1988-06-17_REPORT - C1981012 (2)

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measured to the nearest hundredth-foot using an electric line water level detector. The elevation at the top of the well casing was subtracted from the depth to water to obtain the ground water level below the ground surface. Water quality was sampled in the field directly from the wells with a hand bailer. The wells were cleared by bailing at least three columns of water prior to collecting the sample. Equipment and procedures used for water chemistry analysis were consistent with those described above for Surface Water. 3. 0 MONITORING RESULTS The geologic setting is an important factor when analyzing hydrology of an area. Stratigraphy in the region ranges in age from Pre-Cambrian to Quarternary. However, only the Raton Formation and Quarternary (alluvial) deposits were exposed in the area of the mines. The Raton Formation constitutes the bedrock of the area having a total thickness of 1200 to 1600 feet. Most of the formation consists of very fine to medium grained sandstone interbedded with siltstone and shale. Coal to be mined at the New Elk and Golden Eagle is located near the middle of the Raton Formation. The outcrop of the formation in the area may be characterized as stream deposits including channel-point bar faces, floodplain deposits and swamp deposits . Alluvial deposits along the Purgatoire River are complex. The headwaters of the river are underlain by volcanic rocks and sediments . As it flows to the east, the river cuts its way through many different geologic formations including Pleistocene glacial-fluvial sediments, foothills belt of Paleozoic-Mesozoic strata, terrestrial sediments of the Tertiary, and marine deposits of the Pierre Shale. Channel shape and structure of the Purgatoire also vary within each of these formations as does the water quality. A natural deterioration of water quality can be expected as the stream flows out of the igneous terrains , through sodic sediments , and into marine 10