April 20, 2011 Sandbagging 101 Sandbagging is a seasonal ritual in flood-prone cities and towns. In places like Fargo, N.D., up to 3 million bags are filled, readied and made into levees according to methods developed for saving lives, homes and property. Here's a took at how it's done. , @ Sandbags Most sandbags are made of woven polypropylene and are 14 in, (35.5 cm) wide and perhaps 2 ft. (61 cm) deep; they're usually filled about halfway with sand or clay and tied or stapled; they weigh about 35 lb. (16 kg) @ Site prep Site preparation begins with scraping away ice, snowand topsoil, if possible; a shallow trench sometimes helps hold the levee in place 1 bag deep, two wide @ Filling bags It usually takes two people to fill one sandbag; crews often use funnels (like the one shown), but mass production sometimes involves conveyors and chutes Levees are usually built at least a foot (30 cm) higher than the predicted crest Construction ratios The U.S. Army Corps of Engineers recommends that a levee have a base three times wider than its height; other sources say a 1:2 ratio is adequate for a solid levee. Bags are staggered, like bricks in a wall; the water's weight helps hold a levee in place @ Watertight Plastic sheets are often wrapped under and over levees to prevent seepage Floodwater 10' (305 cm) NOTE: Ftoodwater is poHutod, so used sandbags are considered contaminated • 2011 MCT Source: North Dakota State Extension Service and the US Army Corps of Engineers, St Paul Graphic: Mark BosweH, Minneapolis Star Tribune 51