7.The Hudson River is extensively contaminated with PCBs and these are believed

Question

7.The Hudson River is extensively contaminated with PCBs and these are believed to be primarily from discharges from a large General Electric (GE) factory on the Hudsorn. We briefly discussed in class how, after many years of fighting, GE finally began to dredge the sediments six years ago. A key argument GE made against dredging is that it is too disruptive of the environment. But EPA argued that it is possible with modern methods to minimize environmental damage while dredging. a. Identify typical ecological disruptions that occur from dredging. Just a list; nota k could be taken to mininm

Explanation / Answer

a)

The potential emvironmental effects of maintenance dredging are generally two fold, firstly as a result of the dredging process itself and secondly as a result of the disposal of the degraded material.

The impact of dredged material disposal largely depends on the nature of the material and the characteristics of disposal area.The environmental affects of dredging must take account both for short term and long term.The potential impacts of dredging can be summarised as follows.

1. Removal of subtidal benhic spicies and communities.

2. Short term increases in the level of suspended sediment can give rise to change in water quality which can marine Flora and fauna, both favourably and non favourably, such as increased in turbidity and the possible release of organic matter, nutrients and or contaminants depending upon the nature of the material in dredging area.

3. Settlement of these suspended sediments can result in the smothering or blankering of subtidal communities and adjacent intertidal communities, although this can also be used benficially to rise or erosion.

b )

1. To choose suitable time to dredging. They are time minimize move around of dredging or moving along along a way from zones.

2. To choose advance technology for dredging. For example CSD technology.

3. Use a good medal to simulate hydrodynamics and sediment transport condition could be the mitigation measures.

4. Dredging should be undertaken only during the mid days within a phase of the new and the full moon days. During these days, tidal amplitude is the lowest in the in the particular moon phase. As the water movement is the least, siltaton on marine biota can be minimized.

5. Grabbing of benthic substratum entails lesser disturbance of mud particles as compared to it's deposition at some place away from it's original source through the action of water movement.

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