Perchlorate Source Attribution Study in Zones 1-4 of the Stringfellow Superfund Site, Jurupa Valley, Riverside County, California

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Between 1956 and 1972, the Stringfellow Hazardous Waste Site, Riverside County, Calif., discharged approximately 34 million gallons of industrial wastes to unlined surface impoundments located at the head of Pyrite Canyon. Contaminants from the site have been detected as far as 4 miles downgradient near the Santa Ana River. Perchlorate in excess of the California Maximum Contaminant Level of 6 micrograms per liter has been detected within the area of contamination. The areal extent of perchlorate contamination from the site, and other sources of the perchlorate near the margin of the contaminant plume, are not precisely known.

Map of the Stringfellow Superfund Site.

Map of the Stringfellow Superfund Site

The purpose of this study is to distinguish groundwater and associated solutes, especially perchlorate, that may have originated from the Stringfellow Hazardous Waste Site within Pyrite Canyon, from other potential sources farther downgradient.

Scope of the study includes a multiple-tracer approach that will be used to evaluate the source, movement, and age of water, along with the chemical processes that affect selected solutes, such as nitrate. The multiple-tracer approach includes the use of: (1) isotopes (δ18O and δD of water) and dissolved gasses (N2, and the noble gases helium, neon, argon, krypton, and xenon) to determine the source and hydrologic history of water, (2) age-dating parameters (tritium, helium-3, and carbon-14) to determine time-since recharge of water along selected groundwater flowpaths, and (3) isotopes of nitrate and sulfate to determine differences in the source and chemical history of these solutes, that may be associated with releases at the Hazardous Waste Site or from other sources in the study area. Isotopic and other data will be interpreted with hydrologic and chemical data, including selected chemical tracers and indicators of the redox status within water (dissolved oxygen, nitrate, iron, and sulfide). The work will be coordinated with collection, analyses, and interpretation of chlorine and oxygen isotopic composition of perchlorate to be done by Dr. Neil Sturchio, University of Delaware.