### Draft Report 

## Task 3 Legacy P Abatement Plan For Project Entitled 

## Technical Assistance in Review and Analysis of Existing Data for Evaluation of Legacy Phosphorus in the Lake

Okeechobee Watershed

Prepared for 

## South Florida Water Management Distric t

by 

## Soil and Water Engineering Technology, Inc.

In association with 

## JGH Engineering

April 14, 2008Task 2

– Legacy P ii



### Technical Assistance in Review and Analysis of Existing Data for Evaluation of Legacy Phosphorus in the Lake Okeechobee Watershed

Task 3 : Legacy P Abatement Plan Table of Contents IN TRODUCTION
................................ ................................ ................................ .......................... 1 DEFIN IT ION OF LEGACY P
................................ ................................ ................................ ....... 1 BACKGROUND OF LEGACY P
................................ ................................ ................................ .. 2 OVERALL ABATEMENT STRATEGY AND ASSUMPTIONS
................................ ................ 3 LEGACY AND OTHER P SOURCES
................................ ................................ .......................... 4 PHOSPHORUS CONTROLPRACTICES
................................ ................................ .................... 4 In
- Field Agricultural BMPs
................................ ................................ ................................ ...... 10 In
- Field Soil Amendment s ................................ ................................ ................................ ........ 10 Edge
- of
- Field/Farm (EOF) Treatment Technologies
................................ ............................... 12 Residential and Urban
................................ ................................ ................................ ............... 12 Facilities or Point Sources
................................ ................................ ................................ ........ 12 Regional In
- Stream Treatment Technologies
................................ ................................ ........... 13 ESTIMATED IMPLEMENTATION LEVELS AND COSTS TO ACHIEVE TMDL TARGETS

................................ ................................ ................................ ................................ ....................... 13 IMPLEMENTATION SCHEDULE
................................ ................................ ............................. 19 REFERENCES
................................ ................................ ................................ ............................. 20 List of Figures Figure 1. Northern Lake Okeechobee Watershed
................................ ................................ .......... 1Task 2

– Legacy P iii List of Tables Table 1. Surface water inflows, TP concentration s, loading rates, and TMDLtargets for Lake

Okeechobee Tributary

Basins (1991
- 2005)
................................ ................................ .. 5 Table 2. Assumed P mobility factors for legacy , native, and anthrogenic P sources
.................... 6 Table 3. P loads from Soil Based Legacy P for Various L and Uses
................................ ............. 7 Table 4. P loads from Native and Non
- Soil Based L egacy P Anthropogenic Sources fo r Various Land Uses
................................ ................................ ................................ ...................... 8 Table 5. Predicted P Source Loads to Stream, In
- stream Assimilation, and Net Basin Export

(1991
- 2005)
................................ ................................ ................................ ................... 9 T able 6. Measured and Estimated P Source Loads to Stream and Net Basin Exports with TMDL

Targets
................................ ................................ ................................ ........................... 9 Table 7. Phosphorus Control Practices
- Assumed Effectiveness and Costs
............................... 11 Table 8. Northern Lake Okeechobee Basin P Control Practices Implementation Plan for Meeting

the Tributary

TMDL
................................ ................................ ................................ ... 15 Table 9. Upper Kissimmee Basin P Control Practices Implementation Plan for Meeting the

Tributary TMDL
................................ ................................ ................................ ......... 16 Table 10. Lake Istokpoga Basin P Control Practices Implementation Plan for Meeting the

Tributary TMDL
................................ ................................ ................................ ......... 17 Table 11. Estimated Additional Regional Treatment Required to Meet Lake Okeechobee TMDL

with and without Meeting Tributary TMDLs
................................ ............................. 18 List of Abbreviations BAT Best Av ailable Technologies BMAP Basin Management Action Plan BMP Best Management Practice CERP Comprehensive Everglades Restoration Plan cm Centimeters EPA Environmental Protection Agency FDACS Florida Department of Agriculture and Consumer Services FDEP Florida Department of Environmental Protection Fe Ferric ha Hectares IFAS Institute of Food and Agricultural Sciences kg Kilograms mg Milligrams mt Metric Tons NRCS Natural Resources Conservation Service P Phosphorus ppm Parts per million RAS TA Reservoir Assisted Stormwater Treatment Area SFER South Florida Environmental Report SFWMD South Florida Water Management District TMDL Total Maximum Daily Load TP Total Phosphorus yr YearTask 3

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### INTRODUCTION The goal of this final task 3 report is to present a legacy phosphorus ( P ) abatement plan for the northern Lake Okeechobee watershed (Figure 1) based on the findings of the first two tasks of this project . Tasks 1 and 2 quantif ied , mapped , assessed mobility of, and identified abatement practic es for the legacy

P within the watershed based on the available field and literature data obtained during a comprehensive review process . The Statement of Work for this final task provided for two options depending on the adequacy of the findings for developing a meaningful legacy

P abatement plan at this time
. Even though more information would obviously be useful, i t was determined that the current legacy

P knowledge base was suffi cient for developing an abatement plan. If the current information had been dee m ed insufficient, then a research and data acquisition plan would have been developed to obtain the additional information needed before an abatement plan could be developed
. The specific objectives of this legacy P a batement plan were to outline specific P control practices and strategies at different spatial scales , anticipated P reduction performance s , implementation costs , and a general implementation schedule. 

### DEFINI TION OF LEGACY P Legacy p hosphorus (P) is defined as phosphorus within the watershed that is present as the result of anthropogenic activities and has transport potential to Lake Okeechobee
. Antecedent P is defined as the P that occurs naturally in soils based on the native properties of the soils and atmospheric deposition and rainfall. Anthropogenic activities in the Lake Okeechobee watershed have resulted in more imported P into the watershed, as fertilizer, animal feed, and domestic goods, than has b een exported resulting in the accumulation of P in soils, waste storage facilities, and landfills. Figure 1 . Northern Lake Okeechobee WatershedTask 3

– Legacy P 2



### BACKGROUND OF LEGACY P Over the last three decades, Lake Okeechobee has experienced accelerated eutrophication due to excessive phosphorus inputs from anthropogenic activities , particularl y agricultural land uses that dominate in its watershed. Lake Okeechobee’s northern watershed consists of 21 summary basins covering more than 2.65 million acres or 4,100 square miles (Figure 1). F rom 1991 to 2005 P lo ads to L ake Okeechobee from the northern drainage area were 457 metric tons per ye ar (mt/y r) , which were about 83% of the total P load of 549 mt/y r to the lake including 35 mt/y r from atmospheric deposition . These P loads are higher than the established T otal Maximum Daily L oad (TMDL
- FDEP Rules Chapter 62
- 304 ) target by 1 6 0 mt/y r . The northern Lake Okeechobee watershed exceeds its TMDLtarget by 112 mt/y r . An EPA proposed Lake Okeechobee tributary TMDL will likel y set in
- stream P concentration targets somewhere between 7 7 to 1 2 0 ppb. Despite the long history of regulatory

and voluntary

incentive
- based programs to control P inputs into Lake Okeechobee, current P loadings to the lake and P concentrations in the watershed north of the lake remain high. Intensive P management strategies will be needed to lower P loadings sufficiently to meet the TMDL target by 2015. Though the process of P accumulation has been occurring since the late eighteen hundreds, the majority of the accumulation has occurred over the past fifty years. The first major import of P was as fertilizer used for a developing vegetable crop industry around 1915 to 1920, but the vegetable farms disappeared after a brief time due to hard freezes and therefore little P accumulation occurred ( VanLandingham and Hetherington , 1978)
. F rom 1930 to 1940 , a significant increase in the cattle business occurred with beef cattle going from 17,000 head in Okeechobee County in 1930 to 45,000 in 1940. Phosphorus fertilizer was used o n beef pasture at this time, but was fairly limite d due to costs and low animal densities. Beef cattle pastures were fertilize d more aggressively starting in the 19 40s and up through the 1980s, which is the period of the greater legacy P build up. Phosphorus fertilization on beef pastures was essentiall y stopped during the 1990s. The period s tarting in the late 1940s through the early 1960s saw dairy

farms from the southeast coast of Florida move into the area . At their peak during the 1970s there were more than 45 dairi es in the northern Okeechobee basins. More than half of these dairies have since closed as part of the Dairy

Buyout P rogram in the mid to late 1980s and economic pressures. Most of these dairies operated without waste management systems until the 1960s when the US Soil Conservation Service constructed lagoons and seepage fields on most of the dairies. Other best management practices , such as stream fencing, were started on the dairies in 1979
. By 1988 , all of the dairies were operating under FDEP Dairy Rule permits that required BMPs on all dairies. As these permits were transferred to NPDES (EPA) permits , starting about the year 2000, each dairy was required to show nutrient balanc ing across the dairy , which in some case s required additional BMPs
. Res idential and urban development also increased in the basin with its most rapid growth occurring during the last 20 years. The legacy P associated with residential and urban development is from landscape fertilization , the accumulation of P in drain fields and septic tanks, municipal sludge from wastewater treatment plants, and landfills.Task 3

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The findings of Tasks 1 and 2 provided a good picture of where the legacy P is located within the watershed and its relative mobility for eventually washing into the stre ams and ultimately to Lake Okeechobee. The P transport processes and associated practices that influence P transport were also identified. The purpose of this report is to use these data and information to formulate an abatement plan that will meet the T MDLtarget of 140 mt/y of P going to L ake Okeechobee by 2015 and an assumed tributary P TMDL for the watershed
. 

### OVERALL ABATEMENT STRATEGY AND ASSUMPTIONS The overall approach for controlling the legacy P within the northern Lake Okeechobee watershed f

rom entering its tributaries and Lake Okeechobee was to identify where the legacy P is being stored and then identifying practices that c ould most cost efficiently limit its mobility
. Establishing where they

are to be implemented however depend s on where the TMDL P target levels are to be met . The L ake Okeechobee target has been set at 140 mt (112 mt for the northern Lake Okeechobee watershed) , however the tributary TMDL has not been finalized. Th e tributary TMDL target and its associated BMAP will be critical because they directl y influence the legacy

P control measures and ultimately the costs to meet the P reduc tion goals
. Obviousl y designing an abatement program with an unknown target is difficult, therefore for this assessment a tributary TMDLof 1 00 ppb TP was assumed. It is also important to known how rigorous ly the BMAP would enforce this target within tributaries, i.e. would it extend to the limits of the Waters of the State designation or would some flexibility be provided within the secondary and tertiary

reaches for more efficient practices? For this assessment, it was assumed that reason would prevail and upland tributary practice s would allow limited use of design ated waters for treatment s ys tems. Insummary , it was assumed for this proje ct that a tributary TMDL will be established at 1 0 0 ppb TP, but that P control measures could use Waters of the State for conveyance within predominately agricultural areas or individual property boundaries. The assumption that meeting tributary TMDL target s will be required has its greatest impact on those areas that have existing down stream P abatement systems, such as large lakes, extended sloughs, or regional treatment systems. For example for the lakes in the upper Kissimmee basin , particularl y Lake Kissimmee , are currentl y assimilating m ost of the P entering them from their watersheds , and therefore from the Lake Okeechobee TMDL p er spective upland P control practices in this watershed would not be very effective
. The same is true for the Lake Istok poga basin and the extensive slough s ys tem in Fisheasting Creek, though to a lesser extent. A tributary TMDL within these basins obviously negates this advantage and directly affects the P abatement strategies
. An additional issue associated with the downstream systems , which have been assimilating P for years, is that when the ir inflow P concentrations decrease due to upland P control practices they will likely become sources of P
. This means that there can be significant delays between the P load reduc tions in upland tributaries and the P loads entering the Lake Okeechobee , particularl y for these upper basins
. Since the tributary

TMDLs targets will be higher than the Lake Okeechobee TMDL targets and the in
- stream accumulated legacy P could start washing out, there be need for additional P remov al before discharging to the lake . Therefore, it will be necessary to integrate upland PTask 3

– Legacy P 4

control practices with regional treatment s ys tems on the lower tributaries in order to meet the lake TMDL. The approach taken for this abatement plan was to first meet the tributaries TMDL and then to do regional treatment to obtain the additional P reductions needed to meet the Lake Okeechobee TMDL. 

### LEGACY AND OTHER P SOURCES In order to develop an abatement plan it w as first necessary to understand and quantify where the P is coming from and how it is moving through the stream s ys tem. The 2008 S F ER provided the flow and P loads from 1991 through 2005 for all of the basins that drain to L ake Okeechobee. This information was reordered in Table 1 to separate out the northern Lake Okeechobee watershed data and to compare these data to the Lake Okeechobee TMDL and the assumed tributary TMDL targets . The measured data were used to verify the assessment tool developed as part of this project. This assessment tool predicts the P loads to streams by land use and P source category for the three primary basins within the northern Lake Okeechobee watershed based on the assumed mobility factors shown in Table 2. Table 3 provides the predicted P loads based on the soil based legacy P information developed during task 2 of this project , while Table 4 provides the predicted native and other anthropo genic P loads from the various land uses
. These land use based P source data were then combined with estimated assimilation rates within the streams, sloughs, and lakes to predict net basin outflows (Table 5 ). These predicted net basin P loads were then compared to measured data and the Lake Okeechobee and tributary TMDL targets (Table 6 ). Table 6 is useful because it provides an indication of the percentage reductions required to meet the TMDL s. These results also make it clear that meeting the tributary TMDL targets will not be sufficient to meet the lake TMDL targets, and therefore either the land source d P loads will have to be reduced significantl y below tributary TMDL targets or additional in
stream treatment will be needed or a combination of both.


### PHOSPHORUS CONTROL PRACTICES This section describes the P control practices that are integral to the abatement plan. The P control practices used in the plan can be categorized into one of the following spatial groupings that define the scale and type of P source to be addressed: 1. In
- Field

– Field practices that address the legacy P and its mobility

within the soil/plant environment. 2. Edge
- of

- Field/Farm (EOF)

– Practices that treat and/or retain runoff as it is leaving a field or farm. 3. Residential

– Practices applied within residential areas. 4. Urban

– Practices applied within tran sporation/urban/commercial/industrial areas 5. Facilities

– Practices used in non soil
- based areas that potentially discharge P into runoff, such as industrial sites, packing houses, old land fills, etc. 6. Regional

– Practices that treat and/or retain stream f lows within the tributary s ys tem where multiple upstream landowners drain to the system.Task 3

– Legacy P 5

Table 1 . Surface water inflows, TP concentrations, loading rates, and TMDL targets for Lake Okeechobee Tributary Basins (1991 - 2005)Task 3

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Table 2 . Assumed P mobility factors for legacy, native, and anthrogenic P sourcesTask 3

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Table 3 . P loads from Soil Based Legacy P for Various Land UsesTask 3

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Table 4 . P loads from Native and Non - S oil Based Legacy P Anthropogenic Sources for Various Land UsesTask 3

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Table 5 . Predicted P Source Loads to Stream, In - stream Assimilation, and Net Basin Export ( 1991 - 2005)

Table 6 . Measured and Estim ated P Source Loads to Stream and Net Basin Exports with TMDL TargetsTask 3

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The following sections will describe the individual P control practices within each of these categories and provided estimated P removal efficiencies in terms of dollars per pound of P removed. 

### In - Field Agricultural BMPs Previous studies and reports have estimated the effectiveness and cost of agricultural BMPs for the Okeechobee basin as described in the task 2 report
. FDACS has been instrumental in the development and implementati on of agricultural BMP around the Lake Okeechobee watershed and the rest of Florida. They have a series of BMP manuals for a variety of commodities. These manuals, however, do not provide specific information on P reduction performances or costs. Theref ore, the l etter report (Bottcher, 2006) entitled: “ Phosphorus Reduction Performance and Implementation Costs under BMPs and Technologies in the Lake Okeechobee Protection Plan Area ” was used for providing the agricultural BMP response and cost data . This letter report summarizes the available BMPs and provides ranges and ty pical condition implementation costs and estimated P reductions. The ty pical condition was developed to account for that fact that some farms already have BMPs and for the fact that BM Ps effectiveness also varies due to site
specific conditions , such as soils. Because of the complexity and diversity

of the northern Lake Okeechobee basins the following assumptions had to be made to complete this assessment. First it was assumed that an integrated BMP program would be implemented instead of trying to deal w ith individual BMPs implementation strategies, i.e. the ty pical BMP implementation condition developed in the letter report was be used. Secondly , to roughl y account for variable soil conditions between the three primary basins, the northern Lake Okeechobee basins were categorized as being predominately flatwood soils while the other two basins were categorized as ridge soil dominated. This adjustment was done because the well drained ridge soils have considerabl y less P transport potential than flatwood soils , thus reducing the legacy P influences on P losses . Table 7 summarizes of the assumed BMP reduction performance and relative costs for the agricultural land uses used for this p lan’s development
. 

### In - Field Soil Amendments A few studies have looked at the benefits of applying soil amendment s to reduce the mobility of the accumulated legacy

P in the soils. The soil amendments evaluated have been lime, gy psum, silica, aluminum and iron salts, and water treatment residuals. The intent of these compounds is to either raise pH to enhance P binding or to directly bind P to the applied compounds. Though these soil amendments can significantl y reduce P they have three disadvantage s that greatly limit their effectiv eness for control ling P. First, soil amendments attempt to tre at the entire legacy P pool within the soil , which is about 50 to 2 00 times larger than the P being discharged per year. This means large amounts of chemicals hav e to be applied at high cost. Second, it is very difficult to get the amendments mixed into the soil adequatel y to maximize there effectiveness. Finally , soil amendments do not reduce the amount of legacy P in the soil and over time many of the amendment s can los e their binding properties and the legacy P can be come mobile again. Lim eTask 3

– Legacy P 11

Table 7 . Phosphorus Control Practices - Assumed Effectiveness and CostsTask 3

– Legacy P 12

and iron salts are particularly vulnerable to remobilization. Therefo re, soil amendment s were not considered a viable P control practice in this plan
. 

### Edge - of - Field/Farm (EOF) Treatment Technologies Edge
- of
- field /farm (EOF) P control practices are grouped together because they use identical technologies and onl y diff er in the phys ical location of their implementation. The concept behind EOFs is that they

need onl y treat the P leaving the field or farm and not the entire pool of legacy P in the field or farm. This means that all of the natural P assimilation processes up stream of the EOF can be taken advantage of before treatment. The Dairy BAT project discussed in the Task 2 report evaluated and ranked EOF technologies and then constructed and tested four s ys tems in the northern Lake Okeechobee basin. This project foun d that EOF systems for high P source areas are the most cost effective P control practice that can be implemented. However, the relative cost effectiveness of EOF s ys tems decrease s as the P concentration in the field or farm runoff decreases, where 2.0 pp m P runoff will cost about $20 /lb
- P removed

/y r as compared to about $120 /lb
- P removed /y r for 0.35 ppm P runoff. Table 7 summarizes the assumed reduction performance and relative costs for EOF systems for various land uses used for this plan’s development. 

### Residential and Urban Residential P control practices include site level and EOF s ys tems. Site level practices are ty picall y landscape management BMPs, such as fertility and water management practices . The EOF s ys tems include standard stormwater retention/detention practices and possible chemical treatment for pass
- thru waters. The estimated responses and costs are based on Harvey Harper’s work included in the 2006 letter report (Bottcher, 2006). Table 7 summarizes the assumed P reduction performance and relative costs for EOF sy stems for various urban land uses used for this plan’s development. 

### Facilities or Point Sources Direct discharges from point sources and other industrial and commercial operations were considered in the overall P balance for the watershed, but were not included as a control option within this plan because these sources ty picall y do not include the mobility of accumulated legacy P and are assumed to be under existing FDEP permits, so additional modifications to these facil ities w ere assumed unlikely . Therefore, no practice s were applied to these sources; however it is strongly

encouraged that these sources be periodically review ed for their relative contributions and control practices.Task 3

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### Regional In - Stream Treatment Tech nologies The final option for controlling P loads going into Lake Okeechobee is to treat the water flowing within the stream network at selected regional locations. The primary advantage of regional treatment, particularl y nearest to the lake, is that only the P that is headed into the lake would be treated, thus taking full advantage of the other assimilative processes within the watershed. The two primary

disadvantages are that tributary TMDLs upstream of the regional sy stems are not addressed and the fact that treatment of mixed or diluted flows will be less efficient than treating closer to the higher P source areas. Two regional treatment technologies were considered for this project, which were a reservoir assisted stormwater treatment areas (RASTA s) that use a reservoir to buffer flows and depths within a wetland treatment areas that provide P removal treatment and a retention/detention reservoir s ys tem using chemical treatment for its pass - thru waters. Even though the chemical treatment system wa s found to be more cost efficient, it was not included in the plan due to a directive from the District that chemical treatment at the regional scale would not be acceptable. However, it is recommended that because of its high efficiencies and lower cost, further investigation s be conducted to verify or disprove the stated concerns over chemical treatment. The release and assimilation of legacy P within the stream network is an important issue to address when considering the placement of regional treatment s ys tems. Wetland sloughs and lakes can assimilat e and release P depending on the difference between current inflow P concentrations and long term historical inflow P concentrations. Over time these wetlands and lakes will trend toward an equilibrium w ith inflow P concentration , but in the case of large lakes and slough system s it is unlikely that they have reach such an equilibrium and therefore are still assimilating P. However, as inflow P concentrations are reduced these sloughs and lakes might beg in to release either native or legacy accumulated P. Therefore placing regional treatment system upstream of such sy stems could greatl y reduce its effectiveness especially in the short term. In time the accumulate d P in these system s will wash out to est ablish a new equilibrium with the inflow P levels. S loughs will likely respond within five to twenty years as compared to the larger lakes taking perhaps five to ten times longer to establish a new equilibrium. Therefore it recommended the regional treatment s ys tems not be placed upstream of sloughs and lakes. Table 7 summarizes the assumed reduction performance and relative costs for the regional treatment s ys tems used for this plan’s development. 

### ESTIMATED IMPLEMENTATION LEVELS AND COSTS TO ACHIEVE TMDL TARGETS This section spatially

assigns P control practices across the watershed to achieve both the Lake Okeechobee and assumed tributary TMDL targets based on the 2006 land use GI S coverage and assumed P control practices’ performance s and costs. The approach taken was to appl y P control practices for meeting the tributary TMDLs first, and then to apply additional practices as needed to meet the Lake Okeechobee TMDL. The method of appl ying P control practices was to appl yTask 3

– Legacy P 14

the most cost effective practice first, and then to add practices as needed to meet the TMDL target s for each land use. The implementation of a modest “ty pical” BMP program was found to be the most cost effective initial P control practice for the watershed , and therefore was applied first across the watershed. To keep the logistics of BMP implementation to a manageable level , site or field level BMPs were applied as a suite of BMPs as previousl y identified as the most appropriate combination by Bottcher ( 2006). The next P co ntrol practice implemented was stormwater retention , which includes wetland restoration and water reuse , as well as standard urban R/D sy stems . Finally , chemical treatment was added to the retention based systems if the first two practices were not suffic ient to meet TMDL targets. Tables 8 through 10 show the existing P loads to the tributaries, the tributary TMDL target, required P load reduction, P load reductions by P control practice s , and annual costs for each land use category within the three primary basins. The TMDL targets for the individual land uses were adjusted to account for the dilution effect of runoff from low er P concentration sources, such as native areas, groundwater contributions, and reduced P concentration s due to long term P assimilation in lakes and sloughs . These adjustment factors are provided as a footnote in the tables . They clearly show that the northern Lake Okeechobee basins have the le ast dilution effect thus requiring greater relative P reductions than for similar land uses for the other two primary

basins, particularl y compared to the Upper Kissimmee regional basin that had the greatest P dilution advantage. These tables also show that the relative importance of the various land uses with improved beef pasture s bein g the dominant source of P in the watershed . Nearl y 80% of the P load reduction needed in the northern Lake Okeechobee basin is associated with improved beef pasture while about 60% and 70% P reductions are needed for improved beef pasture for the Lake Is tokpoga and Upper Kissimmee basins, respectivel y. It was also found that BMPs and retention practices alone were not sufficient for improved beef pastures to meet tributary TMDL target s except within the Upper Kissimmee basin because of the lower P load reductions required in this basin. As anticipated onl y the more intensive dairy and vegetable land uses required EOF chemical treatment to meet tributary TMDL targets. The cost for implementing the P control practices to meet the tributary TMDLare also show in Tables 8 through 10. These costs include both the amortized capital costs and annual operation and maintenance costs so that a direct comparison can be made as to the long term investment required to meet the TMDLtarget s . The annual costs are obviously closely related to the P load reductions, but the lower P load sources do have higher relative costs compared to high P load sources on a cost per pound of P removed basis
. The estimated total annual cost for meeting the tributary TMDL throughout the northern Lake Okeechobee watershed is about $54 million with about half going to O&M costs and the remaining being the 20
- year amortized initial outlay of capital expense s including land, equipment, and construction. This means about $270 million of initial capital expenditures would be needed for all three primary basins to meet the tributary TMDLtarget .Task 3

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Table 8 . Northern Lake Okeechobee Basin P Control Practices Implementation Plan for Meeting the Tributary TMDLTask 3

– Legacy P 16

Table 9 . Upper Kissimmee Basin P Control Practices Implementation Plan for Meeting the Tributary TMDLTask 3

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Table 10 . Lake Istokpoga Basin P Control Practices Implementation Plan for Meeting the Tributary TMDLTask 3

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Table 11 . Estimated Additional Regional Treatment Required to Meet Lake Okeechobee TMDL with and without Meeting Tributary TMDLsTask 3

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Table 11 provides estimates of the additional regional treatment required to meet the Lake Oke echobee TMDL for three conditions; 1) tributary TMDL not addressed, 2) tributary TMDL is met and existing wetlands and lakes equilibrate to the TMDL levels, and 3) tributary TMDL is met and existing wetlands and lakes will maintain current P discharge leve ls. It is assumed that the regional treatment is implemented downstream of any significant P sinks or sources, such as lakes or wetland sloughs to maximize the ir benefits. As seen in Table 11 the current P loads leaving the Lake Istokpoga and Upper Kiss immee basins are already in compliance with the assumed tributary

TMDL due to the ir significant buffering effect in these basins. This means that achieving tributary

TMDLtargets within these basins will have a minimum benefits for achiev ing the Lake Okee chobee TMDL. In fact, since the assumed tributary TMDL targets in these basins are actually higher than current P discharge s, it is possible that over time these lakes will ultimately

come into equilibrium with tributary TMDL
. To account for this possibl y, two tributary TMDL scenarios are presented in Table 11 , which reflect the future condition that the lakes do come into equilibrium with TMDL or that the lakes will continue to buffer P concentrations in their outflows to current levels . A third scenari o presented in Table 11 is for the condition where tributary TMDLs are not implemented, so that only the L ake Okeechobee TMDLtarget has to be met. The predicted results indicate that current up stream P assimilation or buffering b y the large lakes is reducing the P load treatment needs by about 16 mt per year, which translates into an annual savings of about $5.2 million. Assuming that the lakes continue to buffer P and the tributary TMDL targets are met, then it would cost about $47 million per year to p rovide the additional treatment needed to meet the Lake Okeechobee TMDL . However, if no tributary TMDL P control practices are implemented, then it would take about $106 million per ye ar (about $700 million of capital expenditures) to meet the Lake Okeech obee TMDL or about $60 million per year more than if the tributary TMDL targets were already met . Comparing this to the estimated $54 million per year for meeting the tributary TMDL means that it would be less expensive to meet both TMDL target s together than it would be trying to meet the Lake Okeechobee TMDL b y just doing regional treatments.


### IMPLEMENTATION SCHEDULE Previous sections presented the recommended P control practices required to meet the tributary and lake TMDL targets based on the 1991
- 2005 discharge data and average implementation conditions over that period. This means that the P control practices implemented since 200 0 were not reflected in the presented results and therefore must be included in any implementation plan based on these results. Hence , the following implementation schedule includes the period staring in 2000 and any

moneys spent on the P controls after this date would be included in the cost estimates presented in the previous section, thus reducing future expenditures. The plan development requires set goals for when both the tributary and Lake Okeechobee TMDL s are to be met. The stated goal for meeting the Lake Okeechobee TMDL is 2015 where there is currentl y no set timeline for the tributary TMDL
. The concern of different target compliance dates for the TMDL s is that the relative response times of various P controls practices will impact when and where TMDL targets can be met . The tributary or upland P controls, particularl y BMPs , may take several years for their full benefits to be realized whileTask 3

– Legacy P 20

EOF and regional treatment system will have much quicker P reduction responses. This means that even if the described tributary and regional P controls practices are fully implemented by 2015, the Lake Okeechobee TMDL t arget will likely not be fully

met for another five to ten ye ars. Therefore, to achieve compliance with the Lake Okeechobee TMDL in 2015, the quicker response P controls, such as EOF and regional treatment, must be implemented at levels greater than what would be needed when future equilibrium conditions are realized. I f the compliance date for the tributary

TMDL s is also set to 2015, then the retention and EOF upland P control practices would have to become the higher priority. The compelling argument f or going with the more intensive upland EOF s ys tems is that you can obtain fast P reduction responses while not having to temporary

overbuild regional treatment systems while waiting for the slower response BMPs to take their full effect
. Making the ass umption that me eting both tributary and Lake Okeechobee TMDL s by 2015 would be the preferred goals and that temporaril y overbuilding regional treatment systems is not cost effective the following a generalized implementation schedule is recommended . The highest priority should be placed on EOF s ys tems on the highest P source areas within the Northern Lake Okeechobee basin. BMPs should also remain as a very high priority

because in the long run they provide the most cost effective P reduction response. Re gional treatment must also continue to be implemented, but only to the level needed to address the equilibrium condition with the tributary TMDL.


### REFERENCES Bottcher, A. B. 2006. Phosphorus Reduction Performance and Implementation Costs under BMPs and Technologies in the L ake Okeechobee Protection Plan Area . Letter report provided to the South Florida Water Management District.