How will the solid materials handling facility be constructed to prevent infiltration to groundwater?
To protect the environment and to ensure that the stored ash will not impact the ground or surface water, Plant Washington’s ash will be managed in a solid materials handling facility very similar in design and construction to a federally-regulated municipal solid waste storage facility. The Plant Washington dry ash storage facility will include the following protective measures: • A two-layer composite liner will be constructed at the storage facility to prevent percolation of water through the stored materials to the underlying groundwater. • The first layer will be approximately two feet thick and comprised of compacted soil, synthetic clay materials and a non-permeable synthetic flexible membrane. • The second layer, underlying the non-permeable membrane, will consist of cohesive soil (clay) also two feet thick. • Above this four-foot-thick synthetic barrier will be a two-foot-thick drainage layer with an integrated sump and water collection system to remove any free water (i.e. ra
