Spring ’17 MCCD Dirt and Gravel DSA Demo Day
In Fall of 2016, Tobyhanna Township placed nearly 900 tons of Driving Surface Aggregate (DSA) on Gordon Lane, a township owned road parallel to Interstate 80. DSA is a specified mixture of stone aggregate designed as a wearing course for gravel roads. Unlike 2A, a commonly used driveway stone, which is actually a drainage aggregate, DSA contains more medium and fine particles which enables it to compact better. DSA forms a hard driving surface similar to concrete, with benefits like reduced dust generation, reduced loss of fines from water transport, and longer maintenance intervals. Unfortunately, the placement was done late in the season, and the material delivered was too wet, and was never able to dry properly. This resulted in a rutted surface once winter hit. The township added 2B stone to the top to stabilize the road over the winter.
Purpose and Process of the Demonstration
In order to correct the rutting and remix the DSA in place, a power rake box (PRB, a.k.a. rock hound or Harley Rake) was employed to loosen and remix the upper surface of the aggregate. First as much 2B as possible was removed with a loader. Then the PRB was run, using caution not to remove the road crown. The DSA was then re-compacted using the required 10 ton roller. This process was repeated following the first run. We received 0.2” of rain two days before the workshop, which provided moisture content necessary to compact the aggregate properly.
The demonstration purpose was two-fold: to show the benefits and limitations of the PBR for maintaining DSA, and to determine if overly wetted aggregate could be repaired using the PRB.
The PRB was able to remove the top 3” of aggregate and remix it in place. This was sufficient to remove the embedded ruts in the road surface. The DSA compacted well in areas without excess 2B intermingled with the aggregate. While the DSA surfaced areas were solid, the clusters of 2B, evident in the completed photos, will probably result in potholes when they pop out. Overall the surface is approximately 85% corrected. If the 2B could have been more completely removed, which was made difficult by the underlying ruts, the surface may be 100% corrected. We will continue to monitor the performance of the road and may employ a more substantial method next spring- a grader with a stinger blade, which will be able to cut more deeply, and turn the aggregate over, better diluting the excess 2B now mixed in with the surface layer. Stay tuned for more.
Questions can be directed to John Motz, Resource Conservation Specialist at MCCD- 570-629-3060.
Thanks to the Townships of Tobyhanna and Middle Smithfield for the use of their equipment and operators. We had 15 participants from three municipalities, and the District Manager from MCCD in attendance. Funding was provided through the MCCD Dirt Gravel and Low Volume Road Program for the Demo Day.
Spring ’17 MCCD Dirt and Gravel DSA Demo Day Media Gallery