An engineering firm involved in the design of the 17th Street Canal levee and floodwalls said Friday that the Army Corps of Engineers overruled its recommendation to drive sheet piling to a depth of 35 feet below sea level along a stretch of the floodwall that failed during Hurricane Katrina, causing massive flooding in Lakeview and other parts of the city. William B. Conway, chairman of the Metairie engineering firm Modjeski and Masters, in a letter to The Times-Picayune, said the corps plan eventually led to pilings that were driven just 10 feet below sea level. Modjeski and Masters was...