Providing new water to residents in fast-growing southern Hillsborough County could be aided by injecting old water into the ground.
The new water will be fresh from the aquifer drawn to the surface by additional wells run by Tampa Bay Water, the regional water supplier. The old water will be treated wastewater injected at sites several miles away and pushed down 1,000 feet below the surface.
At least that’s the plan. But it will come at a price that is a matter of contention.
Hillsborough County and Tampa Bay Water dispute how much the county should be paid for giving up its reclaimed water.
“We’re not real close on the value,” George Cassady, Hillsborough’s assistant county administrator for public utilities, told commissioners last month.
The proposal calls for Hillsborough County to inject a total of 10 million gallons of reclaimed water into the ground each day at a series of four wells west of Interstate 75 near the county’s coastal areas.
Tampa Bay Water says studies show the injections do two things: create a barrier preventing saltwater from intruding into fresh groundwater, and increase aquifer levels at inland locations several miles away.
Those aquifer level increases mean Tampa Bay Water can seek permission to pump additional groundwater. The permission would come from the Southwest Florida Water Management District, which requires new withdrawals to be offset by a separate action resulting in a positive effect on the aquifer.
If the district grants the permit, then Tampa Bay Water would withdraw 6.1 million gallons of water from the aquifer at new production wells on county-owned property known as the AG-Mart site — a former farm that is east of I-75, roughly 8 miles from Apollo Beach.
Nobody disputes that more water is needed for southern Hillsborough County. Businesses and homeowners in the area south of the Alafia River remain on lawn-watering restrictions and each dry season residents complain about the dribbling flow from their taps.
But withdrawing more groundwater isn’t a singular solution.
In the 1990s, the water management district designated southern Hillsborough and the vicinity to the south as a caution area. Pumping had dropped underground water levels resulting in saltwater intrusion into the Upper Floridan aquifer. The hardest hit areas totaled 708 square miles along the coast of southern Hillsborough, Manatee and northwestern Sarasota counties, according to the water district.
The county started injecting reclaimed water underground with a single injection well in Apollo Beach in 2015. The strategy is to present an underground bubble or wall of water to prevent saltwater from migrating inland from the coast. Since water naturally flows to the west underground, the treated wastewater is not considered a threat to the drinking water supply to the east. The county began operating another injection well in northwest Hillsborough in 2021.
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The effort has an ancillary benefit. Sending treated wastewater underground helps protect Tampa Bay. Annually, each county well injects 9 tons of nutrients below the surface instead of allowing it to spill into the bay, said Jeff Greenwell, a manager for the county’s environmental services division.
Sending the water underground also will help the county meet a state law prohibiting so-called wasteful discharge of reclaimed water by 2032.
Currently, Hillsborough operates five plants generating 45 million gallons of reclaimed water each day. The wells inject 5.5 million gallons of that underground; 26 million gallons are used for irrigation and the rest, about 13.5 million gallons, goes in the bay.
The proposal being debated now is to have some of that reclaimed water offset drawing future tap water from underground.
There is, however, the matter of price. The capital cost of the four injection wells is estimated at $17 million, with the water management district anticipated to pay half.
But the county and regional utility — the two agencies promoting the idea – can’t agree on how much that reclaimed water is worth.
An initial estimate from Tampa Bay Water put the value at 69 cents per 1,000 gallons. Hillsborough County thinks it should be more, but hasn’t made a public counter-offer. It also is hesitant to commit for 30 years.
“At the end of the day, this has to work for everybody or it doesn’t work at all,” said Hillsborough Commissioner Mariella Smith, a member of Tampa Bay Water’s board of directors.
Sixty-nine cents for 1,000 gallons might seem like a minute number over which to argue, but consider Hillsborough could be pumping as much as 2.6 billion gallons of wastewater underground each year. Over the length of a 30-year contract, even after discounts, it amounts to $45 million credited to the county by Tampa Bay Water in today’s dollars.
At least one member government of Tampa Bay Water, Pasco County, thinks the offer might be too generous. The price estimate is based on the rates charged to residential customers instead of less expensive charges assessed to bulk users.
“We’re uncomfortable with that,” said Pasco Commissioner Kathryn Starkey.
If the two sides can reach an accord on economics, the project still isn’t a guarantee. Tampa Bay Water also is considering other water-producing alternatives.
Tampa Bay Water has kicked around this idea for at least 18 months. If the agency and county can’t come to terms by June, Tampa Bay Water indicated it would shelve the project and turn its focus to two remaining alternatives for increased water production: expanding its seawater desalination plant or treating additional river water skimmed from the Alafia and Hillsborough rivers and Tampa Bypass Canal.
“Plenty of time is not something we can say,” said Pinellas Commissioner Dave Eggers, chairman of Tampa Bay Water’s board of directors.
The additional water is not scheduled to be available until 2028.