The design of overlay projects at GA airports is contracted out to private engineering firms. Current designs do not incorporate Falling Weight Deflectometer data due to inconsistencies caused by the extremely thin HMA overlays used on GA airports. The binder specified in the design is often deviated from due to contractors inability to obtain the specified binder from asphalt suppliers or lack of storage for small quantities of specialized binder. Currently the FAA is very restrictive on the asphalt emulsions used as maintenance treatments and does not allow the use of chip seals.
Advances in materials and design could potentially extend the useful life of GA runways. Binder specifications need to be enforced without allowing contractors to deviate from the binder specified. Numerous HMA surface treatments could also be used to extend surface life and maintain an acceptable skid resistance. Some of the surface treatments available are chip seal design using the new SDDOT chip specification and polymer-modified emulsion, macro seal, micro surfacing, and slurry seal. The last three listed surface treatments have previously been tested on airports in others states and have showed very promising results in extending the service life of HMA surfaces. Comparing two or three of these treatments to the current coal tar pitch emulsion on GA runways in South Dakota would provide information on which treatment is the most cost effective and has the best aggregate retention.