The radionuclides, forms and maximum quantity (as the activity limit that may be possessed at any one time) are summarized below in Table 2-1 as listed in Attachment 1- Radioactive Material Specifications for License No. SO067-36 (Appendix A).

TABLE 2-1: Currently Licensed Radionuclides, Forms & Maximum Quantities (pdf)

Under License Condition 9, Authorized Uses include:

• Items A. and B. Storage Only. For handling of licensed material for disposal.
• Items C. through K. As a contingency if radioactive material was discovered during the scoping survey and sampling process of previously licensed materials.

There is no current use of licensed radionuclides at the site under this license. The use of licensed radionuclides at the site ceased when principal manufacturing operations at the site were discontinued in June 2007. The process of removing all licensed radioactive material, sending the materials to other licensed facilities for productive use, or to licensed disposal sites began in 2007 and was largely completed by 2016. The only licensed radionuclides remaining at the site that require cleanup are residual impacts to soil from a past release of Cs-137 formerly located within the High Range Calibration Well (HRW) located in the former Calibration Source Room and residues of naturally occurring uranium ore in soil at locations G95 and G140 (Figure 2-1).

No amendments to License SO067-36 have been made since renewal on December 20, 2022.

Radionuclides, forms, maximum activities authorized, used under all previous licenses, and ultimately dispositioned by the Licensee as part of the site decommissioning process are summarized in Appendix B, Thermo Eberline LLC, Inventory Report.

The Inventory Report in Appendix B utilized License No. CS067-25 (Amendment 25) (TE, 2006), because it was the license in effect when: 1) the Licensee ceased principal manufacturing operations and initiated transition into the decommissioning process; 2) NMED issued a Settlement Agreement and Stipulated Final Order RCB 07-015 (August 7, 2007) (NMED, 2007a&b), affirming the Licensee’s records of receipt and transfer of all radioactive materials were satisfactory.

Amendments subsequent to No. 25 removed line items from the license but did not add any additional items or were administrative amendments.

The radioactive sources and materials used were of several types including (CN, 2022c):

• millicurie to curie quantity encapsulated (i.e., sealed) sources stored in the deep shielded “wells”;
• “stick” or low-level photon sources mainly using Cs-137 or Cobalt- 60 (Co-60) radionuclides;
• electroplated alpha or beta-gamma sources and metallic uranium sources used for precise beta emission rates; and
• uranium and thorium in oxide forms

The radiation sources and radioactive materials were used to:

• determine the minimum detectable activity (MDA) or concentration that a given radiation detection system could measure;
• check for the proper radiation response of an instrument or system over time; and /or
• calibrate or recalibrate a radiation detector or system for linearity, precision, or accuracy

Calibration sources were generally in sealed form, except for sources that were used historically for calibration of liquid or gas monitoring instruments.

Two exceptions to the normal use of radioactive material described above are as follows. First, approximately 8.6 Curies (Ci) of unsealed Americium 241 (Am-241) was licensed for storage only pending disposal under line MM on License CS067-25:

“For storage in 7 each 2R containers with each container located in a 6M Type B container pending disposal.”

The Am-241 described above was never used at the site but was transferred from the Eberline facility in Albuquerque for storage. The Am-241 was stored in multiple encapsulated steel containers located within a High Integrity Polyethylene Container (HIC) from November of 2000 until February of 2016. The material was transferred to Los Alamos National Security, LLC (LANS) for recovery and disposal on February 21, 2016 (CN, 2022c).

Second, in November 2007, a Cs-137 sealed source was discovered to be breached at the bottom of the HRW during the planned removal of sources from the calibration wells for disposal (CN, 2022c).

Locations within the facility where facility employees indicated radioactive materials were used, stored and/or released based on employee interviews (CN, 2022c) are listed below by building and shown on Figure 2-2.

• Laboratory and Calibration Areas (North Building)
• Engineering Source Storage Closets (North Building)
• Radiation Source Storage Room (Middle Building)
• Shipping and Receiving Areas (North and South Buildings)
• Dosimetry Trailer (Adjacent to East Side of South Building)
• Customer Service Areas/Production Floor (South Building)
• Calibration Well Room (South Building)

Areas of the site where spills, burials and/or releases of licensed radioactive materials occurred and were remediated are summarized in Figure 2-1. The following sections summarize the types, forms, activities and concentrations of radionuclides released, if known, the cause of the release, if known, the remedial measures implemented, remedial waste dispositioned, and results of the final radiological evaluation for each of the remedial areas.

All identified impacts from licensed radioactive materials presented in this section have been addressed and wastes properly disposed of off-site with the exception of residual soil impacts from Cs-137 at the former HRW and residues of naturally occurring uranium in soil at locations G95 and G140 (Figure 2-1). Additional details are summarized in documents referenced in the Final Historic Site Assessment Report (HSA) (CN, 2022c).

An interoffice memorandum dated November 13, 1970 indicated two small vials containing approximately 1 microcurie (uCi) of tritium (H-3) were broken on the production floor (Eberline, 1970). The spill was reportedly cleaned up immediately and waste materials properly disposed.

Wipe samples collected after cleanup indicated less than 3E-05 uCi on the floor. Urine samples of the employees involved in the incident also indicated less than 3E-05 microcurie per milliliter (uCi/ml) in urine. The former production area (Figure 2-2) was subject to survey and sampling during characterization of the building and indicated that the levels of residual tritium contamination detected were below applicable NMED RCB Release Criteria (NMED, 2019 & CN, 2022b).

Interviews with employees (see HSA, CN, 2022c) indicated a spill of C-14 in the dosimetry trailer located along the east side of the South Building (Figure 2-2). The date of the incident is unknown but reportedly occurred between 1976 and 1979. The quantity of C-14 released is unknown.

Typically, the use of C-14 associated with dosimetry included minor quantities. The license active in 1977 (License Number NM-EBE-BL-00) indicated that the Eberline Albuquerque and Santa Fe facilities were authorized for a combined limit of 20 millicuries (mCi) of C-14. The spill was reported and cleaned up, but employees indicated that C-14 could have been tracked outside the trailers and into the South Building. The trailers were removed at an unknown date.

Characterization of the building and ground surfaces in and around the former location of the trailers by CN indicated no evidence of residual C-14 above background on building surfaces or in soil (CN, 2022c).

Loose Cs-137 contamination was discovered by the Licensee in August 2007 during the unloading of sealed sources stored within calibration wells (Figure 2-2). Subsequent evaluations indicated a source had fallen to the bottom of the HRW and removable contamination was found in the well (TE, 2008). The source that had fallen to the bottom of the HRW was then suspected, and later confirmed by CN, to have been a 16 Ci Cs-137 source.

The breeched source was encapsulated in concrete in the bottom of the HRW, recovered during removal of the well in 2010 and shipped to a licensed off-site disposal facility (ERM, 2011). Upon removal, the steel well casing was found to be corroded with a breech in the casing at an estimated 12 feet below ground surface (bgs). Cs-137 was found in soil adjacent to the well at a concentration of 1,220 picocuries per gram (pCi/g) (ERM, 2011).

In 2012, removal of an estimated 11.8 cubic yards (cyds) of Cs-137 contaminated soil was completed by a combination of shallow excavation to eight feet and auguring within the footprint of the former HRW to a depth of 24 feet below grade (TIG, 2013). The Cs-137 impacted soil removed was shipped to a licensed off-site disposal facility. Sampling following removal indicated residual concentrations of Cs-137 remaining in soil up to 7,960 pCi/g.

In 2017, a detailed characterization program was implemented including the advancement of 30 soil borings within a 6×6 foot area surrounding the former HRW. Continuous soil cores and sampling were completed to define the remaining extent of residual Cs-137 impact in soil (Appendix D).

Residual impacts were defined to extend from the center of the former HRW outward and to be contained within an area estimated at four feet in width in the east-west direction and five feet in length in the north-south direction. The vertical extent of impact was estimated to extend from six to 24 feet bgs. The total volume of residual soil impact remaining in place was conservatively estimated at just under 20 cyds (CN, 2017). This area has been covered, posted, regularly inspected, and access restricted pending remediation during decommissioning.

Dade Moeller & Associates (DMA) completed scoping surveys of the facility walls, floors, workspaces, materials and equipment and reported the following five (5) locations (Figures 2-1 and 2-2) of isolated radioactive contamination that were decontaminated, contained for disposal, or contained and labeled for future abatement (DMA, 2008), including:

• Source Well Calibration Room- Loose gamma activity was identified at two locations on well shield blocks and cleaned to background. Loose gamma activity associated with Cs-137 was found on the floor near the HRW, sealed with tape and subsequently removed and disposed. Elevated activity was identified within the HRW based on dose surveys over the top well opening.
• Production Floor- A section of electrical conduit that had reportedly been used to probe the HRW was identified adjacent to the Source Well Room exhibited elevated gamma activity associated with Cs-137 The conduit was wrapped in tape and disposed of off-site.
• Radioactive Materials Storage Room- Elevated beta/gamma activity were identified on the exterior of two source storage containers (pigs) and contained for disposal. One table surface and a plastic bottle of white powder were found to be contaminated with alpha activity and disposed of off-site. The top of one wax barrel (typically used to store neutron sources) was found to exhibit removable gamma activity and disposed of off-site.
• Radioactive Source Closet- Elevated beta/gamma activity was identified on the interior of two pigs that were contained and disposed of off-site.
• Engineering Annex- Rubber mats were found to contain elevated fixed activity and were bagged and subsequently disposed of off- site.

The locations of elevated activity were addressed by DMA and/or the Company by decontamination and/or containment for disposal.

Two exceptions included: 1) the 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 2) elevated activity within the HRW (DMA, 2008).

The elevated activity on the floor under tape was addressed by the Company Radiation Safety Officer (RSO) prior to calibration well removal in 2010. The elevated activity within the HRW was addressed during the HRW removal in 2010 (ERM, 2011).

In late 2020, CN completed a series of radiation surveys and testing of exterior ground surfaces (soil, asphalt and concrete) over all accessible exterior areas of the site (CN, 2021a). The site was divided into 10 survey areas, six adjacent to the buildings and four along the boundaries of the site (Figure 13-1).

Elevated radioactivity from ground surface surveys was confirmed at only two locations (G95 and G140) in Survey Area 8, the Exterior Storage Area located to the east of the Middle Building/Loading Dock (Figure 3-2).

Location G95 correlates with a crack in the asphalt in Survey Area 8. Location G140 was located within an unpaved area inside of a shed located along the north wall of the South Building.

Further evaluation of G95 and G140 was completed by manual removal of asphalt, soil excavation, soil screening and collection of samples for laboratory analysis. The asphalt removed at location G95 did not indicate activity above reference background. However, total gamma readings of excavated soil beneath the asphalt crack at G95 were up to 37,000 counts per minute (cpm). Pieces of black rock fragments in soil beneath the pavement with green and yellow discolorations (characteristic of naturally occurring uranium ore) indicated gamma activity up to 850,000 cpm on contact using a using a 3”x3” Sodium Iodide Detector (NaI(Tl)).

Similarly, soil excavated from an estimated six inches below the ground surface at G140 exhibited total gamma readings up to 425,000 cpm. Larger pieces of angular black rock fragments with green and yellow discolorations indicated total gamma readings up to 616,000 cpm using a 3”x3” NaI(Tl) or 3 milli-Roentgen per hour (mR/hr) on contact using a Ludlum Model 19 (micro-R meter).

Excavations were advanced at both G95 and G140 extending an estimated 2×2 feet in width and 1.5 feet in depth. An estimated 10.5 cubic feet (ft3) of impacted soil was removed, contained, and shipped to a licensed off-site disposal facility. Soil samples collected from the floor and four walls (north, south, east, and west sides) of each excavation were screened and found to exhibit gamma activity approaching, but distinguishable from, reference background (24,000 cpm). Samples of the angular black rock fragments with green and yellow discolorations and post-excavation soil samples from the walls and floor of the excavations at G95 and G140 were submitted for laboratory analysis of target licensed radionuclides.

Results of laboratory analyses of the angular black rock fragments with green and yellow discolorations and post excavation soil samples indicated the presence of uranium isotopes similar in composition to naturally occurring uranium ore. Removal of the ore reduced the level of impact to soil, however, residues of naturally occurring uranium isotopes U-233/234 and U-238 remain in soil at concentrations up to 43 pCi/g (above NMED Volumetric Release Criteria of 7.8/8.4 pCi/g, respectively). These areas have been covered, posted, and routinely inspected to ensure access is restricted pending remediation during decommissioning.

Meteorology is the science of atmospheric climate and weather. Meteorological characteristics of the site area can be important to the consideration of migration of potential radiological contaminants in the environment.

Santa Fe is located in the northern Rio Grande Valley of New Mexico, situated in the foothills of the Sangre de Cristo Mountain range. New Mexico in general has a mild, arid or semiarid, continental climate with associated characteristics of low precipitation totals, significant sunshine, low relative humidity, and a relatively large temperature range (annually and daily).

Meteorological data were derived primarily from the websites of the Western Regional Climate Center (WRCC, 2022) and the New Mexico Climate Center (NMCC, 2022).

Specific data were derived from weather stations in proximity to site, including the broadcast station KSAF weather station at the Santa Fe County Airport (approximately 2.5 miles west-southwest of the site), a weather station at the Santa Fe Police Academy (approximately 0.84 miles to the southeast), and the Santa Fe 2 Weather Station (approximately four miles northeast of the site).

Based on data collected between 1996 and 2006 at the KSAF weather station, the annual average wind speed is 9.5 miles per hour with the highest winds occurring during the months of April and May (NMCC, 2022). Prevailing wind direction, measured hourly at the KSAF station from 1992 to 2002, is from the north.

Climatological data were derived in the form of climate normals prepared by the National Climatic Data Center (NCDC) and evaluated from the WRCC website for the Santa Fe 2 Weather Station (WRCC, 2022). The normals are based on data collected between 1971 and 2000. The annual mean temperature at the weather station is 49.4° Fahrenheit (F) with a monthly mean range from 29.3°F in January to 69.8°F in July. The mean temperature ranges from 34.2 to 64.7°F on an annual basis.

Precipitation in the area is predominantly from brief thunderstorms during the months of July and August that account for approximately 30 to 40 percent of the annual total rainfall. This is supplemented by frontal events throughout the year linked in general to Pacific Ocean storm movement across the continent.

Data from the Santa Fe 2 Weather Station NCDC show that total precipitation averages 14.22 inches per year (WRCC, 2022). The lowest mean monthly precipitation (0.5 inches) occurs in February and the highest mean monthly precipitation (2.25 inches) is recorded in July (WRCC, 2022). Despite the mean normal values, it is not uncommon for a month to pass without any precipitation in the arid climate of Santa Fe.

An annual average snowfall of 19.4 inches was recorded for the Santa Fe 2 Weather Station between 1972 and 2007, with the highest averages measured in December (WRCC, 2022). Despite the positive average snowfall reported for all months from October to April, accumulation is limited and only January has a positive value for average snow depth.

The site lies outside the 100-year floodplain of the Santa Fe River (FEMA, 2022). Surface drainage at the site is to the west and south based on observed site topography and the topographic map provided as Figure 1-1.

Relative humidity information is presented for various New Mexico locations for both morning and afternoon by the WRCC. Although the data set does not include Santa Fe-specific stations, the relative humidity data for the City of Albuquerque (further south in the Rio Grande Valley) is considered conservatively high due to the lower elevation of Albuquerque.

The WRCC data show annual average relative humidity levels at 60 percent and 29 percent for the morning and afternoon time frames, respectively (WRCC, 2022). The lowest humidity measurements were recorded during the months of December and January while the maximum values occur during May and June.

As would be expected in an arid climate, evapotranspiration occurs at quite high rates. Pan evaporation data measured from 1972 to 2005 for the Santa Fe 2 Weather Station show an average annual evaporation of 60.22 inches (WRCC, 2022). No net evaporation is reported for the months of November through March. The highest monthly average is 11.31 inches in June (WRCC, 2022).

This section provides a summary of the site geology and seismology based on literature and site-specific information available in reports regarding geologic deposits encountered in soil borings advanced on the site. Geological information assists in defining the horizontal and vertical extent of potential subsurface radiological contamination, as well as the potential transport of contaminants to surface water or groundwater.

The primary physical feature describing the geology of the Santa Fe area is the Rio Grande Rift. The rift is an elongated series of north/south valleys that were formed as a result of the underlying earth’s crust spreading apart. The crustal spreading created a series of basins that extend from Colorado to Mexico.

The primary basin in the Santa Fe area is the Española Basin which is about 50 miles long and 18 to 40 miles wide, bounded to the north by the Santa Fe uplands and San Luis Basin, to the east by the Santa Fe and Sangre de Cristo Mountains, to the southwest by the Santo Domingo Basin and to the west by the Jemez Mountains (Land, 2016). The Española Basin is geologically complex and further divided into several sub-basins (Figure 3-6).

The Española Basin has been filled with sediments from erosional and depositional process occurring over millions of years, including fluvial (sediment deposited by rivers and streams); eolian (sediment deposited by wind); alluvial and colluvial (sediment deposited on mountain front slopes); lacustrine (sediment deposited in lakes); and volcanic (molten rock and ash from eruptions).

The sequences of these sedimentary deposits in the Española Basin have been categorized as belonging to the Santa Fe Group (Bartolino & Cole, 2002). The Santa Fe Group thickens from 250 feet south of Santa Fe to over 10,000 feet to the northwest. The basement granitic rocks of the Sangre de Cristo Mountains underlie the Santa Fe Group to the east, while limestone and volcanic rocks underlie the Santa Fe Group to the west (Land, 2016).

The Santa Fe Group geologic units include sediments and volcanic rocks deposited in the Rio Grande Rift, and like the rift valley, these sediments extend north to south through the central area of New Mexico. Lithology (rock type) consists primarily of siliciclastic sediments and volcanic rocks. The deposits within the upper portion of the Santa Fe Group are defined as the Ancha Formation and are comprised of granite-bearing gravel, sand and mud from the southwestern flank of the Sangre de Cristo Mountains (Koning, et. al, 2002). These strata are estimated to be less than 150 feet thick and comprise a locally important aquifer for private domestic water supply wells south of Santa Fe, but not in the area of the site. The Ancha Formation is underlain by the Tesuque Formation composed of a pinkish-tan silty sandstone with minor conglomerate and siltstone that are exposed to the north of the basin in the Santa Fe uplands. The Tesuque Formation is the primary water supply for the City of Santa Fe.

In the Santa Fe area near the site, the siliciclastic sediments are primarily comprised of eroded sediments derived from granitic and sedimentary rock sources in the Sangre de Cristo Mountains to the east. During the lower Oligocene to upper Pleistocene geologic periods (about 2 to 30 million years before present), the sediments were deposited in fluvial and alluvial depositional environments by the ancestral Santa Fe River system that flowed from the Sangre de Cristo Mountains to the ancestral Rio Grande (Koning and Read, 2010). Deposition occurred across a large drainage area leaving interbedded deposits of sand, silt, and clay.

The ancestral Santa Fe River created an alluvial fan along the mountain front with a series of stream channels that erode channels into existing sediments, depositing sediment within the channels. During periods of high stream flow, water would spill out of the river channels onto the flood plain. The suspended load of sediment would be deposited as overbank deposits, which are typically fine-grained and composed of mostly clay-size material. Some lakes and ponds also occurred in the area, and the lacustrine deposits associated with these features can be extensive. For example, Koning and Read (2010) document a 500-foot-thick clay-dominated sequence near Santa Fe Airport.

Around Santa Fe, the Tesuque Formation represents most of the basin-fill sediments of the Santa Fe Group consisting of silty-clayey sand and sand with lesser amounts of gravel, silt and clay (Spiegel and Baldwin, 1963; Johnson and others, 2016). The formation is consolidated and typically weakly to moderately cemented. The formation is divided into “lithosomes” that are defined based on similar lithology and depositional environments. The channel and floodplain deposits of the ancestral Santa Fe River system are known as lithosomes of the Tesuque Formation (Koning and Read, 2010).

Lithosome S is recognized by its typical “reddish color (particularly compared to the browner, distal alluvial slope facies of Lithosome A), and high-energy-flow deposits in very broad, thick channel complexes that possess very thin to medium, planar to lenticular internal bedding (Koning and Read, 2010).” The sediments are arkosic sands with granitic material being the most common.

Based on descriptions from Koning and Read (pages 21 to 23, 2010), the lithology of Lithosome S exhibits the following characteristics for channel and floodplain deposits:

• The channel sands are fine- to coarse-grained and commonly light brown. The channel units are typically connected, and the grain-size distribution tends to fine-upwards.
• The floodplain deposits include overbank and tributary channel deposits.
  • Mudstone: Mudstone amounts vary and when present are reddish brown, yellowish red, and light reddish brown sandy mudstone. Locally clay deposits reflect floodplain and some lake or pond deposition.
  • Sand and sandstone: The overbank sediments consist of light brown, reddish yellow, pink, and very pale brown siltstone, very fine- to coarse-grained (generally fine-grained) sandstone, and silty to clayey sandstone.
  • Sand and sandstone: Tributary units occur within the fine sediment and are typically fine- to coarse-grained sands in very thin to medium, lenticular channel-fills with individual beds up to 1 meter thick.

Geologic structures in the area include a regional fold and fault system. The Santa Fe Embayment is a large syncline that strikes north to south and extends from the Sangre de Cristo Mountains to the Cerrillos uplift; the Site lies on the eastern limb of the syncline. A series of faults, known as the Agua Fria Fault System, strike north to south and have displaced and tilted geologic units along the synclinal limbs.

The site geology is described below based on the results of several subsurface investigations involving the advancement of soil borings completed between 2009 and 2024 to depths of 365 feet bgs.

Soil boings were advanced on the site in 2009 beneath the South Main Building around the former calibration wells to a depth of approximately 40 feet bgs (ERM, 2009b). The subsurface deposits encountered in those borings were described to consist of the following sequence of unconsolidated deposits:

• Sand and silty, clayey sand, generally present from 0 – 24 feet bgs.
• Clay up to 4 and 4.5 feet thick, generally present around 24 feet bgs.
• Gravelly sand, generally present below the clay layer and continuing down to 40 feet bgs.

The soil conditions were described to be damp to moist, but not wet, indicating that groundwater was not encountered within any of the soil borings (up to 40 feet in depth).

In 2017, a series of 30 borings were advanced to a depth of 26 feet bgs within a 6×6 foot area surrounding the former HRW. Deposits encountered includes sand, silty, clayey sand and clay.

In 2021, a series of 28 shallow (5 to 10 feet bgs) soil borings were advanced to the east of the loading dock. Deposits encountered included loose soil, dense gray sandy clay and caliche, a very dense white to tan calcium carbonate deposit.

In 2024, six soil borings were drilled using the sonic drilling method to enable the collection of soil cores from the ground surface to a depth of 365 feet bgs and installation of six monitor wells on site. Soil samples were collected every 2 or 2.5 feet from the cores, providing highly detailed lithologic information. No indications of faulting were observed during drilling or subsequent analysis of the borehole information (DBS&A, 2025).

The lithology observed in drill cores matches the depositional environments typical of the Tesuque Formation, as expected (DBS&A, 2025). The alternating sand and clay layers were deposited in stream channels and floodplains of the ancestral Santa Fe River. In particular, the observed color and grain size of the core samples match descriptions of the Tesuque Formation for overbank deposits and associated tributary channels. An example cross section based on monitor wells MW-1 and MW-3 was constructed for the site (Figure 3-7). This section illustrates some important site-specific observations, including:

• The clay layer present at a depth of 24 feet in borings advanced in 2009 around the former calibration wells within the building was found to be continuous across the site.
• A second continuous clay layer was encountered at 40 feet bgs.
• A 90 to 100-foot sequence of clay-dominated sediments was encountered in each boring from about 135 to 225 feet bgs. These sediments include clayey sands, silty sand, and clay. These units match the descriptions of typical floodplain deposits in the Tesuque Formation.
• Near the water table at about 329 to 334 feet bgs, the lithology consists of interbedded sand and sandy clay units, interpreted to be tributary channel deposits that occur within overbank or floodplain deposits. The sands are fine- to coarse grained, brown and yellow colors with rounded grains. The clayey sands and clays are typical fine sand and clay and typically brown.
• An example of a brown sand occurs from 332 to 350 and 355 to 365 feet bgs in MW-2 and was observed in MW-1 and MW-3. The sand changes texture towards the north into clayey sands and sandy clays (e.g., MW-5) and towards the south the textures are silty and clayey sands (e.g., MW-4).

The structural geologic features of the Santa Fe area are the result of relatively recent geologic activity, Tertiary and younger. As discussed above, Santa Fe is located near the eastern boundary of the Española Basin, which is one of a number of interconnected basins that make up the Rio Grande Depression. The development of the basins is the result of continental rifting that initially began 29 million years ago and continues today.

The rifting that followed the early Tertiary Laramide orogeny and created the Sangre de Cristo Range to the east, is described by some as a continuation of Laramide deformation (Chapin, 1979). The extensional forces which followed the compression of the Laramide created a series of uplifts and associated down-dropped fault blocks of significant elevation differences, as evidenced in the thickness of basin-fill sediments along the Rio Grande Rift Zone (Chapin, 1979).

Fault zones mark the structural boundaries of the Española Basin, including:

• To the east, north-south trending buried thrust faults along the Sangre de Cristo Range, suggesting that during basin formation Laramide and older faults may have been exploited.
• To the west, the Pajarito Fault Zone and possibly the Cañada de Cochiti Fault Zone further west, both north trending (Koning, et. al., 2007); and normal faults in the Embudo Fault Zone to the north.

The remaining significant structural features of the area also resulted from the regional rifting. Volcanism linked to faulting and crustal thinning within and adjacent to the rift zone in the Santa Fe area began around 14 million years ago. The resulting Jemez and Cerros del Rio volcanic fields bound the Española Basin on the west and southwest, respectively (Koning, et. al., 2007).

The closest mapped fault to the site is exposed in the Santa Fe River a little over one mile from the site (Koning and Read, 2010). The site is on the upthown side of this fault, which is part of the larger Agua Fria Fault System. Additional faults may exist near the site which could not be identified based on existing information.

As would be expected considering the tectonic setting of the region (discussed above), New Mexico has an active seismic history. Researchers from the New Mexico Institute of Mining and Technology have developed catalogs of earthquakes for the state and bordering areas for the time frame of 1869 to 1998.

Figure 3-8 (from Sanford, et. al., 2002) illustrates the epicenters of earthquakes in the region having moment magnitudes of 3.0 or greater.

A total of 155 events are plotted for the time period of 1962 to 1998. Evident on Figure 3-8 is the concentration of events (36) in an area referred to as the Socorro Seismic Anomaly, approximately 140 miles south- southwest of Santa Fe.

Seismicity in that area is attributed to crustal thinning and the presence of an underlying large mass of magma (Sanford, et. al., 2002). Of note are a number of historic earthquakes along an identified fracture zone trending east-northeast in the area north of Santa Fe (possibly consistent with the Embudo Fault Zone that bounds the Española Basin to the north) and the absence of obvious seismic activity trending north-south with the Rio Grande Rift.

Regarding seismicity in the area more local to the site, Broxton and Vaniman (2004) report that the Pajarito Fault Zone that forms the western boundary of the Española Basin remains active. A strong earthquake occurred in 1918 approximately 25 miles southwest of Santa Fe. According to the USGS website, the modified Mercalli intensity of the event was VII – VIII with reports of a rupture of the earth’s surface and residents being thrown from their feet (USGS, 2009).

According to a USGS seismic hazard map produced in 2008, the site is situated in an area where a peak ground acceleration of 18 percent gravity has a two percent probability of exceedance in 50 years. The USGS references that 10 percent gravity “may be the threshold for damage to pre- 1965 structures.”

Within the Española Basin, the Tesuque Formation is the most significant water-bearing formation and the primary aquifer (source of potable drinking water) for the City of Santa Fe (Lazarus and Drakos, 1995). Shallow groundwater has been detected at the top of the Tesuque and in the Ancha Formations to the south of Santa Fe.

Recharge to the Tesuque and Ancha occurs primarily via precipitation and streamflow infiltration along the Sangre de Cristo Mountain front to the east of the site. This recharge occurs at high elevations and provides the driving force for the regional direction of groundwater flow within the Española Basin from east to west where groundwater ultimately discharges to the Rio Grande (or its tributaries) or is intercepted by supply wells (Lewis and West, 1995; Lazarus and Drakos, 1995).

Figure 3-9 is excerpted from the New Mexico Bureau of Geology and Mineral Resources Open File Report 520 that illustrates regional groundwater flow patterns within the Española Basin (Johnson, 2009). The blue lines represent groundwater contours as points of equal groundwater elevation interpreted from groundwater level measurements in wells (plotted as singular elevation points). The pink lines are interpreted as groundwater flow paths with the direction of flow being perpendicular to the groundwater contours (blue lines). The rate of groundwater flow is generally greater, or faster, when the blue lines are closer together, and less, or slower, when the blue lines are further apart. The shading from light to dark blue indicates varying depths to groundwater. The very light blue patches indicate depths of groundwater less than 100 ft, while most areas of the basin are middle blue (greater than 100 ft) to darker blue (100 to greater than 500 ft).

The regional flow pattern illustrated in Figure 3-9 is generally from east to west, consistent with recharge areas in the Sangre de Cristo Mountains (areas where precipitation infiltrates downward into the subsurface and replenishes groundwater). The Rio Grande is the primary receiving surface water (where groundwater flows upward and “daylights” to create a surface water body such as a river, stream, etc.). Also shown are the localized effects of pumping wells that supply the City of Santa Fe where the contours are circular and hashed on the inside indicating downward flow into a pumping well.

Figure 3-10 is a blowup excerpted from the area within the box in Figure 3- 9 to show mapped flow near the site at a larger scale. The darker blue shading around the site suggests a depth to groundwater at 300 to 500 ft. Using the two closest groundwater elevations plotted to the east and west of the site (6,154 ft msl and 6,155 ft msl), and the elevation of the site (6,497 ft msl), suggests that the depth to groundwater beneath the site is at 343 ft. The direction of groundwater flow based on regional data is interpreted to be due west based on the groundwater contours. The wide distance between the groundwater contours (blue lines) around the site indicate the rate of groundwater flow is relatively slow, or indicative of what is termed a “flat” gradient.

Other features of note in Figure 3-10 include: 1) the location of the Santa Fe River, an estimated 0.75 miles to the north of the site; and 2) the inferred boundary of a “groundwater unit” designated by the dashed/highlighted brown line to the north of the site. The boundary unit line is subparallel to the Santa Fe River and marks the boundary between the Santa Fe groundwater unit to the north and the La Cienega groundwater unit to the south. These groundwater units represent inferred boundaries between areas of groundwater flow and contribution.

The rate of groundwater flow in the Tesuque Formation (measured as hydraulic conductivity) is estimated to range from 0.2-6.0 feet/day in the Española Basin as a whole with an estimated rate on the lower end of the range of 0.7 feet/day in area of Santa Fe (Lazarus and Drakos, 1995).

Site groundwater hydrology is interpreted based on a site groundwater evaluation completed in 2024 by Daniel B. Stephens & Associates, Inc. (DBS&A) in coordination with CN. That evaluation included the installation of six monitor wells (MW-1 through MW-6) to evaluate site groundwater quality and groundwater flow. Results of that evaluation are summarized in DBS&A’s report entitled, “Monitor Well Installation & Groundwater Monitoring Report.” Salient findings from DBS&A’s report describing site hydrogeology are summarized below (DBS&A, 2025).

Groundwater beneath the site is found at a depth of 329 to 334 feet within the Tesuque Formation. The movement of groundwater in the Tesuque Formation is influenced by sediment grain-size and sorting, and the extent and shape of the geologic units in the aquifer (Koning and others, 2007).

The six monitoring wells MW-1 through MW-6 installed at the site are screened in sand units that are often interbedded with clayey sands.

These sand units appear to be above a consistently occurring clay unit that may limit the hydraulic connectivity between groundwater in the sand units adjacent to the well screens and sand units that occur deeper in the Tesuque Formation aquifer.

Observed water levels and the interpreted water-table surface as measured on January 10, 2025 are provided in Figure 3-11. The hydraulic gradient (slope of the water table) indicated by the contours in Figure 3-11 ranges from about 0.002 to 0.005 foot per foot, which is typical for the Tesuque Formation. The direction of groundwater flow beneath the site is shown to funnel toward well MW-3. The funneling of groundwater toward well MW-3 is interpreted to reflect the location of that well within more permeable channel-sand deposits of higher hydraulic conductivity as opposed to the other five wells completed in less permeable overbank deposits of lower hydraulic conductivity.