Descriptions of Springs, Part 1

The following is a list of those springs which show activity of interest. Not being included in this list does not imply that the spring showed no activity during the period of the report. There are several small seeps north of Map 2 which flowed continuously except when dormant due to the activity in Well 28-32.

#1—Geyser

A set of three openings located immediately next to one of the access roads. The westernmost is the largest, about 61cm x 25cm. Located 1.6m to the east is a second opening, 38cm x 13cm, while the third located 56cm farther east and the smallest, 13cm x 30cm, and was stained yellow from sulfur. On several occasions tire tracks were observed running right through this spring.

On 28 December 1985 the eastern most vent was observed to be overflowing and continuously erupting about 10-15cm high. On 23 February 1986 the activity and overflow had shifted to the western vent, which was only bubbling heavily with occasional splashes breaking the surface.

#2—Flowing Spring

A small opening with a broad shallow pool about one meter across, filled with long filamentous bacteria and algae. It was observed overflowing throughout 1984. A change was not noted until late April 1986, when in response to tests in Well 28-32, overflow ceased. Two weeks later it was completely dry.

#3—Flowing Spring

This spring appears similar to #2. Overflow from this spring decreased in May 1986. It was still overflowing slightly in June 1987. By September 1987 it had ceased flowing and was dry.

#4—Non-flowing Spring

This spring is a circular vent about 1.75m in diameter, and only about 1m deep. Because of its location at the base of the southern end of the Terrace, thunderstorms have washed considerable gravel into the western end. Vandals have also contributed a number of large rocks. In 1984 an attempt to clean this spring by members of the Sierra Club, the Bureau of Land Management and GOSA did cause the temperature to be raised from 170°F [77°C] to 203°F [95°C] (approximately boiling for the altitude of the Main Terrace).

In response to the drilling tests at Well 28-32, this spring drained in late April 1986. In early June it was one of the first springs to show signs of recovery, and by the end of that month it was completely full and even showing signs of a slight trickle of overflow. In May 1987 it was again drained by Well 28-32.

#5—Flowing Spring

Until it went dormant due to the powerplant, this was an algae filled spring that quietly overflowed. It appeared similar to #2 and #2nw.

#6—Intermittent Spring

A circular vent about 1.25m across and at least two meters deep heavily stained with black iron sulfides. Like #4, this spring was cleaned in 1984. Several hundred pounds of rocks, cans and pipes were removed. The lowest spring of the Main Terrace proper, it is usually at or near boiling. The water level fluctuates about 2cm, and when high enough, a small trickle of water flows from a notch in the east side.

This activity was the norm until April 1986, when it dropped in response to activity in Well 28-32. By mid June, the water level had dropped about 45cm, while the temperature rose from 92°C to 95°C. By September, the water had risen back to overflow, with the temperature dropping to 93°C.

In May 1987, once again in response to activity in Well 28-32, the water level dropped about 50cm. The water level continued to drop, so that by March 1988, the water was down at least two meters.

#7

An irregularly shaped vent about 2.5m long that is almost certainly connected to #6. Usually water stands about a foot below the rim. When #6 was pumped out in an attempt to clean it, water dropped in this spring.

#8—Flowing Spring

This is a small cone with a squarish vent about 28cm x 36cm across at the top. The water would stand just below the rim and the temperature was consistently between 180°F [82°C] and 184°F [84°C]. A small amount of bubbling was observed, while a trickle of discharge escaped through a small opening to the north. In September 1985 it was cleaned down to a depth of about 1 meter.

This spring was the last one to be affected by the geothermal power plant. In May 1987, when all other springs were dry, or nearly so, this spring still discharged a trickle. By December 1987, however, it too had dropped. Later it was reported that whenever the plantŐs wells were in operation, this spring dropped, while it would, in contrast, rise in response to a shutdown in operation.

#8nw—Non-flowing Spring

This is a rectangular shaped cone about 1/2 meter high, with an opening at the top about 76cm x 53cm. Until the autumn of 1985, this spring was filled to within 10cm of the rim with debris. A thermal cleanup effort removed several hundred kilograms of debris. After this effort, the vent was about three meters deep, and filled with boiling water. It may be connected to several seeps located to the west of it which dried up during the pumping operations [Knight and Strasser 1988].

#10—Geyser

In [White 1968], this spring is referred to as a “gassy geyser” that overflowed intermittently. Most observed eruptions were little more than heavy overflow and boiling, but on occasions it was observed to throw water as much as one meter high. The activity varied considerably, with intervals ranging from about 15minutes to several hours. The durations were about one-half to two minutes.

During 1984 the intervals were several hours long, and the duration was only about 30seconds. This was also the case until the Summer of 1985, as while eruptions and wet runoff were observed, no intervals were recorded.

#11—Flowing Spring

A small opening with a heavy deposit of yellow sulfur. It bubbles occasionally, but the temperature has never been measured above 40°C. It is probably connected underground with #10, as it dried up when #10 was pumped down for cleanup.

#12—Geyser

This spring was reported by [White 1967] to have erupted as high as 25ft (7.6m). Several attempts were made to induce activity, but none were successful. Eruptive activity as high as 40cm has been observed from several of its vents. In addition, the water level fluctuated about 3cm.

During a visit of several hours, it was not unusual to note that this spring was overflowing, only to find it down about 2cm later. Or the reverse might be observed, with the spring below overflow, only to be seen overflowing later that day. Along with this fluctuation, the eruptive activity would start or cease. Sometimes the eruptions would take place during overflow, sometimes during the ebb.

#12sw—Flowing Spring

An opening about 30cm by 61cm and about 30cm deep with a slight yellow stain. The temperature was usually about 70°C. It is connected with #42 and #42w, as it would slowly drop after repeated eruptions of those geysers.

#13—Non-flowing Spring

This is a low cone about 20cm high with a circular opening about 50cm in diameter. It is at least one meter deep. It is described in [White 1967] as being a geyser with eruptions as high as four meters, as well as exhibiting a relationship with the activity of #12.

The water level was usually about 30cm below the rim, and although the temperature was at or near boiling (200°F [93°C] to 204°F [95°C]), all attempts to induce it failed. On one occasion a rock the size of a basketball was removed.

#14w—Intermittent Spring

This spring is a shallow, circular opening about 50cm in diameter on a shallow slope. Usually water was not observed in this shallow vent. The area downslope from the vent is a barren, gray-stained area washed clean of sinter gravel, indicating some sort of activity in the past. On 08 February 1986, the only instance of activity was observed, consisting of a quiet overflow which lasted about 35-45 minutes.

#15, #15w, #16, #16se—Geyser(s)

These springs are discussed as one, as they are located near each other. #15 is a circular opening about about 30cm across, which overflowed downslope to the east. #15w is three narrow cracks, with overflow to the east from the end of the southernmost opening. #16 is a long, wide crack only a few centimeters deep except at the north end. There it opens into a deep cavern. Located about 1.5m from this is #16se, a 10cm opening into this cavern.

In November 1983, #15w was observed to be erupting continuously about 1m from two vents. The water from each vent was ejected toward the other so that the spray intersected. A thin coating of brilliant white sinter was being deposited over an older, nearly black layer. A colorful algae mat of reds and oranges enhanced the scene. A few weeks later this activity had ended, causing the drying of the algae mat, and the dulling of the sinter.

This group was first observed to cease all overflow on 26 April 1986, when they had dropped about 1cm in response to tests in Well 28-32. This drop continued, so that on 09 May 1986 they were down about 14cm. After venting ceased, the group recovered, and was observed to only be about 2cm below overflow on 04 Jun 1986.

Through the winter, this group overflowed, and was not noted to change until production began at the Steamboat Hills power plant. On 02 May 1987, the group was down about 8cm, and was completely dry on 28 June 1987.

#19n—Perpetual Spouter

This spring was never observed to change, except at the times of terrace-wide drainage by the operation of the Well 28-32 and Steamboat Hills power plant. When active, it was a small, shallow pool about 1/2m across which splashed about 10cm high. The outflow channel, like #2, was lined with thick, white filaments over a darker algae.