County seeks cheaper sewage disposal deep underground

10,000-foot injection well could change how Miami flushes

Miami Herald 4/8/16

Due to changes in state law, Miami-Dade’s water and sewer department has nine years to stop pumping most of the 300 million gallons of treated waste generated each day miles out into the ocean through outfall pipes. Much of that waste water, called effluent, has to be highly cleansed and re-purposed. But in a county with more than 2 million users, officials say the only way to fully comply with the new law without breaking the bank is to dispose of up to hundreds of millions of gallons of treated waste by shooting it into a cavernous, confined saltwater zone down below South Florida’s drinking supply.

Geologists are exploring the murky world beneath the county’s oldest sewage treatment facility on Virginia Key in search of a safer, cheaper method of sewage disposal. They believe if they can inject effluent farther away from South Florida’s aquifers and deep into the bowels of the earth, they can dramatically lower the cost of doing business.

But some are still wary of injection wells, which under different classifications can also be used to dispose of industrial waste or for fracking. Florida is the only state that allows Class I municipal injection wells for effluent, according to the Environmental Protection Agency.  In Miami-Dade, memories of municipal wells in South Dade leaking ammonia into the brackish Upper Floridan aquifer are still fresh. Those leaks didn’t contaminate any drinking water supplies, but they did push the county into a legal settlement with the federal government, and force the state to change laws regulating Class I injection wells to require a high — and expensive — level of treatment for injected effluent.

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