Status report on remedial investigation of the 300 Area process ponds

Dennison, D.I.; Sherwood, D.R.; Young, John S.

doi:10.2172/5719703

Cited by 13 publications

(11 citation statements)

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“…The used degreasing solvents most likely were disposed to the process sewer system, which discharged to the North and South process ponds until 1975. Initial remedial investigation activities at the two process ponds did not reveal evidence for VOC contamination in sediment samples from the ponds (however, they did detect polychlorinated biphenyls), but the presence in groundwater of TCE and PCE was noted (Dennison et al 1989). …”

Section: Potential Sources For Tce Pce and Dce Observed In Drillingmentioning

confidence: 95%

Volatile Organic Compound Investigation Results, 300 Area, Hanford Site, Washington

Peterson¹,

Williams²,

Smith³

2008

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Executive SummaryUnexpectedly high concentrations of volatile organic compounds (VOCs) were discovered while drilling in the unconfined aquifer beneath the 300 Area of the Hanford Site during 2006. The discovery involved an interval of sediment within the unconfined aquifer that is not routinely monitored by groundwater sampling. Although VOC contamination in the unconfined aquifer has been identified previously and monitored, the concentrations of newly discovered contamination are much higher, with some new results significantly above the drinking water standards. The primary contaminant is trichloroethene, with lesser amounts of tetrachloroethene. Both chemicals were used extensively as degreasing agents during the fuels fabrication process. A microbiological degradation product of these chemicals, cis-1,2-dichloroethene, also was detected.To further define the nature and extent of this contamination, additional characterization drilling was undertaken during 2007. Four locations were drilled to supplement the information obtained at four locations drilled during the earlier investigation in 2006. The results of the combined drilling indicate that the newly discovered contamination is limited to an interval within the Ringold Formation that contains relatively finer-grained sediment than is found in other portions of the unconfined aquifer. The lateral extent of this contamination appears to be the area immediately east and south of the former South Process Pond. Samples collected from the finer-grained sediment at locations along the shoreline confirm the presence of the contamination near the groundwater-river interface. Contamination was not detected in river water that flows over the area where the river channel potentially incises the finer-grained interval of aquifer sediment.The source for this contamination is not readily apparent. A search of historical documents and the Hanford Waste Information Data System did not provide definitive clues as to specific waste disposal operations or spills that might have resulted in groundwater contamination in this sediment, although several relatively small accidental releases of VOCs have occurred in the past in the northern portion of the 300 Area. It is likely that large quantities of degreasing solutions were disposed to the North and South process ponds during the 1950s and 1960s. The infiltration of these discharges through the vadose zone was probably sufficient to cause widespread contamination of the underlying aquifer, and to depths that included the finer-grained material where contamination currently remains because of the low permeability associated with this sediment. Evidence for the earlier widespread contamination in the upper portion of the unconfined aquifer has been removed because of rapid groundwater movement through the much more transmissive sediment. Investigations to date have revealed no evidence to suggest that a dense, nonaqueous phase liquid remains undetected in the subsurface.Potential pathways for contamination to migrate from thi...

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Section: Potential Sources For Tce Pce and Dce Observed In Drillingmentioning

confidence: 95%

Volatile Organic Compound Investigation Results, 300 Area, Hanford Site, Washington

Peterson¹,

Williams²,

Smith³

2008

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“…Limited records document that the pH of the 300 Area process pond water varied over large range during operation (pH 1 to 12) as a result of the nature of the waste and intentional manipulation by site personnel. Anecdotal remarks (Dennison et al 1989;DOE 1990) indicate that base (e.g., NaOH) was added to the pond water to neutralize acid and limit the migration of copper to the river that was evident as green-staining around shoreline seeps. Divalent copper (Cu 2+ ) and U(VI) (UO 2 2+ ) exhibit comparable and high mobility under acidic conditions.…”

Section: An Integrated Conceptual Modelmentioning

confidence: 99%

Uranium Geochemistry in Vadose Zone and Aquifer Sediments from the 300 Area Uranium Plume

Zachara¹,

Davis²,

Liu³

et al. 2005

135

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“…It was retired in 1974. A detailed description of waste discharge history, pond operations, and organic, inorganic, and radioactive contaminants found in this pond can be obtained from several previously published reports (Dennison et al 1989;Young et al 1990;Young and Fruchter 1991). An analysis of the pond sediments conducted in 1992 indicated that activities of 235 U and 238 U, and concentrations of Cr, Ni, Cu, Zn, Zr, Ag, and Sr were elevated above the background concentrations found in the uncontaminated sediments from the 300 Area (Serne et al 1992).…”

Section: Waste Disposal Sites and Sources Of Contaminationmentioning

confidence: 99%

Radionuclide Activities in Contaminated Soils: Effects of Sampling Bias on Remediation of Coarse-Grained Soils in Hanford Formation

Mattigod¹,

Martin²

2001

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Executive SummaryThe Remedial Action Sampling and Analysis Plan (RASAP) for the Hanford Site's 100 Area soils requires sampling and analyzing the soil material for contaminants of concern (COC). However, the RASAP does not include a protocol for analyzing only a fine-grained fraction (sand, silt, and clay) and then relating the measured COC activities and concentrations in this fraction to those in the predominantly coarse-grained (gravel) whole soils in the 100 Area. Selectively sampling only the finer fractions of a coarse-grained soil would introduce a systematic bias that results in consistently overestimating the actual activities and concentrations of COC in whole soil. Such sampling bias, if uncorrected, would result in over-remediation (remediating below the remedial action goal [RAG] levels) of these soils. Therefore, we conducted a study to assess the scope of this problem by analyzing available particle size-COC activity and concentration data for 100 and 300 Area soils, and determined the effects of sampling bias. Our recommendations include sampling protocols and methods to determine the COC activities and concentrations of the whole soil based on the measurements conducted on a finer size fraction of the whole soil.The important findings of our investigations are that 1. In gravelly soils (100 and 300 Areas), the activity and concentration of any COC per unit mass in any finer fractional soil material was consistently biased higher than those of the same COC in the whole soil (all grain sizes sampled). The degree of sampling bias for each COC could be quantified as a sampling bias factor (SBF) that relates the activity and concentration in any finer size fraction of a soil to that in the whole soil.2 The SBF for any COC in a soil increases with decreasing particle size sampled. SBFs for different COC in a soil can vary significantly (up to an order of magnitude) depending on their chemical properties and affinity for specific mineral surfaces.3. SBF for a single COC in soil samples obtained from different locations from the same waste site can be significantly different (two to three times higher than the lowest value), reflecting spatial variability engendered by the source, the type, and the distribution of contamination.4. The SBF for a COC in soils from different waste sites were different, and these values were affected by the soil texture, the degree, the source, and the distribution of contamination.5. Waste site soils would be over-remediated (remediated below remedial action goal values) without SBF corrections. SBF corrections could be made by using corrected remedial action levels (CRAL) computed from RAG and SBF (for selected particle-size finer) for each COC.6. The soils in the vicinity of the 116-C-1 waste trench would be over-remediated (excavation of ~57% to 280% of excess soil volume) without appropriate SBF corrections for contaminant radionuclides 60 Co and 152 Eu.iv Based on our analyses and conclusions, we recommend that 1. A sampling grid should be established (using a geostat...

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Status report on remedial investigation of the 300 Area process ponds

Cited by 13 publications

References 0 publications

Volatile Organic Compound Investigation Results, 300 Area, Hanford Site, Washington

Volatile Organic Compound Investigation Results, 300 Area, Hanford Site, Washington

Uranium Geochemistry in Vadose Zone and Aquifer Sediments from the 300 Area Uranium Plume

Radionuclide Activities in Contaminated Soils: Effects of Sampling Bias on Remediation of Coarse-Grained Soils in Hanford Formation

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