Fire and Reconstruction at Lobato Bridge in New Mexico
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Fire and Reconstruction at Lobato Bridge in New Mexico FREDERICK R. RUTZ, TODD M. RILEY, AND PETER FOSTER The oldest bridge in New Mexico was Introduction resulted in the D&RG abandoning the goal of building south to El Paso and devastated by fire, leaving an operat - Fire broke out at the Lobato Bridge, a focusing instead on building west to the ing railroad with difficult choices for vital feature of the Cumbres and Toltec mining camps of Leadville, Colorado, Scenic Railroad (CTSRR), a National balancing its reconstruction with and the San Juan Mountains of south - Historic Landmark, on the night of historic preservation. west Colorado. 4 June 23, 2010. 1 By morning it was clear In 1879 reconnaissance surveying that the bridge had been severely dam - was conducted, and contracts were let aged and that operations of historic for the construction of the San Juan excursion trains would be interrupted, Extension. By April 1880 service was for how long no one knew. 2 The cause extended from Alamosa, Colorado, to was not clear — the railroad had oper - Antonito, Colorado, and by February 1, ated over 120 years without this kind of 1881, service was extended from An - disaster. tonito over Cumbres Pass to Chama, New Mexico. Building the section of The Railroad, Past and Present line between Antonito and Chama was a The Lobato Bridge, originally known as formidable task that included construct - the Wolf Creek Trestle, is located on the ing two large bridges and two tunnels, San Juan Extension of the Denver and dealing with grades exceeding four Rio Grande Railroad (D&RG). percent, maneuvering across the sides of Gen. William Jackson Palmer founded steep canyons, and crossing Cumbres the Denver and Rio Grande Railway Pass at an elevation of more than Company in 1870. The original plan for 10,000 feet. The line was completed to the railroad was to build a line from Durango, Colorado, by July 1881 and Denver, Colorado, to El Paso, Texas, a to Silverton, Colorado, in July 1882. 5 distance of 870 miles. A narrow-gauge The two large bridges of the Cum - system with a 3-foot width was selected, bres and Toltec Scenic Railroad are the based on reduced cost compared with Cascade Bridge, with a span of more larger gauges and more favorable opera - than 400 feet at a height of more than tions in mountainous terrain. 3 The 3- 130 feet, and the Lobato Bridge, with a foot narrow gauge was more nimble, span of more than 300 feet at a height allowing trains to execute tighter turns of more than 100 feet. Originally, both and climb steeper grades; it could also bridges were constructed of wood. accommodate smaller locomotives and Noted nineteenth-century engineer C. rolling stock. Shaler Smith was retained by the D&RG The advent of the San Juan Extension to design both bridges. The earliest date is based on several important occur - of Smith’s design on surviving drawings rences: the Brunot Treaty and subse - for the Lobato Bridge is November quent treaties and agreements with the 1880, although records indicate the Fig. 1. K-36 Class engine #488 crossing Lobato crossing was built in wrought iron in Bridge with passenger train. View from below Ute Indians, which led to opening of the 1883. 6 prior to the fire. Photographer and date un - San Juan region to mining and agricul - known. From Richard L. Dorman Collection, ture; and the railroad wars between The San Juan Extension between Catalog No. RD012-122, of Historic Narrow D&RG and the Atchison, Topeka and Alamosa and Silverton continued in Gauge Railroad Photographs located at the Santa Fe Railway that culminated in the operation into the mid-1960s. In 1967 Friends of the Cumbres and Toltec Scenic Treaty of Boston, which restricted the the Denver and Rio Grande Western Railroad Library in Albuquerque, N.M., and Railroad (D&RGW), successor to the Historic American Engineering Record, HAER D&RG development in New Mexico. No. NM-16, Lobato Bridge, Wolf Creek. Both of these occurrences ultimately D&RG, applied to the Interstate Com - 37 38 APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 45:1, 2014 Some drawings of the original 1881 design have been preserved and were made available. These proved valuable in evaluating the post-fire condition and reconstruction decisions. The Fire Nearly all of the timber ties were con - sumed in the fire, which created great heat at the top of the structure. The rails buckled. The upper flanges of the girders became distorted, buckled, and cracked in numerous places. The upper parts of the girders were raised to higher temperatures than their lower Fig. 2. Bridge arrangement, Lobato Bridge. Sketch by J. R. Harris & Co., Denver. parts, evidenced by discoloration of the paint on the heated surfaces. It is be - lieved that the lower portions of the merce Commission to cease operation feet above the ground. The built-up girders, which were not distressed, and the supporting bents below, sustained on the railroad, except for the Silverton plate girders, which were 49 1/2 inches Branch that runs from Durango to deep, were fabricated from metal plate no permanent damage. However, the Silverton. Operations ceased, and the with continuous angle connections upper portions of the plate girders, the line was abandoned from Antonito to riveted between the web and flange X-bracing, and the top-flange lateral Durango on December 29, 1969. 7 plates. Cover plates were used in the bracing all sustained significant distress On July 1, 1970, the states of Col - mid-span portion of each girder, and X- (Figs. 3 and 4). orado and New Mexico purchased the bracing served as cross bracing between At the north abutment, the bearing line and its associated right-of-way, the girders, located 10 feet apart. Addi - separated, and the girder was observed rolling stock, and real property from the tionally, lateral bracing of steel angles to be about 7 inches above the masonry D&RGW. Currently the line between provided support of the top compression plate. The top of that girder as it cooled Antonito and Chama is operated as the flange. The ties served a two purposes: after the fire contracted sufficiently to Cumbres and Toltec Scenic Railroad to support rails, as with all railroads, develop a negative camber, raising it off based on the Cumbres and Toltec Scenic and, at 15 inches deep, to span the 10 of its bearing. That meant the girder was Railroad Compact that was authorized feet between the parallel girders. Post- now cantilevered from its interior sup - by an act of Congress in 1974 and is still fire examination revealed that the rails port, 54 feet away, significantly stressing its continuity plate in tension. jointly owned by the states of Colorado were offset 2 1/2 inches from the center - and New Mexico. 8 The Cumbres and line between the girders, resulting in The east girder of each span suffered Toltec Scenic Railroad Commission slightly greater loading applied to one more damage than the west girder, manages the railroad. The commission is girder. suggesting that prevailing winds from comprised of four commissioners, two The iron bents, also referred to as the west may have concentrated more from each state. The governors of each trestles, columns, or piers, were fabri - heat on the east side. Spans 1 through 4 state appoint the commissioners. cated from built-up columns of rolled suffered irreparable damage; span 5 channels, connected with lacing bars suffered damage to the top lateral brac - ing but was considered repairable; and The Bridge and batten plates, with two such columns cross-connected with transverse struts span 6 had no apparent damage. At Lobato Bridge was fabricated by the spaced vertically every 30 feet. The bents number 2 and 3, the bolts that Andrew Carnegie’s prolific Keystone bents are not cross-connected to each connect the girders to the bearings were Bridge Company, headquartered in other; rather, the girders of the bridge either sheared off or distorted. Pittsburgh. The D&RG installed the provide all the longitudinal support for Having lost the service of Lobato bridge over Wolf Creek a few miles the structure. At each interior bent and Bridge, CTSRR was forced to temporar - north of Chama, as part of their line at each column, the two adjacent girders ily cease operations from Cumbres Pass across the mountains of northern New use one bearing assembly, which rests on to Chama. Service from Antonito to Mexico and southern Colorado (Figs. 1 a pin. The pin allows for the rotation Cumbres Pass was continued. As the and 2). effects caused by the deflections of the bridge is located only three miles north The six spans — riveted plate girders, girders. The girders have continuity of the Chama terminal, buses were used five measuring 54 feet and one measur - plates at their top flanges that connect to transport passengers from the termi - ing 40 feet totaling 310 feet in length — each span to the next. Thus, the anchor nal at Chama to Cumbres Pass. Still, were supported on stone-masonry abut - bearing at the south abutment offers the publicity affected tourist numbers; ments and iron bents as much as 100 only longitudinal restraint. business and revenues decreased at a FIRE AND RESTORATION AT LOBATO BRIDGE 39 as other elements were found in very small to trace quantities, but the table does report on the elements discussed in this paper. Physical properties were also deter - mined by tensile testing (Table 2). As shown in Table 2, samples 1 and 2 were taken from portions relatively unaf - fected by heat from the fire.