2017-06-26_GENERAL DOCUMENTS - M1992074

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r t DER SUBSURFACE SUBSURFACE CONDITIONS From the ground surface down, the general subsurface profile encountered in our borings consisted of: Fill Approximately 2 to 7 feet of silty to very clayey sand with gravel or sandy to silty clay fill was encountered at our boring locations within the mined-out portion of the gravel pit. Information provided by CSU representatives indicate the fill materials are waste portions of mined soils that have been placed back across the pit floor. This soil was typically reddish-brown, moist, and medium dense to dense or stiff. Gravelly Sand Silty, gravelly sand was encountered underlying the fill materials or at the ground surface in all of the borings, and extended to depths of 19 % to 35 % feet below the existing ground surface. The silty, gravelly sands were also encountered overlying the formational shale bedrock described below. The sands were generally reddish-brown, light to dark brown, slightly moist to wet, and medium dense to dense. Clay and Silt Slightly sandy to sandy clay as well as some thin silt lenses were encountered beneath the units described above in 7 of the 8 borings. The clays and silts were generally reddish-brown to olive, moist, and firm. Claystone Bedrock Sandy claystone bedrock of the upper members of the Pierre Shale Formation was encountered beneath the silty sand soils described above and extended to depths of approximately 22 and 22 'A feet below the existing ground surface in two borings. The claystone bedrock was generally olive-brown and moist. Formational Shale Bedrock Shale bedrock of the Pierre Shale Formation was encountered beneath the silty sand unit and claystone unit described above and extended to the maximum depths explored of approximately 20 %to 67 %feet below the ground surface. The formational bedrock was generally dark gray, moist, and hard to very hard. The boring logs in Attachment B should be reviewed for more detailed descriptions of the subsurface conditions at the boring location explored. Groundwater Groundwater was encountered during our field exploration in 3 borings. However, soil moisture levels and groundwater levels commonly vary over time and space depending on seasonal precipitation, irrigation practices, land use and runoff conditions. These conditions and the variations that they create often are not apparent at the time of field investigation. Accordingly, the soil moisture and groundwater data in this report pertain only to the locations and times at which exploration was performed. They can be extrapolated to other locations and times only with caution. Monitorina Well Installation Monitoring wells were installed in the 3 borings where groundwater was encountered (GP-2-2, GP-2-6, and GP-2-8). We understand the monitoring wells will be maintained by CSU. The 99533=13811113 Page 2 of 3 December 22,2008 Copyright 2M Kleinfelder