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HOW DOES DREDGING AFFECT OUR ENVIRONMENT?

Adrina Hernandez Biology 338 Doctor Brown December 2. 2016


INTRODUCTION ď‚„

Living in San Diego county among the beautiful coast line we are so lucky to have, many of us are familiar with the dredging that goes on in our harbors and beaches. Dredging is the process of removing material (sediment, debris, and organic matter) from the bottom of a water body in order to make it deeper. Additional depth in estuaries is usually needed to allow for commercial and or recreational water traffic such as oil tankers, other cargo ships, tour boats, ferries and larger power or sailboats(Discovery of Estuarine Environments). When we hear that a beach is getting dredged, we think of sand being pumped out of the ocean and put back onto the beaches so we can enjoy them every summer and also harbors being dug out so that they are deep enough for boats to enter and exit.


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Every year, the Oceanside Harbor gets dredged before summer begins. This year, about 260,000 cubic yards of sand and debris were removed from the entrance of the harbor and were placed along Oceanside beaches (Sifuentes). This is done so that boats can enter safely without the sandbar getting too high. Another area near home that has been recently dredged is the San Diego Bay. What many people do not realize are the hidden effects dredging plays on our environment. Although there are pros to dredging out harbors and beaches, there are many cons. Dredging plays a huge role in our economies and lives, but also damages many ecosystems and releases toxins into our water and is a very controversial topic throughout the world.

(CITY OF OCEANSIDE FACEBOOK PHOTO)


PROS ď‚„

Although Dredging is harmful to the Environment, it plays a big role in our economy and lifestyles. Dredging is very important in keeping our harbors, rivers, and canals accessible for boats and water trade. The buildup of sediments in an estuary is a natural process that is a result of weathering or erosion of the land due to rainfall(Discovery of Estuarine Environments). Another cause of buildup is from natural and unnatural debris. Over time the sediment and debris settle making the entrance more shallow. Dredging is especially important in our local San Diego Bay.

San Diego Bay (KPBS.org)


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It is one of the most commercially important bays, and it is an important military base( Sifuentes). Without dredging, the San Diego Bay would become shallow and would no longer be able to able to support our large military population nor our trade and economy. Dredging not only clears out harbors and canals, but it also prevents a build up of materials along breakwaters and jetties. One of the most important reasons for dredging is to remove contaminants and pollutants that have been building up for years and years. The sediments that accumulate in harbors, such as the San Diego Bay, may be contaminated with a host of heavy metals, man-made chemical compounds, and other potentially serious pollutants. These contaminants pose a risk to humans and marine life when they are dredged up from the bottom of the estuary(Discovery of Estuarine Environments). Toxins from industrial operations, shipyards and urban runoff have built up over decades, settling in the sediment and are then absorbed by small animals, fish and eventually people, especially frequent fishermen(Sifuentes).


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2013, about 159,000 cubic yards of contaminated sediment was removed from the San Diego Bay from a 63-acre site near the NASSCO and BAE Systems shipyards just south of the Coronado Bridge (San Diego Coast Keeper). Once the sediment is scooped and removed, it is usually dried taken to landfills. With so many toxins in our water, it is crucial to remove it for our safety and the health of our community. San Diego is popular for many fishermen, divers, and snorkelers so this poses a huge health risk if not removed. A main concern people have for the toxins that are removed is where they will go one they are discarded. What is removed can be used for beach nourishment, road construction, landfill cover, and remediation of contaminated sites(Discovery of Estuarine Environments). There are many laws, such as The Clean Water Act, that protect our waters and restrict where these contaminants can be dumped. Another big concern people have for dredging are the environmental impacts. Although dredging will always impact the environment, they can be less harmful if certain dredgers are used(marine insight).


CONS ď‚„

Dredging may be beneficial to our economy, but it harmfully impacts our environment and marine life. Dredging releases harmful, toxic chemicals and also spreads unwanted nutrients and organisms. These chemicals can be absorbed by plants and marine life and are then carried up the food chain to humans. Some harmful substances released back into the water include heavy metals, oil, TBT, PCBs and pesticides(UK Marine Special Areas Conservation. Since the toxins are harmful to marine plants and animals, they can have a great affect on the biodiversity in ecosystems. The water could get polluted because of the soil particles mixing with the water, and while this does not have huge impacts, it is indeed an unwanted side-effect of dredging(marine insight).

CAFNEC.org


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Although sediment removed from the ocean during dredging can be used for beach nourishment, construction, and landfill cover, most of the material dredged in harbors, estuaries and at sea are dumped in the ocean and only minor amounts of this dredged material are beneficially used(OSPAR Commission). With all the harmful chemicals and toxins placed back into our oceans at large amounts, marine animals and ecosystems are harmed. Coral reefs and fish nurseries are especially harmed due to their sensitivity to change in their environments. Dredging also has detrimental impacts on the donor sites being dredged. Shortterm increases in the level of suspended sediment can give rise to changes in water quality which can affect marine flora and fauna, both favorably and unfavorably, such as increased turbidity and the possible release of organic matter, nutrients and or contaminants depending upon the nature of the material in the dredging area(UK Marine Special Areas Conservation).


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Dredging disrupts the natural flow of underwater ecosystems by removing large parts of the sea bed, destroying habitats. When dumped, the sediments can cover sea creatures and their food. Before the particles of the sediment settle onto the ground however, they are suspended in the water. This blocks the amount of sunlight shining into the water and can cause and huge impact on those species who depend on a large amount of light for survival. During all dredging operations, the removal of material from the seabed also removes the animals living on and in the sediments (benthic animals); with the exception of some deep burrowing animals or mobile surface animals that may survive a dredging event through avoidance, dredging may initially result in the complete removal of animals from the excavation site(UK Marine Special Areas Conservation) .

ResearchGate.com


CONCLUSION ď‚„

There is much debate on the effects of dredging and if the good out ways the bad. With all the data given to us, we can determine that dredging negatively impacts the environment. Although it causes great harm, it is needed for our economical productivity. To ensure we cause the least harm to marine ecosystems and human health, we can ensure that the right dredgers are used. For example, the hopper dredgers that suction out the deposits are considered to be a major cause for turbidness in the dredged water-part. It has been recommended that those dredgers which present a chance for pollution and extensive contamination be avoided and replaced with other safer methodologies(marine insight).

Maritime Journal


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We can make sure we dredge at specific times where the least amount of species are harmed. If there were laws to make it mandatory for a company to reuse at least a specific percentage of the sediment dredged it would mean that less would be placed back into our oceans to cause damage If we can be aware and conscious of our human impact on the environment, we can strive to cause the least harm while still ensuring the productivity of our economy and social lives on this earth.

San Diego Union Tribune


WORKS CITED 

Manap, Norpadzlihatun, and Nikolaos Voulvoulis. "Data Analysis For Environmental Impact Of Dredging." Journal Of Cleaner Production 137.(2016): 394-404. Academic Search Premier. Web. 29 Nov. 2016.

Sifuentes, Edward. "Oceanside Harbor Dredging Starts." Sandiegouniontribune.com. N.p., 21 Aug. 2016. Web. 09 Nov. 2016.

"Assessment of the Environmental Impact of Dredging for Navigational Purposes." OSPAR Commission. N.p., n.d. Web. 9 Nov. 2016.

"Dredging, Drying, Trucking, and Testing: The Ins and Outs of the San Diego Bay Cleanup San Diego Coastkeeper." San Diego Coastkeeper. N.p., n.d. Web. 09 Nov. 2016.

"Environmental Impacts of Maintenance Dredging and Disposal." Environmental Impacts of Maintenance Dredging and Disposal. UK Marine Special Areas Conservation, n.d. Web. 09 Nov. 2016.

"Policy and Management." "Dredging and Disposal of Marine Deposits"- Case Specific Issues for Narragansett Bay: Discovery of Estuarine Environments (DOEE). N.p., n.d. Web. 09 Nov. 2016.


How Does Dredging Impact the Environment?