Letter Report by SWET, Inc. 1

August 8, 2006 

Ms. Joyce Zhang 

South Florida Water Management District 

3301 Gun Club Road 

West Palm Beach, Florida 33406 

SUBJECT: Letter Report Entitled: Phosphorus Reduction Performance and Implementation 

Costs under BMPs and Technologies in the Lake Okeechobee Protection Plan Area 

Dear Joyce: 

I have completed my re-evaluation of the phosphorus (P) reduction performance and 

implementation costs that Dr. Harper and I previously submitted to Ms. Benita Whalen as a 

letter report on October 20, 2003. The primary purpose of this re-evaluation was to update the 

values in the previous report and include one additional agricultural land use category 

(ornamentals) and separate range/woodland pastures from unimproved pastures. The urban 

land use category was also broken out into more detail. 

To complete these tasks, a workshop was organized and held with leading agricultural experts 

with specific knowledge of BMP implementation practices and effectiveness. The workshop 

was held in Gainesville, FL on May 23, 2006 with the following attendees: Joyce Zhang 

(SFWMD), Drs. Don Graetz and Tom Obreza (Soil Science, UF), Drs. Roger Nordstedt, Ken 

Campbell and Sanjay Shukla (ABE, UF), Dr. Ed Hanlon (Director, SWFREC, UF), and Dr. 

Patrick Bohlen, Director of Research, MacArthur Agro-ecology Research Center. Dr. Ike 

Ezenwa (Agronomy, UF) was later contacted with regards to sand-land sugarcane production 

practices. The workshop was invaluable to determining the latest research and crop 

management practices for the primary crops grown in the Lake Okeechobee basins. The 

appropriate values for existing and BMPs practices for each agricultural land use were 

discussed in detail with updated values being developed by group consensus. The following 

are the primary changes developed by the group: 

1. Table 1 from the previous report was reorganized to eliminate confusion for the listed 

primary land uses. Also, one of the land uses (ornamental), which was previously 

under other land uses, was considered significant enough to be analyzed separately 

during this assessment. 

2. The stormwater retention and wetland restoration BMPs were separated with 

significantly less emphasis being placed on wetland restoration P reductions due to 

recent field data that show these restoration projects are less effective than originally 

thought. It is also important to note that it is assumed that stormwater retention 

systems will not impact in-field water tables because if they did, then they could 

adversely affect P loads. Also, it is assumed that the retention ponds are not 

constructed on fields with historic high P levels, or if they are the land is treated with 

alum prior to flooding. 

3. Existing unit loads and BMP reductions from unimproved pastures were redone so 

that there would be a difference between unimproved pasture and range/woodland 
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pastures. The workshop group agreed that the typical definition of unimproved 

pasture has animal densities and grass and fertility practices somewhere in between 

the improved and range/woodland pastures categories. Table values were adjusted 

accordingly. 

4. The land use category of ornamentals was added and assumed to be an intensive 

ornamental nursery operation, but it is recognized that ornamental field crops, such as 

caladiums, may also be mapped under this category. However, ornamental field crops 

would be more similar to row crops than nurseries, and therefore it is suggested that 

for now the row crops table be used for ornamental field crops. 

5. An assessment table for the land use category of field crops was added and assumed 

to be a hay field that is fertilized with P. The workshop group helped develop 

estimates for existing and BMP P reduction and cost estimates. 

6. The workshop group found the previous P fertilizer rates for citrus to be high because 

P fertilization on citrus typically only occurs over the first few years after planting. 

This change significantly reduced the potential P reductions for the fertility BMP. 

7. There were a few other minor changes made to P reduction ranges and typical values 

and the estimated costs of implementation as suggested by the workshop group. Most 

of these changes were associated with stormwater retention and the fertility BMP. 

8. An assessment table was also developed for the urban land use category because of 

this land use’s importance in any watershed BMP implementation programs. 

The overall findings from this assessment are provided in Table 1 while the detailed updated 

assessments for the primary agricultural and urban land uses are provided in Attachment 1. As 

before, it is anticipated that the implementation of owner and typical cost share BMPs in the 

urban and agricultural sectors will still provide approximately a twenty five (25) percent 

reduction in phosphorus loads into the tributary streams within the Okeechobee basin. 

Additional reductions could be achieved by a more aggressive BMP implementation program 

within the basin. The reductions shown are for what are called a “typical” BMP 

implementation level under a moderately aggressive program that assumes a limited amount of 

cost share support will be available for farmers and urban landowners. 

Table 2 provides estimates of the tons of P reduction that might be expected across the 

Okeechobee basin, excluding the Upper Kissimmee Chain of Lakes basins, based on BMP 

efficiencies presented in Attachment 1 and the most recent (2006) land use data provided by the 

District. This table uses the same unit loading estimates as presented in Table 1. 

It is recommended that the values in this report be updated periodically as additional research 

and field data come available. 

Sincerely, 

Del Bottcher, Ph.D., P.E. 

Enclosures: Table1, Table 2, and Attachment 1 
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Attachment 1 - Letter Report by SWET, Inc. A- 1

ATTACHMENT 1 

Current condition assumptions, existing P loads, potential P load reductions, 

and costs of implementation for the primary land uses within the Okeechobee 

basin. 

 (Updated 8/8/06) 

Table of Contents for BMP Assessment Tables 

Citrus A- 2 

Cow Calf Production – Improved Pasture A- 3 

Cow Calf Production – Unimproved Pasture A- 4 

Cow Calf Production – Rangeland/Woodland Pasture A- 5 

Dairies A- 6 

Field Crops - Hayland A- 7 

Ornamentals A- 8 

Pineland A- 9 

Row Crop A-10 

Sod / Turf Farm A-11 

Sugarcane – Sandland A-12 

Urban A-13 
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Attachment 1 - Letter Report by SWET, Inc. 
Attachment 1 - Letter Report by SWET, Inc. 
Attachment 1 - Letter Report by SWET, Inc. 
Attachment 1 - Letter Report by SWET, Inc.