If water can get in, then enough air can get in as well. The best thing is to dry the area, and eliminate the opportunity for water to enter again. My experience is that mold will grow anywhere it can find moisture and food.(wood, paper, any organic material) Boric acid is an excellent mold killer, if you can get it to the affected area. Sounds like the long term solution is going to be regrading the uphill side, so the water cannot build up. Obviously the drainage system you designed requires someone to give a crap about maintaining it, which seems to be lacking with the current owners. Every house I have built into hillsides (4) was graded in such a way as to channel water coming off the hillside around the house, in addition to having a french drain with perforated pipe buried around the foundation. Gutters also need to carry all the water away from the uphill side of the house.

The only cure for mold is to remove the water.

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On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

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