Don has supplied some very interesting links Forum Lurker - you really should read them:

What Dugway does in relation to CB weapons:

1. The mission of Dugway is to test U.S. and Allied biological & chemical defense systems; perform Nuclear Biological Chemical survivable testing of defense material; provide support to chemical and biological weapons conventions; and Operate and maintain an installation to support test mission.

2. Today DPG continues its role in the testing of chemical agents, pathogens, and toxins, now conducted in sealed containment chambers (rather than open air testing as in the past).

3.   The Department of Defense has designated U.S. Army Dugway Proving Ground (DPG) as the primary chemical and biological defense testing center under the Reliance Program.

4.   Testers here determine the reliability and survivability of all types of military equipment in a chemical or biological environment. The chemical laboratory, permitted storage area, and many test related activities are operated under contract.

5.   The Reginald Kendall Combined Chemical Test Facility (CCTF) is a state-of-the-art 48,000 square foot chemical laboratory facility designed to support testing of chemical warfare defensive equipment. Specific areas of the mission include evaluation of chemical agent detectors, testing of personnel and collective protective equipment (e.g., masks, clothing, shelters, etc.), testing of decontaminants, evaluation of military equipment for NBC survivability, analysis of waste and environmental samples, and safety air monitoring.

NOTE: In the above, or alternatively, read in the text contained in the links as supplied by Don - you will not find any reference to the testing of any CB weapons systems or munitions. Which is not really all that surprising since:

"In 1993, the United States signed the UN-sponsored Chemical Weapons Convention. In October 1996, the 65th nation ratified the convention making the treaty effective on April 29, 1997. Through ratification, the United States agreed to dispose of its unitary chemical weapons stockpile, binary chemical weapons, recovered chemical weapons, and former chemical weapon production facilities by April 29, 2007, and miscellaneous chemical warfare materiel by April 29, 2002."

Yes you do have stockpiles of CB Agents and some obsolete munitions and at present they are being stored for controlled and audited destruction.