The proposed bridge structure be nearly 500 feet long consisting of four-spans that will accommodate three 12-foot lanes with 4- and 6-foot wide shoulders.  The proposed bridge structure will be located over the footprint of the existing bridge structure with the abutments shifting approximately 30 feet north and 15 feet south with an approximate grade raise of 4-foot along I-25.  The proposed bridge foundations will be supported by driven piles groups driven to the Pierre Shale Formation bedrock 50 to 80 feet below existing grades.  

One challenge associated with the field explorations was obtaining the required railroad right-of-entry permits from both the BNSF and UPRR and maintaining railroad flagging protection at each proposed bridge bent.  Another change was that the proposed bridge abutment walls will be cantilevered and supported by the abutment pile cap.  The existing bridge approach embankments were constructed from fat clay and with the proposed grade raising is suspectable to settlement from the weight of the additional fill and potential down drag onto the proposed piles.  Shannon & Wilson developed a settlement monitoring plan to be implemented prior to driving the bridge abutment piles.