Engineering & Mining Journal

JUL 2018

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Page 34 of 75

WATER REUSE STRATEGIES JULY 2018 • E&MJ 33 Currently, numeric nutrient-water cri- teria have been developed for at least two or more waterbody types in Florida, Min- nesota, New Jersey, Rhode Island, Wis- consin and Hawaii. In many other states, there are numeric limitations established for some, but not all, waterbodies. Some states are still developing their numeric nutrient-water criteria in relation to nitro- gen and phosphorus, while other states — namely Connecticut, New York, Georgia, South Carolina and West Virginia — are projected to have additional numeric nu- trient requirements by 2020. "Based on the trends over the past 15 or so years, I believe new requirements will continue to be developed and will become more stringent and quantitatively based over time," Dinges said. "In the years to come, all states are expected to have a complete nutrient criteria developed for each waterbody type within the U.S." The Florida Case "Historically, Florida has suffered from eutrophication of its waters resulting in functional impairment in many of its ma- jor water bodies. These include notable water bodies such as the Caloosahatchee River, the Indian River Lagoon and Tampa Bay," Dinges said. He added that over the past decade, Florida has made significant strides in tackling the issue, resulting in the development of both nitrogen and phosphorus numeric limitations for specif- ic regions and waterbody types across the state. These include numerous springs, rivers, lakes and estuaries from the Florida Panhandle down to South Florida. There are six watershed regions in the state, which are grouped by shared geological, hydrological and precipitation characteristics. Each of these regions has established default-nutrient criteria, which governs the nitrogen and phospho- rus discharges. "In Central Florida, for example, there are a number of phosphate mines within a phosphorus-enriched geological area," Dinges said. "The nutrient limits in this area are a little different, since phos- phorus is latent in the soils within the watershed. When looking at other regions in the state, there are more stringent standards because the nutrients natural- ly latent in the soils and geology are not as significant." He highlighted that numeric nutrient water criteria are particularly important for mines that produce nutrients. "Typically, mines will have water discharges, some of which are released into surface waters. The discharge of nutrients, as well as the limits imposed by regulation and the changes to this limit over time, really con- stitute a need for mining operations to find workable solutions to mitigate the impact these changes will have over the operation during the course of its life-of-mine." Water quantity and availability of supplies are also critical considerations for mines. In Florida, water supplies are classified as insufficient to meet future demands within the eastern portion of the Suwannee River watershed, placing greater strain on mining companies in the region to carefully manage their own wa- ter supply to ensure they do not place a further burden on natural resources. A recent project success related to the development of discharge water reuse is in the Upper Suwannee River watershed. While the Upper Suwanee River is not verified impaired for nutrients, any nu- trients discharged in the upper river flow downriver, which can significantly impact the health of the river. In fact, a portion of the lower Suwannee River has been veri- fied for nutrient impairment. The mine where this project took place is regulated by National Pollutant Dis- charge Elimination System (NPDES) per- mit. This permit regulates discharges at the 100,000-acre phosphate mine and while nutrients are not limited, the mine must sample its discharge water and re- port the results to the state of Florida. He explained the mine operates with- in a watershed area that receives a nota- ble amount of precipitation, typically 55 inches (in.) to 60 in. annually, with fre- quent heavy storms that cause flooding. "The Suwannee River is designated as an Outstanding Florida Waterbody by state law. It is a pristine river, with essentially very few point discharges into the water- body. As a result, there is a big spotlight on its operation and is monitored very closely by the regulatory authorities and special interest groups." Also, the Florida Department of Envi- ronmental Protection (FDEP) is running the Florida Springs Initiative, which aims to restore and enhance more than 300 natural springs across the state, many which are in the Suwannee River region. Dinges said this is an important program, since water flows out of the Floridan aqui- fer system through the springs, contribut- ing to the flow of the Suwannee River. "The Floridan aquifer system is the principal source of water supply for cit- ies, agriculture, mining, and other uses, and is the primary subject of the water supply planning efforts in the region," Dinges said. Dinges asserted that the quality and quantity of the aquifer must be protected and restored in order to ensure the health of the springs. Moreover, the springs in the Suwannee River region contribute a significant portion of the flow to the Su- wannee and other rivers in the region, further highlighting the importance of managing the aquifer system. "The Suwanee River communicates with the aquifer system significantly with- in this landscape, and mining operations and their discharges, therefore, operate within a very sensitive environment," Dinges said. He pointed out that the The Upper Suwannee River in Florida flows through phosphorous-enriched geology.

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