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April, 2004 <br />1.0 INTRODUCTION <br />The purpose of this study and supporting documentation is to provide a design for a low <br />water crossing of the Boulder Creek at the Turnpike Mining Pit. The crossing is to be <br />utilized during gravel mining operations by Asphalt Specialties at this site and will <br />enable maximum 68-ton tandem axle trucks to cross Boulder Creek and access all <br />areas of the site. The crossing is considered to be a temporary structure, used only <br />during mining activities at the site and is not designed to convey anything more than an <br />average annual peak event. The owner understands that this structure is considered to <br />be a temporary structure designed for relatively low flows. Failure of the crossing could <br />occur at anytime the Boulder Creek water surface exceeds elevation 4939.0. <br />1.1 SITE LOCATION <br />The proposed Turnpike Gravel Pit site is located in Section 31, Township 2 North, <br />Range 68 West of the 6`" Prime Meridian. The site is roughly 4-miles west of Interstate <br />25 in the northeast quadrant of the intersection of Highway 52 and County Line Road in <br />Weld County. The low water crossing will be located in the south 1/2 of the northwest <br />1/4 of Section 31, T2N, R68W of the 6'~ Prime Meridian. (See Vicinity Map provided in <br />Appendix A) <br />1.1 SITE DESCRIPTION <br />The proposed Tumpike Gravel Pit lies on approximately 275 acres in the Boulder Creek <br />floodplain. The existing site topography is relatively flat but mildly sloping to Boulder <br />Creek. The average slope across the property is approximately 1 percent. Soils are <br />generally considered to be silty clays with underlying alluvial deposits of sand and <br />gravel. Vegetation is limited to native low-lying shrubs and plants with some larger <br />trees growing close to Boulder Creek. A thin strip of wetland vegetation occupies a <br />drainage swale in the southwest corner of the site. Other significant features on the site <br />are the Plumb and Dailey Irrigation ditch and several oil wells. None of these features <br />will be disturbed by the construction of the low water crossing. <br />Turnpike Pit Low Water Crossing Design Report <br />Page 1 of 6 <br />