The Dredged Material Containment Facility (DMCF) is treated as a landfill in terms of construction specifications, and the first step of liner installation involved clearing the existing vegetation within the DMCF, re-grading the existing perimeter dikes to an elevation of 50 feet (ft.), and increasing dike stability. New steel sluice boxes and associated pipelines will be installed as well.
A thick cushioning fabric, known as geotextile, is being placed over the improved subgrade to protect the liner from puncture. The geomembrane (plastic liner) will be placed on top of the geotextile fabric and then another thick cushioning fabric will overlay the installed liner. There will also be 12 inches of fill material placed over the liner system for further protection. The particular geotextile material being used for the Pearce Creek DMCF can elongate five times its length without breaking, which is beneficial when dealing with differential settlement. The liner sections are 22 foot rolls that are 750 feet long which are heat welded together to incorporate the whole area.
Upon installation there is a rigorous quality assurance/quality control procedure and stringent project installation specifications which must be adhered to. Extensive field and laboratory testing will also be performed during construction to ensure all quality requirements are met (i.e. geomembrane strength and thickness, seam strength and integrity). The construction contractor has hired an independent specialty inspection firm to conduct liner monitoring and testing. The United States Army Corps of Engineers (USACE) will also inspect the liner construction components (10% of the seams) via their own hired firm. The liner is designed to be impenetrable but spraying herbicide on the liner and other continued maintenance efforts will prevent more mature growth.
The aerial images below show the progress of the liner construction:
Site Aerial - May 2016
Site Aerial - June 2016
Site Aerial - July 2016
Site Aerial - August 2016
Site Aerial - October 2016
Site Aerial - November 2016
Site Aerial - January 2017