The completion date for the South Third Avenue rebuild will be delayed after crews tore up the road and discovered clay so thick they had to use another piece of construction equipment to pull a motor grader free from its grasp.
Bruce Campbell, assistant city engineer, updated the Marshalltown City Council Monday, saying the road was built directly atop dirt. Over the years, moisture seeped through cracks in the pavement and created roughly 2 feet of clay the consistency of pudding, Campbell said.
"It's nothing but guck," he said. "Those waters would get into the soil and not go anywhere it just soaks up the water and doesn't allow it to go anywhere."
A motor grader is shown here stuck in the mud on South Third Avenue May 17. Laying a geo grid atop the clay to ensure the road has a strong foundation will add roughly $50,000 and a week to the road’s rebuild.
ConStruct Inc., the company doing the rebuild, has already cored out 18 inches of the clay, but crews have to stop somewhere, Campbell said. The only viable option is to lay a geogrid over the top, line the plastic polymer with rock and build the road on that, he said.
Adam Daters, project manager with Clapsaddle Garber Associates, said once the geogrid stabilizes the road, construction can proceed normally. A change order in the amount of roughly $50,000 will be needed to fund the addition.
However, Campbell said because bids for several road projects came in under the engineer's estimate earlier this year, the city can afford the change order, and it will not put the city over the amount budgeted for road work this year.
Crews originally had 60 calendar days to complete the rebuild, but Daters said the setback could add another week or more to the project's completion date. He said the change order takes into account how much clay crews have already encountered as well how much CGA anticipates encountering on the remaining stretch of street being rebuilt.
Campbell said clay is of the same sort crews encountered on Nicholas Drive. So far, crews have found 250 lineal feet of the clay.
Dealing with the material is difficult, Daters said.
"This isn't even really mud," he said. "It doesn't even dry out."
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