A field testing program to provide data for mathematical modeling of ground water flow in the deep basalts of the Pasco Basin was initiated in FY 1978. Tests performed in DC-2 and water level responses in neighboring DC-1 suggest possible leakage between the three lower piezometers in DC-1 and indicate a downward gradient in the upper basalt layers down to 4000 ft, beneath which there may be an upward gradient. A sharp steepening of the downward gradient near the Umtanum Unit suggest that Umtanum may be acting as a barrier to vertical flow. Pressure testing in well DC-8 in the basalts above the Vantage sandstone at 1700 to 2700 ft indicate a downward gradient. Water level elevations were higher and downward gradients steeper than in wells DC-1/DC-2. Well DC-6 was artesian, with a production rate of about 17 gpm, with 75% of this flow coming from the depth interval 3650 to 3800 ft. Pressure tests between 2200 and 4300 ft indicate artesian conditions in every zone. Water level elevations in the Grande Ronde basalts in DC-6 were higher than in the same zones in DC-1/DC-2. As in DC-1/DC-2, there appears to be a local heat minimum within 600 ft belowmore » the bottom of the Umtanum with higher heads at greater depth. The Gable Mountain anticline may be a flow barrier separating Cold Creek Valley from the Columbia River Valley to the north and east. Recharge to the deep basalts in Cold Creek Valley appears small, with drainage occurring to the southeast, parallel to the Cold Creek syncline. The lowest head elevation in DC-2 was 360 ft, which indicates that the deep flow systems in this area may be discharging to the Columbia River, probably at or below the Tri-Cities area. Presence of tritium in DC-2 at 20% of the Columbia River value was still present after swabbing 64,000 gal of water from the packed-off zone. Recommendations are presented for a continued well drilling and testing program. (DLC)« less