Ground-water contribution to dose from past Hanford operations

Abstract

The Hanford Environmental Dose Reconstruction (HEOR) Project is being conducted to estimate radiation doses that populations and individuals could have received from Hanford Site operations from 1944 to the present. Four possible pathways by which radionuclides originating in ground water on the Hanford Site could have reached the public have been identified: 1) through contaminated ground water migrating to the Columbia River; 2) through wells on or adjacent to the Hanford Site; 3) through wells that draw some or all of their water from the Columbia River (riparian wells); and 4) through atmospheric deposition resulting in the contamination of a small watershed that, in turn, results in contamination of a shallow well or spring. These four pathways make up the "ground-water pathway , " which is the subject of this study. The objective of the study was to assess the extent to which the groundwater pathway contributed to radiation doses that populations or individuals may have received from past operations at Hanford. The assessment presented in this report was performed by 1) reviewing the extensive •literature on ground water and groundwater monitoring at Hanford and 2) performing simple calculations to estimate radionuclide concentrations in ground water and the Columbia River resulting from groundwater discharge. Radiation doses that would result from exposure to this ground water and surface water were calculated. The study conclusion is that the groundwater pathways did not contribute significantly to dose. Compared with background radiation in the Tri-Cities {300 mrem/yr), estimated doses are small: 0.02 mrem/yr effective dose equivalent from discharge of contaminated ground water to the Columbia River; 1 mremjyr effective dose equivalent from Hanford Site wells; 11 mremjyr effective dose equivalent from riparian wells; and 1 mrem/yr effective dose equivalent from the watershed. Because the estimated doses are so small, the recommendation is that further work on the groundwater pathway be limited to tracking ongoing groundwater studies at the Hanford Site. ix # xiv The maximum dose estimated with a simple calculation for the watershed pathway was 1 mrem/ yr effective dose equivalent (during 1945) for a range of possible parameters used. Ruthenium-106 was the only radionuclide predicted to reach the hypothetical well or spring through the shallow groundwater system in significant concentrations. CONCLUSIONS AND RECOMMENDATION Analyses of the groundwater pathways led to the conclusion that gro~nd water did not make a significant contribution to dose during the study period, 1944 to the present. The dose estimates are small compared with doses from average natural background radiation (300 mrem/yr) in the Tri-Cities (Jaquish and Bryce 1990). People in Richland, Pasco and Kennewick who get their drinking water from the Columbia River would be the primary group potentially exposed to groundwater discharges to the river. Both the dose estimates from published literature and calculations performed to address the o...

Evaluation of groundwater monitoring results at the Hanford Site 200 Area Treated Effluent Disposal Facility

“…Estimates based on the tracking of contaminant plume movement suggest average linear flow velocities of 0.2 to 2.7 m * day-' in the general vicinity of the TEDF and 200 East Area (Freshley and Graham 1988;Freshley and Thorne 1992). However, these estimates are averages over a large region within which groundwater flows in the more-permeable Hanford formation.…”

200-BP-5 operable unit treatability test report

“…A general summary of past monitoring activities, focusing on 200 Area operations, is reported in Ground-Water Contribution to Dosefrom Past Hanford Operations (Freshley and Thorne 1992). Over the years, sample analytical techniques, as well as analytes of interest, have been modified.…”

“…Gross beta has been measured from the beginning of monitoring activities to provide indications of liquid effluent migration to groundwater from disposal facilities. The methodology for routine gross beta analysis was refined to improve the detection limit from 300 pCi/L in 1945, to 150 pCi/L during the 1950's, to 80 pCi/L in 1959, to 16 pCi/L in the mid-1980'~~ and to 4 pCi/L in 1991 (Freshley and Thorne 1992). In 1959, Bierschenk (1959a), reported that any groundwater sample that exceeded 100,000 pCi/L for gross beta was analyzed for 6oCo, 137Cs, and %r.…”

Nonradiological chemical pathway analysis and identification of chemicals of concern for environmental monitoring at the Hanford Site

“…It is estimated that, from 1944 to 1989, approximately 444 billion gallons of liquid were discharged to the ground through disposal trenches, cribs, and ponds (Freshley and Thorne 1992). The primary pollutants found in the numerous plumes located onsite include nitrate, fluoride, chromium, cyanide, carbon tetrachloride, chloroform, trichloroethylene, 3H %o, ?3r, V c , '?I, 137Cs, and uranium (Dresel et al 1993).…”