article_snippet: Technicians will take four years to eliminate almost 800,000 artillery shells containing mustard agent .
article_snippet: It will take four years to destroy the Pueblo stockpile.
article_snippet: a highly automated $4.5 billion plant built at the depot isn't expected to begin work until December or January.
article_snippet: Design and construction have taken years, and final testing and training are underway.
highlights_snippet: Almost 800,000 artillery shells are being destroyed over the next four years .
  