2016-03-28_REPORT - M1980149 - Laserfiche WebLink

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Hall-Irwin Corporation Hokestra Slurry Walls October 30, 2014 ' Page 7 of 8 3 COMPACTED CLAY LINER OVERVIEW ' J&T Consulting Inc. was retained by Brierley Associates to design the clay liner. A J&T engineer performed field visits throughout the construction phase of the project. The main function of the onsite engineer from J&T was to observe keyway excavation, and to determine the final depths of the keyway ' in the field. The contractor who installed the clay liner was Claystone Construction (CC). CC utilized a combination of equipment to process on-site bedrock from the bottom of the reservoir which included; scrapers, water wagon, CAT 815 with sheeps foot rollers, CAT D6 dozer, and tractor with disc ' attachment. This material was used for the core of the clay liner and is referred to as Zone 1 material in the daily field reports. The overburden material along the clay liner alignment was processed with the equipment listed above, and was used for the shell of the clay liner. This material is referred to as Zone ' 2 in the daily field reports. Martinez Associates was retained by Brierley Associates to perform full-time quality control observations and testing. The daily compaction testing and observation reports are presented in Appendix E. ' Martinez Associates (MA) performed soils testing that conformed to the project specifications. The soils tests performed on the onsite material were proctors, gradations, atterburg limits, moisture contents, and density. Construction observation and testing began on 4-30-13 and stopped on 9-10- ' 13. The project site suffered flood damage from a large rain event that spanned from September 9-12, 2013. Construction observation resumed on 6-9-14 and finished on 6-11-14. The moisture density tests were completed by nuclear gauge and sandcone methods. A total of 706 moisture density tests by nuclear gauge were recorded. There were 35 failures that have passing re-tests in the same locations and elevations. Eight sandcone tests were performed as a comparison to the nuclear gauge results. The sandcone test results indicated that the nuclear gauge moisture content readings were not accurate. The project team decided to have MA collect three samples of zone 1 material daily from ' underneath the nuclear gauge test sites. These samples were bagged and transported back to MA's laboratory for moisture content determinations. The average of the three samples was obtained, and that value was used to recalculate the wet density value for the nuclear gauge readings. The corrected wet density values were used to recalculate the nuclear gauge percent compaction results. Zone 2 material was not tested by conventional methods in the beginning of the project. A combination of full-time observations on material processing and the use of a T-probe were used to determine the acceptance of the material. The project team decided to have MA perform a rock corrected proctor on the overburden sand and gravel material. This would allow MA to use a nuclear gauge on Zone 2 material. MA's field technician would complete a sieve analysis in the field to determine the amount of oversized material at the nuclear gauge test sites. The percentage of oversized material was used to obtain a rock corrected proctor value. This procedure was performed to establish a sliding scale value for the maximum theoretical density based on the amount of oversized material at the nuclear gauge test sites for Zone 2 material. 3.1 Slurry Wall Alignment Survey ' The clay liner alignment was staked and surveyed by Morningstar Surveying LLC (MS) before construction of the working platform and after construction of the clay liner. Alignment stationing was established at 100-ft intervals. To generate the as-built alignment, Hall-Irwin placed lathe at various ' locations of the clay liner and MS surveyed the lathe to create the as-built point list shown in Appendix ' BRIERLEY ASSOCIATES Creating Space Underground