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<br />Koehler Tunnel bulkhead inspection Page 2 September 8, 2003 <br />bars had been tied into the rebar cages to prevent cracking of the <br />concrete where the bypass pipe passes through the rebar cages. <br />The dimensions of the bulkhead. forms were checked during the <br />inspection, The thickness of the bulkhead between the plywood <br />form faces was measured as 12-ft 1/2-in, slightly more than the <br />design 12-ft. Scaling of the loose rock and removal of the <br />ballast had increased the average bulkhead height to 10-ft 6-in <br />from original maximum height of 9-ft. Obviously, the originally <br />estimated 1-ft thickness of the ballast in the floor had been <br />exceeded. The originally maximum measured bulkhead width of 8-ft <br />6-in was more than the average 8-ft 5-in measured during the <br />inspection. The thickness of the red slime stuck to the tunnel <br />walls during the initial inspection of the Koehler Tunnel had been <br />slightly underestimated. <br />Scaling of the loose rock from the tunnel roof, walls and <br />floor provided a very irregular surface to resist the planned <br />thrust from the maximum static water head of 497-ft and from the <br />maximum credible 0,136g earthquake acceleration. The blocky <br />nature of the rock results in the irregularities present on the <br />back, ribs and floor extending more than 1-ft into the tunnel <br />cross section, considerably more than the specified 0.19-in. The <br />shape of the rock adjacent to the bulkhead is excellent for <br />resisting bulkhead movement under the design thrusts. The floor <br />of the tunnel in the bulkhead section was essentially dry except <br />for a few depressions partially filled with water. The water on <br />the floor must be removed immediately before starting the pour. <br />The pump for removing the water inside the forms was present <br />inside the form at the time of the inspection. <br />The adequacy of the rebar reinforcement was recalculated for <br />final bulkhead dimensions. The as built differences from the <br />~~r. iia c~i dcSigri re cl.llt °_tj i._ file CVeral'. tensile re !. P_f OrceID.ePt Qn <br />,g--, <br />the airside of the bulkhead exceeding the required tensile <br />reinforcement by 30~, as indicated on page 4 of the attached <br />calculation sheets. <br />Sincerely, <br />John F. Abel, Jr. <br />Colorado P,E. 5692 <br />cc. Larry Perino <br />2 <br />