Geological Survey Water-Supply Paper 1475-K Ground-Water Reconnaissance at Pinnacles National Monument, California

Test well T16S/R7E—35R1 was drilled on the west bank of Chalone Creek at an altitude of about 1,020 feet. The following well log is the lithologic description of the drill cuttings and the chronologic record of the development and pumping test of well 35R1.

July 9:

Started drilling (11:30 a.m.). 9-5/8 in. rotary hole. Drilling fluid consists of bentonite and lime.

July 10:

Stopped drilling (5:30 p.m.).

July 13:

Fluid level 9.5 ft. below land-surface datum. Cleaned hole to 41 ft., set 41 ft. 7 in. of heavy-duty casing, 8 in. I.D., with 1 ft. 6 in. above ground surface. Bottom 21 ft. of casing perforated with torch cuts: 6-8 in. long, 4-6 in. apart, 4 cuts around.

July 14:

Kelly lowered with packer at top of casing. Clear water pumped through casing into bore to wash out drilling mud; 5-1/2 tanks or about 2,500 gallons failed to clear well of drilling mud. Bailed about 130 bailers (14 to 25 gallons each) for a total of about 2,600 gallons and well still failed to clear.

July 15:

Depth to water 9.30 ft. below land-surface datum. Set test pump. Pumped at rates of 5 to 60 gpm, broke suction at 37 ft. whenever pumping rate exceeded 7-1/2 gpm. Pumped about 10 hours or more. Depth to water level outside casing 17 ft. when water inside casing was at 35 ft. Small amount of water moving through perforations. Failed to clear. Water has sulfur odor.

July 16:

Depth to water 9.25 ft. below land-surface datum. Pulled casing 5.35 ft. and 5.0 ft. cut off. Top casing now 1.85 ft. above land-surface datum, and uppermost perforation at 13.75 ft. below land-surface datum. Pumped from 9:20 a.m. to July 17 at 4:00 a.m.—about 19 hours—at rates from 12 to 30 gpm. Failed to clear.

July 17:

7:30 a.m. Depth to water 9.06 ft. below land-surface datum. Alternating pumping and surging. Attempted pumping and simultaneous jetting between casing and bore with no observed improvement. Rigged up leather gasket and and swabbed for about an hour. Pumped 2 hours from 6:00 p.m. to 8:00 p.m. Water clear at 8:00 p.m.

July 20:

Depth to water 9.03 ft. below land-surface datum, 10.88 ft. below top of casing (measuring point). Started pump at 12:00 noon, pumping 7.5 to 9.5 gpm until 2:45 p.m., pumping level reached 13.40 ft. below measuring point. Increased rate to 13 gpm until 4:00 p.m., pumping level reached 14.05 ft. below measuring point. Averaged about 17 gpm until 7:50 p.m., pumping level reached 20.05 ft. below measuring point.

July 21:

Pumped at 10 to 15 gpm until 1:58 a.m.; pumping level ±19 ft. Pump stupped for 2 minutes; 2:00 a.m. to 3:00 a.m. pumped about 20 gpm to reach maximum pumping level of 28 ft. below measuring point. Pumped 13.6 gpm from 3:15 a.m. to 5:10 a.m. At maximum pumping level of 28 ft. below measuring point. Water level 17.10 ft. below measuring point outside casing and 28.0 ft. inside casing.

Pump stopped 5:10 a.m., water level recovered to 12.00 ft. below measuring point at 6:00 a.m. Pump started 6:04 a.m., rate varied from 9 to 13 gpm until 10:27 a.m. when rate was reasonably stabilized at 11.5 gpm. Pumped until 7:00 p.m. with maximum pumping level at 14.90 ft. below measuring point. Pump off 7:00 p.m. Water level 11.23 ft. below measuring point at 8:00 p.m.

July 22:

Depth to water 11.00 ft. at 7:45a.m. Cement placed at 29 ft.