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B-L Brenneman Primary Bulkhead <br /> Construction Certification Report <br /> Page 3 <br /> It was anticipated that water addition to the mix would <br /> decrease concrete strength therefore the original design was <br /> modified to account for a possible strength loss from 3000 psi <br /> to 2500 psi and the bulkhead was constructed accordingly. <br /> This modification was submitted to and approved by the <br /> Division and Board (TR-16) . <br /> It was not anticipated that pumping difficulty would be <br /> experienced requiring addition of Portland Type V cement to <br /> increase pumpabili ty of the mix. This was a field <br /> modification which allowed construction to proceed and would <br /> only serve to increase the concrete strength obtained. <br /> Concrete pumping was started on May 23, 1994 after final <br /> inspection but an inability to pump the concrete mix the <br /> entire distance to the bulkhead resulted in suspension of <br /> construction until the following day with no concrete having <br /> entered the bulkhead form. On May 24, 1994, the pour was <br /> again attempted with similar results because of segregation in <br /> the pipeline. At that time, additional Portland Type V cement <br /> was added to the mix (see attached letter report from John <br /> Abel) which prevented segregation. The pour was then <br /> completed in 4 1/2 hours. The impact of this change should be <br /> a higher strength concrete than would have been achieved <br /> without the addition. <br /> During the pour , 3 separate (3-4 test cylinders each) were <br /> taken. The approximate cumulative yardage points where <br /> sampling occurred were 1) 2. 9 yards , 2) 5. 8 yards and 3) 8 . 4 <br /> yards (end of pour) . The cylinders were cured at the bulkhead <br /> site until time for break tests. Test cylinders from each <br /> sample set were broken at 7 days and 28 days with the <br /> remaining cylinders being saved for retest if required. The <br /> average break strength at 28 days was 7003 psi with the lowest <br /> break being 5290 psi . This low break (as compared to the <br /> others (7860 psi average) and its 7 day test cylinder (6030 <br /> psi) ) might have been due to a damaged cylinder but is still <br /> twice the 2500 psi required, therefore no additional testing <br /> is planned. The test reports are attached. <br /> e) Low pressure grouting of the concrete-rock interface. <br /> Drilling and grouting of the B-L Brenneman Primary bulkhead <br /> took place on June 2, 1994. A total of 8 holes were drilled <br /> into confirmed rock . The targeted contact intersection points <br /> were at the approximate center of the bulkhead at the left <br /> rib-sill intersection, left rib-midway between sill and back, <br /> left rib-back intersection, back center , right rib-back <br /> intersection, two holes at approximately the third points <br /> between back and sill and the rib-sill intersection. <br />