SECTION 252:616-7-6. Soil and bentonite liners

(a)   Suitability. A liner system constructed using an admixture of bentonite with native or imported soils is a moderately protective liner system and may be used to contain compatible Class II, III and V wastewater.

(b)   Pre-construction requirements. Before construction, classify and test all liner material and submit the following with the industrial wastewater treatment permit application:

(1)   test the proposed soil and bentonite mixture for both physical and chemical properties showing the wastewater and liner are compatible;

(2)   measure the hydraulic conductivity of a representative compacted sample using water and actual or synthetic wastewater; and

(3)   use bentonite that is high swelling, free flowing, and has a particle size distribution favorable for uniform application with minimal wind drift effects.

(c)   Construction requirements. Construct a soil and bentonite liner as follows:

(1)   use equipment designed for spreading fine grained soils or bentonite mixtures with minimal wind losses;

(2)   apply one-half of the mixture in one direction and the remaining half perpendicular. Several lifts may be required in each direction to achieve the design thickness of the soil and bentonite liner;

(3)   mix the bentonite into the soil to a uniform depth of at least six inches, unless the soil and bentonite are mixed before application using a pugmill;

(4)   construct within a water content-density range to assure a maximum hydraulic conductivity of 1 x 10^-7cm/sec, verified by an independent soils testing laboratory;

(5)   apply the bentonite in the field at a rate that is at least 125% of the minimum rate determined in laboratory tests needed for stability and maximum hydraulic conductivity;

(6)   test the application rate, water content, density, and hydraulic conductivity of the liner at least twice per lift or per acre;

(7)   protect the liners with at least 12 inches of soil; and

(8)   hydrate the liner before adding wastewater and maintain the moisture content of the liner at or above optimum water content until the surface impoundment is filled.

[Source: Added at 17 Ok Reg 1925, eff 6-12-00]