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(( (( l( ()j - r- Hi .~ p' (~-I ~ c::: ABSTRACT The purpose of the Phase II investigation of the Glenwood-Dotsero Springs unit was to evaluate the feasibility of collecting saline waters from the Glenwood and Dotsero Springs and piping these waters to a series of evaporation ponds west of Mack, Colorado. This plan was originally developed in the Phase I investigation in which it was estimated that 13.8 mgd of saline waters could be collected at the springs and piped to evaporation ponds covering an area of approximately 5,700 acres for a period of 100 years. 'The Phase II investigation incorporates the findings of this initial study into a more detailed investigation. This report considers th€ influence of the geologic conditions at the Contour Ponds Site on development of ponds for the evaporation of saline water. The scope of the investigation included drilling exploratory holes at 23 locations. Soil sampling, rock coring, and permeability testing of surfical soils and bedrock were performed. Selected samples were tested in the laboratory for classification and to identify their recompacted engineering properties. In addition, a geologic reconnaissance of the site was performed. The geologic conditions at the site, as determined from the investigation, are characterized by shallow (2 to 31 feet thick) Quaternary deposits overlying 500 to 1,400 feet of Cretaceous age Mancos shale. The primary Quaternary deposits consist of pediments (2 to 31 feet thick), alluvium, and alluvium-colluvium mixed (1 to 10 feet thick), and residuum (0 to 4 feet thick). With the exception of the more gravelly materials within the pediments and less weathered residuum, all of the materials are suitable for use as compacted clay liners. The permeability of these materials when recompacted ranged from 3 x 10-7 to 2.2 x 10-9 cm/sec (4.3 x 10-4 to 3.1 x 10-6 in/hr). Overall, Overall, the materials do not have a high shrink-swell potential, however, when designing liners consideration of their shrinkage potential will be necessary. On-site gravels within the pediment deposits are suitable for bedding material for pipeline construction, but will require some selective sorting. The soundness of the gravels is questionable due to the presence of shale and therefore they probably cannot be used as concrete aggregate. All near surface soils contained high levels of soluble sulfates and use of Type V cement in concrete used on-site will be necessary.