State Highway 34 Bridge at the Trinity River

The State Highway 34 Bridge at the Trinity River was built from 1933 to 1934 with emergency relief funds. Because of its association with a federal work relief program implemented during the Depression, the bridge meets Criterion A in the area of Transportation (subcategory Depression-era Public Works) at a state level of significance. The bridge is also significant for embodying the defining characteristics of a THD truss bridge and therefore meets National Register Criterion C in the area of Engineering at a state level of significance.

The Trinity River bridge was built on SH 34 which formed a loop running west, south, and east of Dallas. The route linked Jacksboro, Fort Worth, Waxahachie, Ennis, and Kaufman, and continued north through Greenville, Ladonia, Honey Grove, and Telephone into Oklahoma. The majority of the eastern portion of the original route, from Ennis to Honey Grove, is still designated SH 34.

As a National Recovery Secondary (NRS) project, the Trinity River Bridge project was funded almost entirely with federal emergency funds authorized under Section 204, Title II, of the National Industrial Recovery Act of 1933 (NIRA). This legislation provided federal monies to supplement state highway funds that the Depression had severely curtailed. By providing additional federal aid, NIRA helped to maintain highway construction spending at pre-Depression levels. The act's primary goal was to boost employment and establish standards for wages. Texas received nearly $25 million in emergency construction funds under this legislation; the Trinity River bridge was one of 543 Texas emergency projects funded under NIRA.

The bridge was built as part of a larger THD undertaking to reconstruct SH 34 between Ennis and the Kaufman County line on a new location. In addition to the construction of the truss bridge, the project included new roadway grading and concrete drainage structures, including the two borrow pit bridges. The borrow pits had been dug previously to provide earth for forming the Trinity River levees. Two pits were dug for each levee. Rather than haul dirt to the site to fill in the borrow pits, THD decided to construct bridges over them, probably because this was the more economical choice. The main bridge spans the Trinity River bottom as well as the two interior borrow pits. The two additional concrete structures span the exterior borrow pits.

THD prepared the plans for the project and, because it received federal aid, the Bureau of Public Roads (BPR) reviewed and approved them. Even though plans to develop navigation on the Trinity River above Liberty (northeast of Houston, near the Gulf) were abandoned in 1922, the river fell under the jurisdiction of the War Department as a navigable waterway. As such, THD was required to submit the plans to that agency for its approval.

THD bridge engineers chose the T22-150 design for the truss span of the Trinity River bridge. The T22-150, designed about 1930, is one of 25 THD standard designs the Bridge Division developed for Parker through truss spans; only 11 of these designs are represented by Texas bridges today. The Trinity River bridge is one of four examples of the T22-150 standard design surviving in Texas.

At just over 1700 feet, the Trinity River bridge is the third longest Parker through truss bridge remaining in Texas and is the earliest of the three. The bridge's 53 I-beam spans, totaling 1,556 feet, provide the second longest approach for a simple truss bridge on a Texas state highway.

The call for bids took the form of a contractor's notice published in local newspapers in early November 1933. In addition to describing the scope of the project, the notice informed bidders of special provisions under NIRA requiring "the use of domestic materials, the selection of labor, hours and conditions of employment, and hand labor methods." Under these provisions, which were implemented to increase employment levels, all carpentry work and painting had to be performed without the use of power tools, such as mechanical saws and electrical drills. THD had also disseminated these provisions in an "Important Notice to all Contractors, Materialmen, Bondsmen and Division Engineers" dated October 5, 1933.

The Texas Highway Commission opened bids for the construction of the Trinity River bridge and borrow pit bridges on November 11, 1933. After reviewing the two bids submitted, the commission awarded the contract to the Austin Bridge Company of Dallas, which submitted a low bid of about $110,000. The Petroleum Iron Works Company of Beaumont fabricated the steel portions of the truss and I-beam spans.

Work on the three bridges began on December 1, 1933, and was completed in November 1934. The THD resident engineer in Ennis supervised the construction, which engineers from both THD and BPR inspected. High water caused some difficulties during the construction of the pier foundations, but the total cost of the three structures was still below $118,000.