As described in the Final Building Characterization Report (Appendix C) and summarized below, none of the structures remaining on site are contaminated. Characterization of the buildings has shown the structures to meet NMED Surface and Volumetric Release Criteria for unrestricted release.

At NMED’s request, building characterization included radiation surveys, sampling and laboratory analyses of building materials in locations where the licensed radioactive materials were known to have been used, stored and/or released. These portions of the buildings were designated as Potential Areas of Concern (PAOC), PAOC-1 through PAOC-10 as shown in Figure 4-1. A description of each PAOC is summarized below.

• PAOC-1 is the northwest portion of the North Building. PAOC-1 was the location of the former Eberline Technical Services Group. This area included a wet lab, storage, inventory area and offices, and had been the location for use and storage of licensed RAM including short-term storage of the Am-241 prior to relocation to PAOC-4.
• PAOC-2 is a series of five storage closets located in the southwest corner of the Engineering portion of the North Building. These closets had reportedly been utilized for the storage of licensed RAM.
• PAOC-3 is the southeast portion of the North Building and is divided into three areas including: 1) the northwest section utilized for Engineering Prototypes; 2) the southwest section identified as an “Open Area” on the building map; and 3) the east half of PAOC-3 occupied by the “REAX” area. Each of these areas are suspected to have utilized licensed RAM in site operations.
• PAOC-4 is a room in the Middle Building on the west end of the loading dock and was utilized for the storage of licensed RAM including inactive sources. PAOC-4 is the former storage location of Am-241 received from the Albuquerque Eberline facility and following consolidation into a HIC was placed in PAOC-4 for long- term storage.
• PAOC-5 is the northeast portion of the South Building adjacent to the loading dock. PAOC-5 is comprised of three areas including: 1) an outgoing shipping area occupying the northwest half adjacent to the loading dock; 2) a shipping and receiving area occupying the southwest half; and 3) a material control area occupying the east half with an upper mezzanine area. The east half of PAOC-5 was reportedly used to store licensed RAM pending shipping, storage, and for stock inventory. All three of these areas were associated with incoming and outgoing devices and materials containing licensed RAMs.
• PAOC-6 is the South Building Production Floor occupying the center and eastern portion of the South Building. PAOC-6 is described in four quadrants (northwest, northeast, southwest and southeast).
  • PAOC-6NW was utilized for servicing counters (multi- purpose survey meters, radiation monitors, alpha and beta/gamma counters, and mini scalers) in the northwest corner with test, assembly and quality control areas occupying the remainder of PAOC-NW.
  • PAOC-6NE was utilized for calibration and test cell work in the northwest section and occupied by the former calibration well room in the northeast section. The reminder of the area was utilized for work with survey instruments including ion chambers, neutron meters, micro-R meters, telescoping poles, high range gamma meters, emergency kits, electronic personnel dosimeters, handheld contamination meters, natural background reduction and portable gamma spectrometers.
  • PAOC-6SW was utilized for work with environmental monitors including area monitors, alpha air monitors, particulate and gas monitors, iodine monitors, stock sampling systems and pumps in the northern section. The southern section was occupied by office cubicles.
  • PAOC-6SE was utilized for work with detectors including Geiger Muller (GM), gas sealed, scintillators, neutron, smart probes, detector cases and accessories in the northern section. The southern section was occupied by conference rooms, offices and trade show/demo items and storage.
• PAOC-7 is an electrical distribution room located adjacent to PAOC- 4 in the Middle Building. This area was designated as a PAOC at NMED’s request as a location where a potential release of activity within PAOC-4 (no known releases of activity had reportedly occurred within PAOC-4) could have migrated.
• PAOC-8 is a room located adjacent to PAOC-7 in the Middle Building for which prior use is unknown. This area was designated as a PAOC at NMED’s request as a location where a potential release of activity from PAOC-4 (no known releases of activity had reportedly occurred within PAOC-4) could have migrated.
• PAOC-9 is a stock room used of storage of metals and plastic located to the south of PAOC-4 off the loading dock in the Middle Building. This area was designated a PAOC at NMED’s request as a location where contaminated materials were reportedly stored by a former Company RSO.
• PAOC-10 is the men’s and women’s restrooms located to the west of PAOC-6 in the South Building. This area was designated a PAOC at NMED’s request as a location where a potential release of activity in the building could have come to be located by inadvertent transfer of contaminated materials from personnel or from Personal Protective Equipment (PPE) used by personnel.

All other areas of the buildings located outside of the PAOC-1 through PAOC-10 were concluded to be classified as non-impacted (as defined in MARSSIM) by licensed radioactive materials based on a review of the history of facility operations and use, storage, and reported release of licensed radioactive materials and the results of multiple scoping and characterization surveys completed from 2008 through 2022. Additional information supporting this conclusion is summarized and referenced in the HSA (CN, 2022c).

For each of the instrument types utilized to survey the buildings, reference background values were obtained for like materials (e.g., concrete, vinyl floor tiles, etc.) located in unimpacted areas of the facility with no known use of licensed RAM and/or no potential for impact from licensed RAM. The primary instruments used for characterization were Ludlum 43-93 dual alpha/beta probes and Ludlum 43-37-1 large area gas flow proportional counters for floor surfaces. Background measurements focused on common substrates, specifically concrete, vinyl floor tiles, and sheetrock. Background data were collected over multiple months and at different times throughout collection days to account for the significant influence of radon progeny on surveys for alpha emitters at the facility and for seasonal variation to maximize the quality of reference background data collected. Reference background values were consistent across media using handheld instrumentation, ranging from 2-4 cpm alpha and 200-400 cpm beta/gamma. Large area gas flow proportional counters on concrete and vinyl floor tiles had reference background of 20-30 cpm alpha and 2,000- 2,500 beta/gamma.

Results of building characterization are detailed in the Final Building Characterization Report included in Appendix C.

Results using field instruments indicated total alpha and beta/gamma activity detected at levels above background periodically in PAOC-1 through PAOC-10. In all locations detected activity levels were below NMED Surface Release Criteria for removable activity (i.e., screening criteria issued by NMED meeting a TEDE of 15 mrem/yr, for unrestricted release, see Section 5.1).

Results of sampling and laboratory testing of building materials at locations where alpha and beta/gamma activity were detected above background using survey instruments indicated levels reported below minimum detectable concentrations (MDCs) in 85 percent of the analyses. In the remaining 15 percent of analyses with reported detections above MDCs, all results were below the NMED Volumetric Release Criteria for unrestricted release, including:

• The two samples exhibiting the highest reported activity that approached, but were below, the NMED Volumetric Release Criteria were concrete floor samples 6-NE-F-7-RS and 6-NE-F-8-RS with levels of Cs-137 at 4.2 pCi/g and 4.8 pCi/g, respectively, as compared to the NMED Volumetric Release Criteria of 6.6 pCi/g. These two samples were collected from the concrete floor in PAOC- 6NE adjacent to a cut in the floor slab where Cs-137 contaminated soil had been removed during past remedial actions. The impacts at this location are attributed to minor cross-contamination of the concrete during past contaminated soil removal. This area is to be addressed during Phase 3 decommissioning actions.
• The majority (88 percent) of detected radionuclides reported above MDCs were associated with uranium (U-234, U-235, and U-238) reported at activity levels of only a fraction of a RCB Volumetric Release Criteria (e.g., the highest reported concentration of U-235 at 0.0504 pCi/g was in a concrete floor sample (5E-F-4-C) as compared to the NMED Volumetric Release Criterion of 4.82 pCi/g for U-235). A review of all building uranium results indicates that the average percentage, and the associated uncertainties (at one standard deviation), of U-234, U-235, and U-238 are consistent with the percentage of naturally occurring uranium in concrete materials as reported by Oak Ridge Institute for Science and Education (ORISE, 2012).
• One concrete sample from the ceiling in PAOC-6SE (PAOC-6-C-C- 254) indicated a low-level detection of Cs-137 at 0.395 pCi/g, well below the NMED Volumetric Release Criteria (6.6 pCi/g).
• The only other licensed radionuclide reported at levels above MDCs of any significance was Tritium (H-3). Tritium was reported at five locations: one in PAOC-6NE (floor sample 6NE-F-56-C) at 1.64 pCi/g; two in PAOC-5E (wall 5E-W-S-67-B-M and wall 5E-W-W-33- M at 1.45 pCi/g and 1.59 pCi/g, respectively); and two in PAOC-5W (floor 5W-F-30-C and wall 5W-W-E-52-A-M at 1.02 pCi/g and 2.58 pCi/g, respectively). The RCB Volumetric Release Criteria for H-3 is 64.8 pCi/g. Further evaluation of tritium in PAOC-5 and PAOC-6 provided confirmation that tritium was not present at levels above NMED Volumetric Release Criteria.

During building characterization surveys, no areas of elevated dose rates were observed. Dose rates were generally 15 – 17 uR/hr (0.015 – 0.017 mR/hr).

CN concluded that the combined results of surveys and radiochemical analyses of building materials in PAOC-1 through PAOC-10, the areas of the highest potential for residual impact from past use, storage and/or release of licensed radioactive material, provide sufficient evidence that building materials meet RCB Surface and Volumetric criteria for unrestricted release (CN, 2022b).

None of the Licensee’s systems, equipment, or building contents remaining on site are contaminated. Licensee equipment remaining on site has been determined to meet the NMED Surface and Volumetric Release Criteria for unrestricted use.

Surveys completed since the termination of site operations in 2007 identified systems and equipment exhibiting elevated alpha or beta/gamma activity above background levels, and as such, contaminated items were contained, managed and disposed of off-site as low-level radioactive waste (LLRW). A summary of the results of past surveys and investigations identifying contaminated systems and equipment are included in the HSA, Section 4.3.5, Contamination of Buildings Surface, Materials & Equipment (CN, 2022c). Investigations and remedial actions involving systems and equipment from the HSA are summarized below.

November 2007- Radiac & Foss Therapy Services completed the unloading of cesium sources from the low, medium, and high range calibration wells in 2007 (Foss, 2007). Loose Cs-137 contamination was discovered in the HRW when one of the sources stored in the HRW could not be recovered (TE, 2008a). The wells, and the remaining source within the HRW, were subsequently removed in 2010

March 2008– Dade Moeller & Associates (DMA) completed scoping surveys of the facility walls, floors, workspaces, materials, and equipment in 2008 and reported five (5) locations of isolated radioactive contamination (DMA, 2008). Details are summarized in the HSA.

The locations of elevated activity were addressed by DMA and the Company RSO by decontamination and/or containment for disposal. Two exceptions included Cs-137 contamination on the floor of the Source Well Calibration Room, which was contained with tape and labeled for control and future abatement, and elevated activity within the HRW addressed in 2010 (DMA, 2008).

April 2014- CN Associates, Inc. completed radiological surveys of items stored in the Radioactive Materials Storage Room in 2014 to identify any potential radiological contamination of items stored, and to release for disposition, those items shown to be free of contamination.

CN identified two contaminated items including one source storage pig exhibiting fixed beta gamma contamination and a shelf inside of a lead safe that was shown to exhibit very low-level fixed alpha and beta contamination. Both items were subsequently segregated for proper disposal as LLRW by the Company (CN, 2014).

June 2021– CN Associates, Inc. completed an Initial Assessment (IA) of materials and equipment (M&E) located within 10 PAOCs (Figure 4-1) in the buildings where RAM use, storage and/or release were known or suspected (CN, 2021c). The IA of M&E was conducted under the companion guidance to MARSSIM entitled “Multi-Agency Radiation Survey & Assessment of Materials & Equipment” (MARSAME, NRC, 2009) that is specific to M&E. This work was intended to supplement the characterization of the building surfaces conducted under MARSSIM specific to the M&E within the PAOCs.

Of the hundreds of items surveyed from PAOC 1-10, only two metal carts from PAOC-6 were found to contain loose elevated beta/gamma activity ranging from 160 to 460 corrected counts per minute (ccpm, as counts above background) detected on two Large Area Wipes (LAWs) of the carts. Collection of smears and direct static measurements subsequent to the LAWs indicated no activity detected above background, indicating that the LAWs had removed the low-level loose beta/gamma activity present. Both carts were moved to a waste storage area and resurveyed and found to exhibit no detectable activity above background and were released for recycling. Both metal carts had reportedly been used during previous removal of the HRW and breeched Cs-137 source (CN, 2021c).

June 2023- CN Associates, Inc. expanded evaluations of M&E in 2023 under MARSAME to include an IA of M&E over the remainder of the site (external to PAOC-1 through 10) (CN, 2023). The IA included the segregation of M&E into three general categories including: 1) Interior M&E (including M&E in non-impacted areas of the building); 2) Exterior M&E (including items stored outside of the building and concrete debris piles) and 3) Systems M&E (including building roofs, roof top units and vents, interior duct systems and lab hoods and drainage systems (sinks, floor drains, roof drains, etc.)). Consistent with the IA process under MARSAME, M&E within each category and group was subject to: 1) an inspection and inventory; 2) a review of historic records pertinent to the use and potential for impact to M&E from licensed radioactive materials; 3) process knowledge considerations regarding the potential for impact to M&E; and

3) sentinel measurements consisting of both radiation surveys, and where appropriate, sampling and analysis. Surveys and sampling included both biased measurements collected at locations representative of a higher potential for impact and random measurements to provide increased confidence (a 95 percent confidence interval) that selected materials (roofs and duct systems) were adequately characterized.

Results of the IA indicated the following for each category and group of M&E evaluated:

• Background values used during characterization surveys of M&E were collected in a like manner to those for structures, on unimpacted portions of like material. Background values on heating, ventilation and air conditioning (HVAC) components ranged from 0.3 to 1.3 cpm alpha and 200 to 300 cpm beta/gamma using handheld instrumentation.
• Interior M&E based on visual inspection, historic records, process knowledge and sentinel measurements, CN concluded that interior M&E within the remainder of the non-impacted facility (outside of PAOC-1 through PAOC-10) was classified as non-impacted. M&E in these areas was released for disposition as non-impacted general refuse to clear the building in advance of demolition.
• Exterior M&E based on visual inspection, historic records, process knowledge and sentinel measurements, CN concluded that exterior M&E (items stored outside the building in the Exterior Storage Area near the loading dock, one large concrete block and a pile of concrete debris that was created from demolition of the shield block in the former Calibration Well Room) was classified as non-impacted. Items in the exterior storage area were subsequently released and disposed or recycled. Concrete block was classified as non-impacted and remains on site to be dispositioned during future building demolition.
• Systems M&E based on visual inspection, historic records, process knowledge and sentinel measurements the following results were obtained for systems M&E by group:
  • Group 1 Systems M&E included evaluation of the roof of the South, Middle and North Buildings. Each roof was divided into 10-foot x 10-foot survey grids and subject to a 100 percent scan with a 3×3 NaI detector. Within each grid two fixed- point measurements were collected with an alpha beta dual probe detector including one on the gravel portion of the roof and one on the asphalt substrate below the gravel. In addition, one smear was collected from the asphalt substrate. All scans and fixed-point measurements were not discernable from background. All smears were reported at MDAs set below the lowest NMED Surface Release Criteria (14 dpm/100cm2 for alpha emitters and 4,670 dpm/100cm2 beta/gamma emitters). Testing by laboratory analysis of 14 samples also confirmed no impacts from licensed RAM. Based on these results CN concluded that the building roofs were classified as non-impacted.
  • Group 2 Systems M&E included evaluation of roof top units (RTUs) including mechanical HVAC units, laboratory hood units on the building roof and vent and drain stacks on the roof. Surveys of accessible portions of Group 2 systems included 100 percent scans with a 3×3 NaI detector, collection, and screening of LAWs from accessible surfaces, fixed point measurements of total and removable activity and removal and sampling of filters from HVAC RTUs. The only elements of Group 2 systems indicating evidence of impact from licensed RAM included the filters from the HVAC RTUs. Laboratory analysis of filters from 15 RTUs indicated Cs-137 detected in 12 of 15 samples at concentrations ranging from
  • 0.32 pCi/g (RTU-8) to 202.6 pCi/g (RTU-6). Results are summarized in Figure 4-2 showing the location of the four RTU’s with filters (all located on the roof of the South Building including RTU-4, 6, 9 & 10) exhibiting Cs-137 at concentrations above NMED Volumetric Release Criteria (6.6 pCi/g for Cs-137). The highest concentrations were detected in the filter from RTU-6 located near the former location of the HRW. The filters were contained and subsequently disposed as LLRW. Evaluation of all RTUs was expanded based on the filter results to include removal of the units from the roof, dismantlement, and a more detailed survey of RTU interior components. Results of these surveys confirmed the RTUs were not impacted by activity discernable from background and were classified as non-impacted M&E. The RTUs were subsequently released for disposition by off-site disposal and recycling as non-impacted waste.
  • Group 3 Systems M&E included all interior vents and duct work located within the buildings including HVAC ducts, laboratory hoods and wall vents. Surveys of Group 3 Systems M&E included LAWs on exterior and accessible portions of interior surfaces, collection, and survey of 541 random metal disc samples from HVAC ducts for survey of fixed-point total and removable activity, In Situ Object Counting System (ISOCS) screening of selected discs, smears and LAWs and laboratory analysis of selected samples for independent confirmation. HVAC ducts for RTU-5, 6 and 7 (located in the former production area (PAOC-6) and near the former HRW area) were also dismantled and surveyed on the interior and exterior of the duct. Results of LAWs indicated one location of elevated beta/gamma activity on the interior of the duct for RTU-7 that was 100 cpm above background and subsequently identified as Cs-137. Further evaluation of the duct from RTU-7 indicated no activity discernable from background. Evaluation of the 541 random disc samples collected from HVAC duct indicated alpha activity in 26 samples exceeding the lowest NMED screening criteria of 14 dpm/100cm2 and no gross beta-gamma activity discernable from background. Evaluation of 31 metal discs by ISOCS indicated no activity above the 14 dpm/100cm2 release criteria and one disc indicating detectable Cs-137 at 7.32 dpm/100cm2 (above the minimum detectable activity (MDA) of 5.2 dpm/100cm2 but well below the NMED Volumetric Release Criteria of 16,800 dpm/100cm2 (see Section 5.1). Laboratory testing confirmed ISOCS achievement of MDAs. Based on these results, CN concluded that Group 3 Systems M&E were classified as non- impacted.
  • Group 4 Systems M&E included all interior sinks, and floor drains within the buildings (limited to the North and South Buildings). Based on visual inspection, historic records, process knowledge and sentinel measurements, CN concluded that Group 4 Systems M&E was classified as non- impacted.
  • Group 5 Systems M&E included exterior roof drains, sumps, and dry wells. Based on visual inspection, historic records, process knowledge and sentinel measurements, CN concluded that Group 5 Systems M&E was classified as non- impacted.

In summary, limited impacts to M&E were identified and impacted M&E segregated for containment and subsequent disposal as LLRW. The remaining M&E was released for management as non-impacted waste for disposal, recycling or subsequent disposition during building demolition.

Consistent with NUREG-1757 guidance, surface soil is defined as soil located within the upper six inches of the ground surface where applicable screening criteria may be used to determine compliance with NMED Release Criteria for unrestricted use (in this case 15 mrem/yr, see Section 5). Surveys and investigations completed since termination of site operations in 2007 indicated no evidence of surface soil contamination (or contamination of concrete or asphalt surfaces) at the site (CN, 2021a). The three instances of subsurface soil contamination identified at the site are described in Section 4.4.

Background levels for target radionuclides in surface soil (both unimpacted soil on and off-site) and exterior concrete and asphalt surfaces on-site, are summarized below based on laboratory analyses of samples analyzed by alpha and gamma spectroscopy (CN, 2021a). The only licensed radionuclides reported in surface soil, concrete and asphalt above MDCs were Cs-137 (at levels consistent with fallout from historic worldwide nuclear testing) and naturally occurring uranium isotopes (U-233/234, U- 235/236 and U-238).

Additional information regarding the characterization of exterior ground surfaces including surface soils is summarized in Section 13.2.4.2, Exterior Ground Surfaces (Concrete, Asphalt & Soil).

Table 4-1: Background Concentrations of Licensed Radionuclides in Soil, Concrete & Asphalt

Radionuclide	Media Concentrations in pCi/g
	Off-Site Soil	On-Site Soil	Concrete	Asphalt
Cs-137	0.11-0.92	0.13-0.31	U	U
U-233/234	0.76	0.28	0.62	0.38
U-235/236	0.19	0.05	0.05	0.04
U-238	1.05	0.35	0.57	0.34

Notes:
U – Not identified > MDC
Uranium Isotopes – U-233/234, U-235/236, U-238

A summary of the maximum and average radionuclides activities in pCi/g in soil are summarized below in Table 4-2 (CN, 2021a).

Table 4-2: Concentrations of Licensed Radionuclides Detected in Surface Soil

Radionuclide	Concentrations in Site Soil (pCi/g)
	Min./Max.	Average	Background	Unrestricted Release Criteria1
Am-241	0.02-0.1	0.06	U	1.25
Cs-137	0.03-0.58	0.2	0.92	6.6
Pu-238	0.013a	0.013	U	1.52
Pu-239/240	0.018-0.036	0.028	U	1.37
U-233/234	0.574-1.16	0.72	0.76	7.8b
U-235/236	0.024-0.275	0.087	0.19	4.82
U-238	0.59-1.98	1.2	1.05	8.4b

Subsurface soil contamination identified at the following three locations (see Figure 2-1) will be addressed during Phase 3 decommissioning efforts:

• Cs-137 was identified in subsurface soil at the location of the former HRW. The maximum concentration of Cs-137 was reported at 7,960 pCi/g in a sample collected from 18-22 feet bgs (TIG, 2013). The average detected concentration of Cs-137 in subsurface soil is estimated at 963.7 pCi/g (CN, 2017). Background concentrations of Cs-137 in soil have been reported from 0.11 pCi/g to 0.31 pCi/g (CN, 2021a). The extent of Cs-137 impact remaining in subsurface soil has been estimated to extend four feet in the east-west direction, five feet in the north-south direction and from 6 to 24 feet bgs, centered on the location of the former HRW (CN, 2017). Details are summarized in the Soil Characterization Report for the HRW in Appendix D Part I and Appendix D Part II.
• Uranium ore was identified in subsurface soil at two locations, G95 and G140 (Figure 2-1), in Area 8 located near the former loading dock east of the Middle Building (CN, 2021a). Location G95 was beneath a crack in the asphalt. Location G140 was located inside of a former exterior storage shed. Removal of surface soil and asphalt at each location revealed uranium ore in soil at depths of greater than six inches bgs. The ore was observed to consist of black angular rock fragments with green and yellow discolorations exhibiting gamma readings of 425,000 cpm to 616,00 cpm using a 3X3 NaI(TI) probe and 3 mR/hr at six inches using a Ludlum Model 19. Excavations were advanced at each location to 1.5 feet in depth to remove black rock fragments and reduce gamma readings to approaching background (24,000 cpm). The maximum and average activities and ratios of radionuclides reported in the ore and in soil samples submitted for laboratory analysis and collected pre-excavation and post- excavation at G95 and G140 are summarized in Table 4-3. Comparison of radionuclide ratios in the ore indicate the ore is consistent with naturally occurring uranium ore. The concentrations of uranium isotope U-235 in post removal soil samples were reduced to levels below the NMED Volumetric Release Criteria (4.82 pCi/g). The concentrations of uranium isotopes U-234 and U-238 in soil post- excavation still exceed comparative screening criteria (7.8 pCi/g and 8.4 pCi/g, respectively) developed by CN for 15 mrem/yr using the same method of scaling used by NMED for the U-235 Volumetric Release Criteria.

Table 4-3: Uranium Ore in Soil Pre & Post-Removal

Isotope	Pre-Removal		Post-Removal
	Fraction (%)	Concentraton (pCi/g)	Fraction (%)	Mean Concentration (pCi/g)	Maximum Concentration (pCi/g)
	Location G95
U-233/234	48.0	14,300	50.0	27	43
U-235/236	2.6	786	1.9	1	2
U-238	49.4	14,700	48.1	26	42
	Location G140
U-233/234	50.3	196	47.8	24	42
U-235/236	2.7	11	2.6	1	3
U-238	47.0	183	42.7	25	43

Additional information regarding the characterization and remediation of subsurface soil is summarized in Section 13.2.4.2, Exterior Ground Surfaces (Concrete, Asphalt & Soil) and Section 13.2.4.3, Surveys of Subsurface Soil & Residual Impacts from Cs-137 at the Former HRW.

There are no surface water bodies present at the site (USGS, 2022). In addition, there is no complete pathway for impacts in subsurface soil on site to migrate to off-site surface waters since groundwater is not impacted. As such, no sampling or analysis of licensed radioactive materials in surface water at the site has been conducted with the one exception noted below. Based on site characterization completed in support of site decommissioning, there is no reasonable likelihood for impacts to surface waters off-site from licensed radioactive materials at the site.

At the request of NMED, a sample of surface water was collected March 22, 2022 from Nichols Reservoir located 14 miles to the east and upgradient of the site. Analysis of the surface water sample by GEL Laboratories for target licensed radioactive materials at the site indicated no radionuclides were detected above MDAs set by NMED (CN, 2022a).

An evaluation of groundwater quality on-site was completed by DBS&A and CN in 2024 that included the advancement of six soil borings to 365 feet to below the water table, installation of six monitoring wells MW-1 through MW- 6 (Figure 3-11), soil and groundwater testing for licensed radionuclides and well gauging.

Radiochemical analysis of 16 soil samples collected from borings and 17 groundwater samples indicated that the radionuclides reported in soil and groundwater were limited to uranium (U-234, U235 and U-238) and decay chain isotopes of uranium and thorium originating from naturally occurring uranium and do not originate from a release of licensed RAM at the site.

Total uranium concentrations reported in each well are summarized in Table 4-4 monitoring events in picocuries per liter (pCi/L) and microgram per liter (ug/L) for comparison with the Maximum Contaminant Level (MCL) for total uranium in drinking water of 30 ug/L. Total uranium concentrations approach but are below the MCL in MW-3 and MW-6.

Table 4-4: Total Uranium Reported in Site Groundwater

August 2024	Total Uranium in Site Groundwater
	MW-1	MW-2	MW-3	MW-3 Duplicate
Total U (pCi/L) – Range 3 Samples	1.85 – 2.77	1.3-3.9	22.4-26.4	21.7-24.2
Total U (ug/L) – Range of 3 Samples	2.1-3.1	1.4-4.3	24.9-29.3	24.1-26.9
MCL = 30 ug/L	< MCL	<MCL	<MCL	<MCL
September 2024	MW-1	MW-2	MW-3
Total U (pCi/L)	2.51	4.18	26.7
Total U (ug/L)	2.8	4.6	29.7
MCL = 30 ug/L	< MCL	<MCL	<MCL
Total U (pCi/L)	MW-4	MW-5	MW-5 Duplicate	MW-6
	1.87	10.7	15.1	26.9
Total U (ug/L)	2.1	11.9	16.8	29.9
MCL = 30 ug/L	<MCL	<MCL	<MCL	<MCL

Note: Conversion of pCi/L to ug/L based on 0.9 MCL factor per Federal Register National Drinking Water Regulations, USEPA December 7, 2000.

The presence of uranium in soil and groundwater in the Santa Fe area is well- documented as being derived from geologic deposits (granites, veins, volcanic ash, etc.) that comprise the Tesuque Formation (NMED, 2017), the primary source of groundwater utilized as drinking water. Results of a study by NMED in 2017 indicated that the levels of naturally occurring uranium in groundwater in the Santa Fe area exceeded the MCL of 30 ug/L in 55 percent of the locations evaluated.

The distribution of uranium in groundwater from natural sources reported by NMED in 2017 is consistent with the range and variability in uranium concentrations reported in groundwater on site. The results confirm that uranium in site groundwater is naturally occurring groundwater, confirm no evidence of impact to groundwater beneath the site from licensed RAM and support classification of the site decommissioning group as Group 4 in accordance with NUREG-1757.

Sampling and testing of the two closest nearby water supply wells (Shalom Trailer Park and Asi La Mar Trailer Park, (Figure 3-5) to the site and the Nichols Reservoir was completed by CN in coordination with NMED in March 2022 (CN, 2022a).

The results of testing indicated no evidence of impact from licensed radioactive materials from the site in groundwater tested. Uranium (and decay by-products) were detected in groundwater at each of the two well locations tested and are attributed to naturally occurring uranium in groundwater, well documented to exist within the Tesuque Formation and are not associated with the site (NMED, 2017).

A summary of radionuclides reported in the water testing results, including the maximum and average concentrations in pCi/L are summarized in Table 4-5.

Table 4-5: Radionuclides Detected in Groundwater Off-Site

Isotope	Average Concentration (pCi/L)	Maximum Concentration (pCi/L)
Bismuth-214	32.85	41.8
Lead-214	20.93	25.8
Uranium-233/234	0.92	1.17
Uranium-238	0.28	0.395

In accordance with NMAC 20.3.4.426 (NMAC, 2009), “Radiological Criteria for License Termination, Part B, Radiological Criteria for Unrestricted Release:”

“A site will be considered acceptable for unrestricted use if the residual radioactivity that is distinguishable from background radiation results in a TEDE [Total Effective Dose Equivalent] to an average member of the critical group that does not exceed 25 millirems (0.25 millisievert) per year [25 mrem/year], including that from groundwater sources of drinking water, and the residual radioactivity has been reduced to levels that are ALARA [As Low As Reasonably Achievable]. Determination of the levels which are ALARA must take into account consideration of any detriments, such as deaths from transportation accidents, expected to potentially result from decontamination and waste disposal.”

At the direction of NMED, the Licensee adopted a TEDE of 15 mrem/yr as a conservative dose threshold 40 percent lower than that required by state and federal regulation (25 mrem/yr). The adoption of the 15 mrem/yr TEDE is intended to provide a more protective level of cleanup and added confidence to NMED and the public that site restoration will not only meet, but exceed, regulatory standards for protection of the public and safe future use of the property following license termination.

The NMED issued Building Surface and Volumetric Release Criteria as action limits for target licensed RAM at the site for use by the Licensee to demonstrate compliance with a 15 mrem/yr dose threshold for the building and its contents (Table 5-1) (NMED, 2019).

The NMED action limits were adopted from the NRC default screening criteria listed in NUREG-1757, Volume 1, Appendix B for 25 mrem/yr and scaled lower to meet the 15 mrem/yr TEDE for the site without modification of the “DandD” (an NRC model) default assumptions used to develop the NRC screening criteria. In instances where radionuclides were detected for which NMED action limits had not been issued (e.g., for U-234 and U-238), CN developed comparative release criteria by scaling the default criteria for 25 mrem/yr (NRC, 2001) to 15 mrem/yr consistent with NMED RCB action limits issued for 15 mrem/yr.

Table 5-1: NMED RCB Recommended Building Surface & Volumetric Release Criteria

Nuclide	Surface Release Criteria (dpm/100cm2) Removable or Fixed	Volumteric Release Criteria (pCi/g)	Minimum Detectable Activity (MDA pCi/g))
Alpha Emitters
Am-241	17	1.25	0.05
Pu-239	17	1.37	0.05
Pu-238	19	1.52	0.05
U-235	59	4.82	0.05
Cm-244	30	2.5	0.05
Np-237	14	0.6	0.05
Cf-252	52	4.12	0.05
Beta/Gamma Emitters
H-3	1.14E+08	64.80	1.0
C-14	2.22E+06	6.96	1.0
Sr-90	4.67E+03	1.03	0.1
Cs-137	1.68E+04	6.60	1.0

Source: NMED RCB December 6, 2019 Letter of Clarification to Company RSO (NMED, 2019).

In accordance with NUREG-1757, a Group 4 site requires the use of site- specific dose modeling. The approach the Licensee has employed for site- specific dose modeling is outlined below and follows NUREG-1757, Volume 2, Revision 2, Appendix I (NRC, 2022). The Licensee will satisfy dose modeling requirements by identifying site-specific DCGLs for each licensed radionuclide of concern and completing a FSS to establish that the DCGLs have been met. The use of DCGLs is intended as a conservative approach to modify default screening criteria to account for site-specific conditions and planned remedial activities to be completed during site decommissioning.   

Considerations supporting the adoption of this approach include:

• Site restoration will include the removal and off-site disposal of buildings, foundations, concrete, and asphalt surfaces to restore the site to the existing soil surface. As such, no buildings or structures will remain at the site. Site characterization has confirmed that buildings, foundations (except a small portion adjacent to the Cs-137 release area), concrete, asphalt and surface soil are not impacted by licensed RAM. Buildings will be removed to the foundation under Phase 1 decommissioning. Foundations (except the small portion adjacent to the Cs-137 release area), concrete and asphalt will be removed during Phase 2 decommissioning. Soil beneath the foundations and asphalt will be characterized following removal during Phase 2 decommissioning. Any impacts to surface soils discovered during Phase 2 decommissioning, if present, will be posted, stabilized, and will be removed during Phase 3 decommissioning.
• Impacts from licensed RAM are limited to a small portion of the foundation adjacent to the Cs-137 release area and subsurface soil (soil that is greater than six inches (15 centimeters) in depth as defined under MARSSIM) in three locations. The Licensee proposes to remove the impacted portion of the foundation and all impacts to subsurface soil from licensed RAM to levels consistent with background to the extent feasible during Phase 3 decommissioning. As such, residual concentrations of licensed RAM in site soil are not expected to exceed background concentrations following the completion of site restoration.
• If restoration of site soil to background concentrations is infeasible, the Licensee proposes to utilize site-specific DCGLs set to a dose criterion for unrestricted release of 15 mrem/yr. To demonstrate compliance with background and/or a 15 mrem/yr dose criterion, a FSS of the site will be completed incorporating the results of post- remedial soil and groundwater testing.
• DCGLs are proposed for buildings, concrete foundations, asphalt, and surface soil based on the adoption of NMED Surface and Volumetric Release Criteria for licensed RAM meeting a TEDE of 15 mrem/yr. These criteria are adopted as intentionally conservative release criteria set at a dose threshold 40 percent below that required by NMAC (e.g., 25 mrem/yr) for unrestricted release. The adoption of this reduced threshold is intended to provide added confidence that the level of site restoration achieved is protective of future use of the property.

NMED Release Criteria utilize default generic exposure scenarios for Building Occupancy and a Resident Farmer. These default exposure scenarios incorporate consideration of exposure pathways to residual contamination on building surfaces and in surface soils but exclude the consideration of residual contamination in subsurface soil. The adoption of these default criteria as the basis for site DCGLs requires one important modification in the exposure assumptions, that is, to validate their application to site-specific conditions applicable to subsurface soil. This proposed modification is described in the following section.

As described in Appendix I, NUREG-1757, Volume 2, Revision 2, Section I.3, Criteria for Selecting and Modifying Exposure Scenarios, Pathways and Critical Groups, I.3.3.2 Site-Specific Analyses:

“Site-specific analyses can use the generic screening exposure scenario(s) with little justification…If site or source features are found to be incompatible with exposure scenario assumptions, the licensee should justify why the generic exposure scenario are nonetheless appropriate for use in the dose modeling.”

The NMED Surface and Volumetric Release Criteria are based on the adoption of the Building Occupancy and Resident Farmer (i.e., generic) exposure scenarios. Table 5-2 below (adopted after Table I.2 Appendix I, NURGE-1757, Volume 2, Revision 2) summarizes the pathways used under these generic exposure scenarios:

Table 5-2: Pathways for the Generic Exposure Scenarios

Building Occupancy Exposure Scenario

This exposure scenario accounts for exposure to fixed and removable residual radioactivity on the walls, floor, and ceiling of a decommissioned facility. It assumes that the building may be used for commercial or light industrial activities (e.g., an office building or warehouse). Pathways include the following: External exposure for building surfacesInhalation of (re)suspensed removable residual activityInadventent ingestion of removable residual radioactivity

Resident Farmer Exposure Scenario

This exposure scenario accounts for exposure involving residual radioactivity that is initially in surface soil. A farmer moves onto the site and grows some of his or her diet and uses water tapped from the aquifer under the site. Pathways include the following: *External exposure from soil *Inhalation to (re) suspensed soil *Ingestion of soil *Ingestion of drinking water from the aquifer *Ingestion of plant product grown in contaminated soil, using aquifer water to supply irrigation needs *Ingestion of animal products grown on site (using feed and water derived from potentially contaminated sources) *Ingestion of fish from a pond filled with water from the aquifer

Adoption of the NMED Surface and Volumetric Release Criteria as DCGLs for the release of building foundations, concrete and asphalt is consistent with the generic exposure assumptions for the Building Occupancy pathway, yet conservative since these materials will no longer remain at the site to contribute to a dose as they will be dispositioned for off-site recycling and/or disposal as construction and demolition debris.

Adoption of the NMED Volumetric Release Criteria as DCGLs for the release of surface soil (i.e., defined under MARSSIM as soil from the ground surface to less than six inches in depth) is consistent with the generic exposure pathways and assumptions for the Resident Farmer Scenario.

However, the Resident Farmer Scenario does not address subsurface soil. This condition poses a limitation in the application of screening criteria to subsurface soil since the conceptual model and parameters used in the development of the screening criteria do not account for subsurface soil.

NUREG-1757, Section 6.6.4, Qualifications of the Site for Screening, indicates, “situations do exist where you can still use the analyses using scenario assumptions to modify the source term. For example, by assuming buried radioactive material is excavated and spread across the surface, the screening criteria may be applicable for use at the site.”

Consistent with the above guidance, the Licensee proposes to modify the source term by assuming that subsurface soil is relocated by excavation and spread at the ground surface in the upper six inches and rendered available to exposure under a future Resident Farmer Scenario. This assumption is overly conservative for site conditions since subsurface soil will remain in the subsurface and the site is not likely to be utilized for farm use. However, employing this assumption renders the use of the NMED Volumetric Release Criteria consistent with the Resident Farmer Scenario for the purpose of demonstrating the subsurface soil meet criteria protective for release without restriction in site use.

The Licensee proposes to demonstrate compliance with the 15 mrem/yr TEDE by:

• achieving cleanup to background where feasible, and/or;
• meeting site-specific DCGLs for target radionuclides of concern (ROCs) adopted from NMED Surface and Volumetric Release Criteria and NRC default screening criteria modified only for the source term by assuming subsurface soil is excavated and rendered accessible at the surface to enable adoption of the Resident Farmer Scenario applicable to site-specific conditions.

The adoption of the generic screening exposure scenarios for the Building Occupancy and Resident Farmer are intended to provide NMED and the public with a high degree of confidence in demonstrating compliance with the license termination release criteria of 15 mrem/yr. In accordance with NUREG-1757 Volume 2, Revision 2 (NRC, 2022), Section 5.3.2 for Decommissioning Group 4, the site-specific dose analysis for the site is based on:

• The source term reflects the parameters adopted for the generic screening criteria used in the DandD model with the exception that subsurface soil is assumed to be excavated and spread on the surface of the site and thereby available for exposure by a future resident farmer.
• ROCs include the target licensed radionuclides listed in Section 5.1 for which NMED had developed surface and volumetric release criteria set to a 15 mrem/yr TEDE. Added to this list are U-234 and U-238 for which CN has developed DCGLs using scaling the default criteria for 25mrem/yr to a 15 mrem/yr TEDE consistent with NMED Surface and Volumetric Release Criteria.
• Site characterization has confirmed no impacts from licensed RAM at the site to buildings, concrete, asphalt, surface soil or groundwater. Impacts from licensed RAM at the site are limited to:
  • Potential impacts exceeding DCGLs are assumed for the concrete foundation immediately adjacent to the former HRW where remediation of Cs-137 had been conducted. Detected impacts to the concrete foundation in this area are reported at levels below the DCGL for Cs-137. This portion of the foundation will remain in place during the work performed under Phase 1 and Phase 2 decommissioning and be removed under Phase 3 work.
  • Cs-137 from a breached Cs-137 source exists in subsurface soil extending over an area estimated at four by five feet laterally and vertically from six to 24 feet bgs centered on the former HRW. The breeched source was removed during prior well removal efforts in 2010 (ERM, 2011). An estimated 69 percent of the soil impacts adjacent to the former HRW were addressed through soil removal work in 2012 (TIG, 2013). The remaining impacts to subsurface soil will be secured and remain in place during the work proposed under Phase 1 and Phase 2 decommissioning and be addressed under Phase 3 work.
  • Two locations contain residues from naturally occurring uranium ore in subsurface soil to 1.5 feet in depth near the former loading dock (G95 and G140 (CN,2021a)). The origin of the uranium ore is unknown but has been determined by analysis to be consistent with naturally occurring. The ore has been removed under prior work (CN, 2021a). The remaining impacts to subsurface soil are posted and secured and will remain in place during the work proposed under Phase 1 and Phase 2 decommissioning and be addressed under Phase 3 work.
• Site remediation during decommissioning will target removal and off-site disposal of concrete and soil impacted by licensed RAM to background levels, where feasible. In instances where remediation to background is infeasible, restoration will seek to meet DCGLs set to 15 mrem/yr for individual ROCs. The critical group for potential future exposure to soil is the Resident Farmer.
• There is no evidence of impact to site groundwater from licensed RAM (DBS&A, 2025). The potential for impact to groundwater is judged to be extremely low based on: 1) the limited depth extent of Cs-137 impact (to less than 25 feet bgs); 2) the depth to groundwater at 331 to 336 feet; 3) the presence of shallow and massive (100+ foot thick) dense clay deposits between residual soil impacts and groundwater representing barriers to vertical migration to groundwater; and 4) the high affinity for Cs-137 to adhere to clay- rich soil such as those at the site and thereby retard migration in a dissolved phase (EPA, 2018). Therefore, the Resident Farmer pathway for ingestion of impacted groundwater is incomplete and eliminated. Groundwater testing will be conducted on site following soil remediation as an element of Phase 3 site decommissioning to provide added confirmation of the lack of impact from licensed RAM to groundwater.
• DCGLs are based on default screening criteria for generic Building Occupancy and Resident Farmer land use scenarios using DandD. The only modifications of the models or input parameters has been limited to adoption of a 15 mrem/yr TEDE and modification of the source term for soil to assume that subsurface soils are relocated on the ground surface so they would be available to a future Resident Farmer.
• The approach employed in the adoption of DCGLs for the site is intentionally conservative to provide an added factor of safety and account for uncertainties. Conservative assumptions include: 1) DCGLs derived for a 15 mrem/yr TEDE; 2) the use of the default Building Occupancy Scenario when under actual conditions all buildings will be removed from the site and not available for future occupancy; and 3) modification of the source term for subsurface soil to assume that it is relocated to the ground surface when under actual conditions the soil will remain in the subsurface and not be available for exposure by a future Resident Farmer.

Site-specific DCGLs proposed for site buildings and soil are summarized below in Table 5-3.

Table 5-3: Site-Specific DCGLW’s for Building Materials & Soil

Radionuclide	Surface Release Criteria (dpm/100cm2) Removable or Fixed Applicable to Building Materials Surfaces	DCGLw Volumteric Release Criteria (pCi/g) Applicable to Building Materials & Soil
Alpha Emitters
Am-241	17	1.25
Pu-239	17	1.37
Pu-238	19	1.52
U-234	59	7.8
U-235	59	4.82
U-238	59	8.4
Cm-244	30	2.5
Np-237	14	0.6
Cf-252	52	4.12
Beta/Gamma Emitters
H-3	1.14E+08	64.80
C-14	2.22E+06	6.96
Sr-90	4.67E+03	1.03
Cs-137	1.68E+04	6.60

The proposed DCGLw is equivalent to the concentration of a single radionuclide from a single source that, if distributed uniformly across a survey unit, would result in a dose of 15 mrem/yr. In the event that restoration achieves background then employment of the DCGLw is not necessary. Site buildings, foundations (except the area adjacent to the Cs- 137 release) and asphalt have been shown to meet either background concentrations or the DCGLw and will be removed, reduced in size, screened to confirm the construction and demolition (C&D) wastes are non- impacted, and following confirmation, released for off-site disposal and/or recycling as non-impacted C&D waste.

Surface soil on site has been shown to meet either background concentrations or the DCGLw. Surface soil located beneath concrete foundations and asphalt will be characterized following foundation and asphalt removal to confirm that the concentrations of target licensed radionuclides remaining in soil meet background concentrations or the DCGLw. In the event that surface soils beneath concrete and asphalt are found to exceed the DCGLw for target licensed radionuclides, removal will be completed under Phase 3 decommissioning work to restore surface soil to background and/or to meet the DCGLw.

Similarly, subsurface soil will be restored to background and/or the DCGLw. In the event that residual concentrations of more than one licensed radionuclide remains in surface or subsurface soil at levels above background but below the DCGLw, then compliance with the DCGLw will be based on demonstrating compliance with the sum of the fractions rule whereby the dose from each radionuclide for each source will be added together to confirm that the resulting dose for all sources and licensed radionuclides meet the 15 mrem/yr TEDE.

Compliance with the DCGLw will be established for each licensed radionuclide above background within each survey unit under the procedures established for the FSS under Phase 3. The DCGLw will be calculated as the average concentration of the licensed radionuclide above background across the survey units to be defined in the FSS (see Section 13.4). A DCGLEMC, an elevated measurement comparison, will be employed in accordance with MARSSIM guidance in smaller areas of elevated activity within the survey unit, if applicable.

In accordance with NMAC 20.3.4.7., DEFINITIONS G. “ALARA” (acronym for “as low as is reasonably achievable”) “means making every reasonable effort to maintain exposures to radiation as far below the dose limits in these regulations as is practical, consistent with the purpose for which the licensed or registered activity is undertaken, taking into account the state of technology, the economics of improvements in relation to state of technology, the economics of improvements in relation to benefits to the public health and safety and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and licensed or registered sources of radiation in the public interest.”( NMAC, 2009).

In accordance with NMAC 20.3.4.426.B, Radiological Criteria for Unrestricted Use, “A site will be considered acceptable for unrestricted use…and the residual radioactivity has been reduced to levels that are ALARA. Determination of the levels which are ALARA must take into account consideration of any detriments, such as deaths from transportation accidents, expected to potentially result from decontamination and waste disposal.” (NMAC, 2009).

The Licensee proposes to achieve a decommissioning goal below the required dose limit of 25 mrem/yr by:

• Removal and off-site disposal of all buildings and contents.
• Removal and off-site disposal of all soil impacted by licensed radionuclides at levels exceeding background, to the extent feasible, and where infeasible to meet DCGLs that meet a TEDE of 15 mrem/yr.
• Performance of a FSS to demonstrate that the radiological status of the site following the implementation of remedial measures has achieved background, to the extent feasible, and/or meets a TEDE of 15 mrem/yr, significantly below the 25 mrem/yr standard regulatory requirement.

The projected schedule for site decommissioning is included in the Gantt chart below (Table 7-1). The schedule is based on consideration that NMAC 20.3.3.318.I. Deadline for Decommissioning (2) requires that “when decommissioning involves the entire site, the Licensee shall request license termination as soon as practicable but no later than 24 months following the initiation of decommissioning.” (NMAC, 2009). In order that the Licensee request termination within 24 months of the initiation of site decommissioning, the following milestones must be completed:

• The Licensee must obtain NMED approval of the DP, and the license must be amended to incorporate the DP.
• The Licensee must complete all three phases of site decommissioning work proposed including post-remedial surveys and testing and FSS to demonstrate compliance with the 15 mrem/yr TEDE for unrestricted use.
• The Licensee must file a DR with NMED documenting the completion of all decommissioning tasks outlined in the DP demonstrating compliance with the 15 mrem/yr TEDE for unrestricted use and the certifications required under NMAC 20.3.318.H.

The projected decommissioning schedule below assumes NMED approval of the DP by December 2025 to enable the initiation of decommissioning work in January 2026. The schedule projects the majority of field work being completed in 2026 followed by completion of the FSS and reporting in 2027 to achieve completion of license termination with the 24 months required under NMAC 20.3.3.318.I. Circumstances could require modification of the proposed site decommissioning schedule.

The Licensee will keep NMED updated of potential modifications in the schedule as needed. In the event that site decommissioning cannot be completed within the 24-month period as required under NMAC 20.3.3.318.I, the Licensee will notify NMED in advance of the 24-month deadline expiring and file a request for an alternative schedule.

TABLE 7-1: Projected Site Decommissioning Schedule