[CPEO-MEF] Last night, Colorado's Water Quality Control Commission, by a vote o

[jeff.edson@state.co.us]

Last night, Colorado's Water Quality Control Commission, by a vote of
4-3 decided to retain the current ground water and surface water
standard of 8 parts per billion for di isopropylmethylphosphonate
(DIMP).  See
http://www.rockymountainnews.com/drmn/local/article/0,1299,DRMN_15_1601760,00.html

DIMP is a by-product of the manufacture and detoxification of the nerve
agent commonly known as Sarin or GB (isopropyl methylfluorophosphonate).
It has a solubility in water of 1500 mg/1, and has a half-life in water
of 530 years. 

The United States Army manufactured GB at RMA from 1953 through 1957. 
The Army considered batches of GB with levels of DIMP greater than 3% to
be unacceptable for use as nerve agent. The unacceptable GB was
neutralized and discharged to one of five unlined surface impoundments
for disposal. According to Army records, during this period
approximately 130,000 pounds (60,000 kg) of DIMP were generated and
disposed of on RMA. Contaminants, including DIMP, disposed of in the
five surface impoundments percolated through the bottom of the
impoundments and contaminated ground water below the basins and as far
as 7 miles downgradient of the RMA disposal basins.    

The Army contended that the community as a whole would benefit from the
adoption of a 400 parts per billion water quality standard because it
was based on best available science.  
 

Jeff Edson
Manager, Remediation and Restoration Unit
Federal Facilities Program
Hazardous Materials and Waste Management Division
Colorado Department of Public Health and Environment
4300 Cherry Creek Drive South
Denver, CO 80246-1530
(303) 692-3388 phone
(303) 691-7761 fax

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