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<br />Mr. William paddock'- <br />December 3. 1993 <br />Page. 2 <br /> <br />~ <br /> <br />Phase I . Exploration <br /> <br />This initial phase involves coring and testing 4 or 5 boreholes in the embankment and <br />left abutment to obtain soil and rock strength parameters, permeability data, pumping test <br />information and to install monitoring piezometers. <br /> <br />This data will be used to analyze the embankment and abutment using a seepage <br />analysis modeling program and a slope stability model. These models will be modified as <br />water levels and flow conditions change in order to determine the most effective location <br />for drain installation. <br /> <br />The estimated cost for this phase of study is: <br /> <br />$48,500.00 <br /> <br />Perform Spring, 1994. <br /> <br />Phase II - Drain Installation <br /> <br />Following observations of piezometer fluctuations with reservoir level changes and <br />the initial seepage and stability analyses, Harza anticipates that the second stage may <br />consist of drilling a series of vertical drains extending along the downstream core filter <br />into sand and gravel overlying bedrock under the dam. <br /> <br />These drains are anticipated to release water in the potentially blocked filter, cross <br />potential zonation of the downstream shell and cOlmect for discharge into the sand and <br />gravel underlying the downstream shell. For costing purposes, six vertical drains are <br />planned. Evaluation of the performance of these drains will require a second season of <br />reservoir fluctuation. <br /> <br />The estimated cost for this phase of remedialion is: <br /> <br />$100,000.00 <br /> <br />Perform Summer, 1994. <br /> <br />Phase 1/1 . Drainage Extension <br /> <br />If vertical drains do not function efficient! y to reduce seepage and to increase the <br />embankment factor of safety, lateral drains may be required to facilitate drainage from the <br />vertical drain systems. These horizontal interceptlJr drains would be drilled from the toe <br />of the dam to intercept the vertical drains and would be gravel packed with a piped <br />discharge. The maximum length of these borings would be about 150 feet. Three laterals <br />would be required. <br /> <br />The estimated cost for this phase would be approximately: $74,000.00 <br /> <br />Page 13 of 15 <br />