State Highway 29 Bridge at the Colorado River

The State Highway 29 Bridge at the Colorado River, constructed in 1937, is significant for embodying the defining characteristics of a THD truss bridge. As such, it meets National Register Criterion in the area of Engineering at a state level of significance.

The Colorado River bridge was built on SH 29, which linked Austin with Mason, Llano, and Burnet in the Hill Country to the west, and with Port Lavaca on the Gulf Coast. Sections of the route just east of Llano paralleled a branch of the Texas & New Orleans Railroad (later the Southern Pacific Railroad).

The construction of the Colorado River bridge was part of a larger THD undertaking to reroute SH 29 around Buchanan Dam, which was under construction beginning in 1931. The original roadway and the bridge across Colorado at Bluffton were inundated by Lake Buchanan after the completion of the dam in 1937. In September 1931, the Texas Highway Commission agreed to accept $135,000 from the Emery, Peck, and Rockwood Development Corporation, the developer of the Buchanan (then Hamilton) Dam, for damages done to SH 29 and the bridge at Bluffton by the dam's construction. Two months later, the development corporation sold out to the Central Texas Hydro-Electric Company, a subsidiary of the utility empire run by the Insull brothers. The power company acknowledged the obligation to THD and signed an agreement in March 1932. A check for the first $5,000 payment was attached; two more $5,000 payments were to be made on the 10th of April and May of that year, and monthly payments of $10,000 were to follow until the total was paid.

THD first developed the plans for the new Colorado River bridge in 1929. These plans included a 20-foot roadway width, reflecting THD's original intent to construct a somewhat modest bridge using only state funds. When, in 1932, Gibb Gilchrist, then State Highway Engineer, initiated a request for federal aid funding for the bridge construction, he insisted that the original plans be included for approval by the Bureau of Public Roads (BPR). This was done against the advice of THD bridge engineers, who pointed out that federal aid requirements called for a wider roadway width. In a March 10, 1932, memorandum, George Wickline, then State Bridge Engineer, informed Gilchrist that compliance with BPR standards would "mean a slightly higher type of design for the Colorado River bridge than ... at first proposed. The engineers at the Bureau of Public Roads would insist on a 22 ft. roadway for the Colorado River bridge." But Gilchrist maintained his original position. In a March 14, 1932, memorandum to Wickline, he responded, "I do not want a design that would be uneconomical just to get the Federal Aid, but I would like to try them out on it... I would not ... change my design. Give them a chance at it and if they turn it down, then all right." Unfortunately, no records document whether or not the design was actually submitted to BPR.

On April 20, 1932, the Insull utility empire, including the Central Texas Hydro-Electric Company, went into receivership. Work on the dam ceased and THD put the Colorado River bridge project on hold. In 1934, the Texas Legislature created the Lower Colorado River Authority (LCRA). The following year, construction resumed on the Buchanan Dam; construction on Inks Dam, about 3 miles downstream of the bridge site, was initiated in 1936.

In May 1935, when planning on the bridge project resumed, Gilchrist again denied revisions to the original design, believing that if federal funding did not come through, he could rely on the $125,000 remaining to be paid for damages to the Bluffton bridge. In a memorandum to Wickline dated May 21, 1935, Gilchrist insisted, "I do not see any reason why we should revise the plans for the Colorado River Bridge. I think the power company is going to furnish the money and I want you to see me before you make any change in the designs." By this time the obligation fell on LCRA, which agreed to pay the money out of the next allotment to be received "within the next few months." LCRA officials urged THD to go ahead with the bridge construction but D.K. Martin, a Texas Highway Commissioner, believed it unwise to award the contract for the bridge project until THD had been paid the full amount.

It is unclear whether THD ever received such funds, but in 1936 THD engineers proceeded with the redesign of the bridge to comply with the latest federal requirements. As a result of the revision, which included a 24-foot roadway, federal aid was approved, and the planning process continued with the involvement of BPR engineers. THD and BPR engineers performed several site inspections to ensure the best location and alignment for the bridge. The bridge site was fixed 1 mile below the Buchanan Dam, at a location where a granite outcropping formed a ledge at the east bank of the river. This ledge was considered an ideal location for the eastern approach to the bridge. In a preliminary inspection report dated July 17, 1936, the BPR engineer summarized, "The bridge site is quite clearly established by the terrain and the surrounding country, there being a high ledge on the east bank that affords a good location for the approach to the structure."

Solid granite also filled the underlying strata where the bridge substructure would be built, facilitating the use of spread footing foundations. Consideration was given to constructing the piers at a 20-degree angle to the bridge's centerline to minimize the force of floodwater and drift on the piers. Instead, final plans revealed that "on all of the piers used under the main truss span, a lenticular type nosing is shown, which is considered quite essential at this location." Only four highway truss bridges using piers with "lenticular nosing" (pointed ends) survive in Texas.

In addition, the final design included a unique steel railing on the approach spans, consisting of curved-top steel posts with attached steel channel railing. The posts were constructed from steel railroad cross ties modified by cutting, bending, and welding them to form a curved top. The plans were submitted to BPR engineers who approved federal aid for the project. BPR and THD engineers performed period inspections of the bridge construction, which the THD resident engineer in Burnet supervised.

THD bridge engineers chose the T24-200 design for the truss spans of the Colorado River bridge. Designed about 1932, the T24-200 is one of 25 different THD standard designs the Bridge Division developed for Parker through truss spans; only 11 of these designs are represented by Texas bridges today. The Colorado River bridge is one of two bridges conforming to the T24-200 design, and with its four truss spans, unusual piers with pointed ends, and curved-top steel railing, is the better of the two examples.

The Texas Highway Commission held bidding for the project in November 1936. After reviewing the bids submitted, the commission awarded the contract to the Austin Bridge Company of Dallas, which submitted a low bid of about $182,000. The Pittsburgh-Des Moines Steel Company of Des Moines, Iowa, fabricated the bridge's four truss spans. The North Texas Iron & Steel Company of Fort Worth fabricated the 11 steel I-beam approach spans. Work on the bridge began on February 4, 1937, and was completed on September 30, 1937, 45 days ahead of schedule. The project cost totaled nearly $188,000; the federal contribution came to about $94,000.

The bridge was dedicated on October 16, 1937, as part of the dedication ceremony for the Buchanan and Inks dams. The ceremony included an address by U.S. Public Works Administrator Harold L. Ickes which was broadcast live throughout the state. Texas Highway Commissioner Robert Lee Bobbitt gave the dedication speech for the bridge.

Returning from a trip to see the Colorado River bridge, as well as the bridge over Colorado in Marble Falls, Acting Bridge Engineer Herbert Eldridge, commended THD Division 14 (now Austin District):

I find that these structures present a pleasing appearance resulting from the highest type of construction and promise was evident during the construction inspections. Too frequently we accept a job well done as being only in the line of duty but this office desires that you and your capable organization in Division 14 know that we appreciate your efforts in securing such splendid construction. We are encouraged by such results toward a more progressive era of bridge design. Bridge construction in Division 14 has been generally above the average and we are confident that you will continue to show advanced improvements in bridge construction.

Of the State Highway 29 Bridge over the Colorado River, he said specifically, "The design and workmanship on the substructure are particularly commendable. We believe these piers and bents provide the most satisfactory appearance of any bridge constructed by this department."