Lake Okeechobee Sediment Management Feasibility Study

Public Outreach Meeting # 4

January 14, 2003

South Florida Water Management District

Okeechobee Service Center

6:30-8:00pm

 

Meeting Minutes

 

Meeting Attendees:

 

Monroe Arnold, Private Citizen

Albert Bastulto, South Florida Water Management District

Theresa Brogan, General Chemical Corporation

Horace Durance, Hi-Lo Caretaking

James Erskine, Miccosukee Tribe

Matt Ferguson, Private Citizen

Mitch Flinchum, University of Florida/ IFAS

Don Fox, Florida Fish and Wildlife Conservation Commission

Pete Gawda, Okeechobee News

Harry Gibbons, Ph.D., Tetra Tech Inc.

Susan Gray, South Florida Water Management District

Larry Harris, Friends of Lake Okeechobee

Carroll Head, Friends of Lake Okeechobee

Clyde Hopple, US Army Corps of Engineers

Angie Huebner, US Army Corps of Engineers

R. T. James, South Florida Water Management District

Raymond Jones, Private Citizen

Anwar Kahn, EA Engineering, Inc.

Dan Levy, EA Engineering, Inc.

Mike Lockhart, Lockhart Ag Technology

Kathy Lukasiewicz, Blasland, Bouck & Lee, Inc.

Katharine Murray, Environmental Quality, Inc.

Eric Nelson, US Environmental Protection Agency

Jorge Patino, South Florida Water Management District, Project Manager

Ronald Payne, City of Belle Glade

Ryan Peck, US Army Corps of Engineers

Janet Phipps, PBC Department of Environmental Resources Management

Curt Pollman, Ph.D., Tetra Tech, Inc.

Max Quackenbos, St. Lucie River Initiative

Gary Ritter, South Florida Water Management District

Kim Shugar, Florida Department of Environmental Protection

Lee Sweet, Lockhart Ag Technologies

Bill Veach, City of Okeechobee

Gary Warren, Florida Fish and Wildlife Conservation Commission

John Welch, Private Citizen

Herb Zebuth, Florida Department of Environmental Protection


Welcome

Ms. Kathy Lukasiewicz of Blasland, Bouck & Lee, Inc. (BBL) opened the meeting with a warm welcome to all attendees.  She expressed gratitude to the participants for their interest in the Lake Okeechobee Sediment Management Feasibility Study (Feasibility Study) and for coming out to this fourth public outreach meeting designed to present the Feasibility Study’s findings and solicit input from the public and intergovernmental agency personnel.

 

Ms. Lukasiewicz invited everyone in the room to introduce themselves.  Meeting attendees and their affiliation are listed above.  

 

Introduction

Ms. Lukasiewicz began the presentation on the Feasibility Study:

The Feasibility Study is a three-year, desktop study being conducted by the South Florida Water Management District (District) through a contract with Blasland, Bouck & Lee, Inc. (BBL).  The study was initiated in the fall of 2000. 

 

The overall objective of the Feasibility Study is to evaluate a variety of sediment management alternatives to address internal phosphorus loading in Lake Okeechobee; improve water quality and decrease turbidity and blue-green algae blooms. 

 

The Feasibility Study is considered necessary for a number of reasons, including:

  • There is an estimated 51,600 metric tons of phosphorus in lake mud sediments;
  • Internal phosphorus loads equal external phosphorus loads from watersheds;
  • Lake Okeechobee may not respond as quickly to external reductions without measures taken to manage internal inputs;
  • This Feasibility Study is required by the Lake Okeechobee Protection Act [Florida Statute 373.4595(3)(f)]; and
  • The Feasibility Study is needed to support management decisions by the District’s Governing Board.

 

During Task 1 of the Feasibility Study, the project team established goals and performance measures and identified potential impacts.  Five project goals and twenty–six performance measures were collaboratively established with input from the public and interagency personnel.  The Goals and Performance Measures report, finalized in June 2001, identifies the five overall goals for the project:

 

Goal 1 – Maximize Water Quality Improvements

Goal 2 – Maximize Engineering Feasibility and Implementability

Goal 3 – Maximize Cost Effectiveness

Goal 4 – Maximize Environmental Benefits

Goal 5 – Maximize Socioeconomic Benefits

 

Task 2 of the Feasibility Study - Development of Sediment Management Alternatives - incorporated public and interagency participation to develop a specific array of technologies to be evaluated in detail by applying four initial screening criteria.  The four screening criteria initially applied were:

·          Effectiveness,

·          Implementability,

·          Applicability to Lake Okeechobee, and

·          Risk and reliability.

 

Thirty-five different process options and technologies were identified and evaluated with respect to the above screening criteria for use in Lake Okeechobee.

 

Through the assessment process, some of the technologies and specific process options were “screened out” (due to lack of: potential effectiveness, implementability, applicability, set risks and concerns for reliability) and, therefore not carried forward into the assembly of overall sediment management alternatives.

 

Retained Alternatives

The retained technologies were consolidated into three major alternatives:

1)      No In-lake Action while monitoring ongoing external phosphorus reduction efforts;

2)      In-place Chemical Treatment using Aluminum Sulfate (Alum) and Sodium Alumate; and

3)      Hydraulic dredging with various post-dredging sediment management scenarios, including near-shore and upland confined disposal facilities (CDFs).

 

Task 3 of the Feasibility Study - Development of a Work Plan - defined how the alternatives would be evaluated against the goals and performance measures established for the project.

 

Task 4 of the Feasibility Study - Evaluation of Alternatives - provided full-scale evaluation of the retained technologies. During this task each alternative was evaluated in detail with respect to the following goals:

·          Maximize water quality improvements;

·          Maximize engineering feasibility and implementability;

·          Maximize cost effectiveness;

·          Maximize environmental benefits; and

·          Maximize socioeconomic benefits

 

All alternatives were also evaluated against each of the twenty-six clearly defined performance measures.

 

Water quality modeling was performed along with engineering evaluations, detailed cost estimates, personal interviews, case study reviews and socioeconomic analyses.  

 

Ms. Lukasiewicz continued with a presentation of the Results of the Draft Feasibility Study.

 

Results of the Draft Feasibility Study

 

Assumed Model Boundary Conditions

Water quality modeling proceeded using a set of assumptions:

  • Initial inflow loads of phosphorus (P) equal to 426 metric tons in 2000 (representing the average over the last 10 years)
  • A decline linearly of 25% between 2000 and 2010 to 328 metric tons (attributed to the implementation of best management practices (BMPs) in the watershed) and,
  • A decline linearly to 140 metric tons by the year 2015.

 

No In-lake Action

The No In-lake Action Alternative was presented and discussed.

 

Results of the evaluation include:

  • Modeling results for this scenario indicate a 25% decrease in the frequency of algal blooms (to below 15% by the year 2015) and a decrease to below 10% by the year 2028.
  • Steady-state lake recovery conditions would be achieved approximately 35 years from the point external loads are reduced to the inflow load of 140 metric tons of P.
  • 90% of the target is achieved by 2063.

     

Mr. Harris questioned: Do these results show that the lake will reach the desired level by 2015?

 

Ms. Lukasiewicz responded: One of the key assumptions of the feasibility study is that the TMDL goal will be met by 2015.  Modeling results for the No In-lake Action Alternative show that the project goal for in-lake P concentrations (40 µg/L) would be met by 2063.

 

Mr. Head noted: The results indicate a 25% decrease in algal bloom “frequency” by 2015.  Please explain.

 

Dr. James explained: The 25% decrease is attributable to a decrease in the frequency in the algae blooms from the current 22% of the time to 15% with an overall linear reduction of 25%.

 

Mr. Fox asked: What is the metric used in the definition of an algal bloom?

 

Dr. James of the SFWMD responded:  The metric is the in-lake concentration of 40 µg/L of chlorophyll a.  This metric is based on actual data collected in the lake over a period of time (approximately 28 years).

 

 


Chemical Treatment

The Chemical Treatment Alternative was presented and discussed.

 

Results of the evaluation include:

  • The cost of using aluminum sulfate (alum) and sodium aluminate is estimated at approximately $500 million.
  • Chemical treatment would start at about year 2012 and would take 3 years to complete.
  • Modeling results and technical evaluations indicate chemical treatment would effectively inactivate the existing P, and much of the new P introduced to the sediments for approximately 15 years.
  • Beyond 15 years, the lake would progressively return to its original state unless chemical treatment applications were repeated or significant reductions in external loads were realized.

 

Ms. Lukasiewicz explained that the application of alum would be preceded by many processes, including, but not limited to, an involved permitting process, implementation and completion of pilot and demonstration projects and an evaluation of ecological, benthic and biological impacts. 

 

Mr. Quackenbos noted:  Studies reveal the application of alum produces a precipitate.  He questioned whether this precipitate would be inactivated.

 

Ms. Lukasiewicz responded:  A floculant is formed when the alum reacts with the phosphorus and effectively inactivates the phosphorous in the sediment. 

 

Mr. Harris:  Would there be an additional cost of $500 million after 15 years for reapplication of alum?

 

Ms. Lukasiewicz responded:  It is possible, that unless external load reductions are achieved by 2013, alum re-application and the associated costs would be required.  Application of alum has not been determined to be a permanent solution for the P in sediments in Lake Okeechobee.

 

Ms. Brogan questioned the estimated cost projection of $500 million.

 

Mr. Patino of the SFWMD responded:  There are numerous costs taken into account when projecting costs in the Feasibility Study, such as design, engineering, production, transportation, mesocosm studies, etc.

 

Ms. Lukasiewicz added:  The Feasibility Study incorporated the total cost of chemical treatment including, but not limited to, a detailed pilot study to demonstrate the environmental benefits and impacts to the benthic and fisheries communities, evaluation of potential toxicity, design costs, shipment and transport of materials, equipment permitting, implementation, and pre and post implementation monitoring.  The cost of the chemicals are a fraction of the total costs of chemical treatment.  Also, the costs developed during the feasibility study are for planning purposes and have a fluctuation factor of ±30% - 50%.

 

If chemical treatment were used in Lake Okeechobee it would be the largest alum application in the world to date. 

 

Mr. Fox raised a concern over using chemical treatment; noting the potential for elevated sodium hydroxide levels that may cause problems for the biota.

 

Ms. Phipps commented: You have indicated that the size of the water body is a factor as well as the turbidity within the lake.  Lake Okeechobee has two significant factors affecting the efficacy of treatment:  size and continued inflow. 

 

Ms. Lukasiewicz continued:  Success stories for lakes treated with alum include Shadow Lake in Wisconsin, Moorley Lake in New Hampshire, and Erie and Camel Lake in Washington state.  In the cases where alum treatment has not been successful, the buffering capacity of the lake and the lake pH was not clearly understood and in most cases, lakes have been improperly dosed.  Alum toxicity occurs when a lake is not properly buffered and the pH is too low.

 

There is an advantage in that Lake Okeechobee is naturally a well buffered lake.  The lakewater is alkaline and the sediments are very high in calcium.  The combined use of sodium aluminate along with alum often provides for additional buffering capacity.

 

Mr. Harris asked:  Would a hurricane or other act of nature have a significant effect on the lake’s treatment? 

 

Ms. Lukasiewicz responded:  Under storm conditions, there would be a lot of movement of material, but with the proper dosing and application techniques, this movement would not necessarily create a problem.  There is a good chance that the inactivated material would move around, but it would not likely come out of the floculant state and negatively affect water quality.

 

Ms. Lukasiewicz initiated a question to Dr. Gibbons of Tetra Tech:  Harry, what are your thoughts on the affects of storm, wind and wave action in a situation such as we face in Lake Okeechobee?  Here we have a high fetch, continuous winds and waves and seasonal storms.  How do these conditions relate to alum application? 

 

Dr. Gibbons responded:  Many techniques can be used to apply alum which control the environment given any number of circumstances.  First, every effort could be made to apply the alum during the non-storm season.  In addition, proper planning can allow for the distribution of alum to coincide with the drift.  Also, engineering controls can be used to control water movement during application.


Dredging

The Dredging Alternative was presented and discussed.

 

Results of the evaluation include:

  • The cost of dredging using hydraulic dredges, is estimated at approximately $3 billion.
  • Dredging of the lake’s pelagic zone would start at about the year 2015 and would take 15 years to complete.
  • Technical evaluations indicate that dredging would leave behind a veneer (6 to 10 cm) of sediment which, based on the water quality modeling, would continue to release phosphorus into the water column.
  • The dredging alternative showed limited or no effectiveness.

 

Mr. Levy asked:  Please explain further the problems in the water quality caused by dredging.

 

Ms. Lukasiewicz responded: Water quality problems would result from the required continuous dredging program that would take 15 years to complete.  Constant dredging and movement within the shallow lake, even when employing engineering controls would show some increase in uncontrolled movement of sediment - resuspending the settled material. 

 

Mr. Levy declared: We at EAA did not find a problem with water quality when implementing the Pilot Dredging Study in 2001, in fact, pre and post dredging water quality measurement results were very close to the same.   

 

Ms. Lukasiewicz responded:  There is a notable scale difference between size of the Pilot Dredging Study and treating the entire pelagic zone of Lake Okeechobee.  This difference in scale was a key factor in evaluating the potential for impacts.  The Feasibility Study projections for treating Lake Okeechobee include 8 dredges running 24 hours a day, 7 days a week for 15 years.  The Pilot Dredging Study incorporated dredging 6,000 cubic yards of sediment in an isolated area over a period of two weeks.  The increased magnitude in size and duration of the project was a major consideration.

 

Mr. Head commented:  Although dredging may increase the turbidity, chemical treatment may have a negative effect on the benthic communities.

 

Ms. Lukasiewicz responded:  In case studies, alum application has shown temporary negative impacts on benthic communities, but typically, the communities recover over time.

 

Mr. Erskine asked:  What is the timeframe for reaching the target TDML in comparing No-In lake Action to dredging?

 

Ms. Lukasiewicz responded:  The target TMDL would be reached in about the same timeframe, but an enormous amount of money would be spent on dredging with very little benefit. 


Mr. Khan asked:  How much sediment would be dredged in the pelagic zone?

 

Ms. Lukasiewicz responded:  For the purposes of this FS it was assumed that the entire pelagic zone would be dredged; removing sediments greater than 10 cm.  This volume is estimated to be about 177 million cubic meters.  It was determined through modeling evaluations, that there was no advantage to isolating areas of the pelagic zone for dredging, or targeting specific depth intervals to be removed. 

 

Known Project Uncertainties

There are uncertainties with all the alternatives evaluated, Ms. Lukasiewicz continued. 

 

Project Uncertainties include:

  • Findings presented in this Feasibility Study are in a large part associated with the expectation and assumption that the Comprehensive Everglades Restoration Plan (CERP) goals, as currently understood for watershed phosphorus reductions, can be achieved by the year 2015.
  • Modeling into the future, especially as it relates to projecting climate, water flow and sediment burial rates presents uncertainties.
  • There is a ±30 - 50%, degree of uncertainty in the modeling results and the cost estimates.  However, these uncertainties are applied uniformly among alternatives.

 

Ms. Lukasiewicz presented a graphical representation of modeling (ILPM and LOWQM models, respectively) results comparing the efficacy of Chemical Treatment and Dredging Alternatives in lake water total phosphorus concentrations relative to the No In-lake Action alternative, as shown below:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The two models revealed nearly the same results.  In the long-term, there is not a substantial benefit of either Chemical Treatment or Dredging when compared with no In-lake Action.  

 

Criterium Decision Plus Modeling

Ms. Lukasiewicz continued with a presentation of the Criterium Decision Plus Modeling results. 

 

Using the five Feasibility Study major performance measures: maximize water quality improvements; maximize engineering feasibility and implementability; maximize cost effectiveness; maximize environmental benefits; and maximize socioeconomic benefits as the decision making criteria, and considering all performance measures to be equally important,  the modeling revealed the following ranking:


 

1st)      No In-lake Action

2nd)      Chemical Treatment

3rd)       Dredging

 

Next, the Criterium Decision Plus Modeling was run identifying water quality and cost as the most critical performance measures.  The purpose of this exercise was to determine: if there were any performance measures, if rated exceptionally high, that would change the outcome.  The same results were discovered.

 

Mr. Head asked:  Would the $500 million be spent in addition to the ongoing and future external watershed clean-up activities?

 

Ms. Lukasiewicz responded: Yes, that is the alternative scenario evaluated in the Feasibility Study.

 

Mr. Head responded:  If you put that money into the current external watershed clean-up efforts, perhaps you would reach the goal faster.  The evaluation results of the No In-lake Action Alternative shows a response within a similar timeframe.  The answer seems obvious - clean it up using the additional money on increased external reductions, that would get quicker results.

 

Mr. Payne expressed support for No In-lake Action. 

 

Ms. Phipps added:  The study should recognize cost effectiveness. 

 

Mr. Welch commented:  I have been to every Lake Okeechobee Sediment Management Feasibility Study Public Meeting.  It is my understanding that even if you reduce the external loads to the lake you will still have 56 metric tons of phosphorus remaining in the lake.  This phosphorus contained within the lake sediments may be resuspended every time there is a storm or heavy wind/wave action.  The resuspension will cause continued algae blooms.  Even if you reduce the external loads to 140 metric tons per year you will still have high internal loads.  At the last public meeting [Moore Haven, FL April 4, 2002] we discussed dredging.  It seemed to be the answer to all our prayers.  I would like to go back a couple years and revisit the idea of capping the phosphorus-laden sediment with a clean layer of sand.  I would like an answer as to why that alternative would not be effective and how much it would cost. 

 

Ms. Lukasiewicz responded:  During the Development of Alternatives task of the Feasibility Study we did consider capping as a sediment management technique.  The technique was not carried forward because it is not considered a permanent solution.  The sand would not inactivate the P.  We also could not be sure that clean sand would stay in place long term.  External loading is what drives the dynamics within the system.  If you reduce the external loading, yes, you will still have phosphorus, but when you shut off the source, you change the dynamics of the lake system, the chemistry of the water column and relationship of what is leaving the sediment and entering the water column.  With reduced phosphorus inflow, you will see the occurrence of a newer, cleaner, sediment layer.  Over time, the old layer will be buried and the chemical dynamics of the system will change such that less P will be released into the water column from the cleaner layer.  This is the point at which we are predicting the lake will begin to recover.

 

Dr. James added:  Numerous case studies have shown that with reduced phosphorus loads, shallow lakes recover very well.

 

Mr. Welch asked:  We have 56 metric tons in the lake now.  How many years will it take before we reach the goal of 140 metric tons per year?

 

Ms. Lukasiewicz responded: Based on the modeling performed, the year 2063 is the point at which equilibrium is reached.  It would essentially take 35 years for the lake to reach steady state, equilibrium conditions after the initial target TMDL of 140 metric tons is reached.  It is estimated that by 2060 we would expect to see phosphorous reductions in the water column that would reflect the new TMDL load.

 

One case study in Florida that has been successful in some respects is Lake Apopka.  Approximately 6 years ago, there was a concerted effort to cut external loads coming into Lake Apopka.  Prior to those efforts, the St. Johns Water Management District predicted that it would take hundreds of years for the lake to show improvements and recover.  Over the past five years there has been a reduction of nearly 30 - 40 % concentration of P in the water column, that has been initially tied to reductions in external loads among other things.

 

Mr. Zebuth added:  There has been a gradual reduction in external loads to Lake Apopka over the years.  Approximately 40 years ago, they stopped the wastewater discharges into the lake, but recently the agricultural activity has ceased its input into the lake. 

 

Mr. Harris expressed his support for reducing external loads, suggesting that reduction in external loads may be a solution.

 

Mr. Quackenbos asked:  Can the modeling results be strengthened by implementing a pilot project with respect to the uncertainties?

 

Ms. Lukasiewicz responded:  Projections in climate, water flow and sediment burial rates are specific factors in the modeling that could be refined with additional scientific information.  Empirical data collected in the lake - in real time - including turbidity, phosphorus levels, chlorophyll a, etc. will be useful in the future for improving model certainty.

 

Mr. Zebuth asked: Are the results presented within the Evaluation of Alternatives the results of two different models?

 

Ms. Lukasiewicz responded: Yes, two different models were used in this study.  Modeling in both cases was performed to determine the results of alternatives in relation to the No In-lake Action Alternative.  The two models – Lake Okeechobee Water Quality Model (LOWQM) and Internal Loading Phosphorus Model (ILPM) – were coded in different sequences which accounts for some of the variation in results.  The reason for the differences is due predominately to the partitioning binding coefficient.

 

Draft Recommendations

Ms. Lukasiewicz began the presentation of the Feasibility Study Draft Recommendations and asked everyone to comment and /or make suggestions on the recommendations presented.

 

Draft Feasibility Study Recommendations include:

1)      External load reductions in the watershed should be the focus of efforts to achieve water quality goals in the lake. 

2)      If the lake does not respond to reductions in external loads as projected, consider chemical treatment as a sediment management alternative to achieve water quality goals.  Chemical treatment would require an in-depth pilot study.

3)      Continue to collect water quality data to improve model certainty.

 

Mr. Harris asked: Are there adverse consequences to adding massive amounts of chemicals such as alum to the lake?

 

Ms. Lukasiewicz responded: There are case studies where alum has been applied properly and there have been no adverse impacts to aquatic life.  There have also been a number of studies where alum application was not managed properly; where the lake’s pH was not been well understood; and the proper pilot study was not performed.  In cases where the dynamics and chemistry of the lake has not been clear, and dosing is not properly managed, alum application was not successful.  Two of the case studies discussed in the Feasibility Study include Cattle Lake in Wisconsin and Moorley Lake in New Hampshire.  These successful alum application projects were the result of properly managed alum dosing and application with a clear understanding and buffering of the lake’s pH, and close monitoring of the fish and biotic communities.  Although this technique has been demonstrated as a successful restoration technique, the exact results of its application in Lake Okeechobee are not certain. 

 

Mr. Quackenbos added:  I am interested in the size of the lakes where alum application has been successful.  How do the lakes compare with Lake Okeechobee?

 

Dr. Gibbons responded: They were all smaller, ranging from 400 to 2500 acres.  These lakes were also eutrophic.

 

Mr. Fox asked:  Would the application of a chemical treatment allow the survival and continued growth of benthic invertebrate organisms? 

 

Mr. Gibbons responded:  After application, there is usually a gap in the abundance of invertebrates; a period of lag in the productivity of the system, but the systems usually shows a recovery state exceeding the initial conditions.

 

Mr. Fox commented:  There have been decades of work by the public and private sector on the black crappie in Lake Okeechobee.  The black crappie is very important to the economy of the area and Lake Okeechobee.  Many of the lake’s fish spawn in the shoreline areas and the juveniles move offshore to feed in the mud zones.  These fish remain in the mud zones until about age 2.  I am concerned about the potential impacts to this population.  I have seen studies where the treatment was not successful and the results were catastrophic.  Catastrophic events to the benthic community require a long time to recover. 

 

Ms. Lukasiewicz responded:  In order to address and better understand those issues, pilot studies would need to be performed to analyze the lake’s benthic communities.  There would probably be pre and post sampling, mesocosm studies, demonstration projects, and a clearly defined set of performance measures defined prior to implementation of pilot testing and full-scale chemical treatment.

 

Mr. Warren added: What degree of certainty do we have that an alum application would be successful?  There are studies that show the impact on benthic communities do not become evident in the short term, but may be seen in the long term.  What are the assurances that the chemical treatment would not get out of control?

 

Ms. Lukasiewicz responded:  A number of factors would need to be tested and evaluated in a pilot study.  Essential information would include the ability to create a floc during application and treatment that would allow deactivation of the sediments; continuous monitoring of the pH - allowing proper control and buffering of pH levels in the water column; and the engineering and design of a successful dosing procedure.

 

Dr. Gibbons added:  Successful case studies have shown effectiveness in excess of 10 years.  In these cases the technique has not created toxicity in the benthic community or aquatic habitat and the water quality has been maintained to an acceptable level.  Again, these cases were on a much smaller scale than Lake Okeechobee.

 

Mr. Fox noted:  There is a commercial fishing industry in Lake Okeechobee.  The fishermen use 1,600 yard nets within the mud zone.  They operate 5 days a week.  This activity, as expected, creates turbidity in the water column.  Would this activity have an impact on the efficacy of chemical treatment?

 

Ms. Lukasiewicz responded:  That activity would have an impact on the treatment, especially since the lake is approximately 12 feet deep in the pelagic zone.

 

Mr. Head suggested: Considering the eutrophic state of Lake Apopka, why not use it as a pilot project for alum application?  Also, will BBL continue to work on this project?

 

Ms. Lukasiewicz responded: Finalization of the Evaluation of Alternatives will complete our tasks in this Feasibility Study.  We are currently collecting input from the public and interagency personnel on this draft.  Final revisions will be submitted to the District. The District staff will present the findings to the Governing Board and the Governing Board will present their information to the Florida Legislature in July 2003.

 

Mr. Harris commented: The case studies show that successful demonstrations have been in small, shallow, stratified, northern lakes.


Dr. Gibbons responded:  That is correct.

 

Mr. Quackenbos commented:  In view of the economics, if you took only 2% of the $500 million and applied that to watershed clean up, that $10 million would have a huge impact on the lake.

 

Ms. Lukasiewicz responded:  That is a good point.

 

Mr. Quackenbos asked:  Did the Feasibility Study evaluate calcium hydroxide or ferrus sulfate as a treatment alternative?

 

Ms. Lukasiewicz responded:  Yes.  While the use of calcium as a chemical treatment alternative was initially considered, it was screened out in favor of aluminum sulfate, which was deemed a more appropriate option for this lake.  Treatment with iron compounds was also considered, but the iron to phosphorus ratio in the lake is not conducive to using iron as a treatment alternative. 

 

Mr. Zebuth asked:  What impacts would you expect to see in the neighboring communities with implementation of chemical treatment? 

 

Ms. Lukasiewicz responded:  If the alum and sodium aluminate were properly applied and the floc was created in the mud zone, as anticipated, you would likely see rapid improvements in the water column.  Alum is currently used by municipal water treatment facilities to floc out suspended materials.  So, based on case studies, we would not anticipate a negative impact on the water supply to the communities.  There could actually be some benefits based on the improved water quality and clarity.

 

Mr. Zebuth continued:  The study has a confidence level of ±50%.  What would the results look like [referring to the graphic display] if we put those confidence levels to test on each alternative? 

 

Dr. James noted:  There have been improvements in modeling recently as well as changed assumptions that increase the accuracy of the modeling results.

 

Mr. Patino responded:  The same uncertainties are applied to each alternative equally.  If you isolate the No In-lake Action Alternative and calculate the ±50% uncertainty, you would reach the target either earlier or later than expected by a margin of 18 or 54 years required to reach the target level.

 

Mr. Warren asked:  Have you done any modeling to determine the results of partial treatment with the goal being to shift the steady state of the lake and reach the target sooner?

 

Ms. Lukasiewicz responded:  The modeling performed assumed a percentage of the lake would be treated every 6 months for approximately 3 years.  In a sense, the modeling was stepped over the three year period to look for improvement in the lake over time.  Even though we did not focus specifically on what happens if we treat just one section, we know what happens throughout the process and no there were not benefits of partial treatments.

 

Dr. Pollman added:  Because there would be a continuation of phosphorus loading from the watershed, you would not see the benefits of treating only sections of the lake.  It would not be an efficient process. 

 

Mr. Erskine commented:  In review of the draft report, BBL has presented solid justification for ruling out the dredging option.  The draft report does however, seem to leave the door open for the future use of chemical treatment as a sediment management technique by using phrases such as “when applied properly”.  There is a lot of literature that presents the successes as well as the failures of chemical treatment.  The draft report highlights four.  The draft report recommends chemical treatment be considered only if the lake does not respond to the load reductions; or if the load reductions are not achieved.  I am not convinced that the load reductions will actually be achieved on time.  I suggest the statement “if target load reductions are not achieved, then chemical treatment may be considered” be deleted from the recommendations.

 

Ms. Lukasiewicz responded:  Can you provide us with a suggestion to revise this text?

 

Mr. Erskine suggested:  I suggest that you recommend stating that if the lake “does not respond” to external load reductions, then chemical treatment may be an option.

 

Mr. Head commented:  South Florida Water Management District and BBL, you have done a good job!  The results are what many of us were hoping you would find. 

 

Ms. Lukasiewicz thanked Mr. Head for his comment.

 

Mr. Patino noted:  The full draft report is posted on the project website for downloading and review.  Hard copies will also be sent to anyone who leaves their name and address this evening.  The District plans to finalize the draft report by mid-March, so he asked that everyone submit their comments and suggestions to him in early February.  The District is most interested in receiving any and all comments and suggestions.  Please respond to Jorge Patino, Project Manager, at 561-682-2731 or at his e-mail address at jpation@sfwmd.gov.

 

Mr. Patino and Ms. Lukasiewicz thanked all in attendance for their engaging participation.  The meeting adjourned at 8:00 P.M.