Posted: 29/08/2014 at 09:57
Normally I wouldn't specially recommend them for a long time, but how about some Goretex shoes, maybe coupled with some shortie gaiters if there's a lot of wet long grass. IME over a lot of trips the goretex membrane will keep your feet dry for a few hundred k but eventually it starts leaking where the upper creases, long before the shoe wears out.
Looking on a single trip basis, it becomes a toss-up whether the membrane keeps more sweat in than it keeps water out, but given the length of the trip you propose, it could be worth it. I'd change into something else at work and let them air-dry somewhere, possibly with a boot dryer if you will do this even on rainy days.