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The site general geology was described in a preliminazy geologic evaluation report <br />prepared by F.M. Fox Associates, Inc. ~ at the time of original DMG permitting in <br />1978. A copy of this document is included as Attachment A for reference. The site is <br />underlain by a thin veneer of hillside colluvium (up to several feet), which is in tum <br />underlain by metamorphic rocks varying from schist to granitic gneiss. The <br />colluvium is Pleistocene to Holocene (Recent) and the bedrock is Precambrian. <br />Pleistocene alluvium reportedly exists at the extreme western edge of the site, but is <br />not of interest because it is west of the active mining operations. <br />The Fox report appeazs to be based on the Reconnaissance Geologic Map of the Pine <br />Quadrangle (1:24,000)Z. A copy of an excerpt from that map showing the project site <br />area is included as Attachment B to this report. The geologic information included in <br />this reference confirms bedrock consisting ofmigmatitic biotite gneiss with biotite <br />schist, granitic gneiss, and amphibolite. General geologic structure mapped near the <br />quarry includes north to northwesterly striking, easterly to northeasterly dipping <br />foliation and metamorphic compositional layering generally pazallel to the foliation. <br />Dips aze shallow to moderately steeply dipping, and generally into the hillside at the <br />quarry site. <br />With respect to the four summazy and conclusion items included in the Fox report, <br />BrierIey Associates offers the following updated comments: <br />1. We concur that the site bedrock is composed of compositionally layered <br />metamorphic rocks that include interlayered biotite gneiss, biotite schist, <br />amphibolite and granitic gneiss. These rocks aze commonly referred to as the <br />"Idaho Springs Formation" as indicated in the Fox Report, but are referred to as <br />undifferentiated metamorphic rocks of Precambrian Age (1,700 - 1,800 m.y.) on <br />the Geologic Map of Colorado 3 In addition, because of the migmatitic texture of <br />the predominant gneissic rocks, irregular bodies of rock composed of granitic <br />lithology also occur within the layered metamorphic rock types. <br />2. We concur that metamorphic foliation is developed parallel to well-developed <br />metamorphic layering, which generally dips moderately steeply into the hillside. <br />The Fox report indicates an easterly dip. Our mapping efforts indicate an average <br />northeasterly dip as discussed further below. <br />3. We concur that the rocks presently exposed do not exhibit any prominent faulting. <br />We do find there to be mappable jointing in the rock mass, in addition to the <br />foliation jointing. One could azgue this jointing is not "prominent" in that it is not <br />continuous over hundreds of feet, there aze jointing trends continuous over tens of <br />feet that could affect slope stability as discussed further below. <br />~ Preliminary Geologic Evaluation of a Proposed Aggregate Quarry Site at Shaffer's Crossing, Jefferson <br />County, Colorado; F.M. Fox & Associates, Inc.; May 5, 1978. <br />z 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 />' Geologic Map of Colorado; Compiled by Ogden Tweto; U.S. Geological Survey (ln Cooperation with <br />The Geological Survey of Colorado); 1979. <br />JC 00770 <br />petersonlElk Creek: <br />