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<br /> <br />Portland Limestone Quarries (M-1977-344) Permit Amendment-02 <br />Holcim US Inc, 3500 Highway 120, Florence, CO 81226 Revised pursuant to preliminary adequacy review November 20, 2023 <br />Phone (719) 288-1443 www.holcim.us 90 <br />2.7 Exhibit G: Water Information (Rule 6.4.7) <br /> <br />2.7.1 Existing Conditions <br />The RCQ lies within the Great Plains physiographic region of Colorado and consists of Cretaceous <br />Seaway Sedimentary rocks (Barkmann 2021). The Cretaceous sedimentary rocks of the region were <br />deposited from an inland sea that divided the North American continent into two landmasses <br />approximately 100 million years ago. The shifting coastal seashore line resulted in the varying marine <br />environment responsible for the deposition with shallow water deposition represented by the sandstone <br />units and deep water deposits represented by limestone and shales (Pinel, 1977). <br />The topography at the Site is generally flat with some local relief along surface water drainages with shale, <br />limestone, and sandstone outcrops. The overall gradient slopes downward to the northeast towards Red <br />Creek and the Arkansas River. Within the Red Creek drainage, sequences of erosion and deposition <br />resulted in multiple alluvial stream terraces covered to varying degree in vegetation. <br />The Water Quality Control Division classification for Red Creek is COARUA14a based on the information <br />obtained from the Colorado Department of Public Health and Environment Clean Water GIS website <br />(https://cdphe.colorado.gov/clean-water-gis-maps). Below are the 5 CCR 1002-32 water quality standards <br />for COARUA14a (Table 2.7.1-1). <br /> <br /> Table 2.7.1-1: Regulation 32 Water Quality Standards for COARUA14a <br />Within the Red Creek drainage are seeps and springs flowing from fractures within the rock outcrop. <br />Minimal water flow was observed in alluvial sediments above the seep location indicating minor flow within <br />Red Creek independent of the identified seeps. <br />The surface water flow disappears into the creek sediments and Red Creek is dry at the boundary of the <br />Site. Drainages south and east of Red Creek show signs of intermittent to no surface water flow. Upland