https://www.theweathernetwork.com/news/articles/miami-dade-florida-septic-tanks-groundwater-sea-level-rise/122622
[Not just for weeping bed systems. Sea Level Rise (SLR) will also be a
problem for sewage lagoons which can be breached by a storm surge or
pump-out holding tanks which could be wrenched loose from plumbing
connections allowing contents to escape close to residences.
images and video in online article]
Florida sea level rise big problem for septic tank systems
Dr. Mario Picazo
Meteorologist, PhD
Tuesday, January 15, 2019, 5:59 PM - Florida's Miami-Dade County relies
heavily on septic tanks that require constant maintenance, but a new
county study reveals that the situation will require even more attention
as sea levels continue to rise.
Since 1994, sea levels have risen more than 10 centimeters and are
expected to increase an additional 5 to 15 centimeters by 2030. The rise
of sea water has brought higher groundwater levels in some areas and
those will continue to rise over the long term.
When groundwater is higher than usual, septic systems cannot function as
designed, with an immediate threat to public health. But there are other
negative impacts, like the contamination of fresh water aquifers which
provide potable water for thousands of residents.
Septic systems treat and dispose of wastewater from individual
properties. The wastewater from kitchens, bathrooms, laundries, and
other sources is gradually treated by allowing the wastewater to pass
through the septic tank and, subsequently, the drain field. A total of
108,000 properties in Miami-Dade County still use septic tanks, and
105,000 of those are residential.
The malfunctioning of many of these septic tanks also means smelly air
for residents, and as global warming-induced sea level rise continues to
increase, problems are only expected to get worse in the area. According
to the report, by 2040, 64 per cent of county septic tanks (more than
67,000) could experience issues every year, affecting residents and
having a major environmental impact in the region.
As groundwater levels rise, low-lying areas will be impacted first,
although the county has already been informed of close to 1,000 property
tanks that are failing under current conditions. New regulations in the
county require that the layer of dirt underneath the tank that carries
out the final filtration be around 60 cm deep. This is hard to come
about since there is not so much dirt between a home and the groundwater
in many areas of South Florida.
Another problem is that rising groundwater levels make the soil soggy,
and soggy soil is not an efficient filter for waste water. During heavy
rains, high tides or elevated storm surges, the situation is even worse,
as the higher flow pushes contaminated water back into residential areas.
Experts agree that the best solution would be to extend the sewer
system, despite the planning time scale and investment. According to
County Chief Resilience Officer James Murley: "Ripping out every septic
tank and laying down pipes to connect the homes to the county's sewer
system won´t be cheap." The latest price tag on doing so was a whopping
US$ 3.3 billion just for private properties. Commercial properties would
add an extra US$ 230 million to the bill.
Commissioner Rebeca Sosa is clear: Action is needed as fast as possible
and financial assistance from the state and federal government
essential. For now however, anyone who wants to connect their property
to the general sewer system has to pay their own bill. The investment
estimate is an average $US 15,000 per home, although in more vulnerable
areas like Pinecrest the price could escalate to near $US 50,000.
For now, the report points out that beyond borrowing money to improve
the situation of tanks, the county should continue to collect a per-home
fee or establish special taxing districts to spread the cost among the
affected neighborhoods.
