Facts on DIMP and the Rocky Mountain Arsenal • DIMP is an abbreviation for the chemical diisopropyl methylphosphonate and is a by-product of the Sarin nerve agent (also called GB) manufacturing process. Sarin was produced at Rocky Mountain Arsenal as a deterrent during World War II and the Cold War era. • The DIMP generated at the Rocky Mountain Arsenal was discharged into unlined basins, using accepted disposal practices of the time. This practice resulted in the contamination of groundwater both on and off the Arsenal. • DIMP is not a nerve agent and does not have the toxicity of a nerve agent, nor is it known to have any cancer-causing effects in humans. • DIMP is a colorless, odorless and tasteless liquid, which is very soluble and chemically stable in water. • DIMP has a low vaporization potential, meaning vapors are not readily released from DIMP dissolved in groundwater. • The state ground and surface water standard for DIMP is 8 parts per billion (ppb). And, the Environmental Protection Agency’s (EPA) National Health Advisory is 600 ppb. One ppb is equivalent to ½ tsp. in an Olympic-sized swimming pool • The Colorado Department of Public Health and Environment prepared a risk assessment in 2000 to evaluate the public health significance of consuming vegetables and fruits irrigated with DIMP-contaminated groundwater. The assessment concluded that the risk associated with the exposure to DIMP at or near the state groundwater standard is unlikely to be a public health concern. • The Arsenal treats DIMP to or below the state’s protective groundwater standard, typically in the less than 1 ppb range, at the two boundary and one off-site groundwater treatment systems. • DIMP is treated at the RMA boundary by a filtration system, which uses activated carbon to capture DIMP and other organic contaminants. • Arsenal water treatment systems have been operating since 1977 and have proven effective in treating contaminated groundwater to below state and federal requirements, leading to a significant reduction in the area affected by off-site groundwater contamination. • Residents living in areas north of the Arsenal are connected to the South Adams County Water and Sanitation District (SACWSD) water supply for all drinking water and household uses, thereby greatly reducing any direct exposure pathways or risk. For questions about water quality, please call SACWSD at 720-206-0563 and for questions about water resources, please call SACWSD at 720-206-0567. • Tri-County Health Department (TCHD) has monitored the DIMP groundwater contamination to the north of the Arsenal since 1974. Data gathered from these tests are available to the public. TCHD representatives can be contacted through their 24-hour information line at 303-286-8032 • Currently, the Arsenal is undergoing a safe and extensive environmental cleanup of the site, which is anticipated to be complete in 2011. As the remediation progresses, the site will continue its transition to one of the nation’s largest, urban wildlife refuges. As of 2005, nearly one-third of the site’s original 27-square miles already has been incorporated into the National Wildlife Refuge System. • Residents with any questions, comments or concerns are encouraged to contact the Arsenal’s Community Information Line at 303-289-0136. • Additional suggested contact information:
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