The document referenced pertains to construction of earthen-lined storage to minimize liquid infiltration. This reference has valuable information for determining if local soils are appropriate for construction of a settling basin. The reference has modest value in vegetative treatment areas (VTA) and vegetative infiltration basins (VIB), both of which are designed to encourage moderate infiltration rates.
The value of a liner in a settling basin is debatable. Settling basins should be designed to maintain shallow depths, possibly no more than 3 feet. Thus, the driving force for seepage is small. Settling basins should be maintained dry except for a few days after a precipitation event and possibly during periods of frozen soils. These situations should not cause significant seepage.
Of greatest value in Appendix 10D is the discussion of soil types and other siting conditions. These are directly applicable to settling basins. Group III soils (e.g., CL or CH unified classification) have low permeability and low to moderate shrink-swell characteristics, making them preferred for settling basins.
Chapter 4 of the NRCS collaborative report on Vegetative Treatment Systems for Open Lot Runoff further discusses siting considerations.
Author: Rick Koelsch, University of Nebraska
