Asphalt/Storm Drain Remediation Do’s and Don’ts

Asphalt/Storm Drain Remediation Do’s and Don’ts

Your community’s roads, parking lots, and driveways are one of the most (if not the most) expensive assets they have.  The asphaltic pavement that comprises those surfaces has an anticipated life expectancy of 25 to 27 years.  The actual duration of your pavement surface (whether shortened or lengthened) is directly related to how well it is designed (in terms of release of storm water and traffic load design), constructed (installed per design specifications), and maintained (ongoing maintenance).  Assuming that the first two components are completed correctly, then your ongoing maintenance procedures will play anexclusive role in the overall life of your pavement surfaces.

Common examples of normal ongoing wear of pavements are:

  • Thermal shrinkage cracking.  Asphalt contains a large amount of emulsion and oil.  This is what provides its flexibility to handle traffic loads.  Heat, weather (rain, snow, etc.), and traffic work to remove these products from the pavement surface.  Thusly, making your pavement shrink.  Unlike concrete, asphalt (when originally applied) does not have “tooled joints” or “cold joints” to allow the shrinkage cracks a place to harbor.  Therefore, as your pavement surface loses oil content and starts to shrink, “thermal cracking” will appear at the pavements “weakest” locations.  These areas would be at paving “seams” where the paving machine applies the product in rows, the seam between the rows “shrinks” away from each other, around utility covers (manholes, water valves, etc.) where these covers are lowered for paving and subsequently “raised” once paving is complete, the pavement is “patched” once the utility is raised provided a “seam” between the asphalt surface and the pavement patch around the utility, or even corners where rolling patterns have difficulty providing uniform density.  These cracks start as “hairline” cracks and can overtime reach widths of 3” to 4”.

  • Grey discoloration of pavement surface and exposure of asphalt aggregates in the pavement surface.  As asphalt ages and loses its oil content, it will lose its rich black color and lighten to grey. In addition, with weather, and as surface oil, emulsion, and fines (sand) leaves the pavement, the “coarser aggregates” are more prominent in the pavement’s surface.  These aggregates have always been at the surface; however, the oil, emulsion, and fines camouflage the majority of this aggregate.  As this occurs, it is the indicator that your pavement needs attention.

Signs of abnormal pavement failure are:

  • Ponding of water at that pavement surface.  Your pavement surface was not designed to “store” water.  On the contrary, water is designed to be released off of asphalt via “in pavement” conveyance systems like catch basins or drywells or “off pavement” conveyance like spillways to retention basins.  It is often believed that water that sits on the pavement surface eventually evaporates into the atmosphere.  This is true to a degree.  However, it can be expected that an equal amount of surface water percolates into the pavement sub grade as that which evaporates into our atmosphere.  This percolation can and does create unstable structural integrity in the underlying sub soils and consequently cause pavement to move and crack.  This can be severe and is commonly seen in “reflective” cracking or “alligator” cracking.  The old saying “oil and water” do not mix is appropriate in asphalt as well.  Pavement ages more rapidly when water is introduced to it on a regular basis.

  • Alligator cracking and vertical undulation of the pavement surface are strong indicators of poor sub grade condition.  Repair of these areas should always include the examination of the sub grade beneath the aggregate base course that underlies your pavement.  Wet or unstable grade should be reconstructed to provide a dry firm and compacted base prior to replacement of aggregate and subsequent asphalt surfacing.

  • “Tearing” of asphalt.  Tearing is a term where the pavement is cracking immediately adjacent to an unconfined edge and there is evidence of cracking that is running parallel to that edge.  All asphalt edges should be confined is some fashion.  This can be accomplished with curb, another type of “hardscape” surface, or even a “thickened asphalt edge”.  All cracking allows water to penetrate beneath the pavement surface and potentially damage the sub grade beneath.  Tearing of asphalt adjacent to an unconfined edge will not only allow the permeation of water, it will also continue to separate and the pavement condition will deteriorate rapidly.

So here are some dos and don’ts for you to remember when evaluating your pavement’s needs:

Do’s-

  • Keep thermal cracks filled.

  • Evaluate the oils, emulsions, and fines in your pavement surface.  When you see significant loss and discoloration, it is time to seal coat your pavement.

  • Have an ongoing seal coat program.  The “rule of thumb” should be every 3 to 5 years depending on usage.  Not all seal coat products are appropriate for all applications.  Depending on the age and condition of your pavement surface, there is a seal coat product on the market that can provide appropriate relief.  You can spend too much money applying an unnecessary product on your pavement surface and you can also apply an inappropriate product that will not provide the coverage or protection you need as well.

  • Make sure your storm drainage is exiting the pavement and not storing on it.  This includes the proper ongoing maintenance of landscape common areas that border your pavement designed to accept this run off.  The top of your landscape should not be higher than the elevation of the pavement or spillway immediately adjacent to it.  Keep your catch basin inlets and adjacent storm pipe clean and free of sediment and debris.

  • Have a maintenance plan and budget created to implement strategic crack filling and seal coating to ensure maximum life expectancy of your asphalt surface.

Don’ts

  • Allow water to stand on pavement surfaces for more than a couple of hours.  If ponding occurs beyond that, you can assure yourself that stormwater is percolating into the sub grade below.

  • Let asphalt go too long without a proper crack fill and seal coat application.  When asphalt becomes too brittle and there is evidence of alligator cracking, the cost of remediation goes up exponentially.

  • Put too much credence in “reserve studies”.  Reserve studies are great for a “general” plan of attack; however, they are based on averages and not engineering fact.  As stated previously, no two pavements are the same; and as such, should not be treated by “average” industry standards.  Create a concise specific plan to address your pavement needs.

Understanding the “normal” versus “abnormal” indicators will help define your maintenance needs for each community.  No two communities are the same.  Each one should be reviewed on its own merit.  When in doubt, hire a professional to assist you in determining the best solutions for your pavement surface.  Proper care will ultimately provide the longest life of your very costly pavement asset.

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