1999 Chevrolet Venture Park Under Tree Every Day Cowl Vent Drain Clogged Leaks

I park under a tree every day. The cowl vent drain has clogged and leaks water in the van on my floors, and there are puddles under the front tires pretty much every day. The mechanic I took it to says the only way to clean the drains out, is to remove the hood, cowl, and both fenders at an expensive labor rate. I tend to believe there should be an easier way. Is there?