In recounting Reclamation's venture into Marble Canyon, there are several factors that occur to me to investigate as I begin.
First: Although it could always be considered as a separate project, a dam in Marble was entangled with the idea of diverting water from that stretch through an immense tunnel to drop into a power station at Kanab Creek. The best height and location in Marble for this combination was one important factor, even after the 1949 decision by Interior to abandon investigations of the tunnel, since the idea was too strong a temptation for dam-dreamers to abandon.
Second, if the dam was to be built on its own, how far downstream and to what height could it be built to obtain adequate geology and optimum economic feasibility? This factor was complicated when the Arizona Power Authority decided to apply to the FPC for the Marble site Reclamation did not favor. As always, Reclamation was attuned to competing ideas, moving to block or co-opt them.
The third factor was that Marble's reservoir not interfere with Glen's operation, and indeed there would be the question of coordinated operations.
A fourth might have been the impact on the Park downstream. This was certainly controlling in the decision to shelve Kanab tunnel, as I have written; were there explicit worries about Marble by itself? Overall, in impact on the Canyon, this would have been a monstrous intrusion, along the rims, down in the canyon, from the rise and fall of the reservoir, and the flows below it. It will be interesting to see if and when NPS and NGO Canyon defenders started asking questions and raising objections.
In earlier posts, I mentioned speculations in the 1920's-- LADWP's about a Kanab tunnel and La Rue's Redwall damsite at mile (below Lee's Ferry) 30 (he didnt like those just below that). One of the Arizona water factions ballyhooed a diversion from Marble east and south to the Verde. The debate over the location of a Glen Canyon dam also figured in, but all these took a back seat after Arizona and then Reclamation targeted Bridge from the late 1930's on.
The following paragraph is repeated from Oct 11:
In 1948, a check of mile 42.4 in Marble disclosed no conditions precluding construction, though the profile was not ideal. More serious steps began in Apr 1949, looking at access to the river in the mile 29-38 stretch, since river travel would not be feasible until late summer. A trail was considered, and then a tramway overlooking mile 30. April saw an "urgent" request for money to make investigations in Marble/Kanab to tie into power production studies for Glen. BIA and Navajo approval was secured, and DC approved funds in May.
Fall-winter 1949-50, work continued on a dirt road and cableway, and by September 1950, there was a draft report on six sites in the nine-mile stretch. The three not eliminated were at 33, 37.5, and 39 miles. The crew had drilled holes at 33-mile to check for shale, but there was none. So they recommended Denver staff to see if downstream sites could be eliminated, saving tramway move. Oct 1950, Larson in Phoenix said 39-mile offered financial advantages if Kanab were built. However the geology was inferior to 32.8. The 37.5 mile site was not quite as good as 32.8 and economics were worse with Kanab. [It could be asked, since Kanab investigations were abandoned over a year before, how he knew this.] Denver staff came and ruled out 37.5 mile, and while they were considerably dissatisfied with 39, did not eliminate it. It would be necessary to drill more deeply at 32.8, and trench into the abutment at 39, in order to correlate the Bright Angel beds with their shales. More geologists were needed. The DC office suggested there be a press release with a photo of the cableway going across the river at 32.8 as this is the "kind of spectacular and unusual operation that catches the imagination and dramatizes Reclamation's job in the public mind". [There was not, after all, much going on otherwise.]
The site at 32.8 is between Redwall Caven and Vaseys Paradise. 39.5 is in just another old straight stretch.
The field trip from Denver reported in November. First came its overall assessment: "The ultimate development …involves the construction of a dam… to back water to Glen… a power plant of small capacity at the dam, and a 43-mile tunnel from the dam to a large power plant located at the confluence of Kanab Creek and the Colorado River. An alternative but less desirable plan, would be to generate all of the power at the dam; this plan would eliminate the tunnel to Kanab Creek but would fail to utilize the full potential power head." The economic advantage of the lower site would be large. "A shorter tunnel would be required for the power development on Kanab Creek and a larger power development would be possible at the dam because of the higher head."
To get at the details, they were working at 32.8 on five rows of holes; about 30-40, one drillhole from the inner rim down the left abutment [acupunture treatment for the Grand Canyon]. The drift on the left was at 3000'; there would be another on the right. The canyon floor was flat with thin aluvium cover, and an inner gorge 45' deep x 45' wide. The Redwall is fully competent, and it is extremely improbable that significant reservoir leakage would result, even with the solution holes. The site at 39 mile is 100' wider, 20' higher. Muav appears in its abutments; buried gorge may be larger. Still improbable there would be serious leaks; Muav would be concreted over. A later check showed that the Bright Angel was 460' below the river.
In Feb-Mar 1951, both sites were found competent enough that the competition between them would require more drilling. In November, the cableway, and the drilling, were at 39.5. They had to climb down the wall to get the cable started The camp was in mile 41 canyon; they called it Spook because of weird noises. And had a rock fall one night that holed some tents.
Poking its nose in, LADWP wanted to visit the site. Further work showed the lower site with 30' more head, and a 1½-mile shorter tunnel. There was no inner gorge there, because the Muav is softer. The Denver inspectors found joints that would need attention; the rock tended to loosen during excavation. Five lines of 99 drill holes were being done, with a 60-100' drift. The damsite here would be much more costly and inferior geologically, though it is suitable. The choice will be how the dam fits into the overall project.
In early 1952, Reclamation was working on project designs. They were thinking of a run-of-the-river dam with no drawdown for power. The Kanab diversion would be made after upper Basin diversions were near allotment. The tunnel intake needed to be close to the dam to counter sediment, which would be done by sluicing, rapidly lowering the reservoir. There could be a minimum of 2000 sec-feet released through the Park, generating baseload power. Without the tunnel, there could be earlier utilization, more flow, and greater capacity. Silt could be a problem in 75-100 years. (Not clear if this is with Glen; the Paria silt trap was reported on in 1958.) Investigations were to end in May.
From a March report from the Regional Director to the Chief Engineer, here are the options they had formulated:
April 1952, a summary from Larson emphasized that one most important factor was tunnel length, 2.2 miles and $48 million less at the lower site. He editorialized that with the meagre info available, it could be either site. We, he said, are in complete ignorance, including NPS, and are seriously hampered in planning intelligently. Even in transmission, the network from Glen will depend on how Marble-Kanab works out. [What didnt they understand about "No!". It is their romantic dreams of "more head; more head" that is holding them up. Did they lose Marble because they dawdled over their monster tunnel, thus delaying until the events of the 1960's closed the Grand Canyon to them (almost) completely?] He went on: We cannot choose a damsite without knowing about Kanab, since lower site is not justified without tunnel. After all, the only effect on the Park would be a reduction in wide fluctuations and flow; Glen will produce clear water anyway. So far we are within limits set by Warne, but we think we can look at surface aspects of Kanab. So we urge Commissioner to talk to Secretary, allowing recon outside Park without drilling.
And so, there is, January 1953, "Field trip report on recon of Kanab power plant site, Marble Canyon Project" by a geologist and an engineer, who went there in Sept 1952. "Necessary" to secure info in order to make sound comparisons between Marble damsites. "This is the major portion of the entire project". Before, there were flights without on-ground survey; the need is to look at physical conditions at tunnel outlet. The investigators assumed a tunnel flow of 10,000 sec-ft. for 36 miles to somewhere between Tapeats and Kanab. There would be a small reservoir or chamber for surge control, penstocks and power plant to handle drop of 940' [small wonder they could not keep their minds off]. There was a 3-mile difference in the four possible tunnels from the two damsites. There could be one alignment with an angle point on a Tapeats tributary, just west of Crazy Jug Point. This would allow an adit instead of a costly vertical shaft, and permit free draining, since Thunder River indicates that underground water conditions will be an important factor. (I think what he meant was that the limestones of the Kaibab Plateau were full of holes, tubes, and tunnels of their own, and would drain water into the tunnel.) Original idea was to have outlet at Kanab mouth. Problems were silt encroachment at head of Bridge's reservoir at Kanab and avoiding Bright Angel shales. So, three other plans were checked. The first had the tunnel under Deer, then coming out into the dry lake, due to a giant slide, which may be unstable, so not geologically suitable. Second idea was to carry the tunnel to next side canyon behind a dam for surge capacity. From there, penstocks would carry water to river at 138.5. This would require a lot of excavation. Third plan would take tunnel to Fishtail Canyon. They couldnt visit because of ruggedness, but it would not seem a better location than the other two. While in the field, they looked at the idea of having the outlet in Deer Creek, with a dam two miles from river at 3140' elevation. The spillway would go down the creek, with a pressure tunnel southwst to the power plant just upstream from the side canyon in the second idea. Good damsite, spillway away from power plant, and the geology is good. There could be a road from Big Saddle to the upper rim and down. Access through Redwall would be a problem. Maybe follow the present trail, and new road into Tapeats. Obstacles here are more or less normal. [So much for abandonment.]
A year later, in June 1953, the Chief Engineer had determined that 39.5 did not look economically feasible; too costly. We have therefore done drawings for two 32.8 options: concrete arch using four generators without tunnel, and concrete gravity using one with. He doubted that the saving in tunnel mileage was worth the extra cost of the downstream dam. Also we prefer curve for spillway tunnel, and 39.5 is straight; also Muav is less desirable. The three grades of rock have varying strengths and may set up undesirable differential abutment deformations. Also, the joints on the left form a thick slab that is a potential hazard. Region agreed the cost difference eliminated the lower site, then added that if Kanab was feasible, we want to re-evaluate.
In January 1954, NPS' Tillotson queried Reclamation about figures FPC had on Marble-Kanab. Reclamation said it was all the FPC's work; Reclamation had confined itself to Marble dam. But in October, the FPC wrote the Region: "you furnished us information on costs for the potential Kanab development." Can you bring us up to date? But Reclamation replied it was only looking at a dam, and was now working on access, a major item. In 1955, Reclamation was considering an inclined railway instead of a highway.
In 1957, NPS put forward a bill to adjust the Park's boundaries, including adding the lower end of Kanab. Reclamation objected. When asked why, if Kanab tunnel had been abandoned, Reclamation replied it was not completely dropped.
The Paria silt trap was being studied, being considered worthwhile to prevent encroachment on Glen. In 1957 it was decided that catching silt on the Paria was enough like the problem of the Little Colorado that drilling was not necessary. Concrete materials could be found just below Buckskin. [A good example of collateral loss: no Paria or Buckskin Gulch backpacks.] In the design for the 32.8 site, the arch dam would be on top of a gravity plug of the submerged inner gorge. September 1957, plans were completed for Marble with 336 mw capacity and a 328' dam in the Paria. Marble access would be an inclined railway. All energy would be firm, integrated with the area's steam generation, and sent to Parker-Davis. In 1958, studies of Glen's operation led them to raise Marble to 375 mw.
In September, Arizona's engineering consultants, Harza, were asking for information on Marble, a sign that Reclamation was about to lose sole control over Marble planning. At this point, NPS said that the recreation potential was not significant due to limited water access. In 1957-8, NPS opined--internally--that maybe Arizona's dams would be better because they would not intrude on the Park as much; the Canyon would continue to have values, and recreation would increase.
Sep 1957, Reclamation asked BLM to issue a first form reclamation withdrawal of Marble Canyon lands west of the Navajo Reservation, north of river mile 40. PLO 1909 did that two years later. The oddity of this is that it did not affect FPC jurisdiction, in place from the 1910's power withdrawals: 446, 447, 743, WP7. Nor did it affect any other agency, or give Reclamation any power to do more than investigate.
In 1958, the Bureau of Sport Fisheries thought there could be a "much-needed" tailwater trout fishery with more access, half-way and on both sides of the dam [more collateral development]. Later, the state Game & Fish Dep't got very enthused about Marble, a reservoir with "not just ordinary water, but clear and cool". Many would be attracted to this unique trout lake, and want to travel through the tunnel to the dam. Bridge would have both warm water and trout fisheries; most unusual. If the water releases were low enough, the entire Grand Canyon could be a trout stream. Elevators at the dams could help pay off costs of state-built dams. At Bridge, there could be one-way trips from dam downstream. Traffic is now double what NPS estimated in 1947. Over 85,000 visitors a year will use Diamond Creek. Access below Marble dam was inadvisable because of "dangerous rapids and lack of access before Phantom".
Reclamation's draft report on Marble dam at mile 32.8 was complete in February 1959. However, there was now the annoyance of the Arizona plan to build a state dam, which was being developed for 39.5. So Reclamation withheld its report. It was also keeping quiet about the concept of a development fund for the Lower Basin (the Upper had such an account, to be powered by Glen's revenues). And then, in November 1960, the monster came back.
Source: Bureau of Reclamation files; Region 3, Boulder City