Radioactive Soil Vacuuming for the Rocky Flats Environmental Technology Site.

Phase II
During September and October 2002, Concept Engineering Group Inc. performed a Phase II Soil Vacuum Demonstration for the Rocky Flats Environmental Technology Site. This site is a government-owned former nuclear weapons plant operated by Kaiser-Hill, LLC for the Department of Energy. The site is located about 15 miles northwest of Denver, Colorado. The site's mission today is to safely clean up and close down Rocky Flats after nearly 40 years of nuclear weapons production. The objective of the demonstration was to evaluate the capability of AIR-SPADE’s vacuum excavation technology and equipment to precisely cut and remove only the fine-grained portion of surface soil representative of the 903 Lip Area. The 903 Lip Area, an area of approximately 30 acres exceeding Tier II soil action levels, was created when contaminants from deteriorated drums in the 903 Storage Area were dispersed by the wind over soils to the east. The 903 Drum Storage Area was formerly used to store drums containing waste oils and solvents contaminated with plutonium and uranium. In the 903 Lip Area, Plutonium-239/240 activities in surface soils range from 6 to 940 pico-curries per gram. As the contamination is thought to be primarily attached to the fine-grained portion of the first two inches of the soil, the selective vacuuming capability offers a key benefit for remediation of the 903 Lip Area by greatly reducing the amount of material for disposal.

The demonstration was conducted on a 1/2 acre site at the Church Ranch adjacent to the site Visitor Center on Highway 93. The equipment used in the demonstration is a trailer mounted SAFEX® 60 unit and a specially configured collector to discharge via a rotary valve directly into a Lift Liner™ soft-sided waste container. The unique “flow-thru” design of the system eliminates a secondary source of dust emissions that would occur when the tank of a typical vacuum would be emptied when full into the disposal container. The equipment and method of soil vacuum remediation is patent pending under US Patent Application 10/680760.

The demonstration successfully met the requirements in the initial Work Plan. On average soil 1 1/2 inches deep was excavated per pass of the vacuum equipment at a coverage rate of 350 square feet per hour and an excavation rate of 0.26 bulk cubic feet per minute. Production efficiency reached 80% at the end of the demonstration with 100% of the excavated material being retained in Lift Liner™ soft-sided waste containers.

SAFEX^® 60 Skid Specifications

Soil Vacuum System Collector

Phase III
In 2003 Phase III of the RFETS Soil Vacuum Demonstration was conducted in the actual 903 Lip area. As shown below, a larger separator was constructed containing an increased filter area. This eliminated an elevated pressure drop noticed during Phase II testing. Because the soil at the actual site was contaminated, a HEPA final filter was added to the equipment skid. A new combined AIR-SPADE^® excavation tool / suction head assembly was fabricated. Over a several week time frame, RFETS personnel conducted the testing. Several items were found to be different than in Phase II and than originally thought. The degree of vegetation cover was much higher than the previous year requiring mechanical farm machinery to cut it. The contamination was found also to extend about 6 inches, about 3 times as deep, into the soil.

The 903 clean-up was completed in 2004 using conventional excavation methods. According to RFETS engineering, these methods were effective, but probably removed more dirt than necessary. An EM-50 test summary report is still to be issued, but has been set back due to higher priorities associated with the site closure.

Special collector filling Lift-LinerTM
Combined air-jet vacuum head
	SAFEX® Utility with special HEPA filter