2020-02-28_REVISION - M2015033 (8)

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Varra Companies, Inc. OFFICE OF SPECIAL PROJECTS 8120 Gage Street Frederick.CO 80516 Teleahone(303)666-6657 Fax(303)666-6743 Fridav 29 Fehriiary 2020 To: Peter Hays,E.P.S. Colorado Office of Mined Land Reclamation(OMLR,or `the Office') 1313 Sherman St.,#215 Denver,CO 80203 From: Varra Companies,Inc. � RECEIVED Bradford Janes,Forester Liaison,Interdisciplinary Affairs FEB Subject: Tecnnicai Revision 1;2—Reviseu trading Han Parcel 122—Resource Develonment Proiect DIVISIOi, —AATION "MIR Permit M4015-033 MINING AND SAFETY This Technical Revision is directed at addressing concerns of stability of extracted slopes as expressed in the OMLR inspection report of 12 December 2019. Please refer to the included attachments. Two copies of the Technical Revision(TR)include the Technical Revision Form,this correspondence,referenced maps and drawings,a Stability Analysis Report,proof of submittal to Weld County for placement at the Weld County Clerk to the Board,and the required Technical Revision Fee(Check#53383), are included; as described under Attachments, below. Tract A is the focus of the 12 December 2019 inspection report. The report also noted the stockpiling of soil and other pit run within Mineral Area Reserve 2,and not on Mineral Reserve Area 1. This Revision shows the current extent within Mineral Reserve Area 2. It also adjusts any expectation of sequencing of the placement of materials in these locations. The designations were simply to distinguish one Area from another, but for clarification of activities at these locations going forward; both Areas may occupy materials stockpiles,equipment or other support materials simultaneously during the life of the operation. The balance of this TR focuses upon the nature and stability of the extracted slopes. To this end,five line transects were measured by hand held laser on 9 January 2020, showing an ocular mean of perceived benching that appeared representative of affected slopes. This information was used in part and shown in the included Stability Analysis Report. In order to improve the understanding of the extracted basin, for the first time we acquired ground elevations through the use of a drone on 23 January 2020. The conditions revealed were simply impossible in prior times through the use of ground survey or hand held devices. The resulting topography extracted from the more than 50,0001 points of data shows what would be expected in a basin undergoing active extraction-variability. To make better sense of the variability, six line transects were placed to better capture and reflect the range of variation at play for the Stability Analysis Report to be measured against to better assure the site