MIL-HDBK-1005/16
Also consult EPA's Municipal Wastewater Lagoon Study: Report to
Congress for discussion and design guidance on minimizing seepage
(0.021 gpd/sq ft [0.86 Lpd/sq m]) for domestic wastewater
lagoons. Industrial waste impoundments may require lower seepage
rates or a double liner for redundancy.
7.7.1
Bentonite Admixtures. Bentonite is a sodium-type
montmorillonite clay that exhibits a degree of swelling,
imperviousness, and low stability in the presence of water.
It can be applied as a water slurry and incorporated with in-situ
soils or as a sand-bentonite slurry (8:1 volume ratio) that is
subsequently covered with soil.
a) Organic polyelectrolytes can be mixed with
bentonite and soil to decrease the permeability of the admixture.
Contact bentonite suppliers for further information and test
procedures.
b) The performance of bentonite linings is greatly
affected by the quality of the bentonite. Bentonite
characteristics that should be specified in preparation of
admixtures include sodium exchange capacity (SAR); percent of
silt, sand, and clay impurities; moisture content; particle size;
and gradation.
c) Determine the required amount of bentonite in the
bentonite-soil by using mixture based on field soil sampling and
laboratory tests by sealant suppliers. Use Figure 24 for
guidance only and for reviewing laboratory results.
7.7.2
Asphalt and Cement Linings. Asphalt linings may be
composed of asphalt or a prefabricated asphalt with or without
admixtures (bentonite or fiberglass). Soil cement sealant is
best when used with sandy, well-graded soil. Avoid using
bentonite and asphalt liners in areas with high weed growth.
7.7.3
Thin Membrane Liners. These liners include plastic and
elastomeric membranes and are best used for sites requiring
essentially zero permeability. For further information, see
FED MCD-54, Wastewater Stabilization Pond Linings. Refer to
EPA SW-870, Lining of Waste Impoundment and Disposal Facilities,
for a listing of membrane suppliers and details of construction.
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