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<br />(( <br /> <br />c( <br /> <br />l( <br /> <br />C"") <br />C'J <br />r--- <br />( ::; <br />c:) <br />Q' <br />1. <br /> <br />1 <br /> <br />INTRODUCTION <br /> <br />_The Phase II salinity investigation involves evaluating the <br />feasibility of collecting saline waters from the Glenwood and <br />Dotsero Springs units and piping these waters to a series of <br />evaporation ponds 8 miles west of Mack, Colorado for disposal. <br />This plan was originally developed in the Phase I investigation <br />of the Glenwood and Dotsero Springs units in which it was <br />estimated that 13.8 mgd of saline waters could be collected and <br />evaporated over a water surface area of 5,700 acres for a period <br />of 100 years. <br /> <br />To maximize evaporation, it was proposed in Phase I that a series <br />of 9 foot high dikes would be constructed. These dikes would be <br />spaced at approximately 600 foot intervals and contour the <br />existing topography to minimize excavation, hence the name for <br />the site became the Contour Ponds Site. To reduce seepage, it <br />was also proposed that the Mancos shale at the site could be <br />recompacted in place to form a 1 foot thick liner over the entire <br />site. This original design was based on a cursory review of the <br />literature and site visits. <br /> <br />The purpose of this report is to present the results of the <br />geologic investigation of the Contour Ponds Site and to provide <br />recommendations for the design and construction of the contour <br />ponds based on these findings. Figure 1 shows the location of <br />the Contour Ponds Site in relation to Mack and Grand Junction, <br />Colorado. The following sections describe in detail the findings <br />of the investigation and design and construction considerations. <br /> <br />To briefly summarize the scope of the study, our field <br />investigation consisted of drilling 23 boreholes at the locations <br />shown on Plate 1. An additional 26 auger holes were drilled at <br />selected borehole locations where additional soil sampling and <br />falling and/or constant head permeability testing was performed. <br />Soil samples obtained from the investigation were tested in the <br />laboratory for the purposes of classification and evaluation of <br />their potential for use as construction materials (Appendix B). <br /> <br />Based on a review of the literature, field investigations, <br />laboratory testing, and geologic reconnaissance of the site, <br />a review of the regional (Section 2) and site geology (Section 4) <br />was compiled which included a surficial geology map (Plate 1) and <br />geologic cross sections (Plates 2 and 3) for the site vicinity; <br />the seismic activity in the area of the site was addressed <br />(Section 3); the material properties of the soil and bedrock <br />encountered were evaluated (Section 5); ground water conditions <br />at the site were addressed (Section 6); the findings were applied <br />to the proposed construction of the contour ponds (Section 7); <br />and our conclusions with respect to areas requiring additional <br />evaluation are presented in Section 8. <br />