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flood level. In addition, auxiliary generators should be available to provide energy dur- ing a power failure for temporary lights, vital pumps to control seepage, and elevator operation. Sewer systems can be kept in operation through the use of shut off valves to prevent backup and the installation of pumps. The same pumps can also remove seepage from the building if outlets are provided which extend above known flood stages. Check valves, vacuum breakers or air gaps should be installed to prevent back siphoning. Water mains normally are kept under sufficient pressure to avoid contamination by flood waters. Pressure should be increased during floods, however, to compensate for the increased head acting on the mains. If the pumping station is flooded, however, pres- sure will be reduced and contamination can occur. This suggests an internal water sup- ply, perhaps a roof storage tank, to keep buildings in operation during floods. It is also advisable to provide cutoff valves to isolate any portion of a building which may be flooded to prevent contamination by back siphonage into those parts which are not inundated. Where water wells are located on flood plains, their casings should be sealed and extended above anticipated. flood levels to prevent the entry of polluted flood waters. Storage tanks may contain products necessary for a building's operation. They should be anchored and weighted down or else raised. above flood levels to prevent flotation and loss during floods. Closin~ Wall Openin~s and Vents Windows and vents both above and below the surface should be sealed. to prevent the entry of flood waters. They may also need to be reinforced. Care should be taken, how- ever, that the walls are strong enough to support the pressures added by vent and window reinforcements. Also, the wall itself should be treated or constructed to prevent large amounts of water from passing through it. Openings which are no longer necessary, such as old coal chutes, windows into stor- age and basement areas or unused doorways, can be permanently closed and sealed by masonry or reiniorced glass block construction. Masonry enclosures should be "keyed" into the existing masonry in a manner similar to the original construction (Figure 27). Where openings in exterior walls are necessary to the everyday function of the build- ings, there are several flood proofing alternatives. Figure 28 illustrates four alternatives ranging from partial closure to complete closure. A variety of materials and combinations can be used in window closure. Possibilities include the partial bricking in of wall open- ings with or without metal shields; the use of wooo timbers which fit in slotted jamb sup- ports, and the provision of full metal shields. Any material can be used providing it pre- vents the entry of flooo. water. Windows can be equipped with flood shields and still be attrac- tive. Figure 29 is an example in which an aluminum skin covers the brackets to which the bulkheads are bolted. Figure 30 shows a shield over an air vent which is located in a pedestrian mall to prevent entry of flood waters into the subsurface part of a building. The shield is stored in a nearby garage and is carried by several men when it must be p..1t into position. Smaller wall openings such as service chutes, vents, or windows can be sealed as in Figure 31. This type of closure requires little alteration to the building and can be installed in a minimum of time. Display Windows There are several approaches to adjusting display windows to prevent the entry of flood waters. Since these windows are so vital to store operation, they must remain attractive and function as a place of display for as long as possible. One approach is to equip the New brick used in closure Figure 27.-Masonry closure for unnecessary windows. The closure is keyed into the existing masonry to provide strength. 37