Depot spokesman Bruce Henrickson says the last shipment of eight-inch projectiles will be made from storage to the plant on Tuesday.
If all goes well, disposal should begin Wednesday or Thursday.
The facility has destroyed more than 13,000 of these projectiles already.
After the last one is destroyed, the facility will start processing the final sarin gas-related munitions in its stockpile, which will take until July.
Once the munitions work is complete, the plant will start focusing on its rocket campaign, which should run until early 2009.
When the rocket project is finished, the mustard gas will be the depot's final campaign.
Henrickson says the disposal work will likely be completed in 2012.