I just got mail from my dad. I wrote him asking if he thought 9,500 sandbags would be enough to protect the Spolana facility. This is his response. (Note: USACE=US Army Corps of Engineers, RDFW=Rapid Deployment Fortification Wall) :
On the average, filledÂ sand bags weigh, an average ofÂ 30 pounds per bag.Sand weighs 110 pounds per cubic foot. That gives you 3.66 bags per cubic foot. Sand bag structures must be built in a trapezoidal shape. At ERDC sandbag structures 3 feet high with a 3 ft. wide top and a 9 ft base failed to hold 3 feet of static water and also failed duringÂ small wave tests. As water elevation increased, seepage rates increased until the water pressure dislodged the bags and the structure failed.Â In field testing, the sand bag structure 4 feet high, with a 4 ft. wide top and 12 ft base also failed to hold 4 feet of water and failed.Â Check USACE ERDC web site under Expedient Flood Fight Structures Program or search RDFW.
Each threat is different. Heights and lengths for sand bag structures differ. To determine sand bag structure trapezoidal volume : Pyramid structures do not work at all.
B1 plusÂ B2 or top width of theÂ structure plus bottom width of structure – Divided by 2, X the height, X the length. That will give you cubic feet. Multiply that by 3.66 and that will tell you how many sand bags you need. Trying to justify 9500 sand bags is odd.
In the US, preparedness is finally taking hold following the Katrina and RitaÂ showings . On the average preparedness costs that are effective are 15% of recovery costs. Or an 85% savings.
In terms of RDFW, each expanded unit holds the equivalentÂ of 35 filled sand bags. We actually had CCC kids fill bags and stack them in a pile and dump them into a single RDFW unit.Â 7 men crews can build a 100′ long X 4′ ft wide X 4 ft high structure in 1 hour. A sand bag structureÂ of equal strength must be trapezoidal or 4′ top + 12′ baseÂ Â divided by 2 = 8 X 4 = 32 X 100 = 3200 cubic feet X 3.66 sand bags per C/FT = 11,712 sand bags.
It takes an average of 35 people (in 8 hour shifts) 20 hours to build a 100 ft sand bag wallÂ – 15 filling, 15 daisy chaining, 5 stacking.Â That is 700 man hours. It takes 7 man hours to build an RDFW 100 ft. long. if we had 35 people we could install 500 lineal feet in one hour or 10,000 feet in 20 hours.