A double wall impact protection levee such as I am proposing uses the concept of a force-couple. The waterside sheetpile is in tension while the landside sheetpile is in compression. This balances the resistance of the force-couple so that each pile can withstand equal vertical pressure. Ideally, the sheetpile in tension is longer than the one in compression due to the nature of the soft soils. The area between the sheetpiles is filled with an appropriate impact resistant material (river sand) to act as a shock absorber against sudden impacts. The final component is to connect the sheetpiles with either a series of rigid, horizontal struts or with a concrete cap. If a cap is used the area can be adapted for recreational uses such as biking or jogging paths while also allowing access for ongoing levee inspection.

There are advantages to using the double wall impact levee. Slope stability is not a factor as this design is simply a vertical wall with no slope. In addition, there is flexibility in the length of sheetpile used. Depending on soil conditions, each pile can protrude above ground to the level matching the amount of hurricane protection desired. If a category 4 storm (Staffir-Simpson Scale) is the goal, then the top of the piles must be elevated from 12 to 18 feet. The final step is earthen fill on the land side as an added precaution that reinforces the entire system.

This system can be constructed within the existing rights of way — thus no additional land need be expropriated. It can be installed quickly and within theoriginal funding allocated by Congress for levee reinforcement and rebuilding even if the cost was $1,000 per linear inch!