This report provides the results of the semiannual post-closure inspections conducted at the closed Corrective Action Unit (CAU) sites located on the Tonopah Test Range (TTR), Nevada. This report covers calendar year 2006 and includes inspection and repair activities completed at the following nine CAUs: CAU 400: Bomblet Pit and Five Points Landfill (TTR); CAU 404: Roller Coaster Lagoons and Trench (TTR); CAU 407: Roller Coaster RadSafe Area (TTR); CAU 423: Area 3 Underground Discharge Point, Building 0360 (TTR); CAU 424: Area 3 Landfill Complexes (TTR); CAU 426: Cactus Spring Waste Trenches (TTR); CAU 427: Area 3 Septic Waste Systems 2, 6 (TTR); CAU 453: Area 9 UXO Landfill (TTR); and CAU 487: Thunderwell Site (TTR). Post-closure inspections were conducted on May 9, 2006, May 31, 2006, and November 15, 2006. All inspections were conducted according to the post-closure plans in the approved Closure Reports. The post-closure inspection plan for each CAU is included in Attachment B, with the exception of CAU 400. CAU 400 does not require post-closure inspections, but inspections of the vegetation and fencing are conducted as a best management practice. The inspection checklists for each site inspection are included in Attachment C, the field notes are included in Attachment D, and the site photographs are included in Attachment E. Vegetation monitoring of CAU 400, CAU 404, CAU 407, and CAU 426 was performed in June 2006, and the vegetation monitoring report is included in Attachment F. Maintenance and/or repairs were performed at CAU 400, CAU 407, CAU 426, CAU 453, and CAU 487 in 2006. During the May inspection of CAU 400, it was identified that the east and west sections of chickenwire fencing beyond the standard fencing were damaged; they were repaired in June 2006. Also in June 2006, the southeast corner fence post and one warning sign at CAU 407 were reinforced and reattached, the perimeter fencing adjacent to the gate at CAU 426 was tightened, and large animal burrows observed at CAU 453 were backfilled. Cracking observed in three monuments at CAU 487 was repaired using sealant during the May 9, 2006, inspection. At this time, the TTR post-closure site inspections should continue as scheduled. Any potential problem areas previously identified (e.g., areas of erosion, subsidence) should be monitored closely, and periodic vegetation surveys of the vegetated covers should continue.