Haystack_SDV___NN_PA_Report_0002.pdf

This is a Preliminary Assessment/Site Assessment Report addressing toxaphene contamination at 24 sheep dip vat (SDV) sites on Navajo Nation lands. The Navajo Superfund Program prepared the report in June 1999 for submission to USEPA Region IX, covering sites located in Arizona and New Mexico across 23 Navajo Nation Chapters.

The report documents a fifty-year history of toxaphene and lindane pesticide use at approximately 250 SDV sites operated by the Navajo Nation and Bureau of Indian Affairs from the 1930s through the late 1980s. After livestock dipping operations, spent pesticide solutions were improperly disposed of in unlined pits, trenches, and intermittent streams, resulting in soil contamination. USEPA banned toxaphene use in 1983. The April 1998 sampling activities by the Navajo Superfund Program at 24 SDV sites using Enzyme Immunoassay field test kits identified eight sites with toxaphene concentrations at or above the 40 ppm action level established by ATSDR (Agency for Toxic Substances and Disease Registry). USEPA laboratory confirmation testing showed soil samples from pesticide disposal locations, post-exit corrals, and disposal trenches ranging from 2.3 to 430 ppm toxaphene, with background samples at 0.5 to 20 ppm, confirming contamination at least three times above baseline. The report identifies threats to public health including potential contamination of drinking water supplies, high surface contamination susceptible to wind and rain migration, and proximity of sites to Chapter areas serving elderly and children populations. ATSDR health consultations are scheduled for July 1999, and bioremediation has been identified as a feasible cleanup approach targeting 25 ppm concentration levels.