At the nature center where I work we have a 1/3 mile long boardwalk that winds through a forested area and a mangrove swamp. There are sections where there are slight dips and rises. These areas are periodically treated by spraying with an adhesive to which a light coating of fine sand is applied. This method virtually eliminates the possibility that someone might slip on the boardwalk when it's wet (which is most of the time, here in south Florida). If you'd like the name of the adhesive we're using I could find out for you. BTW, have you considered recycled plastic composite "lumber"? It's in use at another park in the city where I work; it's attractive, splinter-free and doesn't warp. Rhea Tannenbaum Exhibits Coordinator Gumbo Limbo Nature Center Boca Raton, FL [log in to unmask] ____ RheaT