The vertical setback is the distance measured from the bottom of dispersal trench to the seasonal high groundwater level, fractured rock, or other limiting layer. Soil textural classification should be considered the primary data source for system sizing. Percolation tests may be allowed or required to supplement soil textural classification. When determining soil textural classification, the least permeable layer below the point of dispersal shall be used in determining the vertical setback. Minimum vertical setback distances are provided in the Manual.
Where supplemental system is utilized, minimum vertical setback may be reduced from the requirements that apply to standard systems as provided in the Manual.
(Ord. 1469, eff. July 14, 2016)