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

Highlights:

• Miami-Dade is drilling the state’s deepest municipal injection well on Virginia Key
• Geologists are studying whether treated sewage can be injected deeper into the earth
• The project is part of a $5.2 billion effort to overhaul Dade’s sewage disposal system

Just off a winding back road on a barrier island in Biscayne Bay, engineers and scientists are on a mission to flush to the center of the earth.

Using a custom, lime-green drill rig, they have bored a first-of-its kind industrial well into the ground 10 feet at a time and plunged to a depth of 10,000 feet. They are digging into prehistoric rock formations, deeper than any municipal government has before in search of a better solution for a $5.2 billion problem:

The Atlantic Ocean is no longer a suitable receptacle for sewage.

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.

The decades-old practice is steeped in science, but polarizing. It also requires expensive cleansing, in part because effluent from existing wells in south Miami-Dade and elsewhere has escaped containment and seeped upward in the past.

But with lessons learned, 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.

“If we can find permeable zones down there that we can inject into, it’s separated from any kind of environment by thousands of feet,” said Virginia Walsh, Miami-Dade’s senior professional geologist and leading expert on injection wells. “We’re looking for safer alternatives.”

The unprecedented quest on Virginia Key began in late 2014 after county commissioners awarded a $20 million contract to Youngquist Brothers to oversee the dig as part of a larger movement to comply with the state’s looming ocean outfall regulations. Following seismic testing by the U.S. Geological Society to map out the faults below ground and select an ideal location — a step not required by law — the Fort Myers-based contractor created a custom rig capable of drilling a well nearly two miles deep and holding more than 1 million pounds in concrete, steel and reinforced fiberglass piping.

The drilling started with a hole large enough to hold a Hummer H3, and narrowed down diameter through 3,000 feet . Eventually, that’s where the well will open up and begin pumping up to 20 million gallons of effluent and other treated waste each day into Southeast Florida’s unique “Boulder Zone,” where it is expected to mix with underground seawater and, after hundreds of years, filter out into the Florida Straits.

But instead of stopping there, Youngquist Brothers kept drilling a smaller pilot hole down another 7,000 feet into earth that last saw the sun 90 million years ago. It’s down in these depths, where heat from the earth’s core warms a salty soup with a salinity like the Dead Sea to 130 degrees fahrenheit, that scientists are recording video and taking and testing rock and water samples in the hopes of finding a deeper, safer sewage receptacle.

Deep caverns have been documented in Florida’s geology. Ideally, geologists hope to find another porous subterranean zone capped and effectively sealed by a dense rock called anhydrate. If they succeed, county engineers will factor the information into the design of other planned injection wells. Today, the county has 21 injection wells in north and south Dade. By 2025, they expect to more than double that amount at a cost of $635 million, including a second injection well of standard depth to be drilled next to the 10,000-foot well on Virginia Key.

“These are just the first two wells” on Virginia Key, said Gerrit Bulman, a senior project manager for CH2M, which is coordinating the county’s plans to end ocean outfall dumping. “We’ll probably have nine here by 2025.”

Walsh, who focused her doctorate thesis on injection wells, says research clearly shows pumping waste into the earth to filter slowly deep into the ocean over centuries is “far, far safer” and environmentally friendly than dumping sewage into the ocean in a concentrated area. 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.

Harold Wanless, a geology professor at the University of Miami, said he hopes the county finds deeper, safer pockets of earth for the massive pool of sewage created every day in South Florida. But he doubts it will. And even if it does, Wanless is among the skeptics who believe gthe county is better off spending the money to reuse all its waste water, and there’s a chance that today’s science governing the use of injection wells may still prove flawed in the future.

“It’s 100 million gallons a day or more,” he said. “That’s not a dribble.”

When the south Dade wells leaked, University of Miami geologist Don McNeill studied the problem as a hired expert for the Sierra Club and found that contractors had built injection wells too shallow. But McNeill, who has been out to the county’s deep injection well site and gone over some of the research, says injection wells are sound when designed and built correctly. He believes the county’s aim to find a better reservoir for human waste — which has to go somewhere — is a sensible idea.

“The 10,000-foot well is exciting and different. People should be aware of what’s going on,” he said. “But I think they’re taking the right approach, collecting data and doing an exploratory approach to find the safest place.”

Drilling of the two injection wells currently planned at Virginia Key should be completed by the end of the year. And the county’s two first injection wells at the site are expected to open by 2018, when another law kicks in requiring a dramatic cut to the amount of sewage-related nutrients pumped into the ocean. Additional wells are planned in the south, north and at a new facility in west Dade.

Meanwhile, the deep well research will continue. Walsh says new information gleaned from the Virginia Key dig will be incorporated into new injection wells as they’re designed. And when the research is over, the deep pilot hole will be back-filled with cement up to around 3,500 feet before the standard injection well is opened for use.

Depending on what they find, the county could save millions, and the millions living in Miami-Dade could put some extra distance between themselves and the millions of gallons of waste they produce every day.

“We’re truly making history here,” said Walsh. “This whole project is cutting edge.”

BY DAVID SMILEY  dsmiley@miamiherald.com

Attached link

Taxonomy

• Effluent
• Sewage Treatment
• Sewage