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J <br />s_ W :A� -*-- -- - - <br />1. Sealing the dik <br />force against the dike. Estimate the pressure on the dike <br />base by multiplying the water depth by 62 pounds. For <br />example, the pressure that 5 feet of water exerts on the <br />base of a dike is about 310 pounds per square foot. The <br />force of 5 feet of water on a vertical wall is about 775 <br />pounds per linear foot of wall. Flowing water striking <br />the dike exerts even more force on the dike. A triangular - <br />shaped dike permits the weight of the water to push <br />down on the dike to help hold it in place. <br />S Sealing the Dike <br />The finished dike should be sealed with a sheet of <br />plastic to improve water tightness. Spread a layer of <br />soil or sand 1 inch deep and about 1 foot wide along the <br />bottom of the dike on the water side. Lay polyethylene <br />plastic sheeting so the bottom extends 1 foot beyond the <br />bottom edge of the dike over the loose soil or sand. The <br />upper edge should extend over the top of the dike. Poly <br />sheeting at least 6 mils thick is preferred. It generally <br />is available in 100-foot rolls from construction supply <br />firms, lumberyards and farm stores. Do not put plastic <br />sheeting under the bags since that will increase the <br />potential for the dike to slide. <br />If more than one sheet of plastic is used, the poly <br />sheeting should be placed from downstream to upstream <br />and the next sheet upstream overlapped by at least 3 <br />feet. Overlapping in this direction prevents the current <br />from flowing under the overlap and tearing the poly <br />loose. <br />Lay the plastic sheeting down very loosely. The pressure <br />of the water will make the plastic conform easily to the <br />sandbag surface. If the plastic is stretched too tightly, the <br />water force could puncture it. Place a row of sandbags <br />on the bottom edge of the plastic to form a watertight <br />seal along the water side. Place sandbags to hold down <br />the top edge of the plastic. Avoid puncturing the plastic <br />with sharp objects or by walking on it. <br />0' Controlling Seepage <br />Use a sump or skimmer pump to remove water that <br />permeates through the dike. Use ground fault circuit <br />interrupters on circuits or extension cords to reduce the <br />risk of electrocution. <br />F Disposing of Used Sand <br />Floodwater is generally considered as polluted, so sand <br />from bags exposed to flood water should not be used <br />for children's sand boxes. It can be used for typical <br />construction applications. <br />W, <br />The NDSU Extension Service does not endorse commercial products <br />or companies even though reference may be made to tradenames, <br />trademarks or service names. <br />This publication may be copied for noncommercial, educational <br />purposes in its entirety with no changes. Requests to use any portion <br />of the document .(including text, graphics or photos) should be sent to <br />NDSU.permission@ndsu.edu. Include exactly what is requested for <br />use and how it will be used. <br />For more information on this and <br />other topics, see: www.ag.ndsu.edu <br />County commissions, North Dakota State University and U.S. Department of <br />Agriculture cooperating. North Dakota State University does not discriminate on <br />the basis of race, color, national origin, religion, sex, gender identity, disability, <br />age, status as a U.S. veteran, sexual orientation, marital status, or public assis- <br />tance status. Direct inquiries to the Vice President for Equity, Diversity and Global <br />Outreach, 205 Old Main, (701) 231-7708.This publication will be made available <br />in alternative formats for people with disabilities upon request, (701) 231-7881. <br />3M-3-09 <br />