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~- Ir1TRODUCrIOrI • Mining of the F seam at Atlantic Richfield's (ARCO) t1t. Gunnison t•tine will result in a certain amount of subsidence and fracturing of over- burden units. inflow of water into the mine may result if hydrologic connection with surface water or the limited overburden aquifers results from subsidence and fracturing of the overburden. However, in operating this project, ARCO is committed to protecting valid water right interests from any negative impacts of mining on water supply. Furthermore, ARCO is committed to protecting its mining operations from the•hegativ~ impacts of increased min= water..infiows: It must be pointed out that any unusual water inflow into the tot. Gunnison f4ine represents a "nuisance" to the operations. Atlantic Richfield will take every precaution to insure. that water does not enter the mine. needlessly. A map shoving watershed areas and associated streams, reservoirs and ditches is provided in Exhibit 1. The areas under which mining will • occur are shown as single cross-hatched (areas tributary to the FJorth Fork), shaded (areas tributary to r4innesota Creek) and double cross- hatched (example of 50~ extraction safety zone fora perennial stream). Table 1 lists the acreages of each basin under which mining will take place. Baseline studies indicate that flow originating within the lease area is in direct response to sno~~rtnelt and precipitation events. Streams originating primarily on the lease area, Sylvester Gulch, Lone Pine Gulch, Dry Fork of flinnesota Creek and Lick Creek are all ephemeral. Horse Creek and South Prong of t9innesota Creek are perennial but their source originates outside the lease block at higher elevations on Mt. Gunnison. All of these streams, with the exception of Sylvester Gulch and Lone Pine Gulch, are tributary to 14innesota Creek. Sylvester and Lone Pine Gulches are tributary to the Morth Fork of ttie Gunnison River. (I)