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foliation. Dips are shallow to moderately steeply dipping, and generally into the hillside at the quarry <br /> site. <br /> The Brierley Report indicates that the site had evolved into a <br /> With respect to the four summary and conclusion items included in the Fox report, Brierley Associates <br /> offers the following updated comments: <br /> 1. We concur that the site bedrock is composed of compositionally layered metamorphic rocks <br /> that include interlayered biotite gneiss, biotite schist, and amphibolite and granite gneiss. These <br /> rocks are commonly referred to as the "Idaho Springs Formation" as indicated in the Fox Report, <br /> but are referred to as the undifferentiated metamorphic rocks of Precambrian Age(1,700-1,800 <br /> m.y.)on the predominant gneiss rocks, irregular bodies of rock composed of granitic lithology <br /> also occur within the layered metamorphic rock types. <br /> 2. We concur that metamorphic foliation is developed parallel to well-developed metamorphic <br /> layering, which generally dips moderately steeply into the hillside. The Fox report indicates an <br /> easterly dip. Our mapping efforts indicate an average northeasterly dip as discussed further <br /> below. <br /> 3. We concur that the rocks presently exposed do not exhibit any prominent faulting.We do find <br /> there to be mappable jointing in the rock mass, in addition to the foliation jointing. One could <br /> argue this jointing is not"prominent" in that it is not continuous over hundreds of feet,there <br /> are jointing trends continuous over tens of feet that could affect slope stability as discussed <br /> further below. <br /> 1 Preliminary Geologic Evaluation of a Proposed Aggregate Quarry Site at Shaffers Crossing,Jefferson <br /> County Colorado; F.M. Fox Associates, Inc.: May 5,1978 <br /> 2 Reconnaissance Geologic Map of the Pine Quadrangle,Jefferson County, Colorado; by Bruce Bryant; <br /> Miscellaneous Field Studies Map MF-598; U.S.Geological Survey; 1974 <br /> 3 Geologic Map of Colorado; Compiled by Ogden Tweto; U.S. Geological Survey( In Cooperation with <br /> The Geological Survey of Colorado);1979 <br /> 4. We concur that the favorable attitudes of the dominant foliation into the hillside is generally <br /> compatible with the originally proposed 1:2(H:V) slope ratio. Additional discussion about slope <br /> stability and proposed steepened slopes is included in the slope stability section below. <br /> Finally,the Geologic Map of Colorado (1:500,000) indicates two northwesterly faults transecting or <br /> passing just southwest of the site. These faults would be considered inactive and cut across the both <br /> Precambrian metamorphic rocks that occur southeast of U.S. 285 and slightly younger granitic rocks <br /> (Silver Plume Quartz Monzonite and Pikes Peak Granite)that occur northwest of the highway. <br />