oriented at some angle to the levee alignment; consequently, only a 

 small number of holes is dug unless the levee is quite wide. The 

 majority of the holes are dug on systems adjacent to the levee/spoil 

 bank. Surveyors enter the area by truck, marsh buggy, or on foot, 

 stake the lines, and mark the areas where shot holes and geophones 

 will be placed. Vegetation may be cleared along a path 3 to 4 m (10 

 to 15 ft) wide. A drilling truck or buggy and one or two support 

 vehicles enter next; holes are drilled, charges and recording equip- 

 ment are placed, and shots are fired. Geophones are retrieved, and 

 after completion of all shots on the levee system, the holes are 

 plugged and the crew exits. 



2. Primary ecological alterations 



2.1 Creation of ruts or depressions in the land surface, possibly 

 breaching the levee 



2.2 Trampling and crushing of vegetation along shot line path 



2.3 Localized change in direction of water flow 



2.4 Creation of pathway for increased rate of flow of runoff 

 Attribute alterations 



The movement of work crews and marsh vehicles over the land surface 

 tramples and crushes vegetation in a zone wider than that cleared 

 for shot placement. The vegetation may be completely destroyed in 

 some areas, depending upon the soil moisture conditions. This 

 results in an immediate decrease in food and cover for the consumers 

 in the area. The total area affected is usually small in comparison 

 to the remaining area of productive vegetation, and the effects on 

 consumers and detrituts accumulation are usually insignificant. 



The depth and number of ruts created by marsh vehicles are dependent 

 upon the total number of trips and the degree to which vehicles re- 

 trace, existing tracks. Deep ruts, resulting from retraced trails 

 which parallel the levee alignment, will form depressions for the_ 

 movement of water and, if deep enough, may result in standing bodies 

 of water during wet seasons. The orientation and depth of the de- 

 pressions determine whether they (1) remain for long periods of time 

 and (2) alter the water regime of the local area by increasing or 

 decreasing the surface water and macropore water. In extreme cases 

 the deep tracks cross the entire levee or spoil system; this breach- 

 ing could establish water flows between the systems on either side 

 of the levee/spoil -bank system. Assuming that this major change does 



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