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<br />Regional ground water flow from the west is along the coal seams, <br />discharging into Maitland Arroyo. Thus, the underground workings act as drainage <br />conduits, directing ground water into the arroyo alluvium. During the wetter <br />months, water flows increase in the Maitland alluvium, and the watertable rises. <br />When the hydraulic head is higher in the alluvium than in the workings, the reverse <br />would occur, whereby some surface water would seep into the coal seams and into <br />the underground workings. Thus, the underground workings would also act as large <br />storage reservoirs. <br />The rate of discharge into or out of the arroyo alluvium is controlled <br />primarily by coal permeability and hydraulic gradients. At the time that <br />piezometers were installed, water levels in the underground workings were higher <br />than in the bedrock near the arroyo as indicated by the water levels at Site W82-10 <br />(6237 feet). Water levels in the workings of the Champion and Maitland No. 2 <br />Mines were at 6241.8 feet (W82-12L) and 6240.8 feet (W82-9R), respectively. <br />• Hydro~eological Sector II <br />Sector II is bounded by Maitland Arroyo to the south and by a fault to <br />the northwest. This sector is partially dissected by a dike which intersects the <br />fault in the west central portion of the permit area. <br />Water levels in Sector II indicate an intersection between bedrock <br />ground water and Maitland Arroyo exists similar to that in Sector I. However, only <br />limited mining has taken place in the Lower Robinson Seam of Sector II. Variations <br />in static water levels for the various wells indicate the increased length of time <br />these units require to reach equilibrium with the water level in the alluvium <br />beneath Maitland Arroyo. The water level in the Lower Robinson seam under- <br />ground workings, however, is the same throughout Sector II due to mining through <br />the dike. <br />• <br />-9- <br />