Gateways to Commerce:
The U.S. Army Corps of Engineers' 9-Foot Channel Project on the Upper Mississippi River
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Case Study: The Construction of Lock and Dam No. 26

The U.S. Army Corps of Engineers built 29 lock and dam complexes on the Upper Mississippi River. The construction of those complexes, and the decisions related to that process, greatly influenced the pace of technological development of the Upper Mississippi River 9-Foot Channel Project. Poor or misguided construction decisions invited disaster. Well-planned and well-executed construction efforts generated technical innovations and improvements at later sites. On the following pages is a detailed description of the construction of Lock and Dam No. 26, located near Alton, Illinois.

Lock and Dam No. 26 was located immediately upstream from two railroad and highway bridges. As a result, Corps engineers incorporated the bridges' piers into the design of the lock walls. Lock and Dam No. 26 Site Map, December 1934. (U.S. Army Corps of Engineers, St. Louis District)

Lock and Dam No. 26 is being highlighted for several reasons. Lock and Dam No. 26 provides an excellent opportunity to examine the decision-making and construction methods, both efficient and inefficient, involved in the building of the 9-foot channel. The complex was also a somewhat "typical" 9-foot channel installation. The Corps of Engineers constructed Lock and Dam No. 26 between 1934 and 1938, during the middle phase of the Upper Mississippi River 9-Foot Channel Project. Many of the technological breakthroughs associated with the 9-Foot Channel Project were standard practice by the time work began on Lock and Dam No. 26.

The Upper Mississippi Valley Division designed the twin locks at installation No. 26 prior to the assignment of design responsibilities to individual districts at the close of 1933. As such, the lock design reflects the level of technology immediately following the earliest phases of the project. The Corps designed Dam No. 26 in 1934 and constructed it between 1935 and 1938. Corps engineers equipped the dam with thirty 40-foot-long, submersible, Tainter gates. The rapid evolution of Tainter gate design is perhaps the most significant technological achievement of the 9-Foot Channel Project. As one chapter of a larger story, the building of Lock and Dam No. 26 sheds light on the methods used to construct the 9-foot channel, and the wide range of technical innovations and improvements realized throughout the course of the project.

Lock and Dam No. 26 was also unique because it was the first Upper Mississippi River 9-Foot Channel Project complex replaced by a modern structure. The construction of the 9-foot channel on the Upper Mississippi had vastly increased the amount of barge traffic on the river. The tonnage passing through Lock and Dam No. 26, the southernmost lock and dam complex constructed during the 1930s, increased from 1.4 million tons per year in 1938, to 55 million tons in 1975. This enormous increase in traffic severely taxed the operational capacity of the installation and ultimately led, with a variety of other factors, to the construction of a new facility. The Corps of Engineers removed the original installation in 1990, and completed the construction of Lock and Dam No. 26R, also known as the Melvin Price Lock and Dam, in 1991. In Lock and Dam No. 26R, the Corps of Engineers incorporates the most modern design lessons and philosophies, representing the culmination, for the moment, of Mississippi River navigation improvement technology. [1]

Authorization and Site Selection

The U.S. Army Corps of Engineers located Lock and Dam No. 26 approximately 23 miles above St. Louis, placing it under the jurisdiction of the St. Louis District office. Because the authors of House Document 137 realized that the 1930 authorizing act had not appropriated enough money to complete the 9-Foot Channel Project, they developed a plan for progressively building the channel as funds became available. Under the plan, Corps officials placed each lock and dam complex in one of four groups: A, B, C, or D. Because they were necessary for existing commerce, Group A structures were slated for immediate construction. Group B structures, which were located in areas that did not have a dependable 6-foot channel, were the next priority. Although ultimately needed to secure a 9-foot channel, Group C and D structures were the lowest priority. All of the 9-foot channel installations in the St. Louis District, including No. 26, were "Group D" structures because dredging alone could maintain a 9-foot channel in this stretch of the Upper Mississippi River. Of these, Lock and Dam No. 26 was the first to be built. [2]

The Corps' special Board of Engineers originally recommended that Lock and Dam No. 26 be located just below Grafton, Illinois, approximately 1 mile below the mouth of the Illinois River. By September 1933, however, Corps officials relocated the site to Alton, Illinois, approximately 20 miles below the point where the Illinois River joins with the Upper Mississippi. Corps engineers determined that the navigation pool formed by Dam No. 26 would create backwater 80 miles up the Illinois River. As a result, Lock and Dam No. 26 would facilitate barge traffic on both the Mississippi and the Illinois Rivers, making it a key element within a complex inland navigation system that ultimately extended from New Orleans to Pittsburgh, Chicago, Kansas City, and Omaha. Corps engineers often relocated lock and dam sites throughout the 9-Foot Channel Project. The recommendations of the special Board of Engineers' survey report were frequently discarded upon closer investigation of the lock and dam sites. [3]

Lock and Dam No. 26, October 1938. (U.S. Army Corps of Engineers, St. Louis District)

In the case of Lock and Dam No. 26, the relocation appears to have been for more than just engineering reasons. Forty years after the fact, Tom Butler, the mayor of Alton, claimed the Corps moved the installation to Alton because Grafton did not have enough open space for an adequate storage and staging yard. According to Butler, Corps officials proposed to relocate the lock and dam installation to Alton, where the recently constructed Riverside Park offered an excellent site for a construction yard, if Alton would allow the Government to use the park site free of charge for the duration of the project. Faced with large-scale unemployment, the city quickly agreed to this proposition.

Alton city boosters were also quick to realize the recreational benefits of the 9-Foot Channel Project. Some local residents saw the potential of utilizing the navigation pool for recreational purposes. Although the Corps of Engineers was allotted money to build public access roads to the navigation pool, Alton civic leaders successfully lobbied the Public Works Administration (PWA) for money to construct a scenic drive along the Upper Mississippi River from Alton to Grafton. The project, which received $900,000 in funding, also called for the employment of 1,800 federal relief workers. [4]

Although the relocation helped Alton's economy, it made little sense from an engineering standpoint. The Alton site was located immediately upstream from the bridges of the Missouri & Illinois Bridge & Belt Railway and the Clark Highway. As a result, the Corps was forced to position the locks in an awkward location. Corps engineers incorporated two of the existing bridge piers into the lock walls, creating a difficult approach into the lock chambers. The site also held the potential for creating scour problems at the railroad and highway bridges. [5]

William H. McAlpine, UMVD head engineer, signed the construction drawings for the twin locks at installation No. 26 in October 1933, shortly after the Corps secured the Alton site. Between 1933 and 1936, the Corps conducted model tests on the structure at the University of Iowa's Hydraulic Laboratory. As a result of these tests, Corps engineers designed the locks to have extensive stone and timber mattresses to protect the bridge piers from scour. [6]

Construction of the Main Lock

The Corps of Engineers always constructed the lock before the dam at each 9-Foot Channel Project complex. The twin locks at No. 26 provided the St. Louis District with its first experience with the massive construction techniques required to build a 9-foot channel. The lessons learned during this difficult, and occasionally disastrous, endeavor provided the Corps with valuable, albeit hard-earned, experience. [7]

In November 1933, the Corps of Engineers put twin locks No. 26 out for bid. When Corps officials opened the bids on December 19, 1933, they discovered that the bid of the John Griffiths & Son Company of Chicago was the lowest. The Griffiths & Son Company bid $3.2 million—$200,000 less than the next lowest bid, and approximately $350,000 less than the Federal Government estimate for the job. Griffiths & Son had an established reputation as large-scale contractors. They constructed both the massive Merchandise Mart and the main United States Post Office in Chicago. However, the firm had virtually no experience in the highly specialized field of river construction. Despite this lack of experience, Griffiths & Son received notice to proceed on the construction of the twin locks in January 1934. [8]

As discussed earlier, the 9-foot canalization had originated as a navigational improvement project but was reshaped into a massive public employment program during the New Deal administration of President Franklin D. Roosevelt. At twin locks No. 26, as at many other 9-foot channel sites, the public works aspects of the job became immediately apparent. Soon after the project's official announcement, Missouri and Illinois politicians began bitterly debating the composition of its work force. Missouri's Senator Clark demanded the labor force be split equally between residents of Missouri and Illinois. But Alton's mayor, Tom Butler, filed a protest with the Labor Department and Missouri's U.S. Senators, arguing that during the negotiations with the Corps for the use of Riverside Park he had been led to believe that the ratio of Illinois to Missouri workers would be three to one. Butler also argued that Madison County, Illinois, had a population six times that of largely rural and agricultural St. Charles County, Missouri, and six times the number of unemployed. Ultimately, Butler's arguments carried the day. [9]

Griffiths & Son relied almost entirely upon local laborers, importing only 15 to 20 key personnel from Chicago. The company hired workers at prevailing rates for the St. Louis metropolitan area, with common laborers earning 60 cents an hour. Unions, however, argued that these predetermined wages were below their regular rates and refused to furnish workmen. In May 1934, the Wage Predetermination Board of the Department of Labor ruled in favor of the unions and held that common laborers should be paid at least 67.5 cents per hour. Griffiths & Son estimated that this rate increase would raise the cost more than $40,300, which the Corps of Engineers agreed to cover. [10]

As at all the other 9-foot channel lock sites, the first step in building the main lock was the construction of a cofferdam. A cofferdam walls off the construction area, enabling the lock to be built "in the dry," while river traffic is rechanneled around the cofferdam. When the lock is completed, the cofferdam is removed and traffic goes through the open lock chamber while work progresses on the dam.

Cofferdams were one of the most important and expensive construction features of the 9-Foot Channel Project. Each contractor was responsible for the design of his own cofferdam. As a result, innovations in cofferdam technology originated with these firms rather than the Corps' design team. Failure of a cofferdam not only destroyed the work done during that contract, but also destroyed work completed by another contractor under a separate contract. Such failures became the subject of lengthy court battles over who had responsibility for the resulting damage. In some instances, these court cases went on for years, involving hundreds of thousands of dollars. [11]

Contractors on the Upper Mississippi 9-Foot Channel Project built two basic types of cofferdams: timber/crib configurations and steel sheet piling configurations. All the timber/crib cofferdams were Ohio River Box type, which had been used extensively since the 1870s. These cofferdams were typically comprised of wood sheathing inside a frame of horizontal walers and tie rods. The cofferdams at No. 26 were constructed of steel sheet piling.

The Corps of Engineers first used steel sheet piling cofferdams during its efforts to raise the Maine from Havana Harbor. Contractors working for the Corps of Engineers began using them on the Ohio River in 1917. However, William McAlpine, then supervisor of construction on the Lower Ohio and later head of the UMVD, discouraged their use. He believed the difficulty and expense of removing the pilings after the work was completed outweighed their advantages. McAlpine apparently continued in this belief at the beginning of the 9-foot channel on the Upper Mississippi, despite the reduced first cost of steel sheet piling and its high salvage value. As a result, contractors did not begin to use steel sheet piling cofferdams on the Upper Mississippi River until after McAlpine was transferred to the office of the Chief of Engineers, removing him from direct supervision of such project details. Thereafter, cofferdams made of steel sheet pilings were in very general use on the project. [12]

A cofferdam walls off a portion of the river, providing a dry work site. Each contractor was responsible for the design of his own cofferdam. Griffiths & Son, the contractor for Main Lock No. 26, began by building a trestle along the center line of the cofferdam site. The trestle supported derricks and cranes that aided in construction and the delivery of materials. Cofferdam Construction for Main Lock No. 26, March 1934. (U.S. Army Corps of Engineers, St. Louis District)

Corps officials approved Griffiths & Son's cofferdam design for Main Lock No. 26 in mid-January 1934. The company designed an exceptionally heavy and strong cofferdam for the site because of the existing swing span railroad bridge. The presence of the bridge required traffic to pass through the auxiliary lock area during construction of the main lock. This, in turn, dictated that the river arm of the main lock cofferdam be placed very near the intermediate lock wall, preventing construction of a suitable stabilizing berm on the inside of the cofferdam. [13]

Griffiths & Son began constructing the cofferdam on the first of February. The company enclosed approximately 13 acres of riverbed with the cofferdam, which consisted of a wall of semi-circular, steel sheet, pile cells. Work crews filled the cells with material dredged from the bottom of the river. Y-connection piles, connected to two structural frames, tied the individual cells together at the panel points. Outside wall piles measured 55 feet in length; inside wall piles were 40 feet long.

The riverbed at Alton consisted of a minimum of 80 feet of sand above bedrock, which forced construction of the cofferdam atop a pile foundation not driven to bedrock. The riverbed also proved particularly susceptible to scour at this location, which threatened to undermine the cofferdam. Griffiths & Son placed a pair of streamlined pile fins around the cofferdam to help smooth the flow of water and, presumably, reduce scour. Workers also placed ballasted brush and timber mattresses against the cofferdam to hold the foundation soil in place.

Griffiths & Son used construction methods for the cofferdam that were very similar to those used on dryland projects. First, the company constructed a wood pile-supported trestle along the center line of the cofferdam site. Railroad tracks atop the trestle supported a succession of derricks and cranes that aided in the construction of the sheet pile cells and the delivery of materials. The company constructed the trestle between early February and mid-April 1934. Workers began placing the steel sheet piling in early March and completed the job by the end of April. [14]

The contractor began draining the cofferdam in early May 1934. Serious seepage problems developed almost immediately. Griffiths & Son stopped the seepage by installing an extensive system of wellpoints that lowered the water surface 1 to 2 feet below grade. The wellpoint system represented an advance over previous methods that relied upon large surface pumps to discharge water from sumps. The new system, which appears to have been first used on the 9-Foot Channel Project in the Rock Island District in about 1933, cost more but afforded a drier work area. By mid-May, the cofferdam was dewatered to the point that Griffiths & Son's pile driver began placing foundation piles for an interceptor sewer designed to carry Alton's existing Piasa Street sewer below the locks. [15]

The 9-Foot Channel Project had generated little local opposition within the St. Louis District. However, Alton residents were concerned that the navigation pool created by the construction of Dam No. 26 would adversely affect the local sewage system. For the river towns along the Mississippi, sewage systems were often a significant source of local pride, serving as physical manifestations of the towns' participation in the urban improvement and reform movements that swept the United States during the decades following the 1893 Columbian Exposition. To alleviate concern that the increased river height would adversely affect sewers, the Corps designed and constructed interceptor sewers that carried the Piasa Street and State Street sewer outlets to a point below the locks. [16]

Workers began driving the first piles for the main lock's land wall in early June. In mid-June, they began working on the intermediate wall foundations. With the exception of the piling for some of the struts between the lock walls, all pile driving within the main lock cofferdam was completed by the end of October 1934. Griffiths & Son organized the pile driving operations into three 6-hour shifts, 5 days a week. Four pile drivers were in daily operation, with a fifth unit held in reserve. During a shift, each rig placed an average of 13 piles. The majority of the piles were 11-inch-diameter, 32-foot-long wood piles. Griffiths & Son's employees placed three rows of tapered, 32-foot, concrete piles on the river side of both the land and intermediate walls. Workers also drove a single row of 40-foot, steel, sheet piling along the outside of the land wall, below the upper miter sill, and through the center of the intermediate wall. This piling acted as a cutoff, preventing the foundation sand from being carried away. Loss of this sand would have removed the lateral and vertical support from around the piles, creating stress and the possibility of a total structural collapse. Driving of the steel sheet cutoff walls began in late June 1934. [17]

The contractor began draining the cofferdam in May 1934; pile driving began the next month. By the end of October, all pile driving was completed. View upstream from cofferdam. October 1934. (U.S. Army Corps of Engineers, St. Louis District)

Unlike the remainder of the lock structure, the Corps located the upper end of the land wall on a rock-filled timber crib surrounding 56-foot wood piles. Griffiths & Son began constructing the cribbing in mid-September 1934. Below the reinforced concrete apron in front of the lower discharge ports, workers laid derrick stone directly atop the sand between the concrete struts to prevent scour. This protection, 4 feet deep and 30 feet wide, was largely placed from atop the intermediate wall. [18]

The lock's massive fixed sides were constructed of concrete masonry, the use of which had been pioneered by the U.S. Army Corps of Engineers. In 1891, Major William L. Marshall, the same officer who initiated the Corps' use of Tainter gates, had conducted the Corps' first "great experiment in river construction" when he used poured Portland cement, rather than cut stone, to construct lock walls on the Illinois and Mississippi (Hennepin) Canal. [19]

Concrete masonry walls were standard practice at the time of the 9-Foot Channel Project. However, the unorthodox construction techniques used by Griffiths & Son to build the concrete walls of Main Lock No. 26 were not. Griffiths & Son's choice of concrete placement would prove to be disastrous.

Griffiths & Son chose to place the concrete with belt conveyors, rather than the usual practice of using gantry cranes and concrete buckets. This decision was apparently made for practical and budgetary reasons; the company had a large number of belt conveyors stored in its Chicago material yard. But the decision had far-reaching effects. If Griffiths & Son had chosen to invest in gantry cranes, the company could have used large, heavy, concrete forms. By choosing to use equipment on hand, Griffiths & Son were forced to use small, easily handled, forms that could fit on belt conveyors.

The smaller forms that fit on the belt conveyors produced 5-foot-tall monoliths, which contained only 90 to 200 yards of concrete. These forms were so small that a standard day's production required the completion of five to eight monoliths, placing considerable strain upon the complex belt conveyor distribution system. The capacity of the concrete mixing plant, which was located on shore, exceeded that of the conveyors. When Griffiths & Son ran the mixing plant at capacity, concrete inundated the forms. This forced a delay of several minutes while the concrete was shoveled down and vibrated into place. Further complicating the process was the fact that workers needed to shift the belt conveyor distribution system each time they began working on a new monolith. The Corps of Engineers later estimated that the combination of light concrete forms and the belt conveyor distribution system added approximately $1.50 to the cost of each cubic yard of concrete above the cost of using gantry cranes and concrete buckets.

Griffiths & Son began placing concrete in mid-August 1934. The company had planned to construct the lock walls in a pyramidal fashion, broadening the base as the upper pours advanced. Throughout August, Griffiths & Son's workers placed concrete at the rate of one footing monolith per day. The small amount of yardage contained in the monoliths, and the large amount of carpentry work required to form each monolith, slowed production and prevented placement of more than 700 yards per day. The high form costs and disappointing progress led Griffiths & Son to increase the monolith heights to 10 and later 15 feet beginning in November 1934. Still, Griffiths & Son's workers were placing concrete well into 1935.

The delays in concrete placement caused a delay in steel erection. Steel workers could not begin until the top concrete lifts at the gate bays, which included the gate anchorages, were completed. Workers started erecting steel in mid-February 1935, beginning with the upper gate leaf for the intermediate wall. Griffiths & Son crews began riveting the upper gate leafs in early March, and the lower gate near the end of April. But Corps personnel at the site complained that Griffiths & Son's steel erection lacked organization and planning. Riveting gangs failed to follow closely upon the erection gang, despite repeated insistence on the part of Government engineers. The lack of gantry cranes also greatly delayed this phase of the construction. In March 1935, the Upper Mississippi River overtopped the cofferdam, further complicating the situation. The river deposited 4 to 12 inches of silt on the lock floor.

After the piles were driven, workers began building the monolith forms used for concrete placement of the lock walls. Construction of Main Lock No. 26, September 1934. (U. S. Army Corps of Engineers, St. Louis District)

Finally, Griffiths & Son completed the main lock in late September 1935, and began removing the cofferdam. However, the heavy construction of the cofferdam delayed its removal which, in turn, delayed the start of the auxiliary lock cofferdam. The company could not construct the auxiliary lock cofferdam, which would have blocked river traffic, until the completed main lock was open for navigation. [20]

Construction of the Auxiliary Lock

The U.S. Army Corps of Engineers incorporated provisions for auxiliary locks into the majority of the 9-foot channel sites. However, the Corps completed auxiliary locks at only two of the original 9-Foot Channel Project installations constructed between 1930 and 1940: Lock and Dam No. 15 and Lock and Dam No. 26. At the other locations, the Corps stubbed-in the foundations for auxiliary locks, but never built them. The Corps engineers equipped the auxiliary lock foundation with portions of the river wall, machinery recesses, and upper lock gates that could be opened for traffic during periods when the dam was fully raised and the pool drawn down. [21]

Griffiths & Son's construction of the auxiliary lock at No. 26 was calamitous. During the construction of the main lock, the company's decision to place concrete by using belt conveyors rather than gantry cranes had significantly slowed down the construction process. The company began working on the main lock on February 1, 1934, but did not complete the job until September 1935. By the time Griffiths & Son began constructing the auxiliary lock the following month, it was dangerously close to the onset of winter. While river ice conditions were less than ideal, they may have been manageable if they had not been combined with the contractor's unorthodox construction practices.

Griffiths & Son's crews began building the river arm of the auxiliary lock cofferdam in early October 1935. By mid-December, workers had completed both the river and lower arms of the structure. Then, despite the objections of the Corps' resident engineer, H.S. Pence, Griffiths & Son closed off the lower arm of the cofferdam in hopes that the river would deposit the 2 to 8 feet of fill required to bring the auxiliary lock site up to grade.

On December 19, 1935, the temperature fell sharply. On December 20, heavy ice started to run in the river. By December 26, the auxiliary cofferdam was filled with ice. In early January 1936, ice damaged a portion of the river fin, an extension of the cofferdam designed to streamline the flow of water around the structure. Repair efforts proved unsuccessful. As a stopgap measure, the Corps placed a barge loaded with derrick stone against the fin to protect it from the flowing ice. Griffiths & Son resumed cofferdam driving on January 15, and completed all but three cells in the upper arm of the cofferdam before cold and ice again halted the work on January 17.

Extremely low temperatures prevailed, and by the end of February the entire river was gorged with heavy ice. On the night of February 26, a large gorge of ice upstream from the lock broke up and caused considerable damage to the fin on the lock side of the cofferdam. On February 29, the river fin failed completely and the sheet pile cells of the cofferdam collapsed like dominoes. Almost the entire upper and river arms failed. In addition to the cofferdam, a crane, a steam hammer, and assorted other materials plunged into the river.

Following the collapse of the auxiliary lock cofferdam, Griffiths & Son began to disband their work force and remove their equipment from the job site. On March 18, 1936, in reply to a telegram from the District Engineer, Griffiths & Son stated that it was not obligated to assume the construction hazard associated with completion of the auxiliary lock, since the Corps had ordered the Engineering Construction Company, the contractors for the construction of Dam No. 26, to proceed with the second section of the dam cofferdam. The District Engineer notified Griffiths & Son of the Government's intention to terminate their contract on April 2, 1936. On April 7, Griffiths & Son informed the Corps that it had abandoned work and would proceed to remove its equipment and material.

By January 1935, the construction of Main Lock No. 26 was well underway. (U.S. Army Corps of Engineers, St. Louis District)

With the departure of Griffiths & Son, the Corps was left with the responsibility for removing the collapsed cofferdam, as well as preventing damage to the completed main lock. In late April 1936, the Corps placed 820 feet of timber mattress against the intermediate lock wall to prevent scour. Throughout May, Corps crews also removed the standing cells of the auxiliary lock cofferdam to prevent eddies and facilitate the passage of river traffic. In June, Corps workers began searching for the collapsed cofferdam. In order to remove the cofferdam, the Corps had to know the precise location and depth of the collapsed cells. The cofferdam also had to be removed quickly in order to avoid delaying the dam contractor, who was expected to complete work within his second cofferdam by late fall of 1936. Divers successfully located the cells, which they found laying nearly horizontal beneath 8 to 18 feet of sand.

W.F. Goodson, one of the engineers engaged in the raising of the battleship Maine and then assigned to the Buffalo District of the Corps of Engineers, assisted in the removal effort. Dredges removed the sand atop the collapsed cells. Divers then attached shackles to the sheets, which were hauled free in groups of 12 to 20 by a derrick boat. The Corps removed most of the collapsed cells by late September 1936. The dam contractor located his third cofferdam, which included this area, so as to avoid any unrecovered sheets. The Corps of Engineers removed the cofferdam with remarkable speed, partly because of the abnormally low water levels experienced during 1936. As a result, the dam contractor was able to access the area on schedule in November 1936.

The failure of Griffiths & Son to complete their contract provided Corps officials with valuable information regarding the appropriate manner in which to approach construction projects of this magnitude. Griffiths & Son's low bid virtually mandated that the company use the most efficient equipment and operational plan available if the job were to be profitable. Instead, Griffiths & Son developed a plan based on equipment on hand rather than the most suitable and efficient. Likewise, the firm, though inexperienced in river construction, had made no attempt to secure the services of an experienced superintendent.

Griffiths & Son also failed to take into account the complexities of the job. The company's inattention to dredging the subgrade within the cofferdam required the removal of large amounts of fill by dragline which, along with inadequate control of pumping, delayed pile driving. Griffiths & Son also failed to adequately plan the layout of the piling, which delayed preparation of the foundations at the gate bay areas and, consequently, delayed concrete placement and the erection of the miter gates. Corps engineers also estimated that if the contractor's crews had worked 24 hours a day on the main lock cofferdam, the job could have been finished by April 1935, 5 months ahead of the actual completion date. In turn, completion of the main lock in April would have permitted completion of the auxiliary lock cofferdam prior to the onset of river ice, thus avoiding the disastrous cofferdam failure. [22]

Construction of Dam No. 26

Upper Mississippi Valley Division Senior Engineer A.F. Griffin signed the construction drawings for Dam No. 26 in December 1934. Griffin and the UMVD team designed the 1,724-foot-long movable dam with 3 steel roller gates, each 25 feet deep and 80 feet long, and 30 submergible steel Tainter gates, each 30 feet high and 40 feet long. The engineers located the roller gates in the center of the dam, flanked on either side by 15 Tainter gates. Individual electrically-driven gear reduction units, mounted either on the roller piers or beneath the service bridge spans, raised and lowered the roller and Tainter gates respectively. The Corps also equipped the installation with a steel deck girder service bridge that extended across the entire length of the dam. A 75-ton locomotive crane was mounted on rails atop the bridge. An earthen dike, adjoining the Missouri abutment at an angle, extended nearly 900 feet to the embankment of the Missouri & Illinois Bridge & Belt Railway.

Concrete placement for Dam No. 26 was accomplished with gantry cranes and buckets, which were more efficient than the belt conveyor system used during the construction of the main lock. Construction of Dam Pier No. 27, November 1935. (U.S. Army Corps of Engineers, St. Louis District)

The Corps of Engineers received four bids for the construction of Dam No. 26. The Engineering Construction Company of Delaware was the lowest. The company was a joint venture of the George A. Fuller & Company, the Turner Construction Company, and Spencer, White & Prentis, and had been organized for the sole purpose of securing the Dam No. 26 contract. The company's bid of nearly $4.9 million was almost $200,000 less than the next lowest bid, but $650,000 above the government estimate for the job.

The Engineering Construction Company received notice to proceed in mid-June 1935, and immediately established a construction plant on the Missouri shore of the river. The member firm of Spencer, White & Prentis designed the plant. The company had recently completed Lock and Dam No. 6 at Trempealeau, Wisconsin, and was also, at the start of this contract, constructing Lock No. 3 at Red Wing, Minnesota.

In marked contrast to the land-based construction techniques of Griffiths & Son, the Engineering Construction Company designed their entire operation according to generally accepted principles of marine construction. In addition to locally-hired labor, the Engineering Construction Company staff included between 30 and 35 experienced specialists. Again, this differed from Griffiths & Son, who had no personnel experienced in river construction.

The Engineering Construction Company constructed Dam No. 26 within three cofferdams. The first cofferdam enclosed an area that included the site of the Missouri abutment and the 12 Tainter gate bays adjacent to the abutment. In late June, workers began constructing this cofferdam, which consisted of 2 rows of interlocking steel sheet piling, ranging in length from 37 to 60 feet, spaced 30 feet apart and connected by tie rods. Sand filled the space between the two rows of sheet piling, and was bermed against both the outside and inside walls. Timber guide piling carried the templates for the steel sheet piling. The contractor completed the cofferdam after 45 working days.

Workers drained the first cofferdam by the end of August, and began driving the dam's timber pile foundation. By mid-December, the Engineering Construction Company had driven a total of 5,100 wooden piles, an average of nearly 3 piles per hour for each of the 2 driving rigs. A continuous, 47.5-foot-deep, steel sheet-pile, cutoff wall extended across the length of the dam above the piers. The company located a second cutoff wall, 24.5 feet deep, at the downstream edge of the stilling basin. Transverse walls of sheet piling connected the upstream and downstream cutoff walls every 96 feet. [23]

Workers began placing concrete in mid-October 1935. The contractor used a floating concrete plant, which included a pair of 1.5 cubic yard Ransome mixers with accompanying scales, hoppers, and bins, to supply the concrete. The Engineering Construction Company also used a series of belt conveyors to carry the concrete over the cofferdam and into a large hopper situated on locomotive tracks. The concrete was then released into 62-cubic-foot dump buckets on flat cars. The flat cars hauled the concrete to the gantry cranes, which lifted the buckets to the point of placement. The method of concrete placement underwent minor modification during the course of construction. Piers 29 and 31 in the first cofferdam were placed in accordance with the contract specifications, which called for two separate lifts. Tests on these piers showed no fatigue or form distress, and it was determined to place the next pier continuously to full height. This proved successful and permitted elimination of the 22 to 24 hours of rest time previously required between lifts, increasing the rate of construction to 2 piers per week.

The Engineering Construction Company completed work within the first cofferdam by the end of February 1936. Workers removed the steel sheet piling by the end of May. This material was reconditioned for use in the second cofferdam, which had been begun in early February 1936. The second cofferdam slightly overlapped the first cofferdam, enclosing an area for the construction of six Tainter gates and the three roller gates. The Engineering Construction Company designed and constructed the second cofferdam in a similar way to that of the first, with the overlapping section used as a locking chamber for the storage of forms, cranes, and other construction equipment. The cofferdam was closed in mid-May 1936, despite a failure of the guide piling and trestle work of the upper arm at the beginning of the month. Construction crews drove the last steel sheet piling during early June.

(Top) Tainter Gate Assembly on Dam No. 26, December 1935. (Bottom) Aerial view of cofferdam surrounding Dam No. 26, August 1937. (Both photographs: U.S. Army Corps of Engineers, St. Louis District)

The contractor began to dewater the second cofferdam in mid-June 1936. A unique feature associated with this process was the use of a floating crane and pile driver within the cofferdam. These rigs spread stone for the inside berms and drove the piles for the gantry crane trestles prior to the completion of dewatering. The Corps of Engineers estimated that this innovation saved 10 to 15 days of work. The contractor's crews began driving piles in the second cofferdam in late June 1936; the first concrete placement occurred about a month later.

The American Bridge Company began erecting the Tainter gates in early August, and a month later started erecting the three roller gates. By the end of October, work within the second cofferdam was completed. The cofferdam was removed by early December. The principal change in procedures between the first cofferdam and the second stemmed from the American Bridge Company's full use of the service bridge for both the delivery of steel into the cofferdam and as a base for the guy derrick used to erect the steel. [24]

The American Bridge Company was the subcontractor for steel fabrication and erection. The firm established its field office at the site in mid-October 1935, and began erecting steel eye bar assemblies in late November. The company had originally planned to transport structural steel members into the cofferdam by means of the service bridge. However, earth slides along the Missouri abutment delayed the construction of the service bridge, forcing American Bridge to build a temporary trestle. As a result, the American Bridge Company did not begin erecting the service bridge until January 1936. However, to prevent delays, members for the Tainter gate A-frames were brought by rail onto the lower arm of the cofferdam, and moved into the gate bays by gantry cranes. American Bridge Company crews erected the steel within the bays. United Construction Corporation crews placed all the reinforcing and embedded anchorage assemblies for the Tainter gates. The trunnion pins, on which the gates moved, were placed and aligned by American Bridge Company crews, and the enclosing stirrups later pre-stressed, under a 500,000-pound load, to the embedded anchorage assembly.

The American Bridge Company had the roller gates partially shop-assembled at its plant, and shipped to the construction site for erection. The Tainter gates appear to have been assembled in the field. The American Bridge Company also had the roller gate operating machinery shop-assembled and erected atop the piers prior to the construction of the poured-in-place operating houses. Falsework supported the gate sections during the erection process. The company erected the end sections first, and carefully positioned them into their precise operating positions. Crews then assembled the central section, which was bolted to the ends. The entire gate was aligned, the apron placed, the gate riveted and realigned. The inclined racks in the pier recesses were lined, leveled, and grouted into place. After the grout set, workers connected and adjusted the hoist chain, rolled up the gate, and dismantled the falsework. The gate was then rolled down into its closed position so that the Corps could check the alignment of the seal. Finally, the end shields were straightened and realigned into their final position. [25]

Construction of the Central Control Station, Dam No. 26, September 1937. (U.S. Army Corps of Engineers, St. Louis District)

Engineering Construction Company crews began building the third cofferdam in late September 1936. This cofferdam enclosed the remainder of the dam area, as well as the site of the auxiliary lock. In mid-November, the contractor closed the upper arm of the cofferdam without incident. The lower arm was closed approximately a month later and dewatering operations started immediately. Work in the third cofferdam progressed in the same fashion as previously described. The contractor's employees began driving piles in mid-December 1936, and essentially completed the job by the end of April 1937. Concrete placement began at the end of January 1937. The American Bridge Company began erecting Tainter gate steel in mid-April and, at one point, managed to complete two gates per week. [26]

With the completion of the 9-Foot Channel Project, the Corps of Engineers made the Mississippi River fully navigable, providing for efficient transportation of materials and people. Steamships and Barge in Main Lock No. 26, June 1938. (U.S. Army Corps of Engineers, St. Louis District)

The Corps of Engineers located the central control station for Lock and Dam No. 26 on the river wall against the dam. Based upon their experiences at other Mississippi River sites, Corps engineers found that reinforced concrete tended to crack and check in thin building walls, permitting objectionable condensation on the building's interior walls. As a result, the Corps redesigned the control station at Lock and Dam No. 26 as a brick and tile building with a structural steel frame. The Corps constructed the control station between July and December 1937. [27]

Work within the third cofferdam was completed in September 1937. Work crews finished removing the sheet piling by the end of December 1937. On January 21, 1938, the Federal Government declared the contract completed. In its final report on the project, the Government praised the experience and efficiency of the member firms of the Engineering Construction Company. The experience gained during work on Dam No. 26 convinced engineers in the St. Louis District that planning and experience were as important, if not more so, than price on such a large-scale construction project. All future work in the district was accomplished by firms experienced in river construction. [28]


1. Dobney, River Engineers, 150.

2. "Mississippi River Lock and Dam No. 17: Final Report Construction," Vol. I: "Introduction, Lock, and Temporary Buildings" (Rock Island: U.S. Army Corps of Engineers, Rock Island District, March 1938), 3, RG77, Entry 81, Box 666, NACB; and H. Doc. 137, 1-10.

3. H. Doc. 137, 120.

4. David W. Moore and Frederick J. Dobney, "Engineers, Environmentalists, and the Replacement of Locks and Dam No. 26: A Study in Passion, Politics, and Principle" (n.d., photocopy in the files of the Office of History, U.S. Army Corps of Engineers, Fort Belvoir, Virginia), 24-25.

5. Alton (Illinois) Evening Telegraph, September 13, 1933, 1; September 15, 1933, 1; and September 16, 1933; and Journal of Wood River Township, March 13, 1975 (clipping file at Hayner Public Library, Alton, Illinois).

6. Mudd, "Locks and Dams No. 26," 2.

7. Lock and Dam No. 26R, which opened in 1990, is not, technically, part of the original 9-Foot Channel Project, and is the only instance where a portion of the dam was constructed prior to the main lock.

8. Journal of Wood River Township, March 13, 1975; "Final Report—Lock and Dam 26, Part I," 1; and Alton Evening Telegraph, December 19, 1933, 1.

9. Alton Evening Telegraph, December 23, 1933, 1; and "Final Report—Lock and Dam No. 26, Part I," 8.

10. "Final Report—Lock and Dam No. 26, Part I," 7.

11. Final Report Lock 11, 60; and McCormick and Dixon, "Mississippi River Cofferdams," 105-107. In the Rock Island District, cofferdams failed in April 1934, during the construction of Lock No. 21; in April 1936, during the construction of Dam No. 11; and in January 1938, during the construction of Dam No. 17.

12. McCormick and Dixon, "Mississippi River Cofferdams," 106; and Johnson, Louisville District, 183.

13. Alton Evening Telegraph, January 9, 1934, 1; and January 22, 1934, 1; "Final Report—Lock and Dam No. 26, Part I," 9, 13-14; and E.P. Ketchum, "Removing a Collapsed Cofferdam," The Military Engineer 29 (May-June 1937): 203.

14. "Final Report—Lock and Dam No. 26, Part I," 29-30; and Carl Stopp, "Report of Main Lock Cofferdam Twin Locks No. 26, November 1934," 2-5 (on file at St. Louis District Office, U.S. Army Corps of Engineers).

15. McCormick and Dixon, "Mississippi River Cofferdams," 105-108; "Final Report—Lock and Dam No. 26, Part I," 31; and Stopp, "Main Lock Cofferdam," 5-6.

16. Lois Craig, et al., 210-214; and "Final Report—Lock and Dam 26, Part I," 63-64.

17. "Final Report—Lock and Dam No. 26, Part I," 35-38; and Mudd, "Locks and Dam No. 26," 4. Concrete piles appear to have been used at both Lock No. 26 and Lock No. 25, the two pile-founded lock installations constructed in the St. Louis District during the 1930s. The concrete piles were placed in areas that supported heavy loads, principally at the edges of the lock walls and at the junctures between the walls and the miter gate sills. The installations constructed in the Rock Island and St. Paul Districts during this period do not appear to have utilized concrete piles.

18. "Final Report—Lock and Dam No. 26, Part I," 39.

19. By the 1880s, engineers in France had used concrete construction for shore protection, and American engineers had used it to build fortifications. Marshall learned about locks and dams when in charge of the Fox and Wisconsin Rivers prior to 1888. The Corps began building the locks, dams, and canals along the Fox in 1872 under Colonel David C. Houston and completed it in 1904, by which time it had built 18 new locks, 9 composite locks, and 13 canals. Prior to 1888, Marshall also experimented with a method of pouring concrete walls when he worked on a project to protect Chicago's Lincoln Park lakefront. He adapted this system to lock construction on the Illinois and Mississippi (Hennepin) Canal Project. The methods and machines he and his assistants developed for the Hennepin project became standard industry practice and helped revolutionize American building practices. Even before Marshall's Hennepin Canal structures were complete in 1908, other Corps officers also built poured concrete locks. The 10 locks and dams designed between 1896 and 1898 under Lieutenant William L. Sibert for the White River in Arkansas included poured concrete locks. Subsequently, while serving as Pittsburgh District Engineer (1902-1905), Sibert served as a member of the Isthmian Canal Commission. There, Sibert was instrumental in carrying concrete lock construction into the Panama Canal designs. Sibert also served as a member of the Special Board of Engineers headed by Colonel Daniel Lockwood that chose concrete construction for the design of the new Ohio River locks in 1905-1906. While the Ohio River locks were being designed, Hugh L. Cooper, working closely with Montgomery Meigs, designed the Keokuk Lock, the first Upper Mississippi River lock in the Rock Island District built of concrete. Annual Report 1981, 2651; Merritt, Creativity, Conflict and Controversy, 257; Tweet, Rock Island District, 163-166; and Yeater, "Hennepin Canal," Section 8:12-13.

20. "Final Report—Lock and Dam No. 26, Part I," 14, 40-41, 46-51.

21. Roberts "Canalizing for 9-ft. Navigation" 324; Daley, "Canalization of the Upper Mississippi," 105; and Gross and McCormick, "Upper Mississippi River Project," 314.

22. Ketchum, "Removing a Collapsed Cofferdam," 203-206; and "Final Report—Lock and Dam No. 26, Part I," 52-62.

23. "Final Report—Lock and Dam No. 26, Mississippi River, Alton, Ill., Part II—Dam/Auxiliary Lock" (St. Louis: U.S. Army Corps of Engineers, St. Louis District), (hereafter referred to as Final Report—Lock and Dam No. 26, Part II), 1, 8, 26, 30-31, 38-39, typescript draft on file at St. Louis District Office; and Mudd, "Lock and Dam No. 26," 4.

24. "Final Report—Lock and Dam No. 26, Part II," 9, 31, 40-41, 45-48.

25. "Roller-Gate Dam Erection," 412-414.

26. "Final Report—Lock and Dam No. 26, Part II," 32-34, 38, 48.

27. Ibid., 49.

28. Ibid., 10, 50.

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Last Updated: 01-Feb-2008