1. (b) A drainage layer constructed of either a soil layer or geosynthetic drainage layer must be installed between the barrier layer and the barrier protection layer unless stability analysis meeting the requirements of section 363-4.3(c)(3)(iv) of this Part indicates that a drainage layer is not required. If a geosynthetic drainage layer is utilized, it must be designed and constructed in accordance with the requirements in section 363-6.12 of this Subpart.

A barrier protection layer must be constructed in accordance with the provisions of this section. The barrier protection layer must protect the geomembrane barrier layer from root penetration, be stable for the specified slopes and resist erosion.

(a) Construction requirements.

The barrier protection layer, including any drainage layer, must consist of a minimum of 12 inches of soil where cool season vegetation is specified or a minimum of 18 inches of soil where warm season vegetation is specified. One hundred percent of the soil used to construct the lower six inches of this layer must pass a two-inch sieve.