Pollutants in Storm Water Discharge

April 5, 2009

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[Download not found]Various shipyard operations and processes can be the source of pollutants found in shipyard stormwater discharges.

It is important to identify the pollutant types, their potential sources and estimate the loading from these sources in order, to determine where Best Management Practices to control the discharges can be applied.

This paper uses common shipyard operations and processes as examples to demonstrate how to determine the types of pollutants generated, estimate their loading in stormwater, and perform a pollution pathway analysis.

The flow chart indicates both the steps in the process, and where in those steps pollutants may be released to the environment.

Using dry abrasive blasting in a blast pit as an example, we would assemble the following information necessary to estimate the annual loading of copper in stormwater discharges.

Like operations and processes analysis, pollution pathway analysis is performed by determining the specific sequence of steps or paths a pollutant will take from its origin to its discharge point.

In the blast pit, dust may first be emitted to the air, followed by deposition to the ground within the facility, and then transported by stormwater to a drain where upon it is discharged to the surface waters from an outfall.

In this example, the same process generated the same emissions, but the location of the activity in the shipyard resulted in completely dissimilar pathways to the same media.

As illustrated in the example, a pollution pathway flow chart begins at the point of discharge of the emission, and ends at the point where the pollutant is discharged to the media.

This methodology evaluates processes as potential sources of pollutants, and prioritizes the sources based upon their estimated contribution to the overall facility (or area) pollutant loading.

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