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ENVIRONMENTAL CONSTRUCTION AND REMEDIATION Air Sparging Trench Installation The project included the construction of an air sparging trench at the Colonial Pipeline Company Winder Leaksite in Winder, GA. At the site, contaminants are present as a result of a gasoline spill in soils and ground water as well as an adjacent stream. The system objective was to remove dissolved-hydrocarbon constituents to levels that adhere to Georgia stream water quality standards. The project consisted of excavating a trench via the Bio-Polymer method. The trench was 250 lineal feet, with a maximum depth of 20 feet and a width of 30 inches. The Bio-Polymer Slurry Drainage Trench method is a modified version of the slurry trench technique, which permits the construction of deep and narrow trenches supported only by an engineered fluid or slurry. The air sparging system consisted of ten inverted "T" sections of piping placed at 50 ft intervals. Each 50-ft interval consisted of a primary system, placed at a depth of 20 ft, and a secondary system, placed at a depth of 10 ft. The 50 ft section was held in suspension with pre-measured cables, which were attached to wooden blocks at the ground surface. Once all pipes were placed in the trench, the trench was then backfilled with #57 stone to a depth of 6-12 inches below ground surface. Efforts were made to carefully place the stone in the trench to ensure the secondary piping system was not interfered with or damaged.
Trench development began immediately upon the completion of the backfill process. Complete trench development/slurry degradation was accomplished by recirculating the trench fluids over the surface of the trench until the slurry was completely degraded. Geotextile was then placed on top of the # 57 stone and the remaining portion above the trench was backfilled with natural soils. A secondary trench was also excavated to a depth of 2 feet below ground surface and extended from the equipment compound to the air sparging trench. A solid 4-inch HDPE pipe was placed in the trench, connecting the air sparging manifold piping to the equipment compound. The secondary trench was then backfilled with clean native soil.
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