NAS Areas of Concern - Radioactive Contamination
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Areas of Concern
Pier 3 Ramp 1 and Adjacent Parking Apron 4 Site 1 and 2 Former Radioactive Waste Storage Shack Area Building 5 Storm Sewer Lines and Manholes Building 400
The following sections summarize PRC's conclusions and recommendations derived form the radiological investigation at NAS Alameda.
General basis for recommendations are predicated on the following principles: (1) removal actions should be taken where there is high potential for human contact with intact radium sources (such as dials and illuminators identified during walkover surer) and for human contact with contaminated soil or storm sewer sediments; and (2) removal actions should be considered where surface activities may result in radiation doses to exposed personnel (non-occupationally qualified radiation workers) that exceed a specified action level. Remedial action levels for removal actions will be based on applicable or relevant and appropriate requirements (ARAR) (to be decided upon prior to remedial actions).
Alternatively, isolation of structures or systems may be appropriate where high remediation costs exceed benefits under conditions where (1) radioactivity is not producing detectable radiation exposure in normally occupied areas; (2) deed or lease restrictions are appropriate; and (3) excavation or exposure to activity is unlikely and can be minimized by engineering measures (and radiation exposure from a single inadvertent event is not likely to exceed 100 millirem [mrem]).
Warning signs or positive controls to prevent radiation exposure shall be put in place in public areas of sites based on the potential to exceed 100 mrem/yr (50 microrem per hour [µrem/hr] for occupational exposure or 11 µrem/hr for continuous occupancy).
Beta-emitting radioactive contamination was identified on Pier 3. The Navy removed the contaminated portion of the pier surface during the week of August 19, 1996 (Guiterrez-Palmanberg Inc. {GPI} 1996). The subcontractor that removed the contamination also performed a final status survey and took confirmatory concrete samples for laboratory analysis. No radioactivity was measured above the regulatory limits for beta-emitting isotopes during the final status survey (GPI 1996). Beta activities in the confirmatory concrete samples were also below regulatory limits (GPI 1996). No further action is recommended on Pier 3 for the identified radiological concerns.
No radiological contamination was identified in this area; therefore, no further action is recommended.
Nineteen anomalies were identified and eight sources were recovered during the survey of the northwest point of Site 1 (maximum activity 1.3 µCi). The location of anomaly FP04, which was not removed, has an exposure rate of approximately 300 µrem/hr at 1 meter from ground surface. Removal of the radiation sources at FP04 should be considered based on likely future access to the site. Access control measures are recommended around the area of anomaly FP04 to limit access to this location until the area can be excavated. Soils at several other locations in the northwest point of Site 1 demonstrated low levels of dispersed radioactivity. Although soils at these locations do not pose a radiation exposure hazard, they should be evaluated for potential removal.Because only the northwest point of Site 1 was surveyed for 100 percent coverage, further surveys of the remainder of Site 1 are recommended. Prior to the release of the area for unrestricted use, all identified anomalies posing an external radiation hazard should be removed. As an alternative, because the presumptive remedy for the Site 1 landfill is to cap it, an interim action for the Navy would be to control access to the Site 1 landfill until a remedial action has been decided upon. Capping of the landfill may preclude any further action at Site 1.
On the Site 1 jogging trail, six radioactive anomalies were identified and four sources were recovered (maximum activity of approximately 0.22 µCi). Because the exposure rates measured at 1 meter above the trail surface (maximum 8µR/hr) were barely distinguishable from background (5 to 6 µR/hr), these areas do not pose a radiation exposure hazards. However, at the anomalous locations, surface soils showed evidence of containing low levels of dispersed activity. The soils at these locations should be evaluated for potential removal.
No anomalies were identified on the Site 2 jogging trials (sic); therefore, no further action is recommended for these trails.
Eight radioactive anomalies were identified in the area around the location of the former radioactive waste storage shack in Site 2. All eight sources were recovered (maximum activity approximately 2.7 µCi). Area surface soils also showed evidence of containing elevated levels of dispersed radium-226 activity, approximately 6,000 times greater than background, The maximum exposure rate (at 1 meter above ground surface) in the area is about 17 µR/hr, approximately 3 times the background exposure rate. Further assessment of the extent of the soil contamination in the surrounding area of the former radioactive waste storage shack is recommended. Because of the high number of anomalies identified in such a small area, the soil contamination in the immediate area of the former radioactive waste storage shack should be excavated and removed. As an alternative, because the presumptive remedy for the Site 2 landfill is to cap it, an interim action for the Navy would be to control access to the contaminated areas of Site 2 until a remedial action has been decided upon. Capping of the landfill may preclude any further action at Site 2.
Beta-emitting radioactive surface contamination, in excess of release limits established by the U.S. NRC (U.S. NRC 1974), was identified in Building 5. In order to meet free release limits, decontamination of identified areas in Room 227C of the Bearing Shop should be performed. Prior to decontamination or during the waste characterization process, the radio isotope should be identified for the sludge-like material located on the floor and the contamination on the wall. Upon completion of the decontamination activities, a final status survey of the affected areas should be performed. Analysis of surface core samples may be necessary to determine that residual activity has not penetrated the floor or wall surfaces.At this time, radium contamination under the linoleum floor coverings in the Bearing Shop rooms cannot be ruled out. The survey methods implemented were not designed to detect low levels of alpha-emitting or radium chain contamination beneath floor covering material. The only way to survey the underlying floor surface for alpha radiation, with an acceptable detection limit less than the release limit, would be to first remove the floor coverings. If historical information cannot be provided as to the radiological condition of the floor prior to the laying of the linoleum floor covering, then removal of the floor covering and final survey of these areas is recommended.
The identified drain line in Building 5 that feeds storm sewer line F is contaminated with radioactive materials, most likely paint containing radium-226. Access to this drain line should be limited to personnel who are trained in radiation protection procedures. The exposed section of the contaminated drain line should be removed. Removal of the exposed section will be necessary in order for the Navy to release the building to unrestricted use. Removal of the subterranean section of the drain line is also recommended. Interim control of the se areas should be determined following the Navy RAD-10 guidance (U.S. Navy 1991b).
Alpha-emitting radioactive surface contamination, in excess of release limits established by the U.S. NRC (U.S. NRC 1974), was identified in Rooms 204 and 210 of Building 400. In order to meet free release criteria, decontamination of the identified areas should be performed. Upon completion of decontamination activities, a final status survey of the affected areas should be performed. Decontamination of the north wall of Room 204 poses a special problem due to the rough surface of the wall material. Removal of the pressed fiber-board wall material may need to (sic) performed in order to remove all traces of contamination.
As discussed in Section 6.2, radium contamination under the linoleum floor coverings in Room 203, 210, and 213 cannot be ruled out. The only way to survey the underlying floor surface for alpha radiation with acceptable detection limit less than the release limit would be to first remove the floor coverings. If historical information cannot be provided as to the radiological condition of the floor prior to the laying of the linoleum floor covering, removal of the floor covering and final surveys of these areas is recommended.
An area of increased gamma activity was identified on the concrete floor of the DU removal booth. The DU removal booth is located in Room 204. The surface contact activity on the floor is about 20 µR/hr above background, while the exposure rate at 1 meter above the anomalous area is about 3 µR/hr above background. This results in a maximum annual dose of 6 mrem/yr. No controls to limit access are necessary in the immediate area of the DU removal booth; however, removal of the identified contamination is recommended. A final status survey should be performed after decontamination activities are complete.
Several exposed drain lines inside Building 400 were identified as having elevated levels of gamma radiation. Internal contamination of these drain lines is most likely caused by paint containing radium-226. These lines will require removal prior to releasing the building for unrestricted use. Elevated levels of gamma radiation were also identified in the subterranean drain lines leading form the contaminated lines in Building 400 to the sanitary sewer manhole, R112. This drain line is most likely contaminated with paint containing radium-226. Removal of this line is also recommended. Investigation of the surrounding soil may also be indicated.(sic) Exposure precautions should be taken for the subterranean section of line, as described in Section 6.2.
Surfaces on several pieces of equipment in Building 400 were found to be contaminated with elevated levels of alpha-emitting radioactivity. These pieces of equipment were either decontaminated or the contaminated parts of the equipment were isolated and removed from the rooms. The resulting contaminated materials were labeled and placed in Building 5 for storage. Prior to disposition, additional surveys of this material may result in the reclassification of some items as suitable for free release, rather than disposal. This will ensure proper characterization of the waste stream and potentially identify pieces that may be disposed of as low-level radiation waste (LLRW). Materials meeting the unrestricted release criteria should be disposed of at a secure landfill and not recycled or surplused.
Several section of storm sewer line F and related manholes demonstrated elevated levels of gamma radiation. Figure 6-1 presents a color-coded diagram of the sections of the storm sewer lines and manholes that were surveyed and the approximate radium-226 point-source equivalent activity ranges in picoCuries (pCi). The elevated levels indicate the presence of sediments that are most likely contaminated with paint containing radium-226.
Remediation of the contaminated sections of storm sewer line F is recommended. Investigation of the surrounding soil may also be indicated.(sic) Because the sewer lines are not readily accessible, remediation to free release criteria may not be necessary. Remedial actions may include decontamination and/or removal of the identified sections of contaminated storm sewer line and manholes. In the event that a section of the contaminated line is broken, it is likely that the soil surrounding the line will also be contaminated. If removal activities are performed, all connecting lateral sections of the storm sewer line F and the soils under the lines should be thoroughly investigated.
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Copyright © 1998 NICHE Project