expected load and use, to form the roadway. Conner et al. (1976) illustrate 

 some of the typical board patterns. 



Board roads are usually temporary and are removed after the site has been 

 drilled. When the road is to be left for a long period, however, earth, river 

 sand, and shell or gravel will be placed over the top to form a cap. Despite 

 these precautions, heavy traffic and capillary action pump water from the marsh 

 level up into the levee (Conner et al., 1976). This softens the fill, and 

 after a while holes or slumping will occur at road level. If the boards are 

 exposed to traffic, they may break into the hole. Usually the hole is filled 

 with shell or crushed stone and a few more layers of board are added. In cases 

 where the boards are buried, the hole is filled with shell or gravel. 



In many areas, the marsh soil is stronger so that a levee is not needed. 

 Often the board road sheeting will be laid directly over the marsh surface, 

 without any sort of underlying layer being placed down. In this case, no 

 preliminary steps are required before laying the boards, though small toe 

 levees may be built on either side of the roadway to exclude unexpected high 

 water. If built, the fill for the toe levees will come from the nearby marsh. 



When marsh soil is used to build levees, draglines are the usual excavation 

 machines. Sometimes they may operate from the newly formed levee; on other 

 occasions they will bring their own series of board mats to move across the 

 marsh. These mats will spread the weight over the marsh surface, though they 

 may result in some crushing of the vegetation. Borrow pits have often been dug 

 in a continuous line beside the levee. This can encourage drainage of the 

 marsh area by proviaing a low spot into which water drains. If the marsh is 

 above mean sea level and the tidal influence is low, water may continuously 

 drain off the marsh surface and upper soil levels. 



If the continuous ditch is near sea level and there is a moderate tidal 

 fluctuation, salt water may intrude further into the marsh via the ditch than 

 it did previously. The salinity regime of nearby areas may change as a result. 

 Some land owners have required the contractor to stagger the pits so no contin- 

 uous water channel is formed. However, even spots where pits are staggered or 

 end before connecting with a drainage channel have had brackish or saline 

 waters flow into the borrow depressions due to additional factors. Grazing 

 cattle using the unexcavated area to cross from one side of the ditch to the 

 other can significantly soften the soil. Biological activity, such as feeding 

 upon vegetation by geese, muskrat, and cattle, or alligators' use of unexcavated 

 areas as travel routes between ponds, have denuded and eroded the intact surface. 

 Later, given the proper combination of conditions of rain and/or tide, these 

 areas have been eroded further until open channels form. 



Unless an unusual erosion problem occurs, levees are not vegetated artifi- 

 cially. In most areas, growth of colonizing plants on levees is rapid, and 

 artificial seeding is not necessary. 



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