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The Subsurface Part of the Buildin~ Newly designed buildings may have machinery located on upper floors but most older structures have the electrical machinery, the heating and the pumping equipment on lower floors. It is these lower, subsurface floors, which first experience flooding problems from seepage and sewer backup. Since flood proofing systems often require pumps, elec- trical equipment and emergency generators as an essential part of the operation--these must be kept in working condition throughout the crisis. When buildings have entrances to subsurface levels which lead out onto ground level, these entrances should be adjusted to prevent the entry of overland flow. Figure 24 shows how a stairway opening could be flood proofed by encasing the entrance with a concrete block wall treated with asphalt and installing a watertight bulkhead door. To increase the strength of such a wall, the block cells could be filled with concrete and steel reinforcing rods. The two photographs in Figure 24 are existing examples of this technique in use. One of the installations in this figure is a part of the flood proofing program at the Chicago Union Station which was initiated as an aftermath of the 1954 flood which inundated the sta- tion. Several buildings subject to flocx:l have installed low protection walls around furnaces, air-conditioners and other valuable equipment (Figure 25), to protect the equipment if wa- ter accumulates in the basement. This approach may prove most desirable when the base- ment floor is not adequate to withstand hydrostatic pressure, so that flooding to a few feet is allowed to prevent the floor from cracking or rupturing by equalizing the pressure. In some cases pumps are operated from the "safe" islands to control the water depth in the other parts of the deliberately flooded basement. Only enough water is allowed in the base- ment to prevent structural damage. An alternate methcxi of protecting valuable equipment would be to "mothball" it by ap- plying a coating of grease, by spraying with parafin or plastic, or by enclosure in water- proof jX)lyethylene or vinyl film. Equipment so protected can be submerged for consider- able periods and later put back in operation with a minimum of expense compared to the cost of restoring unprotected equipment. When none of the above measures is possible, or in the case of an emergency, it is sug- gested that the motors, other vital electrical relay components and mechanical equipment be removed and stored above flood level. Even if this cannot be done, much of this equip- ment can be restored to working condition by proper salvage even if inundated. Salvage of equipment and materials can be another method of reducing flood loss. The goal of flood proofing is loss reduction, however it is accomplished. Figure 24.-Flood proofing to prevent overland flow from entering subsurface levels. These photographs are examples of walls which have been built around openings which lead from above the ground level to subsurface levels of buildings. Until these flood proofing measures were undertaken, flood waters flowing on the surface would enter through these openings and inundate the lower levels. (Photo on right by TV A.) 34