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wind patterns. Accordingly, the sampling location proximate to the west property boundary is located such that: it is virtually unaffected by the valley wind patterns Bind is expected to yield airborne particulate concentrations uninfluenced by the licensed facilities. iv. Addendum: The above rationale for the use of the sampling location proximate to the west property boundary is considered valid when viewed in its intended context concerning the establishment of a site background for the licensed facilities, however concerns have been voiced about the potential undue influence of non-licensed facility radiation sources on this location. A review is now in progress to address those concerns. In the interim the sampling location offsite on Pine Ridge Road will be used as a background level because it is definitely not affected by either the licensed facilities or non-licensed radiation sources. Pathways A. External Dose - Direct Gamma Radiation The mineralogy surrounding the licensed facilities makes the determination of a "net" dose for gamma radiation from the licensed facilities difficult. The mineralogy of the opposing valley slopes at the site is quite different. Specifically, the valley side east-northeast o:E the site is much younger than the valley side west-northwest of the site. The age of the east-northeast side is on the order of millions of years, while the west-northwest side is about 4 to 4.5 billion years old. Needless to say, this leads to a vastly different mineralogy. The e<ist- northeast side is comprised mostly of sandstones, mudstones, clay and conglomerates, while the we:st- northwest side is made ug of metamorphosed gnei.sses and schists. Geology types such as sandstones, muclstones, and clays are historically associated with higher '"background" gamma counts than the metamorphosed types. This difference in mineralogy substantially limits the use of a thermoluminescent dosimeter (TLD) for background subtraction. To address this problem, Cotter F~roposed the placement of ten TLDs on the east-northeast valley side for a period of one year. This proposal was approved by Radiation Control and monitoring began on April 1, 1988. The one year monitoring period was completed in 1989 and the average annual background gamma radiation exposure for the ten locations studied was 184 mRem. A gamma dose is not attributed to the licensed facilities and is not included in the offsite dose commitment because the background study data of 184 mRem/yr exceeds the 158 mRem/yr calculated from monitoring data collected from