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projects > integration of seismic-reflection and well data to assess potential impacts of structural anomalies and stratigraphic features on alternative Floridan Aquifer system water supply, Broward County

Integration of Seismic-Reflection and Well Data to Assess Potential Impacts of Structural Anomalies and Stratigraphic Features on Alternative Floridan Aquifer System Water Supply, Broward County

image showing lithostratigraphic units in the study area, generalized geology, and correlation to hydrogeologic units
Figure 1. Lithostratigraphic units in the study area, generalized geology, and correlation to hydrogeologic units. Subdivisions of the Arcadia Formation and Avon Park Formation are informal. Modified from Reese and Richardson (2008). [larger image]

Study Area: Broward County, Florida
Period of Project: July 2012 through September 2015
Principal Investigator: Kevin J. Cunningham
Cooperator: Broward County

Objective:

(1) Define the regional structural and stratigraphic setting of the middle and upper parts of the FAS in Broward County (fig. 1).

Background:

The South Florida Water Management Districtís 2007 Regional Water Availability Rule restricts southeastern Florida Biscayne aquifer withdrawals to pre-April 2006 levels. Furthermore, the State of Florida proposes elimination of ocean outfalls by 2025. In light of these policy changes, environmental stakeholders are pressing resource managers to expand use of the more deeply buried karst Floridan aquifer system (FAS) (fig. 1) as a water resource to satisfy water-supply needs, and as a reservoir for the disposal of wastewater via Class I deep injection wells and injection of reclaimed water. Water-supply options that make use of the FAS include (1) the utilization of the brackish upper FAS as source water, (2) aquifer storage and recovery (ASR), and (3) reverse osmosis (RO) desalination. Some water providers in Broward County have expressed reservations in developing the FAS as an alternative water supply based on a general lack of technical data and information regarding the sustainability of the FAS as a source of water. Furthermore, the limited development of the FAS in Broward County has resulted in a shortage of quality hydrogeologic data on which to base models that can simulate anticipated changes that will result from future water-supply projects. Intensified economic development of the FAS as a sustainable water resource in Broward County will depend on reliable knowledge of the hydrogeology of the FAS for use by water managers and planners. Improving the accuracy of the current hydrogeologic framework of the FAS is essential to future modeling of the FAS's long-term capacity to support water-supply development. Two critical geologic elements that impact the efficacy of FAS water-supply withdrawal and wastewater injection are the structural and stratigraphic components of the FAS hydrogeologic framework.

Scope of Work:

Acquisition, processing, and interpretation of water-based seismic-reflection profiles (fig. 2) will be used to image deeply buried faults and karst-collapse structures (fig. 3), and more fully delineate hydrostratigraphy, lithostratigraphy, and sequence stratigraphy for the FAS in eastern Broward County. Five previously acquired seismic-reflection profiles located either in Broward County or northeaster Miami-Dade County will be used to enhance the seismic data base being acquired for this project. The new water-based profiles will be focused on a lithostratigraphic section that includes the FAS (fig. 1). Nearby FAS utility wells will provide sufficient data to make a reasonable correlation between hydrostratigraphy and lithostratigraphy in the wells, and seismic stratigraphy on the profiles.


location map of project area in southeastern Florida profile of very large karst collapse structure located beneath Biscayne Bay in southeastern Florida
Figure 2. (left) Location of project area in southeastern Florida. The cyan lines show locations of water-based seismic-reflection profiles that will be acquired in canals during early 2013. The orange lines show locations of existing water-based seismic-reflection profiles that will be included in the scope of the project, as well as the USGS G-2984 upper Floridan aquifer test corehole completed in 2012. [larger image] Figure 3. (right) Example of a very large karst collapse structure located beneath Biscayne Bay in southeastern Florida. This collapse structure is approximately up to 3 miles in width. Faults (semivertical yellow dashed line) cross confining units that separate permeable zones within the Floridan aquifer system and have potential to provide a vertical pathway of the migration of groundwater between permeable zones. Hydrostratigraphy from onshore is projected onto the profile. Modified from Cunningham and Walker (2009) and Cunningham et al. (2012). [larger image]

Expected Benefits:

Because of the risk posed by structural geologic anomalies (faults, vertical fractures, karst collapse structures; fig. 3) and much less advanced stratigraphic knowledge of physical system, FAS system sustainability remains uncertain. Seismic sequence stratigraphic techniques coupled to existing borehole data offers an opportunity to improve existing groundwater flow models, as well as assess system sensitivity to well field interference, predict upconing of more saline fluids, improve water resource management, and aid in site selection of future FAS projects.

References:

Cunningham, K.J., and Walker, C., 2009, Seismic-sag structures in Tertiary carbonate rocks beneath southeastern Florida, USA: evidence for hypogenic speleogenesis?: In Klimchouk, A.B., and Ford, D.C., eds., Hypogene Speleogenesis and Karst Hydrogeology of Artesian Basins. Ukrainian Institute of Speleology and Karstology, Special Paper No. 1, Simferopol, Ukraine, p. 151-158. (Please note that this is a PDF file and requires the FREE Adobe Acrobat Reader® to be read.)

Cunningham, K.J., Walker, C., and Westcott, R.L., 2012, Near-surface, marine seismic-reflection data define potential hydrogeologic confinement bypass in the carbonate Floridan aquifer system, southeastern Florida: Society of Economic Geophysicists 2012 Annual Meeting, Las Vegas, NV, 6 p.

Reese, R.S., and Richardson, E., 2008, Synthesis of the hydrogeologic framework of the Floridan aquifer system and delineation of a major Avon Park Permeable Zone in Central and Southern Florida: U.S. Geological Survey Scientific Investigations Report 2007-5207, 60 pp.

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Last updated: February 14, 2013 12:50 PM (KP)