How to Calculate the Load Capacity of a Stream

Load capacity has to do with the capacity of a water stream to handled toxic pollutants without violating water quality standards. Environmental Protection Agency (EPA) and Occupational Health and Safety Agency (OSHA) officials must know this information to properly regulate environmental concerns and protect the public from safety hazards that could rise from toxic dumping or discharge. To calculate load capacity, you need to know water quality parameters and the flow or volume of water just downstream from the discharge associated with the stream in question.

Things You'll Need

• Water quality standards table
• Calculator

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Instructions

• 1

  Determine the water quality standards parameters based on the type of stream and the toxin or pollutants in question. Refer to the water quality standards table. (see References). Or, you can contact the Environment Protection Agency or the Occupational Health and Safety Agency (OSHA) to locate similar charts that may be available for your state or local area. An example of a representative number would be 0.51 ug/l, which reads 0.51 micrograms of toxin per liter of water.

• 2

  Contact OSHA to determine the permissible exposure levels (PEL) for the water in the stream in question. From the calculations and data, find the volume of water quantity they used to make the PEL calculation relative to the water flow just downstream from the discharge location. A representative example of this type of number will be 500 l/ft^3, which translates to 500 liters of water per cubic feet.

• 3

  Multiply the water quality standards number from the chart by the water flow number to calculate load capacity. Using the sample numbers above, the load capacity is 255 ug/ft^3 (0.51 ug/l x 500 l/ft^3). This means the stream has a capacity of holding 255 micrograms of toxin for each cubic feet of water without violating water quality standards for that stream.