Following a Reclamation-NPS conference on Bridge's effect in November 1942, Olmsted reported to Drury, Jan 43, on the effects from two sites with a range of elevations: a lower Gneiss from 1772' up to 1835', and an upper from 1919' to 1970'. Based on Reclamation's own work, Debler had concluded lower Gneiss was better, and told the Commissioner that 1835-40' was the preferred height. Commissioner Page and Director Drury then talked it over, after which Page concluded, and told his Chief Engineer, that unless the advantage of a dam above 1772' was "very material", the invasion could be accomplished only with great difficulty. He doubted plans would contemplate a dam that put water into the Park, even though many thought invasion would not be detrimental. Contrarily, in February, the Chief Engineer recommended using the lower Gneiss site, to 1840', about three miles below Kanab Creek. Since NPS was not averse to development in the Monument, he suggested adding the affected Park to GCNM. The high-water debris would be below Havasu, and the reservoir would be full, mostly.
NPS also reported on possible camping sites and road access. Necessarily there would be extensive scarring, and more if aggregate were taken above the dam and dropped into place.
A January Reclamation report is in the archives with photos of the drifts showing what was done, up to as high as 1575'. The site to obtain the aggregate was on the south rim at the lower Gneiss site; easy to get at and almost pure limestone. Redwall not accessible.
To gather the materials necessary for the construction plan, the Kingman office was closed, concentrating office work in Denver . All field work was finished in February, with barges and tools released by March. The spillway specifications were down-sized because of the likelihood of upstream reservoirs. Calculations were being carried out to look for the best economic height. Sep 43, Debler told Olmsted that if the maximum elevation is below 1843', there will be an economic loss.
LADWP asked, with high urgency, for data, and received it. Debler used LA interest to press for a commitment by Interior to ask Congress to change the Park boundaries, making economics the foremost value. Geologist's report showed all sites excellent; upper Gneiss the best.
Oct 43, McKee made his report, but it is far more visionary than just the geology, the type of report that should have been made before making a Park. He visited Diamond Creek, below Toroweap, the Havasu mouth, and took a boat trip down from there to Bridge. He noted that the youngest strata at river level, after Marble's introduction, were around Havasu. He was impressed by the vast volcanics and the widened stretch along the Hurricane fault. He corroborated the fact that the Canyon was deepest here. The Cambrian record is remarkable for its completeness, and cannot be duplicated, although the greatest loss would be the lavas and ancient sediments. He dismissed the archeology and biology as not unique, and could be recorded before drowning. (Pooh! these geologists.) The Havasu area had striking scenery, but not great geology. He wrote that he was worried more about indirect effects and thought that sediment would mess up any development. He made the mistake of wanting to start the Grand Canyon where it widens at Nankoweap, as if a digestive tract did not include the mouth and esophagus. Called the Canyon a physiographic whole, even though there are differences. (I call it a topographic, geographic, geologic, educational, scientific, environmental, cultural, and ethical entity. That's how the 1975 GCNP Act defined it, and how could Congress be wrong?)
McKee's fine conclusion : It is not possible to say one part is inferior or superior; each is different, great, and part of the entirety. Remove one part and you lower the value of it all, exposing it to commercialization, exploitation, and misuse by private interests. He preferred that the Canyon be administered as an entity by NPS. Encroachments have been made, but kept to minimum, the vast remainder can be kept in the best interests of conservation. We should not dismember the developed parts.
Upon receipt, Director Drury sought more advice as to whether to try to keep encroachment below Havasu.