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Rinderle Construction Surficial Geology Investigation, High Desert AFT Subdivi:.ion D & 35 Roads, East Orchard Mesa, Palisade, CO May 4, 2001 Page 4 The exploration holes indicate that the top of the Formation is relatively flat and that subsurface drainage would probably be quite slow. While it is believed that under the existing conditions at the time of this exploration the construction process would not be effected by any free-flow waters, it is very possible that several years after development is initiated, a troublesome perched water condition may develop which will provide construction difficulties. In addition, this potential perched water could create some problems for existing or future foundations on this tract. Therefore it is recommended that the future presence of a perched water table be considered in all design and construction of both the proposed residential structures and any subdivision improvements. SURFACE WATER The site is partially dissected by branch gullies of Sink Creek. The majority of storm drainage which could affect this site, would originate on-site, with minor storm water effects originating off-site from the west facing slopes of the Grand Mesa. Drainage from the Grand Mesa is routed into established drainages and various alluvial valleys to the northeast and east. Most surface water will be diverted into Sink Creek and eventually into the Colorado River. The site is not located within or immediately adjacent to a designated Flood plain. The gully bottoms of Sink Creek and associated gullies must be considered to have a flood haiard, generally `Flash Flooding' after periods of precipitation. ECONOMIC GEOLOGIC DEPOSITS Some sand, gavel or cobble deposits are believed to exist beneath this site and may be of some value for on-site use. These aggregate deposits are believed to be relatively thin in some areas and in excess of 20 feet thick beneath lots 7, 8 & 9. These aggregate deposits are covered with in excess of 2-I S feet of alluvial soils. It is not believed that any such sand, gravel or cobble deposits on this site could be economically extracted due to the rather limited extent of the deposits, the amount of overburden in some areas and the close proximity of the gullies and property lines. The upper `perched' ground water on this site is notorious for large amounts ofsoluble sulfate salts and other minerals. The upper `perched' water is not considered to be potable. It is not believed the shallow, perched ground water on this site would be considered a water resource for either potable purposes or for extensive irrigation. Approximately 2500 to 3500 feet below this site, confined waters in the Dakota, Summerville and Entrada Formations may be encountered but, are probably saline and would not be potable. Some petroleum and significant amounts of natural gas have been prospected for and extracted from the Dakota, Burro Canyon and Morrison Formations. The established producing gas fields are in the Bookcliffs, approximately 6 miles north and northeast of this site and on the slopes of Grand Mesa and Chatk Mountain to the east of the site. To our knowledge, exploration for natural gas or petroleum has not been accomplished in this portion of the Grand Valley. It is possible that natural gas deposits are present beneath this site but, development of these resources is prohibitive at this time and has not been considered an issue within this portion of the Grand Valley. Radioactive ores have been mined from the lower Burro Canyon and Morrison Formations, in the Uncompahgre UpliFl to [he south. In general, the producing mines and significanr deposits are located more than 20 miles south of [his site. Due to the depths of these formations beneath this site, in excess of 1400 feet, it is not believed that such deposits would be economic or that such deposits would adversely affect this site.