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The Borough plans to construct a recreation center on the former Landfill site. DOE’s Office of Legacy Management (LM), which is responsible for long-term surveillance of remediated former FUSRAP properties, wishes to assure that the near-surface soil of the former Landfill site does not contain residual deposits of contaminated soil that might be exposed as a result of these construction activities.

During the period of September 22-27, 2008, DeNuke Contracting Services, Inc. (DCSI) of Oak Ridge, TN performed a radiological survey at the former Middlesex Municipal Landfill site. The objective of this survey was to identify elevated surface radiation levels that may be indicative of residual deposits of radioactive material in the near-surface soil. The survey consisted of walkover gamma scans and limited sampling of locations identified by the scans.

This survey demonstrated that there are small areas of elevated, low-level surface radiation on the Landfill site. The contaminants at locations of elevated radiation include Ra-226, U-238, and Th-232; relative concentrations of these contaminants vary and the radionuclide mix in the southern portion of the Landfill does not appear to be uranium or thorium ore, as was the contaminant identified by previous surveys of the northern portion.

Elevated radiation levels were identified on only a small portion of the site; the remainder of the property does not exhibit direct radiation levels differing from the typical background levels for the area. Several locations of residual low-level contamination are on the previously remediated northern portion of the site; however, the radiological conditions on this area are within the DOE FUSRAP guidelines applicable at the time of the remedial action. Contamination is more extensive along the southernmost boundary and several of the generally elevated areas would not satisfy the DOE FUSRAP guidelines.

Although there are small areas of residual radioactive contamination on the site, the levels are such that, under conditions of current and proposed property use, the contamination does not pose a health risk to members of the public on or in the vicinity of the site.

Surveys and remedial actions performed by the DOE were limited to that potentially impacted 3 to 5 acre portion at the north end of the former Landfill. In 2001 and 2002, the State of New Jersey contracted for a radiological survey of the entire former Landfill site. That survey identified elevated radiation levels along the south boundary, near Pershing Avenue; the source of these elevated radiation levels was not determined and further characterization of the deposits was not performed.

The Borough plans to construct a recreation center on the former Landfill site. DOE’s Office of Legacy Management (LM), which is responsible for long-term surveillance of remediated former FUSRAP properties, wishes to assure that the near-surface soil of the former Landfill site does not contain residual deposits of contaminated soil that might be exposed as a result of these construction activities. Under contract with the S.M. Stoller Corp., during the period of September 22-27, 2008, DeNuke Contracting Services, Inc. (DCSI) of Oak Ridge, TN performed a radiological survey of the surface of the former Middlesex Municipal Landfill site. This report describes the survey approach and activities.

The objective of this survey was to identify elevated surface radiation levels that may be indicative of residual deposits of radioactive material in the near-surface soil of the former Middlesex Municipal Landfill site. Soil samples would be obtained at selected discrete locations of elevated radiation levels (if any) to determine the radionuclide(s) present and their concentrations. Where practical, the source of elevated direct radiation would be identified and removed by the sampling effort. If more extensive deposits were identified, the extent of these deposits would be determined and described in the report of findings.

The site surface is generally level, except along the eastern boundary, where the elevation decreases towards Bound Brook. In preparation for the survey, small trees, brush, and high weeds were cleared from the central portion of the site. Mature trees and other ground cover remain along the south and west perimeter fence, and there is heavy tree and ground vegetation along Bound Brook on the eastern part of the site. Individual trees and large bushes are also disbursed throughout the central and southern portions of the property. The presence of miscellaneous debris, scattered across the site, indicates that local residents continue to use the site for disposal of household trash.

The site is readily accessible to foot traffic and small motorized vehicles (e.g., ATV’s).

Based on historic operations and previous radiological surveys, the potential radiological contaminant is expected to be small pieces of ore, containing uranium and/or thorium in natural isotopic abundances and in secular equilibrium with members of the naturally occurring uranium and/or thorium decay series.

Survey Reference System

A 100-ft grid pattern was established over the site to provide a means for referencing measurement and sampling locations; this reference grid is shown in Figure 2. In addition, where conditions permitted, scans and sample locations were referenced to the New Jersey Planar Coordinate system, using instruments equipped with GPS-based logging capabilities.

Instrumentation

The primary instrument type used was a 2" x 2" Ludlum Model 44-10 sodium iodide (NaI) gamma scintillation detector, coupled with a Ludlum Model 2221 ratemeter/scaler readout/display instrument. This instrument combination was used for walkover gamma surface scans and for monitoring direct radiation levels at soil sampling locations. Based on an average general background count rate of 10,000 cpm, the walkover scan minimum detectable concentration (MDC) of approximately 2.5 pCi/g for Ra-226 (present in uranium ore, in secular equilibrium with uranium 238) and 2.5 pCi/g of Th-232 (in secular equilibrium with its decay series) was estimated using the guidance in MARSSIM and NUREG-1507 (Reference 8). This sensitivity enabled identification of small deposits of elevated activity, having an activity concentration of Ra-226 or Th-232, approximately twice the upper level in naturally occurring soil from this area of New Jersey.

Gamma Surface Scans

Gamma surface scans were performed to identify locations of residual surface activity. NaI gamma scintillation detectors were used for these scans. Scanning was performed by moving the detector in a serpentine pattern, while advancing at a rate of approximately 1.0 m per second. The distance between the detector and the surface was maintained within approximately 5 cm. Scan coverage for the property of interest was 100% of accessible areas. Audible signals were monitored and locations of elevated direct levels above 12,000 counts per minute (12 k cpm) were confirmed and marked for further investigation. Systems were equipped with global positioning system (GPS) sensors and data loggers to record scan position and data for statistical evaluation and graphical presentation.
Because the 2001/2002 survey identified only background radiation levels along the heavily vegetated eastern site boundary and the vegetation cover restricted access, that portion of the site was not included in this survey. Also, because of overhead vegetation and equipment malfunctions, logged scans with GPS assist could only be obtained from approximately half of the remaining site area.
A graphic display, typical for portions of the site where GPS/logged scans were obtained, is included in Figure 3 to illustrate the thoroughness of coverage. Blank areas on this figure represent surfaces that either were not accessible, due to surface conditions, or locations where overhead cover prevented GPS signal reception. The remaining portion of the site was scanned in a similar manner to achieve complete surface coverage.

Sampling

Localized shallow sampling, guided by monitoring of direct gamma level, was performed at five locations of elevated direct surface radiation. Sample locations are shown on Figure 4. To avoid disturbing the grassy area between the fence and Pershing Avenue, sampling was not performed at the two locations of highest discrete surface radiation (i.e., 100 k cpm and 120 k cpm). Attempts were made during sampling to identify and remove the source of elevated radiation. Following sampling, radiation levels at the surface and the bottom of the excavation were monitored to determine the effectiveness of source removal. Samples were packaged and submitted to Paragon Analytics, Inc. for gamma spectroscopy analysis in accordance with their contract with SM Stoller Corporation.

Gamma scans identified 8 small discrete locations of elevated direct radiation and 7 larger areas, ranging from about 250 ft2 to 2100 ft2, with generally higher near-surface radiation levels and containing multiple discrete elevated locations.

Several of the larger areas and individual locations with the highest direct radiation levels were located near the extreme southern boundary of the property. The highest discrete direct contact radiations levels of 120 k cpm and 100 k cpm were identified in the narrow grassy strip between the fence and Pershing Avenue. Other discrete locations in this general area ranged up to 90 k cpm. The dose equivalent level at the point of highest count rate identified by the scans was 70 microrem/h at contact and 25 microrem/h at 1 meter above the surface. For comparison, the background dose equivalent level in this area is approximately 5 microrem/h at a height of 1 meter.

There were also four elevated locations identified in the northwest portion of the site, in the vicinity of the area which was previously remediated. The highest discrete location was 72 k cpm. An area of generally elevated levels contained multiple discrete locations of ? 2 ft2 with a maximum level of 50 kcpm. The maximum concentration of Ra-226 in these samples is 135 pCi/g from the 6-10 inch depth at sample location 1; the sample from the 0-6 inch depth at this location contained 108 pCi/g of Ra-226. Concentrations of uranium in these samples are significantly lower than those of Ra-226. This combination of radionuclides differs from that in samples from the remediated northern portion of the Landfill and raises doubt as to whether the contaminants in the southern and northern portions of the site are from the same process or source. Based on the extent of contamination indicated by the scans and the limited soil sampling results, it is probable that four general surface areas along the south perimeter contain Ra-226 concentrations that exceed the average FUSRAP Ra-226 guidelines in effect at the time of remediation. In addition, small areas of surface soil along the south boundary contain Ra-226 concentrations in excess of the more recent hot-spot guideline for localized contamination of 50 pCi/g. Other locations satisfy the FUSRAP concentration guidelines, which were in effect during the mid 1980’s at the time of the Landfill remedial actions. Guideline concentrations for radionuclides in soil have not been developed for the Landfill, based on DOE criteria and current site use. Therefore, no comparison of radiological conditions with current guidelines is possible.

Radiation exposure to site occupants under recreational and industrial use scenarios would be from direct radiation. For an industrial scenario, the maximum time on site would be 2,000 hours/y. Based on a maximum direct radiation level at 1 meter above the surface of 20 microrem/h above background, the direct radiation for an annual 2,000 hour exposure period would be 40 millirem. This is within the DOE basic dose limit of 100 millirem/y for the general public. Moreover, this represents an individual small location, and it is unlikely that a person would be at this location for a full 2,000 hr during the year. Recreational use involves less time on site and proportionally lower direct radiation exposure. During the period of September 22-27, 2008, DeNuke Contracting Services, Inc. (DCSI) of Oak Ridge, TN performed a radiological survey of at the former Middlesex Municipal Landfill site. The objective of this survey was to identify elevated surface radiation levels that may be indicative of residual deposits of radioactive material in the near-surface soil. The survey consisted of walkover gamma scans and limited sampling of locations identified by the scans.

This survey demonstrated that there are small areas of elevated, low-level surface radiation on the Landfill site. The contaminants at locations of elevated radiation include Ra-226, U-238, and Th-232; relative concentrations of these contaminants vary and the radionuclide mix in the southern portion of the Landfill does not appear to be uranium or thorium ore, as was the contaminant identified by previous surveys of the northern portion.
Elevated radiation levels were identified on only a small portion of the site; the remainder of the property does not exhibit direct radiation levels differing from the typical background levels for the area. Several locations of residual low-level contamination are on the previously remediated northern portion of the site; however, the radiological conditions on this area are within the DOE FUSRAP guidelines, applicable at the time of the remedial action. Contamination is more extensive along the southernmost boundary and several of the generally elevated areas would not satisfy the DOE FUSRAP guidelines. Guideline concentrations for radionuclides in soil have not been developed for the Landfill, based on DOE criteria and current site use. Therefore, no comparison of radiological conditions with current DOE derived volumetric guidelines is possible.
Although there are small areas of residual radioactive contamination on the site, the levels are such that, under conditions of current property use, the contamination does not pose a health risk to members of the public on or in the vicinity of the site.