Based on our observations, USACHPPM personnel performed a thorough and effective survey of the buildings. While the density of the data collected during the landfill survey did not approach the level of that collected during building surveys, the overall coverage appeared to be adequate. All surveys were performed in a manner consistent with the established USACHPPM industrial radiation survey protocols (Edge, 1995).

IDNS building survey results identified no radioactive contamination in any of the areas surveyed. These results concur with the preliminary findings of the USACHPPM survey. Also, IDNS landfill #7 gamma survey results identified no areas where the surface gamma count rates exceeded the mean background count rate by three standard deviations of the mean. Gamma spectrum analysis and liquid scintillation results for the water sample split collected from the landfill #7 drainage collection system found no radiological contamination in the effluent. Finally, the gamma spectrum analysis results for the water samples collected from the gas vents on landfill #7 detected no elevated or unusual levels of radionuclides.

BACKGROUND

Site Description & History

The former Fort Sheridan is a 712-acre military installation located north of Chicago on the north shore of Lake Michigan. From its establishment in 1887, the base was used primarily for military training and maintenance and support to reserve units in the area. For twenty years, beginning in the early 1950s, Fort Sheridan housed NIKE anti-aircraft missiles. The installation served as a maintenance and service center for all other NIKE sites in the Midwest.

In 1988, the Base Closure and Realignment (BRAC) legislation was passed, closing specific U.S. military installations throughout the United States. Fort Sheridan fell victim to this legislation in 1992 resulting in partial closure of the site; the Army retained 100 acres in order to maintain its reserve units while the Navy purchased 200 acres in the southeastern portion of the site. An additional 200 acres, including a historic district, may eventually be available for sale to outside investors.

During the pre-release investigative process for the facility, the U.S. Army informed the Illinois Environmental Protection Agency (IEPA) that the potential for radioactive contamination existed at the site. The Army revealed that radioactive materials had been used and disposed of at the facility and further, that the site currently housed licensed radioactive materials. As part of their internal investigation, the Army contracted with the U.S. Army Center for Health Promotion and Preventive Medicine, Industrial Health Physics Program (USACHPPM) to perform a scoping survey of potentially contaminated buildings and landfills. Likewise, IEPA requested assistance from IDNS in observing and evaluating the radiological survey protocols used by the USACHPPM staff.

Radiological History and Current Status

Results of a historical search (Kwok, 1995), contracted by the Army, identified the areas of radiological interest: buildings 42, 128, 142, 379, 380, 538, and 565; the NIKE silos, identified as areas 908, 909, 910; and landfill #7. Historical documents also indicated that of the seven landfills on the base, only landfill #7 was used to dispose of gauges, dials and other articles reported to contain radioactive materials/sources.

At one time building 380 contained a depleted uranium weapons training device. Building 42 was used, both historically and recently, for the storage, shipping and receiving of radioactive commodities at Fort Sheridan. Building 142 was used as a temporary storage site for radioactive materials being transferred to other military training centers. Building 128 was historically used as the NIKE maintenance shop. However, documentation indicates that maintenance was not performed on nuclear warheads (Kwok, 1995). Buildings 379, 380, 538, and 565 are currently used to store gauges and other devices containing licensed radioactive materials. Building 128 is currently used as a vehicle motor pool and maintenance shop by the Army. All of the identified buildings are currently utilized by either Army or Navy personnel.

The NIKE silos are located on the northwest corner of the installation and are currently unused. Other structures which housed the NIKE missile operational facilities were razed in 1974 (Kwok, 1995). The remaining silos are covered, but filled with rain water. The silos are scheduled to be drained in the spring of 1996 when water and sludge sampling will be performed by USACHPPM.

Landfill #7, originally a natural ravine, lies at the southeast end of Fort Sheridan and covers approximately three acres. It was established in the 1940's and is the only landfill documented to contain radioactive dials, gauges, electron tubes, instruments and other articles no longer working or useful, as well as other non-radioactive waste (Kwok, 1995). Landfill #7 was closed and capped about 1978. The landfill #7 ravine was a natural drainage system for rain water and, prior to its use as a landfill, an engineered rainwater drainage system was installed. This drainage system still functions and continues to drain surface and ground water from the installation into Lake Michigan.

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RADIOLOGICAL ASSESSMENT

Overview

At the request of the IEPA, staffers from the IDNS, Office of Environmental Safety (OES), Division of Environmental Monitoring (DEM), met with BRAC, IEPA, and USACHPPM personnel and the contracted health physics technicians from Numanco Nuclear Support Services. The IDNS had been requested to review protocols and observe the procedures used by USACHPPM during survey and sampling operations in buildings 42, 128, 142, 379, 380, 538, 565 and landfill #7.

On August 30 and 31, 1995, IDNS staffers met with the USACHPPM representative, Dave Hayes, and his staff to observe the radiological scoping surveys of buildings 128 (vehicle engine maintenance shop), 142, 538, 379 and 565. Based upon observation and review of the preliminary data collected, IDNS representatives were satisfied that the scoping survey performed by USACHPPM was thorough, accurate and reproducible. As part of the evaluation process, IDNS staffers performed independent verification surveys on gridded areas which, in our opinion, had the most potential to retain contamination from radioactive materials use (Attachment A). These grids generally contained building features, such as floor cracks, drains or ductwork, that would make decontamination difficult.

On September 6, IDNS staffers met with USACHPPM, BRAC, IEPA and USEPA personnel to observe the radiological survey and sampling activities on landfill #7 being performed by USACHPPM staff. The scoping survey performed by USACHPPM was adequate and consistent with their procedure. Soil sampling was also performed according to approved USACHPPM industrial radiation survey protocols (Edge, 1995). A water sample was collected from the drainage collection system which runs under the existing landfill. IDNS observed all survey and sampling activities and obtained a sample split from the landfill drainage collection system.

On November 7 and 8, IDNS staffers performed a comprehensive radiological survey of landfill #7 to verify the results of the USACHPPM scoping survey. The IDNS survey included measurement and mapping of surface gamma radiation levels, and the measurement of radiation dose rates at several points within the landfill. On November 30, USACHPPM staff collected water samples from seven gas vents on landfill #7 and submitted sample splits to IDNS for isotopic analysis.

Survey Procedures: Buildings

IDNS staffers toured all of the buildings that had contained and continue to contain radioactive sources. Building 128, because of its historical background as the NIKE maintenance area, was chosen for observation of the complete scoping survey procedure. IDNS staffers reviewed written protocols, observed instrument source checks, gridding, surveying techniques and data handling. Additionally, IDNS performed spot check surveys of grids that had the most potential to retain contamination from radioactive materials use. IDNS performed alpha scans using Ludlum Model 12 portable rate meters with Ludlum Model 43-65 alpha scintillation detectors. Beta/gamma scans were performed using Ludlum Model 12 rate meters with Ludlum Model 44-9 pancake detectors. Measurement of gamma exposure was performed using a Bicron Low Energy (LE) exposure rate meter.

Survey Procedures: Landfill #7

IDNS staffers observed the walk-over survey performed by USACHPPM staff, as well as their soil sampling procedure. To augment USACHPPM's survey, IDNS scheduled and performed a gamma survey. The IDNS staff conducted this survey utilizing an integrated global positioning (GPS) and gamma radiation detection system, developed by IDNS/DEM staff.

The entire system consisted of a roving GPS/gamma-survey package and a base station transmitter/receiver. The roving unit combined a 9 channel Trimble Pro-XL with a TDC1 data logger for the global positioning and a Ludlum scaler/rate meter with a 2x2 NaI scintillation detector for gamma detection. The rover simultaneously logged gamma count rates and position data. The fixed base station, located at a known coordinate site near the landfill, was used as a reference point for differential correction of the rover unit data.

The rover instrumentation was mounted on a four-wheeled all-terrain vehicle in a manner that allowed for consistent, near-surface scanning of the entire area of interest. To the extent possible, areas not accessible to the survey vehicle were measured on foot utilizing the same instrumentation mounted on a backpack. Due to wet, swampy conditions, some areas of the site remained inaccessible.

Landfill #7 Mapping

Since IDNS was not able to acquire a digital copy of a site map of landfill #7, a copy of the plat map for the entire installation was obtained from the U.S. Army Corp. of Engineers. The plat map provided the coordinates of survey points which were used to digitize a general outline of the area of interest. These points were imported into an Arc/Info geographic information program to generate a map of landfill #7 in relation to the entire base.

As part of the initial GPS/gamma survey, IDNS used one of the known coordinate stations nearest the landfill as the fixed base station site. Using data collected by the fixed base station data collected during the gamma surveys, Trimble's Pathfinder software differentially corrected the rover position data. Differential correction allowed for position accuracy in the sub-meter range. The data was then used to create an Arc/Info coverage for the landfill that would accurately display all of the gamma data collected. Gamma data was sorted and displayed to identify the location and distribution of peak gamma values for the property. These values were compared to background gamma values from nearby unaffected properties.

RADIOLOGICAL SURVEY RESULTS

The radiological survey results for building 128 (Attachment A) indicate all grids surveyed to be free of both fixed and removable radiological contamination. The radiation exposure rates, at various locations within the building, were consistent with typical background for the interior of block or brick buildings (20 µR/hr).

Although some areas of landfill #7 were inaccessible and some position data was not correctable due to satellite signal loss, the available data met the USEPA's quality assurance guidance document's (QAM/005) definition for completeness. That is, greater than 90% of data collected were available for use in analysis of site conditions. Considering this, the radiological survey results of landfill #7 indicate that no points were identified where gamma count rates exceeded 3 standard deviations above the mean background count rate. Computer generated survey maps clearly demonstrate these findings. The peak count rate on the parcel was approximately 13,967 cpm, far less than twice the natural background rate. The gamma dose rate, measured one meter from the surface, at various locations on the survey site, was approximately 10 µR/hr which is also consistent with normal background dose rates. Due to the fact that no truly elevated gamma levels were identified, no soil samples were collected.

Results for gamma spectrum analysis and liquid scintillation analysis for the water samples taken from the landfill drainage collection system and gas vents indicate the water contained no elevated or unusual levels of radionuclides. The radionuclides normally present in water were identified at or below their naturally occurring concentrations.

Based on review of the available radiological survey data, IDNS/OES suggests radiological parameters at this site to be within the normal range of background.

FUTURE ASSESSMENTS

Radiological Assessment of NIKE Silos

Additional IDNS/DEM involvement at the former Fort Sheridan is planned for the Spring of 1996. Water samples splits will be collected from the currently flooded NIKE silos. After the water samples are analyzed to determine disposal requirements, the remaining sludge on the silo floors will be split-sampled and analyzed. IDNS/DEM will be willing to provide any additional assistance, if requested.

REFERENCES

Edge, H., 1995. Report prepared for the Department of the Army, U.S. Army Center for Health Promotion and Preventive Medicine (PROV). Industrial Radiation Survey No. 27-83-2859A-95, Historical Data Review, Fort Sheridan, IL. January 1.

Edge, H., 1995. Report and addendum prepared for the Department of the Army, U.S. Army Center for Health Promotion and Preventive Medicine (PROV). Industrial Radiation Survey No. 27-83-2859B-95, Industrial Radiation Survey Protocols, Fort Sheridan, IL. January 1.

Kwok, S., 1995. Report prepared for USACHPPM (PROV). Base Realignment and Closure (BRAC) Historical Record Search. March.

*GRID# LOCATION               DIRECT READINGS       EXPOSURE RATE                                                     

                            ALPHA    BETA/GAMMA      at 1 meter                                                      

                           net cpm     net cpm         uR/hr



F 3 B  drainage grate, floor  0           0             20

F 1 E  crack, floor           0           0             20

F 3 J  bldg., base support    0           0             20

F 4 P  overhead door, S.      0           0             20

F 6 N  bay, S. E.             0           0             20

*USACHPPM#

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