Attachment_D-8_(1_of_4)_DP_West_Site_History_and_Past_Decontamination_Efforts.pdf

DP West Site History and Past Decontamination Efforts

1.0 General Site Information

Los Alamos National Laboratory is a multidisciplinary research facility owned by DOE and managed by TRIAD. The Laboratory is located in north-central New Mexico approximately 60 mi northeast of Albuquerque and 20 mi northwest of Santa Fe. The Laboratory covers 40 mi2 of the Pajarito Plateau, which consists of a series of finger-like mesas separated by deep canyons containing perennial and intermittent streams running from west to east. Mesa tops range in elevation from approximately 6200 feet to 7800 feet above sea level.

Buildings 21-02, 21-03, 21-04, 21-05, 21-149, and 21-150 housed nuclear research and processing activities. Buildings 21-312, 21-313, 21-314 and 21-315, located along a central corridor traversing the former DP West laboratory/process line, served as access and support facilities. Buildings 21-03 and 21- 04, which were plutonium and uranium laboratories, have been removed with the exception of small sections adjacent to Buildings 21-313 and 21-314. These sections were left as part of the corridor between Buildings 21-02 and 21-05.

2.0 SITE BACKGROUND

TA-21 is located east of downtown Los Alamos, New Mexico, on a spur of “Townsite Mesa” known as DP Mesa. DP Mesa is bounded by the drainage channels in DP Canyon to the north and Los Alamos Canyon to the south. The eastern boundary is formed by the confluence of the two drainage channels.

The western boundary is defined by the property boundary of TA-21. DP Mesa is divided into two separate areas. The western area, historically dedicated to plutonium operations, is known as DP West.

The smaller, easternmost grouping of buildings is known as DP East. Building 21-257, the Radioactive Liquid Waste Disposal Facility, is located between DP West and DP East.

The Laboratory transferred plutonium purification and recovery operations to the DP West facility in September 1945. DP West was used for production-scale uranium and plutonium processing. DP East also started operating in September 1945. Work at DP East originally focused on polonium initiator research and continued with actinium and polonium processing operations.

Acids and caustics were used to isolate and concentrate uranium and plutonium at DP West. The buildings and surrounding soils potentially contain chemical and radiological contamination.

2.1 Historic Features and Operational History

The original facilities at TA-21 were constructed in 1944 and 1945. Plutonium purification operations were relocated from the D Building plutonium facility (TA-01) to DP West in September 1945. Uranium and plutonium purification started at TA-21 in September 1945. Several processing stages were required to separate the actinides from a nitrate solution feedstock received primarily from the Hanford Site. Other operations included fabricating uranium and plutonium metal, manufacturing space-heat sources, producing americium, separating isotopes, researching nuclear reactor fuel, and conducting various other research and development projects. Plutonium operations ended at TA-21 in 1978.

Buildings 21-02, 21-03, 21-04, and 21-05 had common features. Each building was constructed in 1945 as part of the original operations of DP West. Each is currently inactive and demolished to the slabs, and all above-grade equipment has been removed. Each has concrete-filled trenches and troughs under former laboratory floors. These trenches crossed the laboratory rooms from east to west and were connected to floor drains to collect any waste or wash waters from the laboratory floors. Process piping

TA-21 DP West Slabs D&D and Remediation Project

RFP-0000300

within the trenches were routed to perimeter utility tunnels that contained the main service process pipes and, possibly, electrical wiring.

The Laboratory decontaminated these buildings from 1978 through 1981. Surfaces were decontaminated and covered with an orange paint to fix residual contamination. Contaminated floors were covered with a new layer of concrete and/or linoleum. The buildings were subsequently used for other research purposes under restricted-use occupancy conditions (LANL 1982, 06339).

Prior to the 1978–1981 decommissioning, it was common practice to clean contaminated surfaces to the extent practical and cover the residual contamination with paint, concrete, or tile. Contaminated building materials, such as sections of roofs and walls, were sometimes removed. Paint chips and underlying materials are expected to be radioactively contaminated. The primary component of the contamination is assumed to be the various isotopes of plutonium. Americium-241 is the predominant contaminant in specific areas within Building 21-02.

The following sections give brief histories and construction details of the main buildings.

2.1.1 Building 21-02

The operations conducted in Building 21-02 included plutonium processing, americium-241 recovery and storage, plutonium wastes dissolution and recovery, nuclear stockpiling, and health and safety. The structure also contained a liquid waste loading area, solvent extraction columns, and a scrap incinerator.

A criticality incident occurred in this building in 1958 (LANL 1999, 87442).

Building 21-02 was oriented north-northeast to south-southwest. The north section of Building 21-02 (referred to as TA-21-02 North Building) was a pre-engineered, warehouse-type building with corrugated metal exterior siding. The walls were structural steel with gypsum lathe and plaster. The south section of Building 21-02 (also referred to as TA-21-02 South Building) was a steel and plaster laboratory building, with structural steel walls, concrete stucco and metal siding on the exterior; and gypsum lathe and plaster on the inside (LANL 1999, 87442). The current combined floor area of the north and south sections is approximately 13,500 feet2.

Both structures have a raised concrete floor that was placed in two layers. The original floor was 6 in.

thick. A 4-in. layer of concrete was poured over the original floor to shield and contain radioactive contaminants. Both sections of the buildings reportedly had interior transite panels that were considered asbestos-containing material (ACM). In addition, many floors had asbestos-containing linoleum or vinyl-asbestos tiles (LANL 1982, 06339).

The building was a composite of various elevations and roof slopes, with a high, pitched bay in the center.

The roofs supported mechanical ducting. The roofing materials were suspected ACM. There was a partial mezzanine used primarily for storage and observation and basement areas housing electrical equipment.

There was also an attic with numerous pipelines and potentially asbestos-containing insulation traversing the middle of the structure and extending into adjacent Buildings 21-312 and 21-313.

Building 21-02 most recently housed offices, storage rooms, and chemistry laboratories. All above-grade equipment previously located in the structure has been removed.

2.1.2 Building 21-03

Building 21-03 housed plutonium-238/239 research and development; americium-241 and tritium separation research; inorganic and structural chemical research; and carbon, nitrogen, and oxygen isotope separation work.

Most of the building was razed in 1994. All that remains are the center corridor slab sections, portions of the foundation and utility tunnels.

Building 21-03 was originally a pre-engineered, warehouse-type building similar to Building 21-02. The building contained the same types of trenches and troughs under the laboratory floors as in Building 21-02. Portions of the utility tunnels are visible where the building foundation was cut.

2.1.3 Building 21-04

Building 21-04 housed plutonium hot-cell research, much of the artificial heart research program, and Los Alamos Molten Plutonium Reactor Experiment (LAMPRE) research and development. Most of the building was demolished in 1994. All that remain are the center corridor slab sections. Portions of the former building’s utility tunnels are visible where the building foundation was cut. Building 21-04 was similar to Building 21-03 in its construction.

2.1.4 Building 21-05

Building 21-05 housed plutonium and metal alloy fabrication operations, plutonium parts fabrication and testing for nuclear devices, and uranium and plutonium limited research. Tritium recovery, fluoride reduction, metal casting and machining, and uranium operations were also conducted in this facility.

Building 21-05 is structurally similar to Building 21-02. Modifications similar to those in Building 21-02 were made during decontamination, including a second 4-in.-thick concrete floor and painting contaminated surfaces.

The building had a metal pitched roof. The roof supported mechanical ducting. The roofing materials were suspected ACM. There was a partial mezzanine used primarily for storage and observation and a basement housing electrical equipment. There was also an attic with numerous pipelines and potentially asbestos-containing insulation traversing the middle of the structure and extending into adjacent corridors (Buildings 21-149 and 21-315).

Building 21-05 was subjected to numerous renovations and additions, based on changes in the research and development. Additions varied in architectural detail including roofs, walls, floors, and structural features. The renovations included adding a solvent shed and two hoists; modifying the furnace, exhaust, lighting, heating, wiring, and ventilation systems; and installing a balcony and stairs, an electro-refining lab, new dry boxes and exhaust stacks, equipment rooms, and an equipment room containing a dehumidifier and compressor (LANL 1999, 87442). The current footprint of the building is approximately 14,400 feet2.

2.1.5 Building 21-116

The original (1950) portion of Building TA-21-116 housed utility equipment, a restroom, and decontamination shower. This portion of the building was directly adjacent to corridor TA-21-315. In 1957/1958 a new additional was added to the original portion. This new addition was formerly an airport hanger located on Airport Road at the Los Alamos Airport. Once the building was relocated to TA-21, its first use was as the Plant Services Building for the plutonium processing/research facility. It was also connected to corridor TA-21-315 by its own passageway (TA-21-144). This added portion originally contained workbenches, welding stations, a tool crib, a janitor equipment area, an equipment monitoring area, and other equipment areas. After 1967 and before 1983, TA-21-116 stored audio system equipment. In 1983, it was used as a general equipment storage facility. Since 1983, TA-21-116 was used as a conference room, office space, and a radiation count lab.

2.1.6 Building 21-149

Building 21-149 was constructed in 1962. It was primarily a corridor that connected Buildings 21-150 and 21-05 and included an equipment room, telephone cabinet, and a men’s restroom on the first floor. The building served as a hub for the distribution of utilities, including alarms and public address systems, to Buildings 21-02, 21-03, 21-04, and 21-05.

The building had a partial second floor containing two fans and an equipment room. The attic contained numerous pipelines and potentially asbestos-containing insulation traversing the middle of the structure and extending into the corridors of Buildings 21-150 and 21-05. The current footprint of the building is approximately 3762 feet2. The base is a concrete slab with footings (LANL 1999, 87442).

Building 21-149 was a steel-framed post and beam structure with insulated metal siding panels and flat built-up roofing. The roofing materials were assumed to be ACM. The building had two heating, ventilation, and air conditioning (HVAC) condenser units, a high-efficiency particulate air (HEPA) filtration system, a bag house, and two 50-feet stacks on the exterior. The HEPA filters and exhaust system were upgraded in 1972. The HVAC system contained a condenser and blower equipment.

Asbestos-containing transite panels, vinyl-asbestos floor tiles, and thermal system insulation were assumed to occur in Building 21-149, based on visual observations and the date of construction.

2.1.6 Building 21-150

Building 21-150 was built in 1961 and 1962 to house plutonium fuels development activities. The building contained a laser lab, wet lab, other laboratories, offices, a sampling shed, and a janitor’s closet.

Research performed in this building included work on plutonium fuels, fast reactor plutonium/ceramic fuels, batteries for artificial hearts, space heat sources, and cold fusion. Equipment observed in Building 21-150 included several fume hoods. The footprint of the building covers 7041 feet2. It rested on a reinforced concrete slab.

Building 21-150 was an industrial-style building with cast-in-place concrete beams and columns spanned by concrete masonry units. The built-up roof was assumed to contain ACM. Interior walls were covered with cement plaster. It had a full basement with electric switchgear and a mezzanine space containing three laboratories (LANL 1999, 87442). The roof had a visible external piping and conduit system as well as an exhaust stack and blower. Asbestos-containing transite panels, vinyl-asbestos floor tiles, and thermal system insulation were assumed to occur in this building, based on visual observations and the date of construction.

2.1.7 Buildings 21-312, 21-313, 21-314, and 21-315

These buildings were designed to allow quick and easy passage of personnel and equipment between the buildings. The rooms were primarily storage, janitorial supply, and restrooms. The corridor spanned the entire length of the complex from Building 21-02 through 21-150, with an uneven grade and many double doors, which in most cases had two sets leading into and out of rooms of the main buildings. The buildings also served as the primary utility corridor for DP West.

2.2 Solid Waste Management Units at DP West

Plutonium-processing operations generated high volumes of process and waste liquids.

2.2.1 Solid Waste Management Unit Descriptions

There are three categories of SWMUs on the site: acid waste sumps, underground seepage pits, and decommissioned septic tanks. The sumps, pits, and septic tanks may have been installed as early as 1946 and were removed at various times. The decommissioned septic tanks have not been considered in this investigation because they are not near existing building slabs.

2.2.2 Building Relationships to Solid Waste Management Units

SWMUs in the vicinity of structures at DP West are discussed in Chapter 18 of the TA-21 Operable Unit Work Plan for ER (LANL 1991, 07529).

There are 11 SWMUs near the existing and former buildings at DP West, not including the decommissioned septic tanks. Each of these is discussed in the following sections.

2.2.3 Waste Lines and Former Sumps

Acid waste lines from Buildings 21-02, 21-03, 21-04, 21-05, and 21-150 emptied into acid well sumps, from which the waste was transferred by way of pipes to Material Disposal Area (MDA) T or subsequently to waste treatment plants (Building 21-35 followed by Building 21-257). The sumps also received liquid waste discharges and chilled water overflows from their respective buildings. The sumps were located near a northern corner of each building.

Liquid waste was conveyed by way of pipes connected to the sumps at Buildings 21-02, 21-03, 21-04, 21-05, and 21-150 to MDA T between 1945 and 1952. The waste was carried in a 6-in. jennite-coated iron pipe, installed between 6.5- and 8-feet below ground surface (bgs). Building 21-35, a waste disposal plant, was constructed in 1952. A new, 4-in. extra heavy cast iron waste line was installed parallel to and approximately 20 feet north of the old 6-in. pipe, which was abandoned in place. In addition, three 1.5-in.

stainless steel pipes were installed 1-feet above the new 4-in. waste line in the same trench. One of these lines originated at the northeast corner of Buildings 21-02 and carried “special waste” directly to Building 21-35. The remaining lines carried raffinate from Buildings 21-03 and 21-05 to holding tanks and then to Building 21-35. A 4-in. cast iron line was installed in 1962. The line carried waste from the acid sump [now SWMU 21-022 (g)] at Building 21-150 to the existing 4-in. line to Building 21-35. The 4- and 1.5-in. lines were rerouted in 1967, when Building 21-35 was removed and Building 21-257, a new waste disposal plant, began operation. The line segments from the new portion of the lines to Building 21-35 were removed (LANL 1991, 07529).

The sumps were constructed of brick, approximately 5-feet 5-in. in diameter and 10-feet deep, originally with a gravel base. Construction drawings indicate a 2-feet diameter, 5-feet deep steel catch basin in each sump. Plastic liners were placed and grouted inside each sump in 1963 (LANL 1991, 07529).

The acid well sumps and surrounding soils were removed between 1979 and 1980 (LANL 1982, 06399).

The sumps were bypassed by connecting the outfall pipe directly to the acid waste line exiting the building. The majority of the contaminated soils around the sumps were removed, based on field gross alpha measurements. No analyses for non-radiological constituents were reported. Exposed surfaces in the excavations were sprayed with asphalt and the excavations were backfilled (LANL 1982, 06399).

According to diagrams in previous reports (LANL 1982, 06399), excavations of contaminated soil in and around the sumps stopped within a few feet of the building foundations and extended to depths of up to 20 feet. Little information exists on anticipated hazardous chemicals in the acid waste sump areas. A sample of pipe residue from the acid waste pipe that fed the acid waste sumps outside Buildings 21-03 and 21-04 was submitted for analysis (Montoya 1987, 01138). Concentrations of arsenic, boron, cobalt, molybdenum, niobium, nickel, lead, antimony, uranium, and zinc exceeded background levels. Plutonium was also observed but not quantified (LANL 1991, 07529). It is anticipated that associated contamination will include nitrates, chlorides, and fluorides resulting from nitric, hydrochloric, and hydrofluoric acid discharges from the plutonium separation operations (LANL 1991, 07529).

The fourth sump considered in this investigation is SWMU 21-022(i). It is located in the southwest corner of the equipment room on the southeast corner of Building 21-02. It consists of a 6-feet by 18-feet well that is approximately 8 feet deep. An 18-in. by 18-in. by 24-in. deep sump is located in the southwest corner of the well. The room is partially below grade. The bottom of the sump is approximately 14 feet bgs. The room contained air compressors and evaporative coolers. Historical discharges from this sump are not understood, because drain lines associated with this sump have not been observed in available reference documents.

2.2.4 Underground Seepage Pits

Seepage pits were built into subsurface volcanic tuff, which would reportedly serve to filter large quantities of liquids containing low concentrations of radioactive materials. The exact number and locations of these pits are not known. SWMUs 21-006(e) and 21-006(f) are located near former Building 21-04, which was demolished in 1994.

SWMU 21-006(a) is a 0.1-acre seepage pit located between Buildings 21-02 and 21-03 (LANL 1978, 08905). The pit was used to dispose of liquids from the Hanford container washing operation. It is not known whether it is north or south of the east-west corridor or part of other SWMUs in the general area.

SWMU 21-006(c) is located about 15 feet outside the door to bomb-cleaning Room 322 of former Building 21-03. This pit reportedly received “bomb electrolytic decontamination solution” from a drain in Room 322. Because of building renovations, this pit is now under or partly under a structure. The approximate location is near the center and base of the wall that divides Rooms 3131 and 3133.

SWMU-006(d) may be associated with a concrete pad and a French drain system called the TA-21-272 Dock Seepage Pit. Waste from a second-story chemical makeup room was reportedly dumped or pumped into a stone-filled seepage pit in this area (LANL 1991, 07529). This pit may be associated with what is labeled either SWMU-006(a) or SWMU-006(c).

SWMUs 21-006(a), 21-006(c), and 21-006(d) were reportedly used to dispose of Hanford container wash water, bomb electrolytic decontamination solution (ethylene glycol, phosphorous acid, and plutonium), and chemical makeup room wastewater. Approximately 12 gal./day of ethylene glycol and phosphorous acid electrolytic solution were reportedly emptied into the drain in Room 322. Analyses of a source of the liquid waste indicated that approximately 1.9 mg of plutonium were released daily (Tribby 1947, 01764).

According to the “Radioactive Waste Management Site Plan” (LANL 1978, 08905), the estimated radioactivity associated with SWMU 21-006(a) is high. Plutonium is expected to be the principal radionuclide (LANL 1986, 07419).

2.3 Historical Releases and Discharges

Comprehensive lists of spills recorded in the DP West buildings were compiled before the 1978–1980 decommissioning project (Blackwell 1979, 90520; 1980, 90516; 1980, 90517; 1980, 90518; 1980, 90519;

and 1980, 01912). The releases listed in Table 2.3-1 are described in several documents and occurred throughout the 34-yr operating history of DP West. Releases of radionuclides were reported; however, releases of chemicals generally were not reported. Explosions, fires, breaches in glove boxes, and other containment failures caused the radioactive releases. Releases in utility tunnels in Buildings 21-02 and 21-05 are listed in Table 2.3-2.

Areas contaminated by radioactive releases were usually cleaned. It sometimes took as long as 6 months to decontaminate a single large process room. Decontamination normally included washing the surfaces with water and other liquids and removing plaster from walls or ceiling tiles. Decontaminated areas were painted to fix residual contamination. It is likely that the paint contained lead and, possibly, zinc and cadmium (Baker 2005, 90515).

Two AOCs related to the existing buildings are noted in Chapter 18 of the OU 1106 RFI work plan (LANL 1991, 07529). AOC C-21-001 represents a hydrogen fluoride spill that occurred in the corridor between Buildings 21-04 and 21-05. AOC C-21-006 represents a release of americium-241 from a leaking transport trailer. The 25 feet2 affected area was covered with asphalt (LANL 1991, 07529).

2.4 Contaminant Transport Mechanisms and Receptors

Potential transport mechanisms that may lead to exposure of potential receptors include vaporization and gaseous diffusion and advection of volatile organic compounds (VOCs) and tritium in air;

dissolution and/or particulate transport of surface contaminants during rainfall and snow melt runoff events;

mechanical resuspension of particulate contaminants due to concrete coring and drilling;

airborne transport of contaminated surface soils;

continued dissolution and advective/dispersive transport of radiological and chemical contaminants contained in subsurface soil and/or bedrock;

biotic perturbation and translocation of contaminants in subsurface soils; and future migration of contaminants already migrated into subsurface media.

Potential receptors of possible contaminant transport include down-gradient users of groundwater, site workers at TA-21, trail users in the canyon below TA-21, and ecological receptors both onsite and immediately surrounding the site.

2.5 Current and Proposed Land Use

DP West, DP East, and Building 21-257 are within fenced areas subject to DOE/LANL access control.

DOE has determined future land use at TA-21 as industrial/construction.

2.6 Previous Investigations

There is no evidence that investigations conducted before the 1978–1980 building decommissioning activities considered contaminants other than radionuclides. Acid and caustic contamination was generally overlooked: this contamination was believed to be concentrated within documented areas. The OU 1106 RFI work plan (LANL 1991, 07529) contains a summary of historical analytical results for underground seepage pits, buried waste lines, acid waste lines and sumps, decommissioned septic systems, active and inactive container storage areas, and many areas of AOCs.

2.7 Historical Investigation and Decontamination at Buildings 21-02, 21-05, and 21-150

Plutonium operations at DP West were relocated to a new plutonium facility at TA-55 in 1978. The D&D project performed from 1978 to 1981 involved removing plutonium-contaminated process systems and inside utility support services, decontaminating exterior concrete pads; and removing exterior concrete, asphalt, and soil. Walls and ceilings were painted orange and new sheet linoleum was laid on some room floor surfaces.

The D&D activities are described in “Los Alamos DP West Plutonium Facility Decontamination Project 1978–1981” (LANL 1982, 06399). The surface activity limits applied to the D&D activities were 2000 total alpha activity dpm/100 cm2 and 400 dpm/100 cm2 removable (swipeable) alpha activity. The beta-gamma and neutron dose equivalent limits were 1 mrem/h on contact and 0.25 mrem/h at 1 m, using a Ludlum Model 14 or Eberline Model 112B Geiger-Mueller and Eberline PNR-4 neutron detector, respectively (Valentine 1979, 90514). The dose at 1 m (0.25 mrem/h) is 10% of the DOE radiation dose limit for workers (5000 mrem/yr), assuming an annual exposure of 2000 h.

The Laboratory’s special decontamination crew performed the initial decontamination work to reduce activity levels to a point where there was less of a chance of the material being spread to other areas.

Laborers and janitors performed later stages of decontamination under the supervision of LANL health physics technicians.

2.7.1 Decontamination of Building 21-02

The Laboratory monitored accessible surfaces to determine total and fixed radiation levels after equipment was removed from Building 21-02. Workers observed several areas that exhibited greater than 2 × 106 total alpha dpm/100 cm2. The areas were located near or in floor trenches or under metal strips that covered concrete expansion joints. Radioactive contamination also reportedly settled in voids between floors and walls and near or in dissolver pits. Surface activities generally ranged from 2000 to 1 × 105 alpha dpm/100 cm2 in the building (Blackwell 1980, 01909).

2.7.1.1 Walls, Ceilings, and Doors

Plaster was removed from areas on ceilings and walls where high levels of activity were observed. Other areas, including overhead lights, sprinkler systems, and air inlet systems, were cleaned by scrubbing with commercially available household cleaners and wiping with rags. In some areas the plaster from entire walls had to be removed, in addition to large sections of ceilings, to reduce contamination to an acceptable level. In other areas, only small sections of plaster were removed; the remainder of the walls and ceilings were wiped with damp rags.

Ceilings, walls, and doors were reportedly decontaminated to less than 2000 alpha dpm/100 cm2 with non-detectable counts on swipe samples, except in a few isolated areas. Contaminated paint was removed using a commercially available paint remover (Blackwell 1980, 01909).

2.7.1.2 Floors

Concrete or hard plaster was removed using an air impact gun (a scabbler). Approximately 8200 feet2 of concrete floors required repeated scabbling. Some areas of the floor were scabbled to depths of 1 to 3 in.

without having removed the contamination to below guidelines.

Approximately 1500 anchor pins were reportedly removed from the floor. Areas around the pins were decontaminated and chiseled. Approximately 300 feet of metal strips, associated with concrete expansion joints, were removed from the floor. The expansion joints were then decontaminated.

Residual alpha radioactivity on Building 21-02 floors ranged from less than 4000 to less than 1x106 dpm/100 cm2.

Workers poured a 2-in. layer of concrete over decontaminated concrete floors. Some of the floors were also covered with linoleum (Blackwell 1980, 01909). It is assumed that the new layer of concrete is thicker than 2 in. in areas where the original concrete was scabbled to depths greater than 1 in.

2.7.1.3 Utility Trenches and Tunnels

Workers addressed utility trenches located in the process rooms and the subsurface utility tunnels that surround the building by decontaminating the trenches and filling them with concrete, removing some service lines in the utility tunnels, and abandoning others in place.

Workers reportedly disconnected and removed the negative-pressure chilled-water, vacuum, caustic supply and return lines, a caustic drain, and an acid waste drain from the utility tunnels. Workers also removed 0.5 m3 of soil containing nCi/g-levels of plutonium from a portion of the utility tunnel located between Rooms 213 and 218. Steam, helium, argon, air, hot water, positive-pressure chilled-water, and condensate return lines were reportedly abandoned in place. Entrances to the tunnels were filled with concrete, with the exception of the north and south entrances, which were covered with locked metal covers (Blackwell 1980, 01909).

2.7.1.4 Building Exterior

Workers scabbled approximately 120 feet2 and acid-washed more than 500 feet2 of exterior walls.

Workers also scabbled approximately 700 feet2 of exterior concrete pads. Workers scanned the ground adjacent to the building with a phoswitch detector. Soils, asphalt, and concrete that exhibited elevated levels of radioactivity were excavated and replaced with new materials (Blackwell 1980, 01909).

2.7.1.5 Post-decontamination Dosimetry Measurements

Airborne activity in the building after decontamination was reportedly less than 2% of the maximum permissible concentration for radiation workers (LANL 1982, 06399) (limit not reported). Beta-gamma and neutron radiation levels in the building were reportedly less than a 0.25 mR/h guideline.

In addition, 55 theromoluminescent detectors (TLDs) were placed in the rooms at 1 m above the floor and left for one month. Fifty-one TLDs recorded no detected doses and four recorded 10 mR, indicating that dose rates were below 0.25 mR/h. The uncertainty associated with the TLD results was 2.0 mR (Blackwell 1980, 01909).

2.7.2 Decontamination of Building 21-05

Building 21-05 was used for processing plutonium-239 from 1946 through 1977. Several failures in containment systems resulted in plutonium contamination of systems and building structures.

Building 21-05 was surveyed, cleaned, and resurveyed using similar methods applied during the Building 21-02 decontamination (Blackwell 1980, 90517).

2.7.2.1 Walls

Workers removed approximately 85 m2 of plaster from walls and ceilings. The concrete wall in the southwest corner of the basement was reportedly highly contaminated with plutonium. The wall was partially decontaminated using paint removers and acid scrubbing and then painted, plastered, and repainted. Materials under the plaster reportedly exhibited total radiation levels up to 2 × 105 alpha dpm/100 cm2 (LANL 1982, 06399).

2.7.2.2 Attic

Accessible services in the attic were reportedly wiped with damp rags, surveyed, and spray-painted with water-based asphalt.

2.7.2.3 Floors

Workers reportedly scabbled approximately 240 m2 of concrete. The floors were leveled and covered with sheet linoleum. Workers poured a 3- to 4-in. concrete layer over the original concrete floor in Room 501 and installed a linoleum cover. Surface activities exhibited by the original concrete were up to 4 ×105 alpha dpm/100 cm2 in places (Blackwell 1980, 90517).

2.7.2.4 Utility Trenches and Tunnels

Workers removed mechanical service lines in the utility trenches in process rooms. The trenches were then decontaminated and surveyed. Total surface activity under the paint in the floor trenches measured up to 1 × 106 alpha dpm/100 cm2 after decontamination. The trenches were then filled with concrete.

Workers reportedly observed high concentrations of plutonium in the tunnel. They removed soil but no amount was reported. Workers reportedly disconnected and removed the negative-pressure chilled-water, vacuum, caustic supply, and return lines; a caustic drain; and an acid waste drain from the utility tunnels. Steam, helium, argon, air, hot water, positive-pressure chilled-water, and condensate return lines were reportedly abandoned in place. Liquid waste lines from utility sinks in 502A and 511 were capped and left in the building floor. The inside surfaces of these lines were reportedly contaminated.

Workers fixed residual contamination by spraying surfaces with water-based asphalt. The tunnels were reportedly sealed off from the rooms. Entrances to the tunnels were filled with concrete, with the exception of the north and south entrances, which were covered with locked metal covers (Blackwell 1980, 90517).

2.7.2.5 Post-decontamination Dosimetry Measurements

Airborne activity in the building after decontamination was reportedly less than 2% of the maximum permissible concentration for radiation workers (limit not reported). No beta-gamma and neutron readings exceeded 0.25 mR/h. In addition, 86 TLDs were placed in the rooms at 1 m above the floor and left for 1 month. Seventy-eight TLDs recorded no detected doses, 6 recorded 10 mR, and 2 recorded 20 mR, indicating that dose rates were below 0.25 mR/h. The uncertainty associated with the TLD results was

2.0 mR (Blackwell 1980, 90517).

2.7.3 Decontamination of Building 21-150

Building 21-150 was built in 1963 to house plutonium fuels development. Fewer releases have been reported for this building than in Buildings 21-02, 21-03, 21-04, and 21-05. Releases of plutonium reportedly occurred in Rooms 603, 604, 605, 606, and 607. The releases reportedly contaminated acid waste systems and building structures. Building 21-150 was surveyed, cleaned, and resurveyed using methods similar to those applied during the Building 21-02 and 21-05 decontaminations.

There are three salient differences in the decontamination activities at Building 21-150. Workers removed and replaced the contaminated roof. There is no utility tunnel associated with Building 21-150.

Furthermore, the positive-pressure chilled-water system at Building 21-150 was left in place, at the request of future occupants.

The positive-pressure chilled-water system was drained and flushed. Workers cleaned the screen and screen holder. Alpha activity inside the system was reportedly at least 4 × 104 alpha dpm/100 cm2. The inside surfaces of the liquid waste lines left in the basement were not checked and are considered contaminated. Interior surfaces of electrical junction boxes were reportedly surveyed and decontaminated to within guideline levels. Connecting conduits were not checked and were reported as contaminated (Blackwell 1980, 90519).

2.7.3.1 Post-decontamination Dosimetry Measurements

Airborne activity in the building after decontamination was reportedly less than 2% of the maximum permissible concentration for radiation workers (no limit reported). Beta-gamma and neutron radiation levels in the building were reportedly measured at less than 0.25 mR/h.

In addition, 40 TLDs were placed in the rooms at 1 m above the floor and left for 1 month. Twenty-seven TLDs recorded no dose and 13 recorded 10 mR, indicating that dose rates were below 0.25 mR/h. The uncertainty associated with the TLD results was 2.0 mR (Blackwell 1980, 90519).

3.0 EXISTING SITE CONDITIONS

3.1 Surface Conditions

DP West Buildings 21-02, 21-05, and 21-150; portions of former Buildings 21-03 and 21-04; and interconnecting structures were located on the west-central portion of DP Mesa within the fenced area of TA-21. All that remains of these buildings are the slabs and utility tunnels/basements. Each of the buildings were considered either contaminated or potentially contaminated. The floors of these buildings have been routinely monitored by the HSR-1 for surface contamination. Levels of airborne and surface radioactivity are expected to be similar to those reported after the 1978–1981 decommissioning project described in Section 2.7. The site occupies approximately 3.5 acres (1.4 hectares).

The following sections describe generalized surface features and existing subsurface geologic characteristics at TA-21. Known surface and subsurface traits and their potential effects on the occurrence and concentration of contaminants include;

a canyon-mesa terrain, which affects meteorological conditions and ecological habitats at the surface;

a semi-arid climate with low precipitation and a high evapotranspiration rate, which limits the extent of subsurface moisture percolation and the amount of moisture available for leaching radionuclides or other hazardous waste constituents; and a thick, relatively dry, unsaturated vadose zone, which greatly restricts or prevents downward migration of contaminants in the liquid phase through the vadose zone to the regional aquifer.

Elevations at the top of DP Mesa near the site range from 7160 feet to 7220 feet above sea level (asl), with a gentle slope to the south. The canyon slope ranges from 7060 feet in the bottom of BV Canyon to 7180 feet on the south edge of DP Mesa, immediately south of the site. Surface drainage from the site (e.g., rainwater, snowmelt) flows south into BV Canyon, a shallow tributary of Los Alamos Canyon.

Topography prevents surface runoff from flowing north into DP Canyon.

Administrative and research buildings occupied areas west and east of the site. The BV Canyon borders the south side of the site. MDA T is located approximately 100 feet east-northeast of Building 21-150 and 400 feet northeast of Building 21-02. DP Road is the only access road to DP Mesa.

3.2 Surface Soils

Natural or undisturbed surface soil cover at DP West is limited because of Laboratory operations such as building construction and demolition. The present-day mesa surface in the investigation area is predominantly asphalt and landfill cover material. Asphalt containing gravel-sized aggregate covers land areas outside the building footprints.

Where undisturbed, soils on the mesa surface are thin and poorly developed. They tend to be sandy near the surface and clay-rich beneath the surface. Soil profiles tend to be more poorly developed on the cliff-forming south-facing slopes than on the north-facing slopes, which tend to have higher organic content.

A discussion of the soils in the Los Alamos area can be found in Section 2.2.1.3 of the Environmental Restoration (ER) Project’s installation work plan (LANL 1998, 62060, pp. 2–21) and in a soil survey of the area (LANL 1978, 05702).

3.3 Surface Water

Mesas of the Pajarito Plateau are generally dry, both on the surface and within the bedrock forming the mesa. Canyons range from wet to relatively dry; the wettest canyons contain continuous streams and perennial groundwater in the canyon-bottom alluvium. DP Mesa is bounded on the north by DP Canyon and on the south by Los Alamos Canyon and BV Canyon, which flows into Los Alamos Canyon. DP and Los Alamos Canyons have intermittent flow sufficient to support alluvial groundwater systems.

BV Canyon has only occasional stream flow that is insufficient to support alluvial groundwater. There are no streams on DP Mesa; storm water and snowmelt generally run off the mesa as sheet flow and in small drainages off the mesa sides.

3.4 Utilities

Recent utility drawings of the site indicate abandoned water, sewer, gas, steam and condensate, chill water, acid waste, helium, argon, vacuum systems; and electric lines. There are two water lines near the site. One line runs approximately 25 feet north of the buildings (northern line). An extension of this line runs south to Building 21-315. The second water line runs approximately 40 feet south of the buildings (southern line). Lines from Buildings 21-313, 21-314 and 21-149 are each connected to the southern line.

Building 21-150 is connected to the northern line. The southern and northern water lines join after passing Building 21-150. A sewer line runs parallel to the southern water line and has six extensions running north into Buildings 21-313, 21-314, 21-04, and 21-315 and Buildings 21-149 and 21-150. One gas line is apparent on the maps. It runs within 10 feet of the west side and south corner of Building 21-150. Two electric lines appear on the drawings. One line runs south-southwest into Building 21-313. The second line runs north-northeast into Buildings 21-149 and 21-150.

3.5 Utility Tunnels Information

The utility tunnels located under Buildings 21-02, 21-03, 21-04, and 21-05 reportedly contained helium, argon, positively and negatively pressured chilled water, acid supply and return, acid waste, and vacuum lines. It is known that the pipes have leaked, at times requiring hands-on repair inside the tunnels.

Workers have entered the tunnels through one or more man-ways situated along the outside of the buildings. Workers have also removed contaminated soil from the utility tunnels in Buildings 21-02 and 21-05. Only a small portion of the utility tunnels of Buildings 21-03 and 21-04 currently exist beneath the corridor.

There are varying reports regarding the status of the pipes in the tunnels. Contaminated utility piping (vacuum, negative-pressure chilled-water, acid, and caustic lines) have reportedly been removed from the tunnels in Buildings 21-02 and 21-05. Other pipes considered uncontaminated were reportedly abandoned in place.

4.0 REFERENCES

Baker, K. R., June 30, 2005. “TA-21 June 30, 2005, Site Walk Through and Interviews with Workers,” Environmental Restoration Group, Inc., memorandum to R. Rager, from K.R. Baker, Albuquerque, New Mexico (Baker 2005, 90515)

Blackwell, C., August 29, 1979. “Final Condition Report for Rooms 401-East, 401-A, -B and -C, 403, 404, 406, and 407 at DPW, TA-21” Los Alamos Scientific Laboratory memorandum to A. Valentine from C.

Blackwell, Los Alamos, New Mexico. (Blackwell 1979, 90520)

Blackwell, C., March 13, 1980. “Final Survey Report of Building 150 at TA-21,” Los Alamos Scientific Laboratory memorandum to A. Valentine from C. Blackwell, Los Alamos, New Mexico.

(Blackwell 1980, 90519)

Blackwell, C., March 18, 1980. “Final Condition Report of Building 150 at TA-21,” Los Alamos Scientific Laboratory memorandum to A. Valentine from C. Blackwell, Los Alamos, New Mexico.

(Blackwell 1980, 90516)

Blackwell, C., July 24, 1980. “Final Condition Report on Building 5 at TA-21,” Los Alamos Scientific Laboratory memorandum to A. Valentine from C. Blackwell, Los Alamos, New Mexico.

(Blackwell 1980, 90518)

Blackwell, C., July 24, 1980. “Final Survey Report of Building 5 at TA-21,” Los Alamos Scientific Laboratory memorandum to A. Valentine from C. Blackwell, Los Alamos, New Mexico.

(Blackwell 1980, 90517)

Blackwell, C., August 13, 1980. “Final Condition Report of Rooms 403, 404, 405, 406, and 407 in Building 4 at TA-21,” Los Alamos Scientific Laboratory memorandum to A. Valentine from C. Blackwell, Los Alamos, New Mexico. (Blackwell 1980, 01912)

Blackwell, C., October 8, 1980. “Final Condition Report of Rooms 308, 312, 314, 320, 321, and 322 in Building 3 at TA-21,” Los Alamos Scientific Laboratory memorandum to A. Valentine from C. Blackwell, Los Alamos, New Mexico. (Blackwell 1980, 01909)

LANL (Los Alamos National Laboratory) June 1, 1978. “Radioactive Waste Management Site Plan,” Los Alamos, New Mexico. (LANL 1978, 08905)

LANL (Los Alamos National Laboratory), J.W. Nyhan, L.W. Hacker, T.E. Calhoun, and D.L Young, June 1, 1978. “Soil Survey of Los Alamos County, New Mexico,” Los Alamos National Laboratory report LA-6779-MS, Los Alamos, New Mexico. (LANL 1978, 05702)

LANL (Los Alamos National Laboratory), R. Garde, E.J Cox, and A.M. Valentine, September 1982.

“Los Alamos DP West Plutonium Facility Decontamination Project 1978–1981,” Los Alamos National Laboratory report LA-9513-MS, Los Alamos, New Mexico. (LANL 1982, 06399)

LANL (Los Alamos National Laboratory), K.A. Balo, and J.L. Warren, March 1, 1986. “1985 Waste Management Site Plan,” Los Alamos National Laboratory document LA-UR-86-990, Los Alamos, New Mexico. (LANL 1986, 07419)

LANL (Los Alamos National Laboratory), May 1, 1991. “TA-21 Operable Unit RFI Work Plan for Environmental Restoration,” Los Alamos National Laboratory document LA-UR-91-962, Los Alamos, New Mexico. (LANL 1991, 07529)

LANL (Los Alamos National Laboratory) and W.D. Purtymun, January 1, 1995. “Geologic and Hydrologic Records of Observation Wells, Test Holes, Test Wells, Supply Wells, Springs, and Surface Water Stations in the Los Alamos Area,” Los Alamos National Laboratory report LA-12883-MS, Los Alamos, New Mexico. (LANL 1995, 45344)

LANL (Los Alamos National Laboratory) and K.H. Wohletz, May 1995. “Measurement and Analysis of Rock Fractures in the Tshirege Member of the Bandelier Tuff Along Los Alamos Canyon Adjacent to Technical Area 21,” Earth Science Investigations for Environmental Restoration—Los Alamos National Laboratory Technical Area 21. D.E. Broxton and P.G. Eller (Eds.), Los Alamos National Laboratory report LA-12934-MS, Los Alamos, New Mexico, pp. 19–31. (LANL 1995, 54404)

LANL (Los Alamos National Laboratory), D.E., Broxton, G.H. Heiken, S.J. Chipera, and F.M. Byers, Jr., May 1995. “Stratigraphy, Petrography, and Mineralogy of Bandelier Tuff and Cerro Toledo Deposits,” Earth Science Investigations for Environmental Restoration—Los Alamos National Laboratory Technical Area 21. D.E. Broxton and P.G. Ellers (Eds.), Los Alamos National Laboratory report LA-12934-MS, Los Alamos, New Mexico, pp. 33–63. (LANL 1995, 50121)

LANL (Los Alamos National Laboratory) and F. Goff, June 1, 1995. “Geologic Map of Technical Area 21,” Earth Science Investigations for Environmental Restoration—Los Alamos National Laboratory Technical Area 21. D.E. Broxton and P.G. Ellers (Eds.), Los Alamos National Laboratory report LA-12934-MS, Los Alamos, New Mexico, pp. 7–18. (LANL 1995, 49682)

LANL (Los Alamos National Laboratory) April 7, 1997. “Performance Assessment and Composite Analysis for Los Alamos National Laboratory Material Disposal Area G,” Los Alamos National Laboratory document LA-UR-97-85, Los Alamos, New Mexico. (LANL 1997, 63131)

LANL (Los Alamos National Laboratory), W. Soll, and K. Birdsell, February 1, 1998. “The Influence of Coatings and Fills on Flow in Fractured, Unsaturated Tuff Porous Media System,” Water Resources Research, Vol. 34, No. 2, pp. 193–202. (LANL 1998, 70011)

LANL (Los Alamos National Laboratory) May 22, 1998. “Hydrogeologic Workplan, Los Alamos National Laboratory,” Los Alamos National Laboratory document LA-UR-01-6511, Los Alamos, New Mexico.

(LANL 1998, 59599)

LANL (Los Alamos National Laboratory) November 19, 1998. “Installation Work Plan for Environmental Restoration Project,” Revision 7, Los Alamos National Laboratory document LA-UR-98-4562, Los Alamos, New Mexico. (LANL 1998, 62060)

LANL (Los Alamos National Laboratory) December 23, 1999. “Historical Building Assessment for the Department of Energy Conveyance and Transfer Project,” Los Alamos National Laboratory document LA-UR-00-1003, Los Alamos, New Mexico. (LANL 1999, 87442)

LANL (Los Alamos National Laboratory), S.L. Reneau, J.N. Gardner, A. Lavine, E.V. McDonald, C. Lewis, D. Katzman, G. Woldegabriel, D. Krier, D. Bergfelt, and J. Heikoop, May 1, 2002. “Paleoseismic Investigation of Trench EOC-2, Pajarito Fault Zone, Los Alamos National Laboratory, New Mexico,” Los Alamos National Laboratory report LA-13939-MS, Los Alamos, New Mexico. (LANL 2002, 82913)

LANL (Los Alamos National Laboratory), August 31, 2004. “Investigation Work Plan for Delta Prime Site Aggregate Area at Technical Area 21,” Los Alamos National Laboratory document LA-UR-04-5009, Los Alamos, New Mexico. (LANL 2004, 87461)

Montoya, G., July 22, 1987. ”Clay and Ductile Pipe Removal, TA-21, Area V,” Los Alamos National Laboratory memorandum to R. Garde (HSE-7) from G. Montoya (HSE-1), Los Alamos, New Mexico.

(Montoya 1987, 01138)

Tribby, J.F. May 8, 1947. “Fluid Waste Disposal at DP West,” Los Alamos Scientific Laboratory memorandum to E.R. Jette from J.F. Tribby, Los Alamos, New Mexico. (Tribby 1947, 01764)

Valentine, A., January 22, 1979. “Procedure for the Final Survey and Transfer of CMB-11 Areas at TA-21, DP West Decon H-1-6.” (Valentine 1979, 90514)

Table 2.3-1 Documented Releases in DP West Buildings

Building Area Description of Release Constituents of Concern

21-02 Room 201 Numerous leaks associated with a nitric acid tank located in the northeast corner. Many other releases reported but poorly documented.

Plutonium isotopes, nitrates

Room 205 Numerous spills of unknown contaminants. n/a

Room 208 Spill of molten uranium on floor 1950; numerous spills of plutonium solution.

Uranium isotopes Plutonium isotopes

Room 209 Spill of liquid plutonium solution on floor. Plutonium isotopes

Room 212 Spill on floor five times during 1959. Plutonium isotopes

Room 213 Dissolver section of Room 213 was located near the west exit just north of Room 218. Numerous spills of americium-241;

caustic solution spill.

Americium-241 Unknown associated with caustic solution

Room 218 Numerous spills of americium-241 and plutonium;

contaminated from spill in Room 213 which also spilled onto outside loading area; overflow of transport tank onto loading area; criticality incident in 1958.

Americium-241 Plutonium isotopes

21-03 Room 308 High number of plutonium solution spills. Plutonium isotopes

Room 320 Contamination tracked in from Room 308. Plutonium isotopes

Room 321 Contamination tracked in from Room 308. Plutonium isotopes

Room 322 Contamination tracked in from Room 308. Leak from five shipping containers.

Plutonium isotopes

21-04 Room 401-E Spills of uranium-235, plutonium-239, and fission products. Uranium-235 Plutonium-239

Room 406 Numerous spills of plutonium solution; spill of plutonium-238 in corridor enroute to Building 21-05.

Plutonium isotopes Plutonium-238

21-05 Room 500 High release rate (explosions) of plutonium-239…