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• D"nom the annual inspection of the dam, cracks on the crost and downstcearn slope were again observe3 Appearance, chazacter and location of ctackmg, however were distincfiy different than cracks observed two Years prior. The main crack, shown on Figure 1, began near the k& abrtment on the crest and traversed the downstream slope diagonally toward the outlet for a distance of aboat'IO feet The crack was about 2S inches wide and probed to a depth of 2 feet A longitudinal crack traversed the crest between the abutment and the fast piezometer,, P-1. Tlris crack showed Iitde sepazafion, but was probed to a depth of 3 fcet See Fig~e 1. The reservoir was again restricted to a Ievel 10 feet below spffi until questions were answered reganling the cause of cracking and the integrity of the dam was evaluated. Inspection of fire solace geology revealed that a nnssive landslide fo>ms [he stnrctine of the le$ abutment Because the abutment centact was iadistmom~;chahle, it was difficult to determine if the cracks were on the embankment or the abutrnent Topograplticafly, the slide mass extends, vertically, about 400 feet above the dam site and i500 feet across az the widest point A ridge along the east botmdary of the s&de, Heady pamRet end m line with the ass ofthe dam, begins az the left abutment and ends az the head of the slide. The ridge also forms the west boundary of a slide which encompasses the spiIlway entrance and rim of the reservoir upstream of the left abetment abort 100 feet. The inves4gatioa concluded the observed cracks were a malt of shear along the perimeter of the landslides. Furthermore, slide debris was marginally stable and would likely continue m move as a result of changes in pore pressure within the slide mass. 1988 The cracks wore backfilled with impervious clay ma6erial and survey points established to monitor further movements of the dam and the left abutment slide. Embankment piewmcaers and drain flow measurements showed no anomalies and consistent trends with previous records. Inspections revealed no additional caacking as reopeffig of old cracks. As a result of the dry condition of the left absent, the reservorz was allowed m fill within 2 feet of spill. • Performance of the dam was Jcrdged aa:eptable for the relatively short period of time the reservon- was above rho restriction and no rmusual behavior was observed Piezometer levels and drain onffiow wen: sinn7ar m past records far couespo~ing reservoir levels. A primary question, however remained tmanswered_ what, if any, influence does leakage from the reservoir through the abntmeM or foundation have a~n the stab8ity of the slide mass? 1989 Less thaw average snow Back aaa dry coalitions were favorable in aIIow temporary sorage above the restiction. The amual inspection found conditions wen: unchanged from previous observations. Controlled filling ofthe reservoir began in May with provisions m inspect and mm~itor the dam 3 times per week. Because of the rmaaaauy dry weafirer irrigation demands resulted m the reservoir being drawn down to the restriction by 7uly 1". No usual performance was observed and monimring results were simr7ar m the past records for the period of t~ the reservoir operated above the restriction. 1990 The preceding wnde~'s sooty pack was above average, but the resulting runoff peak flow was managed by fire outlet without exceeding the restriction. By mid-hme the snowpack in the general area bad melted and the ground surfaces were sufficiently dry to allow conditional storage above the resmction Monitomig and inspection were performed az least twice per week as a condition for storing water above the resmcctian. The reservos was drawn down m the reshiction by August 1'r. The dam continued m perform without signs of cracks or increased leakage daring the time the reservoir was above the nspecton..