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~ . ~ tc' ~ f ~ 12~06. Construction agency. the Las Animas Valley Branch constr~ted by the owner 0 Alterations of the Arkansas River Bridge on of the AT&SF Railway would be designed and 12-07. Views of a~ers. The Chief Engineer's Office of the Eastern Lines Division, AT&SF w~s contacted in connection with the relocation of their facilities. The owner had no objection to the proposed relocation. They stated that the traffic over the line consisted of several trains per week varying with the season. They also stated that during construction it may be possible to use the crossing at Lamar, Colorado or construct temporary falsework at the bridge site. 12~08. Legal ~bligations of the Government for relocations. obligations of the Government for relocation or alteration of ties are presented in the Attorney's Report, Appendix C. The legal the facili- 12-09. Extent of surveys and investigations. Surveys and investigations conducted in connection with the relocation consisted of reconnaissance surveys of the existing railway bridge and discussions with the owner. As-built plans of the existing bridge were obtained from the owner. 12010. Flood damages under existing conditions. During the June 1921 flood the four bents of the north pile bent portion of the bridge were washed out and thirteen be~ts of the south pile bent POrtion were under- mined and shifted. Ten thousand cubic yards of emba~nt were washed out along the branch line. During the flood of May 1936 there was minor damage to the approach embankment to the bridge. Several thousand cubic yards of the approach embankment were washed out in the May 1955 flood. In 1929, the owner raised the bridge four and one~half feet. 12.ll. Description of existing AT&sF facilities. The existing railroad bridge runs in a north-south direction over the Arkansas River near the town of Las Animas in Colorado. The existing bridge is made up of wood trestles for the end spans and is supported by a pair of 9-foot deep steel plate girder~ about a 415 feet length comprising four spans at the interior of the bridge. The interior spans are supported by concrete piers. An open wood deck is used thro~ghout the length of the bridge. Photographs in Appendix B show the bridge. " l2-12. Proposed bridge alteration. Three methods of altering the exist- ing bridge were compared on a first cost basis as follows: a. Deck Support: 4 std. rolled beams. X-Bracing: At ends and 1/3 span points. Sway Bracing: Both ends and 1/3 span panels. Piers: Extend present piers, install new piers at 1/2 points between present piers and 2 new piers so~th of last existing pier. L 38