Cadillac Desert_ The American West and Its Disappearing Water - Marc Reisner [257]
Ruckel had wanted to introduce testimony from Shirley Pytlak, a professional geologist who had worked briefly on the Teton project during the summer of 1973, drilling test holes at the damsite and injecting water into them. The idea was to see how fast the holes filled up, which would allow the Bureau to gauge—“guess” is a better word—the extent to which the surrounding rock was fissured and fractured and concomitantly leak-prone. For weeks, Pytlak said, the boreholes had been pumped with water at a rate of three hundred gallons per minute, which was like sticking a fire hose in them and turning it on full-blast. The holes never filled. If test holes leaked at such a rate, Pytlak asked her superiors, how much water would seep out of the reservoir and try to get around the dam?
Actually, none of this should have come as a surprise. Three years earlier, the Bureau had conducted a similar test-drilling program, and three deep holes—numbers 301, 302, and 303—turned out to be particularly thirsty. Injected with as much as 440 gallons of water per minute, all of them refused to fill. The three holes were all drilled in the right canyon wall. Number 303 was only 250 feet from what would be the dam’s embankment. Clifford Okeson, the Bureau’s regional geologist and the person supervising the drilling program, reported to his superiors: “The three deep drill holes which were completed on the right abutment of Teton Dam during 1970 encountered cracks capable of transmitting much more water than the cracks encountered in previous drill holes.” This led Okeson to conclude that some reservoir leakage was inevitable. “Probably some of the reservoir water will leak around the ends of the dam, through cracks in the bedrock, and emerge from cracks at lower elevations of the bedrock surface downstream from the dam. The water would be under artesian pressure so it would gradually wet the thick cover of soil, thus turning [it] into a loblolly or quagmire. Loblolly conditions could also develop in places within the impervious section of the dam if one or more cracks is poorly grouted” (emphasis addedd).
Although he was loath to say so—using an adjective like “serious” is regarded by some engineers as unwarranted emotionalism—loblolly conditions inside the dam would be a serious occurrence, one under which the dam could conceivably be lost. The key to preventing them was proper grouting. Grouting, a commonly used technique in the dam builders’ art, involves injecting liquid concrete under high pressure into drill holes in the abutment walls on either or both sides of a dam; the concrete moves like water, filling all the fissures, shear zones, and holes, and then hardens, leaving a supposedly impervious barrier against seepage. The plan at Teton was essentially the same as at Fontenelle—several grout curtains would be extended outward from the site, into the abutments, to block any flow of water trying to move around the dam. The grouting might be done improperly under three sets of conditions: if the engineers were inexperienced or otherwise incompetent; if the rock was so hopelessly fractured and fissured that a near-perfect job of grouting was impossible; or if the canyon wall surprised the engineers by taking so much more grout than expected that, at some point, they declared the job done and quit.
In 1969, the year before the water-injection tests, the Bureau had taken the rather unusual step of performing a test-grouting program, so unsure was it of the conditions at the Teton site. Holes were drilled in the rock, and grout was