Thursday, February 11, 2016

Understanding the Road Dips in Bellevue

Get your favorite bag of chips and experience the dips of Bellevue... in their road that is.  If you have driven around Bellevue, there are many roads that have a depression settlement crossing the road. Complaints regarding Verlin Road are most common. So why is this? And what is being done to prevent it from happening?

The majority of the settlements within the roadway are the result of the utility installations from years past.  Talk to many contractors that have worked in Bellevue and they will tell you that the soils are difficult to work with.  The conditions can change every 50 feet and uniform compaction is difficult to achieve as a result.  If you don't add enough water, it is like trying to compact concrete.  If you add too much water, it is like compacting soup. It does not take a lot of moisture to go from one extreme to the next.

Many of the dips have settled as a result of years of moisture and traffic traveling through and over the trench area.  It is very difficult to achieve the same compaction as the surrounding soil, but eventually it does happen. The surface asphalt is flexible enough to conform to the dip.  Many concrete roads have the same condition, but it is not noticeable because the concrete will bridge the settlement.  Over time even the concrete will crack and settle over the depression.  Typically when roads are resurfaced, the utility trenches have been compacted for 25+ years and can be filled in with little chance of additional settlement.  This is one of the unfortunate features of Bellevue.  In extreme cases, the depressions are filled in with patch asphalt.

The Village has taken steps to reduce the settlement chances through new utility trenches by specifying granular backfill within the roadway and additional compaction testing.  The uniformity of the backfill material allows the contractor to better achieve consistent compaction results.  There are no guarantees that there will never be settlement in the roadways, but these methods do reduce the chances of it happening.