tempered. In general, inundation will affect the system by adding salts, 

 mineral sediments, and nutrients to the highly organic (peat) soils. 

 Changes in vegetative composition depend upon the frequency and extent of 

 inundation by saline or brackish water. 



The degree and significance of wildlife displacement resulting from 

 leveed road construction activities is difficult to predict though the 

 effect is short term due to the rapid rate of construction (0.1 to 0.5 km 

 per day). The disturbance due to construction is likely less than that 

 due to the long-term continued use of the roadway over many years. 



Key attribute alterations 



The key alterations involve the digging of the borrow pit and disruption 

 of flow patterns within the marsh. Direct losses of vegetation always 

 occur; the areal extent and impact on consumers are minimal. However, 

 significant secondary changes may be induced by the altered regimes of 

 water flow. 



Site access by canal and wellsite dredging . 



1. Activity sequence 



Surveyors enter the marsh by vessel, marsh buggy, or on foot, stake the 

 wellsite location and access route, and leave the area. The pathway may 

 or may not be the most direct one possible. Usually there is no need to 

 clear vegetation, but vegetation may be trampled and crushed in adjacent 

 zones. 



Site location, equipment availability, spoil placement requirements, and 

 economic factors may dictate which type and size of dredged is used in 

 each phase of the operation. In a fresh marsh, any new canal is usually 

 an extension or branch of an existing canal. Therefore, a barge-mounted 

 bucket dredged or a hydraulic dredge may be used. Alternatively, a track- 

 mounted bucket dredge may be employed. Spoil is placed on both sides of 

 the channel and completely around the well site in most cases. Canal 

 depths must be about 3 m (8-10 ft); typical widths approach 23 m (70 ft); 

 a 10-m (30-ft) berm typically exists between the canal edge and the inside 

 foot of the continuous spoil banks on both sides of the canal. 



Small vessels, crew boats, supply boats, and tugs may move to the dredg- 

 ing site daily. Alternatively, marsh buggies may be used for these 

 functions. After the wellsite location is dredged (usually 50 by 115 m, 

 or 150 by 350 ft), all equipment moves out of the area. Redredging may 

 be necessary once every six months to once every five yr. 



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