To make certain that the backfill material is more pervious than the soil to be drained, the relationship used in« Back to Previous Page

A. (D15)Filter ≤ 5 (D85)Protected soil B. (D15)Filter ≥ 5 (D85)Protected soil C. (D15)Filter ≥ 5 (D15)Protected soil D. (D15)Filter ≤ 5 (D15)Protected soil

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