What can be done when settlement causes a 200,000-gallon concrete pool to crack and leak? Because cracks in the penguin pool at Boston's New England Aquarium were still active due to continuing settlement, patching had been ineffective. Many other repair methods investigated involved noise, dust, drilling or toxic fumes, all of which would disrupt museum operations for up to three months. A solution was found when the museum's technical staff decided to install a plastic liner of high density polyethylene. Elongation properties of the 100-mil-thick polyethylene sheet permitted it to be laid directly over the cracked concrete. Sheets were fastened to the concrete only near the top of the sidewalls where anchors embedded in the concrete supported them. A one-inch slit in the sidewall sheet was fitted over the anchor at these locations to permit movement. Then the flooring sheet was brought up to the sidewall sheet and joined to it using a patented hand-held extrusion welder.