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<br />. ._~._..~_-"'-.,c=-'-='~~._. - ''''-'-'''- - ..<--....".--- <br /> <br />(. <br /> <br />......:.-~.;~~._4:__."_ <br /> <br />foundation have been perfonned. The deepest of the holes drHled previously <br />penetrated 73 feet into the foundation material downstream of the dam but <br />never reached bedroc~. <br /> <br />MKE shall drill four bore holes with a high emphasis on gathering as much <br />information as possible from the holes. In this way, the previous bore holes <br />can be correlated and conclusions can be drawn as to the path of the seepage <br />flow. Three of the holes shall be drHled from the crest of the dam through <br />the embanlcment and "into the glacial till that forms the foundation. An <br />attempt shall be made in at 1 east one hol e to reach bedroclc so that the <br />possibility of a true positive cutoff can be investig~ted. A fourth hole <br />shall be drilled through the slurry trench cut off. The bore holes shall be <br />systematically sampled by the split spoon or California method at 5-foot <br />intervals, or where changes in material are detected. Bore hole permeability <br />tests shall be perfonned every ten feet to determine the distribution of more <br />or less pervious strata. Undisturbed samples shall be obtained as required of <br />the embanlcment and foundation for classification in the laboratory and deter- <br />mination of strength characteristics for use in the stability analysis. In <br />the event one or more of the bore holes does reach bedroclc, it shall be cored <br />and packer tested to a depth of at least ten feet. Upon completion of a bore <br />hole, multiple stage, standpipe piezometers shall be installed in strata of <br />varying permeability within the hole in order to allow measurements of the <br />phreatic surface. In addition, several test pits and trenches shall be <br />excavated on and around the dam to correlate the physical characteristics of <br />the embanlcment and the foundation with the samples obtained from drilling, <br />where a particle size restriction exists. Test pits shall also be used to <br />assess the thickness of riprap and the quality of the upstream impervious <br />blanket and slurry trench cutoff. In addition, seismic lines shall be run <br />along the crest of the dam in order to define the dam/foundation contact and <br />the top of bedroclc. <br /> <br />7.2.2 Peterson Dam <br />Previous geotechnical investigations and dam records identify some of the <br />problems associated with Peterson Lalce Dam'. but fail to define the deficien- <br />cies. Four holes drilled in the embanlcment.produced little useful information <br /> <br />-9- <br />