Well, as no translators seem formally qualified here, I just want to comment on the term suggestions made. I think the professional term in this context is "drenerende" or "drenering(s)", combined with a context dependent word, like "overflate". I don't feel a direct word translation of "pervious" will work, we need to use the context specific expression here. I would advise to check out SFT material, like this guide:
http://www.sft.no/publikasjoner/avfall/1951/ta1951.pdf, where "drenering" is used in many combinations and variants for the issue in question.
The translation workplace 
peer agreement (net): +2
