Summary of drilling log and pumping test for Pulana Well 9-10 Pulana, Puna, Hawaii

Abstract

Location and Description Pulama Well 9-10, drilled under the State's exploratory well drilling program, is situated four miles west of Kalapana Black Sand Beach in the Puna District of the "Big Island". The well lies 1.8 miles inland from the coast at an elevation of 230 feet and its total depth of 250 feet extends 20 feet below sea level. Eight-inch casing is set to the total depth with the bottom 21.7 feet perforated. Geology and Hydrology Pulama Well, the first to be drilled in the southern portion of the Puna District, encountered highly permeable basalt flows of the Puna volcanic series which erupted from the Puna rift zone about 4 miles mauka. Based on the driller's log, the formations penetrated are predominantly "hard" to "medium hard gray rock" intercalated with "soft" to "very hard" zones. The aquifer rocks consist of "cinders" and "clinkers" reported between the 233-foot and 250-foot depths. Several faults roughly parallel to the east-west trending Puna rift zone have been mapped in the Pulama area. The abrupt change in slope immediately mauka of the well can be followed for several miles and is believed to be a fault scarp buried by subsequent lava flows. Other parallel faults have been mapped near the coast. It is not known what effect, if any, the structural geology of the area has on the aquifer system. However, no hydrologic boundary conditions are indicated by the pumping test data. Annual rainfall averages about 75 inches at the well site and increases with elevation to over 100 inches along the rift zone; four mile distant. Although a rainfall belt of this magnitude could be expected to provide sufficient recharge to maintain a fresh water lens, Pulama Well has a chloride content of about 300 ppm and is sensitive to changes in chlorides under pumping conditions. An extremely permeable aquifer and structural geology may be influencing factors of the anomalous situation. Temperature of the well water is slightly above normal at 78.5 degrees Fahrenheit. Pumping Test Results Pulama Well 9-10 was pump tested for 73 1/2 hours with a turbine pump driven by a 165 HP diesel engine from 11:25 a.m. on December 3 to 1:00 p.m. on December 6, 1963. The well was pumped at rates of 50 and 100 gpm during the first 24 hours and at 50 gpm for the next 42 hours. Five additional hours of pumping were at step-up rates of 100, 200, 300, and 450 gpm with a maximum drawdown of 0.14 feet. Chlorides of the pumped water increased from an initial 278 ppm to 307 ppm while pumping at a rate of 100 gpm. On reducing the pumping rate to 50 gpm, the chlorides stabilized in a range of 293 to 298 ppm. Pumping the well at a maximum rate of 450 gpm with only 0.1 foot drawdown,the chlorides rose to 346 ppm, an increase of 150 ppm in 5 hours. Results of the pumping test indicate these salient points: the aquifer is extremely permeable, the well is capable of yielding 50 gpm of water with chlorides stabilized at about 300 ppm, the water level in the well under pumping conditions fluctuate with a periodicity closely resembling the ocean tides, and while pumping at a rate of 50 gpm, the chlorides of the pumped water fluctuates about 5 ppm.