Why Should I Care about Concrete Washout?
By Matthew Trygg // 2020-07-30
Water used in the concrete washout process has a high level pH, that pH level can be near 12, which is essentially the same as liquid drain cleaner, ammonia or other household cleaning detergents. The safe pH ranges for aquatic life habitats are 6.5 – 9 for freshwater and 6.5 – 8.5 for saltwater. Another issue with concrete washout is it has other toxins include Aluminum, Barium, Chromium, Hexavalent Chromium (Chromium 6), Copper, Iron, Magnesium, Manganese, Nickel, Potassium, Selenium, Sodium, Vanadium, and Zinc. “Toxins can clog fish gills, reducing their oxygen and causing death. These pH levels can also be long lasting in the soil. Plants may become stunted or refuse to grow in these soils. Restoration of ground surface surrounding washout facilities may require removal and replacement of topsoil, nutrients, and alkaline tolerant seed mixture. (IUM)”
What can be done about this and what are some of the rules associated with concrete washout container?
The primary concern is the mixing of water with the concrete slurry. This means that if you have an open concrete washout container and rainwater fills your container over 2/3, the Illinois' rule states “existing facilities must be cleaned, or new facilities must be constructed and ready for use once the washout is 2/3 full (IUM).” This is because if the concrete slurry and rain water mixes, that water is now toxic. One solution to this may be simply putting a tarp over the container prior to rainfall or covering the washout area except when in use.
A major issue would be the contaminated water entering a waterway. That is why “Washout facilities shall be located on level ground a minimum of 15 m (50 ft) from storm drain inlets and all open drainage facilities. For smaller sites where the distance criteria may not be practical, washout facilities shall be located as far from drainage facilities as possible and additional inspections shall be conducted to ensure no illicit discharges have occurred (IUM).” If it is not possible to select a location far away from an inlet it is crucial to protect the inlets. A solution to this problem would be to add external inlet protection to ensure water does not enter the drain.