Flood Recovery and Pond Help
Water Quality Testing & Fish Health
Flood waters that have entered your pond are likely turbid (high in suspended sediment, can look cloudy) and polluted by contaminated runoff from the landscape (trash, bacteria, auto fluids and heavy metals, excess fertilizers and nutrients, and other hazardous materials). Water quality testing through certified wet laboratories and test kits can inform you if your pond water is safe for contact as well as for fish productivity. Untreated pond or stream water are never safe for drinking water.
The following standards and discussion relate primarily to recreational or fish ponds, which serve a different purpose than an engineered stormwater pond, which is designed for flood storage and water quality treatment.
- Many pollutants, including harmful bacteria, bind to sediments. If a pond has become turbid with suspended sediment, this could indicate additional water quality concerns. Ponds receiving flood waters should be tested for elevated bacteria levels before any recreational use (if it is a pond purposed for recreational use, and not stormwater treatment).
- Surface water (fresh not marine) can be a public or personal health risk for primary contact if fecal coliform is greater than 200 cfu/100 mL of sample, or colonies of Escherichia coliform (E. coli) exceed 126 cfu/100 mL of sample. In marine or fresh waters, contact with waters with Enterococci greater than 35 cfu/100 mL of sample can be a risk. Bacterial infections associated with fecal matter contact can include upper respiratory illnesses, rashes, eye inflictions, earaches and infections of open wounds.
- Dissolved Oxygen (DO) is critical for fish health, and 7 mg/L or greater is optimal for fish productivity. Results of 3-5 mg/L can cause stress on a fish and lead to further health issues or death; less than 2 mg/L is typically associated with a fish kill. Diffusers can be used to circulate pond water to increase DO. If DO continues to persist at low levels, this could be an indication of the presence of organi waste (high BOD) in surface waters and excess fecal bacteria.
- pH influences fish health and should be maintained between 6.5 and 8.0.
- Settling time will typically decrease high total suspended solids (TSS) concentrations. As flood waters recede, and under less turbulent conditions, TSS results should be less than 60 mg/L or potentially 1/3rd of the incoming water’s TSS concentration. Another way to measure clarity of water, and potentially what is clouding the water, is visibility. Ideal depth visibility for fish ponds is between 12 and 30 inches.
- High water events allow stocked fish to escape impoundments (emigration) and may introduce undesirable fish and invasive species (immigration). Both emigration and immigration of aquatic species can significantly impact the fishery. For guidance on monitoring the fishery and stocking fish refer to Clemson Extension’s fact sheets https://hgic.clemson.edu/ and the Southern Region Aquaculture Center at https://srac.tamu.edu. Aquaplant is a good resource for identifying undesirable aquatic plants (and more) that may have immigrated to your pond.
Structural Integrity Questions
**If you believe your dam will fail or that there are public safety risks, please call 911.**
When examining your dam for potential failure, look for cracks and seeping, as well as if water is discharging around the pipe versus through the pipe. DHEC can be contacted with concerns with your dam at 1-866-246-0133.
It is recommended to safely and slowly lower water levels. Too quick of a release of volume accumulated from flooding, could put increased pressure on your dam.
Reconstruction Considerations & Resources
Especially given the dozens of dam failures across the state following the flood of 2015 and hurricane Matthew in 2016, it is important for emergency management for agencies to know where ponds and risks of failures exist. If you are considering reconstruction of an unpermitted pond, you are required to seek a permit if your pond's embankment or dam meets any of the following conditions:
- Greater than or equal to 25 acre-feet in height measured from the elevation of the natural stream bed or lowest point outside the dam;
- Greater than or equal to 50 acre-feet in impoundment capacity;
Or if failure would lead to significant loss of property or potentially loss of life.
Information for repairing/altering existing dams that exceed the 25 ft/50 acre-feet exemptions: https://www.scdhec.gov/Environment/WaterQuality/DamsReservoirs/ProcessDescription/.
“Ponds – Planning, Design, Construction” handbook from USDA (1997) provides excellent guidance on pond designs if you are considering reconstruction. It can be downloaded at https://www.extension.org/mediawiki/files/3/3c/ponds.pdf. The USDA Natural Resources Conservation Service offers financial assistance for agricultural producers to build or re-build water management structures, including ponds. Information should be sought out online at http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/programs/?cid=stelprdb1048817 or by contacting your local NRCS office.