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Connie Davis <br /> TETRA TECH June 28, 2016 <br /> Page 2 <br /> As a result of these two factors, we elected to make field adjustments to the plan to account for <br /> the loss of the borrow area. In summary, riprap armoring was placed along the unreinforced <br /> erosion banks within the breach. No additional riprap was placed on the emergency berm that <br /> was constructed by Thornton in 2015. Some alluvial fill material was recovered from the borrow <br /> area and placed within the erosion feature in order to provide a stable platform for riprap <br /> installation. This fill was compacted with a CAT815 sheepsfoot compactor. Verification testing <br /> was not performed because of the accelerated construction schedule. <br /> Construction of the interim mitigation action was substantially completed on April 28, 2016. To <br /> the best of my knowledge, the work was completed in accordance with the design memorandum <br /> from Tetra Tech (dated April 14, 2016), as modified by field adjustments described above. Fill <br /> material, where placed, was compacted to either 95% standard proctor density or 70% of <br /> relative density. <br /> Sincerely, <br /> TETRA TECH <br /> 1 <br /> Jeffrey A. Butson, P.E. <br /> Project Engineer <br /> PA23514\133-23514-16004\ProjMgmt\Correspondence\Certification for Interim Action at Cooley West.docx <br />