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A AGGREGATE Mr.Tyler O'Donnell,Division of Reclamation Mining and Safety INDUSTRIES March 11, 2016 Page 2 excess overburden that came from the site and was used to construct the 3:1 sloping around the reservoir. Type M riprap from the Morrison Quarry is granitic gneiss. The goal of the work Al proposes in TR-05 is to reinforce the emergency repairs performed in July and August,2015 by City of Thornton's contractor. The work to be performed by Al is not designed to provide a permanent, engineered solution but rather is intended to be completed as a temporary measure prior to Spring 2016 runoff to provide additional protection and reduce potential flood flows to the reservoir. This temporary reinforcement will be torn out by Thornton when permanent repairs and flood control mitigation measures are completed in accordance with its design plans. On that premise,Al responds to adequacy items 4 and 5 as follows: 4) Pursuant to Rule 6.5.2,please provide a compaction and density specification for the backfilied embankment. At a minimum the Division will accept maximum 12-inch loose lifts compacted to 95 percent of maximum dry density(ASTMD698). As the backfill activity to be performed under TR-05 is intended to be a temporary repair that will be removed at a later date,Al is not designing the repair work to ASTM standards for compaction and density. In accordance with AI's discussions with City of Thornton in this matter, Al incorporates additional detail regarding the proposed repair as follows: • Area I will be filled using pit run or backfill material placed at a maximum of 12- inch loose lifts compacted with a Cat 815 compactor, sloped 20:1. • In Area 2,type M Rip-Rap will be mixed with clay soils,placed 2-feet thick and sloped 10:1. The aerial photo drawing submitted with AI's TR request has been revised(enclosed)to incorporate the above additional detail. 5) Please commit to submitting to the Division within 60 days of completion of the backfill, a certification by a qualified engineer certifying that the backfill has been constructed to the required compaction and specifications, approved through TR-05. As compaction and density specifications are not proposed for this temporary repair,this commitment is not applicable. 6) Comment: The Division still has an outstanding corrective action far a problem cited in the July 2 and 9, 2015, inspection report for Sediment Control and Backfilling and Grading. Problem and Corrective Action from the July 2 and 9, 2015, inspection report: PROBLEM:A breach between the River and phase 2 has occurred. The breach has headcut back towards the River, eroding the land between the River and phase 2. Erosion is occurring in areas where the flow is overtopping the earthen embankments between