Water Quality Impacts of Contaminated Sediment Removal Using Hydraulic Dredges

该项目的目的是通过广泛的现场数据收集，结合美国ALCOA Point Comfort/Lavaca Bay超级基金可处理性研究，研究使用传统液压刀盘挖泥船去除受污染沉积物对水质的影响。研究的具体目标是：(1)在代表其他补救地点的常规液压刀盘疏浚作业期间，收集清淤头附近及水柱（25米至500米）内的水质数据；(2)在一系列疏浚作业条件下收集这些数据；(3)评估与此类疏浚作业有关的水质影响范围；(4)利用近场数据验证和完善Hayes（1998）提出的将泥沙再悬浮速率与疏浚特性和操作参数联系起来的模型；(5)对沉积物进行柱沉降试验，尝试验证Je（1998）提出的远场悬浮泥沙输运模型；(6)根据疏浚作业期间收集的水质数据，通过计算从现场输运的泥沙量和汞量，评估再污染的可能性，并将其与指定地点的实测沉积物沉积量和汞浓度进行比较。美国国家研究委员会（National Research Council）估计，每年要从美国的港口、港口和水道中疏浚1400万至2800万立方码受污染的沉积物，以维持既定的航行深度。已知在非通航区域和指定的超级基金地点存在大量受污染的沉积物。虽然这些沉积物中的许多可以留在原地，但在污染物进入食物链的地方，采取补救措施是必要的。然而，对搬迁过程中对水质影响过大的担忧阻碍了清理行动。这项研究的结果将为污染沉积物清除作业对周围和下游水生环境质量的影响提供额外的知识。

9876401 Hayes The objective of this project is to study the water quality impacts associated with removing contaminated sediments using a conventional hydraulic cutterhead dredge through extensive field data collection in conjunction with the ALCOA Point Comfort/Lavaca Bay Superfund Treatability Study. Specific objectives of the research are to: (1) gather water quality data from near the dredgehead and in the water column (25m to 500m) during conventional hydraulic cutterhead dredging operations under conditions representative of other remedial sites, (2) gather these same data under a range of dredge operating conditions, (3) evaluate the range of water quality impacts associated with this type of dredging operation, (4) use the near-field data to verify and refine the model proposed by Hayes (1998) that relates the rate of sediment resuspension to the dredge characteristics and operating parameters, (5) conduct column settling tests on the sediments and attempt to verify the far-field suspended sediment transport model proposed by Je (1998) and (6) evaluate the potential for recontamination by calculating the amount of sediment and mercury transported away from the site based upon the water quality data collected during the dredging operation and compare that to measured sediment deposition and mercury concentrations at specified locations. The National Research Council estimates that 14 to 28 million cubic yards of contaminated sediments are dredged annually from U.S. ports, harbors and waterways to maintain established navigation depths. Larger volumes of contaminated sediments are known to exist in non-navigable areas and designated superfund sites. While many of these sediments can remain in place, remedial actions are necessary where contaminants are finding their way into the food chain. However, concern over excessive water quality impacts during removal hampers cleanup actions. The results of this study will provide additional knowledge of the effects of contaminated sediments removal operations on the quality of the surrounding and downstream aquatic environments.