Lapeer County Road Commission has a goal to serve Lapeer County by maintaining all county roads, bridges and culverts within the jurisdiction to provide convenience and safety for the public. So when a bridge on Newark Road began deteriorating, they took action.
The existing structure was a 10-foot long by 25-ft. wide castin- place concrete bridge on spread footings built in the 1940’s. A rainstorm in August 2009, consisting of more than 8-inches of rain in a 24-hour time period, produced scour forces that severely undermined the spread footings, weakened the bridge abutments and eventually caused foundation failure.
The structure was heavily damaged and the County was in need of an immediate replacement crossing. As this road was a main route for school buses and for county winter plowing and salting trucks, a fast replacement was essential to minimize road closure time and the impact on the public.
“Because we were at the end of our construction season and we typically receive heavy precipitation during the fall, it was crucial to replace the existing failing bridge in a relatively fast manner,” said William Meinz, P.E., County Highway Engineer with Lapeer County Road Commission.
The bridge was located over a natural stream and the adjacent floodplain was determined to be a regulated wetland. An emergency permit application was submitted to the Michigan Department of Environmental Quality (MDEQ) who regulates the stream crossings and wetlands. Survey work for the permit took place mid October and the MDEQ permit application was approved by the beginning of November.
Lapeer County Road Commission reviewed many options when deciding whether to rehabilitate or replace the structure. The crippled bridge was posted with a 10-ton weight restriction while they considered their alternatives.
One option was to postpone the replacement until the 2010 construction season by either posting the structure with a 10-ton weight limit and performing winter maintenance or by consolidating traffic to the north lane of the bridge where the structure was not undermined and posting a 35-ton weight limit.
Another option was to add a steel spreader beam supported by driven steel H-piles to support the concrete bridge deck and post the structure for 35-tons. This would allow the bridge to remain operational for a few years until a replacement could be planned.
Immediate replacement options – and the two options preferred by the County – included installing either an aluminum box culvert or a concrete box culvert. The aluminum box culvert was the most practical, timely and cost-effective alternative for this small bridge replacement. The concrete box culvert option would be ultimately too expensive and would take 3 to 4 weeks for delivery to the site.
The replacement structure was delivered to the site within 10- days of ordering and Platinum Services assembled 58.5 feet of the aluminum box culvert within a day and a half. Lapeer County Forces then began installation. The wide-span, low-rise shapes were lightweight and fast and easy to install.
“We were pleasantly surprised by how fast the structure was delivered to the site,” said Meinz. “The bridge replacement went without a hitch and the weather held out. Our fast-track project was successful because the culvert was manufactured and delivered to the site within 10 days. Overall the project went very smoothly.”
The aluminum box culvert was delivered to the site on November 13th, installed on the 17th and the road was open again to public on November 20, 2009.
“We are very pleased with the new bridge as well as the installation process. The entire process – including shipping, installation and paving the roadway – took only 3 weeks,” said Rick Pearson, County Manager with Lapeer County Road Commission.