Interstate 680 is an important traffic corridor located north of Council Bluffs, IA. A key section of this interstate connects I-80 in Nebraska with I-29 in Iowa and crosses the Missouri River via the Mormon Bridge. The route serves as a northern bypass of Omaha, NE and Council Bluffs, IA and provides critical access to the Omaha airport.
Much of the upper Missouri River Basin received heavy snowfall over the course of the 2010/11 winter months. As the snowpack began to melt, the overland flow was higher than the normal amount of winter runoff. Around 8 inches of rain also fell on May 23, 2011, in the upper reaches of the basin. This caused the worst flood event on record along the Missouri River which resulted in severe damage to I-680 east of the Mormon Bridge. The majority of the pavement in the area was completely destroyed and what remained intact showed signs of flood water erosion.
The prime contractor, Peterson Contractors, Inc., entrusted Snyder & Associates to perform design and construction staking on this vital link between Nebraska and Iowa while they took on the challenge of rebuilding the flood-ravaged interstate highway in less than three months. Our scope of work included limited topographic survey, formulation of a stormwater pollution prevention plan and NPDES permitting, design, construction staking, and record drawings. The Iowa DOT provided an alignment and vertical profile of the roadway based on their records. Much of this information needed to be modified to match actual field conditions. Pavement design and typical sections were also provided by the Iowa DOT.
Since flood waters destroyed most of the existing pavement, a full topographic survey was not performed on the corridor. A limited survey was obtained on the pavement that remained intact (and in good condition) where the new pavement would match in. A field survey was also obtained on the alignment monuments that remained to aid in establishing the centerline shortly after the project was awarded. One of the more challenging aspects was to provide a design that matched the original roadway while upgrading the facility’s geometry to current standards. This was especially challenging on interchange entry and exit ramps.
With limited topographic survey obtained along with LiDAR surfacing and 35-year-old record drawings, the Snyder & Associates team recreated the horizontal and vertical control, designed the roadway, generated 3D stakeless grading files for each phase of construction, and staked the entire corridor for drainage and paving in just over three weeks.