Hanford Site National Environmental Policy Act (NEPA) - Pacific ...

Contaminant, Units
Table 4.4-1. Regulatory Drinking Water Standards for Groundwater
Drinking
Water
Standard
Contaminant, Units
Drinking
Water
Standard
arsenic (filtered), µg/L 10 gross beta, pCi/L 50
cadmium (filtered), µg/L 5 iodine-129, pCi/L 1
carbon tetrachloride, µg/L 5 nickel (filtered), µg/L 100
carbon-14, pCi/L 2,000 nitrate, mg/L 45
cesium-137, pCi/L 200 nitrite, mg/L 3.3
chloroform, µg/L 100 plutonium-239/240, pCi/L not applicable
chromium (dissolved), µg/L 100 strontium-90, pCi/L 8
cis-1,2-dichloroethene, µg/L 70 technetium-99, pCi/L 900
cobalt-60, pCi/L 100 trichloroethene, µg/L 5
cyanide, µg/L 200 tritium, pCi/L 20,000
fluoride, mg/L 4 uranium, µg/L 30
gross alpha, pCi/L 15
The highest strontium-90 concentration detected in riverbank springs during 2005 occurred at the
100-K Area (2.7 ± 0.41 pCi/L [0.10 ± 0.015 Bq/L]). This value was 34 percent of the ambient
surface-water quality criterion of 8 pCi/L (0.30 Bq/L). Samples from a spring at the 100-N Area have
historically had the highest strontium-90 concentrations. However, because of decreased groundwater
elevations, no flow has been observed at this spring since 1997 (Poston et al. 2006). Tritium
concentrations in riverbank springs varied widely with location. The highest tritium concentration
detected in riverbank springs during 2005 was 39,000 ± 2,800 pCi/L [1,400 ± 100 Bq/L]) at the
Hanford townsite (Poston et al. 2006). During 2000 to 2004 the highest iodine-129 concentration of
0.25 pCi/L (0.0093 Bq/L) was found in a Hanford townsite spring. Iodine-129 results were not yet
available for 2005 (Poston et al. 2006).
Non-radioactive contaminants of Hanford-origin continued to be detected in water from
shoreline springs entering the Columbia River along the Hanford Site during 2005. Metals and
anions (chloride, fluoride, nitrate, and sulfate) were detected in spring water. Concentrations of
volatile organic compounds were near or below their detection limits in all samples. Trichloroethene
was detected (1.4 µg/L) in one sample from the 300 Area and was the only analyte detected at all
shoreline spring sampling locations. Trichloroethene has been consistently detected at low
concentrations in 300 Area shoreline spring water (Poston et al. 2006).
4.4.1.6 Runoff and Net Infiltration
Total estimated precipitation over the Pasco Basin is about 9 x10 8 m 3 (3.2 x 10 10 ft 3 ) annually,
calculated by multiplying the average annual precipitation averaged over the Pasco Basin by the
4,900 km 2 (1,900 mi 2 ) basin area (DOE 1988). Precipitation varies both spatially and temporally with
higher amounts generally falling at higher elevations. Annual precipitation measured at the HMS has
varied from 7.6 cm (3 in.) to 31.3 cm (12.3 in.) since 1945. Most precipitation occurs during the late
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