06-23-08 Drainage and Flooding Committee Minutes

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The most conservative cost estimate for a floodwall is based on a two foot high engineered cantilevered concrete floodwall. A cantilevered wall has a footing to provide stability and keep the water pressure from pushing it over. The budget shown in Table 3-1 is for a 40'x 40' home with a flood wall one foot outside the building wall. Labor accounts for about half the price in the cost estimate. Table 3-1: Floodwall Cost Estimate Two Foot high reinforced concrete cantilever wall, 168 feet @ $200/foot $33,600 Internal drainage and sump pump system 5,000 Sewer backup valve 4,500 Generator for power outages 900 TOTAL $44,000 It should be noted that smaller, non-engineered walls such as the ones in Figures 3-3 and 3-4 on page 19 have been built by their owners for less than $10,000. FEMA does not fund individual floodwalls for residential properties, therefore, the homeowner must pay 100% of the cost for a floodwall. However, each property owner can determine how much of their own labor they want to contribute and whether the cost of a wall is worth the protection from flooding that it provides. V. Dry Floodproofmg This measure keeps floodwaters out of a building by steps taken to protect the building directly. Walls are coated with waterproofmg compounds or plastic sheeting. Openings (doors, windows, and vents) are closed, either permanently, with removable shields, or with sandbags. A floodproofmg project has three components: e Make the walls watertight. This is easiest to do for masonry or brick faced walls such as those found in the study area. The brick walls can be covered with a waterproof sealant and bricked over with a thin brick veneer to camouflage the sealant. Wood, vinyl, or metal siding needs plastic sheeting to make them watertight. The most effective approach is to apply a sealant and plastic sheeting and then cover the job with brick, a second facing to protect the waterproofing from punctures. · Provide closures for the openings; including doors, windows, dryer vents and weepholes; such as removable shields or sandbags. · Account for sewer backup and other sources of water entering the building. For shallow flood levels, this can be done with a floor drain; although a valve system is more secure. Dry floodproofrng employs the building itself as part of the barrier to the passage of floodwaters, and therefore this technique is only recommended for buildings with non-cracked slab foundations because the solid slab foundation prevents floodwaters from entering a building from below. Also, even if the building is in sound condition, tests by the Corps of Engineers have shown that dry floodproofrng should not be used for depths greater than 3 feet over the floor, because water pressure on the structure can collapse the walls and/or buckle the floor. Dry Brookglen Area Analysis - DRAFT 21 9/8/2008