ESH-19 personnel collected soil and single-stage water samples around the perimeter of Area G at Los Alamos Nationrd Laboratory to characterize possible contaminant movement through surface-water mnoff. These samples were anal yzed for tritium, total uranium, isotopic plutonium, americium-241 (soil only), and cesium-137. The metals, mercury, lead, and barium, were analyzed using xray fluorescence. Elevated levels of tritium (as high as 117,200 pCi/L) were found in soil samples afong the eastern half of the north side of Area G. To the east and south of the transuranic waste pads, the soil samples showed slight increases (300& 5000 pCi/L) above baseline tritium levels (100-1000 pCi/L for Area G soils). Only one single-stage water sample had a tritium activity greater than 2000 pCi/L. Although we propose two subsurface-to-surface tritium migration mechanisms, we do not know how well our sample results reflect possible fluctuations in the Area G near-surface tritium distribution. The uranium soil concentrations had an average vahse of 2.59 + 0.70~@g. For soil samples, the average plutonium-238 activity was 0.28 + 0.80 pCi/g and the average for total phstonium-239 and-240 was 0.21 * 0.51 pCi/g. The locations of elevated plutonium readings in soil samples were consistent with the history of plutonium disposal at Area G, which was also reflected in the americium-241 results. Cesium-137 activities in soils had a wide distribution and ranged from 0.019-2.38 pCi/g. Soil mercury was detected in only 5 out of 83 samples, with the highest value at 6.1 pg/g. Other metal concentrations were found within natural background ranges. EXECUTIVE SUMMARY Area G, in Technical Area 54, has been the principaJ facility at Los Alamos Nationat Laboratory for the storage and disposal of low-level and transuranic (TRU) radioactive waste since 1957. Our investigation focused principally on the possibility of contaminated sediment movement through surface-water runoff out of the site perimeter. Soil samples were analyzed for tritium, total uranium, isotopic plutonium, americium-241, and cesium-137. The metals, mercury, lead, and barium, were analyzed using x-ray fluorescence. Filtered-water fractions from singlestage collectors were analyzed for tritium, isotopic plutonium, total uranium, and cesium-137. Filtered-sediment fractions were analyzed for isotopic plutonium only. Elevated levels of tritium (as high as 117,2W pCi/L) in soil were found for sampling locations along the eastern half of the north side of Area G, To the east and south of the TRU pads, the soil samples showed slight increases (3000-5000 pCfi) above baseline tritium levels (100-1000 pCti for soils in Area G). Six single-stage water samples had tritium activities over 1000 pCi/L, but in FY 93 only one single-stage water sample had a tritium activity greater than 2000 pCi/L. Two primary mechanisms, vapor-phase transport or capillary action, may allow tritium to move from subsurface soils to surface soils. Tritium's residence time in surface soils is unknown, however, and we d...

Location of Six surface soils were also submitted for metal analyses. These data were included with similar data generated for soil samples collected during FY 94 and compared with metals in background samples collected at the Area G expansion area. I List of TablesElevated levels of tritium (as high as 105,000 pCi/L) were found in perimeter soil samples during FY 95. Five single-stage water runoff samples (out of a total of 131 collected) had a tritium activity greater than 1000 pCi/L. The tritium concentrations in soils were substantially lower than those found during corresponding sampling accomplished in FY 94, but similar to tritium levels in soils collected during FY 93. Although we propose two major subsurface-to-surface tritium migration mechanisms, we do not know how well these surface sample tritium data reflect the true Area G near-surface soil tritium distribution.For soil samples, the average plutonium-238 activity was 0.539 pCi/g, whereas for plutonium-239 the average activity was 0.343 pCi/g. The locations of elevated plutonium readings in soil samples were consistent with the history of plutonium disposal at Area G, which was also reflected in the americium-241 results. Americium-241 on soils had a mean concentration of 0.202 pCi/g. Cesium-137 activities in soils had a wide distribution and ranged from 0.02 to 1.76 pCi/g. The uranium soil concentrations had an average value of 2.67 pg/g and were uniformly distributed around Area G.Of the ten metals analyzed on six perimeter soils collected around Area G, all were within the baseline concentrations for metals established from the soil sampling done in the undisturbed Area G expansion grid.Baseline or local background concentrations for future disposal operations were established for metals and radionuclides by a sampling program conducted in the proposed Area G expansion area during FY 93 and 94.Considering the amount of low level radioactive waste that has been disposed of at Area G, there is evidence of only low concentrations of radionuclides on perimeter surface soils. Consequently, little radioactivity is leaving the confines of Area G via the surface water runoff pathway. EX:ECUTIVE SUMMARYArea G, in Technical Area 54, has been the principal facility at Los Alamos National Laboratory for the storage and disposal of low-level, solid mixed, and transuranic (TRU) radioactive waste since 1957. Our investigation during FY 95 focused on defining whether surface water has moved contaminated sediments out of the Area G site perimeter. Soil samples were analyzed for tritium, total uranium, isotopic plutonium, americiu~n-241, and cesium-137. Ten metals-silver, arsenic, barium, beryllium, cadmium, chromium, mercury, nickel, lead and antimony-were analyzed on soils using standard analytical chemistry techniques (EPA SW-846). Filtered-water fractions from single-stage collectors were analyzed for tritium. Filtered-sediment fractions of the single-stage samples were analyzed for isotopic plutonium only.Elevated levels of tritium (as high as 90,500 p ...

List of Figures List of Tables ABSTRACTHazardous and Solid Waste Group @SH-19) personnel collected soil and single-stage water samples around the perimeter of Area G at Los Alamos National Laboratory (LANL) during FY96 and 97 to characterize possible radionuclide and metals movement out of Area G through surface water and entrained sediment runoff. Soil samples were analyzed for percent moisture, tritium, isotopic plutonium, americium-241, and cesium-137. The sediment portion of the single-stage water samples were analyzed for 13 metals

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