Geosynthetics Group team to jointly brainstorm solutions that may be incorporated to overcome the project challenges and to make the required repairs that would solve the erosion problems. This team quickly arrived at a potential innovative geosynthetic solution that would meet all the challenges and could be rapidly executed. The solution called for an underwater cofferdam to be installed adjacent to the base of the concrete structures under which erosion scour was occurring. The cofferdam would be formed using 65-cubic-yard (50-m3) sand-filled geotextile bag containers weighing 99 tons (90 tonnes) (Figure 3). The individual geotextile bag units would be flexible enough to conform to the irregular eroded bottom of the canal, yet they would be massive enough to withstand the prop wash of the tugs and high velocity of the water flowing out of the canal locks underneath the Panamax-size ships. In addition, the geotextile bag structure would provide a 7-foot (2-m) thick × 16-foot (5-m) wide erosion control mattress along the base of the entry slab and on either side of the canal entry dividing wall. The geotextile bag containers would be prefilled at an off-site location and transferred to the Gatun Locks where a 386-ton (350-tonne) barge-mounted crane would lift and place them to form a 13-foot (4-m) high × 16-foot (5-m) wide × 98-foot (30-m) long cofferdam. Once the cofferdam was constructed, concrete would be pumped behind the cofferdam and underneath the entry slab to fill the eroded void. This two-step process would be performed during successive scheduled 12-hour maintenance windows. TenCate had previously developed and tested the full-scale system of filling, lifting and placing 65 cubic yards (50 m 3) of sand-filled geotextile bag containers, which weighed 99 tons (90 tonnes). The bags were fabricated from FIGURE 4 Filling geotextile bag containers at off-site location a 1,142-pounds-per-inch (200-kN/m) woven polypropylene geotextile in a 16-foot (5-m) wide × 16-foot (5-m) long × 7-foot (2-m) high configuration. The bag had a top lid that was open for filling with sand and could be closed and mechanically sealed to permanently contain the sand. A unique 2,284-pounds-per-inch (400-kN/m) friction geogrid harness was designed and full-scale tested to provide the flexible system of lifting and placing. The ACP determined that the geotextile bag system provided the required factors of safety and met its criteria to repair the Gatun Locks on the Atlantic side during the 12-hour maintenance window without disrupting the canal operations. The operation The ACP resolved that the off-site geotextile bag-filling operation would be conducted at its maintenance dock facility adjacent to the canal near the Gaillard Cut, 32 miles (51 km) from the Gatun Locks (Figure 4). The ACP Titan The ACP determined that the geotextile bag system provided the required factors of safety and met its criteria to repair the Gatun Locks on the Atlantic side during the 12-hour maintenance window without disrupting the canal operations. www.GeosyntheticsMagazine.com 0820GS_p14-19.indd 17 17 7/22/20 4:54 PMhttp://www.GeosyntheticsMagazine.com