2020-05-26_PERMIT FILE - M2020029

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Geotechnical Engineering Report lrerracon Carr Aggregate Pit ■ Carr, Colorado April 23, 2020 ■ Terracon Project No. 20195087 GeORepOrt. PROJECT DESCRIPTION Our final understanding of the project conditions is as follows: Item Description Information Provided The following project information was provided to us in a notice of intent(NOI) to the State by Kiewit and through conversation with the client. We understand the project includes an investigation for a new aggregate pit Project Description in Carr, Colorado. We understand the gravel pit will cover an approximately 640-acre area; however, the current scope of services includes only 160- acres. If project information or assumptions vary from what is described above or if location of proposed mining changes, we should be contacted as soon as possible to confirm and/or modify our recommendations accordingly. GEOTECHNICAL CHARACTERIZATION Geology The project area is located within the Colorado Piedmont section of the Great Plains physiographic province. The Colorado Piedmont, formed during Late Tertiary and Early Quaternary time (approximately 2,000,000 years ago), is a broad, erosional trench which separates the Southern Rocky Mountains from the High Plains. Structurally, the site lies along the western flank of the Denver Basin. During the Late Mesozoic and Early Cenozoic Periods (approximately 70,000,000 years ago), intense tectonic activity occurred, causing the uplifting of the Front Range and associated down-warping of the Denver Basin to the east. Relatively flat uplands and broad valleys characterize the present-day topography of the Colorado Piedmont in this region. Surficial geologic conditions mapped in the vicinity of the site ('Hershey and Schneider, 1978), (2Tweto, 1979), include Quaternary Gravels (Qgo) and Valley Fill terrace deposits (Qvf and Qt) which has been described as arkosic sand and gravel, which may be locally cemented. Bedrock units mapped in the vicinity of the site include the Laramie Formation (KI). Bedrock was encountered in our borings and test pits at depths ranging from about 3'/z to 13'/2 feet below existing ground surface. The bedrock formations in the area have been reported to include mostly 'Hershey, L.A., and Schneider, P.A., 1972,Geologic map of the lower Cache La Poudre River basin,north-central Colorado: U.S. Geological Survey, Miscellaneous Geologic Investigations Map 1-687, scale 1:62,500. 2 Tweto, Ogden, 1979 Geologic Map of Colorado, United States Geological Survey. Responsive■ Resourceful ■ Reliable 2