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are upgradient from the Musgrave well, they can be expected to represent the quality of any leachate that would reach the Musgrave well. The Musgrave well sample matches the leachate quality of Trapper's GD-3 well in Trapper's backfilled Den•inger pit. The GD-3 well is about ].5 miles southeast of the Musgrave well. The Musgrave well is not in the ground water flow path of the Derringer pit because the pit is outside the area underlain by the 3`a White Sandstone, the well's perforated unit. Hydraulic connection between Trapper's spoil leachate and Musgrave well -Trapper's pit nearest the Musgrave well is the Browning pit, about one-half mile southeast of the Musgrave well. The 3`a White Sandstone was removed during excavation of the pit. The pit was backfilled with coal spoil in the late 1980s. Spoil now abuts the 3`a White Sandstone in the low-wall of the pit. Degradation to the Musgrave well could have resulted if rainwater and snowmelt infiltrated from the ground surface down into the buried spoil in the Browning pit, and from there flowed downdip through the 3`a White Sandstone to the Musgrave well. It would have taken about 10 years for this spoil leachate to flow from the Browning pit to the Musgrave well if the flow velocity was on the order of 0.7 ft per day. This velocity is reasonable based on porosity of the 3`a White Sandstone and the local hydraulic gradient. Many individual sandstone beds in the 3`a White have azound 10% total porosity on a bulk density log From Trapper's GD-1(2) well, indicating effective porosity of, perhaps, half as much. Hydraulic conductivity on the order of 0.04 fl/day may be reasonable for 5% porosity, based on core data from the Williams Fork Formation at the Seneca Mine (USGS Water-Resources Investigation Report 92-4187). Trapper's potentiometric surface map for the 3`a White in the 2001 annual report shows a hydraulic gradient of about 5 vertical feet per 100 horizontal feet. Comparison of sample results with natural water quality in 3rd White Sandstone - Trappermonitors the natural quality of the 3`a White Sandstone in four wells on the mine. ("Natural" as used here denotes no influence from mining.) Although none of the wells aze upgradient from the Musgrave well, they can be expected to represent the natural water quality of the 3`a White Sandstone at the Musgrave well. The Musgrave well sample matches the natural water quality in the 3`a White Sandstone of Trapper's GP-9 and GC-2 wells. These wells are located at the east end of the Trapper Mine, approximately 5.5 miles east of the Musgrave well. Leachate versus natural conditions as a cause of Musgrave well water degradation - The Musgrave sample matches Trapper's spoil leachate composition, and a mechanism exists by which the leachate could have reached the Musgrave well (flow through the 3`a White Sandstone). The Musgrave sample also matches the natural ground water composition in the 3`a White Sandstone, and a mechanism exists by which the natural ground water could have reached the Musgrave well (the well is completed in the sandstone). The evidence for the cause of the change in Musgrave well water quality is equally compelling for both leachate and natural ground water. The attached Piper plot shows the similarities in composition among the samples. The samples from Trapper'well were taken in October 2001. One of Trapper's four spoil wells, P-8, is not included in the Piper plot because it may have infiltration from the ground surface.