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 were also installed.
A thick cushioning fabric, known as geotextile, was 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 was placed over the installed liner. Additionally, 12 inches of fill material was 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 was a rigorous quality assurance/quality control procedure and stringent project installation specifications which must be adhered to. Extensive field and laboratory testing were performed during construction to ensure all quality requirements are met (i.e. geomembrane strength and thickness, seam strength and integrity). The construction contractor hired an independent specialty inspection firm to conduct liner monitoring and testing. The United States Army Corps of Engineers Philadelphia District (CENAP) also inspected the liner construction components (10% of the seams) via their own hired firm. The liner is designed to be impenetrable, including roots; however, 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