Thursday, August 30, 2007

Attn Bicyclists: A Letter from Steve Titus, DOT

As posted in the Ester Post Office:

Thank you for contacting me regarding the Department’s recent design change on the bike path from Ester to Fairbanks. Specifically, we decided not to use crushed D-1 aggregate under the asphalt in the bike path. The decision was made after we confirmed that the pavement could be placed on the alluvial gravel material in compliance with our design standards and that the material would provide the structural support and the smooth surface we needed for the path.

The Parks Rehabilitation project includes reconditioning the existing roadway surface by grinding up the existing asphalt and repaving the surface. In the course of construction we encountered areas that required the removal of thick sections of patched pavement. This resulted in a shortage of material and significant overrun of D-1 to be used in the roadway.  

The original design of the bike path embankment called for 3 feet of alluvial gravel, topped by 4 inches of D-1 and 2 inches of pavement. We specified “alluvial” gravel because we were concerned that the locally available “tailings” would not give us the desired drainage. The D-1 layer in bike path design is often included to provide a smooth surface on which to place pavement.

To keep the overrun of D-1 to minimum, we looked at the option of paving the bike path on the alluvial gravel rather than on the pavement. This option was discussed with our Preconstruction section to assure that we were complying with our design standards. Additionally, the option was discussed with our Materials section to affirm that the D-1 layer was not needed for structural purposes. It was determined that the alluvial borrow material was more than sufficient for structural purposes on a bike path and that it would provide a suitable paving surface. In short, the only purpose the D-1 layer served for the bike path portion of the project was for a surface for placing pavement and as an additional and unnecessary structural layer in this project. 

The decision to use the D-1 in the roadway, rather than in the bike path, will result in a savings to the State of approximately $80,000 with no impact on the life expectancy of the facility. Furthermore, the bike trail will be structurally sound and the pavement will be smooth.

In every transportation project, our designs are tested in the field. Occasionally, we modify or change our original plan when faced with real world site conditions. We take every one of these decisions seriously and made these decisions based on the professional advice from our engineering and geologist technical experts. The elimination of the D-1 was just one of those types of decisions and we feel confident that it is a good decision that reduces the fiscal impact to the State. It will allow the Department to spend those fund on other needed projects in the Northern Region.

Thank you again for contacting me regarding this project.

Steve Titus, P.E.
Regional Director

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