The following is an accounting of the discussions, events, and decisions that occurred during a meeting of the Aquifer Committee Working Group held December 6, 2001 in the O'Conner Room of the Savannah Civic Center, Savannah Georgia.
The third meeting of the Working Group convened at approximately 9:45 AM. Those attending and their affiliations were as follows:
Please note that Chris Schuberth arrived after the lunch break and was present for approximately one hour; his role was primarily as an observer. Bill McLemore was called away from the meeting at approximately 2:15 PM. Larry Keegan did not attend the afternoon session. John Cox serves as Chairman of the Aquifer Committee Working Group.
The Working Group Chairman called the meeting to order at approximately 10:10 AM. Copies of the Draft Study Plan (with comments attached) were distributed to the membership. The purpose of the meeting was to discuss the Draft Study Plan and comments and to finalize the various work elements to be recommended to the Aquifer Committee.
Bill McLemore suggested that the Study Plan "elements" be referred to as "tasks" for clarity and this suggestion was accepted. Hence the ten work "elements" previously identified during the second Working Group meeting and referred to within the Draft Study Plan are referred to as "Tasks" herein.
John Cox stated that each task would be listed, discussed as necessary and voted on by the Working Group regarding inclusion within the final study plan to be recommended to the Aquifer Committee. He further stated that in order to keep the process moving forward, a majority vote in the affirmative for each task would be required for inclusion; consensus would not be necessary and that the Working Group could "agree to disagree" on particular issues. Those voting in the affirmative should be prepared provide and discuss the rationale for including that particular task in the recommended Study Plan. Those in the minority on each issue would be so noted and their position as why a task should not be included in the recommended Study Plan would similarly be noted for the record. The Working Group raised no objections to this approach. The meeting then proceeded to focus upon the ten tasks identified.
The various tasks were listed for discussion in the order that they were first identified during the second Working Group meeting. Discussion regarding logical sequencing of the tasks was deferred until later in the meeting.
Task1. Reconnaissance level of drilling (land-based geologic transect)
Task 1 was unanimously voted for in the affirmative for inclusion in the Study Plan to be recommended to the Aquifer Committee.
Discussion focused on the number of sites to be drilled, locations of drilling sites, and sampling and analyses to be recommended.
It was decided that the following general locations would be recommended for drilling as part of the transect: Tybee Island, Ft. Pulaski, near Elba Island, and at the northern end of Hutchinson Island. The prescribed drilling locations could be modified based upon information obtained during additional seismic reflection surveying (Fields Cut to off-shore of Tybee Island) It was decided that a control site (near Ridgeland) would not be recommended to be drilled; however, the control location might be added to the transect if ground-water age determinations and relative movement of saltwater at the other locations could not be determined. The Bull River site that was drilled during March 2001 would not be re-drilled; however, data collected from that site would be included within the transect and piezometers or monitoring wells would be recommended at the Bull River location.
It was agreed that the Study Plan would recommend that each drilling location be geophysically logged (spontaneous potential, electrical resistivity, gamma, and sonic logs) core samples would be analyzed to determine estimates of vertical hydraulic conductivity (Upper Floridan confining unit), porosity and that pore-water samples would be collected and analyzed for salinity, age determination (radio isotopes) and general aqueous geochemistry parameters. The land-based geologic transect will be relied upon to establish base-line conditions (pre-harbor expansion).
Task 2. Offshore Drilling (along channel)
Task 2 was unanimously voted for in the affirmative for inclusion in the Study Plan to be recommended to the Aquifer Committee.
The offshore drilling will be completed with a jack-up barge-mounted drilling rig and will be focused upon the areas previously characterized by thinned Upper Floridan confining unit thicknesses (paleochannels). No specific number of drilling locations along the navigation channel was discussed.
Core samples would be analyzed to determine estimates of vertical hydraulic conductivity (Upper Floridan confining unit), porosity and pore-water samples would be collected and analyzed for salinity, age determination (radio isotopes) and general aqueous geochemistry parameters. Each boring would also be geophysically logged for spontaneous potential, electrical resisistivity, gamma emission, and sonic velocity.
The rationales for this recommendation are that the areas to be investigated will be most representative of the areas to be dredged; and Task 2 is part of the overall determination of baseline conditions.
Task 3. Pilot-Scale Aquitard Test
There was unanimity regarding the importance and need for obtaining vertical hydraulic conductivity data and that it is a critical parameter. The minority opinion is that it needs to be obtained using in situ testing. The minority position rationale for including aquitard testing in the recommended Study Plan were: vertical hydraulic conductivity is a scale dependent parameter, aquitard tests are recognized as the best approach to determining vertical hydraulic conductivity, laboratory derived estimates of vertical hydraulic conductivity are less representative of field conditions than are aquitard tests, the cost associated with conducting aquitard tests is nominal, and aquitard testing is the best approach to determine vertical hydraulic conductivity.
The majority position of the Working Group was to exclude pilot-scale aquitard testing from the Study Plan to be recommended to the Aquifer Committee. Those in the negative (against inclusion in the Study Plan) were: Bill McLemore, Jim Landmeyer, Camille Ransom, Harold Gill, and John Cox. Those voting in the affirmative (for inclusion in the Study Plan) were Jim Reichard, Jim Henry, and Rick Krause. John Clarke abstained from voting on this particular task.
The rationales of the majority position were: concerns regarding the feasibility of conducting an aquitard test (in this setting, i.e. ambient pumping interference, and large contrast in hydraulic conductivity between the Upper Floridan aquifer and the Upper Floridan confining unit), concerns regarding the assumptions involved in data analyses, concerns that the test would be land-based while the area of concern is within the navigation channel (especially over the Tybee structural high), the presence of fractures and other vertical secondary permeability features is postulated, but has not been demonstrated within the navigation channel, and the stress required to elicit a hydraulic response within the upper confining unit is probably large.
The minority position rationales for including aquitard testing in the recommended Study Plan were: vertical hydraulic conductivity is a scale dependent parameter, aquitard tests are recognized as the best approach to determining estimates of vertical hydraulic conductivity, laboratory derived estimates of vertical hydraulic conductivity are less representative of field conditions than are aquitard tests, the cost associated with conducting aquitard tests is nominal, and aquitard testing is the best approach to determine vertical hydraulic conductivity.
Task 4. Analyze and Evaluate Aquitard Test Data
Inasmuch as the majority opinion was to not include aquitard testing in the study plan to be recommended to the Aquifer Committee, this task similarly will not be included in the study plan.
Task 5. Complete Monitoring Well Clusters at Each Land-Based Transect Location
There was consensus to include this task in the study plan to be recommended to the Aquifer Committee. Monitoring well clusters will be recommended to be located at the northern end of Hutchinson Island, in the vicinity of Elba Island, at the U.S. Highway 80 bridge over Bull River, Ft. Pulaski, and Tybee Island.
The rationales for recommending that this task be completed were: monitoring wells will be used to determine vertical distribution of head, salinity, age of water and other aqueous geochemical parameters, and to monitor head changes within the Upper Floridan aquifer and the Upper Floridan confining unit in response to changes in pumping.
Task 6. Complete Additional Seismic Reflection Survey
There was consensus to include this task in the study plan to be recommended to the Aquifer Committee.
The rationales discussed for including Task 6 in the study plan to be recommended to the Aquifer Committee were: the geographic orientation, geometry, and areal extent of the scour channels (i.e. paleochannels) need to be better defined and the seismic reflection survey will provide data to accomplish this, the paleochannels represent the most vulnerable points of potential saltwater intrusion into the Upper Floridan, and the survey will aid in describing the thickness and character of the Upper Floridan confining unit.
Task 7. Research and Compile Relevant Pumping, Dredging, and Hydrogeologic Data and Synthesize Field Data into a Working Database or Graphical Representation (Pre-Modeling)
There was consensus among the Working Group to include Task 7 in the study plan to be recommended to the Aquifer Committee.
The rationale for including Task 7 is that historic data are necessary to predict future conditions.
Note: This Task was originally presented as two separate tasks in the First Draft Study Plan. It was suggested and agreed that these tasks should be combined into a single work task. Therefore, the numbering for the subsequent tasks has been changed accordingly.
Task 8. Complete Numerical Model to Predict Flux in Chloride Concentration across the Upper Confining Unit Beneath the Navigation Channel, and Approximate Lateral Transport Within the Upper Floridan Aquifer (formerly Task 9)
The majority of the Working Group favored inclusion of Task 8 in the study plan to be recommended to the Aquifer Committee. Those comprising the majority were: Jim Reichard, Jim Henry, Jim Landmeyer, Camille Ransom, John Clarke, Rick Krause, and John Cox. Bill McLemore was opposed to including this task.
The majority rationales for including Task 8 in the study plan were: numerical modeling will provide a predictive ability regarding future impact to the Upper Floridan aquifer due to dredging, numerical modeling will assist in understanding current hydraulic and salinity distribution conditions, modeling is used for similar tasks and for other scientific and engineering applications, and the model proposed for development would have sound, robust data sets for both input to the model(s) and for arrays against which to calibrate, thus making the model(s) reliable for the purpose intended.
The minority position for not including Task 8 in the study plan was as follows. Modeling by its very nature is subjective and is based on assumptions. Assumptions can be readily challenged and thus persons who disagree with the model results can readily discredit models. Further, models, even if correctly constructed, can provide incorrect answers. If the Ports Authority elects to perform models then the Authority should recognize: persons who disagree with the model results may be able to successfully challenge the model assumptions (i.e. the model would be discredited) and the model may show that dredging has or has no impact on water quality in the Upper Floridan Aquifer, when, in fact the opposite is true.
Task 9. Develop Lateral Solute-Transport Model Using the Navigation Channel as a Line Source to Predict Migration and Dilution of any Predicted Chloride Plume Within the Upper Floridan Aquifer (Formerly Task 10)
Discussion regarding this task considered the option of using a coupled 2-D numerical model to be completed as an integral part Task 8. Ultimately, it was agreed that Task 9 would be deleted and that Task 8 would model both vertical leakage and solute transport through the Upper Floridan confining unit and lateral solute transport within the Upper Floridan aquifer. No decision as to recommend use of coupled two-dimensional models or of separate, uncoupled models in a phased approach, with the lateral 2-D flow and transport model being developed only if necessary and appropriate was reached; rather it decided to simply refer to the task as "Numerical Modeling."
The minority position for not including Task 8 in the study plan was as follows. Modeling by its very nature is subjective and is based on assumptions. Assumptions can be readily challenged and thus persons who disagree with the model results can readily discredit models. Further, models, even if correctly constructed, can provide incorrect answers. If the Ports Authority elects to perform models then the Authority should recognize: persons who disagree with the model results may be able to successfully challenge the model assumptions (i.e. the model would be discredited) and the model may show that dredging has or has no impact on water quality in the Upper Floridan Aquifer, when, in fact the opposite is true.
The discussion then focused on developing a logical sequence of work tasks. In developing a sequence, new task numbers were assigned according to sequence, therefore tasks numbers discussed above do not correlate with the sequence task numbers. The sequenced task numbers also reflect deletions of tasks, as well as combination of tasks that were originally discussed as separate tasks.
The sequence of tasks within the study plan to be recommended is as follows.
Task 1. Seismic Reflection Survey
Task 2. Onshore reconnaissance drilling (geologic transect)
Task 3. Construction of piezometer (monitoring well) clusters
Task 4. Offshore drilling (in-channel or along channel drilling)
Task 5. Historical data research and development of database
Task 6. Develop numerical model of system
Rick Krause suggested that the study plan should use standardized terms for such terms as "upper confining unit," "movement of saline water," and "water level." The following terms were agreed upon:
"Upper confining unit" and similar references shall be replaced with "Upper Floridan confining unit.
"Movement of saline water" shall be replaced with "transport."
"Water level" shall be replaced with "head."
It was then agreed that John Cox would prepare a draft of the meeting minutes and distribute them to the Working Group for review and comment. After receiving comments, the meeting minutes are to be finalized and will become part of the public record.
A second draft of the study plan will then be developed (based on the outcome of this meeting) and will be distributed to the Working Group for review and comment. After finalization of the second draft of the study plan to be recommended to the Aquifer Committee, it will be presented to the Aquifer Committee at the next meeting.
John Cox directed comments to Chris Schuberth regarding a tentative schedule of tasks to be completed. Chris was informed that it was unlikely that finalization of the meeting minutes and development of a second draft study plan could be completed prior to the Christmas holiday. Chris responded that the SEG is not scheduled to meet again until February 2002; therefore the Aquifer Committee did not need to reconvene until approximately mid-January or thereabout.
John Cox queried the Working Group as the necessity of reconvening to further discuss the various tasks to be recommended. The consensus was that no further meetings would be necessary to discuss the study plan to be recommended to the Aquifer Committee.
A move was offered and seconded to adjourn the meeting and it was so moved at approximately 3:00 P.M..