Stewart Mountain Dam, Spanning the Salt River, Tempe

Source document Quoted word for word from HAER AZ-12. Not written, edited or summarised by this site.

Spanning the Salt River approximately 40 miles east of Phoenix and 10 miles east of the confluence of the Salt and Verde Rivers; Maricopa County, Arizona. USGS Quadrangle: Stewart Mountain, Arizona (7Yi minute series, S 7 UTM Coordinates: 12.450305.391402ffi ? - t:,\o\-~,J\e.d !...A,~\~~ '- C"a.()(1.-, W"\ \ y c) Construction Date: Dam and powerhouse: Concrete spillway lining: West spillway: Engineers: Charles C. Cragin, Chief Engineer for Salt River Valley Water Users' Association, with assistance from staff of U.S. Bureau of Reclamation Builders: Force account labor under supervision of Charles C. Cragin, Chief Engineer, and Connell, Assistant Chief Engineer, Salt River Valley Water Users' Association.

Source document Quoted word for word from HAER AZ-12. Not written, edited or summarised by this site.

Along with the earlier Roosevelt, Horse Mesa and Mormon Flat dams, which are upstream, Stewart Mountain Dam impounds water on the Salt River for use in generating power and for supporting irrigation and domestic use within the Salt River Valley. The dam is thus an important component of the Salt River Valley Users' Association's electric power generating system that provides service for much of central Arizona. The structure is also an important example of a radius arch dam designed using the trial local method.

Source document Quoted word for word from HAER AZ-12. Not written, edited or summarised by this site.

Donald C. Jackson FRASERdesign Loveland, Colorado {} Stewart Mountain Dam jJ HAER No. AZ-12 ii page 2 Introduction The Stewart Mountain Dam is a 212-foot-high, reinforced concrete arch structure that extends across the Salt River at a location about forty miles east of Phoenix and about ten miles upstream from the confluence of the Salt and Verde Rivers. The dam is comprised of a single arch flanked on both sides by gravity buttresses or abutments, with a gravity overflow spillway on the east side. The main arch stretches 480 feet from buttress to buttress and varies in thickness from eight feet at the crest to 33 feet at the deepest foundation. 1 At the crest, the arch is circular in shape with a radius of 273 feet, thus encompassing an arc of approximately 120 degrees.

Originally engineered as a variable radius dam with circular arches that gradually reduced in radius the deeper they were located in the struc- ture, the dam's design was later revised so that arches in the lower part were flattened in the shape of "more or less complex curves not developed on geometrical lines."2 Stewart Mountain Dam is thus best described as a variable-radius, multiple-curve design. The massive concrete buttresses at each end of the arch were built because no steep can- yon walls suitable to resist the horizontal arch thrust existed at the damsite. 3 Measuring 15 feet by 30 feet at the top, the pyramid-shaped buttresses splay downward for more than 100 feet; each is approximately 150 feet long, with a base thickness of more than 50 feet.

4 On the west end of the dam a 115-foot-long, straight concrete wall with a grav- ity section that extends from the buttress into the side of the canyon. On the dam's east end, a gravity-section wall extends perpendicularly from the buttress for 90 feet; beyond that is a 270-foot wide, concrete-lined spillway topped by nine Tainter gates, each 23 feet high and 27 feet long. Stretching beyond the spillway is a 225-foot, grav- ity-section wall that joins the main structure with the canyon wall at the eastern end. Before construction on the Stewart Mountain Dam began late in the natural stream.bed of the Salt River at the site lay at an average elevation of feet above sea level.

The deepest foundation of the dam extends to a depth of feet above sea level, while the crest lies at an elevation of feet. When filled to capacity, the reservoir behind the dam (now known as Saguaro Lake) contains acre-feet of water (An acre-foot is a volume of water equal to one acre of land covered with water one foot deep; it is equal to cubic feet or about gallons.) The reservoir covers a maximum surface area of acres and meanders through the Salt River Canyon for a distance of ten miles above the dam. J} Stewart Mountain Dam }) HAER No. AZ.-12 }t page 3 . . . Water from Saguaro Lake is released downstream through four penstocks that extend through the western end of the dam at elevations averaging about 100 feet below the dam's crest.

Closest to the centerline of the structure is an 8-foot-diameter penstock, a reserve outlet that has never been used. West of this is a 7-foot-cliameter penstock regulated by a single butterfly valve. Adjacent to this is another 7-foot-diameter opening, which bifurcates into two separate penstocks, each regulated by a 54-inch needle valve. 5 Furthest west is the most important opening in the dam, a 13-foot-diameter penstock that passes directly into the hydroelectric powerhouse located adjacent to the dam's down- stream face. The 60-foot-square, two-story, reinforced concrete powerhouse is a pivotal part of the Stewart Mountain complex.

In fact, because financing for the dam was predicated upon projected hydropower revenues, the power facility comprised the historic raison d'etre for the entire project. The power penstock attaches directly to a horsepower Francis reaction turbine with scroll casing manufactured by the S. Morgan Smith Com- pany of York, Pennsylvania. 6 Water flows into the turbine chamber under an average head (or pressure) of 100 feet and rotates the horizontal turbine runner at an average speed of 150 revolutions per minute The blade runner is connected directly to the main generator by a vertical shaft extending upward to the ground floor level of the powerhouse.

Rated at kilowatts, the General Electric three-phase generator pro- duces current at a potential of volts.7 The unit was designed initially to generate alternating current at a frequency of 25 cycles. In recent years, however, the armature has been rewound to generate a 60-cycle current. 8 Located directly on top of the gener- ating unit, and also attached to the turbine's drive shaft, is a small 250-volt, direct current "exciter" generator. This DC unit provides current that charges the electromagnets in the armature of the main generator.

9 Although the immense turbine/generator unit is the most prominent feature within the Stewart Mountain powerhouse, other important components are located on the main level, including a Woodward governor (with associated oil pump and tank) that is used to maintain constant turbine speed, a control room, and electrical switching equipment used in connecting and disconnecting the facility with the outside world. 10 A storage room (now unused) is located on the second floor of the powerhouse; this space was originally designed to contain transformers that would raise the voltage of the current before transmission to the Phoenix region.

Before ever being brought into service, however, this transformer room was supplanted by an outdoor transformer station located directly beside the powerhouse at the western end of the dam. The General Electric transformers raise the current from the generator from volts to volts for transmission to the Salt River Valley. 11 (: Stewart Mountain Dam ti HAER No. AZ-12 JI page 4 -'1 7., . ~ > 0 N I C: . -'1 0: . !j !;; 0 ;: ~ I-< ;_; . ~ w . ,i ,i ... ~ ." 0: 0 C: Cl. .. c w "' ~ C: g ~ ." !: C: :,; b !:; tr. , ; Figure 1. Map of Salt River and Phoenix Area. From drawing by U.S. Reclamation Service, ?I Stewart Mountain Dam (( HAER No. AZ-12 }C: page 5 The Salt River N arned for the brackish taste of its waters, the Salt River is one of Arizona's most important streams.

With its tributary, the Verde River, it drains over square miles in the central and eastern parts of the state. The Salt River rises in headwaters of the Black River at an altitude of over feet and flows southwesterly for some 200 miles before joining with the Gila River a short distance west of Phoenix. In its easternmost reaches, the Salt drains a rugged mountain region covered by substan- tial snowpack during the winter months. Streams such as White Mountain Creek, Box Canyon Creek and Cherry Creek carry runoff from the snowpack and from intermittent rain storms into the river, causing it to swell occasionally into a raging waterway.

Be- cause of variations in precipitation in the Salt River watershed, the natural flow of the river can vary from less than 200 cubic feet per second in times of drought to more than cfs during periods of intense flooding. With its fertile deposits of alluvium in what is now Arizona's Salt Central Valley, the Salt formed the basis for one of the earliest irrigation-based settlements in the New World. In the period A.D., before the arrival of Europeans to the continent, the Hohokarn Indians diverted the river's flow through an extensive network of irrigation canals to grow crops in the broad desert valley around present-day Phoenix.

Although the Hohokarn had long since disappeared when the area was first settled by Anglos in the mid-19th century, the remains of their irrigation canals were still evident on the land- scape. The rudiments of the present-day irrigation system and agricultural settlement in the Salt River Valley date from That year William John "Jack" Swilling, flamboyant Confederate army officer, prospector, Indian fighter and entrepreneur, opened an irriga- tion ditch with ''Yours Truly" Smith, the post sutler at Fort McDowell. They formed the Swilling Irrigation Canal Company, and with some contributed by local inves- tors, opened the Swilling Ditch by clearing an ancient Hohokam canal.

Eventually called the Town Ditch, Swilling's canal extended from the north bank of the Salt River, north- west a mile-and-a-half across the desert, and then curved back toward the river. In a man named Frenchy Sawyer started the first permanent farm in the valley, irrigated by the Swilling Ditch. Sawyer was soon joined by others, and two years later the townsite of Phoenix was platted. 12 Over the following ten years other canals branched from the river, including such formative irrigation ventures as the Tempe Canal San Francisco Canal Utah Canal and Mesa City Canal on the south side of the river and the \ Stewart Mountain Dam ,( HAER No. AZ-12 JJ page 6 Maricopa Canal and Grand Canal north of the river.

Using nothing more than small diversion darns to deflect the natural flow of the stream, these early irrigation ditches demonstrated the capacity of the Salt River Valley to support a substantial agricul- tural economy. In fact, by over acres of farmland were under irrigation in Maricopa County, the site of Phoenix and other agricultural towns such as Tempe and Mesa. The county was home to more than settlers.13 By the tum of the century, valley farmers had come to recognize that their continued ability to flourish would forever be stunted if they could not find a way to increase the region's surface water supply. Until this time the irrigation canals had been dependent solely on the natural flow of the Salt River, a desert stream notorious for its extreme fluctuations in flow.

Without the means to impound the river, farmers and canal owners could only stand and watch as floodwaters of the Salt roared past their headgates untapped. And with no provision to accumulate a reserve of flood waters to supplement the river during dry periods, their crops withered in the intense desert heat with insufficient flow in the irrigation ditches. Roosevelt Dam The issue of water storage and potential drought was by no means unique to the Phoenix area; in fact, it is a problem endemic throughout virtually the entire Western America. Water - or more specifically, the lack of it - has from the start occupied a central position in the development and settlement of the region.

In John Wesley Powell first directed public consciousness to the interrelationship between water storage and Western agricultural development in his now-famous Report on the Lands of the Arid Regi,on. 14 A prominent proponent in the nationwide "irrigation crusade" that developed in the Powell espoused the virtues of Western irrigation as the director of the Interior Department's U.S. Geological Survey. During the late and early he supervised the Congressionally sponsored Irrigation Survey, a branch of U.S.G.S.

intended to explore the potential for development of the region's water re- sources.15 Although government officials denied that the survey was intended as a fore- runner of federally sponsored irrigation projects, its prime objective was to identify and locate promising sites for storage reservoirs. Powell's Irrigation Survey functioned for less than five years before its dissolution, but not before the agency had focused national at- tention on the role that water storage reservoirs could play in expanding the region's economy. ti Stewart Mountain Dam HAER No. AZ-12 1:1 pao-e o 7 The Irrigation Survey made only a cursory study of Arizona Territory.

It did, however, prompt agricultural interests in the Phoenix area to dispatch a three-man surveying party to explore potential reservoir sites in the upper Salt River and Verde River watersheds. Undertaken in the summer of under the direction of Maricopa County Surveyor William M. Breakenridge, the Breakenridge Survey located an ideal dam site just below the mouth of Tonto Creek in the Mazatzal Mountains about 60 miles east of Phoenix. 16 Known as the Tonto site, a storage reservoir with a capacity exceeding a million acre feet of water could be impounded here by building a dam less than 300 feet tall.

Early in the Hudson Reservoir and Canal Company, a privately held corporation, initiated plans to build a storage dam at the Tonto site and filed claims for land encompassing the reservoir area. Although the company's project was technically and legally feasible, the monetary risk involved in implementing the ambitious scheme proved too great to attract investors in the financially depressed mid-1890s. Throughout the remainder of the decade, the Hudson Company's plans were widely known among civil engineers and irrigation enthusiasts, but little headway was made on the project. 17 After the tum of the century, Phoenix-area promoters enlisted the aid of the U.S. Geological Survey in planning a storage dam at the Tonto site to increase the supply of water in the Salt River Valley.

Similar in design to the Hudson Company's initial proposal, this new plan would be financed by public bonds issued by Maricopa County. 18 Before the project reached the point of financial commitment, however, events in Washington completely altered the political and economic forces controlling Western water development. Succeeding to the presidency after the assassination of William McKinley in September Theodore Roosevelt almost immediately embarked on a course to involve the government directly in the development of Western water resources. The keystone to Roosevelt's plan was the National Reclamation Act, alternately known as the Newlands Act for its sponsor, Nevada Congressman (later Senator) Francis Newlands.

Signed into law on June 17, this landmark legislation incorporated elements of executive independence from the legislative branch, nationalization and a scientific approach to natural resource management as the first truly Progressive measure of the Roosevelt Administration. As originally drawn, the Newlands Act directed the Secretary of the Interior, through the newly formed U.S. Reclamation Service, to select irrigation projects in sixteen arid Western states and territories that would most benefit from federal funding, using proceeds from public land sales in these states. The U.S.R.S. would undertake construction of these projects directly, and upon completion of each the farmers benefiting from the project would be required to repay the construction costs in ten annual payments.

Under the direction of Chief Engineer Frederick H. Newell - later the agency's first director - the Reclamation Service quickly listed projects that could make good use of the new federal program and, not coincidentally, place the new program in a favorable light ft Stewart Mountain Dam ::t HAER No. AZ-12 i:I page 8 with Congress. Armed with an optimistic reconnaissance report by Reclamation Service principal Arthur Powell Davis and encouraged by development interests in the Phoenix area, the agency included among its initial ventures a large storage dam at the Tonto site on the Salt River.

Before committing the government to construct the Tonto Dam, the Reclamation Service required that landowners in the Salt River Valley coalesce into a regional organization which would represent the collective interests of the region's farmers. Organized in the Salt River Valley Water Users' Association (SRVWUA, predecessor to today's quasi-public Salt River Project) formed a single entity through which the valley's farmers could negotiate with the Reclamation Service. The Water Users' Association also assumed responsibility for repayment of the completed project. 19 With the formation of the Water Users' Association and commitment of the Reclamation Service to build the dam, work got underway quickly on the Salt River Project.

Contrac- tors began clearing the site for the dam proper, soon re-christened Roosevelt Dam, in and work on the 280-foot high, curved gravity dam continued for several years until the final blocks of masonry were put in place in early By the time the structure was formally dedicated in March it had already begun impounding water for use by members of the Water Users' Association in the valley below. Finally, after decades of concern and work, farmers in the Phoenix area were no longer dependent upon the natural flow of the Salt River to irrigate their crops. Salt River Project: Initiation Once completed Roosevelt Dam functioned well enough technologi- cally.

It and its associated features had taken much longer to construct than originally anticipated, however, and the aggregate cost of the Salt River Project zoomed from around $3 million to more than $10 million. Some of this increase was attributable to construction of the Granite Reef Dam, a completely new structure located at the head- gate, to the valley's irrigation canals. Built to replace the failed Arizona Dam, the Granite Reef structure had not been budgeted at the project's inception. 20 Other parts of the project, such as the cement factory and the power canal built to help supply electricity to the construction site, ended up costing much more than the Service had initially estimated. This led to considerable discontent among members of the Water Users' Asso- ciation.

As a result, official completion of the Salt River Project was delayed for several years while Reclamation and the Water Users' Association bickered over the repayment cost of the project. )ff Stewart Mountain Dam :@j HAER No. AZ-12 JI page 9 ' ' ' This dispute festered until when Interior Secretary Franklin Lane finally set the repayment cost for the Salt River Project at slightly under million. But the contro- versy over Reclamation's administration of the Salt River Project prompted Lane to alter the government's role in water use management in a way that had not been envisaged when the National Reclamation Act was passed in Originally, the Reclamation Ser- vice was to bear responsibility for the operation of the reclamation projects it had built.

The various water users' associations served by the projects were to coordinate political and economic activities associated with repayment, but management of the physical plants was to remain in federal hands. After six years of fighting between Reclamation and SRVWUA, however, Lane turned over management of the Salt River Project directly to the Water Users' Association: a precedent that would be followed on subsequent Reclama- tion-sponsored projects. On September 6, the two parties executed a "Contract Between United States Gov- ernment and Salt River Valley Water Users' Association". 21 This agreement obligated the government to: tum over to and vest in the said Association, the care, operation and maintenance of the inigation works known as the Salt River Project. ..

consisting generally of the Roosevelt Dam, the Granite Reef Dam, inigation canals, laterals, ditches... [and] all water rights and franchises, and rights to the storage, diversion and use of water for inigation or other pwposes [including] water power, and power privileges, with such right of possession of all thereof. The Water Users' Association would: receive to its own use and benefit, all the rents, issues, profits, revenues and income, including all income from power and power privileges growing out of or arising from the operation and maintenance of the project and every part thereof by it. [emphasis added] 22 In return, the Water Users' Association agreed "to accept the transfer to it of the care, operation and maintenance of said project ...

in such a manner that the same and every part of it thereof shall remain in a good and efficient condition."23 The contract further stipulated that the Association could make no substantial change to the project nor could it sell or lease its power privileges for periods of longer than one year without the prior consent of the Secretary of the Interior. 24 Execution of the contract signaled the official completion of the Salt River Project and the beginning of repayment of the millions of dollars expended by the government during the previous fifteen years. The Water Users' Association had not made a single payment to date, although its members were enjoying the benefits of the project. The signing of the contract initiated the repayment obligation.

As stipulated in the contract, the Association was to pay off the million debt through a series of annual ff Stewart Mountain Dam fi HAER No. Al.-12 )1 page 10 . . . installments (extended by Congress from the original 10 to 20 years). The Association was to repay two percent of the total loan each year (approximately for the first four years; the annual payment would then increase to four percent (approximately for two years, and then level off at six percent per year (approximately for the remainder of the loan. Although the debt represented a substantial sum for area farmers, it would have been several times greater had Reclamation not been willing to forgive years of accrued interest on the balance.

Proceeds for the annual payments were to be gathered from assessments made proportionately on each of the farmers who benefited from the project. The farmers' payments were to be made ostensibly from the increased profits derived as a result of additional irrigation: as long as agricultural prices remained sufficiently high, the farmers would have little problem in paying off the government debt. During and the market for cotton was so good that the Salt River Valley was flush with growers experiencing some of the most profitable years in the region's history. But crop prices plummeted in the agricultural depression following World War I, leaving Phoenix-area producers with insufficient funds to service the government loan.

25 Facing the prospect of default by the Water Users' Association, the government in amended the original contract to extend the time allowed for the scheduled and installments. 26 In the early the Association leadership began to recognize that agricultural profits alone might not be enough to service the long-term debt that saddled the regional economy, despite the numerous de facto subsidies by the govern- ment. Contract extensions would forestall an economic crisis, but such repayment moratoria ultimately did nothing to alleviate the financial difficulties faced by the Association. It was in this context that SRVWUA began developing plans for a vastly enlarged hydroelectric power system that would produce a new source of revenue to pay off its debt to the government.

27 Hydroelectric Power Generation The theoretical basis of hydroelectric power generation is relatively simple. Electrical current in a conductor (e.g., a copper wire) can be produced by moving the conductor through the magnetic field that surrounds a magnet. A good way to produce a constant current in a conductor is to rotate it continually around a magnet fi Stewart Mountain Dam (1 HAER No. AZ-12 Ii page 11 so that it is always cutting through the "lines of force" of the magnetic field. A number of ways exist to power the rotation of a conductor through a magnetic field (including coal-fired steam engines); one of the most efficient of these is a water turbine.

The term "water power" refers to the kinetic energy associated with a quantity of water falling a certain distance under the force of gravity. Anyone who has ever carried a bucket of water up a flight of stairs knows that this activity requires the exertion of energy to accomplish. Similarly, anyone standing under a second floor window when a bucket of water is poured out experiences firsthand the power inherent in falling water. The amount of energy available in developing water power is equal to the weight of water multiplied by the distance the water falls. (This distance is often referred to as "head".) Thus, the more water there is in a river and the greater the vertical distance that the river drops, the more water power there is that theoretically can be developed.

28 The most rudimentary method of developing water power involves the use of a large wooden wheel with buckets that can be rotated by having water enter the top and flow. Given a steady flow into the buckets, the wheel will rotate indefinitely. 29 These overshot water wheels, as they are termed, have been historically most closely associated with small-scale grist mills. Traditional water wheels were not especially efficient, though, in their ability to transform the kinetic energy of a stream into actual power production. 30 Hydraulic engineers worked throughout the century on more efficient methods of tapping the energy of falling water, eventually developing modem pressurized water turbines.

A water turbine such as the unit installed in the powerhouse of Stewart Mountain Dam converts the force of pressurized water into circular motion by passing the water into an enclosed chamber through slotted blades or runners that comprise the movable part of the turbine. The blade runners are attached to a central metal shaft that in tum rotates another assembly. The form of this latter assembly depends upon the ultimate use of the power developed by the turbine. Turbine shafts can be connected directly or through belts to mechanical devices, such as a lathe in a woodworking shop or a spinning wheel in a textile factory. Alternately, turbines can be used to generate electricity by connecting the rotating shaft with the rotating magnetic armature of an electrical gener- ator.

By converting water power into a rotating force and then applying this force to the movement of a conductor through a magnetic field, hydroelectric power is produced. 31 The era of large-scale commercial electric power systems dates to the when Thomas Edison first marketed his direct current central station plants, and George Westinghouse subsequently developed alternating current (AC) systems. 32 By the large-scale hydroelectric generating stations operated at Niagara Falls and in a variety of locations throughout California and other parts of the United States. 33 During this time hydroelectric plants located in remote mountain locations were supplying power to urban areas via long distance, three-phase AC transmission lines capable of being used for both lighting and power purposes.

34 A volt, 83-mile long transmission line was supply- II Stewart Mountain Dam ?[ HAER No. AZ-12 r: page 12 ing hydropower to Los Angeles on a year-round basis by And by a volt, 140-rnile long transmission line connected the San Francisco Bay Area with the Bay Counties Power Company's hydroelectric generators in the Sierra Nevada Mountains. 36 Salt River Project: Early Hydropower Generation Clearly, by the time the Reclamation Service began planning for a hydroelectric power system to help facilitate the construction of Roosevelt Dam, the technology had long since passed from the experimental stage.

The Roosevelt hydroelec- tric power plant, in both an initial, temporary installation and in the permanent facility, did not constitute a radical departure from contemporary engineering practice. Instead the Reclamation Service adapted technologies which had already been used at other Western sites. A lengthy power canal was needed to develop the necessary head of water to generate electricity during the construction process. As described in the report of HAER No. AZ-4, th~ Roosevelt Power Canal diverted water from the Salt River at a location about twenty miles upstream from the damsite and carried it in a concrete channel at a gradient slight- ly less than the bed of the river itself, developing a head of about 220 feet at the damsite.

37 By the spring of a penstock had been built connecting the power canal with a 950-kilowatt turbine/generator unit located in a shallow cave adjacent to the permanent powerhouse, then under construction. The permanent powerhouse at Roosevelt first came on line in replacing the temporary facility. By five generator/ turbine units with a combined capacity of kilowatts were installed at Roosevelt. In a sixth unit was added that boosted the power plant's capacity by kilo- watts. 38 By this time three of the turbine/ generator units were connected to the power canal penstock while the other three (including the kilowatt unit) were served by a penstock extending through the dam that drew water directly from the impounded res- ervoir.

As a result, the head for these latter units was dependent upon the height of the water within the reservoir, which could vary substantially. Electric power from Roosevelt Dam was used for a variety of purposes, including the operation of irrigation pumps throughout the Salt River Valley and general commercial service in the greater Phoenix area. 39 The most important customer for power produced by the Salt River Project was a private utility, known as the Pacific Gas and Electric it Stewart Mountain Dam :J HAER No. AZ-12 : : : page 13 Company and later renamed the Central Arizona Light and Power Company (CALAPCO), that bought power in bulk quantities from the government and resold it at a profit to consumers.

40 The economic attractiveness of hydroelectric power generation was quickly evident, because it offered a way to pay off the huge cost of the Roosevelt Dam without relying upon the vagaries of agricultural prices and profits. Within a few years after the dam's completion, the Water Users' Association undertook construction of three small hydroelectric plants to provide additional income. These facilities (known as the Arizona Falls, Consolidated and Cross Cut Power Plants) were located at natural drops in eleva- tion within the Association's existing water distribution system. First brought on line in they added an additional kilowatts of power capacity to the Salt River Valley generating system.

41 When the federal government turned over administrative control of the Salt River Project to the Salt River Valley Water Users' Association, this included responsibility for an electric power system with a generating capacity of over kilowatts. Although the contract granted the Association relatively wide latitude in operating the project, the government retained the right to approve or reject any action which would substantially affect the physical condition of the facilities or impact upon the financial affairs of the Association. Given its considerable investment in the project, it was not unreasonable to expect that the Department of the Interior would retain at least some authority over future development activity.

In a change in the Water Users' Association leadership provided an opportunity for the Reclamation Service to begin overseeing an expansion of the project's electric power system. Frank Reid, a cattle rancher and mining investor who had come to Arizona from Texas in assumed the presidency of the Association that July. Concurrently, Charles. C. Cragin, an engineer with previous experience in large-scale water development projects (including New York City's and Oakland's water systems), took over as general superintendent and chief engineer. 42 With Reid's support, Cragin began a comprehensive study of the Association's hydroelectric power system and potential means of expanding it.

With the financial condition of Association members seriously weakened by the na- tionwide collapse of agricultural prices, the search for additional power revenues took on increasing urgency. 43 After eighteen months of analysis, Cragin, with assistant chief engineer Francis J. O'Hara and electrical engineer Harry J. Lawson, completed a study entitled "Report on Proposed Additional Hydro-Electric Power Development of the Salt River". 44 Issued in February the report focused on the best means to take advantage of the water power poten- tial inherent in the drop of the Salt River between the Roosevelt Dam and the flat lands of the lower valley in the Tempe/Phoenix region: a hydraulic drop of some 700 feet between Roosevelt and Granite Reef.

The objective of the Cragin report was to determine a way to develop this tremendous potential. it Stewart Mountain Dam Ji HAER No. AZ.-12 }\ page 14 In operating the original powerhouse at Roosevelt, it had become apparent that maximiz- ing the amount of hydroelectric power generated could not be accomplished as long as water releases from the reservoir were determined primarily by irrigation needs and not by electric power demand. This problem was related to a basic dichotomy in the role that water storage played in increasing both irrigation and water power within a water- shed. Both purposes benefited from the retention of floodwaters, but the interests of irrigation were best served by releasing water primarily during the growing season of late spring, summer and early fall.

Over the rest of the year, irrigators' demand for water was minor, and during this time irrigation interests wished that no water be released from reservoirs in order to conserve supplies for the next growing season. In contrast, electric power production was a year-round endeavor, especially when serving a market of general commercial and domestic consumers. To serve such a market using hydroelec- tric power meant that water from the reservoir was released on a regular schedule. This conflicted directly with the seasonal releases best suited to irrigation needs. 45 Cragin understood the need to reconcile the conflicting needs of irrigation and power generation.

Beyond the installation of an additional kilowatt turbine/generator unit at Roosevelt and gates on the spillways to increase the head available from Lake Roosevelt, he proposed a new storage dam on the Salt River below Roosevelt that could store water after it had already been used to generate power at Roosevelt. Named the Mormon Flat Dam, the new structure could be eventually outfitted with a hydroelectric plant of its own, but its immediate purpose was to provide a way of regulating the flow of the Salt to accommodate the dual needs of irrigation and power production. Cragin proposed building the 228-foot-high Mormon Flat Dam at a site about 27 miles down- stream from Roosevelt.

46 It would create a reservoir with a storage capacity of over acre-feet so that water could pass through the Roosevelt generators and still be conserved for maximum irrigation utility. Construction of the Mormon Flat Dam would provide the Water Users' Association with greater flexibility in generating power, without construction of new power generation facilities, and in the world of electric power utili- ties, flexibility in the handling of generating capacity typically resulted in greater profits. 47 The top of the planned Mormon Flat Dam lay at an elevation of 16 71 feet above sea lev- el, substantially below the base of the Roosevelt Dam (located at a height of about feet above sea level).

The gap between the Mormon Flat and Roosevelt Dams represen- ted a hydraulic drop of more than 260 feet that could be further developed for power production. To take advantage of this, Cragin envisaged the construction of a third dam to generate hydroelectric power. Horse Mesa Dam, as it was called, would rise to a height of 305 feet above its deepest bedrock foundations and would eventually support the operation of kilowatt hydroelectric power plant, the largest that would ever be built along the Salt River. 48 Because Horse Mesa would lie upstream from Mormon Flat, it could be operated solely to generate electricity without regard to irrigation schedules. !@ Stewart Mountain Dam :it HAER No. AZ-12 I:!

page 15 The primary purpose of Cragin's report was to analyze increases in the capacity of the Water Users' Association electric power system made possible by construction of the Mormon Flat and Horse Mesa darns. In it he pointed out that between the base of the proposed Mormon Flat Darn and the Granite Reef Darn was a drop of over 200 feet that could be developed for further power production. Rather than discuss in any de- tailed way how this water power might eventually be harnessed, however, Cragin only described in briefest terms a scheme for building a shallow diversion darn that would supply water through a 21-rnile long power canal to a new powerhouse located on the banks of the Verde River, a short distance from its rnouth.

49 No detailed plans for this scheme were ever developed, but Cragin evidently envisaged a system comparable to the power canal like that at Roosevelt Darn. He recognized the value of developing some kind of power plant along the stretch of river below the Mormon Flat Darn, but serious planning for this facility held a low priority until the Mormon Flat and Horse Mesa struc- tures were completed. The power canal plan was eventually scrapped in favor of the Stewart Mountain Darn. After presenting his report to the membership of the Water Users' Association early in Cragin and his staff immediately began planning its implementation.

Construction of the two proposed darns and associated features would be expensive, fundable only through a bond issue approved by a three-quarter majority of the Association's member- ship. 50 Because of the Association's difficulties in meeting its existing financial obligations and because the Association would be contracting for long term power leases as part of the financing schemes, approval of Cragin's plan would also be necessary from the Secre- tary of the Interior. After negotiations in and the Department of the Interior approved the Mormon Flat Project, and, concurrently, the Association authorized the mortgaging of lands to support the proposed construction.

51 With their land as collateral for the privately financed bonds, Association members had gambled nearly everything on the success of Cragin's plan. But the Association touted the revenues from additional power generation as the best means to repay the staggering debt associated with the con- struction of Roosevelt Darn.

Work on the Mormon Flat Darn began in and was completed by a kilowatt power plant at the darn became operational by Meanwhile, construction of the Horse Mesa Darn and its kilowatt power plant had started in and concluded by The latter project's construction had been facilitated by a long-term contract with the Inspiration Copper Company in which the mining firm agreed to pur- chase the entire electrical output of the Horse Mesa power plant at rates which appeared to guarantee that payments on the financial bonds could be met without using any addi- tional funding sources. The success of Cragin's hydroelectric power development plan soon began to attract national exposure. For example, in a communication to the American Society of Civil Engineers, Jarvis of the U.S.

Bureau of Public Roads reported: ti Stewart Mountain Dam ii HAER No. AZ-12 fyt {/ page 16 iy.' err An excellent example of coordinated power and irrigation development is furnished by the Salt River Project, in Arizona. Formerly the power plants could not be operated during the non-irrigation season, because the discharge from the turbines was lost to the system. s. \ This situation has been relieved by the supplemental storage [i.e. Horse Mesa and Mormon ridg Flat Dams] provided between the Roosevelt Dam and the intake of the main irrigation canals.

This immediately replaced the intermittent power generation with constant, dependable service.52 s ir eav rrat Stewart Mountain Dam: Inception !.cor ,a S 00( During the economic boom years of the mid-1920s, the success of the Water Users' Association in finding lucrative, long-term markets for its electric energy prompted Cragin to look to the power potential existing along the remainder of the lower Salt River. He soon began to develop plans for what would come to be known as Stewart Mountain Dam. Although in his report he had briefly discussed a lengthy power canal along the lower stretch of the Salt River, by plans for implementing this type of scheme had been shelved.

On February 8th of that year, Cragin made a presentation to the As~ociclfion's board of governors that outlined plans and cost estimates for a rein- forced concrete arch dam at the Stewart Mountain site, a powerhouse with a generating capacity of kilowatts, and a volt transmission line that would connect the facility with. the Association's electrical grid. 53 Cragin estimated the aggregate cost of the Stewart Mountain Dam, powerhouse and transmission line at approximately million. In addition, his proposal included a million estimate for "electrification of valley," which involved construction of electric power distribution lines to previously unserved areas of the Salt River Valley.

Finally, Cragin's proposal recommended the sale of an additional in bonds as an early repayment of part of the Water Users' Associ- ation's debt to the government. The critical financial prerequisite to construction of the Stewart Mountain Dam involved a contract negotiated between the Water Users' Association and the privately-owned Central Arizona Light and Power Company (CAIAPCO) for the guaranteed purchase of power. 54 Executed on February 8, the SO-year agreement stipulated that CAIAPCO would purchase a minimum of kilowatts of electricity on a continuous basis for a minimum annual payment of per year, to begin one year after first delivery of power from the Stewart Mountain plant.

Beyond this minimal annual payment, the energy charge would be made at a rate of eight mills ) per kilowatt hour. t: Stewart Mountain Dam f: HAER No. AZ-12 {j page 17 In addition to this sale of "firm power", analogous to the contract signed with Inspiration Copper for power from Horse Mesa Dam, the contract between the Water Users' Associa- tion and CAlAPCO called for an official division of the territories served by each organizations' power distribution systems. The origins of CAlAPCO as an electric power company dated back to the beginning of the century, when it operated under the name Pacific Gas and Electric. In the years before the Salt River Valley Water Users' Association began supplying electrical power, CAlAPCO concentrated its activities in the valley's urban areas.

The company was not legally obligated to limit its operations within these areas, but it did so primarily because it was more economically advantageous. With the growth of the Water Users' Association's electric power system in the and however, the two organizations began to overlap and compete in various parts of the valley. Of course, much of the Water Users' Association distribution system was developed to serve widely scattered irrigation pumps in agricultural areas, but other Association customers were in urban areas that CAlAPCO considered part of its prime market area. Thus, in response to the growing conflict between the two organizations, the con- tract delineated in detail those areas of the Salt River Valley served by each.

In basic terms, CAlAPCO received rights to serve "all that territory within the boundaries of the City of Phoenix as now or hereafter established," along with "all of the present incorpo- rated towns or cities within the boundaries of the Salt River Project as they are now or hereafter constituted." Conversely, the Water Users' Association received exclusive rights to serve "all that territory within the Salt River Project" that had not been explicitly described as being within CAlAPCO's service area. 55 The result of this formal division of the Salt River Valley into non-competing service areas meant that CAlAPCO had agreed to limit its operations to only 15 percent of the lands held within the Salt River Project, whereas the company had previously covered 29 percent of project lands.

The advantage of the contract for CAlAPCO was that its newly defined service region was highly concentrated in already developed areas: the company would not have to fi- nance construction of a widespread distribution system to serve relatively minor rural consumers. In addition, CAlAPCO's agreement to accept kilowatts of "firm power" guaranteed it a reliable supply of electricity for SO years without forcing the company to reinvest any of its own money into expensive capital improvements to increase power generation capacity. In fact, it was estimated that a comparable steam-powered electric generating plant built by CAlAPCO to take the place of Stewart Mountain power would require annual expenditures of for fuel oil alone.

56 The advantage for the Water Users' Association was that CAlAPCO's guaranteed annual payments were sufficient to provide a solid financial basis for the Stewart Mountain project. As part of this project, the Water Users' Association would be able to increase the size of its power distribution system dramatically, practically guaranteeing that electricity would be available to anyone located within the Salt River Valley. The 11 : : Stewart Mountain Dam :? HAER No. AZ-1 2 II page 18 trade-off to the Water Users' Association was that it would have to assume several million dollars in debt obligations beyond those already incurred for the Roosevelt, Horse Mesa and Mormon Flat Dams, and it would have to assume the risk of building and operating the dam itself.

The new agreement meant that some members of the Water Users' Association located in Phoenix and other towns would now be required to purchase their electricity from CALAPCO. Because CALAPCO's power rates were historically higher than those charged by the Water Users' Association, this meant that those Association members faced with paying higher electric bills to the private utility would certainly be angered. To assuage these people, the Association offered to refund the cost differential between the two entities' power rates. In essence, this meant that the membership of the Water Users' Association would partially subsidize the operations of those members served by CALAPCO to equalize the rates paid by all.

57 After unanimously accepting Cragin's recommendation to proceed with the Stewart Moun- tain project in February the board of governors authorized a series of six proposals to be presented to the Association membership in a special election so that, in accordance with the Association's bylaws, they could receive final legal approval for the work at Stewart Mountain. Of course, the Association's agreement with the government con- cerning transfer of the Salt River Project to local control also stipulated that the Secretary of the Interior approve the issuance of any financial bonds by the Association.

58 Fears about receiving such approval were allayed by a February 1, letter from Elwood Mead, Commissioner of the Bureau of Reclamation, to the Secretary of the Interior (and officially approved by E.C. Finney, First Assistant Secretary of the Interior) in which Mead declared: The Stewart Mountain power development will be an asset to the Salt River Project in that it will increase the power revenues and it will also provide additional regulating storage nearer to the point of diversion which will permit closer regulation of irrigation water and thereby minimi7.e waste...

[furthermore] it is believed that the proposed contract [with CALAPCO] will increase the power earnings on the Salt River Project and thereby increase the security of the investment which the United States has made in this project. It will also make it easier for the Water Users' Association to meet its consttuction payments to the United States. It is recommended that the contract received the advance approval of the Department.59 With this endorsement, which presaged the official government approval of the project later in the year, no further obstacles stood to block construction of the Stewart Mountain Dam. However, approval from the Association membership was necessary in a special election, scheduled on March 20, by the board of governors. ti Stewart Mountain Dam ff HAER No.

AZ-12 :\I page 19 In this election members of the Water Users' Association were asked to ratify six proposi- tions that would empower the board of govern~rs to "issue bond_s of the Association in an amount not exceeding payable m not to exceed thirty years from the date of issuance thereof... and bearing interest rates not to exceed six per cent per annum for the purpose of constructing said i~provement a~~ undertaking designated as Stewart Mountain Development."60 In add1t10n to authonzmg the sale and repayment of these bonds, Proposition No. 2 sought approval of the plan to subsidize the power costs of Asso- ciation members who would be served subsequently by CALAPCO. Given the wide mar- gins of approval previou~ly_ given t?

the Mormon Flat an~ Horse Mesa bonds, there was little reason to suspect difficulty with the Stewart Mountam vote. When some Association members went to the polls on March they endorsed all of the propositions overwhelmingly. Of the total votes cast, not a single proposition received less than affirmative votes. The only problem was that the critically important Proposition No. 4, which authorized the million bond, received approval from only percent of the votes cast - just short of the three-fourths majority needed.61 The bond issue was essential to the project. When it failed, the directors stated: "each and every one of said, propositions Nos.

1 to 6 do not become effective.1162 The reason for the narrow defeat of the Stewart Mountain bond issue apparently derived from a small group of landowners who wished to limit the size of the Water Users' Associ- ation's debt. Rather than default on the CALAPCO agreement, the board of governors instead authorized a new election to resubmit the exact same six proposals to the member- ship for approval.63 Scheduled for May 8, this new election provided an opportunity for project supporters to allay any suspicions about the Stewart Mountain plan and to make sure that members in favor of the propositions showed up at the polls and voted.

To boost the Stewart Mountain project, a pamphlet was prepared, entitled "Salt River Valley Water Users Association Statement of Facts."64 This brochure spelled out the financial advantages of the proposed contract in simple terms, stressed the fact that CALAPCO's service area was to be decreased from 29 percent to 15 percent of Salt River Project land and reprinted in its entirety the endorsement made by Elwood Mead in his February 1st letter to the Secretary of the Interior. Support for the Stewart Mountain project was requested by George L. Johnson, a prominent Salt River Valley businessman, in a public letter to the president and board of governors of the Water Users' Association.

Vowing his "whole-hearted support of this development," Johnson stated: It would be a decided setback to have this development fail and make it necessary for the local Power Company to produce the power which they need to meet their demands, by steam development. This would take approximately each year out of the com- munity to be spent for fuel oil in Texas or California. The approval of this development by the water users will electrify the whole valley, making power aVailable for each farmer... your program of development has been so constructive that it is hard for me to understand why you should not have the unanimous approval of all your shareholders.65 :t Stewart Mountain Dam ti HAER No.

AZ.-12 /} page 20 On May 8th there was a 20 percent increase in the number of Association members who went to the polls compared with the March election. These people cast a total of votes, and this time all six propositions passed with the legal required majority. For the crucial Proposition No. 4, the affirmation rate rose to 82 percent. 66 The Stewart Mountain project was approved and ready to move ahead.

Stewart Mountain Dam: Financing On May 16, the board of governors authorized a "call for bids" to be disseminated through the financial markets requesting offers for the purchase of million in bonds at five percent interest to cover both the million approved for the Stewart Mountain development as well as an additional $1 million of existing debt that the Water Users' Association wished to refinance at a lower interest rate. 67 Interest rates nationwide were low at this time, and the board wished to reduce the Association's interest payments on some of the debt incurred by the Horse Mesa project by refinancing it as part of the Stewart Mountain bonds. Bids were received from five different invest- ment groups.

These proposals were judged by the extent of discount from face value each of the bidders was willing to offer. A syndicate led by the Detroit Trust Company offered to provide the Association with for every included in the bonds (a total of million for bonds with a face value of million). By far the best of the five bids tendered, it was accepted unanimously by the board of governors. 68 In accepting the offer from the Detroit Trust syndicate, the Water Users' Association agreed to deliver the bonds by July 15, Under normal circumstances this would not have presented any major difficulties.

But the Association members who had opposed approval of the Stewart Mountain development continued to press for abandonment of the project, and during the summer of they further attempted to block the mort- gaging of valley land. These efforts ultimately failed, but in the meantime they engen- dered uncertainty, at least within the minds of the financiers responsible for handling the sale of the bonds. As Cragin later described the situation: "copies of all the actions brought and pleadings thereof were forwarded ... to Gibson, Dunn & Crutcher, the attor- neys of the bond syndicate who contracted for the purchase of the bonds.

Obviously, this was for the purpose of interfering with the sale of the bond issue."69 The result of this legal maneuvering was that, in Cragin's words: "It became apparent we would not be able to deliver the bonds with their approving opinion within the time limit set by the contract of sale."70 mr Stewart Mountain Dam Jj HAER No. AZ-12 Ii page 21 . . . The financial consequences of this delay proved dramatic. It was not until August that all the legal obstacles could be resolved, and the Water Users' Association was prepared to consummate the sale of Stewart Mountain bonds.

During this time, however, the bond market had plummeted during the frenzied trading that preceded the Great Crash of The terms of the sale as finally negotiated were far less favorable, as portrayed succinctly by Cragin: The sale was made on May at for a 5% bond. The bond mark.et at that time was at the highest point within our recollection. By the time the litigation was practically settled and an approving opinion was available to the buying syndicated, the bond marlcet dropped over six points, the lowest in a generation. The highest price then obtainable was 93 for 5~% bonds. Ar.

this price there was no object in refunding the short-term bonds of the Association so that only were sold in place of the of the original sale.71 The new sales agreement for the bonds was made with a syndicate led by the First Securities Company of Los Angeles on August 25, the "execution delivery and sale of the bonds" formally made on September 72 With this, money was finally available to begin construction of the Stewart Mountain Dam. Soon Cragin was occupied with en- gineering matters related to the dam's design and construction.

Embittered by the delays that by his estimation had cost the Water Users' Association "largely in excess of half a million dollars, he later lambasted his opponents in an article on "Development of Hydro-Electric Power as an Aid to Irrigation" for the Transactions of the American Society of Civil Engineers: Mobility and ability to develop speed in financing are essential, but these are almost always absent in irrigation projects, practically all of which require votes of their members or stockholders for all substantial financing. One large power development in connection with irrigation requires a three to one majority for authorizing any expenditure greater than in any year. Bonds of this nature are always subject to legal contest by any portion of the minority.

Known examples of six months delay have been caused from litigation carried on by less than 1 per cent of the stockholders.74 if Stewart Mountain Dam ;if HAER No. AZ.-12 JJ page 22 Stewart Mountain Dam: Design In principal, the structural characteristics of the Stewart Mountain Darn represent an approach to engineering in which the shape of the darn is more impor- tant than the mass (or weight) of material in the structure. In this context, the simplest type of darn is one in which stone or rock is piled across a strearnbed in such quantities that the water that builds up behind it cannot exert sufficient hydrostatic pressure to move or dislodge the structure. The modem equivalent of this massive type of structure is the concrete or masonry gravity darn.

Although they may resemble arch darns in their curved plans, these structures rely upon the tremendous downward force of their mass to withstand the horizontal force exerted by the impounded water. Roosevelt Darn, for instance, is a typically configured curved gravity darn. In contrast to this massive tradition in darn design, darns can be built with such a relatively small amount of material that it becomes necessary that they be curved in plan to resist the hydrostatic pressure exerted by a reservoir filled with water. Usually termed arch darns to distinguish them from curved gravity designs, these materially conservant structures derive their strength from the structural characteristics of their shape, which is basically a bowed wall with the outside curve facing upstream.

Arch darns represent the structural tradition of darn design, in which the shape of the darn, rather than the amount of material used, is the critical factor in its structural strength. 75 Stewart Mountain Darn is an arch darn. The cross-section (or profile) of the arch is so thin that if it was built straight across the darn site in an effort to have it function as a gravity darn, it would quickly collapse under the pressure of a full reservoir. The great advantage of an arch design over a comparable gravity design is that the savings in material can be directly translated into lower construction costs. This distinction was of great interest in the Salt River Valley, especially in light of the excruciating cost of the gravity Roosevelt Darn.

76 When Cragin set out to implement his hydroelectric devel- opment plan for the Salt River in the early he opted not to follow in the footsteps of the Reclamation Service and build storage darns that adhered to the massive tradition exemplified by the Roosevelt Darn. Rather, when Cragin chose to build darns under the direct authority of the Salt River Valley Water Users' Association, he was fully aware of the organization's financial limitations. Thus, it was natural for him to gravitate toward design that would provide the Association with maximum service at a minimum cost.

The third of the three similar concrete arch structures built by the Water Users' Association along the Salt River during the period to the Stewart Mountain Darn was a direct outgrowth of the work undertaken on the earlier Mormon Flat and Horse Mesa Darns. 77 All three sites that Cragin had selected for his hydroelectric power -r (: Stewart Mountain Dam ff HAER No. AZ-12 JI page 23 storage darns were characterized by solid bedrock foundations capable of absorbing the relatively high stress that would be exerted on them by the arch dams. First of the three structures engineered by Cragin, the Mormon Flat Dam featured a variable radius - or constant angle - arch design.

In designing this structure in Cragin employed a simple mathematical equation known as the "cylinder formula" to determine the various dimensions of the structure. The cylinder formula allows the designer to calculate the thickness T of the arch by using the equation T = in which P represents water pressure, R represents the radius of the arch, and Q represents the allowable compressive stress on the concrete [e.g., 650 pounds per square inch]. In an ideal situation in which the arch is relatively thin and the foundation and canyon walls of a site are perpendicular to the floor, the cylinder formula could be relied upon to formulate extremely accurate approximations of the actual stresses within an arch dam.

The reliability of the cylinder formula decreases, however, once the arch is made thicker and the damsite topography becomes more irregular. Despite its practical limitations, the cylinder formula was used successfully for many years, first in the design of the Zola Dam in France 7). The first American example was the 64-foot-high, 450-foot-long Bear Valley Dam, completed in southern California in Decreasing in width from 24 feet at the base to three feet at the crest, the Bear Valley structure was the most slender masonry arch dam yet built. 78 ~ ,t .. . ~ 1ad.1:.1i 4 - ~- Y :f' I Figure 2. Bear Valley Dam. From Development of Dam Engineering in the United States.

Upon studying the formula T = it becomes apparent that if water pressure P and allowable stress Q are held constant, then the thickness T is directly proportional to the radius R of the arch. In other words, as the radius of the arch becomes smaller, the thickness will be reduced correspondingly. For the earliest arch dams designed using the formula, the radius of the arch was held constant so that the arch thickness was depen- dent solely upon the water pressure exerted at any elevation. But by the early cen- tury, engineers understood that more materially efficient designs could be developed by {i Stewart Mountain Dam :J HAER No. AZ-12 :.J page 24 . .

varying the radius of the arch, thus creating so-called "variable radius" or "constant angle" designs better suited to the shape of most dam sites. In reality, virtually all dam sites are narrower at the bottom than they are at the top, forming V-shaped sites. By building a constant angle arch in a V-shaped canyon, a dam could be designed that more resembled a cone than a cylinder when viewed from upstream. Because this conical shape provided for a reduced radius R in the lower elevations of the structure, it also allowed the thickness of the arch to be substantially reduced over that required for a standard arch dam designed using a constant radius. The first constant angle dam was built near Juneau, Alaska, in using a design pre- pared by California engineer Lars Jorgensen.

Jorgensen had received a patent for his design of constant angle arch dams two years before, and, although the legal validity of such a patent was dubious, he became closely associated with the proliferation of constant angle arch dams throughout the United States over the next twenty years. 79 When Cragin began the engineering for the Mormon Flat Dam early in he recog- nized that use of a constant angle arch dam could save considerable quantities of concrete and, therefore, money. He used the cylinder formula to determine the dimen- sions of the arch, quickly devising a suitable structure for the site. In so doing, he attracted the ire of Jorgensen's Constant Angle Arch Darn Company, which tried to block Cragin from using a design which Jorgensen claimed infringed upon his patent.

Cragin considered Jorgensen's claim legally indefensible. Consequently, the Water Users' Association and the Constant Angle Arch Dam Company mounted a seven-year legal battle over the right to use the constant angle dam design. Also based upon constant angle designs, the Horse Mesa and Stewart Mountain Dams were eventually entangled in the dispute. Finally, in the two parties agreed to an out-of-court settlement, in which the Association paid Jorgensen to drop the case. Cragin and the Water Users' Association maintained that Jorgensen's claims could not withstand a legal test, but they eventually decided it was more prudent to settle rather than take the case to court. 80 Cragin again used the cylinder formula in his initial design for the Horse Mesa Dam.

Bureau of Reclamation engineers balked at this, however, instead requiring a new design technique that would supposedly provide for a more accurate calculation of stresses with- in the structure. The basic theoretical limitation of the cylinder formula was that it could not account for either the irregular shape of the dam site or any internal stresses in the structure caused by deformations or deflections of the concrete under the force of the water. 81 During the engineers had gradually begun to develop a method of analysis that would accommodate both of these deficiencies in cylinder formula.

82 Eventually known as the "trial load" method of arch dam design, this new technique in- volved seeing the arch dam as a structure in which arch action and cantilever action (which relates to the way the lower part of an arch dam actually resists water pressure like a gravity dam) combine structurally to hold back water in a reservoir. It is because f( Stewart Mountain Dam Ji HAER No. AZ-12 ]( page 25 of the irregular shape of their sites that arch darns must function to some degree as gravity structures.

In the trial load method of analysis, the deflections of the arch elements and the cantilever elements are calculated using the elastic theory and then, through a series of reiterations, the dimensions of the design are refined so that the deflections for the arch and cantilever elements coincide with one another. 83 Variations on the trial load method had been used to analyze the stresses in existing dams but had never before been used to calculate the profile of a new structure. To test the practical application for this novel design strategy, the Bureau of Reclamation engineering staff developed the final design for the Horse Mesa Dam itself, using the trial load method.

When the time came to prepare plans for the Stewart Mountain Dam, however, the Asso- ciation took the lead in developing a design based upon the trial load method. In fact, Cragin initially thought that the relatively wide canyon at Stewart Mountain would be best suited to a multiple arch dam; after studying the conditions at the site by drilling down to bedrock, however, he realized that the foundations would be too deep - ninety feet below the surface in some places - for economical use of a multiple arch structure. He instead focused attention on a single-arch design.

84 Anticipating that the Bureau of Reclamation would almost certainly require that the Stewart Mountain Dam be designed in a manner similar to that used for Horse Mesa, Cragin used the trial load method to develop a variable radius structure. He submitted the design to Reclamation early in after initial construction had already begun at the site, hoping for a quick approval. The Stewart Mountain Dam as built followed Cragin's initial design in large part: a single, large concrete arch that closed off the deepest parts of the site, with two large concrete abutments to help absorb the thrust of the arch, two short gravity sections to connect the abutments to the edge of the canyon walls, and a lengthy overflow spillway with movable gates at the east end of the struc- ture.

Reclamation accepted the overall concept of the design and approved Cragin's maximum allowable stress in the concrete arch of 650 pounds per square inch. The design changes that Reclamation engineers did recommend primarily involved details on the massive concrete abutments and the arch profile itself. 85 The Bureau-approved design involved widening the upstream face of both abutments by two feet and adding reinforcing steel to the abutments such that steel would comprise at least three-tenths of one percent of the volume of each abutment. These changes helped assure that the abutments would be massive enough to absorb the thrust of the arch and that they would resist shrinkage cracks while they were curing.

In addition, the Bureau determined that the upstream face of the variable-radius arch should be constructed so that the upper elevations not overhang the lower parts of the structure. In other words, the "conic-shape" of Cragin's original design meant that the upstream face of the dam was not built with a flat, vertical face. The Bureau considered such an overhang to be difficult to build and required the modification before giving final approval to the design. f: Stewart Mountain Dam :t HAER No. AZ-12 )i page 26 . . , --- -- E~~~~=-- Figure 3. Plan of Stewart Mountain Dam arch. From Salt River Project. The effect of this change meant that extra quantities of concrete would have to be added to the base of arch to eliminate the overhang and create a vertical upstream face for the structure.

As a result of the Bureau's requirement that the abutments be widened and the upstream overhang be eliminated. Because the bedrock foundation proved deeper in some areas than the diamond borings had indicated, the amount of concrete required to build the dam increased substantially over Cragin's original estimate. As built, the Stewart Mountain Dam consumed cubic yards of concrete - some more yards than originally planned. After granting approval to the modified design for Stewart Mountain Dam in April the Bureau of Reclamation retained an interest in the structure as it was being built. In late October Bureau Chief Design Engineer John L.

Savage noted during his inspection of the foundations: There is every evidence that the excavation has been made by proper methods without excessive blasting... the design of the dam has already had the consideration and approval of the Bureau of Reclamation. Based on the superior character of the foundation rock and having in mind the high quality of the concrete aggregate and the rigid inspection under which the work is being done, it is my opinion that the Stewart Mountain Dam can, when completed, be classified as a permanently safe structure.86 :@ Stewart Mountain Dam 1( HAER No. A'Z-12 1[ page 27 Stewart Mountain Dam: Constrnction With the funding in place and the design finalized, the Water Users' Association soon began full-scale construction of the dam.

The Mormon Flat and Horse Mesa projects had both been built using force account labor, without outside contractors, and Cragin chose to pursue construction at Stewart Mountain similarly. All laborers would be hired directly by the Association, under Association supervision, and all construction equipment and materials would be purchased directly by the Association. 87 Unlike Roosevelt Dam, which suffered considerably from its relatively remote location, frequent floods and primitive access roads 25 years earlier, the Stewart Mountain site benefited both from the pre-existence of three large storage dams on the upper Salt River and from its close proximity to the Phoenix/Tempe/Mesa community in the Salt River Valley.

The river's flow here was already regulated by the three upstream dams, permit- ting essentially uninterrupted construction on the lower dam. 88 The site's proximity to the lower Salt River Valley meant that communication and transportation to and from the dam could be undertaken expeditiously. Once the roadway connecting the damsite to the Apache Trail (State Route 88) that extends from Mesa to the Roosevelt Dam was com- plete, the 40-mile automobile trip from Phoenix could be made in "a little over an hour."89 Construction of this roadway link constituted one of the earliest aspects of the project.

The nearest railroad passed some 23 miles from the site, and, given that any rail line built to provide access during construction would serve little useful purpose after the dam's completion, construction of a spur line appeared impractical. Materials would in- stead be delivered to the site by trucks over a branch from the Apache Trail. The road to Stewart Mountain diverged from the Apache Trail at a point about nine miles east of Mesa and then extended another twelve miles in a northeasterly direction before reaching the Salt River at a location known as Blue Point. After crossing the river on a wooden bridge built as part of the Stewart Mountain project, the road followed the river's north bank for about three miles before reaching the damsite.

Construction of the 30-foot-wide, dirt-paved roadway took place during the fall of by November the bridge was in service, and by December all grading of the right-of-way was finished.9 Built to accommodate topographic conditions near the dam, the bridge at Blue Point also served as a kind of security checkpoint to regulate access to the construction site. Even then, tourists were driving up from the Salt River Valley along the Apache Trail to view the dams and reservoirs, and "the number of tourists and sight - seers [at Stewart Mountain] was kept down by requiring written passes in order to cross the bridge, where a watchman was on duty at all times. II Stewart Mountain Dam ti HAER No. AZ-12 ti pao-e 28 . . . 0 While the road was graded, preparatory work at the damsite had already begun.

Among the first priorities was the erection of a temporary camp to supply workers with the basic necessities of room and board. Although the site was relatively close to the cities of Mesa, Tempe, and even Phoenix, the Water Users' Association considered it important to provide housing facilities within a short distance of the construction area. This would eliminate any commuting problems - en~e troubles, flat tires, etc. - that might disrupt the regular attendance of workers, and 1t also insured that the road to the construction site would remain clear for hauling equipment and construction supplies. The broad, expansive topography at the Stewart Mountain site was ideally suited to construction of a workers' camp a few hundred yards downstream from the dam.

92 Essen- tially completed by December 1, the camp consisted of a large mess house, a first- aid station, bathhouse, a time keeper's office and several clusters of housing facilities. The largest group of living quarters consisted of 43 wood frame bunkhouses designed to provide comfort for six workers each. These bunks were intended for use by unmarried men or by men who voluntarily had separated themselves from their families. The large number of relatively small bunkhouses was intended to allow operation of day and night shifts with minimal disruption between the two.

93 It was also reported that the use of many small bunkhouses, rather than one large residence hall, could have "provided effi- cient segregation in the event of necessity for medical purposes." As it turned out, though, conditions throughout the entire construction site proved extremely safe and sanitary, with "not a single casualty or serious injury" reported during the entire 17-month construction period. 94 In addition to the 43 bunkhouses, the camp included separate housing facilities for men with families. The single men were apparently housed without regard to ethnicity, with Angl()s, Mexicans and Indians (Apaches) quartered together. The families, however, were segregated by ethnic groups, as explained by T.A.

Hayden: "A separate group of buildings housed white workmen with families [while] Mexican and Indian laborers with their fam- ilies had quarters in a third and fourth group."95 The segregation of living groups on the basis of national or ethnic origin was not unusual for the time period; the institution of this type of living pattern merely reflects that the camp at Stewart Mountain adhered to the social norms of American society in the pre- World War II era. It is impossible to ascribe exactly how many people lived at the site and participated in the construction process.

96 But based on the number of six-man bunk- houses erected and the likelihood that the separate quarters for married men supported at least twenty families for each of the Anglo-American, Mexican and Native American ethnic groups, the work force at the site probably reached a maximum of approximately 300 men during the peak of construction activity. Had the dam site not been extremely spacious with room for many phases of construction to proceed simultaneously this work force estimate might appear to be too high. However, in light of how rapidly the huge structure reached completion, the estimate of a 300-man work force appears reasonable. fl: Stewart Mountain Dam mf HAER No. AZ.-12 fi page 29 Figure 4. Site Plan of Stewart Mountain Dam. From Salt River Project.

The early stages of construction on the dam itself divided into three broad categories: 1) assembly and organization of the equipment and machinery necessary for construc- tion; 2) excavation of the foundations to bedrock; and 3) erection of an upstream cofferdam and a wooden diversion flume to channel the flow of the Salt River so that it would not disrupt operations at the site. Although the Roosevelt, Horse Mesa and Mormon Flat Dams protected the Stewart Mountain site from uncontrolled flooding, the upstream dams did not stop the river's flow entirely during the construction period. Irrigators in the valley depended upon a steady river flow for their crops, and water was constantly released from the Mormon Flat Reservoir through the Stewart Mountain site.

To control this flow, the Water Users' Association built a timber/stone diversion dam approximately 30 feet high and 400 feet long at a location about 250 feet upstream from the site of the main dam. At the western end of this diversion dam, an opening was built that allowed water to flow into a 450-foot long wooden diversion flume with a cross- section of 30 feet wide by 11 feet high. This diversion flume passed directly through the center of the dam site and did not release its flow until a point well downstream from where activities at the J, Stewart Mountain Dam }) HAER No. AZ-12 :r page 30 site could be disturbed. Operational by the beginning of April the diversion flume remained in use throughout the remaining eleven months of construction.

In fact, an opening was left in the dam's arch to allow the diversion flume to remain in service until the last possible moment; this opening was the last part of the arch to be blocked off, and it was not filled with concrete until the dam was ready to impound water. In concert with the construction of the diversion flume, early efforts at the site focused on clearing away debris from the foundation. Bedrock here consisted of "a hard gray granite, somewhat weathered at the surface but firm and dense below the weathered portion. Excavating to bedrock presented no major difficulties across most of the dam's base, and construction crews dug the foundations using four dragline excavators with bucket capacities varying from three cubic yards to of a cubic yard.

98 Resembling steam shovels, dragline excavators scraped the overburden away by dragging a large bucket across the excavation area. Once the dragline excavators had scooped most of the soil and loose rock from the bedrock, work crews removed the remaining weathered rock or fissured stone that might diminish the solidity of the bedrock. As a final step, the men sprayed the foundations with pressurized water. Sometimes referred to as "hydraul- icking", this process was frequently employed in dam construction to clean the foundation of loose or unstable material that might weaken the bond between the rock foundation and the concrete of the dam.

99 Dragline excavation and hydraulicking could be used for the foundations over most of the dam's length, but unusual conditions at the arch's east end necessitated additional steps to reach the bedrock. By a quirk of nature, the bedrock here lay at a depth some 90 feet below the streambed; to excavate to this level, engineers for the Association devised a cofferdam to enclose the deep pit. This protective cofferdam was built by driving Lackawanna steel interlocking I-beams down into the soil surrounding the deep bedrock zone using a compressed air-powered hammer. 100 The interlocking piles define a roughly rectangular area 210 feet long and 4 7 feet wide.

As later noted: Great care was taken to stop driving when any pile encountered a boulder and not to attempt to push the pile or piles deeper until the excavation inside the cofferdam had exposed the rock and permitted its removal. By this means a perfectly aligned and water tight job was secured. 101 Because dragline excavators were able to remove a substantial quantity of overburden before it became necessary to start driving the piles for the special cofferdam, these piles only needed to extend a maximum of 55 feet to bedrock. To prevent the inward collapse of the piles and to protect the area where excavation - and later concrete construction - would occur, heavy timber trusses spaced 17 feet apart were erected across the 47-foot- wide space defined by the outer edge of the cofferdam.

By thus spacing the timber sup- port trusses, it was possible for workers to carry out all required excavation work and later construct the wooden forms for the concrete arch. :t Stewart Mountain Dam \} HAER No. AZ.-12 (} page 31 As with practically every darn built, underground water flow, or seepage, passed through the Stewart Mountain site throughout construction, forcing the engineers to remove it before any difficulties developed. The drainage flume helped to minimize seepage at the site, but the depth of the east-end excavation pit required additional dewatering to avoid impeding the construction process.

The seepage at the bottom of the cofferdam here was drained using 150-horsepower electric pumps with a capacity of lifting 60 cubic feet of water per second a vertical distance of 100 feet for discharge into the diversion flume. 102 Once excavation had proceeded to bedrock and all loose rock and debris had been re- moved, only one further step was necessary before the process of erecting forrnwork and pouring concrete could begin. This last step involved the injection of cement grout into the foundation as a precautionary measure to help eliminate the possibility that extreme amounts of seepage through the foundations might occur once the darn began to hold water.

Grouting is an engineering procedure commonly undertaken as part of darn con- struction and was hardly unique to Stewart Mountain. The process involves drilling small holes into the bedrock foundation of a site and then forcing wet cement down into these holes. The intent was to fill underground cracks or fissures with cement in order to reduce the ability of water to seep through the rock. A total of 95 grout holes were drilled, varying in depth from 25 to 100 feet and in diameter from 1 to 1 \ inches. To fill all of these holes, only 143 bags of cement were required - an indicator of the solidity of the foundations at Stewart Mountain.

103 Every darn has experienced some kind of seepage or leakage through its foundations, and although some seepage through the Stewart Mountain site has occurred since the time the reservoir was first filled, the quality of the Stewart Mountain foundations has always been considered to be very good. As Cragin later described: At. the Stewart Mountain Dam it was possible to carry on operations over practically the entire length of the structure at the same time. The smface excavation and removal of checked, weathered or disintegrated rock was completed at both ends of the dam, and concrete poured while excavation in the deep pit in the [eastern half of the] stream bed was still in progress.

104 What this meant is that the processes of excavation and construction were not undertaken at completely separate times. Rather, once excavation was finished in one part of the dam, this might well become an area where the pouring of concrete would start long before excavation for other parts of the structure was complete. For example, excavation at Stewart Mountain started on January 10, and, especially for the deep work at the eastern section of the arch, excavating work continued through late that October. 105 During most of this same period, concrete pouring proceeded at a brisk pace within those parts of the damsite where all excavation had been completed. :t Stewart Mountain Dam J: HAER No. AZ-12 :t page 32 . . .

The first concrete was poured on March 13, forming a base for the wooden diver- sion flume through the center of the arch; the first concrete for the east abutment was placed on April 17, while the first concrete for the west abutment was placed on June 5, Both of these abutments were completed by early October. Construction of the western section of the arch began in early August construction of the east arch section did not commence until early October. The spillway and gravity sections adjacent to the east abutment were finished by the end of December final work on the arch continued through the early months of and the entire structure was de- clared complete on March 8th of that year.

Construction of the concrete powerhouse began in October and the exterior of the building was complete by December During the early part of the turbine generator and other electrical equipment were installed. "The dam and power plant were finished simultaneously," Cragin reported, "the latter being placed on the line in a test run the same day the last concrete was deposited. -a. . . I i ~ I I I ' I I I -- -- Figure 5. Stewart Mountain Dam Powerhouse. From Salt River Project. /: Stewart Mountain Dam 1) HAER No. AZ.-12 \( page 33 Before describing the processes of concrete handling used for the dam, it is worth discus- sing some of the overriding engineering considerations that guided the structure's erec- tion.

The east and west abutments were to be built well before the main arch, because they were intended to serve as immovable monoliths that would absorb the arch's horizontal thrust. The abutments were thus to act as integral parts of the foundation in resisting pressure exerted by the arch. For this reason Cragin and his engineers wanted to insure that the poured concrete buttresses were well cured before construction of the arch. 107 They were also concerned about the formation of shrinkage or temperature cracks during the pouring of the arch itself. To avoid this problem, the engineers divided the arch vertically into five separate sections, each of which would ultimately join with the others to form the complete arch.

This method of construction allowed each arch section to harden separately, without concern that the entire arch might crack while different parts of the structure hardened. Large vertical grooves were formed into the ends of both the buttress faces and the faces of the five arch sections to help insure that the various components of the arch could ultimately be joined together into a solid structure. To waterproof the arch contraction joints, "water gas tar" (a type of sticky asphalt) and waterproof copper strips were placed on their upstream sides. 108 A final means of protecting the main arch from leakage involved the installation of a tem of pipes within the arch that would allow cement grouting of the various expansion joints.

When the foundation of the dam site was grouted, it was necessary to drill lengthy holes in the bedrock that were later filled up with cement. In contrast, the process of grouting the arch itself involved placing \-inch pipes at three-foot intervals a short distance from the face of each arch section. These pipes extended the entire height of the arch. At eight-foot intervals, horizontal pipes were connected to the vertical grouting pipes, providing a means of carrying cement grout directly to the face of the arch sections. Thus, grouting could be forced down into the entire length of the contrac- tion joints between the arch sections.

To insure that the grout did not spill out uselessly through the downstream edge of the joint, a special copper strip was installed that was similar to the one used as a waterproof barrier at the upstream edge of the contraction joint. It was considered desirable to apply the grout at a time when the arch was under no appreciable hydrostatic load and at a time after all parts of the structure had hardened to their final dimensions. Consequently, the grouting procedure was undertaken several months after the dam was considered complete.

109 The dam erection process can be broken down into three distinct phases: 1) fabrication of wooden formwork into which the concrete would be poured; 2) mixing of the cement, sand and gravel into concrete; and 3) transportation of concrete from the mixing plant to the various parts of the damsite and pouring the concrete into the forms. To accom- plish these interrelated tasks, a wide variety of material and equipment - much of it used previously at Mormon Flat and Horse Mesa - was brought on-site by a fleet of ten five- /} Stewart Mountain Dam :t HAER No. AZ-12 if page 34 . . . ton, gasoline-powered trucks.

110 Power for construction was provided both by individual gasoline engines and by a volt electric transmission line that connected the Stew- art Mountain site with the Water Users' Association substation at the Granite Reef Dam about twelve miles downstream. Completed late in this transmission line provided power for most of the works undertaken at Stewart Mountain. Once the dam was com- plete and the powerhouse became operational, this transmission line was used to carry electric power from the Stewart Mountain Dam for use in the greater Salt River Valley. m The concrete mixing plant was erected on the east bank of the Salt River immediately downstream from the damsite.

The purpose of the mixing plant was to provide a means of storing the cement, sand and gravel in close proximity to the concrete mixers so that the various ingredients would be readily available. In total, barrels of cement were hauled in by truck for use at Stewart Mountain and delivered by chutes into a large shed above the mixers. 112 Cement was transported from the shed to the mixers by an elec- trically powered, 16-inch-wide conveyer belt. This belt ran the entire length of the shed and extended about 100 feet upstream to the mixers. 113 The other components of the concrete were obtained directly at the dam site and did not require trucks to haul them in.

Rock and stone obtained during the excavation process were dumped by dragline excavators into "grizzly" rock-crushers designed to reduce the aggregate to a manageable size. After passing through the grizzly, the crushed rock was carried by a 40-foot-high bucket elevator to the top of the main aggregate storage bin. The material'then passed through a 6-foot-by-30-foot revolving screen that separated the rock into sand, gravel (i.e., stones up to about \-inch in diameter) and rock (i.e., stones up to 3 inches in diameter).

114 The sand dropped by chute into a 1000-cubic-yard- capadty compartment at the southern end of the storage bin; a 24-inch-wide conveyer belt carried the gravel into a 2000-cubic-yard capacity compartment in the center of the storage bin, while another 24-inch-wide conveyer belt carried the rock to a 1000-cubic- yard-capacity compartment at the northern end of the bin. Delivery of aggregate from the large storage bin to the small bins directly connected with the mixers was accomplished in a two-step process. Material from the large bin was dropped onto a separate 24-inch-wide conveyer belt that ran beneath the three storage compartments.

This conveyer belt carried the various sized aggregates in an upstream direction where they were delivered into a 45-foot-high bucket elevator that lifted them up into small storage bins located directly above the mixers. These smaller bins provided a storage capacity of 30 cubic yards for the sand and rock and a capacity of 60 cubic yards for the gravel. m When it came time to mix the concrete (which was usually carried on continuously for hours at a time), the cement was brought in from the cement shed and dumped into one of two 1-cubic-yard concrete mixers. Sand, gravel and rock were then dumped into the mixer, and as the mixer started turning, water pumped from the diversion flume was :J Stewart Mountain Dam {} HAER No. AZ-12 i{ page 35 added to create a wet mix.

No records of the actual proportions of cement:sand:gravel used for the mix have been discovered, but this ratio was probably close to 1 This was commonly used for concrete in large dam projects during the early century. If anything, the proportion of cement in the mix was perhaps even greater than this esti- mate because it was reported that "additional cement was occasionally added to keep up the water-cement ratio where operating conditions required a rather wet mix." 116 The mixers operated at a combined maximum capacity of cubic yards of concrete per day.

Compression tests taken 28 days after various concrete samples had been poured indicated an average crushing strength of pounds per square inch (psi) and maximum of psi - sufficiently greater than the psi strength required by the specifications. 117 Once mixed, the concrete was delivered to various parts of the damsite for pouring. The time available before the hardening process began was about minutes; if the concrete had not been properly placed after this time, then prudence dictated that it be declared unusable and discarded. Given that the Stewart Mountain site stretched out for more than feet, Cragin needed to find a way in which wet concrete from the cen- tral mixing plant could be quickly and economically delivered to all parts of the dam.

The search was not that difficult, really, and the engineers soon settled on a popular system of conveying concrete that had been developed and popularized by the Insley Manufacturing Company of Indianapolis in the early 118 The Insley system involved hoisting the wet concrete up a tall tower in the center of the construction site and then letting it fl.ow through large, hinged chutes that could be maneuvered to reach any part of the structure. The advantage of this system was its sim- plicity and efficiency: once the concrete was pumped to the tower's top, it could fl.ow by gravity to the darn section then being poured.

Its major drawback was that concrete could have a tendency to "separate" into its constituent parts of cement, sand and gravel, a tendency that was exacerbated by the use of "wet" concrete suitable to being chuted for distances of several hundred feet. The engineers erected two 340-foot high, bolted Insley towers at Stewart Mountain. The base of this double tower was located directly adjacent to the concrete mixers so that once a batch of wet concrete was ready, it could be loaded into a large bucket attached to one of the towers and then hauled upwards. The height of the hoist would depend upon how close to the tower the concrete was to be placed.

For locations close to the tower, the material might only be lifted 75 or 100 feet; for locations at the extreme ends of the site it could be lifted over 300 feet. Once the concrete had been hoisted to the appropriate height, it was then dumped into a system of 20-inch diameter, semi-circular chutes. These chutes were supported by a system of three, two-inch diameter steel cable "skylines" that extended over the top of the Insley tower and were anchored into the sides of the canyon surrounding the damsite. Varying in length from feet to if Stewart Mountain Dam if HAER No. AZ-12 t: page 36 . . . feet, these skylines supported most of the chutes. However, at the western end of the dam, they were supplemented by a derrick crane set upon the top of an 80-foot-high wooden tower.

The use of this derrick provided more flexibility in moving the chutes around while building the west abutment and powerhouse. 119 Before any concrete could be mixed, hoisted up the Insley tower and then delivered through the chuting system, it was necessary to construct wooden formwork to hold the wet concrete in its proper shape as it cured. It was not necessary, or even desirable, to construct all of the necessary formwork for an arch section before starting to mix and pour the concrete. Instead, formwork would be built in sections about 7 to 10 feet high and then filled with concrete delivered via chutes.

The concrete would be allowed to harden for several days and then the lower sections of the formwork would be struck down while additional sections of new formwork were built above the previously poured areas of concrete. The level of carpentry skill involved in building the forms did not need to be particularly demanding, at least if the engineers on site were careful to oversee the work and make sure that necessary dimensions were maintained. For most of the arch, no steel reinforcement was placed within the concrete. However, in that part of the arch where the four penstocks were located, a substantial grid of steel beams was erected to insure that the penstock openings did not precipitate cracking in the concrete.

These steel members were actually components that had originally been used to form the cofferdam around the foundation for the eastern section of the arch. 120 Once this cofferdam had served its purpose, the interlocking steel members were pulled from the pit and many were reused as reinforcing for the arch. Other areas of reinforce- ment were the two massive abutments (which were reinforced primarily to help prevent shrinkage cracks) and the piers for the Tainter gates in the spillway. As with the abutments, arch and spillway sections, the construction of the powerhouse was implemented by erecting wooden formwork and then filling it with concrete deli- vered by the Insley chuting system.

The powerhouse shell was essentially complete by December and during the first two months of all the necessary turbine and electrical generating equipment was installed. This work was handled expeditiously, largely because the single turbine/generator unit used at Stewart Mountain was a rela- tively small, standardized design that did not pose any significant problems to assemble and make operational.

Similarly, the valves installed at the downstream side of the out- let penstocks used simple designs that posed no problems when they were installed in early In fact, the two needle valves installed to control the flow out of the 7-foot penstock adjacent to the powerhouse were quite familiar to the Water Users' Association engineers - they had previously been installed at both the Roosevelt Darn and Mormon Flat Darn before finding a final home at Stewart Mountain. 121 ?? Stewart Mountain Dam ): HAER No. AZ-12 }\ page 37 ... ,., ,, __ _ ,, ., _., , ,, __ ,_ t r - I ~ -., AJ,tJ PT 1" Figure 6. Detail of Stewart Mountain Dam Tainter Gate. From Salt River Project.

Construction of the Stewart Mountain Dam came to a conclusion on March 8, when the final concrete blocking off the space where the wooden diversion flume intersected the arch was put in place. 122 Soon thereafter, electric power was first generated in the Stewart Mountain powerhouse and "placed on the line in a test run. Thus, in a period of less than eighteen months the Stewart Mountain Dam went from the planning stage to fully functioning, physical reality. In the end, the dam incorporated cubic yards of concrete into its structure (which in tum required barrels of cement to be hauled to the mixing plant).

In addition, the dam required tons of steel reinforcing, over 2 million board feet of lumber for the diversion flume, sheds, aggregate bins, formwork, etc., excavation of cubic yards of rock, and excavation of over cubic yards of loose dirt. 124 The cost of construction exceeded the original estimate of million by only this modest cost overrun was caused by the need to pour an additional cubic yards of concrete into the unexpectedly deep foundations excavated along the eastern section of the main arch. 125 ::f Stewart Mountain Dam :/ HAER No. AZ-12 J: page 38 , . Conclusion Smee its completion, the role in the regional economy of the Stewart Mountain Darn and Powerhouse has remained essentially static.

A few subsequent altera- tions have been made to the physical plant, described later in this section. But before discussing the operational history of the Stewart Mountain Darn, it is worth commenting upon how the overall Salt River Valley Users' Association's electric power system fared following the completion of the fourth - and last - major storage dam on the Salt River. When Stewart Mountain came on-line in the spring of the United States was in the initial throes of the Great Depression. Central Arizona's economy was heavily affected by the Depression, as were all parts of the country dependent upon agriculture.

Before the beginning of the crash in October the Association had completed a million expansion of its electric power distribution system and increased the numbers of its members receiving power to over 126 Completion of the Stewart Mountain Darn six months later culminated the expanded hydroelectric power generating and transmission system that Cragin had first proposed in By the new facilities had increased the Association's generating capacity from kilowatts to kilowatts. This allowed the Association to increase its kilowatt-hour production from 85 million to 270 million, and its power revenues increased fourfold from to million during the period 127 But the effect of the Great Depression soon had a deva- stating impact on the economy of the Salt River Valley.

Between and the annual value of crops grown in the valley decreased from $25 million to less than $10 million. As a reflection of this, between fiscal years and the Water Users' Association's net income from power sales fell from over to a meager 128 Some of the Association's immediate problems were caused by a serious drought in that reduced the amount of water available for hydroelectric power production. Even with an increase in water supply, however, the local power market remained weak throughout the it was not until the country's entry into World War II late in that the regional economy began to recover.

129 During the 1930s.the financial obligations incurred in constructing the hydroelectric power dams of the were met only by delaying payments to the federal government for the original debt. 130 The bonds that financed construction of the Stewart Mountain Dam never went into default, and the structure has always remained under the control of the Water Users' Association. Despite the financial problems that afflicted the Water Users' Association electric power system in the the Stewart Mountain Dam, with its 13,000-kilowatt capacity, remained an important component of the overall system. it Stewart Mountain Dam it HAER No.

AZ-12 }I page 39 During its sixty years of operation, the Stewart Mountain power plant has undergone no major expansion and, aside from the rewinding of its generator for 60-cycle output in little change in terms of operation or design. 131 As has been the case since the plant first came on-line, power generation at Stewart Mountain has been controlled com- pletely by the need to release water for irrigation purposes in the Salt River Valley. The release of water through the powerhouses at Roosevelt, Horse Mesa and Mormon Flat is often undertaken for power generation without regard to irrigation needs.

As the last storage structure above the Granite Reef headgates, however, the Stewart Mountain facil- ity is operated in direct response to the valley's irrigation and domestic water supply demands. It is essentially for this reason that there are no plans to upgrade or alter the existing power generating facilities at the site. Because power generation at Stewart Mountain will always be secondary to irrigation and domestic water supply demands, there is little incentive to invest in expensive new equipment. In civil engineering terms, the history of Stewart Mountain Dam has been more complex than its development within the context of electrical technology.

The first major altera- tion to the dam came in when the channel downstream from the spillway was lined with reinforced concrete to create a solid apron that would provide protection against erosion. First proposed in this work was carried out with other, more substantial spillway improvements at Horse Mesa and Mormon Flat Dams.

132 The cost of building the concrete spillway at Stewart Mountain was approximately the funds for which were obtained by a special agreement with the Bureau of Reclamation signed in late November This contract, which also covered the construction of the new Bartlett Dam on the Verde River and spillway work at the other dams on the Salt River, was federally financed by a new, interest-free loan of $6 million obtained under the authority of the Emergency Relief Appropriation Act of 133 Construction on the Stewart Mountain spillway started in January and was complete by the end of the year. 134 The only other major engineering work associated with maintenance of the Stewart Mountain Dam concerns the proliferation of a chemical reaction within the structure's concrete.

Known as "alkali-aggregate reaction," this phenomenon is caused by an inter- action between alkalis present in cement and natural siliceous materials found in many types of stone aggregate used for concrete. When mixed together, high-alkali cement and reactive aggregates can cause relatively minor surface cracking of the concrete as well as a noticeable swelling or expansion of the overall structure. This latter effect can be quite worrisome, especially in structures such as large dams where the increase in size can measure several inches. 135 By the late it was noticed that the roof of the Stewart Mountain powerhouse was separating from the downstream face of the dam - an indication that the arch was expan- ding in size and slowly moving upstream.

136 Although the movement of the dam as subsequently measured in the could be calibrated in terms of inches, even this relatively small amount of displacement was cause for concern. Following the end of \i Stewart Mountain Dam : HAER No. AZ-12 r: page 40 . . . World War II, the Bureau of Reclamation undertook an examination of the interior of the dam by drilling a 24-inch diameter hole into the structure and removing large concrete samples for laboratory analysis. 137 This analysis subsequently revealed that the structural effect of the alkali-aggregate reaction was not such that the overall integrity of the con- crete, especially in the interior of the structure, was in danger.

138 Because the alkali-aggregate reaction is one that is facilitated by the presence of water, it was decided that the best thing to do would be to regrout the construction joints of the entire structure with a fresh infusing of cement. An initial regrouting was undertaken in with the placement of 189 bags of cement applied into the structure under a pressure of 60 pounds per square inch. 139 This grouting work had the effect of reducing the expansion process from approximately one-half-inch per year to one-eighth inch per year, prompting the Water Users' Association to undertake an even more extensive grout- ing effort in late This new work involved the drilling of 79 \-inch diameter holes with a total length of over feet into the interior of the structure.

Over 950 bags of cement were infused into these holes in an attempt to waterproof the structure further. 140 Since the completion of the second round of grouting, the expansion of the Stewart Mountain Dam has stabilized, and the effect of the alkali-aggregate reaction is no longer considered to pose a long-term structural threat. The dam is still monitored regularly to detect further movement. In an additional effort to reduce the tendency of the dam to expand, its downstream face was painted white in and repainted in as a means of limiting solar energy absorption. Finally, the stability of the western abutment in regard to sliding was strengthened by the addition of cubic yards of concrete to increase. its mass, and hence increase its ability to resist the thrust of the arch.

141 These changes have certainly altered the structure from its condition at the time of completion in but, overall, the Stewart Mountain Dam has undergone only a modest amount of change during the past sixty years. Endnotes Descriptive data on the Stewart Mountain Dam is taken from: T.A. Hayden, "Salt 1 River Project, Arizona: Irrigation and Hydroelectric Development by Salt River Valley Water Users' Association - Six Major Dams," Westem Construction News 5 25 June pp. and 10 July 10 pp. Cornell, "Organization, Equipment and Methods: Building a Huge Irrigation and Power Project in Arizona," Contractors and Engineering Monthly (August pp. and "Stewart Mountain Development" in ? Stewart Mountain Dam {/ HAER No. AZ.-12 m: page 41 . . .

History of the Salt River Project for the Period October 1, through September 30, (no pages, in section on "Engineering and Major Construction"). 2 Hayden, "Salt River Project," (July 10, p. 3These buttresses that are designed to provide support for the ho;izonal thrust exerted by the dam's arch are referred to by a variety of names. Sometimes they are called "thrustblocks" and other times they are simply called "abutments" or. "buttresses". Regardles~ of the name used, the function of these two large masses of re~orce~ con- crete at either end of the dam has remained constant throughout the operational history of the structure.

4 Cragin, "Stewart Mountain Development," History of Salt River Project, 5"Needle valves" are devices which control the flow of water through a pipe (or penstock) through the horizontal movement of a cylindrical "plug" that is larg~ enough to completely close off the end of the pipe. The cylindrical plug has a sharp-pointed end which resembles a needle, hence the name "needle valve." For detailed discussion of the technology see Calvin Victor Davis, ed., Handbook of Applied Hydraulics (New York: McGraw-Hill Book Company, pp. 6The name "Francis turbine" refers to a type of inward flow rea~tion turbine ongma~y develoJ?ed by James B.

Francis, a century engineer who earned out many hydraulic expenments in his capacity as chief engineer in ch;a~ge of t~e Lowell, Massa~husetts, water power system. For more information descnbing the history and ope~atio~al character of various types of water turbines see Daniel W. Mead, Water Power Engmeenng: The Theory, Investigation and Development of Water Powers (New York: McGraw-Hill Book Company, pp. 'Specifications for the technical characteristics of the generator at Stewart Mountain Dam are taken directly from manufacturer's nameplate attached to the unit. 825-cycle AC current is better suited for the operation of large motors than it is for S):7Ste~ that include a large lighting load. 25-cycle current cause~ lig~ts to give off a flickenng eff~ct, a .Phenomenon that.

is negated by more rapidly ?scillating .60-~ycle C1;1I- rent. For discussion of the Salt ~ver Project's early interest m. converting its e~trre sys~em fro'f!l 25- 1~0 60-cycle operation, see Raymond Hill, "Econo~c .survey of Salt River Pr?Ject, Arizona, September pp. report included within, Volu~e ~6 of t~e Minutes of the Board of Governors of the Salt River Valley Water Users Associat10n. This report. was co~ssioned by the Board of Governors to help the Association plan its operations dunng and after World War IL For more on the ultimate changeover from 25- to 60-cycle equipment, see David M. Introcaso, "History of the Mormon Flat Dam," Chapter 5, HAER No. AZ.-14. Stewart Mountain's generators and transformers were changed to 60-cycle in (: Stewart Mountain Dam fj HAER No.

AZ-12 r: page 42 9Direct current exciters are considered to be necessary components of any major electric power station because it is unrealistic to attempt the operation of large-scale generating units using natural magnets. By using DC current to "excite" the electromag- nets in the main generators, it is possible to create a constant, reliable current in the conductor. 10See Mead, water Power Engi.neering, pp. for extended discussion of the relationship of governors to the operation of water turbines. Woodward governors, de- veloped by the Woodward Governor Company of Rockford, Illinois, are specifically described on pp.

11Engineers and utility executives are attracted to the use of higher voltage electric transmissions systems because higher voltages allow a reduction in the amount of copper wire necessary to carry a given amount of power. In general terms, the amount of power carried in a electric circuit is equal to the current times the voltage (power = current x voltage, or P = I x V). The amount of current in a circuit is directly proportional to the diameter of copper wire conductor required to carry the current. Thus, the amount of copper required in transmission circuit can be reduced by lowering the intensity of the current; the only way to do this without reducing the power is to raise the circuit's voltage.

12See Karen Smith, The Magnificent Experiment: Building the Salt River Reclamation Project, (Tucson: University of Arizona Press, pp. for more on Swilling's early activities. 13Comprehensive data on the population of Arizona and Maricopa County from through is provided in the Founeenth Census of the United States Population, Volume 1 (Washington, Department of Commerce, Government Printing Office, p. 94. 14John Wesley Powell, Repon on the Lands of the Arid Regi.on (Washington, Government Printing Office, For excellent discussion of Powell's Irrigation Survey, see Stanley Davison, The 15 Leadership of the Reclamation Movement, (New York: Arno Press, pp. For numerous bibliographic references to the "Irrigation Movement", see Lawrence B.

Lee, Reclaiming the American West: An Historiography and Guide (Santa Barbara, California: ABC-Clio Press, Extensive discussion of the background to the construction of Roosevelt Dam in 16 the Tonto Basin is provided in Donald C. Jackson, "History of the Roosevelt Dam," Chapter 2, HAER No. AZ-6. f: Stewart Mountain Dam f\ HAER No. AZ-12 i{ page 43 17The Hudson Reservoir and Canal Company's proposed dam design for the Tonto site is illustrated in the Thirteenth Annual Report of the U.S.

Geological Survey (Washing- ton, Government Printing Office, 18Plans for obtaining government permission for the issuance of county bonds to support construction of a dam at Tonto Basin are discussed in the Arizona Republican, 24 February and 8 March 19The "Articles of Incorporation of Salt River Valley Water Users' Association" were signed on February 4, They were published in the Second Annual Report of the Reclamation Service, (Washington, Government Printing Office, pp. 2 0'fhe Granite Reef Dam is located at a site not far from where the Salt River exits from the mountains to flow through the broad, fertile Salt River Valley. The dam is not designed to store water, but rather to provide. a means of diverting water into the main irrigation canals that serve farmers in the valley.

Construction of the Granite Reef Dam was undertaken by the Reclamation Service after the privately-owned Arizona Dam washed out in and water delivery to many farmers was seriously endangered. The Granite Reef Dam is described in the Fifth Annual Report of the Reclamation Service, p. 90.

21 Copies of the September 6, contract between the Department of the Interior and the Salt River Valley Water Users' Association can be found in the archives of the Salt River Project and in the Washington, National Archives, Record Group Entry 3, Box [Hereafter, reference to this collection will be NA, RG Entry 3, Box_ 22 September 6, contract, Paragraph #2, NA, RG Entry 3, Box 23 September 6, contract, Paragraph #3, NA, RG Entry 3, Box 24 September 6, contract, Paragraph NA, RG Entry 3, Box For discussion of the economic problems that plagued the Salt River Valley in the 25 early see David Introcaso, "History of the Mormon Flat Dam," Chapter 2, HAER No. AZ-14.

The history of the Salt River Valley Water Users' Association's repayments to the 26 federal government from through is provided in the publication, How Reclamation Pays: A Book of Project Repayment Histories and Payout Schedules with History of Crop Production (Washington, U.S. Department of the Interior, Government Printing Office, pp. This publication also includes references to all the "Public Notices and Contracts" that had an effect on how the repayment had been handled. :t Stewart Mountain Dam %: HAER No. AZ.-12 {{ page 44 27A description of how electric power would have to be generated as part of the construction process for building the Roosevelt Darn is included in Arthur P. Davis, 'Water Storage on Salt River, Arizona," (USGS Water Supply and Irrigation Paper No.

(Washington, Government Printing Office, This study was completed in and published the following year. 28A good discussion of water power is available in Mead, Water Power Engineering, pp. Mead notes that "the cubic feet per second flowing in a stream multiplied by the available head and divided by 8.8 will give the total available [theoretical] horse- power of the stream." 29A comprehensive history of traditional waterwheels is provided in Terry S. Reynolds, Stronger Than a Hundred Men: A History of the Vertical Waterwheel (Baltimore: The Johns Hopkins University Press, 30 See Mead, Water Power Engineering, p. 27, for a good discussion of how to assess the efficiency of a hydropower system.

The theoretically maximum amount of power that can be obtained from a flowing river is determined by the distance the water drops in a certain distance and the amount of the flow. However, the theoretical maximum can never be reached because of such factors as friction, water loss, etc .. 31 The interrelationship between magnetism and electricity was first discovered by Hans Christian Oersted of Denmark in At that time Oersted demonstrated that a wire carrying electric current is surrounded by a magnetic field. In the English scientist Michael Faraday determined that by moving a conductor through a magnetic field it was possible to induce a current in the conductor. Faraday's discovery comprises the basis of all later electric power generators.

For a succinct overview of early work in the study of electricity, see Bern Dibner's chapter on "Beginning of Electricity'' in Melvin Kranzberg and Carroll (ed.), Technology and Westem Civilization, Vol. 1 (New York: Oxford University Press, pp. 32The initial development of commercial electric power systems in the United States is described in Thomas P. Hughes, Networks of Power: Electrification in Westem Society, (Baltimore: The Johns Hopkins University Press, pp. 33Early California hydroelectric power systems are described in Hughes, Network of Power, pp. and in Donald C. Jackson, "A History of Water in the American West: John S. Eastwood and 'The Ultimate Darn' dissertation, University of Pennsylvania, pp.

34The use of three-phase AC current becomes important because a single-phase of AC current is not easily employed for the transmission of electricity for power purposes (as opposed to lighting purposes). By building transmission systems with more than one circuit (i.e., polyphase circuits), it becomes possible to transmit power over an AC system. tt Stewart Mountain Dam tr HAER No. A'l,-12 :? page 45 For more on this, see Jackson, "The Ultimate Darn," p. The advantage of AC over DC systems was that DC systems could not transmit electricity for power and lighting purpose for more than about 10 miles. For discussion of why three-phase AC systems were more economical than two-phase AC systems, see Jackson, "The Ultimate Darn," pp.

and Louis Bell, "The Saving of Copper in the Three Wire, Three Phase System," Electric World 23 (27 January p. The 83-rnile long Santa Anna-to-Los Angles transmission line is described in 35 George Low, "The Generating, Transmission and Distribution Systems of the Edison Electric Company of Los Angles," Journal of Electricity, Power and Gas 13 (January The Bay Counties Power Company's 140-mile long transmission line is described 36 in George Low, "The World's Longest Electric Power Transmission," Journal of Electricity, Power and Gas 11 (July 37A complete history of the facility can be found in David Introcaso's "History of the Roosevelt Power Canal," HAER No. AZ,-4. Data on the history of the Roosevelt Power Plant can be found in Donald C.

38 Jackson, "History of the Roosevelt Darn," HAER No. AZ,-6. 39A detailed description of the early Salt River Project power system is provided in James M. Gaylord, "Power and Pumping System of the Salt River Project, Arizona," 1 Jan- uary National Archives (Denver), RG Bureau of Reclamation, Engineering and Research Center Files, Box 40 Extensive documentation on the origins of the power contract between the Reclamation Service and the Pacific Gas and Electric Company can be found in NA, RG Entry 3, Box 41 The early history of the Water Users' Association's hydroelectric power system is discussed in Chapter 2 of David Introcaso's "History of the Mormon Flat Darn," HAER No. A'l,-14. Biographical data on Charles C.

Cragin is provided in Chapter 2 of Introcaso, 42 "History of the Mormon Flat Darn" and in History of the Salt River Project for the Period October 1, to September 30, p. 11; Frank Reid's obituary appears in The Phoenix Gazette, 8 October The collapse of agricultural prices in the Salt River Valley during the early 43 is discussed in Introcaso, "History of the Mormon Flat Darn." Because the Mormon Flat Darn was the first of the large hydroelectric power darns built by the Water Users' Associ- ation in the it is appropriate that most of the data on the economic conditions in the Salt River Valley during this period be included in the HAER report on the Mormon Flat Darn. :t Stewart Mountain Dam HAER No. AZ-12 f:!

page 46 ' ' ' 44A copy of Cragin, O'Hara and Lawson's "Report on Proposed Additional Hydro- electric Power Development of the Salt River," completed in February can be located in the Salt River Project Research Archives, Tempe, Arizona. A copy can also be found in the National Archives, Denver Branch, Bureau of Reclamation, Record Group Engineering and Research Center Files Box [This source will sub- sequently be referenced as NA, Denver, RG Engineering and Research.] 45The only facet of a water storage system in which irrigation and hydroelectric power generation are readily compatible is in the operation of groundwater irrigation pumps. 46A good general engineering description of the Mormon Flat Darn is given in T.A.

Hayden, "Salt River Project, Arizona: Irrigation and Hydroelectric Power Development by Salt River Valley Water Users' Association - Six Major Darns," Western Construction News 5 (25 June pp. In basic terms, Cragin was attempting to increase the "load factor" of the Water 47 Users' Association's system. "Load factor" is a term that relates to the overall efficiency of an electric power system. The load factor is the ratio of the average power usage of a system to the maximum load on the system. The closer the average load is to the peak load, the higher the load factor. Higher load factors mean that a system is being used with more economic efficiency because the investment required to serve the peak load is generating greater overall revenues.

48In the Cragin report there was also mention of a plan to build a smaller version of the Horse Mesa Darn (the original Mormon Flat Power Darn) and supplement it with yet another darn called Pine Creek that would have been built between Roosevelt Darn arid Horse Mesa. The Pine Creek proposal was never pursued. Cragin's report on hydroelectricity made only the briefest reference to plans 49 for a power plant development at the Stewart Mountain site; these plans were not for a storage darn but for a lengthy power canal. SO'fhe three-quarters majority consent of Association members for the assumption of any major debt obligations is provided for in the original Association bylaws.

The approval of the bonds to finance the Mormon Flat Darn is described in 51 Introcaso, "History of the Mormon Flat Darn," HAER No. AZ-14, Chapter 3. The bonds were approved by a vote of to 52Quote taken from communication by Jarvis included as part of William Kelleys' "Coordination of Irrigation and Power," Transactions of the American Society of Civil Engi.neers 89 p. This article focused on the difficulties of operating water supply system to serve both power and agricultural needs. \} Stewart Mountain Dam if HAER No.

AZ-12 I_{ page 47 , , 53 Cragin to President and Board of Governors of the Salt River Valley Water Users' Association, 8 February letter retained in Salt River Project Research Archives [hereafter referred to as SRPRA], Box 54A complete copy of the contract between the Salt River Valley Water Users' Association and the Central Arizona Light and Power Company is retained in the Minutes of the Board of Governors [hereafter referred to as BOG Minutes], 8 February Vol. 11, p. 55 BOG Minutes, 8 February Vol. 11, p. 56"Salt River Valley Water Users' Association, Statement of Facts," circa 1 April p. 1. This is a 16-page informational pamphlet printed to explain the advantages of the Stewart Mountain development. A copy of the pamphlet is in the private collection of Richard Tempe, Arizona.

57A description of the exact agreement among members of the Water Users' Association to subsidize those members forced to pay higher rates to CALAPCO is provided in BOG Minutes, 8 February Vol. 11, p. 58This condition was explicitly noted in the September 6, agreement between the Water Users' Association and the federal government. 59Elwood Mead to Secretary of the Interior [approved by E.C. Finney, First Assistant Secretary], 1 February copy included in BOG Minutes, 8 February Volume 11, pp. Complete transcripts of all six propositions appear in BOG Minutes, 8 February 60 Vol. 11, pp. . . 61 The complete results of the March special election are listed BOG Minutes, 26 March Vol. 11, p. 62 BOG Minutes, 26 March Vol. 11, p. 63BOG Minutes, 26 March Vol. 11, pp.

For more on the debate over whether the Stewart Mountain bonds should be approved_ see: "Stewart Mountain Development and Valley Electrification Now Up to Vote of Farmers," Associated Arizona Producer 7 (15 March p. 3; "Do You Want Electricity in Your Home?" The Associ- ated Arizona Producer 7 (15 March p. 11; "The Other Side of the Stewart Moun- tain Question, What Opponents Advocate," The Associated Arizona Producer 7 (l May p. 1; "Facts About the Salt River Project Power System and Stewart Mountain Development," The Associated Arizona Producer 7 (1 May pp. 2 and 5; "Stewart Mountain Development and Valley Electrification," The Associated Arizona Producer 7 (15 May p. 1; "The Stewart Mountain Power Development," The Associated Arizona \@ Stewart Mountain Dam fl HAER No.

AZ-12 Ji page 48 ' ' ' Producer 7 (15 September p. 4; "Contract for Sale of Stewart Mountain Devel- opment Bonds," The Associated Arizona Producer 7 (15 September p. 5. "Salt River Valley Water Users' Association, Statement of Facts," circa 1 April 64 See endnote 56 .. 65George L. Johnson to President and Board of Governors of the Salt River Users Association, April 28, letter appears in BOG Minutes, 30 April Vol 11, p. 66The complete results of the May 8th special election are listed in BOG Minutes, 14 May Vol. p. See BOG Minutes, 16 May Vol. 12, pp. for complete data on how 67 the Water Users' Association solicited financing from private investment groups. 68'fhe bond contract signed with the syndicate headed by the Detroit Trust Company is provided in full in BOG Minutes, 28 May Vol.

12, pp. 69A succinct overview and commentary on the legal action taken to halt work on Stewart Mountain development is provided by a memo written by Cragin that is included in BOG Minutes, 15 September Vol. 12, pp. 70 BOG Minutes, 15 September Vol. 12, p. 71 BOG Minutes , 15 September Vol. 12, p. 72 BOG Minutes, 15 September Vol. 12, p. 73The $5 million estimated as lost by Cragin came from the lower sale price of the bonds per instead of per and the higher interest rate in- stead of The problem encountered by the Water Users' Association is analogous to a prospective home buyer who arranges for financing at an interest rate of 10% and is given 90 days to close the sale.

If the sale is not concluded in the required 90 days then the buyer needs to arrange financing again starting from scratch. If, for example, interest rates subsequently rise to 11 % then the buyer will be forced to pay more for the loan then if they had been able to close the deal within the original 90 day financing period. In basic terms, the Water Users' Association was a "buyer" who failed to meet the time requirements of their original loan agreement; when they sought new loan fi- nancing they were forced to pay a higher interest rate. 74 Cragin, "Development of Hydroelectric Power as an Aid to Irrigation," Transactions of the American Society of Civil Engineers 98 pp. it Stewart Mountain Dam i!f HAER No. AZ-12 :!{ page 49 . . . 75See Donald C.

Jackson, "History of the Roosevelt Dam," HAER No. AZ-6, for dis- cussion of the differences between the massive tradition of dam design exemplified by gravity dams and the structural traditions of arch dams. 76See Jackson, "History of Roosevelt Dam," HAER No. AZ-6, for discussion on how the costs of this dam greatly exceeded initial estimates and ultimately placed a great financial burden on the Water Users' Association because they were required to repay the cost of the dam. 77'fhe designs of the two earlier dams are described in David Introcaso, "History of the Mormon Flat Dam," HAER No. AZ-14; and David Introcaso, "History of Horse Mesa Dam," HAER No. AZ-14. Unless otherwise referenced, material on the design of these two dams is drawn from these sources.

78 For more on the early history of the arch dam, see Donald C. Jackson, "A History of Water in the American West: John S. Eastwood and "The Ultimate Dam,"' dissertation, University of Pennsylvania, Chapter Two; Jan A. Veltrop, "Concrete Arch Dams," in Kollgaard and Chadwick's Development of Dam Engineering in the United States, (New York: Pergamon Press, also see, James D. Schuyler, Reservoirs for Irrigation, Water Power and Domestic Water Supply, Second Edition (New York: John Wiley and Sons, and Edward Wegmann, Design and Construction of Dams, Eighth Edition (New York: John Wiley and Sons, 79Jorgensen's patent on his "Constant Angle Arch Dam," is No.

and was assigned in His method of design is described in Lars Jorgensen, "The Constant- Angle Arch Dam," Transactions of the American Society of Civil Engineers 78 pp. and Lars Jorgensen, "The Constant Angle Arch Dam," Journal of Electricity 38 (15 January pp. SO'fhe dispute between the Water Users' Association and Jorgensen's Constant Arch Dam Company is documented in Box No. in the Salt River Project Research Ar- chives. The most revealing of the letters in this file are Karl Brehme (President of the Constant Angle Arch Dam Company) to Cragin, 27 March Karl Brehme to Salt River Valley Water Users' Association, 10 January Cragin to Constant Angle Arch Dam Company, 19 March and Cragin to Gene B.

Heywood, 17 April This latter letter indicates that Cragin believed, 'We were confident we could win the case, but I am satisfied the above settlement [of is the best for us in that it would cost us at least that much to win the case and no telling what might happen." A precedent for Jorgensen's patent that should have invalidated it is described in John Eastwood, "An Arch Dam for the Site of the Shoshone Dam," Engineering News 63, (9 June pp. it Stewart Mountain Dam it HAER No. AZ-12 i:} page 50 81 In the early a number of technical articles were published that explored the difficulties of using mathematical analysis to determine the stresses within arch darns.

Among the most important of these articles are: Lars Jorgensen, "Improving Arch Action in Arch Darns," Transactions of the American Society of Civil Engineers 83 pp. Fred Noetzli, "Gravity and Arch Action in Curved Darns," Transactions of the American Society of Civil Engineers 84 pp. William Cain, "The Circular Arch Under Normal Loads," Transactions of the American Society of Civil Engineers 85 pp. and Fred Noetzli, "The Relation Between Deflections and Stresses in Arch Darns," Transactions of the American Society of Civil Engineers 85 pp.

82The earliest analysis of arch darns that attempted to reconcile the gravity and arch actions that operate within the structures are: Herbert Vischer and Luther Wagonner, "On the Strains in Curved Masonry Darns," Transactions of the Technical Society of the Pacific Coast 6 (December pp. and Charles L. Harrison and Silas Woodward, "Lake Cheeseman Darn and Reservoir," Transactions of the American Society of Civil Engineers 5 pp. Howell and A.C. Jaquith, "Analysis of Arch Darns by the Trial Load Method," 83 Transactions of the American Society of Civil Engineers 93 pp. 84 Cragin makes brief mention of a plan to build a multiple-arch darn at the Stewart Mountain site in "Engineering and Major Construction," Annual History of the Salt River Project from January 1, to December 31, p. 2.

In this description Cragin states that "a multiple arch was first considered for this site. Final explorations with diamond drills, however, developed a maximum depth of ninety feet to lowest bedrock from the strearnbed. Plans were accordingly changed and the darn designed as a central arch sec- tion thrusting against massive reinforced concrete abutments." No plans or descriptions of the proposed multiple-arch design for Stewart Mountain have been discovered. The Bureau of Reclamation's design review and modification of the Stewart 85 Mountain Darn design is documented in file No. B-A 7.5 in the Salt River Project Research Archives.

This file includes an important memo by Lewis dated 12 July that provides a review of the approval process from the original design submittal in February through final approval in July Walters, Chief Engineer of the Bureau of Reclamation requested in March that the abutments by widened by two feet and that three-tenths of one percent of the volume of the buttresses be comprised of steel reinforcement to help resist shrinkage cracks. Walters also demanded that the upstream "overhang" be eliminated by adding more concrete to the arch. The Bureau's approval of the design is verified in a memo by Lewis dated 11 February (: Stewart Mountain Dam {{ HAER No.

AZ-12 :f page 51 86The Bureau of Reclamation's approval of the Stewart Mountain Dam's foundations is acknowledged in Savage [Chief Designing Engineer of the Bureau] to Cragin, 31 October [Letter included in BOG Minutes, 4 November Vol. 13, pp. 87 In Connell, "Organization, Equipment and Methods: Building a Hugh Irrigation and Power Project in Arizona," Contractors and Engineers Monthly (August pp. it was reported that, "all work [on the Stewart Mountain Dam] was done by forces on the Salt River Valley Water Users' Association, practically the same personnel and much of the same equipment being employed as on the Horse Mesa and Stewart Mountain construction, as a result of the existence of this organization and equipment...

contract work was not considered and it is estimated that a savings of 25% was saved over contract prices." The contract with General Electric for elec- trical equipment is noted in BOG Minutes, 7 March Vol. 12, pp. [Connell's article quoted above will hereafter be referenced as "Organization, Equipment and Methods".] 88 For discussion of the construction of Roosevelt Dam see Donald C. Jackson, "History of the Roosevelt Dam," HAER No. AZ-6. 89 Cragin, "Engineering and Major Construction: Stewart Mountain Develop- ment," p. 3, in Annual History of the Salt River Project, [hereafter this source will be referenced as "Stewart Mountain Development."] Preliminary road work is described in Cragin, "Stewart Mountain Development," 90 p. 3; and in T.A.

Hayden, "Salt River Project, Arizona - Stewart Mountain Dam," Western Const1Uction News 5 (10 July p. [hereafter this latter source will be referenced as "Stewart Mountain Dam."] 91 Hayden, "Stewart Mountain Dam," p. 92Discussed in both Cragin, "Stewart Mountain Development," p. 3 and Hayden, "Stewart Mountain Dam," pp. the Horse Mesa Dam site was particularly con- stricted and posed serious problems in the location of a construction camp. 93 Connell, "Organization, Equipment and Methods," p. 58. 94 Connell, "Organization, Equipment and Methods," p. 58. 95 Hayden, "Stewart Mountain Dam," p. Unfortunately, no records of the construction camps' population survives in the 96 Salt River Project Research Archives. ff Stewart Mountain Dam )jj HAER No. AZ-12 :.r page 52 . .

97 Hayden, "Stewart Mountain Dam," p. 98 Connell, "Organization, Equipment and Methods," p. 58. 99'fhere was also a need to remove the water that accumulated in the foundations as a result of the hydraulic cleaning of the bedrock. 100'fhe piles for the cofferdam were driven by a McKieman-Terry No. 7 reversible double acting pneumatic hammer delivering 225 strokes per minute. 101 Connell, "Organization, Equipment and Methods," p. 59. 102 Hayden, "Stewart Mountain Dam," p. 103 Connell, "Organization, Equipment and Methods," p. 57. 104 Cragin, "Stewart Mountain Development," p. 6. 105Excavation work is described in Cragin, "Stewart Mountain Development," p. 7; the starting date for excavation in given in "Stewart Mountain Project, Phoenix, Arizona," Western Construction News 4 (25 February p.

Basic chronological data on construction is taken from Cragin, "Stewart Mountain 106 Development," p. 6; and Hayden, "Stewart Mountain Dam," p. The date of the dam's completion is given in connell, "Organization, Equipment and Methods," p. 56. It was not unusual to have the abutments of concrete arch dam poured first to 107 insure they formed a solid anchorage for the rest of the structure. 108 Hayden, "Stewart Mountain Dam," p. Hayden, "Stewart Mountain Dam," p. See the conclusion of this report for 109 more on later grouting work. 11 Connell, "Organization, Equipment and Methods," p. 59. 111 Cragin, "Stewart Mountain Development," p. 1; and Connell, "Organization, Equipment and Methods," p. 56. 112 Hayden, "Stewart Mountain Dam," p. 113 Hayden, "Stewart Mountain Dam," p.

it Stewart Mountain Dam ({ HAER No. AZ-12 if page 53 . . . 114No data on the exact sizes of the gravel and rock used in the Stewart Mountain Dam has been located. The sizes here are estimated from standard practice of the period. Because the concrete needed to be chuted for several hundred feet, it was imperative that all the aggregates be fairly small in order to prevent "clogging" of the chutes. The sizes of the aggregate bins are provided in Hayden, "Stewart Mountain 115 Dam," p. 116 Hayden, "Stewart Mountain Dam," p. 117 Hayden, "Stewart Mountain Dam," p.

118The concrete equipment marketed by the Insley Manufacturing company is fully described in a 96-page catalogue published in entitled, "Insley Concrete Placing Equipment: The Insley Steel Tower, Quick Shift, Counterweight Chute Plant, The Insley Mast Hoist Plan." Copy of the catalogue is available in the personal library of Donald Jackson, Easton, Pennsylvania. 119 Descriptions are taken from Connell, "Organization, Equipment and Methods," p. 59. 120 Connell, "Organization, Equipment and Methods," p. 59. 121 Hayden, "Stewart Mountain Dam," p. 122 Connell, "Organization, Equipment and Methods," p. 55. 123 Hayden, "Stewart Mountain Dam," p. 124 Connell, "Organization, Equipment and Methods," p. 5 7.

See History of the Salt River Project for the Period October 1, to September 125 30, "Annual Report of General Superintendent and Chief Engineer," pp. (Chapter One) and pp. 2-6 (Chapter Two). The electrification program is described in History of the Salt River Project for 126 the Period October 1, to September 30, "Annual Report of the Superintendent and Chief Engineer," pp. (Chapter One); and in History of the Salt River Project for the Period October 1, to September 30, "Annual Report of the General Superin- tendent and Chief Engineer," pp. (Chapter One). :t Stewart Mountain Dam it HAER No. AZ-12 fj page 54 127History of the Salt River Project for the Period October 1, to September 30, "Annual Report of General Superintendent and Chief Engineer," p.

7 (Chapter One) and "Power and Pumping Diversion," pp. 2 and 13 (Chapter Six). As David Introcaso notes in his "History of Mormon Flat Dam," HAER No. AZ- 128 14, the complete history of the Water Users' Association financial condition is documented in Barry Dibble, "Engineering and Economic Examination of Salt River Valley Water Users' Association, Salt River Project," January A copy is available in the Salt River Project Research Archives. See report by Raymond Hiss entitled "Economic Survey of Salt River Project, 129 Arizona," September included in the Minutes of Board of Governors, Vol. 26, for more on the Association's electric power system during World War II. See Dibble, "Engineering and Economic Examination," January report 130 available in SRPRA.

131 The change from 25-cycle to 60-cycle power is described in Morong, E.J. Lauerrman and J.A. Hollowell, "The Salt River Project's Hydro Expansion and Fre- quency Unification Program," a paper presented to the Institute of Electrical and Elec- tronic engineers, 18 April copy available in the Salt River Project Research Archives. 132The idea of constructing a concrete spillway apron is first proposed in William Cone, "Report on Inspection of Horse Mesa, Mormon Flat and Stewart Mountain Develop- ments," 21 July copy available in the Salt River Project Research Archives.

The spillway work undertaken at Stewart Mountain is described in Mcconaughy and Lieurance, "Report on Stewart Mountain Dam, Mormon Flat Dam, Horse Mesa Dam and Roosevelt Dam, Salt River Project, Arizona," 1 February and "Stewart Mountain Dam Spillway, Salt River Project, Arizona," (n.a.) 10 July both of these latter articles are available in NA Denver, RG Engineering and Research, Box See "Contract Between the United States of America and the Salt River Valley 133 Water Users' Association Providing for the Construction of Bartlett Dam and Repairs to and Completion of Other Dams and Project Canals," 26 November copy available in the Salt River Project Research Archives. See History of the Salt River Project for the Period January 1, to December 134 31, for more on the spillway addition.

The hydraulic characteristics of the new spillway were described in Bureau of Reclamation research and, Geology Division, draulic Model Studies for Spillway Channel and Stewart Mountain Dam, Salt River Pro- ject, Arizona," 13 September copy in NA Denver, RG Engineering and Research, Box The spillway work also included the installation of new electric motors to operate the Tainter gates. fi Stewart Mountain Dam {[! HAER No. AZ-12 ii page 55 135A good basic reference on alkali-aggregate reactions, as they were understood in the is Blanks and Meissner, "Deterioration of Concrete Dams Due to Alkali-Aggregate Reaction," Transactions of the American Society of Civil Engi.neers 111 pp. This article also provides an excellent bibliography.

136 Unless otherwise noted, data on the condition of the dam in regard to the effects of alkali-aggregate reaction is taken from material in File No. B-A7, within the Salt River Project Research Archives. This file contains several unattributed reports dating from the early through the late 137See O.E. Boggess, "Grouting contraction Joints and Drilling 24-inch Calyx Hole, Stewart Mountain Dam, Salt River Project, Arizona," 15 April copy in NA Denver, RG Engineering and Research, Box This study was undertaken upon the recom- mendation of a committee consisting of Joel Justin, Herbert Crocker, Ivan Houk, Raymond Davis and Byrum Steel.

138"Petrographic Examination of 22-inch Diameter Concrete Cores from Stewart Mountain Dam, Salt River Project, Arizona," (circa copy in NA Denver, RG Engineering and Research, Box Because of losses in the drilling process, the 24- inch diameter holes referred to in endnote 140 produced the 22-inch diameter concrete cores referred to above. 1390.E. Boggess, "Grouting Contraction Joints," 15 April pp. In 550 pounds of asphalt had also been poured into the contraction joints as a stopgap measure to reduce seepage. 1" See O.E. Boggess, "Pressure Grouting Construction Joints; Stewart Mountain Darn, Salt River Project, Arizona," February copy available in NA Denver, RG Engineering and Research, Box Also see "Grouting Stops Arizona Darn Leakage," Engi.neering News-Record 150 (30 April p. 27.

See File No. B-AZ.5 for more on these alterations to the Stewart 141 Mountain Dam in the late and :J Stewart Mountain Dam :J HAER No. AZ-12 :t page 56 Bibliography MANUSCRIPT COLLECITONS AND PRIMARY

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Engineering and Research Center Project Reports Bureau of Reclamation, Record Group Denver Branch, National Archives, Denver, CO. General Administrative and Project Records, and Salt River Project, Bureau of Reclamation, Record Group National Archives, Washington, Salt River Valley Water Users' Association, Minutes of the Meetings of the Board of Governors, Phoenix, Arizona. BOOKS, DISSERTATIONS AND THESES Blanks, R.F ., and Meissner "Deterioration of Concrete Dams Due to Alkali-Aggregate Reaction." Transactions of the American Society of Civil Engineers III Creager, William, Joel Justin and Julian Hinds, Engineering for Dams, Volume III. New York: John Wiley and Sons, Davis, Arthur Powell. Irrigation near Phoenix, Arizona. U.S. Geological Survey Paper No. 2.

Washington, Government Printing Office, Davis, Calvin Victor, editor. Handbook of Applied Hydraulics. New York: McGraw-Hill, Davison, Stanley. The Leadership of the Reclamation Movement. New York: Arno Press, Fifth Annual Report of The Reclamation Service, Washington, Government Printing Office, ti Stewart Mountain Dam li HAER No AZ-12 fi page 57 Fourteenth Census of the United States Population, Volume I. Washington, Department of Commerce, Government Printing Office, How Reclamation Pays: A Book of Project Repaymellt Histories and Payout Schedules with History of Crop Production. Washington, U.S. Department of the Interior, Government Printing Office, Hughes, Thomas P.

Networks of Power: Electrification in Western Society, Baltimore: The Johns Hopkins University Press, Introcaso, David M. "History of the Roosevelt Power Canal." File No. AZ-4, Historic American Engineering Record, Prints and Photographs Division, Library of Congress, Washington, Introcaso, David M. "History of the Mormon Flat Darn." File No. AZ-14, Historic Ameri- can Engineering Record, Prints and Photographs Division, Library of Congress, Washington, Jackson, Donald C. "History of Roosevelt Darn," File No. A'l-6, Historic American Engin- eering Record, Prints and Photographs Division, Library of Congress, Washington, Jackson, Donald C. "A History of Water in the American West: John S.

Eastwood and 'The Ultimate Darn' Dissertations, University of Pennsylvania, Kranzberg, Melvin, and Pursell, Carroll, editors. Technology and Western Civilization, Vol. I. New York: Oxford University Press, Mawn, Geoffrey P. "Phoenix, Arizona: Central City of the Southwest Dissertation, Arizona State University, Medad, Daniel. Water Power Engi.neering: The Theory, Investigation and Development of Water Powers. New York: McGraw-Hill, Powell, John Wesley. Report on the Lands of the Arid Regi.on. Washington, Govern- ment Printing Office, Reynolds, Terry S. Stronger Than a Hundred Men: A History of the Vertical Waterwheel. Baltimore: The Johns Hopkins University Press, Schuyler, James D. Reservoirs for Irrigation, Water Power and Domestic Water Supply, Second Edition.

New York: John Wiley and Sons, ft Stewart Mountain Dam }f HAER No. AZ-12 fi page 58 Second Annual Report of the Reclamation Se,vice, Washington, Government Printing Office, 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: Citidel Press, Veltropp, Jan A. "Concrete Arch Dams," in Kollgaard, Eric B., and Chadwick, Wallace L. Development of Dam Engineering in the United States. New York : Pergamon Press, Wegmann, Edward. Design and Constntction of Dams, Third Edition. New York: John Wiley and Sons, Zarbin, Earl A.

Roosevelt Dam: A History to Phoenix: Salt River Project,

Articles and Reports

Bell, Louis. ''The Savings of Copper in the Three Wire, Three Phase System." Electrical World 23 (27 January p. Cain, William. "The Circular Arch under Normal Loads." Transactions of the American So- ciety of Civil Engineers BS Cornell, "Organization, Equipment and Methods: Building a Huge Irrigation and Engineering Project in Arizona." Contractors and Engineering Monthly (August pp. Cragin, "Development of Hydroelectric Power as an Aid to Irrigation." Transactions of the American Society of Civil Engineers 98 "Do You Want Electricity in Your Home." Associated Arizona Producer 7 (15 March p. 11. Eastwood, John S. "An Arch Dam for the Site of the Shoshone Dam." Engineering News 63 (9 June pp. ft Stewart Mountain Dam :] HAER No. AZ-12 i.t page 59 . .

"Facts About the Salt River Project Power System and Stewart Mountain Development." Associated Arizona Producer 7 (1 May "Grouting Stops Arizona Dam Leakage." Engineering-News Record 150 (30 April p. 27. Harrison, Charles L., and Woodward, Silas. "Lake Cheeseman Dam and Reservoir." Transactions of the American Society of Civil Engineers 5 Hayden, T .A. "Salt River Project, Arizona: Irrigation and Hydroelectric Development by Salt River Valley Water User's Association - Six Major Dams." Western Construction News 5 (25 June, 10 July pp. Hill, Raymond. "Economic Survey of Salt River Project, Arizona, September Type- written manuscript. Minutes of the Board of Governors Meetings, Salt River Valley Water Users' Association, Phoenix, AZ.

"History of the Salt River Project for the Period October 1, to September 31, Typewritten report, Salt River Project Archives, Phoenix, AZ.. "History of the Salt River Project for the Period October 1, to September 30, Typewritten report, Salt River Project Archives, Phoenix, AZ.. "History of the Salt River Project for the Period October 1, to September 30, Typewritten report, Salt River Project Archives, Phoenix, AZ.. Howell, and Jaquith, A.C. "Analysis of Arch Dams by the Trail Load Method." Transactions of the American Society of Civil Engineers 93 Jorgensen, Lars. "The Constant Angle Arch Dam." Journal of Electricity 38, (15 January pp. Jorgensen, Lars. "The Constant Angle Arch Dam." Transactions of the American Society of Civil Engineers 78 Jorgensen, Lars.

"Improving Arch Action in Arch Dams." Transaction of the American Society of Civil Engineers 83 Jorgensen, Lars. "The Record of 100 Dam Failures." Journal of Electricity 44 (15 March and 1 April pp. Kelley, William. "Coordination of Irrigation and Power." Transactions of the American Society of Civil Engineers 89 II Stewart Mountain Dam fi HAER No. Al.-12 ]f page 60 Low, George. "The Generating, Transmission and Distribution Systems of the Edison Electric Company of Los Angeles." Journal of Electricity Power and Gas 13 (January Low, George. "The World's Longest Electric Power Transmission." Journal of Electricity, Power and Gas 11 (July "The Other Side of the Stewart Mountain Question, What Opponents Advocate." Associated Arizona Producer 7 (l May p. 1. Morong, E. J. Lauerrman and J.A.

Hollowell, "The Salt River Project's Hydroexpan- sion and Frequency Unification Program." Typewritten report, Salt River Project Archives, Phoenix, Arizona. Noetzli, Fred. "Gravity and Arch Action in Curved Dams." Transactions of the American Society of Civil Engineers 84 Noetzli, Fred. "The Relation Between Deflections and Stresses in Arch Dams." Transac- tions of the American Society of Civil Engineers. Sloan, Richard. "Land and Water Rights, Salt River Project." Typewritten manuscript, Salt River Project Archives, Phoenix, Arizona. ''The Stewart Mountain Development." Associated Arizona Producer 7 (15 September p. 4. "Stewart Mountain Development and Valley Electrification Now Up to Vote of Farmers." Associated Arizona Producer 7 (15 March p. 3.

"Stewart Mountain Project, Phoenix, Arizona." Western Construction News 4 (25 February p. Vischer, Herbert, and Wagonner, Luther. "On the Stains in Curved Masonry Dams." Transactions of the Technical Society of the Pacific Coast 6 (December STEWART MOUNTAIN DAM HAER AZ-12 Spanning the Salt River HAER AZ-12 Tempe Maricopa County Arizona PHOTOGRAPHS WRITTEN HISTORICAL AND DESCRIPTIVE DATA FIELD RECORDS HISTORIC AMERICAN ENGINEERING RECORD National Park Service U.S. Department of the Interior C Street NW Washington, DC