Thanks for the responses. My problem is relating that to the EPA !.
We have a spec of 10-9 in the clay barrier, but I have 10-8 materials - so how do I convince them that we can construct a cap with the same rate of infiltration from rainfall ?. Do we increase then depth ?
Question - I have to design a 0.5m thick cap on a waste rock dump. Criteria is 10-9. My materials are 10-8 What extra thinned do I need to meet same infiltration rate ?