Concerns Related to ASR Wells in Florida



Concerns Related to ASR Wells in Florida

Compiled by Jim Egan,

Executive Director, Marine Resources Council

1) The proposed ASR wells in Rockledge, like those throughout Florida, would fully treat the water being injected to full drinking water standards with a few minor exceptions such as it being saltier then drinking water and having a small amount of suspended solids. Not normally tested for, but known to sometimes be found in this type of wastewater are endocrine disrupters such as birth control chemicals, caffeine, prescription drugs, fire suppression chemicals and a host of others that are found in very trace amounts but can cause human and animal impacts at even trace amounts.

2) The biggest problem found in ASR wells in Florida is that they introduce water containing oxygen into groundwater that does not contain it and that causes Arsenic to be removed from the aquifer's rock formation and introduced into the groundwater. (In parts of western Florida the oxygen has also removed radioactivity from the surrounding rocks and introduced it into the groundwater but this not likely on the east coast of Florida) ASR well water can be treated to remove arsenic before it is used but it still leaves a high percentage of arsenic-contaminated water in the aquifer. Currently Fl DEP is holding ASR wells to a limit of 10 ppb of Arsenic not only when it is pumped out but also the water remaining in the aquifer, for the purpose of not allowing the introduction of new oxygen rich water to continue to raise the concentrations of arsenic in the groundwater indefinitely. This has caused problems for some operators of ASR wells who have difficulty keeping their groundwater below the 10 ppb limit and can cause the very expensive wells to be shut down. US Army Corp studies of south Florida ASR wells found injected water tended to convert nitrate to ammonia, exceeding the Florida Class I and III surface water standards (20 ppb), the injected water dissolved gypsum to release sulfate (within current standards) and increased hydrogen sulfide concentrations in the groundwater, though not beyond current standards (US Army Corp 2004).

3) ASR wells create groundwater changes that can result in direct, indirect and secondary and cumulative impacts to marine species according to (Bacchus 2001) Bacchus found the man-made groundwater changes could result in significant physical, chemical and biological changes in the marine ecosystem including 1) predisposing organisms to disease via decreasing their resistance, 2) the introduction of new pathogens into the groundwater and surface waters they come in contact with, 3) promoting the rapid antagonistic evolution of microbes, and 4) introducing hazardous chemicals, including endocrine disrupters.

4) ASR wells often boast high "efficiency rates" approaching 100% or even greater. This is a very misleading calculation. In Florida's rock formations it is unlikely that anything greater than between 50%-75% of the water that is introduced is recovered in the next cycle of pumping (SJRWMD 2004). Typically a new well pumps millions of gallons of water into the aquifer again and again and is capable of withdrawing only a small fraction for several years. The US Geological Survey of the US Dept of the Interior studied ASR wells in the Floridan Aquifer in Florida and reported in 2004 that well efficiencies ranged from a high of 78% in Palm Beach to a low of 3% in St Lucie County. About 30% of the wells in south Florida had not exceeded 10% recovery (USGS 2004). USGS testing of proposed ASR wells for the everglades had efficiencies of 3.1%, 2.7% and 7.2% (Bacchus 2003). After pumping in millions of gallons and only recovering a small fraction over and over again, eventually most of the wells start to recover more of the water they pump in each time and more of the water that was pumped in during previous efforts. High efficiency rates are calculated by comparing simply how much water is pumped in at one time with how much is withdrawn later even though the water being withdrawn later may contain a high percentage of water not recovered during previous years of pumping or water that was never pumped down in the first place (SJRWMD 2004). This reinforces the concern that the excess of water that remains in the aquifer has increased opportunity to be contaminated by Arsenic. It also increases the likelihood that some of the water is never recovered and can move laterally into other wells, laterally down the aquifer into natural ocean outfalls of the aquifer or vertically through overlying fractured and water-soluble limestone into surficial aquifers, lakes, canals, rivers and the Indian River Lagoon.

5) Commonly, injected water is relatively fresh compared to the salty groundwater it is being injected in to and as a result the injected water is less dense and can have a tendency to rise and find breaks and cracks in the overlying confining layers and move up into other aquifers or into surface waters. Recent studies found even much more deeply injected wastewater was found to have moved upward through thicker confining layers into drinking water aquifers. McNeill (2001) found deep well injected water passed through confining layers and reached the Floridan Aquifer at a rate 30 times faster than predicted and that the ultimate fate of where this wastewater moves to is unknown. McNeill (2001) also concludes the uncertainty in the subsurface geology and properties of the confining layers provides no reasonable degree of certainty for the protection of underground sources of drinking water and nearby fragile marine and land-based ecosystems. Uncertainties in the subsurface geology is very applicable to Brevard County since the DB Lee well in Melbourne was found to transmit its deeply injected water into the drinking water aquifer, the Floridan (Fl DEP). There has also been evidence to suggest the Floridan Aquifer may have connections to both the surficial aquifer and the Indian River Lagoon in Central Brevard County.

6) Concerns about ASR wells from the National Groundwater Association include: What type of treatment is necessary to ensure that no pathogens will survive in groundwater? Will disinfection lead to the formation of carcinogenic compounds that will move to broader ground water areas? What information is needed to ensure that the water being recharged is geochemically and microbiologically compatible with native ground water? Unanticipated reactions may lead to poor-quality water, biomass formation, pathogen growth and well clogging. What monitoring will be required to ensure that unforeseen water-quality problems do not affect broader ground water resources? How will communities be assured that the recharged water will not adversely affect other aquifers or surface water bodies? (NGWA 2008)

7) Due to concerns like these the State of Georgia has banned ASR wells into the very same Floridan Aquifer

References

(USGS 2004) US Geological Survey of the US Dept of the Interior Fact Sheet 2004-3128 Nov. 2004

(SJRWMD 2004) Pyne, R, Aquifer Storage and Recovery (ASR) Issues and Concepts

(Bacchus 2001) Bacchus, Sydney, Endangered Species Update Vol 18 No. 3 2001

(Bacchus 2003) Bacchus, Sydney, Conduit Flow: Pathways to Poor ASR Recovery and Subsurface Water Contamination in Florida.

(McNeill 2001) A Review of Upward Migration of Effluent Related to Subsurface Injection at Miami-Dade Water and Sewer South District Plant

(FL DEP) Fluid Movement Associated with Class 1 Deep Injection Facilities in South Florida, Fl DEP website

(US Army Corp 2004) MIrecki, June, Water-Quality Changes During Cycle Tests at Aquifer Storage Recovery (ASR) Systems of South Florida. June 2004

(NGWA 2008)

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