Tetra Tech EC, Inc. Projects Department of Energy Hanford 100-N and 116-N Remediation Project, WA
Hanford 100-N and 116-N Remediation Project, WA

Tetra Tech was contracted to provide planning and engineering, mobilization, site preparation, surveying, demolition, excavation, size reduction, segregation, loading, staging and debris services within the Hanford site in Richland, WA. Water used to cool the 100-N reactor was discharged into a concrete trough-like distribution system where it traveled away from the reactor to a crib where it eventually absorbed into the soil through panels thus contaminating the soil with the highly radioactive waste. The crib covered 1.3 acres with the top and side panels made of reinforced concrete. Primary contaminants were cesium 137, cobalt 60, europium 154, plutonium 239 and 240, strontium 90 and tritium. Since the reactor had been shutdown only 13 years previously, the time for decay was short and the radiation levels were up to 50 times higher than experienced at other similar remediation project sites. The DOE noted that this was the most contaminated location within the Hanford site.


Tetra Tech performed demolition activities as well as the removal of contaminated soils and debris. We completed remediation activities associated with excavation, removal, stockpiling, blending, loading, and transportation of low and higher activity contaminated and uncontaminated soils, debris and materials associated with past waste disposal practices at the site. In addition, we provided engineering and technical services to prepare necessary submittals and drawings including as-builts, locations of existing / new access roads and active and inactive service utility lines and laydown areas. We minimized personnel exposure to contaminated materials by using numerous remote controlled procedures such as; remotely controlled concrete saws to cut concrete panels covering high radiation zones and loose radiological contamination, using “flying C clamps” to remove over 400 concrete panels and pumping 150 cubic yards of flowable grout into the N-3 Crib Distribution Trough to cover and shield radiation levels. In addition, we modified existing equipment and processes to minimize personnel exposure such as using a trackhoe to assist in taking samples or surveys and by mounting a cutting system to the trackhoe to reduce the amount of manual digging or pipe cutting.


Project Highlights

  • Successfully completed over 460 critical lifts
  • 1785 days without a lost time injury of accident
  • Removed, processed and transported 500,000 tons (29,100 containers) of soil and debris
  • Met customer-established ALARA goals, including a total exposure 40% less than expected
  • No environmental citations, notices of violation, PAAA reportable incidents or the like