AQUIFER VULNERABILITY ASSESSMENT: PROJECT REVIEW COLUMBIA COUNTY June 11, 2009 Columbia County, Florida Advanced GeoSpatial Inc. Alan Baker, P.G. James Cichon

Presentation Overview Conceptual Definition Conceptual Definition Model Results Model Results Implementing Model Results Implementing Model Results Generalization with examples Generalization with examples

Model Limitations Vulnerability is relative; all aquifers are vulnerable Vulnerability is relative; all aquifers are vulnerable Based on features of the natural system that have association with location aquifer vulnerability Based on features of the natural system that have association with location aquifer vulnerability Does not account for human activity Does not account for human activity Does not take account for contamination types Does not take account for contamination types Does not estimate ground-water flow paths Does not estimate ground-water flow paths Does not model fate/transport of chemical constituents Does not model fate/transport of chemical constituents Large surface water features omitted Large surface water features omitted

Study Area over which to search for a particular occurrence Study Area over which to search for a particular occurrence Usually a county or some political boundary Usually a county or some political boundary Can be aquifer or springshed specific Can be aquifer or springshed specific Conceptual Definition

Development of evidential layers used as predictors: Development of evidential layers used as predictors: Soil Properties Soil Properties Confinement or Overburden Thickness Confinement or Overburden Thickness Sinkhole Features or closed topographic depressions Sinkhole Features or closed topographic depressions Conceptual Definition

Training Sites Training Sites Dataset of occurrences in our case ground water wells Dataset of occurrences in our case ground water wells Maximize knowledge by locating as many as possible Maximize knowledge by locating as many as possible Evaluate water quality records to locate upper quartile Evaluate water quality records to locate upper quartile Ultimately use a subset of total wells Ultimately use a subset of total wells Conceptual Definition

Conceptual Model Evidential layers are spatially associated with the distribution of known occurrences and then generalized into binary patters Evidential layers are spatially associated with the distribution of known occurrences and then generalized into binary patters Individual evidence layers are combined together as a map depicting the best areas to search for contamination Individual evidence layers are combined together as a map depicting the best areas to search for contamination

Use known locations and assess their distribution spatially with respect to each factor causing occurrence Use known locations and assess their distribution spatially with respect to each factor causing occurrence Where are the relationships or breaks between the data and the training points? Where are the relationships or breaks between the data and the training points? Conceptual Model

Input Input Soil Permeability Soil Permeability Overburden Thickness Overburden Thickness Hydraulic Head Difference Hydraulic Head Difference Karst Features Karst Features

Soil permeability Soil permeability Determine spatial association between theme and training points Determine spatial association between theme and training points Analysis reveals that highest contrast occurs at a soil permeability rate of 7.66 in/hr Analysis reveals that highest contrast occurs at a soil permeability rate of 7.66 in/hr

Overburden thickness Overburden thickness Determine spatial association between theme and training points Determine spatial association between theme and training points Analysis reveals that highest contrast occurs at a overburden thickness of 117 feet Analysis reveals that highest contrast occurs at a overburden thickness of 117 feet

Karst Features Karst Features Determine spatial association between theme and training points Determine spatial association between theme and training points Analysis reveals that highest contrast occurs at a distance of 210 m from a karst feature Analysis reveals that highest contrast occurs at a distance of 210 m from a karst feature

Aquifer Vulnerability Maps We now have a map showing where to focus our efforts in similar locations We now have a map showing where to focus our efforts in similar locations Results are based on data collected about existing occurrences Results are based on data collected about existing occurrences Model reveals a map showing favorable areas with greater probablity of finding occurrence Model reveals a map showing favorable areas with greater probablity of finding occurrence Relative Vulnerability Vulnerable More Vulnerable Most Vulnerable

Local versus regional assessment Larger scale study area: Wekiva Aquifer Vulnerability Assessment Larger scale study area: Wekiva Aquifer Vulnerability Assessment Results are normalized across smaller study area, not entire statewide extent of aquifer system Results are normalized across smaller study area, not entire statewide extent of aquifer system Can include refined input data such as LIDAR Can include refined input data such as LIDAR Provides more usable final product for planners, developers, regulators, and local government Provides more usable final product for planners, developers, regulators, and local government Local versus Regional

Aquifer Vulnerability Assessment Benefits Assists local government, planners and developers in guiding growth into areas delineated as lower vulnerability Assists local government, planners and developers in guiding growth into areas delineated as lower vulnerability Enables more focused protection of sensitive areas, e.g., springsheds and ground-water recharge areas Enables more focused protection of sensitive areas, e.g., springsheds and ground-water recharge areas Public tax dollars used more wisely as a result Public tax dollars used more wisely as a result Has be used to help guide wastewater management requirements – septic zones vs. centralized sewer Has be used to help guide wastewater management requirements – septic zones vs. centralized sewer Leon County & Alachua County Leon County & Alachua County Purpose, End Users, and Benefits

Implementing model results Results are not static; model is based on best available data and is snapshot in time Results are not static; model is based on best available data and is snapshot in time New and refined data reveals more accurate or complex statistical patterns allowing higher confidence in results New and refined data reveals more accurate or complex statistical patterns allowing higher confidence in results Lidar: Karst and Overburden Lidar: Karst and Overburden Accuracy is function input data Accuracy is function input data Approach is highly adaptable and useful tool for implementing ongoing protection of ground-water resources Approach is highly adaptable and useful tool for implementing ongoing protection of ground-water resources Implementing Model Results

Alachua and Leon Counties contracted with AGI for development of derivative protection-zone maps based on each of the County Aquifer Vulnerability Models Alachua and Leon Counties contracted with AGI for development of derivative protection-zone maps based on each of the County Aquifer Vulnerability Models Deliver an aquifer protection zone map based on individula results that is directly applicable to land use and environmental regulatory decisions Deliver an aquifer protection zone map based on individula results that is directly applicable to land use and environmental regulatory decisions Generalization of CAVA Model Results

Methodology Generalization of the vulnerability map into specific aquifer protection zones Generalization of the vulnerability map into specific aquifer protection zones Raster Smoothing techniques employed Raster Smoothing techniques employed Help guide implementation Help guide implementation Avoid use of results on parcel to parcel scale Avoid use of results on parcel to parcel scale Account for highly resolved but isolated areas of vulnerability Account for highly resolved but isolated areas of vulnerability Use of ArcGIS Spatial Analyst extension Use of ArcGIS Spatial Analyst extension

Determination of Appropriate Analysis Window Recent projects recommended that model results be applied on a local scale of greater than or equal to approximately 1.0 mi 2 for statewide studies (Florida Aquifer Vulnerability Assessment) Recent projects recommended that model results be applied on a local scale of greater than or equal to approximately 1.0 mi 2 for statewide studies (Florida Aquifer Vulnerability Assessment) Or approximately 0.75 mi 2 for localized studies (Alachua, Wekiva, Leon and Marion County Aquifer Vulnerability Assessments). Or approximately 0.75 mi 2 for localized studies (Alachua, Wekiva, Leon and Marion County Aquifer Vulnerability Assessments). Based on similarities to larger scale projects, AGI determined that model results be used at a recommended scale of 0.75 mi 2, or an approximate 4,500-ft grid cell size. Based on similarities to larger scale projects, AGI determined that model results be used at a recommended scale of 0.75 mi 2, or an approximate 4,500-ft grid cell size.

ACAVA Model Results

Draft test results Focal Mean Filters on a window with a radius of 12 cells Cell size is 345 m. Calculates a statistic on a raster over a specified neighborhood. Focal Mean Finds the mean of the values for each cell location on an input raster within a specified neighborhood and sends it to the corresponding cell location on the output raster.

Note on CCAVA Protection zone map will be a derivative product of the original model CCAVA results Protection zone map will be a derivative product of the original model CCAVA results Not intended as a replacement of the CCAVA results Not intended as a replacement of the CCAVA results As a result, the protection zone map will represent a standalone map product based on CCAVA results and additional supplemental datasets As a result, the protection zone map will represent a standalone map product based on CCAVA results and additional supplemental datasets

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