Contaminated Stormwater Guidance
When there is heavy rainfall and flooding our waterways may not meet State water quality standards. Flood waters pick up contaminants from roadways, industry, agriculture and residential yards. In addition, sometimes septic systems and sewer systems become inundated with storm water and/or rising groundwater that seeps into the sewer infrastructure. When this happens, wastewater may overflow and comingle with floodwaters. This contaminated water may enter rivers, lakes or streams which may affect water quality and public health. People can be exposed to infectious diseases in the spilled wastewater through direct contact, inhalation or food which has been contaminated.
The overall impact of wastewater discharges to surfaces waters is fortunately temporary. Our bays, rivers and gulf are constantly moving, which results in dissipation and dilution of wastewater contaminants in a few days. Persistence of increased levels of bacteria depends on many factors such as rain intensity, volume of any wastewater released and the receiving water body flow rate. For small water bodies receiving wastewater spills, the utility company may be able to remove the contaminated water and route it for proper treatment if feasible, but this is usually challenging in storm or hurricane conditions when the sewer systems are already overloaded. However, bacteria levels do subside over time through natural attenuation. As a general guideline, bacteria levels can remain elevated for at least three days after a significant rainstorm.
Is it safe to swim?
Public bathing places such as coastal beaches are routinely monitored (currently weekly) by the Department of Health under their Healthy Beaches Program to ensure public safety but may pose an increased risk after heavy rainfall. When the Department of Health confirms that bacteria concentrations exceed levels safe for swimming, they issue health advisories or warnings and post signage. After the next samples meet standards for public beaches the advisories or warnings are removed. The public beaches in Hillsborough County monitored by the Department of Health are: Bahia, Ben T. Davis North & South, Cypress Point, Davis Island, Picnic Island and E.G. Simmons. The public may contact the Health Department regarding any Hillsborough advisories in effect by calling (813) 307-8044 or using the online system which includes data across Florida, at http://www.floridahealth.gov/environmental-health/beach-water-quality/index.html
Swimming in areas not covered by the Healthy Beaches program poses additional risk, particularly after heavy rainfall. Many of these waterways are part of EPC’s extensive monitoring program which includes approximately 260 sites sampled monthly or quarterly based on location. However, with 125 miles of major tributaries and 400 square miles comprising Tampa Bay, our monitoring is limited and only representative of the conditions at the particular sample site and time. And, as with all bacterial samples, including those of the Department of Health, lab analysis requires time for bacterial growth to determine concentration during which time there may be rainfall or other conditions affecting the waterway post sampling. Therefore, one should assume that the waterways and beaches may be impacted after heavy rainfall and take precautions to limit direct contact with standing water or any water body after heavy rains due to the potential for pollution.
What you can do:
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Limit direct contact with standing water or any water body after heavy rains due to the potential for polluted runoff, sewage overflows and other safety issues due to the possibility of the presence of debris, wildlife such as snakes and downed powerlines.
