Horseshoe Dam, Across the Verde River approximately 58 miles northeast of Phoenix and 40 miles north of the confluence of the Verde and Salt Rivers, Rio Verde

Source document Quoted word for word from HAER AZ-24. Not written, edited or summarised by this site.

Across the Verde River approximately 58 miles northeast of Phoenix and 40 miles north of the confluence of the Verde and Salt Rivers, Maricopa County, Arizona Horseshoe Dam is at latitude: longitude: The point represents the west end of the dam. It was located on April 14, using Google Earth. There is no restriction on the release of its location. Date of Construction: Outlet Tunnel: Dam and Spillway: Spillway Gates: Engineers: Dam and Spillway: Leeds, Hill, Barnard and Jewett Spillway Gates: Leeds, Hill and Jewett Builders: Outlet Tunnel: Langdon and Company, Minneapolis, Minnesota; Douglas Grant and Company, Faribault, Minnesota; Vinson and Pringle Company, Phoenix, Arizona Dam and Spillway: Arundel Corporation and L.E. Dixon Company, Baltimore, Maryland

Source document Quoted word for word from HAER AZ-24. Not written, edited or summarised by this site.

A major component of the Salt River Project s water supply system, Horseshoe Dam was completed in as part of the industrial production effort for strategic materials in World War II. Although administered by the Salt River Valley Water Users Association, the dam s construction was funded by the Phelps Dodge Copper Company and the U.S. Defense Plant Corporation. It functioned as a means to increase the Phoenix region s water supply in exchange for water delivered to the Morenci copper mine in eastern Arizona. The structure is technologically significant as the first major earth- and rockfill dam built as part of the Salt River Project. HORSESHOE DAM HAER No. AZ-24 (Page 2) Report assembled by: Donald C. Jackson and Clayton B. Fraser Research assistance by Richard E.

FRASERdesign Loveland, Colorado December

Source document Quoted word for word from HAER AZ-24. Not written, edited or summarised by this site.

The final documentation, consisting of this historical report and large-format historic and contemporary photographs, was never formally transferred to the Historic American Engineering Record for transmittal to the Library of Congress. In the original historical report was prepared for transmittal. The only substantive changes have been in formatting and to the historic images in the appendix. HORSESHOE DAM HAER No.

AZ-24 (Page 3) Introduction Located astride the Verde River about 66 miles northeast of Phoenix, the Horseshoe Dam is a 140'-high, rockfill storage dam with an interior core of rolled earth.1 The structure was built with a relatively conservative 3:1 slope on both upstream and downstream faces and ranges in cross- section from 50' at the crest to at the base and in length from at its crest to at its base. Its interior consists of an earthen core with a base width of approximately and a top width of A concrete cutoff wall extends into the bedrock foundation along the centerline of the entire dam. The earthen core is covered with rockfill quarried from the spillway and nearby sites and dumped in place by trucks.

Two gravel-surfaced roads extend across the dam, one angling up the downstream face from the spillway to the eastern abutment and the other running straight across the crest. When completed in Horseshoe Dam formed a reservoir with a capacity of acre- feet. (An acre-foot is a volume of water equal to 1 acre of land covered with water 1' deep; it is equivalent to cubic feet or about gallons.) In the reservoir s capacity was more than doubled to acre-feet by the construction of movable Tainter gates across the top of the 320'-wide spillway at the western abutment. With a maximum hydraulic height of 33' when closed completely, these gates allow water to be stored to within 13' of the dam s crest, impounding a 2,800-acre reservoir.

Water from the reservoir is normally released through a 730'-long tunnel that extends through bedrock under the western abutment. This 14'-diameter tube was originally drilled as part of an aborted irrigation project undertaken in the It remained unused for fifty years until work began on the Horseshoe Dam in the mid-1940s, when it was cleaned out and lined with reinforced concrete. A 220'-high, freestanding reinforced-concrete tower situated immediately upriver from the dam forms an inlet for water into the tunnel without the fear that sediment and silt will accumulate to block the opening. Water releases are controlled by a steel 9'-diameter cylindrical plug contained within the tower that can be raised and lowered to control flow through the tunnel opening.

Water enters the tunnel at the elevation of approximately above sea level and descends at a 5-degree grade until exiting through a simple pipe opening at an elevation slightly more than above sea level. Designed solely to provide water storage for irrigation and domestic water supply, Horseshoe Dam lacks a hydroelectric powerhouse or other power production facilities. Since the dam s completion, no serious consideration has been given to outfitting the site with electric generating equipment. Water releases from Horseshoe Reservoir have always been controlled exclusively by the needs of water users in the Salt River Valley without consideration given to potential hydroelectric power generation.

1 Data on the dimensions of Horseshoe Dam is available in Work Starting on Earth and Rock Fill Dam on Verde River in Arizona, Southwest Builder and Contractor 104 (7 July pp. Lawrence L. Lee, Arizona Earth and Rock Fill Dam Rising on Site Contemplated Fifty Years Ago, Western Construction News 20 (September pp. and Lawrence L. Lee, Horseshoe Dam: Arizona s Latest Addition to Her Irrigation System Nearing Completion, in History of the Salt River Project for the Period January 1, to December 31, The diversion tunnel at Horseshoe is described in Lawrence L. Lee, Arizona Tunnel Rehabilitated, Western Construction News 19 (September pp. HORSESHOE DAM HAER No.

AZ-24 (Page 4) Horseshoe Dam is located at a topographical bend in the Verde River about 40 miles north of the confluence of the Verde with the Salt River. Its name probably derives from the distinctive shape formed by the riverbed in curving around a large rock formation.2 Draining an extensive portion of central Arizona, the Verde River flows southward from headwaters in the San Francisco Mountains before entering into the Salt River about 40 miles east (upstream) of Phoenix. It is sometimes considered a hydrological entity in its own right. But because it feeds into the Salt River at a point above where most water is diverted from the larger stream for use in the Salt River Valley, the Verde is usually considered to be an integral part of the Salt River system.

In fact, the question of whether or not the flow of the Verde was to be subsumed within the general flow of the Salt River was a critical issue to the Phoenix area during the first part of the twentieth century. The chronology of Horseshoe Dam divides into two distinct phases. The first involves the initial discovery of the Horseshoe site at the end of the nineteenth century and the plans of the Rio Verde Canal Company to develop the Paradise Valley north of present-day Scottsdale by irrigated agriculture. The founders of the Rio Verde Company first filed claims to build a storage dam at Horseshoe in actually going so far as to drill a 730'-long diversion tunnel in anticipation of building a large storage dam at the site.

The Rio Verde interests proposed to build a canal over 100 miles long that would carry water by gravity flow from the Verde River to land in the Paradise Valley region that was at too high an elevation to receive water from canals that extended from the Salt River. As will be described, the Rio Verde Canal Company and its successors the Verde Water and Power Company, the Paradise-Verde Water Users Association, Paradise-Verde Irrigation District and the Verde River Irrigation and Power District never actually implemented any system to divert water from the Verde River for use in Paradise Valley or anywhere else in the greater Phoenix region.

Given the role played by the Rio Verde interests in bringing attention to the Horseshoe site and drilling a diversion tunnel here that is presently in use, the activities of the company warrant attention. The second phase relating to construction of the Horseshoe Dam concerns the activities of the Salt River Valley Water Users Association to develop the resources of the Salt River for the benefit of the farmers in the greater Phoenix area. Predecessor to today s Salt River Project, the Salt River Valley Water Users Association (SRVWUA) was formed in by farmers dependent on the flow of the Salt River for water to irrigate their extensive acreage of crops. As described in the report on the Roosevelt Dam (see HAER AZ-6), the SRVWUA played a pivotal role in the implementation of the U.S.

Reclamation Service s Salt River Project that included Roosevelt Dam 2 The origin of the name, as described by Arizona geographer Howell Granger, is uncertain, deriving either from the prominent bend in the river at this location or from the nearby One Horseshoe Ranch, in existence sometime before Howell Granger, X Marks the Place: Historical Names of Places in Arizona (Tucson: Falconer Publishing Company, p. 3 For more on the early development of water resources of the Salt River, see Donald C. Jackson, Roosevelt Dam, HAER AZ-6, Historic American Engineering Record, National Park Service, U.S.

Department of the Interior, and Karen Smith, The Magnificent Experiment: Building the Salt River Reclamation Project, For more on the post-World War I development of dams on the Salt River, see David M. Introcaso, Mormon Flat Dam, HAER AZ-14, and Donald C. Jackson and Clayton B. Fraser, Stewart Mountain Dam, HAER No. AZ-12. HORSESHOE DAM HAER No. AZ-24 (Page 5) In the eighty years since the completion of Roosevelt Dam, the Water Users Association has come to be the most important supplier of water in the Phoenix region and a key producer of electric power in Arizona. In the the association built three hydroelectric power dams Horse Mesa (HAER AZ-15), Mormon Flat (HAER AZ-14), and Stewart Mountain (HAER AZ- 12) along the Salt River below Roosevelt.

In the the group contracted with the Bureau of Reclamation (the federal agency created when the Reclamation Service changed its name in for construction of the Bartlett Dam (HAER AZ-25) on the lower Verde River.4 The Water Users Association s control of the Verde, and hence the development of the Salt River Valley, was further strengthened when it gained operational jurisdiction over the newly built Horseshoe Dam in Since this time no major dam has been built by any group along either the Verde or Salt rivers. To appreciate the fundamental conflict between the SRVWUA and groups such as the Rio Verde Canal Company, it is necessary to understand the development of early irrigation systems in the Salt River Valley and relative locations of the Verde and Salt rivers.

Shortly after the end of the Civil War, Jack Swilling established the first Angle irrigation canal in the region by digging out an ancient ditch originally excavated by the Hohokam. This waterway was soon supplemented by several other systems such as the Tempe Canal, the San Francisco Canal and the Maricopa Canal, providing water to land on both the north and south sides of the Salt River. These canals drew their water from the Salt River at diversion sites in or very close to the cities of Phoenix, Tempe and Mesa, more than 20 miles below the confluence of the Salt and Verde rivers. Consequently, canal owners and users considered their water rights to include the flow of the latter.

With irrigation systems that rely upon gravity (instead of pumping) to power water flow in the canals, it is possible to serve only agricultural land that lies at a lower elevation than the diversion dam. Thus, water diverted near Phoenix and Tempe could serve only a relatively small amount of land in the valley s lower reaches. To carry water to the higher parts of the valley, it became necessary to build diversion dams further up the Salt River and then deliver water through extremely long canals. In a new diversion dam was built at a site almost 40 miles east of Phoenix and only a short distance below the confluence of the Verde and Salt rivers.

This dam provided water for the newly constructed Arizona Canal that ran along the northern edge of the Salt River Valley for more than 60 miles before stopping near the edge of the Agua Fria River northwest of Phoenix. The Arizona Canal demarcated the partial limit of land in the northern part of the valley that could be watered from the Salt River using gravity flow canals. Any land north of the Arizona Canal would have to be irrigated by pumping or using water from a source other than the Salt. The significance of the Arizona Canal was later codified when it became the official northern boundary of the area served by the Salt River Valley Water Users Association. Lying entirely north of the Arizona Canal, Paradise Valley was unreachable by Salt River canals.

If water could be diverted directly from the Verde, however, it would be possible to transport it 4 The conflict over water rights to the Verde River in the and is documented in David M. Introcaso, Bartlett Dam, HAER AZ-25, Historic American Engineering Record, National Park Service, U.S. Department of the Interior. HORSESHOE DAM HAER No. AZ-24 (Page 6) over the ridge of mountains bordering the western edge of the Verde drainage basin. This formed the essence of all plans to develop the agricultural potential of the Paradise Valley using Verde River water. It is not difficult to understand why the SRVWUA opposed development of the Paradise Valley.

The association considered water from the Verde to be an integral part of the flow of the Salt River, and thus subject to the water rights of its constituent irrigators. Promoters associated with the Paradise Valley considered the Verde River a separate stream with floodwaters that could be appropriated for use on land that lay outside the boundaries of the SRVWUA. Herein lay the conflict between these two positions. The longstanding struggle for control of the Verde River between the two groups would form the compelling background for the Horseshoe Dam. Chapter 1: The Rio Verde Development and its Aftermath Completion of the Arizona Canal in June opened large areas of the north Salt River Valley to irrigation and settlement.

Without water, land in the valley was considered useless desert; with it, land rose significantly in value, as described by historian Geoffrey Mawn: Even before canal construction had started, speculators and settlers filed upon all available public land open to entry in the even-numbered sections south of the Arizona Canal, locating homestead claims for 160 acres and Desert Land Act entries for 640 acres. Before the completion of the canal, the company backers and speculators utilizing dummy entrymen filed claims on newly opened odd-numbered sections of public land that previously had been reserved as a land grant for the Texas and Pacific Railroad. In one local newspaper revealed that the Arizona Canal Company controlled over thirty sections of land or about acres.

This interest of the organizers in land and not the canal itself, had been present from the initiation of the Arizona Canal Project.5 Though important, this new development still left substantial tracts of desert lands north of the Arizona Canal in government hands, waiting for potential settlers, developers and speculators to implement a water supply system. Impetus for settlement in this area came within a few years. On July 4, the Maricopa and Phoenix Railroad, a branch of the Southern Pacific, arrived in Phoenix.

Faced with the responsibility for generating freight revenue on the new line, Osgood Wheeler, General Baggage Agent for the railroad, persuaded Army Captain Winfield Scott, then stationed at Angel Island in San Francisco Bay, to help promote immigration to the Salt River Valley. Scott had earned a reputation as an effective promoter of immigration as the first superintendent of the Kansas Immigration Society.6 When Scott came to Phoenix in February he was impressed with the region s fertility. He agreed to promote the Salt River Valley in the eastern United States.

Scott urged the introduction of citrus culture to the valley at a mass meeting of citizens, and he then invited representatives of the valley s business communities, farming interests and towns to participate in a Grand Exposition of Pacific Coast Products to be 5 Geoffrey P. Mawn, Phoenix, Arizona: Central City of the Southwest, dissertation, Arizona State University, p. 94. 6 During a promotional tour of the East in the winter and spring of Scott had extolled the virtues of moving to the West. Largely as a result, some settlers immigrated to Kansas the following summer. HORSESHOE DAM HAER No. AZ-24 (Page 7) held that fall in Ohio as part of the annual convention of the Grand Army of the Republic.

Scott organized the exposition and arranged space in the exhibit hall for the Salt River interests. Out of this invitation was born the Salt River Valley Exhibition Association, forerunner of the Phoenix Chamber of Commerce. After the convention Scott toured the East, visiting farm communities and promoting the virtues of Arizona s Salt River Valley.7 Early in two events occurred that would profoundly affect the valley s development. The first involved the relocation of the territorial capital from Prescott to Phoenix. Coupled with the new railroad and a new system of horse-drawn streetcars, Phoenix was now on its way to becoming the predominant economic and political force in the territory. The second involved the establishment of the region s first commercial citrus orchards.

Two groves were planted simultaneously, just miles apart, on land watered by the Arizona Canal. A 7-acre orchard owned by Winfield Scott himself, located near the present community of Scottsdale, contained fifty orange trees. A 16-acre tract owned by the Arizona Improvement Company (a holding company for the Arizona Canal) encompassed several hundred trees. This latter firm hoped to use the new orchard as a selling point for prospective buyers of its large land holdings. Two years later, in November the first harvest of these pioneer citrus groves proved successful.8 As the orchards took root in early March Augustus C. Sheldon, Samuel C. Symonds and Prosper P. Parker arrived at the mouth of Camp Creek in the Verde Valley.

Here the three men studied the feasibility of bringing Verde River water to the northern sections of the Salt River Valley above the Arizona Canal. As these would-be dam builders and land promoters left Phoenix, crossed the Arizona Canal and passed the Phoenix Mountains heading northeast, they viewed the desert in bloom. Mindful of land promotion brochures they might soon be distributing, they named this upper valley between the Phoenix Mountains and the McDowell Mountains Paradise Valley. The name would later be used by the Paradise Valley Water Users Association and the Paradise Verde Irrigation District. In addition to the preliminary survey, the men also dug small ditches from the Verde River and irrigated the few acres they had cleared for cultivation.

This surveying and pilot irrigation project proved to be the formative effort of the soon-to-be-formed Rio Verde Canal Company.9 Augustus Sheldon, the driving force behind the Verde survey and later the first president of the Rio Verde Canal Company, had arrived in Phoenix only two months earlier, in January A lawyer from Minneapolis, Sheldon had sought the dry mild climate of the valley in an effort to regain his failing health. Five months of outdoor living, including his reconnaissance work in the Verde Valley, had him solidly on the road to recovery.

Whether Sheldon had become interested in the valley and its agricultural potential before he came to Arizona or whether he was a quick 7 Rio Verde Company, Some Things That Were Said At A Luncheon Given By The Rio Verde Canal Company At Phoenix, Arizona, Tuesday, February 19, p. 13. Richard E. Winfield Scott: A Bibliography of Scottsdale s Founder, (M.A. thesis, Arizona State University, pp. 8 Winfield Scott, pp. Donald W. Campbell, Report of Donald W. Campbell, Supervising Engineer, on the Storage Irrigation System of the Rio Verde Canal Company of Phoenix, Arizona (Minneapolis: Alfred Roper, p. 4. 9 San Francisco Chronicle, 23 April Phoenix Daily Herald, 23 November McFarland and Poole, comp.

A Historical and Biographical Record of the Territory of Arizona (Chicago: McFarland and Poole, p. HORSESHOE DAM HAER No. AZ-24 (Page 8) study and grasped the potential of promoting the Verde-Paradise Valley area in just sixty days of exploration and inquiry is unknown.10 Sheldon s partner, Prosper Parker, had first come to Arizona the year before as a contractor on the South Gila Canal in Yuma County. Parker had gained broad experience as a surveyor and railroad contractor in the Midwest, having taken contracts on both the Chicago and Alton Railroad and the St. Louis, Hannibal and Keokuk Railroad.

Parker surveyed the original levels of the proposed Verde project and became secretary of the Rio Verde Canal Company upon its incorporation.11 The least known of the three principals in this initial survey, Samuel Symonds appeared not to play an active role in the management of the Rio Verde Canal Company. His initial participation is understandable, however, as partner in the Los Angeles-based real estate firm of Collins, Symonds and Company. Symonds partner, Michael E. Collins, had entered the Phoenix real estate market in and with streetcar developer and real estate promoter Moses H. Sherman had developed several subdivisions adjoining the Phoenix townsite.

Symonds undoubtedly was well aware of the Phoenix real estate market and the tremendous land promotion possibilities in the Salt River Valley.12 Without fanfare or public announcement, on April 13, Symonds and Sheldon filed a notice of location with the Maricopa County Recorder for rights to: 1) the flow of the Verde up to cubic feet per second; 2) the Horseshoe dam site; 3) a diversion dam site; and 4) a canal right-of- way across Paradise Valley to the Hassayampa River. Almost certainly they made this filing to protect their preliminary survey and reconnaissance work from irrigation project claim jumpers.

By the end of the year, the two men had supported their initial claim with two more public filings.13 Having found the key location for the diversion dam, which would allow construction of a gravity flow canal over the McDowell Divide into Paradise Valley, Sheldon, Parker and their engineers re-entered the Verde Valley in July to gather rainfall data, survey possible canal lines and reservoir locations, and calculate irrigable acreage in the Verde Valley under their canal. For the next twenty months, except for the summer of a force of thirteen to thirty- five men was in the field, surveying.14 10 McFarland and Poole, Historical Record of Arizona, pp. 11 Portrait and Biographical Record of Arizona (Chicago: Chapman Publishing Company, pp.

12 McFarland and Poole, Historical Record of Arizona, p. Richard E. The Relationship of Streetcars to Real Estate Promotion in Phoenix, (manuscript, pp. 10, Phoenix Daily Herald, 12 October, 13 Notice of Location by August C. Sheldon and Samuel C. Symonds, dated 13 April recorded in pages 152 and 153 in Book 1 of Canal Records, Maricopa County, in Notice of Appropriation. Entire Enterprise by the Verde Water and Power Company January 25, Arizona Department of Library, Archives and Public Records, Phoenix. Notice of Location of Dam and Reservoir Site by Samuel C. Symonds, dated 4 July recorded in pages 178 and 179 in Book 1 of Canal Records, Maricopa County, in Notice of Appropriation. January 25, Claim of Water Right and Location of Dam and Reservoir Site by Samuel C.

Symonds and Augustus C. Sheldon, date of notice 25 November recorded in pages 188 and 189 in Book No. 1 of Canal Records, Maricopa County, in Notice of Appropriation. January 25, 14 San Francisco Chronicle, 23 April McFarland and Poole, Historical Record of Arizona, p. HORSESHOE DAM HAER No. AZ-24 (Page 9) Meanwhile, in December the Phoenix-based Rio Verde Canal Company was incorporated. The firm s charter stated that the company proposes to build irrigation dams, canals, reservoirs and hydraulic works and to operate water and power generally with the area to be irrigated by the proposed project estimated at acres, served by a canal 119 miles in length. The first officers of the company were listed as: Augustus C. Sheldon, president; Charles P. Silloway, vice-president; Prosper P.

Parker, secretary; and Benjamin W. Thompson, treasurer.15 The fledgling company immediately printed copies of an illustrated sixty-four-page brochure promoting the advantages of the Salt River Valley for national distribution.16 In May thirty stockholders in the Rio Verde Canal Company reportedly arrived in the Salt River Valley to file on 320 acres each under the Desert Land Act of In addition, at least additional acres in 320-acre parcels had been filed on under the Desert Land Act by other individuals seeking speculative investment or small farm tracts. The terms of these filings revealed that the Rio Verde Canal Company paid the amount due at the time of the filing in exchange for the investor/settler assigning 300 acres of his claim to the company.

The investor/settler was also to receive a free water right for his remaining 20 acres.17 With this activity, it appeared that the company was preparing to move quickly to begin construction of its irrigation system. Another year would pass, however, before any public notice was given regarding the company s plans. On April 23, the San Francisco Chronicle published a description of the Rio Verde Canal Company project, noting the planned construction of a major dam at the Horseshoe site that would impound a acre-foot reservoir with a surface area of over acres. Water from the reservoir was to be released into the Verde River, where it would flow downstream for several miles before being turned into an irrigation canal by a small diversion dam.

Extending a distance of 140 miles, this canal was to carry water from the Verde River Valley into the Paradise Valley and other desert areas lying north and west of Phoenix.18 Four days after the article s publication, the canal company filed with the Maricopa County Recorder and the Secretary of the Territory a notice of appropriation of as much of the total flow of the Verde River as would aggregate a continuous flow of cubic feet per second.

The company further stated its intention to construct and maintain the Horseshoe Reservoir under the provisions of Act 86, Session Laws of the Seventeenth Legislative Assembly of the Territory of Arizona, passed April 13, This law stated that appropriation of water would date from the time of filing and posting a notice of appropriation at the point of diversion and with the appropriate county recorder if the construction of the works needed to deliver the water to beneficial use was completed within a reasonable time and maintained with reasonable diligence. 20 15 Phoenix Daily Herald, 18 December The Rio Verde Company, Arid Region 2 10; Portrait Record of Arizona, pp. 16 Phoenix Daily Herald, 23 November 17 The Rio Verde Company, p. 10.

18 San Francisco Chronicle, 23 April 19 Notice of Water Appropriation and Intention to Maintain Canals and Dam and Reservoirs under Act of April 13, by Rio Verde Canal Company, Secretary of State, Appropriation of Water, Dam and Reservoir Sites, Arizona Department of Library, Archives and Public Records, Phoenix. 20 Session Laws of the Seventeenth Legislative Assembly of the Territory of Arizona pp. HORSESHOE DAM HAER No. AZ-24 (Page 10) Just as the Rio Verde project began to take form, the country was wracked by the Panic of This nationwide financial crisis began in the spring of and by the summer of that year had impoverished many once-thriving business concerns.

Railroads were hard hit, with 25 percent of all railroad capitalization coming under the control of bankruptcy courts within two years. In rural areas banks toppled like houses of cards, with 153 such institutions failing in the South and the West during alone.21 A major consequence of the panic was that investment sources and speculative capital quickly dried up, leaving enterprises such as the Rio Verde Canal Company with little money with which to finance engineering projects. The Rio Verde group kept a low profile during the Panic, then in early announced that Langdon and Company of Minneapolis had been awarded a $2-million contract for the initial construction of the Rio Verde Canal Company project.

This involved building a diversion dam, a storage dam at the Horseshoe site to impound acre-feet of water and miles of main canal.22 Langdon would not be paid in cash. Rather, he would receive a generous amount of Rio Verde stock that he would then sell on the open market to raise money to cover construction costs. If a ready market for the stock were found, then both Langdon and the Rio Verde interests would benefit.

But if the stock proved unsalable, the work would cease.23 The initial plan to finance the construction with stock sales apparently proved unsuccessful, because no public notice was given as to actual work on the project in Early in the Rio Verde directors signed a new contract with the Minnesota and Arizona Construction Company.24 An amalgamation of Langdon s organization and Douglas Grant and Company of Fairbault, Minnesota, the firms had previously been involved in extensive railroad construction, having built a combined miles of rail lines during the preceding twenty years.25 By April 9, construction equipment had been shipped from Minnesota to Phoenix, and the contractors were on their way into the field.26 On July 10 the Phoenix Daily Herald reported that work was underway in drilling the 730'-long tunnel at the Horseshoe site that was to be used to divert the flow of the river when work was started on the dam project.

According to the Herald: The dam will therefore be constructed of rock taken from the mountains at either end of the structure and throughout its entire contract be built into solid rock in place. The dam will be three hundred feet long at the bottom or present water level, twelve hundred feet long on top and one hundred and seventy feet high.27 21 Samuel Elliot Morison, Henry Steel Commager and William E. Leuchtenburg, The Growth of the American Republic, 6th ed., 2 vols. (London and New York: Oxford University Press, 22 Phoenix Daily Herald, 7 June McFarland and Poole, Historical Record of Arizona, p. 23 Testimony of Christian People, p.

1, General Administrative and Project Record, Bureau of Reclamation, Record Group National Archives, Washington, [hereafter cited as NA, RG GAPR, 24 McFarland and Poole, Historical Record of Arizona, p. 25 Phoenix Daily Herald, 24 May 26 Phoenix Daily Herald, 8 April 27 Phoenix Daily Herald, 10 July HORSESHOE DAM HAER No. AZ-24 (Page 11) Although this structure was never built, it is interesting that the canal company and the contractors planned a rockfill dam at Horseshoe similar to the structure eventually built fifty years later. Throughout the remainder of and early work on the project proceeded steadily, if not particularly rapidly.

In a report to stockholders of the Rio Verde Canal Company on March 5, President Sheldon sounded upbeat in reporting water rights sales of million, of which would come in deferred payments. Company water rights were currently selling for $17 an acre, Sheldon stated, and would probably advance to $20 an acre as construction activity increased. He further reported that the company had formed an extensive system of agencies for colonizing the land under their proposed canal, and that through these agencies they had distributed between and pieces of promotional literature per month for the past year. Sheldon boasted 15 miles of canal had been completed and that the 730'-long diversion tunnel was close to being finished.

After describing the large amount of preliminary work that had been undertaken, he justified the expense in the name of safety, economy and efficiency in construction and operation. Sheldon applauded management on its diligence in the face of unusually adverse conditions, and in passing he claimed that the company s first mortgage issue of $2 million in 5 percent gold bonds had been sold and would be ready for delivery within a month.28 Sheldon s positive comments proved ironic, perhaps even deceitful, because within several weeks construction on the project would come to a halt, never to resume.

By mid-April the tunnel at Horseshoe had been finished, the diversion dam completed and an additional 5 miles of canal constructed.29 But shortly thereafter the contractors ceased operations, and the Rio Verde Canal Company began a long, slow demise the victim of its directors overly grand schemes. It may well be that Sheldon s report in March had been given with full knowledge of impending disaster, and his announcement of sales of $2 million worth of bonds was nothing more than a last ditch exercise in wishful thinking. As Arthur Powell Davis observed of the canal company s plan in The magnitude of the undertaking, the natural difficulties to be overcome, and the prevailing business depression combined to render its prosecution a matter of peculiar difficulty.

30 While the canal company s unfinished facilities lay idle in for lack of capital, the region was stricken by a severe drought that was to last for several years. Between and as many as acres of farmland were taken out of cultivation in the valley as a result of water shortages; agricultural development suffered tremendously.31 Despite these drought-related problems, the Rio Verde interests continued to support their project. With this in mind, the company s directors filed a notice of appropriation with the Maricopa County Recorder in January stating: 28 Phoenix Daily Herald, 5 March 29 Phoenix Daily Herald, 16 April 30 Arthur Powell Davis, Irrigation near Phoenix, Arizona, United States Geological Survey, Water-Supply and Irrigation Paper No.

2 (Washington, Government Printing Office, p. 64. 31 Stephen C. Shadegg, Century One: One Hundred Years of Water Development in the Salt River Valley, (Phoenix: W.A. Krueger, pp. HORSESHOE DAM HAER No.

AZ-24 (Page 12) The Rio Verde Canal Company, a corporation, of Phoenix, Arizona, does hereby locate, claim and appropriate perpetually so much of the flow, torrential and otherwise, of the unappropriated waters of the Verde River as will in the aggregate amount to a constant flow of cubic feet for each second of time [and] that said corporation intends to construct and maintain a reservoir in the Valley of the Verde River, known as the Horseshoe Reservoir of this corporation and the Rio Verde Canal Company hereby renews and reaffirms all locations, claims, rights and appropriations named in and heretofore claimed or held under a certain notice of location, claim and appropriation by this corporation made and dated the twenty-first day of December, A.D.

and posted of said date.32 After maintaining a low corporate profile for five more years, the Rio Verde Canal Company was reorganized in August as the Verde Water and Power Company, with Augustus Sheldon as president. Incorporated in Arizona, the new company s stated purpose was the business of supplying and using water for irrigation, city supply and manufacturing purposes as well as domestic use, and of supplying, distributing and using power and electricity.

33 The new firm acquired the rights, franchises and property of the Rio Verde Canal Company, including the 20 miles of unconnected canal, the outlet tunnel at the Horseshoe dam site, and all of its water right filings, dam and reservoir sites, power station sites and rights-of-way for canals, roads and telephone and telegraph lines.34 Despite the reorganization, no further construction was undertaken on the Horseshoe Dam or the canal to Paradise Valley. In events began to unfold that would eventually make it impossible for the old Rio Verde plans ever to reach completion. On June 17, the National Reclamation Act was signed into law by President Theodore Roosevelt. This law authorized formation of the U.S.

Reclamation Service within the Department of the Interior and provided the federal government with a direct role in financing and building irrigation projects in the western states. As part of the planning process for these irrigation projects and ostensibly to prevent speculators from gaining control of land that would soon increase in value the Department of the Interior was empowered to remove from entry any public lands that might prove necessary to use in implementing a federal reclamation project. The government could prevent anyone from taking ownership of a tract of public land under the provisions of a variety of federal laws such as the Desert Land Act of The only exception was that settlers could still use the Homestead Act of to file claims on federal land.

In practice, settlement under this latter law was rarely feasible in the arid West, however, and the Homestead Act exception did little to impede the Department of Interior from closing large tracts of western land from development. 32 Notice of Appropriation by the Verde Canal Company, dated 17 January Arizona Department of Library, Archives and Public Records, Phoenix. 33 Water Right Prospectus of the Verde Water and Power Company, Phoenix, Arizona, 12 November p. 1, NA, RG GAPR, Notice of Appropriation. Entire Enterprise by the Verde Water and Power Company January 25, p. 3, Arizona Department of Library, Archives and Public Records, Phoenix. 34 Water Right Prospectus of the Verde Water and Power Company, Phoenix, Arizona, 12 November p. 1, NA, RG GAPR, HORSESHOE DAM HAER No.

AZ-24 (Page 13) The significance of the Reclamation Act was first felt by the Verde Water and Power Company in the summer of when a substantial amount of land in the lower Verde River Valley was closed to entry in anticipation of a federally sponsored reclamation project in the greater Salt River Valley.35 Although this land withdrawal did not specifically include the site of the proposed Horseshoe Dam, it did include property traversed by the canal to the Paradise Valley.

By the summer of Department of Interior officials had removed from entry further tracts of land in the Verde River Valley that included the Horseshoe site.36 Although this action could have the effect of protecting the rights of the Verde Company from claims by other development interests, in fact the removal of land in the Verde River Valley created major obstacles to the implementation of plans to irrigate the Paradise Valley. These obstacles principally involved the organization of the Salt River Valley Water Users Association in Comprised of valley farmers who were already using Salt River water to irrigate land in the Phoenix region, this association was formed at the behest of the Reclamation Service in anticipation of a federally sponsored project to build Roosevelt Dam.

With water rights dating back as far as thirty years, these famers constituted a formidable group that held strong legal rights to the natural flow of the Salt River. Reclamation correctly perceived that the Water Users Association represented the water establishment in the Phoenix area, allying itself closely with the association s interests to assure success of its reclamation project. Conversely, the Reclamation Service expressed little interest in furthering the work of groups such as the Verde Water and Power Company, who were not yet actively engaged in irrigation.

The agency thus found itself in the odd position of opposing a group of small-scale settlers in their effort to reclaim farmlands by irrigation exactly the kind of people it was chartered by Congress to help in favor of established agricultural interests. Reclamation s feelings toward the Verde Water and Power Company were bluntly expressed in a September letter from Fredrick H. Newell, chief engineer (and later director) of the Reclamation Service, to the president of the Water Users Association.

Reacting to a promotional brochure published by the Verde interests, Newell wrote: I do not think I have ever seen a more outrageous and sacrilegious pamphlet that attempts to cover up the fraudulent character of the water rights under the guise of dedicating the profits to the support of evangelization. To a man who knows the facts, the reading of such stuff is nauseating, but its effect on credulous victims is such that in my opinion action should be taken officially by people of Salt River Valley to discredit the scheme and show it in its true light.37 35 Newell to Charles D. Walcott, 27 June E.A. Hitchcock to Commissioner of the Federal Land Office, 2 July United States Bureau of Land Management, Phoenix.

36 Newell to Secretary of the Interior, 22 July Acting Secretary of the Interior to Commissioner of the General Land Office, 27 July United States Bureau of Reclamation, Phoenix: Third Annual Report of the Reclamation Service 2d edition (Washington, Government Printing Office, p. form letter from Bureau of Reclamation, 18 December John K. Doolittle to John G. Hudson, 30 December NA, RG GAPR, 37 Newell to B.A. Fowler, 30 September NA, RG GAPR, HORSESHOE DAM HAER No. AZ-24 (Page 14) The Verde Company responded in kind to such attacks.

In December for example, the attorney for the Verde Water and Power Company wrote to an agent involved in trying to interest investors in the firm: It is rumored that some of the engineers connected with the Reclamation Service have announced the legal proposition that the passage of the Reclamation Act and the government s reservation of the Horse-shoe site under it, have had the legal effect to confiscate the property and wipe out, without compensation, the and more contributed by more than 300 persons and actually invested in the Verde enterprise. In view of the language of the Act of Congress and the well established principles of law applicable to the subject, their position is too grotesque for serious discussion. In the language of a noted counselor, There is no such law.

No intelligent court will listen to so ridiculous a doctrine.38 Unfortunately for the Verde Company, the Reclamation Service, which had a vested interest in blocking its effort, held the upper hand on availability of public lands in the Verde River watershed. Eventually the Verde River Valley lands were again made eligible for entry, but this did not occur for another decade. By this time the Verde Water and Power Company represented little more than a paper enterprise that had suffered repeated attacks on its corporate viability, both from the Salt River Valley Water Users Association in Arizona and from government agents in Washington.

For example, the company had been subject to investigations by the United States Post Office on mail fraud charges in and As the investigation proved, the firm had dutifully placed investors down payments into a bank account that remained outside the direct control of company officers. As of June a total of was held in escrow for water rights to land totaling acres.

In recommending that the investigation be closed, the Post Office reported: While the evidence in this case forces the conclusion that it is extremely doubtful whether or not the Verde Water & Power Company will ever be able to carry out their project to a successful termination, there is no evidence that their operations are being carried on with intent to defraud.39 Chronically undercapitalized and lacking the political clout of its well-heeled rival, the Verde Water and Power Company could not survive under the continuous pressure. The firm continued to struggle for several more years, occasionally surfacing to assert its claim to water rights on the Verde River.40 But by the firm was no longer a serious contender in the battle to gain control over the Verde.

After this time the primary adversaries over the river s future were the Salt River Valley Water Users Association and a new group, initially called the Paradise Valley Water Users Association. Formed in January this new entity was incorporated to construct, purchase, acquire, own [and] operate dams, reservoirs, canals, pumping plants and all necessary appurtenances thereto and all things necessary or convenient for the appropriation 38 John K. Doolittle to John G. Hudson, 30 December NA, RG GAPR, 39 Morgan Griswold, Postal Inspector to The Inspector in Charge, Cincinnati, Ohio, 24 June NA, RG GAPR, 40 John Hudson to Ray Lyman Wilbur, 20 April NA, RG GAPR, HORSESHOE DAM HAER No. AZ-24 (Page 15) and use of water for all beneficial purposes.

41 As the name implied, the water for the new association was to come from the Verde River and be applied to land in the Paradise Valley and adjacent areas outside the boundary of the Salt River Project.42 Within weeks of the formation of the new Paradise Valley group, the SRVWUA also began to take an active interest in building the Horseshoe Dam for its own benefit.

In January a board of survey, responsible for determining the legal limits of area to be served by the Reclamation Service s Salt River Project, reported that additional acres of irrigable land could be put into production if water supplies were obtained either through the installation of groundwater pumping plants or by building a storage dam at the Horseshoe site.43 The Water Users Association wasted little time in posting a notice of appropriation at the dam site on March 4, for all the surplus and flood waters flowing or to flow in the Verde River.

44 Within a month the SRVWUA approved an investigation to determine the feasibility of building a dam at Horseshoe; by February preliminary studies of the site were complete.45 But with disputes over how, and how much, the association was to pay for the federally financed construction of Roosevelt Dam and other aspects of the Salt River Project, the issue of building the Horseshoe dam was relegated to a secondary status.46 For twenty years the two water users associations waged a water war over the appropriation of Verde River floodwaters. The first conflict occurred late in the summer of That September the Salt River association took over direct control of the Salt River Project from the Reclamation Service and quickly formulated new plans to build a dam at the Horseshoe site.

Although the association had no way to fund construction of the structure, it sought to reassert its claim to the entire flow of the Verde.47 Meanwhile, in August the Paradise-Verde group made a similar application to the General Land Office for a right-of-way on which they planned to build the Horseshoe reservoir. In January the Reclamation Service notified the Salt River Valley Water Users Association Board of Governors of the Paradise-Verde application, asking if they had any objections to its approval.

Predictably, the board filed an immediate protest with the commissioner of the General Land Office.48 41 Articles of Incorporation filed 9 January Paradise-Verde Users Association, Arizona Corporation Commission Dead Files, Arizona Department of Library, Archives and Public Records, Phoenix. 42 For more on early water filings of the Paradise-Verde Water Users Association see I.D. O Donnell et al. to Secretary of Interior, Record Group 48, National Archives, Washington, U.S. Congress. Senate, Committee on Irrigation and Reclamation, To Correct Title of the Verde River Irrigation and Power District: Hearing on S. Congress, 1st session, 15 April p. 32; Data in Chronological Order Relative to Verde District, unattributed and undated typescript, p.

1, Salt River Project Archives [hereafter cited as SRP Archives]. 43 United States Reclamation Service, Salt River Project, Arizona: Limiting Irrigable Area of Land, January 15, pp. 44 Maricopa County, Arizona, Recorder s Office, Book 2 of Canals, p. 45 Salt River Valley Water Users Association, Minutes of the Meetings of the Board of Governors, Vol. 3, pp. Vol. 4, pp. 51 and 53 [hereafter cited as BOG]. 46 Richard E. Sloan, Land and Water Rights, Salt River Project, (manuscript, 10 May pp. SRP Archives. 47 Contract between United States of America and Salt River Valley Water Users Association, 6 September SRP Archives. 48 Verde River Storage Rights: Brief Filed at Hearing Before Sub-Committee of Committee on Irrigation and Reclamation of the U.S.

Senate at Phoenix, Arizona, November (typescript), p. 3, SRP Archives; BOG, Book 4, p. HORSESHOE DAM HAER No.

AZ-24 (Page 16) Early in the Paradise-Verde group officially changed its name to the Paradise-Verde Irrigation District, and a hearing was held with the Department of the Interior regarding the competing plans to develop the Horseshoe site.49 Interior officials convened two more hearings over the next two years on the Paradise-Verde proposal; both times the Reclamation Service officially recommended against any action which would facilitate construction of the Paradise- Verde project, but the Secretary of the Interior remained unconvinced by these arguments.50 Given that the Salt River group was in no position to build a dam at Horseshoe or anywhere else on the Verde without financial assistance from the federal government, the Interior Department would have had difficulty rationalizing why Paradise-Verde should not be given a chance to proceed with private financing.

After hearings held in May Secretary of the Interior John Barton Payne was impressed by the fact that Paradise-Verde lands were being settled. Believing that these settlers should be given an opportunity to secure irrigation water, he advised both parties that, unless an agreement could be reached, he would award the right to construct reservoirs on the Verde to the Paradise- Verde Irrigation District. Representatives of the Verde District and the SRVWUA tried to settle the dispute. The terms dictated by the Paradise-Verde interests, while acceptable to Payne, proved unacceptable to the Salt River group, however.

With no agreement forthcoming, Payne awarded the rights to Paradise-Verde to develop storage on the Verde with the proviso that the district demonstrate within three years that it had made arrangements to secure the necessary funding for the project and that construction had begun.51 The Secretary s ruling should have settled the issue, with the Paradise-Verde Irrigation District building its project and becoming a significant force in the agricultural development of central Arizona. In the face of generally depressed agricultural prices nationwide in the however, the district failed to secure financing for the project within the stipulated three-year period.

Early in the Paradise-Verde group requested an extension of the financing deadline, and, receiving a six-month extension, it officially reorganized itself as the Verde River Irrigation and Power District. In October the new district was granted another extension until February to make a satisfactory showing of its ability to obtain financing and get the project underway.52 When the district asked for yet another deadline extension early in the Department of the Interior staged more hearings in an attempt to find a way in which the Salt River Valley Water Users Association could facilitate construction of the Paradise-Verde development in return for an ironclad recognition of the association s legal right to the natural flow (but not flood flow) of the Verde.

Efforts to reach an accommodation between the two parties proved fruitless. Finally, in January the Secretary of the Interior refused to authorize any more deadline extensions, and the Verde River Irrigation and Power District forfeited its authorization to build dams on the Verde and to construct a canal across public land.53 49 Election Results, March 2, ADM Verde River Irrigation District, Clerk of the Board, Maricopa County Board of Supervisors, Phoenix; and Verde River Storage Rights, p. 3; BOG, Volume 4, p. 50 Verde River Storage Rights, pp. 51 Ibid., pp. 52 Ibid., pp. 53 T.A. Hayden, History of Water Rights of the Salt River Project with Special Reference to the Supply from the Verde River (typescript, 8 July p. 10. HORSESHOE DAM HAER No.

AZ-24 (Page 17) After attempting unsuccessfully to reverse the Secretary of the Interior s ruling through court action and political pressure, the Verde River District directors once again tried to coordinate their efforts with the SRVWUA. Throughout and early leaders of the district and the association discussed accommodations for their mutual interests in the Verde River. After over a decade of sometimes acrimonious negotiations, the two groups finally reached a tentative agreement in June In this proposed compact, the Verde River Irrigation and Power District acknowledged the right of the Salt River Project to all natural flow of the Verde River as well as to any flood flow which could be utilized by existing facilities.

In return the district retained the right to build storage dams on the Verde for use in impounding floods as well as the right to erect the rest of the Paradise Valley irrigation system. The pact included numerous other stipulations regarding production, cost sharing, etc., but the heart of the compromise lay in the apportionment of water rights on the Verde.54 The agreement was immediately approved by the Department of the Interior and in December by the membership of the Verde River Irrigation and Power District. The shareholders of the SRVWUA also needed to ratify the contract for it to take effect, but public sentiment did not appear favorable in December Formal vote was postponed for a full year in an attempt to increase popular acceptance of the plan.

Despite the urging of the association s leadership to accept the pact, the shareholders rejected it in December by a margin of to The proposed accommodation between the Paradise-Verde interests and the Salt River Project had failed; future control of the Verde River remained uncertain. The Verde River district immediately moved to take advantage of this setback by reapplying to the Department of the Interior for authorization to build the Paradise-Verde irrigation project on their own.

Reversing his decision, the Secretary in June granted the district another five-year period in which to finance and implement the plan.56 But as the original promoters of the Paradise-Verde project had discovered in fundraising for a capital-intensive venture was virtually impossible during a financial crisis. With the country struggling through the early years of the Great Depression, the district was unable to raise sufficient private financing for the project. Franklin D. Roosevelt s election as President late in increased the prospect for federal funding dramatically, however.

As part of Roosevelt s New Deal effort to provide financial relief to the American economy, in November the Public Works Administration offered the Verde district a loan of more than $18 million to help fund improvements that were to include storage dams at the Bartlett and the Horseshoe sites on the Verde River.57 Finally, it appeared as though the efforts started by the Rio Verde Canal Company to irrigate the Paradise Valley would be successfully revived. 54 See Agreement Between Salt River Valley Water Users Association, Verde River Irrigation and Power District and United States of America, June 19, A copy is available in the Arizona Collection, Arizona State University Library, Tempe. 55 Hayden, History of Water Rights, pp. 56 Ibid., p. 12. 57 Data Relative to the Verde District, p.

3; Verde Project Gets Loan of 4 Million, Yuma Morning Sun, 4 November HORSESHOE DAM HAER No. AZ-24 (Page 18) In the face of such massive government financial support for its longtime rival, directors of the SRVWUA acted quickly to gain control of the Verde River. Mustering as much political influence as possible, the association conducted an intense lobbying campaign in Washington, to force revocation of the federal loan to the Verde district. Stressing the political power of the association s membership within the state, Arizona s congressmen were soon enlisted to help promote the cause of the Salt River Project. By the fall of this lobbying had produced the desired result.

On October 3, the Federal Emergency Relief Administration authorized an expenditure of $6 million to construct new spillways on the association s existing Salt River dams and to build a new storage dam at the Bartlett site on the Verde as part of the Salt River Project. The next day the Secretary of the Interior acted to prevent any federal funds from going to the Verde River Power and Irrigation District for its planned development. Verde River district members could only watch in frustration as their five-year time limit for building the Paradise-Verde project expired the following October.

Proponents of the Salt River Project were now free to pursue their own plan to impound the floodwaters of the Verde River.58 In November the SRVWUA signed a contract with the Department of the Interior for construction of a large storage dam on the Verde at the Bartlett site. Work on this multiple-arch dam began in the summer of and reached completion almost three years later in May With use and control of this structure, the Salt River Project established complete control of the lower Verde River watershed.

Although the Verde River Power and Irrigation District would remain active for many years to come, it would never again come close to implementing an irrigation development scheme.59 With attention focused on the Bartlett site, interest in building a storage dam at the Horseshoe site had taken on secondary importance during the After the Bartlett Dam was completed, the Salt River Project was in a strong position to lay claim to the entire flow of the Verde as the only entity that could use the storage potential of the Horseshoe site.

Although the Salt River Project was not adverse to constructing a dam at Horseshoe, in the wake of the new debt the SRVWUA had assumed to build the Bartlett Dam (added to the sizable outstanding debt incurred for construction of the Roosevelt, Granite Reef, Mormon Flat, Horse Mesa and Stewart 58 For evidence of politicking on the part of the Salt River Valley Water Users Association, see: Greig Scott to Lin B. Orme, 22, 23, 24, 25, 27, June, and 2, 5, 21, 24 July Greig Scott to Lin B. Orme, 25 June, 5 July Greig Scott to Lin B. Orme, 2, 5, 7 July Henry Fountain Ashurst to Lin B. Orme, 9 July Lin B. Orme to Greig Scott, 23 July all in SRP Archives. For further information on the Salt River Project s early development of the Verde, see: Raymond A.

Hill, Application for Allotment by the Federal Emergency Relief Administration for Public Works to the Bureau of Reclamation, Department of the Interior for Salt River Project in Arizona, 3 October (typescript); Raymond A. Hill to H. J. Lawson, 23 July SRP Archives; Harold L. Ickes to Carl Hayden, 5 October Federal Emergency Relief Administration of Public Works, PWA Press Section, Release No. Franklin D.

Roosevelt to McCalla (draft for President s signature), 12 August Department of the Interior; and Appeal from the General Land Office, 23 March NA, RG Salt River Project, 59 Elwood Mead to Carl Hayden, 16 November NA, RG Salt River Project, Contract between the United States of America and the Salt River Valley Water Users Association Providing for the Construction of Bartlett Dam and Repairs to and Completion of Other Dams and Project Canals, 26 November History of the Salt River Project for the Period January 1, to December 31, Inc., (typescript, p. 51; E.C. Koppen, Building Bartlett Dam, Reclamation Era p. HORSESHOE DAM HAER No. AZ-24 (Page 19) Mountain dams on the Salt River), it was in no position to begin construction of yet another large water storage structure.

The lack of concern about construction of a dam at Horseshoe is perhaps most tellingly documented in a September report analyzing the status of the Salt River Project in light of economic activity related to World War II and its anticipated aftermath. Written by Raymond Hiss on behalf of the engineering firm of Leeds, Hill, Barnard and Jewett, the 130-page Economic Survey of Salt River Project, Arizona, investigated and assessed a wide range of issues that could affect the health and growth of the Water Users Association, including the potential benefits of upgrading the electric power system, restructuring the water and electric rates and reducing operating costs.60 Significantly, nowhere in the report is there discussion of how or when a new dam might be built at Horseshoe.

In the fall of the idea of building such a dam was not considered part of the Salt River Project s development scheme for the war and postwar years. Within a year, however, impetus for constructing such a dam would come from a source with no previous involvement in efforts to develop the Verde River. As it turned out, the interest of the government and the Phelps Dodge Corporation in increasing America s supply of copper during the war would prove to be the key in reviving plans to build a dam at Horseshoe.

Chapter 2: Phelps Dodge and the Morenci Development The origins of the Phelps Dodge Corporation date to the early nineteenth century when saddle maker and leathersmith Anson Greene Phelps expanded into the mercantile business.61 Originally based in Connecticut, Phelps had relocated his operation to the growing port city of New York by After the War of Phelps international trade blossomed as he specialized largely in exporting southern-grown cotton to Europe and importing metals such as copper, brass, tin and lead to the United States. Phelps soon developed an expertise in copper that would later figure in the development of the copper company bearing his name.

Through the early Phelps operated in partnership with Elisha Peck, but after a disastrous fire at the Phelps-Peck warehouse in he reorganized his business associations and soon established a new partnership with sons-in-law William E. Dodge and Daniel James. Anson Phelps died in By the time William Dodge died thirty years later, Phelps Dodge & Company had become an industrial giant, with substantial holdings in railroads, coal and mineral mining and lumbering.62 Included among these were copper mines in Arizona Territory, which would become the core of the firm s business in the twentieth century.

The impetus for Phelps Dodge s direct financial involvement in the Arizona copper industry stemmed from recommendations from James Douglas, a mining engineer and metallurgist who advised the company on technical matters related to the metal trade. After being offered an opportunity by owners of the Detroit Copper Company to invest in an expansion of its mine at 60 See Raymond Hill, Economic Survey of Salt River Project, Arizona, September BOG, Volume 26, 30 September 61 Unless otherwise noted, data in this chapter is taken from Robert G. Cleland, A History of Phelps Dodge (New York: Alfred A. Knopf, For discussion of Phelps early career see pp. 62 Ibid., p. 28.

Daniel James became the man in charge of European operations and a partnership known as Phelps, James & Company was established in England. HORSESHOE DAM HAER No. AZ-24 (Page 20) Morenci, Phelps Dodge called upon Douglas in to examine the quality of the Detroit company s holdings. While involved in this work, Douglas also examined other mining properties in the region, including claims centered around the town of Bisbee in the extreme southeast corner of the territory. At Douglas urging, Phelps Dodge invested in operations that were already involved in exploiting deposits at both Morenci and Bisbee.

The firm s purchase of what was known as the Atlantic Claim in Bisbee proved lucrative in the short run, especially after this claim was merged with the nearby Copper Queen mine in to form the Copper Queen Consolidated Mining Company.63 The decision to invest in the Morenci District also provided long-term dividends, especially in the twentieth century when technological advances allowed profitable smelting of relatively low-grade ores. It was the search for water needed in processing the low-grade ore at Morenci that would prompt Phelps Dodge s interest in building a dam on the Verde River for the SRVWUA.

Knowledge of the mineral deposits present at what came to be called the Morenci District sometimes also known as the Clifton-Morenci District in reference to the nearby town of Clifton derived from prospecting in the period shortly following the Civil War. In the late mineral expeditions based out of the Silver City mining area in southwest New Mexico extended into the upper reaches of the Gila River watershed not far from the New Mexico/Arizona border.64 The San Francisco River is a major tributary of the Gila, with a drainage area that abuts the upper reaches of the Salt River watershed. Near the confluence of Eagle and Chase Creek with the San Francisco River, prospectors discovered copper ore deposits rich enough to develop.

In entrepreneur Henry Leszensky built a small furnace to smelt ore, and by the Longfellow Copper Company (controlled by Leszensky and his partner T. Freudenthall of New York) had built a large smelter with a daily production capacity of almost 4 tons.65 In the other mines were developed in the Clifton-Morenci District, the most important of which was the Detroit Copper Company complex under the control of William Church and E.B. Ward of Detroit.66 Because of difficulties in securing a stable water supply in the early the Detroit Copper Company proposed to build a 6-mile-long pipeline to connect its smelter in Morenci with Eagle Creek.

To finance the construction, the company sought support from Phelps Dodge, which in provided capital for the pipeline in return for a substantial stake in Detroit Copper. Phelps Dodge gradually increased its Detroit holdings until the mining operation was under the direct control of Phelps Dodge by the mid-1890s. Previously, in the early the Longfellow Copper Company had also come under the control of outside investors and was renamed the Arizona Copper Company. For the next forty years the Detroit and Arizona companies comprised the major forces in the Clifton-Morenci district as they steadily increased the region s 63 Ibid., pp. The importance of the Bisbee/Copper Queen holdings to the fortunes of the company in the late nineteenth century is discussed in this section of Cleland s book.

64 For more on the early history of the Morenci District see: Remington F. Barr, Phelps Dodge Corporation- Morenci Branch: Plant-Production-History, (typewritten manuscript, ca. a copy of this informative manuscript is available in Manuscript Collection, Box 7, Arizona Historical Foundation, Arizona State University Library, Tempe. 65 Ibid., p. 5. 66 Cleland, History of Phelps Dodge, pp. HORSESHOE DAM HAER No. AZ-24 (Page 21) productivity.67 A key development in the district occurred in when an 18-mile-long connection was made between Clifton/Morenci and a line of the Arizona & New Mexico Railroad located to the south.

This rail link greatly facilitated shipping of the smelted copper and promoted further development of the region s ores.68 Shortly after the end of World War I, the Phelps Dodge Corporation (incorporated in acted to take control of all holdings in the Clifton-Morenci District. The key to this consolidation came with Phelps Dodge s takeover of the Arizona Copper Company late in Prior to this, the Detroit Copper Company had merged with Phelps Dodge, and, beginning in the early all operations in the district were referred to as the Phelps Dodge Corporation-Morenci Branch or just Morenci. 69 Following this consolidation, operations in the district remained relatively static in terms of the basic technologies employed in mining and ore processing.

Through the all ore at Morenci was obtained through deep-shaft mining that exploited relatively rich underground veins. Miners had long known that vast quantities of low-grade ore known locally as the clay orebody existed near Morenci, but it was not considered feasible to smelt this ore profitably because of its extremely low copper content. Given the magnitude of clay orebody available, however, Phelps Dodge eventually began exploring the possibility of developing a plant to process such low grade-ore on a massive scale. Between and Phelps Dodge drilled intensively around the region to determine the approximate size and geological form of the clay orebody deposit.

From these studies it was determined that there were between 200 and 300 million tons of 1 percent copper ore lying at a depth of to below the surface.70 The company then set out to develop a means for processing this huge low-grade deposit at a scale that would make the enterprise cost effective. The initiative at Morenci was masterminded by Louis S. Cates, appointed president of Phelps Dodge in after working his entire life as a western mining engineer/businessman.

Cates had been closely involved in developing the tremendous open-pit copper mine at Bingham Canyon, Utah, an experience which proved ideal in planning the new Morenci facility.71 One key to developing the clay orebody at Morenci lay in abandoning the old methods of mining ore through underground shafts and digging a huge open pit accessible to railroad cars that could be filled with ore and then hauled directly to the processing plant. The other key lay in developing a processing system that could extract the copper from the low-grade ore quickly and inexpensively for shipment to the Phelps Dodge plant in El Paso, Texas, for final smelting.

In grappling with the latter of these two problems, the firm experimented with a technique known as flotation as a means of separating the copper ore from the waste rock. As ultimately executed, the flotation system at Morenci worked in the following manner: Ore from the open pit was delivered in 80-ton capacity railroad cars and dumped into large crushers at a rate of about one car per minute. The crushers reduced the ore to pebble size, after which it was mixed with 67 For evidence of this, see Barr, Morenci Branch, pp. 68 McClintock, Arizona, p. 69 Barr, Morenci Branch, p. 1. 70 Cleland, Phelps Dodge, pp. 71 Ibid., pp. HORSESHOE DAM HAER No. AZ-24 (Page 22) water and ground into a fine paste-like substance known as pulp.

The wet pulp was then placed into long tanks, or flotation cells, in which it was mixed with oily chemicals to separate the ore from the waste rock. Material in the flotation cells was constantly agitated so that the copper in the ore could become attached to air bubbles and then lifted (or floated) to the surface as part of an oily froth. As the waste rock sank to the bottom, this copper-rich froth was skimmed from the surface of the flotation tank. The waste rock was subsequently removed and, after water drained from it for reuse, eventually dumped in large tailing ponds.

The froth was then dried and delivered to the smelter where it was further refined in furnaces before being shipped from the site.72 The flotation process installed at Morenci allowed ore with a 1 percent copper concentration to be refined quickly into a froth ranging from 22 to 30 percent of copper content. The flotation process was not the only concentration method employed at Morenci, but it played a critical role in supplying a high-grade concentrate that could be easily refined to a purity of 99 percent in the smelter s furnaces. Successful use of flotation technology at Morenci required approximately 175 gallons of water for every ton of ore processed.

Given that the plant ultimately handled tons of ore a day, almost 9 million gallons of water were required on a daily basis to operate the flotation system. Much of the water could be recycled, but substantial quantities were unavoidably lost in smelting the froth, requiring the constant availability of large amounts of fresh water. By the early Phelps Dodge considered the construction of a huge new facility at Morenci to represent the firm s best hope for continued growth. But the collapse of copper prices that accompanied the Great Depression left the company in no position to finance a major capital improvement project at Morenci. Gradually, the market for copper improved; by the price of the metal was almost double what it had been five years earlier.

At that time the firm chose to proceed with the $35 million Morenci project. In June it authorized sale of new public securities to help finance the work required to develop the open pit mine and build the new crushing plant, smelting facilities and housing for the thousands of workers to be employed at the site. While construction on the new smelter continued into the late and early international tension was rising in Europe and the Pacific Rim as the world headed into another massive war. Although America would not enter the war officially until after the Japanese bombing of Pearl Harbor in December efforts were initiated during the summer of to support a national defense buildup.

A sizable increase in America s ability to wage war would necessitate an expansion of the nation s industrial and manufacturing capacity. To assist such 72 The technical operations at Morenci are described in John B. Huttl, Morenci Expands to Meet War Demand, Engineering and Mining Journal 144 (July pp. also see Cleland, Phelps Dodge, pp. for a good description of the processing methods employed at Morenci that is written in a style understandable to a general audience. For more data on the technology of flotation see Donald M. Liddell (editor), Handbook of Nonferrous Metallurgy: Principles and Processes (New York: McGraw-Hill Book Company, pp. and Robert H. Richards and Charles E. Locke, A Text Book of Ore Dressing, second edition (New York: McGraw- Hill Book Company, pp.

HORSESHOE DAM HAER No. AZ-24 (Page 23) expansion, the government formed the Defense Plant Corporation in as an offshoot of the Reconstruction Finance Corporation.73 The purpose of the DPC was to provide direct financial support to companies involved in military-related production. This included work such as aircraft and ship construction, engine assembly, machine tool production and strategic metal extraction and production. Vital to a wide variety of electrical and electronic systems and devices, copper was included in the latter category. By the end of the war in the Defense Plant Corporation had invested in some American industrial plants, providing each an average of $3 million to upgrade production capacities.

This resulted in a government investment of more than billion in private industry during the war years.74 In April Phelps Dodge began copper production from its newly completed facility at Morenci. At that time the War Production Board, a federal agency charged with planning America s industrial development during the war years, directed the company to increase its overall copper production by 80 percent. As part of this effort, the processing capacity of the Morenci plant would be more than doubled, from tons to tons of copper ore per day. This involved construction of new processing equipment, housing, etc.

that would eventually require the expenditure of $42 million in funds from Phelps Dodge and another $26 million from Despite the huge financial resources available, the one thing that money could not buy directly was water. For the original Morenci plant, Phelps Dodge had planned to use the flow of Eagle Creek. But doubling the plant s production capacity required a major new source of water. In the fall of Phelps Dodge engineers began considering drawing this new flow from the upper reaches of the Salt River watershed. Chapter 3: Planning and Approval of Horseshoe Dam Before approaching the SRVWUA for permission to divert water from the Salt River drainage basin, Phelps Dodge first sought to draw additional flow from the San Francisco River as it passed near Morenci.

The plan drew strong opposition from irrigation interests in the Safford Valley, however, as well as residents of the San Carlos Indian Reservation. Both groups used water from the Gila River and would have been adversely affected by increased diversion from the San Francisco River, a major tributary.76 Phelps Dodge then explored the idea of building dams on both the lower Gila River and on the San Pedro River far to the south as a means of compensation, but this quickly proved unworkable. Rather than increasing its use of the San Francisco River, the company devised a plan by September to pump water from the Black River over an intervening mountain range into the headwaters of Eagle Creek. From there it 73 An excellent general history of the DPC can be found in Gerald T.

White, Billions for Defense: Government Financing by the Defense Plant Corporation During World War II (Tuscaloosa, Alabama: University of Alabama Press, 74 Ibid., p. 10; billion is for DPC funding only; another $18 billion came from other federal sources supporting the war effort. 75 Cleland, Phelps Dodge, p. 76 For more on early plans to get additional water for Morenci, see memo from Harry G. Raschbacher to Director of Project Planning [for the Bureau of Reclamation], 15 November NA, RG GAPR also in file no. SRP Archives. HORSESHOE DAM HAER No. AZ-24 (Page 24) would flow downstream by gravity for use at Morenci. The easternmost tributary of the Salt River, the Black River contributes significantly to the water levels of the present stream.

Like the farmers of the Safford Valley, the SRVWUA looked askance at any proposed diversion from the Black River. Phelps Dodge president Louis Cates proposed that his company buy a large tract of land in the Salt River Valley that was part of the Roosevelt Water Conservation District. This district received water directly from the SRVWUA, and Cates intended to use the water rights from this tract in the Salt River Valley to allow partial diversion of the Black River over the mountains to Morenci. In September the association s board of governors met to consider this request.

After acknowledging that public emotion may be aroused through pleas to aid in the war effort the board unanimously rejected the proposal and characterized it as promoting the diversion of water to purposes other than the essential ones to which it is dedicated (i.e., irrigation). The board further stated that: [We] reaffirm the association s declared policy of full protection to the water rights of the Salt River Basin through the use of all lawful means in preventing the diversion of any of the waters there from.77 In this decision the Salt River Valley Water Users Association was adamantly protecting its own interests.

Water taken from the Black River for use at Morenci would never find its way downstream through the association s hydroelectric powerhouses at Roosevelt, Horse Mesa, Mormon Flat or Stewart Mountain. Furthermore, it would be lost to irrigation in the Salt River Project. If the Water Users Association s campaign against the Paradise Verde interests was any indication, the group was prepared to use any tactic necessary to retain its domination of the Salt River watershed. World War II affected the Phoenix area along with the rest of the country, with many of the valley s residents serving in the military while many others provided support at home.

The association s governors were kind to mention the war effort before dismissing it out of hand, but their message to Phelps Dodge was clear: war or not, they would guard the association s interests above all else. Phelps Dodge and the SRVWUA held further discussions during the early fall of By mid- October the company had devised a new proposal to compensate for its diversions from the Black River by financing construction of a new storage dam on the Verde River that would capture flood flows in excess of the capacity of the recently completed Bartlett Dam.

This new dam, to be built at the Horseshoe site, would be financed by the On October 16 the board of governors voted to approve the request in principle, provided that: 1) the diversions from the Black River never exceed a cumulative total of acre-feet; 2) the new storage dam at Horseshoe have a minimum capacity of acre-feet; 3) the Water Users Association be financially compensated for the electric power revenues that would be lost because of the upstream diversions; and 4) approval of the project be ratified by a vote of the shareholders of the association.78 77 BOG, Volume 27, Minutes of 7 September 78 BOG, Volume 27, Minutes of 16 October HORSESHOE DAM HAER No.

AZ-24 (Page 25) By placing a limit on the total diversion from the Black River, the association was able to prevent Phelps Dodge from gaining control of water resources within the Salt River Basin. And by demanding that the government pay for enlarging the association s water storage system on the Verde, the association would gain even more control over the stream s floodwaters. The Verde River Power and Irrigation District had been stymied in the by the association and the Bureau of Reclamation with construction of Bartlett Dam. However, no guarantee existed that the Verde group would not devise some way to appropriate the Verde River s unclaimed floodwaters for use in the Paradise Valley.

For this reason, the temporary relinquishment of water from the Black River seemed a reasonable price to pay for a dam at Horseshoe. It was rendered even more attractive by Phelps Dodge s agreement to compensate the association for lost power revenues resulting from the upstream diversion. With the prospect of greater profits and increased control over the region s water resources, the board of governors found little reason not to support the war effort. Negotiations between Phelps Dodge and the Water Users Association proceeded rapidly.

By mid-November the board of governors had approved a contract covering the Black River diversion and the construction of Horseshoe Dam.79 Under the agreement Phelps Dodge could not divert water from the Black River at a rate of more than 40 acre-feet per year; cumulative diversions could not exceed a total of acre-feet. Further, if the government ever requisitioned more water out of the Salt River Basin for use at Morenci, this additional diversion would be included as part of the acre-foot limit. Phelps Dodge s water rights to the Black River were established in terms of a water exchange with floods impounded on the Verde River.

After completion of the Horseshoe Dam, any water stored along the Verde that exceeded the existing capacity of the Bartlett Dam (about acre-feet) would be considered exchange water that Phelps Dodge would have rights to exchange for purposes of replacing the amount diverted from the Black River. This arrangement provided a legal framework for justifying Phelps Dodge s right to use water from the Salt River basin. It also served the association s interest in providing a mechanism for limiting (or even stopping) the diversions to Morenci during periods of drought when little water could be store along the Verde. If water stored behind Horseshoe and Bartlett Dams remained low for a sustained period of time, Phelps Dodge would have no rights to such exchange water.

In the initial negotiations concerning construction of Horseshoe Dam, Phelps Dodge and the Water Users Association planned a structure that would impound a 60,000-acre-foot reservoir. The reservoir s capacity was eventually increased, but the basic terms underlying the financing and construction of the dam were established by November Phelps Dodge agreed, at its sole cost and expense and as expeditiously as possible after this agreement become operative, [to] construct, as an extension to the Salt River Project works, a dam and appurtenant works at the Horseshoe dam site on Verde River.

80 By contract, title to the dam and dam site would remain in federal hands, but operation of the structure would be controlled by the SRVWUA an arrangement similar to that used for the 79 BOG, Volume 27, Minutes of 18 November 80 Ibid., Article I, paragraph 1. HORSESHOE DAM HAER No. AZ-24 (Page 26) association s other storage dams on the Salt and Verde rivers. Plans and specifications for the dam were to be prepared by Phelps Dodge, subject to approval by both the chief engineer of the Bureau of Reclamation and by the SRVWUA.

The contract stipulated that, if necessary, Phelps Dodge would retain a competent firm of independent consulting engineers to inspect the work for and on the behalf of the association during the course of construction to determine whether the work is being performed in accordance with the plans and specifications. Reclamation s chief engineer would arbitrate any disagreements over the quality of work. The agreement also addressed the issue of compensating the Water Users Association for the loss in power revenue that would result from the Black River diversion.

Phelps Dodge was to pay the association a sum roughly equal to the amount of money that could have been collected through the sale of hydroelectric power if the water diverted from the Black River had been allowed to flow through association power plants.81 The agreement was to be signed by Phelps Dodge, the SRVWUA, the and by the Secretary of the Interior. In addition the shareholders of the Water Users Association also needed to ratify the contract in a special election. Both Phelps Dodge and the DPC were anxious to formalize the agreement as quickly as possible to speed production at Morenci.

With this in mind, Phelps Dodge agreed to complete work on the Horseshoe Dam one year following the first day of February on which this agreement is operative, unless prevented by floods or other circumstances beyond its control. In other words, if all parties to the agreement moved swiftly to ratify it, then Phelps Dodge committed itself to completing the dam in February Otherwise, the copper company would have a full extra year (until February in which to finish construction. After reaching a preliminary agreement with the SRVWUA concerning the Horseshoe Dam/Black River diversion project in November Phelps Dodge and the Defense Plant Corporation assumed it was only a matter of time before final approval of the pact would be forthcoming.

In fact, in early December Phelps Dodge let a contract to Vinson & Pringle, a Phoenix-based construction firm, to clean out the fifty-year old diversion tunnel at Horseshoe and line it with reinforced concrete.82 This project did not involve the dam itself and was thus easier to start construction without need for Reclamation approval of the plans. When Phelps Dodge and the Defense Plant Corporation began expending money to upgrade the diversion tunnel in December they could not be certain that Horseshoe Dam would be built. They were so anxious to increase Morenci s copper production that spending money on the diversion tunnel before final project approval seemed a worthwhile risk.

Fully committed to building Horseshoe Dam after November Phelps Dodge remained uninvolved in the final negotiation concerning the proposed project. 81 Ibid., Article I, paragraph 3. The annual power compensation payment was to be calculated by dividing the gross hydroelectric power revenues of the association by the total number of acre feet of water passing through the Stewart Mountain powerhouse during the same period of time. This would provide the amount of power revenues generated by 1 acre foot of water flowing down the length of the Salt River. This amount would then be multiplied by the total number of acre feet diverted out of the Black River for that year, and this figure would constitute the annual payment owed by Phelps Dodge. 82 Lawrence L.

Lee, Arizona Tunnel Rehabilitated, Western Construction News 19 (September pp. HORSESHOE DAM HAER No. AZ-24 (Page 27) The next hurdle was in securing the approval of the Secretary of the Interior Harold Ickes.

In late November the SRVWUA informed Ickes of the planned project, stating that it would: Operate and maintain the [Horseshoe] dam and its appurtenances in the same manner and under the same manner and under the same conditions as it is required to operate and maintain other works on the [Salt River] Project under its contracts with the United States.83 In addition, the association agreed to fully protect all rights of others entitled to water from Salt River or Verde River with specific attention given to ensure that the residents of the Salt River Reservation received the water that had legally been allotted to them.

The Water Users Association requested that the Secretary approve the construction of Horseshoe Dam and allow the public land comprising the site to be used for such a purpose. In forwarding Ickes a copy of the agreement that had been approved a few days before by Phelps Dodge, the Defense Plant Corporation and the association s board of governors, it was understood that the chief engineer of the Bureau of Reclamation would have to approve all final plans and specifications. Technical matters related to construction could be handled later; what mattered then was obtaining official approval from the Secretary so that work could proceed as quickly as possible.

Bureau of Reclamation officials were aware of the pact before its submittal to Ickes but had not yet approved it.84 They did comment upon the desirability of building a dam at Horseshoe in such a manner that the initial reservoir capacity of acre feet could be raised to over acre feet without requiring a completely new structure.85 Such a design would require a larger (and more expensive) base for the initial structure than would otherwise be required, but Reclamation was not concerned with the funding. The enlarged base would be sufficient to support later construction to raise the dam s height.

Technical and financial issues related to the Bureau s concern over the dam s ultimate height prompted little controversy in late or in The question of who could control the water stored in an enlarged Horseshoe reservoir, however, caused considerable delay in getting the Water Users Association and the Department of the Interior to approve the final wording of the agreement. To appreciate the reasons for this delay, it is necessary to recall the bitter rivalry that existed between the Salt River Valley Users Association and the Verde River Irrigation and Power District over water rights to the Verde River.

The Salt River Project had delivered a crippling blow to the hopes of the Verde District interests when the former group received permission to control operation of the Bartlett Dam, completed in the late The dam would impound much, but not all, of the Verde s flow. This left the struggling Verde River Power and Irrigation District with the slim hope that someday it might still find a way to use excess flood flow for its long-delayed plan to irrigate the Paradise Valley. The arrangement to have Phelps 83 Lin B. Orme, President SRVWUA, to Harold L. Ickes, Secretary of the Interior, 23 November NA, RG GAPR copy in SRP Archives. 84 For example, see W.E. Warne, Memorandum for the Commissioner, 11 November and C.A.

Fix, Memorandum for the Commissioner, 11 November both in NA, RG GAPR in SRP Archives. 85 Interest in increasing the height of the dam is first recorded in Harry G. Raschbacher, Memorandum to Director of Project Planning, 15 November NA, RG GAPR in SRP Archives. HORSESHOE DAM HAER No. AZ-24 (Page 28) Dodge build a dam at Horseshoe for the benefit of the Salt River Project attracted the opposition of the Verde River Power and Irrigation District. The prospect that Horseshoe Dam might be increased in height at some later date, however, raised the chance that the Verde District interests might gain control of water stored in the expanded reservoir.86 The Department of the Interior wanted to leave this possibility open in the contractor s wording.

While agreeing in principle to the diversion of Black River water, construction of the dam at Horseshoe and the compensation for lost power revenues, Interior officials also wished to have the agreement explicitly note that the new dam would be owned by the federal government and that no alteration or enlargement of the dam and reservoir could be made without the approval of the Secretary of the Interior. When government and association representatives met regarding the proposed contract at the end of they discussed at length a brief passage that the Department of the Interior wanted to include in the final agreement.

This passage stated: The Association agrees that said dam may be enlarged by the United States at any time and the additional storage capacity thus created disposed of by the Secretary of the Interior to the Association and others in such manner and to such extent as said Secretary may deem equitable.87 Ever on guard to protect its own interests, the Salt River Valley Water Users Association reacted predictably to the implication that others (i.e., the Verde River Power and Irrigation District) had as much right to the Verde River as the association did. The association recommended that the phrase be rewritten to note that [nothing shall] be construed as preventing the association from increasing the capacity of said reservoir at any time for the benefit of the Salt River Project.

88 Interior officials rejected this attempt to usurp federal control of the dam site and responded with a proposal that any additional storage capacity could be disposed of by the Secretary of the Interior to the Association or others in accordance with the provisions of the Federal Reclamation Act or upon other such terms as the Congress may prescribe. 89 The negotiations over the agreement s wording continued into January with attention focused on the others reference and on the clause concerning the right of Congress to prescribe other laws that might affect allocation of water storage along the Verde.

On January 10 the association s board of governors met to discuss wording that they would consider acceptable.90 Finally, on January 19 the governors approved a final agreement that: 1) excluded reference to any other parties interested in the Verde River; 2) granted the Secretary of the Interior sole power to dispose of any additional storage capacity; and 3) stipulated that no additions to, or alterations in said works shall be made without the written approval thereof by the Secretary of 86 Evidence of the Verde River Power and Irrigation District s opposition to the proposed Horseshoe Dam is given in Richard J. Coffey to Commissioner, Bureau of Reclamation, 22 December NA, RG GAPR in SRP Archives. 87 C.A. Fix, Memorandum for the Files, 4 January NA, RG GAPR in SRP Archives.

88 Ibid., p. 2. 89 Ibid., p. 2. 90 BOG, Volume 27, Minutes of 10 January HORSESHOE DAM HAER No. AZ-24 (Page 29) the Interior. 91 The final agreement stipulated that the original dam at Horseshoe be so designed and constructed that the same may be enlarged for the purpose of increasing the capacity of the reservoir created thereby to the extent of not to exceed an additional capacity of acre feet without the necessity for further or additional works in connection with the original foundation. 92 With this exception, the revised agreement was, in basic terms, identical to the original contract signed in November. With the governors approval of the final agreement, preparations were made quickly to hold an election so that the association shareholders could formally ratify the pact.

This election was scheduled for February 21, approximately one month after the board of governors approval of the pact but too late to meet the February 15 deadline that would have required Phelps Dodge to complete Horseshoe Dam by mid-February In February, as the Water Users Association was providing reassurances that operation of the Horseshoe Dam would not adversely affect water rights held by the Salt River Indian Reservation, it sought to obtain authorization from the Arizona State Land Department for both the Black River diversion and water storage at Horseshoe.93 On February 23 permits for both these activities were issued by the State Land Commissioners.94 By this time the association s shareholders had voted on the proposed agreement and, to the dismay of the board of governors, Phelps Dodge and the Defense Plant Corporation, had failed to ratify the approval with a three- quarters majority, as required by the association s bylaws.

Although shareholder votes were eligible to be cast, the election on February 21 attracted less than Of these, supported the agreement while were opposed.95 Despite the undeniable benefits that would accrue to the association, a minority of about 5 percent of the shareholders aided by an apathetic majority had successfully blocked ratification of the pact. A second election was hurriedly scheduled for April 4. This time proponents of the agreement were able to quadruple the number of approving votes to while those opposed were only able to increase their support marginally to votes.96 The initial failure at ratification can largely be attributed to voter apathy, despite daily news reports about the war effort and a great professed patriotism among Salt River Valley residents.

However, it also appears that at least some residents were apprehensive about the safety of the proposed Horseshoe Dam. In fact, S.O. Harper, Chief Engineer of the Bureau of Reclamation, wrote to the association in March acknowledging some objection among the water users to the construction of an earth and 91 BOG, Volume 27, Minutes of 19 January 92 Ibid., p. 5 of contract. 93 For evidence of the association s desire to reassure the Salt River Indian Reservation that their water rights would not be diminished, see Lin B. Orme to A.L. Watten (Chief Engineer for the Indian Bureau), 9 February NA, RG GAPR in SRP Archives. 94 Approval to build Horseshoe Dam is given in Permit No. dated 23 February Approval to divert water for the Black River for use at Morenci is given in Permit No. A-1853.

Also see Edwin T. Stewart to Greig Scott, 25 February all documents cited above are available in Box SRP Archives. 95 BOG, Volume 27, Minutes of 28 February 96 BOG, Volume 27, Minutes of 10 April HORSESHOE DAM HAER No. AZ-24 (Page 30) rockfill dam [at Horseshoe]. 97 The assurances by the Bureau concerning the stability of the foundations at Horseshoe to support an earth and rockfill dam apparently proved sufficient to allay major concerns over safety. The Horseshoe Dam as proposed did differ greatly from the five other storage dams operated by the association on the Salt and Verde rivers, a fact which only could have raised public apprehension. Ratification by the SRVWUA marked the last hurdle to gain authorization for Horseshoe Dam.

The next step lay in designing and building the massive structure. Chapter 4: Design and Construction of Horseshoe Dam Questions about the safety of Horseshoe Dam today seem unfounded, because as an earthfill structure it represented an ancient and oft-tested technology. The idea of building a dam by piling huge quantities of earth and/or rock across a streambed dates back thousands of years. Although earth and loose rock are susceptible to erosion or washouts by rushing water, both materials possess the advantage of ready availability.

The oldest known dam in the world is a small earth and rock structure in the Black Desert of modern-day Jordan that dates to circa The remains of much larger rockfill structure built circa in Egypt still survive, providing evidence of a major attempt to impound floodwater for irrigation and domestic supply.99 Since that time earth and rockfill dams have been built by numerous cultures throughout the world. Some of the most noteworthy early examples were built by the Romans, including structures in Spain built almost years ago that still provide water to local agricultural users.100 By the early twentieth century, earthfill and rockfill designs had become a major part of American dam technology.

Some of the earthfill dams, such as the Tabeaud Dam built in northern California in were built by scraping earth into horsedrawn dump wagons that hauled the material to the dam site for deposit in the structure.101 With the profusion of gasoline- and diesel-powered vehicles after World War I, this technique was adapted to motorized dump trucks supplemented by bulldozers to distribute the soil evenly across the dam site. The other major method of constructing earth dams involved hosing down hillsides with pressurized water and then transporting the resulting muck by pipes and flumes to the dam site where it was placed in the structure and the excess water allowed to drain away.

Known as hydraulic fill dams, these earth structures were popular in the early twentieth century, because they were relatively cheap 97 See S.O. Harper (Chief Engineer of the Bureau of Reclamation) to Lin B. Orme, 10 March letter included in BOG, Volume 27, Minutes of 15 March 98 This dam, located at the Jauas archaeological site, is described in Helm, Jawa, A Fortified Town of the Fourth Millennium Archaeology 27 pp. 99 The Egyptian Sadd el-Kafara Dam is described in Norman Smith, A History of Dams (Secaucus, New Jersey: The Citadel Press, pp. 100 The Romans built the 45'-high Cornalro Dam and the 36'-high Proserpino Dam in southwestern Spain in 100 A.D. They are described in Schnitter, Roman Dams, Water Supply and Management 3 pp.

101 Burr Bassell, Earth Dams: A Study, 2nd edition (New York: Engineering News Publishing Company, pp. HORSESHOE DAM HAER No. AZ-24 (Page 31) and easy to build. They were also susceptible to collapse due to problems in removing all the excess water, however, and this ultimately brought them into disfavor among engineers.102 Rockfill dams, usually with wood planks or a steel sheeting covering the upstream face, were built in many mountainous areas of the West during the late nineteenth and early twentieth centuries.

Perhaps the most famous of these were the English and Bowman dams in northern California, built in the to support gold mining operations.103 Rockfill designs were well suited to remote locations where little soil was available and where costs for hauling cement for a concrete structure were prohibitively high. The major problem with rockfill structures is that they are prone to settlement when placed under hydrostatic pressure, causing structural cracking in the upstream face. The reasons for popular misapprehension in the Salt River Valley concerning construction of an earthfill or rockfill dam were basically twofold. First, all the other major storage dams previously built for the Salt River Project were either masonry or concrete structures.

Although the Rio Verde Canal Company had proposed building a rockfill dam at Horseshoe in the the technology had not been used previously on a large-scale structure in the Salt River Valley. Moreover, the notorious failures of the rockfill Walnut Grove Dam in northern Arizona in and the Lyman Dam across the Little Colorado River in attracted an enormous amount of public attention in the region; years later these failures had not been forgotten.104 The second reason for concern over the safety of the proposed Horseshoe Dam relates to the perceived susceptibility of earth and rockfill dams to fail under a variety of conditions. The first, and most dramatic, of these is the failure by overtopping.

This occurs during times of heavy flooding when the capacity of the spillway and outlet valves proves insufficient to release enough water from the reservoir to prevent it from spilling over the top of the dam. As water runs across the dam s downstream face, it quickly causes the structure to erode and eventually collapse. Failure by overtopping can affect all types of dams, but whereas concrete designs are frequently able to withstand overtopping (in fact, many are built as overflow dams), earth and rockfill designs almost invariably fail when overtopped.

The collapse of the earthen South Fork Dam in Pennsylvania that precipitated the disastrous Johnstown Flood of was caused by overtopping, as was the failure of the Walnut Grove Dam and many others.105 Along with overtopping, the other main problem with earth and rockfill dams relates to water seeping through the structure and causing it to weaken and collapse. Seepage can result from water infiltrating the dam upwards from the foundation or from water entering the upstream face of the structure from the reservoir. Seepage is impossible to prevent completely in earth and 102 For more on this technology, along with some of its problems, see James D. Schuyler, Recent Practice in Hydraulic Fill Dam Construction, Transactions of the American Society of Civil Engineers 57 pp.

103 The English and Bowman Dams are described in James D. Schuyler, Reservoirs for Irrigation, Water Power and Domestic Water Supply, 2nd edition (New York: John Wiley and Sons, pp. 104 The collapse of the Walnut Grove Dam is described in Earl A. Zarbin, Roosevelt Dam: A History to (Phoenix: Salt River Project, pp. This account draws heavily on contemporary newspaper accounts and documents the public awareness of the disaster. 105 The collapse of the infamous South Fork Dam near Johnstown, Pennsylvania, is described in David McCullough, The Johnstown Flood (New York: Simon and Schuster, HORSESHOE DAM HAER No.

AZ-24 (Page 32) rockfill dams, but it can be controlled by the use of facing on the upstream side or by the construction of impervious core walls made of concrete or densely packed earth in the structure s interior.106 The key in designing and building a safe earth or rockfill dam lies not in using any complicated mathematical formulas, but rather in employing methods of proportioning the structure developed by centuries of empirical observations and making sure that good quality materials were to be placed on a solid foundation. The basic dimensions of stable earth and rockfill dams had been worked out by engineers well before the beginning of the twentieth century. In this context it is worth noting that earthfill and rockfill designs represent the massive tradition of dam building.

As such, these types of dams gain their stability by being so large, or massive, that the hydrostatic pressure exerted by the reservoir is insufficient to dislodge them from the streambed. The force of gravity pulling down on the mass of earth or rock is what provides resistance to the water pressure and keeps the dam in place. In contrast, designs that exemplify the structural tradition, such as concrete arch dams and buttress dams, rely upon the shape of the structure for stability, not merely the mass of material used. Earthfill and rockfill designs require a certain amount of material in order to provide enough mass to resist a given height of water. A builder who failed to satisfy this requirement would quickly learn of the deficiency after the dam collapsed.

In developing designs based upon such empirical methods, the basic shapes of earthfill and rockfill dams were largely determined by the physical characteristics of the materials. Both earth and loose rocks will take on a sloped, mound-like shape when formed into a large structure. If these slopes are too steep, the mound will tend to realign itself to a more natural (i.e., flatter) profile. The steepest angle at which a material will not slip under the normal forces of gravity is known as the angle of repose. Because of its density and other related properties, rockfill can be built along steeper slopes than earthfill, a fact that was well known by the twentieth century.

In noted dam theoretician Edward Wegmann wrote in his widely acclaimed book The Design and Construction of Dams: The profiles [cross-sections] of earthen dams are determined entirely by practical considerations. The general dimensions of the profile depend upon the materials used and the height of the bank, additional strength (i.e. width) being given to high dams.107 In his book Wegmann stipulated some basic design guidelines: the slope of the upstream face should have a length-to-height ratio of between 2:1 to while the downstream face could be steeper with a slope ratio of to He further indicated that the crest of the completed dam should be 10' to 30' in width and that the top of the reservoir should be allowed to rise no higher than 5' below the crest.

106 See William Creager, Joel Justin and Julian Hinds, Engineering for Dams, Volume III (New York: John Wiley and Sons, pp. and for listings of earth and rockfill dam failures. Also see Lars Jorgensen, The Record of 100 Dam Failures, Journal of Electricity 44 (15 March and 1 April pp. and 107 Edward Wegmann, The Design and Construction of Dams, 3rd edition (New York: John Wiley and Sons, pp. HORSESHOE DAM HAER No. AZ-24 (Page 33) Wegmann s design methodology for earthfill dams was largely reiterated in the book Engineering for Dams written by William Creager, Joel Justin and Julian Hinds.

These distinguished authors counseled: Precise and highly mathematical methods of design or analysis of the various features of earth dams are seldom justified because we know in advance that the assumptions which must be made are sufficiently wide so that no precision is justifiable. Consequently, the engineer whose function it is to investigate, design and construct will, in most cases, do well to confine himself to the simple, less precise methods of design and analysis.108 Engineers in the and conducted research into earthfill and rockfill designs in an attempt to make it more scientifically rigorous. The most useful advances in this area came in the testing of soils and rock to determine their strength, cohesiveness and porosity.

The last of these was important because it determined the amount of water a specific type of soil could absorb and the rapidity with which water could flow or seep through it. Among the most common methods of analyzing the stability of earth embankments was a technique first developed in Sweden in the early that came to be known as the Slip Circle or Dangerous Circle method of analysis.109 The name for this method derives from the fact that when earth embankments fail by having part of their volume slip to a lower elevation, they do so along a circularly shaped surface that is parallel to the upstream face of the dam. Slip circle analysis is particularly valuable in studying the behavior of earthfill with a high moisture content.

The utility of the method is limited, however, by the uncertainty of the physical properties of the earthen material used on a structure compared to the relatively small number of samples analyzed in the lab. By the early the science of soil mechanics had progressed to a point where engineers could test the quality of earth and rock samples with great theoretical precision. Yet the ability to transform this knowledge in to a more sophisticated design remained troublesome. In the book Earth and Earth-Rock Dams, it was noted that: No specific rules can be given for selecting the inclination of the outside slopes of the embankment [for an earth dam].

The general procedure is to make a first estimate on the basis of experience with similar dams and then to modify the estimate as required after making theoretical analysis.110 Like Wegmann had in the authors of Earth and Earth-Rock Dams listed standards for rockfill dam design. According to the volume, a length-to-height ratio of at least 2:1 was necessary for earth embankments, while rock fill could be safely piled up on slopes with length- 108 Creager, Justin and Hinds, Engineering for Dams, p. 109 Ibid. See pp. for an extended discussion of the theoretical state of earthfill dam design at the time the Horseshoe Dam was built. See pp.

for material on the circular slip method of analysis (also known as the Swedish Geophysical Method of Stability Analysis and the Dangerous Circle Analysis ). 110 James Sherard, Richard Woodward, Stanley Gizienski and William Clevenger, Earth and Earth Rock Dams (New York: John Wiley and Sons, p. 46. HORSESHOE DAM HAER No. AZ-24 (Page 34) to-height ratios of to In some cases it was acknowledged that rock could even be used safely for embankments with slopes of Rock, with its greater density and relatively jagged and irregular surfaces, is less prone to slippage and could be built using steeper slopes.

However, for both rock and earth, success lay in the use of good quality material and in the use of engineering techniques that would ensure the construction of a solid structure devoid of imperfections or irregularities that could facilitate excessive water seepage. When Phelps Dodge officials began planning the dam at Horseshoe in the fall of they sought the expertise of engineers already familiar with dam technology. Sensing the importance of retaining a firm that was known to the SRVWUA, Phelps Dodge hired Leeds, Hill, Barnard and Jewett, a group of consulting engineers based in Phoenix and Los Angeles, to handle the design and construction of the dam.

This firm had strong ties to the Salt River Valley (founding member Louis Hill had served as the Reclamation Service s supervisory engineer for the construction of Roosevelt Dam and the early Salt River Project), and in had prepared an analysis for the Water Users Association entitled Economic Survey of Salt River Project. 112 The person responsible for this report was Louis Hill s son, Raymond Hill. In the autumn of Hill was given engineering responsibility for the Horseshoe Dam; Phelps Dodge played essentially no further role on the structure except to finance its construction. Although Hill did not discuss development at Horseshoe in his report, others had written extensively about the site and its geology.

A report by the Verde River Irrigation and Power District on dam sites along the Verde River devoted considerable attention to Horseshoe, and in the Bureau of Reclamation had undertaken its own study of the site in anticipation of building a storage dam for the Power District.113 This latter report presented three designs multiple arch, concrete gravity and earthfill for Horseshoe, reporting the site as somewhat unsuited for an earth dam because of its location in a short canyon with a narrow ridge.114 The conditions affecting dam building were different in than in the previous decade, however, and Hill certainly would not have been constrained by such a judgement when he set out to analyze the problem on his own.

In a circa report prepared by the engineering staff of the SRVWUA describing the design of Horseshoe Dam, the remote location of the site and the shortage of labor during the war are referred to as major reasons why a concrete design of any type was rejected. All work [on the dam] would have to be done during a period of labor shortage, cost of hauling [cement] would be great, and other factors would have made the construction cost of any concrete dam excessive.115 111 Ibid., p. 46. 112 BOG, Volume 26, Minutes for October 113 See Hyde Forbes, Verde River Irrigation and Power District, Arizona, Report on the Geology of the Reservoirs and Damsites to be Utilized in the Proposed Development of the Verde River, Arizona, March pp.

and Bureau of Reclamation, Verde Project-Preliminary Studies of Storage and Diversion Dams, Both of these reports are in the National Archives, Denver Branch, Record Group Engineering and Research Center Project Reports Box [hereafter this source is cited as NA, Denver, RG ERC, Box _] 114 Ibid. 115 No author, Design of Horseshoe Dam and Spillway, circa p. 9, file No. H-A4 SRP Archives. HORSESHOE DAM HAER No. AZ-24 (Page 35) This same report indicates that interest in excavating the spillway for the dam across the top of the western abutment necessitated plans for making a deep wide cut into bedrock.

The rock excavated for a large spillway would be available for use in the structure of the dam, apparently prompting the desire to build a rockfill dam.116 At the end of October Hill consulted with John Savage, the Bureau of Reclamation s Chief Dam Design Engineer, and, at the latter s suggestion, two separate plans for Horseshoe were developed.117 The first was a rockfill dam with an impervious concrete slab built across the entire upstream face. The second was a composite structure with an impervious core of dense earthfill built across the center of the dam site and a thick pile of rockfill placed along the upstream and downstream sides of the dam.

Between the earth core and the rockfill there was to be a thin layer of sand and gravel (referred to as fines ) which would help bond the earth and rock sections into a relatively monolithic mass. The idea of building such a zoned rockfill dam with an earth core did not represent a radical innovation in the field of dam technology. The technique had been used in several dams previously, the most noteworthy being the 260'-high Nantahala Dam in North Carolina, and Justin, Creager, and Hinds book Engineering for Dams specifically discussed this method of construction.118 Although the proposed design for Horseshoe did not constitute a dramatic step in dam building, it nonetheless represented a substantial contribution to the development of earth core/rockfill dams.

In November the two designs were submitted to the Bureau of Reclamation for formal approval.

Following analysis using the slip circle method and a comparison of the dams with previously built structures, the Bureau reported that both would be satisfactory given that good quality methods were used and placed in accordance with sound engineering practice.119 At this point the dam designs were geared toward a reservoir with an ultimate storage capacity of In December and January the Department of Interior negotiated with Phelps Dodge and the SRVWUA for construction of a dam that could be substantially enlarged at a later date.120 By early January new designs acceptable to the Bureau had been developed that maintained the basic configuration of the original designs but in an enlarged form.121 In February, even before the shareholders of the Water Users Association had ratified the Horseshoe/Black River project, the two designs were let for competitive bid.

The rockfill design called for an upstream face at an angle of 45 degrees (a height-to-length ratio of and downstream face with a steep height-to-length ratio of The entire upstream face was to be covered by a reinforced-concrete slab. The earth core/rockfill design included a central rolled earthfill section 35' wide at the crest and over wide at the foundation. This core was designed along a steep slope at the front and a slope at the back. The section of 116 Ibid., p. 10. 117 Ibid., p. 11. 118 For more on various examples of earth core/rockfill dams, see Justin, Creager and Hinds, Engineering for Dams, pp. 119 Memorandum from Walker to Keener, 27 November in Federal Records Center, Denver, Accession No.

115-62-A-473, Location Box Horseshoe Dam Folder [hereafter cited as Denver, Horseshoe Dam]. 120 See memorandum concerning telephone call between Raymond Hill and Riter, 15 December Denver, Box Salt River Folder. 121 See S.O. Harper to Raymond Hill, 8 January Denver, Horseshoe Dam Folder. HORSESHOE DAM HAER No. AZ-24 (Page 36) fines separating the earth core and rockfill was stipulated to be 2' thick at the crest and widening to a maximum of more than 18' at the foundation. The rockfill along both the upstream and downstream faces was sloped at a height-to-length ratio of At the base of the upstream face, however, the rockfill was to be widened an extra 80' in anticipation of future expansion.

No plans were made for a reinforced-concrete slab across the upstream face, but the design called for a concrete cutoff wall approximately 40' high and about 3' thick that would extend into the bedrock foundations and run along the centerline of the earth core section.122 Both designs were to use the outlet tunnel drilled by the Rio Verde Canal Company in the and reinforced with concrete in At the tunnel s inlet, a 120'-high reinforced-concrete tower would be built to house a trash rack and cylindrical gate. The designs also called for construction of a 320'-wide reinforced-concrete spillway across the western abutment. Sized to expel a maximum of cubic feet of water per second, the spillway s capacity was almost twice that of the largest known flood on the Verde.

The spillway was designed in anticipation of movable gates being placed across the structure as a means of increasing the storage capacity of the reservoir. This required excavation to a depth almost 50' below the top of the abutment. Perhaps the most noteworthy aspect of the spillway design was that it did not include a lengthy concrete apron to direct the water for several hundred feet downstream before re-entering the streambed of the Verde River. Instead, the Horseshoe spillway featured a tee-section lip that would propel water in a cascade onto a bedrock channel that would then carry it back to the Verde.

To ensure that the overflow would be concentrated in the center of the spillway, the design also featured a bowl-shaped floor and sloped side walls.123 Sheltered by this lip on the dam s downstream side was a narrow concrete walkway with a concrete parapet wall. This walkway was incorporated into the design to facilitate sheep herding across the dam while water was being spilled over the apron. Bids on the two designs were opened on February 21, but they were not announced for several more weeks.124 In April bids of the six respondents were published in Western Construction News.125 Bidders included the Mittry Brothers Company of Los Angeles, and a joint proposal by Morrison-Knudsen Company and W.A.

Bechtel Company, the latter two firms being a part of the famous Six Companies Incorporated consortium that had built Hoover Dam on the Colorado River. The bids on the earth core/rockfill design ranged from a low of (Mittry Brothers) to three that exceeded million. The rockfill design prompted a low bid of (also by Mittry Brothers), while all the others exceeded million, the highest being million. No firm submitted a bid for the rockfill design that was lower than 122 Data on the designs are taken from Design of Horseshoe Dam and Spillway, circa SRP Archives; Work Starting on Earth and Rock Fill Dam on Verde River in Arizona, Southwest Builder and Contractor 104 (7 July pp. and Lawrence L.

Lee, Arizona Earth and Rock Fill Dam Rising on Site Contemplated Fifty Years Ago, Western Construction News 20 (September pp. 123 Ibid. 124 Design of Horseshoe Dam and Spillway, p. 14. 125 Bids for Horseshoe Dam were reported in Arizona-Maricopa County-Phelps Dodge-Earth & Rock Fill, Western Construction News 19 (April p. Complete breakdowns of the three sets of bids were provided in this report. HORSESHOE DAM HAER No. AZ-24 (Page 37) their bid for the earth core/rockfill design. It was clear that the latter structure would be more economical to build. Logically, the low bid by Mittry Brothers should have been accepted so that construction could have been started as soon as possible.

The failure of the SRVWUA to ratify the project in February delayed the contract award for several weeks, however. By this time the bids submitted in February were no longer binding, and it was necessary to approach several of the contractors for a resubmittal of bids on the earth core design.126 When the Mittry Brothers refused to resubmit their earlier offer, the contract was awarded to the joint venture comprised of L.E. Dixon Company and the Arundel Corporation of Baltimore. The final accepted bid was for almost more than the low bid submitted in February.127 The first work undertaken at Horseshoe involved cleaning out the old Rio Verde Canal Company tunnel and lining the passageway with concrete.

This project was not part of the main dam contract let to the Dixon & Arundel group and was handled by Vinson & Pringle, a Phoenix- based outfit, for a lump sum of Work on rehabilitating the tunnel started early in January and wrapped up by the end of May. As part of this, the contractors erected a small temporary construction camp for workers on the west side of the Verde River about downstream from the dam site. This camp was later enlarged for use by the Dixon & Arundel work crews. Because the work completed in the had been well-surveyed and well-built, little was needed to straighten or realign the 730'-long passageway. Instead, the contractors focused on cleaning out fifty years of rock and sand that had accumulated in the tunnel during times of flooding.

It was initially hoped that this debris could be removed by washing it from the tunnel outlet using jets of pressurized water. However, because the tunnel is very gently sloped, this method proved ineffective to expel the rock and sand. As a substitute measure, a gasoline- powered bulldozer was used to remove the debris deposits by pushing them out the portal of the 14'-wide passageway. Once this was finished, work crews chipped away protrusions from the tunnel walls to make sure that all interior surfaces were smooth and regular. The final part of the contract involved construction of a concrete lining encompassing the entire length of the tunnel.

This was accomplished by building wooden forms in 10' sections and then progressively filling them with concrete pumped in from a mixing plant located near the upstream portal. The bottom of the tunnel was built using a slightly curved cross-section to help ensure that the water would flow freely; the side walls were vertical for a height of 5' and above this the roof of the tunnel was built with a 6' radius semicircular cross-section. The floor and walls were poured first and, after a few days of hardening, the forms were removed and moved further down the tunnel to be used again. Once hardened, the side walls were used to support the formwork for the top of the tunnel. Except for the very top section of the tunnel arch, concrete 126 Design of Horseshoe Dam, pp.

127 Lee, Arizona Earth and Rock Fill Dam, p. 92. 128 All information on the rehabilitation of the tunnel is taken from Lawrence L. Lee, Arizona Tunnel Rehabilitated, Western Construction News 19 (September pp. HORSESHOE DAM HAER No. AZ-24 (Page 38) was pumped in the from the mixing plant and placed the same way as with the bottom section of the lining. The top of the tunnel wall was filled in by a pressurized method of application in which a rich cement mixture known as gunite was sprayed on the rock surface. When completed, the tunnel lining had a minimum thickness of 6" in all locations; it formed a smooth concrete passageway with a constant width of 12' at the base and a constant height of 12' along the centerline.

In total, the tunnel lining required cubic yards of concrete and gunite to construct. The tunnel contract also included construction of the entry and exit portals. The downstream portal was relatively simple in design and involved building a concrete bulkhead around the outlet to help prevent any localized rock erosion. This bulkhead provided a 7' x 8' rectangular opening that was directly connected to the tunnel. At the upstream end a special concrete structure was erected to connect the tunnel with the intake tower. This connecting section was curved in shape and closely resembled draft tubes used in hydroelectric powerhouses to join together penstocks and hydraulic turbines.

The top of the curved intake structure was built with a flat horizontal surface designed to support the intake tower that would be erected later. The intake structure received water flowing straight down and funneled it through a 90-degree curve so that it entered the tunnel proper in a horizontal direction. Though not part of the Vinson & Pringle contract, the intake tower was an integral part of the tunnel/discharge system. Built while the main part of the dam was under construction during late and the intake tower provided support for a valve system devised to control water releases through the tunnel.129 The tower consists of scores of circular-shaped concrete segments, precast at the dam site and assembled above the tunnel entrance using heavy wooden falsework.

The circular segments were then joined together permanently when 6'-tall reinforced-concrete struts were poured in place to form a monolithic structure. Later, the openings formed by the vertical struts and the horizontal circular segments were filled in using removal steel trash racks. The tower supports a 9'-diameter cylindrical steel plug, or gate, that can be raised or lowered to control the release of water. When lowered into a base at the top of the draft tube section, this seals off the tunnel. By raising the cylindrical gate, operators can control the discharge of reservoir water into the tunnel. Maximum release of water can be accomplished by raising the gate a height of 4'.

Control of the cylindrical plug is handled by a steel cable hoisting mechanism attached to the top of the tower; vertical movement of the gate is facilitated by the use of a 92,500-pound counterweight connected with a 12-ton electric hoist motor. Construction of the intake tower comprised an important part of the Dixon & Arundel contract. The effort expended in building the concrete tower was relatively minor compared with the work required for the dam proper, however. By the time the project had received final approval from the Water Users Association and the contract was awarded to Dixon & Arundel, any hope for finishing the dam by early had long since vanished.

Originally the Dixon & Arundel team had planned to hold off any work at the site until September and would not start excavating 129 Data on the construction of the intake tower is taken from Lee, Arizona Earth Rock Fill Dam, p. 94. HORSESHOE DAM HAER No. AZ-24 (Page 39) the dam s foundations until December.130 During the summer, however, the contractors accelerated their schedule in an attempt to get the foundation cleared before the end of so that work on placing the earth core and rockfill could begin by early Among the first tasks required was construction of a camp to house the workers for the duration of the project.

Apparently the housing facilities built on site by Vinson & Pringle were enlarged for the new camp, and they proved suitable as temporary quarters.131 None of the available reports and technical articles describe the number of laborers employed in building the dam, nor is any indication given as to their place of origin or ethnic background. Given the wartime labor shortage that prompted selection of an earth core/rockfill design, it is doubtful that the work force exceeded 100 men at any one time, and even this may be a generous estimate. Most workers operated mechanized equipment such as bulldozers, dump trucks or shovels and dragline excavators, and little hand labor was necessary.

Most workers were probably drawn from the greater Phoenix area, although it is possible that some came to Arizona from out-of-state because of previous dealings with Dixon and/or Arundel. Although skill was necessary to handle the heavy equipment, such skills could be learned by a willing labor force without much difficulty. At the work site, the greatest problems affecting construction probably related to the intense heat that can affect any sustained outdoor activity in central Arizona. No reports have been found to indicate that the heat seriously disrupted construction progress. Rattlesnakes infested much of the dam site, however, and this aroused considerable concern.

In fact, during a special hunt undertaken early in construction, seventeen diamond back vipers were killed in a single afternoon.132 Excavation work on the upper elevations of the abutments started in late August by mid- October work was underway in clearing out the lower elevations of the streambed.133 It was not considered necessary to excavate the entire area under the dam down to bedrock. Instead, only the foundation of the central earth core was taken down to bedrock in order to minimize seepage through the interior of the structure.

After clearing out small trees, shrubs and other brush from the contact area of the earth core, most of the overburden soil was removed by spraying it with pressurized water and then allowing most of the resulting muck to flow downstream beyond the dam site. Known as sluicing , this process involved drawing gallons of water per minute out of the Verde River via an electric-powered pump and carrying it by hose to the top of the dam site. From there the water was directed by a movable nozzle toward the overburden until bedrock was uncovered. The sluicing proceeded downward from the top and eventually enough debris accumulated in the lower streambed that it was necessary to use large shovels and bulldozers to load it into dump trucks for removal.

130 Design of Horseshoe Dam and Spillway, SRP Archives. 131 In all of the top three original bids, the prospective contractors (including L.E. Dixon) indicated that only would be spent on camp construction. See Western Construction News 19 (April p. 132 This special problem is described in Rattlesnakes Add to Hazards of Arizona Dam Construction, Western Construction News 19 (July p. 87. 133 Data on excavation activity is taken from Lee, Arizona Earth and Rock Fill Dam, pp. and from Sluicing of Abutments, circa unsigned report in file no. H-A4 SRP Archives. HORSESHOE DAM HAER No.

AZ-24 (Page 40) As part of the foundation excavation, a small diversion channel was blasted along the east side of the streambed.134 Excavated with the help of over pounds of dynamite, this channel was dug after completion of the sluicing operations. Some long and 30' wide, with a height of about 9', the diversion channel was designed to carry floods of up to cubic feet per second In concert with the tunnel, it would provide a means of diverting water around the site during the early stages of construction. In March the channel carried a flood of more than cfs and helped protect the practically complete structure from the destructive effects of erosion. In addition, about half of the cubic yards of rock excavated for the channel was suitable for placement in the main structure of the dam.

Washing the bedrock surface with pressurized water successfully removed the earth and loose rock from the foundation area. Once the bedrock surface was cleaned, however, the contractors found that substantial quantities of water were flowing from the foundation and accumulating in the lower depths of the stream gorge. Equaling almost 500 gallons per minute, the subsurface flow threatened to disrupt both the construction process and undermine the dam s stability. To cope with this problem, a two-phase plan was put into effect. The first phase involved concentrating the subsurface flow so that it could be readily pumped from the foundation area.135 They did this by building two 14' concrete walls on the bedrock along the upstream and downstream edge of the earth core section of the dam.

Pits were dug adjacent to these retaining walls to concentrate the seepage further so that it could be readily pumped from the foundation area. The other means of handling the seepage involved drilling more than 100 holes between and 25' deep across the surface of the foundation.136 Approximately in diameter, these holes were cleaned out using compressed air and then filled with cement grout applied under pressure of several hundred pounds per square inch. By the grouting was a common engineering technique employed to strengthen foundations and reduce subsurface water flow. By forcing cement group deep into the foundations it was possible to fill in cracks in the bedrock, thus eliminating the passageways through which underground water flowed.

At Horseshoe over sacks of cement were grouted into the foundations during November and December Before placement of the earth core began, two additional procedures were necessary to prepare the foundation. Conceived as part of the original dam design, the first involved construction of a concrete cutoff wall along the centerline of the earth core.137 This wall extended into the foundation and rose to a height of 10 above the bedrock surface. It was 3' thick at the base and tapered upward to a minimum thickness of The second procedure involved construction of an 8'-thick concrete blanket (or slab) on top of the very deepest section of the foundation. Referred to as the gorge, this area was approximately 60' wide and long.

It occupied the 134 Construction of the diversion channels is described in a section entitled River Diversion in the report Sluicing of Abutments, Archives). 135 The process of pumping out the foundation is described in Foundation Preparation, circa unsigned report in file no. H-A4(1945.03), SRP Archives. 136 Grouting work is described in a section entitled Drilling and Grouting in Sluicing of Abutments and in Foundation Preparation Archives). It is also described in Memorandum from O.L. Rice, A.W. Simonds and J.A. Haines to Acting Chief Engineer, January 12, Denver, Horseshoe Dam Folder. 137 The cutoff wall and concrete blanket are described in Lawrence L. Lee, Horseshoe Dam, pp. in History of the Salt River Project for the Period January 1, to December 31, HORSESHOE DAM HAER No.

AZ-24 (Page 41) very bottom of the streambed. Because the extensive grouting had still not been able to eliminate all foundation seepage, it was considered advisable to encase the bottom of the gorge in concrete as a precaution against any possible erosion of the earth core. By December the foundation had been cleared and grouted. In addition, construction of the concrete cutoff wall and blanket was complete. At this time work started on placement of the earth core, the rockfill, and the transition zone of gravel and fines that lay between the two major structural sections. The first material put in the dam proper was a small berm of rockfill at the extreme upstream end of the dam.

This 30'-high berm served as a cofferdam to help protect the site from floods by directing water into the diversion channel. Eventually, both the earth core and rockfill sections would be placed simultaneously but, once the initial rockfill berm was in place, most early construction activity involved placement of the earth core. After the foundation had been cleared and grouted and the gorge covered with concrete, the Dixon & Arundel crews were able to start placing the earth core in mid-December Borrow pits (a strange name, given that the borrowed soil was never returned) were opened up on the west bank of the Verde about downstream from the dam site, and excavated dirt was transported by motorized dump trucks.

The soil in the pits was described as a brown, sandy loam with a density of approximately 100 pounds per cubic foot. Tests undertaken by the engineering firm of Dames and Moore indicated that samples had a percolation rate of about feet per year, meaning that any seepage through the core would proceed at a rate of about 1' every twenty years. As constructed proceeded, the quality of the earth wavered with some material from the pits tested at a percolation rate of close to per year. Care was taken to exclude most of this porous, sandy soil from that placed in the core. To accomplish this, the borrow pits were elongated along the upper levels of the river bank in order to allow excavation of the least porous loam available.

Construction of the earth core necessarily started in the deep gorge section and then proceeded upward. Soil from the borrow pits was delivered by dump trucks and deposited at the bottom of the earth core section. The loose dirt was then compacted to increase its density and ensure that it would be relatively impervious. In areas close to the concrete cutoff wall adjacent to the bedrock abutments, small compressed air-powered tampers operated by one or two men were used to compact the soil. In the main areas of the core, 5'-diameter roller drums filled with water (to increase their weight) were pulled by bulldozers over the surface to compact the soil.

These rollers had 2"-deep steel knobs known as sheep feet attached to them to mix the soil as it was being compacted.139 138 Data on placing the earth core is taken from Lee, Arizona Earth and Rock Fill Dam ; Lee, Horseshoe Dam ; Memorandum from O.L. Rice, A.W. Simmonds and J.A. Haines to Acting Chief Engineer, January 12, Memorandum from J.A. Haines to Chief Engineer, March 2, Memorandum from J.A. Haines to Chief Engineer, June 29, Memorandum from J.A. Haines to Chief Engineer, September 25 These latter four memos are in Denver, Horseshoe Dam Folder.

139 In the deep sections of the gorge, there was insufficient data to maneuver the large rollers so compaction was handled by welding small knobs to the treads of the caterpillar tractors and then driving the tractors back and forth between the walls and the gorge. HORSESHOE DAM HAER No. AZ-24 (Page 42) Prior to compaction, the dirt taken from the pits was frequently sprinkled with water to provide for more cohesion in the core. Bulldozers spread the dirt over the surface in 9"-thick layers that were then subject to compaction under the sheep-foot rollers. For areas compacted by the compressed air tampers, the soil was spread in 4" layers. Once the construction process was put in place, the work of building the core wall proceeded through the end of without any serious incidents.

The only major problem concerned the excavation of some highly porous soil, but this was readily obviated by extending the size of the borrow pits. The construction of the earth core was accompanied by the placement of fine sand and gravel transition zones along the upstream and downstream edges of the core. This zone provided a structural barrier between the earth core and rockfill and averaged about 10' thick. Material for the zone was excavated from the river channel immediately downstream from the dam site and delivered via dump truck. The material was dumped in a wet, saturated condition that allowed bulldozers to compact it into a very dense fill. 140 During construction of the dam, the size of the fine transition zones was enlarged beyond that called for in the original design.

The outer slopes of the two transition zones were flattened slightly to a length-to-height ratio of By widening the two zones it became possible to reduce the amount of rockfill necessary in the structure. This reduction was prompted after early excavation of the spillway indicated that much of the rock being removed was too weak and soft for inclusion in the dam.

Consequently, by increasing the size of the transition zone, it became possible to minimize the amount of additional rock quarrying necessary to build the main structure.141 The only other substantive change to the original design occurred relatively late in construction when, in August the Bureau of Reclamation recommended that the upper levels of the earth core be widened slightly and the outer slopes of the rockfill be flattened slightly. This minor change was made not because of any question regarding the stability of the structure as designed, but in anticipation of the future raising of the dam.

142 All the material for the main sections of rockfill was originally to have been taken from the spillway excavation, but when much of this rock proved inferior in quality, supplemental quarries were opened a short distance southwest of the lower spillway.143 The rockfill varied in size from small spalls about 8" in diameter to large boulders 1-to-2 cubic yards in volume. Dump trucks delivered the loose rock to the dam site; it was then bulldozed into layers between 13' and 15' thick. These layers of loose rock were further compacted by pressurized water. This latter procedure insured that gaps between the larger rocks were filled by smaller stones, thus 140 Construction of the transition zone of fines is described in Memorandum from J.A.

Haines to Chief Engineer, 29 June Denver, Horseshoe Dam Folder. 141 The decision to increase the size of the transition zone is described in Design of Horseshoe Dam and Spillway, Archives], p. 17. 142 The widening of the upper section of the earth core and the flattening of the rockfill are described in Design of Horseshoe Dam and Spillway, p. 18 Archives]; and in Memorandum from J.A. Haines to Chief Engineer, 25 September Denver, Horseshoe Dam Folder. 143 Construction of rockfill is documented in Lee, Arizona Earth and Rock Fill Dam, and in Memorandums from J.A. Haines to Chief Engineer dated 2 March 29 June and 25 September and in a Memorandum from J.A. Haines, O.L. Rice and A.W. Symonds to Acting Chief Engineer, dated 12 January all in Denver, Horseshoe Dam Folder.

HORSESHOE DAM HAER No. AZ-24 (Page 43) creating a dense, tight fill. The process of placing the rockfill presented no major challenges, and it proceeded without incident throughout Any potential problem posed by the poor quality of rock excavated from the spillway proved short-lived, as suitable rock was soon obtained from quarries located close by the dam site. Because of the disaster that would result if water ever overtopped the dam, care was taken to build an ample spillway. Measuring across, the lip of the spillway reached an elevation of above sea level while the crest of the earth core/rockfill structure topped out an elevation of Raymond Hill sized the spillway so that under a head of 40' (i.e. elevation it would discharge cubic feet per second.

The contractors excavated approximately cubic yards of rock for the spillway opening, of which (about 75 percent) proved suitable for use in the structural rockfill. Once the complete length of the spillway reached an elevation of the area surrounding the crest was grouted with pressurized cement. Just as with the grout holes penetrating the earth core, the purpose of this work was to insure solid bedrock free of troublesome fissures capable of leaking. More than eighty such spillway grout holes were drilled up to 40' in depth. When completed, this grouting required more than sacks of cement. Upstream from the spillway crest the bedrock was left uncovered, but below the crest a substantial concrete channel was constructed to divert the water downstream.

Aggregate for the spillway s concrete was taken from streambed deposits in the Verde about downstream from the dam site. After crushing and sifting at a special plant adjacent to the deposits, this aggregate was hauled upstream for use in a concrete mixing plant built near the spillway.145 Concrete from the mixing plant was delivered to the various parts of the spillway by trucks that placed it within the wooden formwork. This concrete was of very high quality (averaging a strength of over pounds per square inch after hardening for twenty-eight days), and, in general, construction of the spillway presented no problems.

When the contractors began pouring concrete in spring however, some protests were made by the Water Users Association concerning the sharp lower lip of the spillway that was designed so that water would drop a distance of about 15' onto a channel of exposed bedrock. Both Raymond Hill and the Bureau of Reclamation strongly defended the original design, and the minor controversy was soon put to rest.146 This design is quite distinctive in that the lower lip of the spillway is built to carry a road that extends across the dam s downstream face and up to the crest at the east end of the structure. To provide access across the spillway during periods of flooding, a walkway was erected underneath the lip to take the place of the roadway.

In this way, it was always possible for a man to reach the top of the outlet tower regardless of any flooding. 144 The design and construction of the spillway is described in Lee, Arizona Earth and Rock Fill Dam, Design of Horseshoe Dam and Spillway, pp. and Foundations Preparation, pp. [the latter two reports are in SRP Archives]. 145 This process and the quality of the resulting concrete is described in Concrete Production and Testing, unsigned report, circa SRP Archives. 146 The spillway controversy is described and addressed in Raymond Hill to Salt River Valley Water Users Association, 6 April and memorandum from McConaughy to Keener, 3 April both documents in Denver, Horseshoe Dam Folder. HORSESHOE DAM HAER No.

AZ-24 (Page 44) By the end of practically all work on the Horseshoe Dam was complete. The contractors finished early the next year in accordance with the terms of the project agreement.147 Water was impounded in the spring of and the dam began active service for the Water Users Association. In the end, the deepest foundations of the dam extended down to above sea level while the crest topped out at an elevation of The foundations for the bulk of the structure were at the level, prompting most descriptions to list the dam s height at approximately The structure contains approximately cubic yards of rolled earthfill, cubic yards of fines and cubic yards of rockfill.

In addition, cubic yards of concrete were poured in the cutoff wall and the spillway, while slightly more than 25 tons of steel were used to reinforce the intake tower and spillway design.149 With the dumping of the last load of rock onto the Horseshoe Dam in early the water storage project envisaged by the Rio Verde Canal Company fifty years earlier had finally become reality. Chapter 5: Conclusion After Horseshoe Dam began impounding water in the spring of some operational difficulties were soon experienced with the mechanism used to control water releases through the outlet tunnel. The opening was designed to be closed by a heavy, 9'-diameter cylindrical steel plug housed within the intake tower.

Dam tenders would lower the plug into the top of the tunnel opening to cut off water releases from the reservoir; the plug would be raised to a maximum height of 4' to release flow from Horseshoe Reservoir. The system functioned adequately as built, but the bolted steel walls of the partially hollow plug suffered from excessive vibration when the outlet was partially opened. Although no permanent damage resulted from this structural aberration, the steel walls and bolts of the plug were strengthened the following year.150 The outlet system has functioned properly since then. In fact, the operation of the dam as a whole has been remarkably problem-free during the past forty-five years.

Within a year of the first water impoundment at Horseshoe, the Salt River Valley Water Users Association initiated efforts to increase the reservoir s capacity. Ever mindful of the possibility that other groups might wish to enlarge the Horseshoe Reservoir for their own purposes, the association sought a way to use all flood flow from the Verde within the confines of the Salt River Project and away from the Paradise Valley. As a result, in November the association signed an agreement with the City of Phoenix calling for the city to pay for construction of movable spillway gates at the Horseshoe in exchange for rights to use the water 147 In September construction was described as 75% complete. See Lee, Arizona Earth and Rock Fill Dam, p. 96.

148 For example in a brochure printed by the Salt River Project in the early entitled Major Facts about the Salt River Project the height of Horseshoe is listed as p. 32. 149 The volumetric data on material used in the Horseshoe Dam is taken from Lee, Arizona Earth and Rock Fill Dam, p. 96. 150 Complete discussion of the early problems and remedies associated with the outlet system is described in Whiman, Structural Report on the Cylinder Gate at Horseshoe Dam, October report in file no. SRP Archives. HORSESHOE DAM HAER No.

AZ-24 (Page 45) stored in the enlarged reservoir.151 This arrangement appealed to the Water Users Association, because Phoenix lay entirely within the boundaries of the Salt River Project, thus ensuring that the city s share of the Verde would always be used in areas already part of the association s service area. The city s allotment was to be used primarily for domestic water supply to help support urban development and commercial growth. Such development could only increase the value of other land holding in the Salt River Valley. For this reason, members of the association supported the spillway gate proposal. In accordance with the original contract for Horseshoe Dam, approval was needed from the Secretary of the Interior for construction of the spillway gates.

During and early the Interior Department bureaucracy considered the advisability of the plan. Objections were raised by the surviving remnant of the Verde River Irrigation and Power District, but once again this small group could muster only a fraction of the political influence wielded by the Water Users Association.152 More serious consideration was given to the impact that an enlarged Horseshoe Reservoir might have on plans to use the Verde River as a conduit for water diverted from the Colorado River upstream from the Grand Canyon.153 In such a scheme, water from the Colorado was to be carried through a lengthy tunnel to the upper reaches of the Verde watershed.

From there it would flow by gravity to Central Arizona after being stored in reservoirs located along the length of the Verde. Horseshoe Dam had been designed to be enlarged to accommodate the potential storage of water diverted from the Colorado River. Money spent to build spillway gates would be wasted if the dam was subsequently extended. The question of whether or not the Colorado-to- Verde diversion would ever prove feasible was soon rendered moot, however, in the face of larger battles between California and Arizona over water rights on the Colorado River.

By May the City of Phoenix had advanced to the association to pay for the development of final plans for the spillway gates; soon thereafter the Department of the Interior also gave its approval for building the gates.154 Design for the gates was contracted to Leeds, Hill and Jewett successor to Leeds, Hill, Barnard and Jewett with Raymond Hill again acting as project manager. The purpose of the gates was to provide a means to block the spillway opening incrementally to raise and control the reservoir level. The movable spillway gates more than doubled the capacity of Horseshoe Dam, from acre-feet to slightly more than acre-feet.

151 For a copy of the contract signed on 22 November see BOG, Volume 30, Minutes for 16 November The contract called for the city to pay toward the cost of spillway gates; any expense above this amount was to be assumed by the water users association. 152 Evidence of the Verde Irrigation and Power District s opposition to the spillway gates is found in E.W. Michael to Julius King (Secretary of the Interior), 26 May Denver, Horseshoe Dam Folder. 153 For example, see Straus to E.A. Mority, 26 January and E.A. Mority to Michael Straus, 24 June both in Denver, Horseshoe Dam Folder.

Attempts to build the so-called Colorado-Verde Project using state funds continued into the For a description of the project see a circa promotional pamphlet published by the Colorado-Verde Association entitled Water for Arizona [available in the Arizona Collection, Arizona State University Library, Tempe]. 154 See BOG, Volume 32, Minutes for 23 June Final approval for the spillway gate contract came in September see BOG, Volume 32, Minutes for 7 September HORSESHOE DAM HAER No.

AZ-24 (Page 46) The spillway is closed off by three Tainter gates, each a little more than long and supported by two reinforced-concrete piers anchored to the base of the spillway.155 The 33'-high Tainter gates consist of riveted-steel plates shaped with a slightly curved cross section that extends towards the reservoir. The gates attach to two steel frames that are each connected by a trunnion pin to the front of the reinforced-concrete piers. At the downstream end of these hinged steel frames are massive concrete counterweights designed to balance the weight of the gates around the hinges. This feature means that very little motive power is necessary to raise and lower the gates. A steel walkway extends across the top of the piers to provide access for cleaning, repair and maintenance.

Completed in the fall of at a cost of the gates at Horseshoe were soon tested under field conditions and were demonstrated as well-suited to their task.157 The balanced mechanisms could be raised or lowered mechanically by an operator, but they were also designed to function automatically without human assistance. For example, during times of heavy flooding when the reservoir was rapidly rising above the level of the spillway crest, the gates were designed, through use of special sensor devices that monitored reservoir levels, to open automatically. Once the reservoir levels had stabilized, the gates were automatically lowered to conserve as much of the floodwaters as could be safely impounded behind the dam.

The automatic operation of the gates could be superseded by operator intervention in times of emergency, but for the most part the gates are self-regulating. The Phelps Dodge facility at Morenci remains operational, but the original agreement allowing the corporation to divert a total of acre-feet of water from the Black River in exchange for financing the Horseshoe Dam has long since been fulfilled. Water from the Black River is no longer diverted to support copper production.158 Since the Horseshoe Dam has functioned as part of the Salt River Project. Devoid of any hydro-electric power facilities, the dam is operated solely to serve the water needs of consumers in the Salt River Valley.

And as the ultimate proof of the victory of the Salt River Valley Water Users Association over the Rio Verde Canal Company and all its successors, water from the Horseshoe Reservoir is and always has been used only on land south of the Arizona Canal. The land north of Scottsdale in the Paradise Valley will continue to be developed using water from groundwater pumping or from the Central Arizona Project, which delivers water from the Colorado River to the greater Phoenix/Tucson region. 155 The design and operation of the gates are described in Raymond Hill to Morong, 21 September file no. H-A7.5(1950.02), SRP Archives. 156 Ibid., see also Morong to S.A. Ward, 21 January file no. H-A7.5(1950.02), SRP Archives, for documentation of acceptance of the gates as satisfactory.

157 For example, see T. M. Morong, Report on operation of Automatic Gates in Horseshoe Dam Spillway, 3 April file no. SRP Archives. 158 The rapid use of Phelps Dodge s rights to water in the Black River is reflected in its decision to purchase additional water from the Buckeye Irrigation District (located on the lower Gila River below Phoenix) between and This water was delivered to Phelps Dodge through the Black River diversion system.

The only reason the Salt River Valley Water Users Association acquiesced to this plan was because it was: 1) legally required to deliver certain amounts of Salt River water to the Buckeye Irrigation District; 2) this was the water that Buckeye was selling to Phelps Dodge; and 3) the association was to be compensated for their reduced electric power production resulting from the diversion. See BOG, Volume 31, Minutes for 13 October HORSESHOE DAM HAER No. AZ-24 (Page 47) Although the origins of Horseshoe Dam date back to the irrigation movement of the late nineteenth century, actual construction of the project is intimately tied to America s industrial expansion during World War II.

Looking back on the almost sixty-year period between its initial survey in and construction in there is little to find that was noble about the history of Horseshoe Dam. Built by an immense corporation as a means to compensate an established agricultural combine for water diverted to another watershed for use in war-driven industrial production, the dam is about as far from the rural agricultural ideal as it could get. The Bureau of Reclamation could have assisted the Rio Verde Canal Company and its successors in their effort to open the Paradise Valley to agricultural development, thereby fulfilling the agency s Congressional mandate to assist small-scale farmers in reclaiming the West.

But Interior Department officials instead aligned themselves with the politically powerful Salt River Valley Water Users Association in actively opposing the Verde-Paradise interests. They did this primarily to protect the Bureau of Reclamation s Salt River Project. The Water Users Association was for years in no position financially to develop the Verde River. It could not even keep up on its government repayment schedule for its existing dams on the Salt River. Despite this, the association was determined that no other group would tap the potential of the Verde, and, with the assistance of the Bureau of Reclamation, succeeded in blocking the Paradise-Verde interest for years.

It took a world war and two powerful outside sources Phelps Dodge and the Defense Plant Corporation to build Horseshoe Dam. Once the decision to build the dam had finally been made to augment the war effort, the Water Users Association and the Bureau of Reclamation, neither of which would design, build or finance the structure, wasted valuable time dickering over jurisdictional details in what amounted to little more than a turf battle. Further, this dispute centered around future use of impounded water, which had nothing to do with the exchange of water with Phelps Dodge. When the agreement had finally been negotiated, the Water Users Association failed to ratify it on the first vote, largely through the apathy of its membership.

This further delayed construction and increased its cost substantially. As a result of these delays, the dam was not completed until months after the war was over. Horseshoe Dam is significant for its tangential role in the American industrial effort behind World War II but it could hardly be considered the finest hour for either the Salt River Project or the Bureau of Reclamation. HORSESHOE DAM HAER No. AZ-24 (Page 48) Bibliography Manuscript Collections and Primary Sources Arizona Corporation Commission Dead Files. Arizona Department of Library, Archives and Records, Phoenix, Arizona. Engineering and Research Center Project Reports Bureau of Reclamation, Record Group Denver Branch, National Archives, Denver, Colorado.

General Administrative and Project Records, and Bureau of Reclamation, Record Group National Archives, Washington, Horseshoe Dam Folder, Bureau of Reclamation Files [Accession No. 115-62-A-473, Location Box Federal Record Center, Denver, Colorado. Notice of [Water] Appropriations. Arizona Department of Library, Archives and Public Records, Phoenix, Arizona. Records of the Clerk of the Board, Maricopa County Board of Supervisors, Phoenix, Arizona. Salt River Project Archives. Salt River Valley Water Users Association, Phoenix, Arizona. Salt River Valley Water Users Association, Minutes of the Meetings of the Board of Governors, Phoenix, Arizona.

Secretary of State, Appropriation of Water Dam and Reservoir Sites Files, Arizona Department of Library Archives and Public Records, Phoenix, Arizona. Books, Dissertations and Theses Bassell, Burr. Earth Dams: A Study, 2nd edition. New York: Engineering News Publishing Company, Campbell, Donald W. Report of Donald W. Campbell, Supervising Engineer, on the Storage Irrigation System of the Rio Verde Canal Company of Phoenix, Arizona. Minneapolis: Alfred Roper, Cleland, Robert G. A History of Phelps Dodge. New York: Alfred A. Knopf, Creager, William, Justin, Joel, and Hinds, Julian. Engineering for Dams, Volume III. New York: John Wiley and Sons, Davis, Arthur Powell. Irrigation near Phoenix, Arizona. U.S. Geological Survey Paper Number 2.

Washington, Government Printing Office, HORSESHOE DAM HAER No. AZ-24 (Page 49) Granger, Howell. X Marks the Spot: Historical Names of Places in Arizona. Tucson: Falconer Publishing Company, Introcaso, David M. Mormon Flat Dam. HAER AZ-14, Historic American Engineering Record, Prints and Photographs Division, Library of Congress, Washington, Jackson, Donald C. Roosevelt Dam. HAER NO. AZ-6, Historic American Engineering Record, Prints and Photographs Division, Library of Congress, Washington, Jackson, Donald C. and Fraser, Clayton B. Stewart Mountain Dam. HAER AZ-12, Historic American Engineering Record, Prints and Photographs Division, Library of Congress, Washington, Kollgaard, Eric B. and Chadwick, Wallace L., eds. Development of Dam Engineering in the United States.

New York: Pergamon Press, Lindell, David M., ed. Handbook of Nonferrous Metallurgy: Principles and Processes. New York: McGraw-Hill, Richard E. Winfield Scott: A Biography of Scottsdale s Founder. M.A. Thesis, Arizona State University, Mawn, Geoffrey P. Phoenix, Arizona: Central City of the Southwest dissertation, Arizona State University, McCullough, David. The Johnstown Flood. New York: Simon and Schuster, McFarland and Poole, compilers. A Historical and Biographical Record of the Territory of Arizona. Chicago: McFarland and Poole, Portrait and Biographical Record of Arizona. Chicago: Chapman Publishing Company, Richards, Robert H. and Locke, Charles E. A Text Book of Ore Dressing. 2nd edition. New York: McGraw-Hill, Schuyler, James D.

Reservoirs for Irrigation, Water Power and Domestic Water Supply. 2nd edition. New York: John Wiley and Sons, Shadegg, Stephen C. Century One: One Hundred Years of Water Development in the Salt River Valley, Phoenix: W.A. Krueger, Smith, Karen. The Magnificent Experiment: Building the Salt River Reclamation Project Tucson: University of Arizona Press, Smith, Norman. A History of Dams. Secaucus, New Jersey: Citadel Press, HORSESHOE DAM HAER No. AZ-24 (Page 50) Trimble, Marshall. Arizona: A Panoramic History of a Frontier State. New York: Doubleday and Company, United States Reclamation Service. Salt River Project, Arizona: Limiting Irrigable Area of Land, January 15, No publisher, no date. Wegmann, Edward. Design and Construction of Dams. 3rd edition.

New York: John Wiley and Sons, White, Gerald T. Billions for Defense: Government Financing by the Defense Plant Corporation During World War II. Tuscaloosa: University of Alabama Press, Zarbin, Earl A. Roosevelt Dam: A History to Phoenix: Salt River Project, Articles and Reports Agreement Between Salt River Valley Water Users Association, Verde River Irrigation and Power District and United States of America, June 19, Printed copy in Arizona Collection, Arizona State University Library, Tempe, Arizona. Arizona-Maricopa County-Phelps Dodge-Earth and Rockfill. Western Construction News 19 (April p. Barr, Remington. Phelps Dodge Corporation-Morenci Branch: Plant-Production-History, typewritten manuscript, circa Arizona Historical Foundation, Arizona State University Library, Tempe, Arizona.

Hayden, T.A. History of Water Rights of the Salt River Project with Special Reference to the Supply from the Verde River, typewritten manuscript. Salt River Project Archives. Phoenix, Arizona. Heim, Jawa, A Fortified Town of the Fourth Millennium Archaeology 27 pp. Hill, Raymond. Economic Survey of Salt River Project, Arizona, September typewritten manuscript. Minutes of the Board of Governors Meetings, Salt River Valley Water Users Association, Phoenix, Arizona. History of the Salt River Project for the Period January 1, to December 31, typewritten report. Salt River Project Archives, Phoenix, Arizona. History of the Salt River Project for the Period January 1, to December 31, typewritten report. Salt River Project Archives, Phoenix, Arizona. HORSESHOE DAM HAER No.

AZ-24 (Page 51) Huttle, John B. The Record of 100 Dam Failures. Journal of Electricity 44 (15 March and 1 April pp. Lee, Lawrence L. Arizona Earth and Rock Fill Dam Rising on Site Contemplated Fifty Years Ago. Western Construction News 20 (September pp. Rattlesnakes Add to Hazards of Arizona Dam Construction. Western Construction News 19 (July p. 87. The Rio Verde Company. Arid Region 2 p. 10. Schnitter, Roman Dams. Water Supply and Management 3 pp. Schuyler, James D. Recent Practice in Hydraulic Fill Dam Construction. Transactions of the American Society of Civil Engineers 57 pp. Sloan, Richard. Land and Water Rights, Salt River Project, typewritten manuscript. Salt River Project Archives, Phoenix, Arizona.

Verde River Storage Rights: Brief Filed at Hearing before Sub-Committee of Committee on Irrigation and Reclamation of the U.S. Senate at Phoenix, Arizona, November typescript. Salt River Project Archives, Phoenix, Arizona. Water for Arizona. Colorado Verde Association, ca. Pamphlet, copy in Arizona Collection, Arizona State University Library, Tempe, Arizona. Whitman, Structural Report on the Cylinder Gate at Horseshoe Dam, typewritten report, October Salt River Project Archives, Phoenix, Arizona. Work Starting on Earth and Rock Fill Dam on Verde River in Arizona. Southwest Builder and Contractor 104 (7 July pp. HORSESHOE DAM HAER No.

AZ-24 (Page 52) Appendix, Figures Construction drawings from Horseshoe Dam, reproduced from microfiche print originals located at the Salt River Project Archives, Tempe, Arizona. Note the drawings have been edited in Adobe Photoshop to improve legibility, including removing illegible text and small-scale detail drawings. Figure 1. Maximum section of earth and rockfill design for Horseshoe Dam. From drawing by Leeds, Hill, Barnard and Jewett, 5 January HORSESHOE DAM HAER No. AZ-24 (Page 53) Figure 2. General Plan and Sections, Horseshoe Dam and Spillway, Alternate A - Earth and Rockfill Type. Leeds, Hill Barnard and Jewett, 5 January HORSESHOE DAM HAER No. AZ-24 (Page 54) Figure 3. Outlet Tunnel: Works Constructed in Advance-Tower Base, Inlet Lining and Outlet.

Leeds, Hill, Barnard and Jewett, 24 January HORSESHOE DAM HAER No. AZ-24 (Page 55) Figure 4. Horseshoe Dam Outlet Tower, Structural Details-Steel Superstructure. Leeds, Hill, Barnard and Jewett, 15 January HORSESHOE DAM HAER No. AZ-24 (Page 56) Figure 5. Horseshoe Dam Outlet Tower, Structural Details Concrete Structure. Leeds, Hill, Barnard and Jewett, 15 January HORSESHOE DAM HAER No. AZ-24 (Page 57) Figure 6. Changes to Horseshoe Dam Spillway. Cone and Proctor, Civil Engineers for Salt River Valley Water Users Association, April HORSESHOE DAM HAER No. AZ-24 (Page 58) Figure 7. Progress Chart: Placement of Fill in Horseshoe Dam as of July 20, HORSESHOE DAM HAER No. AZ-24 (Page 59) Figure 8. Horseshoe Dam Outlet Works Tunnel Portal Nozzle.

Leeds, Hill and Jewett, 10 April HORSESHOE DAM HAER No. AZ-24 (Page 60) Figure 9. Spillway Gates, Gate Control Mechanisms. Leeds, Hill and Jewett, 13 December HORSESHOE DAM HAER No. AZ-24 (Page 61) Figure 10. Preparatory Work: General Plan of Works. Leeds, Hill and Jewett, 13 December HORSESHOE DAM HAER No. AZ-24 (Page 62) Figure 11. Preparatory Work: Piers Longitudinal Section. Leeds, Hill and Jewett, 13 December HORSESHOE DAM HAER No. AZ-24 (Page 63) Figure 12. Preparatory Work: Piers Cross Sections. Leeds, Hill and Jewett, 13 December HORSESHOE DAM HAER No. AZ-24 (Page 64) Figure 13. Spillway Gates, Gate Supporting Arms. Leeds, Hill and Jewett, 13 December HORSESHOE DAM HAER No. AZ-24 (Page 65) Figure 14. Spillway Gates, Framing Details.

Leeds, Hill and Jewett, 14 December HORSESHOE DAM HAER No. AZ-24 (Page 66) Figure 15. Spillway Gates, Foot Bridge. Allison Steel Manufacturing Company, 23 July HORSESHOE DAM HAER No. AZ-24 (Page 67) Figure 16. Cylinder Gate [Repair] Steel Erection and Details. Salt River P.A.I. Power Unit, 15 March