Development of a technically consistent,qualified lithostrgraphic data base for the Yucca Mountain project

摘要

Studies of Yucca Mountain,Nevada,as a potential geologic nuclear-waste repository began in the late 1970s and continued to 1988 when the U.S.Nuclear Regulatory Commission determined that the quality assurance (QA) programs needed to be upgraded and restructured.A newly restructured QA program was accepted in 1989,but many study activities did not resume until new procedures were in place,until the early 1990s.These pre- and post-1989 generations of QA programs have resulted in a highly convoluted assignment of qualified (Q)-status for much of the borehole data.In the simplest case,data from boreholes drilled before 1989 had been assigned Q status.This pre- and post- 1989 distinction in Q status of borehole data has meant that lithostratigraphic descriptions and contacts from the pre-1989 boreholes have bene classed as non-Q,and any reports and ocmputer models~1 that used these data also carried the non-Q status (R.W.Clayton,W.P.Zelinski,and C.A.Rautman,TRW Environmental Safety Systems,Inc.,written commun.,1997).The Q-status of dat ahas limited the amount of lithostratigraphic work done on the pre-1989 boreholes because of the emphasis to produce Q-status data.A parallel and critical concern that arises from such a long history of data collection is the consistent identification of lithostratigraphic units.In the spring of 1996,an intensive effort began to re-examine 11 lithostratigraphic contacts in boreholes.This work was expanded in 1997 to include as many as 50 lithostratigraphic contacts in 80 boreholes.All this work has been done under the post-1989 QA program and emphasizes technically consistent contacts and the Q-status of each contact rather simple assignment by borehole.