Field Trip

The City of Bradenton has two operational Aquifer Storage and Recovery (ASR) wells which store potable water. ASR well no. 1 (ASR-1) is located in the downtown area and ASR well no. 2 (IW-2) is located 6 miles east of Bradenton at the Bill Evers Reservoir Water Treatment Plant (WTP). This trip will visit the WTP which supplies potable water to both ASR wells. Potable water is injected during the wet season and recovered during periods of decreased supply and/or increased demand during the dry season. Recovered water is sent to the WTP for retreatment prior to distribution. The drinking water source is a reservoir formed by construction of a dam along the Braden River in 1939. The ASR operation is a small part of the City’s drinking water supply operations. The two wells are permitted to store up to a combined volume of 3.4 million gallons per day (mgd) although ASR storage and recovery volume is less than the total permitted. The WTP capacity to treat and distribute drinking water is 12 mgd.

Bradenton’s ASR-1 well was the first ASR well in Florida to successfully reduce arsenic concentrations in the ASR zone through use of a pre-treatment system. Well construction was completed in 2004 and the pre-treatment system was installed after arsenic sampled in the recovered water exceeded the drinking water standard. The use of a membrane system reduces dissolved oxygen (DO) to less than 1 mg/L, preventing excessive leaching of arsenic from the rock matrix. The City’s experience with the membrane system will be discussed.

ASR-2 installation was completed at the WTP in 2018. To prevent excessive arsenic mobilization at ASR-2 a different pre-treatment system was used. Prior to injection into IW-2 the finished drinking water goes through a degasification tower to strip out DO prior to injection, successfully reducing arsenic mobilization in the aquifer. The DO removal system is capable of treating up to 2 mgd.

All Florida ASR locations are monitored for physical and chemical parameters during recharge, storage, and recovery events. ASR well volume, flow rate, and pressure are continuously monitored and recorded; monitor well water levels or pressures are also continuously monitored and recorded. Water quality samples are taken from ASR and monitor wells monthly or twice per month depending on the parameter. Monthly summaries are provided to the Florida DEP and annual reports are often required.

The City’s ASR projects were co-funded by the Southwest Florida Water Management District (WMD) as part of their efforts to reduce the stress on drinking water supplies through the use of ASR and aquifer recharge projects. The ASR zone at both locations is the Suwannee Formation (limestone) of the upper Floridan aquifer. The wells are completed between 415 and 714 feet below land surface (bls). The Suwannee is a major source of drinking water in Florida. The Bradenton Bill Evers WTP is 50 miles and one hour south of the GWPC Tampa meeting location.

Manatee County owns the Southwest Water Reclamation Facility (WRF) to treat and reuse or dispose of reclaimed domestic wastewater. Reclaimed water may be used for irrigation particularly at golf courses and parks if the water meets public access treatment criteria. Through the use of high-level disinfection, low levels of biological activity are achieved as measured primarily by fecal coliform bacteria sampling.

During the dry season (winter and spring) the majority of reclaimed water is reused, but during summer and fall, and during other times of wet weather, the excess reclaimed water is injected. Excess water or water not meeting reclaimed standards is directed to a Class I injection well completed below the underground source of drinking water (USDW). A Class V ASR well and a Class V aquifer recharge well at the WRF accept only reclaimed water because they are completed in the USDW. Reclaimed water injected into the USDW qualifies as aquifer recharge under Florida DEP and WMD rules. The availability of a Class I, ASR, and aquifer recharge well at or very close to the same WRF which treats the water is unique in Florida and allows great flexibility to the County as it manages its wastewater disposal options.

The Class I well utilizes the Avon Park Formation (dolomite and limestone) of the upper Floridan aquifer, is completed between 1,067 and 1,659 feet bls, and was operational in the late 1980’s. The ASR well is completed in the Suwannee Formation (limestone) between 510 and 740 feet bls. It was first used in approximately 2005 but was only recently put back into operation after a long period of non-use. The aquifer recharge well is completed in the Avon Park Formation (dolomite and limestone) between 1,015 to 1,850 feet bls, similar to the Class I well. The Manatee County Southwest WRF is 50 miles and one hour south of the GWPC Tampa meeting location.

A Class I injection well was recently drilled and completed to dispose of surface water from a former phosphate mining processing facility. The Piney Point processing facility was built in 1966 and was subject to multiple spills and chemical releases including breaches of the dam for the reservoir which holds the majority of the surface water classified by the state as industrial wastewater. Ownership reverted to the state of Florida after the prior owner filed for bankruptcy. A permitting effort in 2014 by Manatee County to construct a Class I injection well met with little public support and the application was withdrawn. A leak in the reservoir’s wall in 2021 resulted in the release of 200 million gallons into a stream leading to Tampa Bay. A renewed effort to permit an injection well was successful as the well construction permit was issued in December 2021. Construction was completed in November 2022, and the well was put on-line in April 2023.

The injection interval is the Avon Park and Oldsmar formations (limestone and dolomite) in the lower Floridan aquifer, with a completion depth from 1,933 to 3,400 feet bls. The well can inject up to 1.09 mgd. The Piney Point well location is 40 miles and 45 minutes south of the GWPC Tampa meeting location.