Scientific Investigations Report 2008–5089
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2008–5089
Wastewater disposal sites at INL facilities have been the principal sources of radioactive- and chemical-waste constituents in water from the Snake River Plain aquifer and in perched-water zones at and near the INL. In the past, wastewater disposal sites included infiltration ponds and ditches, evaporation ponds, drain fields, and disposal wells. Solid and liquid wastes buried at the RWMC (fig. 1) also are sources of some constituents in ground water.
Contractors at each INL facility collect radioactive- and chemical-waste-disposal data. Historical radioactive-waste-disposal data presented in this report were obtained from a series of radioactive-waste-management information reports (French and others, 1997b; French and Taylor, 1998, and French and others, 1999b). Chemical-waste-disposal data were obtained from a series of nonradiological-waste-management information reports (French and others, 1997a; 1998; 1999a). Since 1999, no formal program has been in place to compile annual amounts of constituents discharged at each facility (Richard Kauffman, U.S. Department of Energy, oral commun., 2005); however, the INEEL Site Environmental Reports (Stoller Corporation, 2002a, 2002b, and 2002c) provide some radioactive waste disposal data for 1999–2001. Amounts and types of radioactive- and chemical-wastes discharged at the various INL facilities are not published for 2002–05 and are not presented in this report.
Since 1952, low-level radioactive, chemical, and sanitary wastewater has been discharged to infiltration and lined evaporation ponds. Nonradioactive cooling-tower wastewater was discharged to radioactive-waste infiltration ponds from 1952 to 1964, to the Snake River Plain aquifer through a 1,267-ft-deep disposal well (TRA DISP, fig. 3) from 1964 until March 1982, and into two cold-waste infiltration ponds from 1982 to present.
In 1976, the DOE contractor at the RTC began a three-phase program to reduce radioactivity in wastewater. The first phase ran from 1976 to 1980 and the second phase ran from 1981 to 1987. The contractor finished the final phase of the program in 1993. During 1977–78, the average number of Curies (Ci) discharged to the RTC radioactive-waste infiltration ponds was about 1,300 Curies per year (Ci/yr) (Barraclough and others, 1981); during 1992–95, about 430 Ci of tritium was discharged to the RTC radioactive-waste infiltration ponds. During 1992–95, tritium accounted for about 96 percent of radioactivity in wastewater discharged at the RTC (Bartholomay and others, 1997). About 2,390 Ci of chromium-51 was in wastewater discharged to the radioactive-waste infiltration and lined evaporation ponds during 1979–98. No data are available for chromium-51 discharged during 1999–2005. The average disposal rate of chromium-51 during 1979–81 was 766 Ci/yr (Pittman and others, 1988, p. 35). During 1986–88, 25.7 Ci of chromium-51 was discharged, an average of 8.6 Ci/yr (Cecil and others, 1991, p. 35). During 1989–91, 11.6 Ci was discharged for an average of 3.9 Ci/yr (Tucker and Orr, 1998, p. 17). During 1992–95, 10 Ci was discharged, an average of 2.5 Ci/yr (Bartholomay, 1998, p. 16). During 1996–98, 6.2 Ci was discharged, an average of 2.1 Ci/yr (Bartholomay and Tucker, 2000).
Because of this waste reduction program, by 1993, the volume of radioactive wastewater and total Curies of radioactivity discharged at the RTC was reduced to a volume that could be disposed in two lined evaporation ponds, replacing the radioactive-waste infiltration ponds. The evaporation ponds may prevent radioactive wastewater from entering the aquifer.
The average annual discharge to the radioactive-waste infiltration and evaporation ponds (fig. 3) was about 116 Mgal during 1960–98. During 2000–2001, effluent waste disposal to the evaporation ponds averaged about 5 Mgal (Richard Kauffman, U.S. Department of Energy, written commun., 2005), which is less than the long-term average. The volume of wastewater and the amount of tritium discharged to the radioactive-waste and evaporation ponds during 1962–2005 are shown in figure 8.
During 1974–79, about 10 percent of radioactivity in wastewater discharged was attributed to tritium; most other radioactivity consisted of radionuclides with half-lives of about several weeks, as well as small amounts of strontium-90, cesium-137, and cobalt-60 (Barraclough and others, 1981). In 1980, about 50 percent of radioactivity was attributed to tritium, and during 1981–85, about 90 percent was attributed to tritium (Pittman and others, 1988, p. 22). From 1986–2000, about 97 percent of radioactivity in wastewater discharged at the RTC has been attributed to tritium (fig. 8). No tritium data are available for 2001–05.
A chemical-waste infiltration pond was used for disposal of chemical wastewater from an ion-exchange system at the RTC (fig. 3) from 1962 to 1999. The average annual discharge to this pond was about 17.5 Mgal during 1962–98 (Bartholomay and others, 2000). The average annual discharge for 1996–98 was 5.8 Mgal, 33 percent of the long-term average (Bartholomay and others, 2000). Sulfate and sodium hydrate were the predominant constituents in the chemical wastewater. The sodium hydrate consists of a 50 percent sodium hydroxide solution (Bartholomay and others, 2000). During 1996–98, average annual amounts of about 210,280 lb of sulfate and 98,800 lb of sodium hydrate were discharged to the chemical-waste infiltration pond. Additionally, about 11,100 lb of sodium ion was discharged in October 1996 (French and others, 1997a). Average annual concentrations of sulfate and sodium hydrate in the wastewater were about 4,300 and 2,000 mg/L, respectively (Bartholomay and others, 2000). In 1999, the chemical-waste infiltration pond was closed and covered with a protective cap (Stoller Corporation, 2002a).
The TRA disposal well, currently used as an observation well, was used from 1964 to March 1982 to inject nonradioactive wastewater from cooling-tower operations at the RTC into the Snake River Plain aquifer. Since March 1982, this wastewater has been discharged to two cold-waste infiltration ponds (fig. 3). The average annual discharge to the well and the infiltration ponds was about 226 Mgal during 1964–95 and about 181 Mgal during 1996–98 (Bartholomay and others, 2000). This wastewater contained an average annual amount of about 402,000 lb of sulfate and 94,000 lb of other chemicals during 1996–98 (Bartholomay and others, 2000).
Sewage effluent discharged to sanitary-waste ponds (fig. 3) at the RTC was about 28 Mgal/yr during 1996–98 (Bartholomay and others, 2000), about 17 Mgal in 2000, and about 52 Mgal in 2001 (Richard Kauffman, U.S. Department of Energy, written commun., 2005). In 1989, the sewage effluent contained about 1,070 lb of chloride and 1,550 lb of hypochlorite. Chloride and hypochlorite were not reported as part of the sewage effluent after February 1990 (Bartholomay and others, 2000).
From 1952 to February 1984, the INTEC discharged most low-level radioactive, chemical, and sanitary wastewater into the Snake River Plain aquifer through a 600-ft-deep disposal well (fig. 6). The average annual discharge of wastewater to the well was about 363 Mgal (Pittman and others, 1988, p. 24). Two percolation ponds (also called infiltration ponds) were used for wastewater disposal during 1984 through August 25, 2002 (fig. 3). The first pond was completed in February 1984 and the second pond was completed in October 1985. The annual discharge to the disposal well and ponds ranged from 260 Mgal in 1963 to 665 Mgal in 1993. Discharge to the ponds during 2001 was about 544 Mgal (Stoller Corporation, 2002c, p 5-9); data for 1999 and 2000 are not available, however, an estimated 1–2 Mgal/d of wastewater was generated (Stoller Corporation, 2003). About 402 Mgal were discharged to the existing percolation ponds during 2002. The volume of wastewater discharged to the disposal well and existing percolation ponds during 1962–98 and 2001 is shown in figure 9. No data were available for volume of wastewater discharged during 1999–2000 or 2002–05. On August 26, 2002, the existing percolation ponds were taken out of service and wastewater was discharged to the new percolation ponds. The new percolation ponds were designed to be a rapid infiltration system, and each pond can accommodate up to 3 Mgal/d of continuous discharge (Stoller Corporation, 2004)
Most radioactivity in wastewater discharged to the percolation ponds at the INTEC was attributed to tritium. Tritium accounted for most of the radioactivity in wastewater discharged at the INTEC since 1970 (fig. 9). During 1986–88, 556 Ci of tritium was discharged at the INTEC; the average annual amount discharged was 185 Ci (Orr and Cecil, 1991, p. 20). During 1990–91, 2.7 Ci of tritium was discharged; during 1992 and 1995 about 0.3 Ci was discharged; no tritium was discharged during 1989, 1993, 1994, and 1996–99; and 0.03 Ci was discharged during 2000 (fig. 9). No data were available for tritium discharged during 2001–05.
During 1996–98, chloride, fluoride, nitrate, sodium, and sulfate were the predominant chemical constituents in wastewater discharged to the INTEC percolation ponds. During this period, average annual amounts of about 1,166,000 lb of chloride; 1,070 lb of fluoride; 86,700 lb of nitrate; 708,000 lb of sodium, and 146,000 lb of sulfate were in wastewater discharged at the INTEC. Data have not been compiled for predominant constituents and amounts in wastewater discharged during 1999–2005.
About 18,100 Ci of strontium-90 and 19,100 Ci of cesium-137 have been released to soil at the INTEC Tank Farm (Cahn and others, 2006). In 1972, during a failed transfer of waste between two underground storage tanks, about 18,600 gal of sodium-bearing waste was leaked at an INTEC Tank Farm site (fig. 7). This accounts for about 88 percent (approximately 15,900 Ci) of the source of strontium-90 and cesium-137 to groundwater at the Tank Farm. Three other locations at the Tank Farm are the source of the remaining 12 percent of strontium-90 (Cahn and others, 2006).
Solid and liquid radioactive and chemical wastes have been buried in trenches and pits at the Subsurface Disposal Area (SDA) at the RWMC (fig. 3) since 1952. These include transuranic wastes, other radiochemical and inorganic chemical constituents, and organic compounds. The transuranic wastes were buried in trenches until 1970, and stored above ground at the RWMC after 1970. Only low-level mixed waste has been buried at the RWMC since 1970. Before 1970, little or no sediment was retained between the excavation bottoms and the underlying basalt. Since 1970, a layer of sediment has been retained in excavations to inhibit downward migration of waste constituents.
About 17,100 Ci of plutonium-238, 64,900 Ci of plutonium-239, 17,100 Ci of plutonium-240, and 183,000 Ci of americium-241 were buried in the SDA during 1952–99 (Holdren and others, 2002, table 4-1). An estimated 88,400 gal of organic waste was buried before 1970 (Mann and Knobel, 1987, p. 1). These buried wastes included about 24,400 gal of carbon tetrachloride; 39,000 gal of lubricating oil; and about 25,000 gal of other organic compounds, including trichloroethane, trichloroethylene, perchloroethylene, toluene, and benzene.
From 1953 to 1972, low-level radioactive, chemical, and sanitary wastewater was discharged at TAN (fig. 1) into the Snake River Plain aquifer through a 310-ft-deep disposal well (TAN Disposal Well, fig. 5). In 1972, the disposal well was replaced by a 35-acre infiltration pond. No records are available that indicate the amount of radioactivity in wastewater discharged at TAN before 1959. During 1959–93, about 61 Ci of radioactivity in wastewater were discharged to the disposal well and infiltration pond. Of this amount, about 20 Ci were discharged to the disposal well in 1968 and 1969 in response to problems with an evaporator used to reduce the volume of liquid waste (Energy Research and Development Administration, 1977, p. II–110, II–111). No radioactive wastewater has been discharged since 1993 (Bartholomay and others, 2000).
An average of about 6.6 Mgal/yr of chemical wastewater was discharged to the infiltration pond at the Technical Support Facility during 1996–98 (Bartholomay and others, 2000). The predominant constituents were chloride and sodium. Average annual amounts of 6,900 lb of chloride and 4,500 lb of sodium were discharged. The average annual amount of all other chemical constituents in the wastewater was about 760 lb (Bartholomay and others, 2000). During 1999–2001, about 28.5 Mgal of wastewater was discharged (Teresa Meachum, CH2M-WG Idaho, LLC, written commun., 2005). Based on 2001 records, an average of 838,000 gal/mo (10 Mgal/yr) of wastewater is discharged to the infiltration pond (U.S. Department of Energy, 2002). No data were available for total amounts of individual constituents disposed in wastewater for 1999–2005.
About 65 Ci of radioactivity in about 1,500 Mgal of wastewater were discharged to the sewage-plant tile drain field at the CFA (fig. 1) during 1952–93. Most radioactive wastes discharged to this drain field were from aquifer water pumped from well CFA 1 (fig. 5), which obtains water from within the INTEC contaminant plume in the Snake River Plain aquifer. Most radioactivity in wastewater discharged at the CFA was attributed to tritium. During 1993–98, no radioactivity was recorded in wastewater discharged at the CFA (Bartholomay and others, 2000). No data were available for radioactivity in wastewater at the CFA for 1999–2005.
An average of about 42.1 Mgal/yr of wastewater was discharged to a pond at CFA and a computerized central pivot system discharged about 13.6 Mgal/yr to native desert rangeland during 1999–2001 (Stoller Corporation, 2002c; Teresa Meachum, CH2M-WG Idaho, LLC, written commun., 2005). Chloride and sodium were the predominant chemical constituents in wastewater during 1996–98. Average annual amounts of about 7,800 lb of chloride and 5,300 lb of sodium were discharged during 1996–98. The average annual amount of all other constituents in the wastewater was about 6,300 lb; about 5,400 lb was from disposal of janitorial supplies (Bartholomay and others, 2000). No data were available for total amounts of individual constituents disposed in wastewater for 1999–2005.
U.S. Department of the Interior | U.S. Geological Survey
URL: http://pubs.usgs.gov/sir/2008/5089
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