities, the EA focuses on geology/hydrology and impacts to ecological resources, and human health which might result from three alternatives for final disposition of the Am—Be source. The proposed alternatives would not (1) cause appreciable changes in employment at the site, (2) affect previously undisturbed areas, or (3) expand the developed area of the site. For these reasons, no significant impacts on socioeconomic, historic or archaeological resources would result from the proposed alternatives.

The Recommended Alternative: Abandonment in Place

The recommended alternative would abandon the radioactive source in place consistent with the requirements of 10 CFR Part 39.15. This regulation requires sealing the source in place with a cement plug, installing a mechanical device to prevent inadvertent intrusion, and posting a permanent sign with detailed descriptions of the source and borehole conditions.

The installation of a cement plug in the bottom portion of the well would provide for the positive sealing of the well below a depth of 152 m (500 ft) to isolate the source from the upper part of the well. The plug would prevent future mixing of²⁴¹ Am in water at the bottom of the well and would further reduce the likelihood of contaminant migration up the well column. Pressure grouting of the bottom of the well using low pressure pumps would force cement down into the low permeability region of the well, encapsulating the lost Am'Be source, the drilling subassembly and bit (intrusion preventer) previously placed in the well, and filling the wellbore to the desired level. Emplacement of this plug would effectively seal the logging source and drill bit assembly in place permanently and seal any²⁴¹ Am contamination which might leak from the source within the inactive groundwater flow zone.

This action would eliminate the possibility of potential mixing of contaminated water at the well bottom with the discharging artesian flow. With completion of the cementing of the well base, any contaminant release scenario would be by diffusion of the contaminant upward through approximately 30 m (100 ft) of cement grout or through the native silts and clays of the geologic formation surrounding the well. The combination of very low groundwater flow in this region and geochemical retardation processes would contain the americium from the source beneath the useable aquifer. Therefore, under this alternative no adverse impact would be expected to either the water quality of Well 10 or other wells in the area. After plugging the basal portion of the well, continued discharge of the artesian flow to the ponds and wetlands could continue.

Under this alternative, near-term ecological impacts would be minor and temporary, involving only minimal disturbance to the well site. Based on a Department of Energy (DOE) methodology for evaluating radiation effects on aquatic biota, no effects would be expected. Therefore, there is little potential for effects on any of the species of fish present in Twin Pond. As the²⁴¹ Am in solution sorbs to sediments, the concentration in water would become markedly less, and dose to fish would decrease even more. At such low levels, effects to other pond biota less sensitive than teleost fish would not be expected.

Because well 10 is located approximately 30-35 km (19-21 miles) from the nearest population centers, Douglas, Arizona, and Agua Prieta, Mexico, respectively, the EA finds there is little potential for an individual to have direct contact with Well 10 water.

Another route the EA examined for exposure to Well 10 contamination would be through the use of water from wells drilled into the same aquifer for drinking or irrigation. Because the geology and hydrology of the site and nearby region are complex and not thoroughly understood, several perspectives on human risk are presented to provide a picture of the potential risk.

As a bounding analysis, the EA evaluates the possibility that if, after many years, a contaminated plume of water could reach a hypothetical agricultural well about 1,000 m (3,300 ft) from the original contaminated source, the approximate annual dose would be less than 3 μSv/yr (0.3 mrem/yr), well below any Environmental Protection Agency and NRC regulatory limit of concern. Because home use pumping rates would not provide the “pressure relief” considered with the agricultural well, it is unlikely that water from the deep, slowly moving water would be taken up in the home well. Therefore, essentially no radiation dose would be received for the case of a home well.

Source Retrieval Alternative

Under this alternative, Well 10 would be re-drilled to a larger diameter and all liquids and solids removed would be contained and disposed of off-site. If the source has already been breached, the drill cuttings, particularly those from the deeper part of the well, would be expected to be contaminated with Am released from the source. If the source has not been breached, the potential exists that it could be breached during the retrieval process resulting in ²⁴¹ Am being dissolved in the drilling fluid and the water.

An accidental breach of the source container while conducting this alternative would be completely or at least partially controlled by the containment procedures that would be implemented. However, the potential for an accidental release from a breached source is a negative factor for this alternative. This could result in occupational doses and the potential for this area to be restricted from public access.

As a bounding scenario for this assessment, the EA has assumed that the entire contents of the source are lost directly into Twin Pond. Using a DOE methodology for evaluating radiation effects on aquatic biota, adverse effects could be expected.

No-action Alternative

Under the no-action alternative, the potential would remain for discharge of²⁴¹ Am contaminated water or particulate material from Well 10 into the adjacent ponds and wetlands. In addition, in the future, someone could inadvertently drill into the source in an effort to redevelop the well. Estimation of the likely concentrations that would be expected to result from this discharge suggests that the discharge would occur at low concentration over a long period of time since the²⁴¹ Am is expected to adsorb to soil and other particulate materials in the ground or in the well. Under this condition, no acute water quality, ecological, and human health effects would be expected. However, because the Am-Be source would not be sealed in the lower part of the well, continued monitoring would be necessary to ensure that unexpected contaminant concentrations do not occur in water or pond sediment.

Agencies and Persons Consulted

The FWS was consulted on the proposed action with respect to Section 7 of the Endangered Species Act of 1973. The State Historic Preservation Officer for the State of Arizona was consulted with respect to Section 106 of the National Historic Preservation Act.

Conclusion

The assessment of the recommended alternative, abandonment in place, indicates it would not result in adverse water quality or human health impacts and would produce only temporary and minor ecological impacts associated with emplacement of the cement plug. The potential exists that the source could be breached during the alternative of attempting source retrieval by overdrilling the borehole resulting in²⁴¹ Am being dissolved in the drilling fluid and the water and, therefore, additional effects could be expected. While not terminating the license would be unlikely to produce significant adverse impacts, it would require continued monitoring to ensure that unexpected contaminant concentrations do not occur in water or pond sediment.

The NRC staff concludes that provided USGS satisfactorily implements abandonment procedures for the well logging source as described in 10 CFR 39.15(c), the environmental impacts associated with the proposed license termination allowing the USGS to discontinue licensed maintenance activities for the 2.5 Ci;²⁴¹ Am-Be well logging source are expected to be insignificant.

Finding of No Significant Impact

The Commission has prepared an EA related to the termination of Material License 02-08779-01. Based on the EA, as previously summarized, the Commission has concluded that environmental impacts that would be created by the proposed action would not have a significant effect on the quality of the human environment and do not warrant the preparation of an Environmental Impact Statement. Accordingly, it has been determined that a Finding of No Significant Impact is appropriate.

Copies of the EA, NUREG/CR-6648, may be purchased from the Superintendent of Documents, U.S. Government Printing Office, P.O. Box 37082, Washington, DC 20402-9328. Copies are also available from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161. A copy is available for inspection and copying for a fee in the NRC Public Document Room, 2120 L Street, NW. (Lower Level), Washington, DC 20555-0001. The document is also accessible electronically through the ADAMS Public Legacy Library component on the NRC website, HTTP://www.nrc.gov,, the “Public Electronic Reading Room.”

Opportunity for a Hearing

Any person whose interest may be affected by the issuance of this license termination may file a request for a hearing. Any request for hearing must be filed with the Office of the Secretary, U.S. Nuclear Regulatory Commission, Washington, DC 20555, within 30 days of the publication of this notice in the Federal Register; be served on the NRC staff (Executive Director for Operations, One White Flint North, 11555 Rockville Pike, Rockville, Maryland 20852), and on the licensee (Department of the Interior, Geological Survey, WRD, Arizona District, 520 N. Park Ave., Suite 221, Tucson, AZ 85719); and must comply with the requirements for requesting a hearing set forth in the Commission's regulations, 10 CFR Part 2, Subpart L, “Information Hearing Procedures for Adjudications in Materials Licensing Proceedings.”

These requirements, which the request must address in detail, are:

1. The interest of the requestor in the proceeding;

2. How that interest may be affected by the results of the proceeding (including the reasons why the requestor should be permitted a hearing);

3. The requestor's areas of concern about the licensing activity that is the subject matter of the proceeding; and

4. The circumstances establishing that the request for hearing is timely—that is, filed within 30 days of the date of this notice.

In addressing how the requestor's interest may be affected by the proceeding, the request should describe the nature of the requestor's right under the Atomic Energy Act of 1954, as amended, to be made a party to the proceeding; the nature and extent of the requestor's property, financial, or other (i.e., health, safety) interest in the proceeding; and the possible effect of any order that may be entered in the proceeding upon the requestor's interest.