Miami-Dade County Begins to Address Thousands of Septic Tanks Failing Due to Sea Level Rise

Sea level rise has many negative consequences on coastal communities. One of them is causing septic systems to fail.

How dow this happen? As sea level rises, saltwater migrates inland underground through porous rock, such as limestone. As it moves, the denser saltwater forces the freshwater water table to rise toward the surface. If the water rises high enough, it can saturate soils near the surface.

Septic systems take wastewater from a home and sends it to a concrete box buried underground. From there, the effluent is distributed underground through soils that remove impurities. If the soil is already saturated, however, it can’t absorb the wastewater and remove the impurities. As a result, the untreated wastewater can emerge and pollute the land and streams, rivers, estuaries, bays and other bodies of water.

Miami-Dade County in South Florida has thousands of septic systems that are failing due to rising seas. The problem is so bad experts say some of the the septic systems are sending untreated wastewater into Biscayne Bay, where it’s killing fish and other marine animals.

To fix the problem, county officials broke ground on a project to disconnect thousands of homes from their currently failing or at-risk septic systems and hook them into the municipal wastewater treatment system. The county has $230 million to invest in converting 13,000 of the counties 120,000 septic systems over the next five years. Their immediate goal is to address the 9,000 tanks that they believe are polluting Biscayne Bay.

Miami-Dade has funding to bring sewer lines up to property lines, then it’s up to property owners to cover the cost of new pipes to hook into the municipal wastewater system and to remove the failing septic tank. Estimates are real estate owners will have to spend $10,000 out-of-pocket to do this. The county has state funds available to help low-income residents with the expense.

Oddly enough, the county is still issuing permits for the installation of new septic tanks. County officials told the Miami Herald that it continues to issue permits because some Miami-Dade residents can’t afford to tie into the municipal wastewater system and because developers are building homes in places where municipal sewer lines haven’t been installed.

Aaron Stauber, an environmentalist and board member of Miami Waterkeeper, applauds the county for starting to address the septic system issue. He told the Miami Herald, however, that the county should only allow development in areas that already have sewer service or force the developers to install new sewer lines.

Coastal real estate owners who have properties served by septic systems clearly need to keep abreast of any changes to regulations that govern their septic tanks. Buyers in those areas need to know whether a property of interest is served by municipal wastewater systems or septic tanks. They also need to know if the septic tank is in good working order and if the local government has any intention of forcing homeowners to tie into the municipal system.

The Threat of Flooding in Coastal Communities Rises as Sea Level Rise Lifts Water Tables

When Tropical Storm Eta soaked South Florida with torrential rains in November, many property owners far inland were shocked to see streets and homes flood in their neighborhoods. Experts say that the extreme flooding was due to the enormous amount of rain that fell on land already saturated by heavy rains that fell in October. They also said that the nearly 75-year-old canal system built to drain what had for been Everglades swamplands was unable to cope with the volume of water.

Sea level rise was part of the problem, too. The drainage canals rely on gravity to transport water from land to sea. As sea levels rise, the difference in height between water on and under the land and the ocean is becoming narrower. As a result, floodwaters don’t flow as quickly downslope to the sea, and, during extremely high tides, sea water actually tries to rush inland through the canals.

Another reality of the canal system is that if the region is experiencing higher than normal “king tides” during a storm, authorities who oversee the drainage system have to close gates to keep seawater from rushing up the canals. During heavy downpours, floodwaters can get caught behind the gates and, with no place to go, they accumulate and flood the land.

Sea level rise poses another less obvious threat that’s right under our feet. As the sea rises, water pressure causes it to migrate inland underground through porous rock and/or soil. The pressure from the salt water, which is heavier than fresh water, forces the fresh water upward, effectively raising the water table.

This can have several negative effects. When the water table rises, it saturates the land. When it rains, the water that falls cannot be absorbed by the soil and flooding results. Another negative effect is that the groundwater itself can rise up to the surface and create flooding.

An even nastier effect of rising water tables is that floodwaters can, as was experienced in South Florida, flow into the wastewater treatment system through manhole covers and broken pipes greatly increasing the flow to wastewater treatment facilities. This influx of water can cause the facilities to lose efficiency or fail all-together. The higher water tables can also cause on-site septic systems to fail. Both problems can result in the release of stinky, and potentially infectious sewage into floodwaters and onto the land.

The flooding Eta brought to South Florida isn’t unique to the region, and it illustrates a problem that many coastal communities and real estate owners are coping with now or will confront soon as seas continue to rise.

Many coastal communities from Florida to Oahu are racing to cope with the problem of sea level rise-induced rises in water tables. A superb article by Grace Mitchell Tada titled “The Rising Tide Underfoot” recently published in Hakai Magazine discusses in detail how rising seas are threatening Oahu, Hawaii. As Dolan Eversole, a management coordinator with the University of Hawaii Sea Grant College Program, told the reporter: “Sea level rise does not look like the ocean coming at us. It looks like the groundwater coming up.”

In South Florida, seawater is migrating inland through porous limestone. In Oahu, it moves through basalt rock. The end result is the same. According to the article, higher water tables are wreaking havoc, flooding residential neighborhoods and commercial and industrial areas. It’s also threatening critical infrastructure, such as roads, pipes that carry fresh water, wastewater, and gas, and underground wires that carry electricity and information.

As the groundwater rises, it also has the potential to release and spread toxic substances, such as oil and chemicals, deposited in the soil, which could lead to environmental catastrophe.

As sea levels continue to rise, groundwater issues will pose an even greater threat to at-risk communities.

Owners and buyers of residential and commercial real estate in coastal areas can’t ignore the threat posed by sea level rise-heightened water tables. The flooding can not only damage their property, it can make driving and communicating difficult, it can cause a spike in maintenance costs and in tax and insurance rates, it can discourage buyers from entering the market, which will drive down prices, it can discourage tourism and other business activity, and it could ultimately lead to lenders and insurers pulling out of the local market altogether, which would be the death knell for a healthy real estate economy.

Unfortunately, there is no easy way to combat rising water tables. For example, if you construct sea walls or natural berms, the seawater can easily migrate under and behind them through the porous rock and soil. With this in mind, owners and buyers of real estate in areas at-risk of rising water tables, need to perform due diligence and determine the level of the threat — has it happened in the past, is it happening in the present, and/or how far in the future will it happen. This information is critical when you decide if you can handle the risk and whether it’s worth taking on to begin with.

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