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M6 PM Fate and Transport of Pollutants from Dredging and Placement
(PRI-1117-838799) Predicting Water Quality Compliance for the Discharge of Runoff Water from Dredged Material.
Price, R1, 1 USAERDC - Environmental Laboratory, Vicksburg, MS, USA
ABSTRACT- Placement of dredged material into a confined disposal facility (CDF) may result in discharge of surface runoff water during rainfall. Water leaving an upland confined disposal facility (CDF) must meet applicable State water quality standards for discharge into receiving waters. When dredged material is placed in a CDF, contaminant movement from the wet, unoxidized material will be mainly associated with suspended solids. As the material dries and oxidizes, suspended solids concentration may decrease while contaminants such as heavy metals may become more soluble due to physicochemical changes of the dredged material. A rapid screening test was developed to predict the effects of these changes on the resulting water quality discharge so that controls could be engineered into the CDF design process. The simplified laboratory runoff procedure (SLRP) simulates the oxidative processes that may have significant effect on pH and solubility of metals. Sediment samples are collected from a proposed dredging project and oxidized with 30% H2O2. Oxidized sediment is added to deionized water to simulate 50, 500 and 5000 mg l-1 total suspended solids (TSS). These TSS concentrations are within the range measured in runoff water from aged dredged material in CDFs. To simulate freshly placed dredged material, unoxided sediment is used at 500, 5,000 and 50,000 mg l-1. The prepared samples are placed on a mechanical shaker and agitated for one hour to ensure complete particle suspension. Samples are then analyzed for both total and soluble (filtered) contaminants. Results of field and laboratory studies will be presented.
Key words: rainfall runoff, dredged material, water quality
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