This appendix compares the input tritium concentrations used in the risk assessment with site-specific data from special studies and with information that is provided in the 1995 LBNL Site Environmental Report [Thorson, 1996]. It includes a summary comparison for air, rain water, surface water, soil and sediment, vegetation and other biota, and urine measurements. Table F-1 provides a summary comparison of the estimates and measurements.

Table F-1
Estimated and Measured Tritium Levels

Rain water yields a useful measure of tritium levels in atmospheric water. During the rainfall season, generally October through April, rainwater is collected monthly or during periods of significant rainfall [Thorson, 1996]. During 1995, rainwater was collected at six locations on site and analyzed for tritium. In Zone 1 rain water was collected at a rain gauge at Building 75 and analyzed for tritium. At this site, tritium was always detected in varying amounts, ranging from a low of 77 Bq/L to a maximum of 496 Bq/L, with an average of 290 Bq/L, which we consider representative of Zone 1.

In Zone 2 most rain water samples are below the detection limit. At Building 4 (200 m southwest of Building 75), one sample was as high as 24 Bq/L and at location ENV-B13D on the hill below Lawrence Hall of Science one sample was 52 Bq/L. We estimate from the samples reported in the 1995 Site Environmental Report that the average tritium concentration in Zone 2 rainwater is about 20 Bq/L.

There was one rain water sample location in Zone 3 (ENV13B), and in 1995 it did not have a sample above the detection limit.

See Table F-1 for comparison of rain water sample measurements for 1995 with the risk assessment estimates.

The 1995 Site Environmental Report lists 11 creeks in the LBNL vicinity that were sampled for tritium. Of these, five had no detectable levels of tritium and six had tritium levels above the detection level. These findings are discussed below according to the zone with which the runoff from that creek is associated.

Chicken Creek, which is associated with Zone 1 and drains from the area near Building 75, had average tritium levels of 44 Bq/L and a maximum reported level of 180 Bq/L. Creeks associated with Zone 2 include Botanical Garden Creek, Claremont Creek, North Fork of Strawberry Creek, No-Name Creek, Ravine Creek, Ten-Inch Creek, and Wildcat Creek. Samplings from these creeks averaged no greater than 15 Bq/L. Lower Strawberry Creek, which flows into Zone 3, had average tritium levels no greater than 10 Bq/L in 1995.

Routine storm-water samples are also analyzed for the presence of tritium. Tritium values range from none detected at the North Fork of Strawberry Creek to 103 Bq/L at 69-Storm Drain Manhole, an influent site near the NTLF. Other samples of storm-water runoff in the vicinity of NTLF were in the range of 32 Bq/L to 74 Bq/L.

See Table F-1 for comparison of surface water sample measurements for 1995 with the risk assessment estimates.

During 1995, soil samples were taken from two onsite sampling locations and one off-site environmental monitoring station and analyzed for tritium. The soil samples correspond to Zone 2. These samples averaged 3 Bq/kg. Sediments collected in Chicken Creek, which are assumed to be associated with runoff from Zone 1, had observed tritium levels of 44 Bq/kg. Sediment levels in the North Fork of Strawberry Creek, which are assumed to be associated with Zone 2, had tritium levels of 2.6 Bq/kg.

See Table F-1 for comparison of soil and sediment sample measurements for 1995 with the risk assessment estimates.

The 1995 Site Environmental Report indicates a tritium plume in the vicinity of Buildings 75, 76, 77, and 78. The source of the tritium is emissions from the NTLF stack. The maximum reported concentration of tritium detected in monitoring wells in 1995 was 277 Bq/L. Thus the average concentration of tritium in ground water in Zone 1 is assumed to be 280 Bq/L. Tritium has not been detected in groundwater samples from monitoring wells near the site boundary. Since most of the monitoring wells in Zone 2 show no detectable level of tritium, the average concentration of tritium in Zone 2 is assumed to be about 10 Bq/L. (See Table F-1 for the comparison.)

Menchaca [1996a] has made measurements of tritium levels in foliage samples in trees from eight locations within LBNL. In trees from Zone 1 she found tritium levels ranging from 350 to 2900 Bq/L (assumed average of 1600 Bq/L). The highest level corresponds to a tree just two meters from the NTLF stack. In Zone 2, Menchaca reported tritium levels at distances of 100 to 300 meters from the stack ranging from 23 to 180 Bq/L, with an average of 92 Bq/L. Menchaca [1996b] has also reported on measured tritium activity in excreta, milk, and pasture for goats grazing at LBNL. These tritium activities range from none detected to as high as 55 Bq/L, with an average on the order of 20 Bq/L. In the Site Environmental Report [Thorson, 1996] vegetation samples from the area surrounding the Building 85 site were reported to have tritium levels in the range of 12 to 670 Bq/L, with an average of about 200 Bq/L. We combined these data to estimate the tritium level in Zone 2 to be of the order of 100 Bq/L. See Table F-1 for comparison of vegetation sample measurements for 1995 and 1996 with the risk assessment estimates.

LBNL monitors the level of tritium exposure for employees by taking and analyzing urine samples from employees working near the NTLF and at other locations. During the period of March-June 1995 samples of urine were collected weekly from workers in Buildings 75, 75B, 69, 26, 76, and 90. Tap water samples from the East Bay Municipal Utility District (EBMUD) water supply were analyzed concurrently. Figures F-1 and F-2 show the weekly distribution of tritium activity (reported in Bq/L) in Zone 1 and Zone 2, respectively.

Tritium concentrations in urine samples collected in Zone 1 (Buildings 69, 75 and 75B) during the above period ranged between 189 Bq/L and 4.4 Bq/L with an average of 48 Bq/L. The tritium concentrations collected in Zone 2 (Buildings 26, 76, and 90) during the above period ranged between 90 Bq/L and 1.5 Bq/L with an average of 20 Bq/L. The estimated values of these concentrations for the risk assessment were 468 Bq/L and 28 Bq/L, respectively, as shown in Table 4-15.