We had some log benches made for a park I am in charge of, they were made of ash from trees cut down in the park , after completion {5 months after trees were felled}they developed deep cracks which we expected but the bottom were people will sit has a fairly large crack full 7 feet of length. I am concerned this will hold water and freeze and open up crack further and cause rot. What would be the best solution to deal with this? Should we try to fill and if so what kind of filler should we use?