What About the Soil After the Flood?

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Lenoir County received just under 19 inches of rain during the five days that Hurricane Florence crossed through the area. Flood waters that resulted from the storm deposited microbes containing bacteria, viruses, protozoa and helminthes in soils.

Storm water floods may contain many contaminants including:  run-off from roads and bridges, sediment with pollutants such as heavy metals or pesticides, Hydrocarbons, oils and grease leak onto road surfaces and pavements, heavy metals from car exhausts, worn tires and engine parts, brake linings, paint and rust, fertilizers, pesticides and herbicides.

It is very difficult to determine the concentration of microbes in flood water because of the many factors. There are numerous and a large variety of sources that can contribute to contamination. The number of sources, the kind, the volume of contaminants and the level of treatment all affect the degree of concentration. Microbial survival and persistence is also influenced by many environmental factors. These include temperature, soil desiccation, pH, soil characteristics and sunlight.

The microbial survival in soil and the resulting potential for exposure is quite difficult to predict because of the multiple variables. Research has determined that at room temperature some microbes in soil survived from 9 to 12 days. Other microbes persisted in a moist environment from 60 to 180 days. The intensity of sunlight exposure, the moisture level of soil and the temperatures needed to kill all microbes also varied. Temperature, moisture and sunlight are all factors in microbial survival in soil.

The multiple variables that result in survival or control of flood water contaminants makes it important for individuals to use caution in working with soil. Practice clean sanitation:  wear gloves as much as possible and wash your hands frequently with soap and water.

A general suggestion is to allow 2 to 3 months for bacteria to significantly reduce contaminants before planting in your garden again.