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present Increased frequency of surveillance was the prescribed coMiogency m the monitoring plan for <br />~conholled filling of the reservoir. Daily inspections of the dam were pe~'a®ed along with measurements of <br />piezo and drain flows until the reservoir caald be lowered to fire restriction In addition, itrclinomehecs <br />were ~aimred weekly, instead ofphmned biweeklyreadings dining more conholkd conditions. <br />Inclinometer readings taken preceding Sprang runoff showed the slide had moved between O.IS and 0.25 inches <br />from the initial reading the previous Fall, Figure 2 shows a distinct zone of movement in the profile of <br />inclinometer INGl. The reservoir remain spffiing for Heady three weeks before the inflow receded. An <br />additional two weeks passed before the reservoir could be lowered to dre reshiction Slide movement <br />progressed to about 1.75 inches during the runoff period, b~rt the rate of movement decelerated after pi~^*^Pr°- <br />IeveLs in the Lmdslide began declirmrg. <br />Rate of movem~t became a principh fac6or in evaluating grogessive slide activity. Movement was occurring <br />at a depth conespond'aog m the upper shear zones identified in the bole boring of INGl. Initially; strain rate <br />was umgsmed for shear zone chain rehtticve to the feed position of the bottom of the inclinometer casing, but <br />results were gni6e erratic The randomness of results were dramatically reduced by calculating strain at the top <br />of the shear zone rehuive to the poini at the bottom of the shear zone. Strann rate reacted a mares of 0.05 <br />inches pex day, bat evenmaIIy reduced to nearly zero as shown on Figure 3. <br />Inspections revealed ~ signs of incipiert Caacks due >n the observed slide movement Since slide ~vemem <br />bad ceased, the ownets request for refilling the reservoir was approved. Monitoring of the stmchne and the <br />h~slide during ccnholled Elting was provided inr in the fiIIiug and monitoring phm. The reservoir was filled <br />to within 2 feet of spffi dining fire initial2 weeks of the re5lling phase and remained above ffie reshictioa for a <br />total of 6 weeks <br />Slide acttvity remained doh d®g the entire re5lling phase of the investigation based on tl~ i~linometer <br />measurements. embankment piezometras continued to conelafe weIl with histuriC records for increased <br />reservoir level Embankment pieromete~ P-l, has hisrorically reported the phreatic wager stature, in the left <br />portion of 9re dam, 12 Ext lower than its ooavflapart, P-2, located near ~ central section The differences <br />between h:vels in the two piezometers stows that the draiq ioshulled in 1985 downstream of P-1, was <br />f~tio~g as intended to reduce the level of saturation on the left downsream embankment surfacc_ <br />Abutment piezometers in 8re hmdstide showed a steady decline while the reservon- was drawn down foIlowiug <br />the runoff period Piezomders INGl and P~3A were targeted to primanly reflect pore pressure within the <br />shear zone. During the re-fritmg phase, PZ-1, downsream of Ere Leff toe, rcporlEd iasaeases in water level <br />ocrrespondmg to increases in the reservoir level However, the matrix level was about 5 feet lower than the <br />highest level recorded duzmg the rmtoff period. Water Lwels in inclinometer INGI showed only a slight <br />increase doriag the refiDing phase while PZ3A and B showed m inerrses. <br />The motion resohs support the belief that Lmdalide movement is ire seasonal and triggered almost <br />eachrmely by pore pressure in$nences from sources other Bran the reservoir Meltiutg snow on the hrllsrde <br />above the dam most likely infiihates the surface reliefcracJcs in the debris near the bead of Ere slide. The added <br />weight of the snow and the inereased saturated weight of slide material increases the driving force, tensing <br />movement <br />Measurements of survey tents showed magnitude and direction of movements whic3r coaelated well with <br />the inclinome9ers. Movement of survey moments clearly showed the previously observed crack defines the <br />upsheam bomrdazy of the sIlde. Mommrnts along the hft side of the sack moved paraIlel to the originally <br />observed surface hate, while tLose m the right of the crack showed liffie or no movemem. Also, the pattern of <br />movement appears io i~icate rotation as if the dam were deflecting &e lower portion of the slide in a <br />downstream direction. <br /> <br />