A quick guide to Sandbags
Sandbag are made of hessian or woven polypropylene that is filled with sand or soil and used for such purposes as flood control and fortification. Sand bags are an excellent choice for the construction of levees, berms, dikes and barricades for erosion control, flood walls, and traffic control used for supporting highway signage. Sandbags may be used flooding during emergencies when rivers threaten to over-flood, or a levee or dike is damaged. Quick action and bags on-hand could save countless Pounds in personal and property damage.
WHEN CAN SANDBAGS BE USED?
The use of sandbags is a simple, but effective way to prevent or reduce flood water damage. Properly filled and placed sandbags can act as a barrier to divert moving water around, instead of through, buildings. Sandbag construction does not guarantee a water-tight seal, but is satisfactory for use in most situations. Sandbags are also used successfully to prevent over-topping of streams with levees, and for diverting current flows to specific areas.
Sandbags alone should not be relied on to keep water outside a building. Using plastic / wooden boards, scaffolding boards or polythene sheeting, tarpaulins with sandbags. To form a sandbag wall, place bags tightly against one another to form the first layer of defense. Stagger the second and subsequent layers of bags, much like the pattern of brick wall pattern effect.
Sandbags, when properly filled and placed, will redirect storm and debris flows away from property improvements.
WHAT ARE THE DIFFERENT TYPES OF SANDBAGS?
- Hessian The most commonly used bags for temporary protective barriers. Hessian Sandbags have been used by the military and government for many years around the world. They resist all kinds of severe weather and are very useful for flood and traffic control. Hessian Sacks will eventually rot if not covered or protected from the elements. Empty bags can be stockpiled for emergency use, and will be serviceable for several years, if properly stored in dry conditions.
- Woven Polypropylene When treated for UV exposure, commercial plastic (polypropylene) sandbags are available. They provide the strongest material for flood control, levee, trench and berm construction and all temporary or permanent protective barriers. When covered from ultra violet exposure, Polypropylene Sandbags last almost indefinitely with a minimum of care, but are not biodegradable. Thus they have to be disposed of, or will remain around a long time.
WHAT SIZE BAGS WORK BEST FOR PRIVATE RESIDENCES AND BUSINESSES?
Use bags about 14-18" wide, and 30-36" deep. Sandbags should be filled half full for easy stacking and will weigh approximately 30 pounds. Thirty sandbags are equal to approximately ½ ton (one ton is 2000 pounds) and is the maximum legal load limit for a ½ ton truck.
HOW CAN I FIGURE OUT HOW MANY SANDBAGS I NEED?
It takes an average of 600 sandbags to cover a 100 foot section, 1-foot high.
HOW FULL SHOULD THE BAG BE FILLED?
Bags should be filled between one-third (1/3) to one-half (1/2) of their capacity. This keeps the bag from getting too heavy, and permits the bags to be stacked with a good seal.
WHAT MATERIAL SHOULD BE USED TO FILL THE SANDBAGS?
A heavy bodied or sandy soil is most desirable for filling sandbags, but any usable material at or near the site has definite advantages. Coarse sand could leak out through the weave in the bag. To prevent this, double bag the material. Gravelly or rocky soils are generally poor choices because of their permeability. Filled bags of earth material will deteriorate quickly.
HOW MANY PEOPLE DOES IT TAKE TO FILL SANDBAGS?
Sandbag barriers can easily be constructed by two people, as most individuals have the physical capability to carry or drag a sandbag weighing approximately 30 pounds.
WHAT IS THE BEST METHOD TO USE TO FILL SANDBAGS?
It is recommended to use a two-person operation to fill sandbags. Both people should be wearing gloves to protect their hands. One member of the team should place the empty bag between or slightly in front of widespread feet with arms extended. The throat of the bag is folded to form a collar, and held with the hands in a position that will enable the other team member to empty a rounded shovel full of material into the open end.
The person holding the sack should be standing with knees slightly flexed, and head and face as far away from the shovel as possible. The shoveler should carefully release the rounded shovel full of soil into the throat of the bag. Haste in this operation can result in undue spillage and added work. The use of safety goggles and gloves is desirable, and sometimes necessary.
WHAT IS THE HEIGHT LIMIT TO STACK SANDBAGS SAFELY?
As a rough guide limit placement to 4-6 layers, unless a building is used as a backing or sandbags are placed in a pyramid.
HOW DO YOU STACK SANDBAGS?
- Fold top of sandbag down and rest bag on its folded top (preferably untied so it will lay flat).
- Take care in stacking sandbags. It is important to place the bags with the folded top of the bag in the upstream or uphill direction to prevent the bags from opening when water runs by them.
- Tamp each sandbag into place, completing each layer prior to starting the next layer.
Clear a path between buildings for debris flow.
- Lay a plastic sheet in between the building and the bags to control the flow and prevent water from seeping into sliding glass doors.
- Limit placement to three layers, unless a building is used as a backing or sandbags are placed in a pyramid.
HOW DO YOU DISPOSE OF SANDBAGS AFTER THEIR USE?
Homeowners should empty the material in the bags in their gardens or yards, then throw the bags in the trash.
Before disposing of used sandbags, check for contamination. Sandbags exposed to contaminated floodwaters may pose an environmental hazard and require special handling.
- Sandbags will not seal out water.
- Sandbags deteriorate when exposed for several months to continued wetting and drying. If bags are placed too early, they may not be effective when needed.
- Sandbags are basically for low-flow protection (up to two feet). Protection from high flow requires a permanent type of structure.
- Sandbags are not always an effective measure in the event of flooding because water will eventually seep through the bags and finer materials like clay may leak out through the seams.
SANDBAG DON’Ts . . .
- Sandbags should never be used to build a fortress around the perimeter of one's property. Doing so can actually trap flood-waters between sandbag walls and structures, leading to further damage.
- Do not use refuse sacks, as they are too slick to stack. Do not use used feed sacks.
Click on the link below for more information on how to use a Sandbag properly for flood protection.
Environment Agency March 2009 - Sandbags: how to use them properly for flood protection