simulating a crackplane in soil?

jemteo

i'm trying to simulate a crackplane within my flowdomain how should i approach this?

_________ _1_ __________ | | | | |<- inlet | | outlet ->| ---------------------

for example in my flow domain (illustrated above as best as i can) i sectioned the middle portion (sub-domain) to be my crack plane. the middle section has a different permeability value than the rest of the domain.

what kind of boundary to i place at '1'? outlet? opening? I'm using outlet with static pressure = 0 Pa, is this right?