nan ~ 408 RADIOLOGICAL CLEANUP OF ENEWETAK ATOLL be monitored and retrieved if a means of permanent disposa| Was perfected. CRATER CONTAINMENT DESIGN After much consideration, the Director, Defense Nuclear Agency (DNA)decidedin early 1975 that the only generally acceptable method for disposing of contaminated debris and soil from the Enewetak Cleanup Project was by mixing it with cement and placing it in recoverable Storage in Lacrosse and, if necessary, Cactus craters. Events leading to this decision are described in Chapter 2. One of the key factors in the decision wasa feasibility study prepared by the Pacific Ocean Division (POD) ofthe Corps of Engineers in March 1975. The study considered several options for crater containment, including: precast soil-cement blocks; lining and dewatering the craters and placing soil-cementslurry in them; or Pumping the slurry through pipe to the bottom of the crater, keeping the discharge end of the pipe at least | foot beneath the top of the previously poured slurry to form a monolithic mass. The last option, called the ‘“‘tremie” method, was recommended by POD not only because it was the fastest and least expensive, but because the other methods would achieve no significantly higher degree of protection. Properly accomplished, the tremie method would stabilize and fix the contaminated material in place as well as the other methods.8.9 In August 1976, once funds had been approved for the project, DNA requested that POD develop a design for crater containment using the tremie method.!9 The initial design was developed based on Field Command’s ConceptPlan I-76 (CONPLAN1-76) and oncriteria provided by engineers from Field Command’s Albuquerque and Honoluluofficesin a series of conferences with POD.!1.!2.13 The design was revised based on subsequent conferences with representatives from Field Command and the Military Service elements.!4 Development of the design was complicated by several factors. In the EIS, it was estimated that Case 3 cleanup would require containment of 79,000 cubic yards of soil, to bring the plutonium concentrations over 400 pCi/g to below 40 pCi/g on Aomon, Lujor and Runit, and 7,262 cubic yards of contaminated debris. The Field Command CONPLAN1-76 estimate for soil over 40 pCi/g, including Enjebi, was 125,000 cubic yards. Field Command asked POD to develop a design to contain up to 200,000 cubic yards as a worst case and to minimize costs by using only one of the two craters.!5 This required a decision on which crater to use.