Washington River Protection Solutions (WRPS) is the Tank Operating Contractor (TOC) for the U.S. Department of Energy Hanford site. The Hanford Site stores mixed radioactive and chemically hazardous waste in large underground tanks. Hanford has 149 older Single Shell Tanks (SST) and 27 newer double-shell tanks (DST) grouped together in tank farms. The SSTs have capacities from 500,000 to 1,000,000 gallons; and measure up to 75’ in diameter and 45’ in depth. Multiple openings in the dome of the tanks (risers) provide access into the tank for operational activities.