Perhaps he just has a different interpretation for the "SL" portion of his entries; some possibilities:

saw log

sawed log <- any fresh cut wood nearby?

sold log <- not likely since they appear to still be there

smooched log <- Ewwwww!

signed lightly

sighted legumes <- not likely at every cache

surfed LaJolla <- perhaps a crowning moment in his life

Tim
Team AZFastFeet (headed for the last page of the stats!)