21 The pumping recovery tests, which involved pumping the boreholes completely dry and then observing the rate of water level rise, were conducted in the tremie material. These tests showed a very rapid recovery in the water levels; in one case the water level rose 2 feet in 5 minutes. Furthermore, water levels within the tremie concrete corresponded very closely to sea: level and lagged only about 1/2 ‘hour behind outside tidal fluctuations. Thus, it appears that although the permeability of the soil-cement mixture is quite low, the permeability of the tremie concrete is much higher. Purthermore, in the tremie region there was relatively free communication with the ocean, perhaps mainly along channels provided by the oversize debris. The soil-cement mixture was a moist, dense material that crumbled in the hand and the tremie concrete, a dense, partially cemented material. The whole of the crater contents, however, was rather impermeable to water except where there was channeling. In sumnary, the cores showed that there are zones of incompletely cemented tremie concrete. This segregation of the concrete most likely resulted because the tremie pipe was not always kept below the surface ef the slurry, probably due to movements of the barge carrying the injection equipment or failure to use a plug when each pumping sequence was started. The soil-cement above the water level aiso did not achieve the concrete-like character that was anticipated, possibly because of bacterial effects of organic material which prevented proper wn, hardening of the concrete at the level of cement content used. Nevertheless, we believe that the keywall and concrete dome are satisfactory for all likely situations that will occur. 4.3 Radioactive Contents Samples taken from the cores and water samples from the holes were. analyzed at the Lawrence Livermore Laboratory. Water samples also were taken from two monitoring wells sunk outside the dome area, on the lagoon side, in positions calculated to intersect water passing through the crater and into the lagoon. The wells were fitted with unscreened slotted polyvinylchloride pipe for use in future monitoring. The results of these analyses have been given by Robison and Noshkin (1981). ‘To summarize the data here, mean values have been _Calcplated, omitting samples taken in the fallback zone. Results are given in pCi/g and the range gives the high and low values for the set of samples. Strontium and Pu were analyzed using wet chemistry methods and the others, using gamma ray spectrometry. . * ° 339 T290py Aeian -~—! tJ cD C™ **sr **7es CF) . Radionuclide Mean Concentration | | Range 18.6 (46 - 1.6 2.8 6.3 = 0.20 20.6 8.7 ' $2- 5.5 27 = 0.24 ”