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-3- • wells were drilled with a 7-7/8 inch bit and completed with 2-3/8 inch O.D. PVC casing and machine slot screen (.010 inch slot size). All screened intervals were gravel packed with 10-20 sieve size silica sand. A seal of bentonite pellets was placed above the gravel pack. The wells were developed with air and by pumping for one to three hours each. The maximum yield obtained from any well was approximately 5 gpm. None of the wells were pumping clear water at the end of development. The permanent wells, YAW-1, YAW-2, YAW-3, YAW-5 and YAW-6 will have cement collars and steel casing with locking caps installed around them. The remaining wells will be abandoned in accordance with the approved plan. Hydrogeology In the wells drilled in March 1982, the thickness of the alluvium ranged from 10 to 18 feet. The depth to water ranged from 1 to 9 feet yielding a saturated thickness of approximately 5 to 10 feet. Cross-section A-A' shows that the bedrock surface under the Big Bottom area is relatively flat and lacking significant buried channel features. Oue to access problems from wet ground conditions, the pumping test of well YAW-5 has not yet been performed. However, wells YAW-2, YAW-3, YAW-4, YAW-6 and YAW-7 were slug tested. The slug tests were performed on 16 March 1982. The tests were performed in the same manner as the Williams Fork . slug tests. The results of the slug testing are presented on Table 2. Where the data did not appear to be in accordance with what the theory would ( indicate for a particular method, the results of that method were not used. The permeabilities individual wells obtained from this testing ranged from 26 to 280 gpd/ft2 and averaged 120 gpd/ft2. The calculated transmissivities ranged from 200 to 1900 gpd/ft and averaged 900 gpd/f t. These permeabilities are higher than those found in the Williams Fork alluvium; however, the Yampa River alluvium is less clayey. Therefore, the calculated permeabilities and transmissivities seem reasonable. Summar The Yampa River alluvium in the Big Bottom area is 10 to 18 feet thick consisting mainly of poorly sorted silty sand to cobble sized materials overlain by sandy silt. The saturated thickness was approximately 5 to 10 feet in March 1982. The permeability and transmissivity calculated from slug test data averaged 120 gpd/f t2 and 900 gpd/ft respectively.