MODEL-BASED ESTIMATES OF TOTAL 

NITROGEN LOADING TO TAMPA BAY: 

CURRENT CONDITIONS AND UPDATED 

2010 CONDITIONS 

Prepared for: 

Tampa Bay Estuary Program 

Mail Station I-1/NEP 

100 8th Avenue SE 

St. Petersburg, FL 33701 

Prepared by: 

A. Janicki, R. Pribble, H. Zarbock, 

S. Janicki, and M. Winowitch 

1155 Eden Isle Drive NE 

St. Petersburg, FL 33704 

July 2001 

 
FOREWORD 

This report was prepared by Janicki Environmental, Inc. under the direction of Mr. Dick 

Eckenrod and Ms. Holly Greening of the Tampa Bay Estuary Program. This work was 

performed under Contract No. T-98-06 for the Tampa Bay Estuary Program. 

ii
ACKNOWLEDGMENTS 

Many individuals and groups contributed to the completion of this report through review 

and technical insight, and by providing data and other information vital to this analysis. 

Special thanks are extended to the following groups and individuals for their assistance: 

the SWFWMD/TBEP Joint Water Quality Subcommittee; Mr. Bruce DeGrove, Florida 

Phosphate Council; Mr. Richard Eckenrod, Tampa Bay Estuary Program; Ms. Holly 

Greening, Tampa Bay Estuary Program; Ms. Sheri Lovely, Pinellas County Utilities; Mr. 

Charles Kovach, Florida Department of Environmental Protection, Tampa Office; and Ms. 

Marsha Reese, Environmental Protection Commission of Hillsborough County. 

iii
TABLE OF CONTENTS 

FOREWORD ii

ACKNOWLEDGMENTS iii 

1 INTRODUCTION 1-1

1.1 Objectives 1-2

2 ATMOSPHERIC DEPOSITION 2-1

2.1 Current Conditions Atmospheric Deposition Loading Estimates 2-1 

2.1.1 Data Sources 2-1 

2.1.2 Methods 2-1 

2.2 2010 Conditions Atmospheric Deposition Loading Estimates 2-2 

 2.2.1 Data Sources 2-2 

 2.2.2 Methods 2-3 

3 DOMESTIC AND INDUSTRIAL POINT SOURCES 3-1 

3.1 Current Conditions Point Source Loading Estimates 3-1 

3.1.1 Data Sources 3-1 

3.1.2 Methods 3-2 

3.2 2010 Conditions Point Source Loading Estimates 3-3 

 3.2.1 Data Sources 3-4 

 3.2.2 Methods 3-4 

4 SPRINGS AND GROUNDWATER 4-1

4.1 Current Conditions Springs and Groundwater Loading Estimates 4-1 

4.1.1 Data Sources 4-1 

4.1.2 Methods 4-1 

4.2 2010 Conditions Springs and Groundwater Loading Estimates 4-2 

 4.2.1 Data Sources and Methods 4-2 

5 MATERIAL LOSSES 5-1

5.1 Current Conditions Material Losses Loading Estimates 5-1 

5.1.1 Data Sources 5-1 

5.1.2 Methods 5-1 

5.2 2010 Conditions Material Losses Loading Estimates 5-1 

 5.2.1 Data Sources and Methods 5-1 

 

6 NONPOINT SOURCES 6-1

6.1 Current Conditions Nonpoint Sources Loading Estimates 6-1 

6.1.1 Data Sources 6-1 

6.1.2 Methods 6-3 

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6.2 2010 Conditions Nonpoint Sources Loading Estimates 6-6 

 6.2.1 Data Sources 6-6 

 6.2.2 Methods 6-11 

7 RESULTS OF LOADING ANALYSIS 7-1

 7.1 Current Conditions 7-1 

 7.2 2010 Conditions 7-7 

8 CONCLUSIONS 8-1

9 LITERATURE CITED 9-1

APPENDIX 1 Individuals Contacted for Future Conditions Point Source Information and 

Summary of Interviews 

APPENDIX 2 Aggregated Florida Land Use and Cover Classification System Categories 

APPENDIX 3 Land Use-Specific Seasonal Runoff Coefficients 

APPENDIX 4 Land Use-Specific Runoff Water Quality Concentrations 

APPENDIX 5 Existing and Projected Future Land Use Acreages 

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1. INTRODUCTION 

One of the primary goals established in the Tampa Bay National Estuary Program (TBNEP) 

Comprehensive Conservation and Management Plan (CCMP) (TBNEP, 1996) is to restore 

seagrass extent in the bay to levels similar to those observed in the 1950s. Seagrass extent 

and condition can be impacted by many factors, including water quality. 

To attain the seagrass restoration goal, the TBNEP developed the Nitrogen Management 

Strategy. The Strategy seeks to prevent future impacts due to excessive nitrogen loadings to 

Tampa Bay. To provide quantifiable goals for the Strategy, a paradigm that relates nitrogen 

loading to water quality and restorable seagrass acreage was utilized, as shown in Figure 1-

1. 

TN LOAD CHLOROPHYLL LIGHT

ATTENUATION

SEAGRASS LIGHT

REQUIREMENT

SEAGRASS

COVERAGE

Figure 1-1. TBNEP Nitrogen Management Paradigm. 

To quantify the relationships represented in the paradigm, empirical relationships between 

external total nitrogen (TN) loads and chlorophyll a concentrations, between chlorophyll a

concentrations and light attenuation, and between light availability and restorable seagrass 

area were developed and presented in Janicki and Wade (1996). These relationships were 

developed for the Old Tampa Bay (OTB), Hillsborough Bay (HB), and Middle Tampa Bay 

(MTB) segments. 

Using these relationships, predictions of the responses in chlorophyll a concentrations, 

light attenuation, and the extent of seagrass restoration to changes in external TN loading 

were derived. 

The model predictions suggested that seagrass restoration goals could be met by meeting 

chlorophyll a concentration and light attenuation targets for the four mainstem bay 

segments. Two sets of chlorophyll a targets were considered, as follows: 

• the chlorophyll a concentrations which would be expected to result in 

restoration of 95% of the seagrass goals for the segments; and 

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• the mean chlorophyll a concentrations observed during the 1992-94 period, 

i.e., current conditions at the time. 

The latter set was considered since all evidence suggested that seagrass areal coverage had 

been increasing since 1988. It was concluded that the more prudent targets would be the 

lower of these two sets for each bay segment. Light attenuation targets were set based on 

the segment-specific depths necessary to allow for attainment of 95% of the seagrass goals. 

The estimated 1992-1994 mean annual TN loads represent those loads identified by the 

TBNEP expected to result in light availability sufficient to meet the seagrass restoration 

goals. The empirical model relating total nitrogen loads to seagrass restoration goals 

(Janicki and Wade, 1996) suggested that light availability necessary for obtaining seagrass 

restoration goals could be met by establishing a “hold the line” strategy for nitrogen loads. 

This strategy would hold nitrogen loads to each segment of the bay to the average levels of 

1992-1994. The Tampa Bay Nitrogen Management Consortium adopted this strategy in 

1996. 

To implement this strategy, local government partners agreed to preclude increases in 

future nitrogen loadings to the bay. The ca. 2010 total nitrogen loading estimates 

presented in Zarbock et al. (1996a) were developed to quantify expected TN loading 

increases, and were used for the TBNEP Allocation Workshops. 

1.1 Objectives 

The Tampa Bay Estuary Program (TBEP) is currently performing an update of the estimated 

TN loadings for the ca. 2010 period. This update incorporates the best available 

information as of 2000 for estimating ca. 2010 TN loads. The objective of this report is to 

update the expected future nitrogen loading from external sources to each bay segment 

for the year 2010. The annual average loading estimates for 2010 are derived from 

estimated future monthly loading estimates, using methods similar to those used previously 

(Zarbock et al., 1996a). In additional, this update contains the modeled TN loading 

estimates for current conditions. 

Loading estimates were developed for each of the seven segments of Tampa Bay (Figure 1-

2). The loading sources examined include: 

• atmospheric deposition, 

• domestic and industrial point sources, 

• groundwater and springs, 

• material losses from fertilizer handling facilities, and 

• nonpoint sources. 

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The following sections present descriptions of the data and methods used for the estimated 

current and 2010 TN loadings from each loading source in the Tampa Bay watershed 

(Figure 1-3). Then a summary of the estimated TN loadings by bay segment, and the 

estimated loadings by bay segment and jurisdiction, for 2000 and 2010 is provided, 

followed by the conclusions. 

Jurisdictional loads were estimated for Hillsborough, Pinellas, and Manatee counties, and 

the cities of Tampa, St. Petersburg, Clearwater, and Bradenton. Estimated loadings 

originating in Polk, Pasco, and Sarasota counties were incorporated into the bay segment 

TN loadings, but were not incorporated into the jurisdictional loadings. Only land-based 

sources of TN were accounted for in the jurisdictional loadings. Atmospheric deposition, 

springs, and groundwater loadings were not apportioned to any county or municipality. 

1-3
 

Figure 1-2. Bay segments of Tampa Bay. 

1-4
 

Figure 1-3. Major basins of the Tampa Bay watershed. 

1-5
2. ATMOSPHERIC DEPOSITION 

2.1 Current Conditions Atmospheric Deposition Loading Estimates

Atmospheric deposition is defined as the pollutant load delivered to the surface of 

the bay from the fallout of airborne pollutants, including both rainfall (wet) and 

airborne (dry) pollutants. Only nutrients delivered to the open water estuary were 

accounted for as atmospheric input. 

2.1.1 Data Sources 

The methods used for estimation of the current TN loading were the same as those 

used previously, with the exception of the precipitation nitrogen concentration data 

and the ratio of dry to wet nitrogen deposition. Descriptions of the methods used in 

both the previous current condition estimate (Zarbock et al., 1996a) and the 

updated current conditions estimate are provided below. 

The previous current loading estimate utilized the best available data for developing 

the TN loading from atmospheric deposition. Estimates of atmospheric deposition 

loads were derived from the 1992-1994 NWS rainfall records and precipitation 

concentration data from the NADP Verna Wellfield site. The ratio of dry:wet 

deposition was 2.04:1, as in the estimate of 1992-1994 loadings (Zarbock et al., 

1996b). 

This updated loading estimate for current conditions differed from the previous 

estimate by utilizing more site-specific information for precipitation concentration 

and dry deposition. In August 1996, the TBEP initiated monitoring as part of the 

Tampa Bay Atmospheric Deposition Study (TBADS). This program includes 

sampling elements for both wet and dry deposition at an intensive monitoring site 

located on the Gandy Bridge Causeway. The data available from TBADS that can 

be used to estimate atmospheric deposition to Tampa Bay include nitrogen 

concentration data, wet and dry deposition rates, and an estimate of the ratio of 

dry:wet deposition. These data, together with the 1992-1994 hydrologic load from 

rainfall, were used to update the estimate of current conditions atmospheric 

deposition TN loading. 

2.1.2 Methods 

Precipitation volume (rainfall depth times the open water area of the bay) and 

pollutant concentration data were used to estimate pollutant loadings delivered 

directly to the estuary via atmospheric deposition. Wet deposition loadings were 

calculated on a monthly basis for each bay segment by multiplying the precipitation 

volume (expressed as volume per unit time) by the pollutant concentration 

(expressed as mg/L). The monthly mean precipitation-weighted TN concentration in 

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rainfall was derived from the TBADS data for the period August 1996 through 

December 1998, and multiplied by the monthly mean 1992-1994 hydrologic load 

due to rainfall to derive the wet TN loading estimate for the current condition. 

Pollutants are also delivered to the bay via dry deposition. Monitoring at the 

TBADS site also provided data concerning atmospheric concentrations of nitrogen. 

Utilizing these data, meteorological data, and a deposition model, dry fluxes of 

nitrogen to the surface of the bay were estimated (Pribble et al., 2001). Seasonalspecific ratios of dry:wet deposition were then estimated. These ratios were used to 

estimate monthly atmospheric deposition from both wet and dry deposition. 

2.2 2010 Conditions Atmospheric Deposition Loading Estimates 

The same NWS precipitation data that were used for 1992-1994 atmospheric 

deposition loading estimates were used for future condition loading estimates. 

These data were used to develop average monthly rainfall, so that only the rainfall 

chemistry concentrations and the dry:wet deposition ratio were different for this 

future condition update. 

2.2.1 Data Sources 

The predicted change in nitrogen emissions used in the development of the 

previous 2010 loading estimate was an increase of 10% between 1994 and 2010 

(Zarbock et al., 1996a). The estimate utilized wet precipitation chemistry from the 

NADP Verna Wellfield site, estimated rainfall volumes based on a rainfall surface 

developed from data collected at 22 NWS sites, and a ratio of dry:wet deposition of 

2.04, as suggested by the FADS study (ES&E, 1987). 

The updated 2010 TN loading estimate utilized more recent projections of a decline 

in atmospheric nitrogen emissions. The decline is based on changes in emissions 

expected to occur from the Tampa Electric Company (TECO) Big Bend and F.J. 

Gannon facilities. In 1997, these two facilities accounted for approximately 80% of 

the stationary point source nitrogen emissions from Hillsborough and Pinellas 

counties. As a result of a federal agreement, a reduction in NOx emissions from the 

two facilities by approximately 90% will occur between 1997 and 2010 (TECO, 

2000). These reductions constitute a 46% reduction in NOx emissions from 

Hillsborough and Pinellas counties compared to 1997 levels. 

NOx emissions from mobile on-road sources are not expected to change 

significantly by 2010 (FDEP, 2000). Projected increases in the numbers of 

automobiles are expected to be offset by implementation of EPA emissions 

standards taking effect in 2004, yielding no net change in NOx emissions from 

mobile on-road sources. 

2-2
The monthly average precipitation-weighted TN concentrations for the 2010 period 

were derived from the TBADS data for August 1996 through December 1998. 

These data were used with the 1992-1994 rainfall data to derive an updated future 

condition atmospheric loading estimate. 

2.2.2 Methods 

For the purposes of the updated 2010 atmospheric deposition, the simplest method 

of relating changes in atmospheric nitrogen concentration to changes in emissions 

was used, as in the previous estimate. A reduction in atmospheric nitrogen 

concentrations was considered to be linearly related to a reduction in atmospheric 

emissions. For these purposes, it was assumed that atmospheric emissions 

remained unchanged in 2010 from the emissions for 1997 from sources other than 

stationary point sources. The reduction in emissions resulting from the scheduled 

modifications to the TECO facilities, and the projected no net change in on-road 

mobile sources emissions, correspond to a reduction in atmospheric emissions of 

46% by 2010. For this estimate, the 46% reduction in atmospheric emissions by 

2010 corresponds to a 46% reduction in atmospheric nitrogen concentrations from 

the 1995-1998 period to 2010. 

This relationship was used to provide the primary estimate of deposition, along with 

the most site-specific data available for precipitation chemistry from the TBADS site, 

and the dry:wet deposition ratio as derived from the TBADS site. These data were 

also used in the estimation of the 1995-1998 atmospheric deposition loadings to the 

bay (Pribble et al., 2001). The updated 2010 estimate based on this method is 

provided in the tabular presentation of predicted loadings later in this document. 

The actual effects of the planned emission reductions with respect to changes in 

deposition are unknown, however. To provide some boundaries to the predicted 

2010 deposition, two additional methods were used to provide alternative 

estimates. The first method uses a previously derived relationship between 

emission reductions and reductions in deposition that estimated a 1 ton reduction in 

deposition in response to a reduction in emissions of 400 tons (TBEP, 1999). The 

second method assumed no changes in atmospheric nitrogen concentrations from 

1998 levels. A comparison of the results of these methods are shown in the results 

section below. 

 

2-3
3. DOMESTIC AND INDUSTRIAL POINT SOURCES 

3.1 Current Conditions Point Source Loading Estimates 

Existing domestic and industrial point sources were identified in Pribble et al. 

(2001), and included direct surface discharges and land application discharges 

within the watershed with a permitted average daily flow (ADF) of 0.1 million 

gallons per day (MGD) or greater. Through interviews with local government utility 

planners and facility operators, projected flows and planned future facilities were 

identified for this analysis. 

3.1.1 Data Sources 

Point sources were identified by reviewing FDEP point source discharge locations in 

relation to the Tampa Bay watershed. The locations of all point sources in Florida 

were obtained from the PCS database provided by FDEP. These locations were 

used to create a GIS coverage, and then mapped for FDEP Tampa office staff review. 

The domestic point sources in the Tampa Bay watershed with ADF of 0.1 MGD or 

greater were identified by FDEP Tampa office staff. 

Sources used to estimate point source discharges and concentrations data to Tampa 

Bay for the current period, based on 1998 data, were as follows: 

• MORs and DMRs obtained from the EPCHC and the Tampa office of 

the FDEP; and 

• MOR and DMR data obtained directly from the domestic wastewater 

treatment facilities for those data not obtained from the EPCHC and 

FDEP. 

The database was subjected to quality control measures to ensure that the most 

accurate flows and concentrations obtainable were used in the loading estimates. 

The entries were scanned for incongruous data points. Obvious outliers (such as 

flows of two or three orders of magnitude higher than the design capacity of the 

facility) were removed from the record. Complete records existed for most domestic 

wastewater treatment plants, with facilities reporting flow rate and TN 

concentrations on a monthly basis. Attempts were made to locate sources of valid 

data to replace missing or invalid values, often by contacting facility personnel 

directly. 

For those data gaps that could not be filled with actual recorded data, two methods 

were used to complete the record, depending upon the amount of data missing, as 

follows. 

3-1
• If 1-3 months’ of data were missing consecutively, discharge and/or 

pollutant concentrations were set to those of the last month’s for 

which values existed. 

• If more than 3 months’ of data were missing consecutively, discharge 

and/or pollutant concentrations were set to the monthly averages of 

the 1995-1998 record. 

In some cases, a form of nutrient other than total nitrogen was reported. For 

example, if both total nitrogen and nitrate nitrogen were recorded for some months 

at a facility, but only nitrate nitrogen was recorded for most months, the average 

ratio of nitrate to total nitrogen was calculated for those months with both values. 

The resulting ratio was applied to the other months, resulting in an estimate of total 

nitrogen for those months. If only nitrate nitrogen data existed, then total nitrogen 

concentration was set to the reported concentration of nitrate nitrogen. 

If no data for a certain parameter were available for a facility and it was known or 

suspected that loadings of that chemical did occur, then other similar facilities were 

examined. Typical or averaged data from these facilities were used to fill data gaps 

if no other source of information was available. This method was chosen as an 

alternative to showing missing data for loads from major point sources. 

3.1.2 Methods 

Current condition point source loading estimates were developed as monthly loads 

for 1998. All facilities were assumed to discharge independently except the St. 

Petersburg facilities. Effluent from St. Petersburg’s four facilities enters a common 

distribution system, and commingles prior to discharge as land application reuse. 

Direct surface water discharges were calculated by multiplying the flow (expressed 

as volume per unit time, such as MGD, by the reported TN concentration (mg/L). 

With appropriate conversion factors, this calculation yields a mass per unit time, 

such as tons per year. All of the effluent released via surface discharge was assumed 

to reach the Tampa Bay system. 

Land application of treated effluent is discharged most commonly by either spray 

irrigation or in percolation ponds. The applied effluent either evaporates, is taken 

up by vegetation, becomes surface runoff (generally a very small component of the 

total volume), or infiltrates to the water table. Therefore, pollutant loadings that 

reach the bay generally do so via groundwater. Land application loadings were 

estimated using recorded effluent quality data from specific facilities, with 

attenuation rates (Zarbock et al., 1996b) applied to flows and nitrogen loads once 

the effluent enters the environment. 

3-2
These attenuation rates are the same as those used previously for loading 

estimations for the 1985-1994 period (Zarbock et al., 1994; 1996b), and account for 

attenuation of pollutants in the environment prior to the effluent flow reaching the 

receiving water of Tampa Bay. Pollutant loading reductions applied to loads 

discharged to land were as follows: 

TN (spray irrigation) : 95% reduction for City of St. Petersburg 

facilities, 

: 90% reduction for all other facilities, and 

TN (percolation pond) : 70% reduction. 

These rates were the same as those used previously (Zarbock et al., 1994; 1996a; 

1996b). 

TN load reductions were based on literature values for nutrient behavior in the 

subsurface environment and local WWTP monitor well data. General assumptions 

used to estimate land application loads include: 

 • Recorded monthly values for domestic effluent for facilities with land 

application were used as the "influent" value. 

 • Initial concentration reductions result from above-ground and root 

zone processes, followed by downward migration through the 

unsaturated zone, to the water table. 

 • Some additional removal of TN may occur during waste stream 

movement towards the receiving water (surface water), through the 

surficial aquifer. However, this additional removal is thought to be 

relatively small, so there was no accounting for varying distances of 

effluent travel among individual sources. 

• Removal rates for nitrogen in effluent are higher for spray irrigation 

than for percolation ponds because of enhanced volatilization and 

plant uptake that occurs with spray facilities. The City of St. 

Petersburg plants operate to maximize the ammonia proportion of 

nitrogen in the effluent. This enhances plant uptake and volatilization 

of nitrogen, and supports the estimated 95% removal rate calculated 

using monitor well data (St. Petersburg, 1993). 

 

3.2 2010 Conditions Point Source Loading Estimates 

Future condition point source loads were obtained by revising existing conditions 

loads base on projected changes in demand, treatment methods, or effluent disposal 

method. Data sources and methods are described below. 

3-3
3.2.1 Data Sources 

Information on the quality and quantity of future discharges from domestic and 

industrial point sources was obtained via telephone interviews and visits with 

representatives of each of the governmental entities responsible for the specific 

sources. A complete list of the persons contacted and a summary of the interviews 

is presented in Appendix 1. For each interview, the contacted party was supplied 

with the information provided during the development of the previous future 

condition estimates, and asked if there were any significant changes in these plans. 

Through these interviews, it was determined which facilities are proposed to remain 

in service or close, what changes in treatment levels or discharge methods are 

expected, and to what extent flows may be expected to rise or fall during the next 

decade. 

Any new information provided for future condition point source estimates was used 

to develop updated 2010 loading estimates. For those facilities for which no 

revisions of 2010 loadings were necessary, the estimated future loadings remained 

the same as for the previous estimate. For those facilities that came online 

following the 1992-1994 period, the 1998 estimated loadings were used as a 

baseline. 

3.2.2 Methods 

The methods used to estimate projected future loads were the same as those used to 

estimate point source loads for the current period, using revised flows or 

concentrations based on the interviews. Monthly flows were multiplied by the TN 

concentrations to yield monthly loads, using the following assumptions: 

• all loads from surface discharges reach the bay; 

• 90% of the TN load from spray irrigation land application did not 

reach the bay, but was attenuated through process following 

application (except for St. Petersburg facilities, which had 95% TN 

attenuation because of the high level of volatile ammonia in the 

effluent); and 

• 70% of the TN loads from percolation pond land application did not 

reach the bay, but were attenuated through processes following 

application. 

3-4
4. SPRINGS AND GROUNDWATER 

4.1 Current Conditions Springs and Groundwater Loading Estimates

Springs are a significant source of nitrogen loading to the bay. Estimates of spring 

loads were developed using existing measured data, and were developed 

independently of groundwater loads. Groundwater provides another source of 

nutrient loading to the bay. The surficial (water table), intermediate, and Floridan 

aquifers all contribute loadings to the bay. 

4.1.1 Data Sources 

Recorded flows and water quality data were used to estimate freshwater inflow rates 

and pollutant loadings from springs for the current condition. Previous loading 

estimates have been developed for Sulphur Springs, Lithia Springs, and Crystal 

Springs, which were identified as significant discharges in the Tampa Bay watershed 

(Zarbock et al., 1994; 1996b). Smaller springs do exist in the watershed, but have 

relatively small discharges and were not considered in this loading analysis or the 

previous estimates. Lithia Springs and Sulphur Springs are not in gaged portions of 

the Tampa Bay watershed, but are themselves gaged. Crystal Springs is located in a 

gaged basin within the Hillsborough River watershed and its flow was accounted for 

by the downstream gage, so that pollutant loadings from Crystal Springs are 

incorporated into the nonpoint source loading estimate, as done previously 

(Zarbock et al., 1994; 1996b). 

Estimates of wet and dry season groundwater inflow to Tampa Bay were completed 

using the methods of Hutchinson (1983) and Brooks et al. (1993). Flow estimates 

were calculated using a flow net analysis and Darcy's equation (Freeze and Cherry, 

1979), a well-recognized analytical method for estimating groundwater flow. TN 

concentration data for the surficial, intermediate, and Floridan aquifers were 

obtained from the SWFWMD Ambient Ground Water Monitoring Program 

(AGWMP) (DeHaven, personal communications). Only groundwater inflow that 

entered the bay directly from the shoreline or bay bottom was considered. 

Groundwater inflow to streams was accounted for in the nonpoint source empirical 

model. Septic tank loadings to the bay in groundwater were not explicitly 

accounted for in this analysis. Current condition groundwater loadings were set 

equal to those of 1998, as previously derived (Pribble et al., 2001). 

4.1.2 Methods 

The methods used to calculate current pollutant loadings from springs and 

groundwater follow those used in previous loading estimates (Zarbock et al., 1996b; 

Pribble et al., 2001). For both sources, average monthly TN concentrations for 

4-1
1998 were multiplied by monthly flows to yield monthly TN loadings. Springs and 

groundwater loading estimates for the current period were set to those of 1998 

(Pribble et al., 2001). 

 

4.2 2010 Conditions Springs and Groundwater Loading Estimates 

 

Loadings from springs and groundwater for future conditions were also estimated. 

Loadings from Lithia Springs and Sulphur Springs were estimated, as were the 

combined loadings from the surficial, intermediate, and Floridan aquifers. 

4.2.1 Data Sources and Methods 

Future condition spring loadings were estimated using 1998 data from the USGS 

and SWFWMD, as described for current conditions. No defensible means of 

quantifying trends in spring flows or spring nutrient concentrations is available. 

Therefore, the 1998 data were used to estimate future conditions spring loadings. 

Similarly, groundwater loading estimates for 1998 were assumed to be 

representative of future conditions. 

 

4-2
5. MATERIAL LOSSES 

5.1 Current Conditions Material Losses Loading Estimates 

Fertilizer losses from loading docks at port facilities constitute a source of nutrient 

loading classified as material losses. In particular, bulk phosphate fertilizer is 

subject to product losses during its transfer from land carrier to storage facility, and 

onto vessels for shipping. Product is lost both through spilled product washing into 

the bay with stormwater runoff, and via fugitive dust. Material losses occur at 

facilities at the Port of Tampa, in the Coastal Hillsborough Bay basin, and at Port 

Manatee, in the Coastal Lower Tampa Bay basin. 

5.1.1 Data Sources 

Estimates of current total nitrogen loadings due to material losses were developed 

from data provided by the facilities for 1998. For the 1995-1998 estimates, all 

facilities provided spreadsheets containing loss estimates due to handling losses and 

airborne (fugitive) losses on an annual basis for the 1995-1998 period. These 

estimates were requested and obtained through the assistance of Mr. Craig Kovach, 

CF Industries, and provided to the TBEP in electronic format. 

5.1.2 Methods 

The loss estimates for the 1995-1998 period were much less than those from the 

1992-1994 period (Zarbock et al., 1996). For the 1992-1994 estimates, facility 

personnel provided rock and chemical masses shipped. The shipped products were 

then converted to losses using conversion factors based on methods developed by 

Morrison and Eckenrod (1994). These methods suggested an overall loss rate of 

approximately 0.02% of product shipped, so that the total masses of nitrogen and 

phosphorus in the shipped product were multiplied by 0.0002 to derive the 

pollutant loadings from the phosphate handling facilities. The estimates for the 

1995-1998 period, however, represent the best estimates by facility personnel of 

actual losses. These estimates reflect both actual reductions in nutrient losses from 

improved handling practices implemented by most facilities, and improved loss 

estimation techniques for both ship loading losses and air borne losses. 

5.2 2010 Conditions Material Losses Loading Estimates

5.2.1 Data Sources and Methods 

Material losses for future conditions were estimated by changing existing condition 

loadings by 1% per year from 1998 through 2010. This information was obtained 

5-1
from Mr. Craig Kovach, CF Industries, and Mr. Bruce DeGrove, Florida Phosphate 

Council, as representative of industry growth through 2010. 

 

5-2
6. NONPOINT SOURCES 

6.1 Current Conditions Nonpoint Sources Loading Estimates 

Nonpoint sources include stormwater runoff and baseflow as streamflow. All 

nonpoint source loading estimates for existing conditions were model-based, and 

used no measured water quality or flow data. This approach was used so that an 

equitable comparison of existing condition to future condition loads (all modelbased) could be made. 

6.1.1 Data Sources 

Data used to estimate nonpoint source loads include rainfall, land use, soils, 

subbasin boundaries, and land use-specific runoff coefficients and stormwater 

quality concentrations. These data were all used to develop modeled estimates of 

TN loads to Tampa Bay. 

Drainage Basin Boundaries

Drainage basin boundaries were incorporated into all geographically-based data 

used for this project (e.g., land use data, precipitation data, drainage areas, point 

source locations). The drainage area boundaries were based on a geographic 

information system (GIS) coverage obtained from the Southwest Florida Water 

Management District ( SWFWMD, 1992). 

The Tampa Bay watershed includes a total of 425 subbasins covering approximately 

2,276 sq. mi. (5,895 sq. km.), as delineated by USGS (Foose, 1993). Internally 

drained lands, which include 22 subbasins, encompass 125 sq. mi., or slightly more 

than 5% of the watershed area. These areas may be expected to retain initial 

rainfall volumes, and provide surface discharge only after internal storage areas are 

filled. For nonpoint source load modeling, these noncontributing subbasins were 

removed from the land area that generated stormwater runoff. 

Rainfall Records

The precipitation data used for modeling surface water hydrology were obtained 

from the NWS for the 1992-1994 period. Total monthly precipitation records for 22 

long-term stations within or near the Tampa Bay watershed were obtained for the 

period January 1992 through December 1994. The names and locations of these 

stations are presented in Zarbock et al. (1994). Total monthly precipitation values 

were estimated for each subbasin, month, and year of the existing period. Subbasin 

estimates were interpolated from a precipitation response surface that was fit to the 

entire watershed for each month and year of the existing period. The response 

6-1
surface was fit to account for regional patterns, but to give more emphasis to local 

conditions. 

Land Use/Land Cover Data

Land use/land cover GIS data for 1995 were obtained from the SWFWMD and 

incorporated into the surface water hydrology model. These data represent an 

update of the land use data from that used for the previous estimate (Zarbock et al., 

1996a), which were for 1990. The land use data were recorded following the 

Florida Land Use Cover Classification System (FLUCCS) level 3 developed by the 

Florida Department of Transportation Thematic Mapping Section (FDOT, 1985). 

For the purpose of assigning land use-specific runoff and pollutant loading factors, 

the FLUCCS land uses were aggregated into 21 classes, as presented in Appendix 2. 

The aggregated land use classification system was developed by examining the 

source literature for the FLUCCS land uses, and combining hydrologically-similar 

land uses based on stormwater runoff coefficients and land use specific pollutant 

loading factors. Land use-specific stormwater runoff coefficients and pollutant 

concentrations were determined from a review of field investigations from central 

and south Florida, as described below. 

Soils Data

The soils coverage includes discrete polygons of individual soil series (types) as 

identified and delineated by the USDA Natural Resources Conservation Service 

(NRCS) in the Hillsborough, Pinellas, Manatee, Polk, and Pasco county soil surveys. 

The GIS coverage of these data was obtained from the SWFWMD. The discrete 

soils polygons represented a soil series, and were aggregated by hydrologic soil 

groups (A - D). The NRCS has assigned a hydrologic group identification to each 

soil series to indicate runoff generating characteristics. "A" soils, in general, 

generate the least, and "D" soils the most amount of runoff for a given rainfall. The 

soils coverage was intersected with the land use coverage to provide the GIS layer 

used to estimate runoff coefficients. Each unique combination of land use type, soil 

series, and season has been assigned an associated runoff coefficient value. 

Land Use-Specific Runoff Coefficients and Stormwater Quality Concentrations

Land use-specific runoff coefficients were obtained from published literature, 

including references for the west-central and south Florida geographic area. A range 

of runoff coefficient values for each land use was developed to account for seasonal 

changes in rainfall/runoff relationships, and for local soils conditions, as described 

in Zarbock et al. (1994) and used for the previously modeled current and future 

conditions (Zarbock et al., 1996a). These coefficients are presented in Appendix 3. 

6-2
An extensive list of regional water quality concentration data for nonpoint source 

total nitrogen was compiled for this modeling effort, and is summarized in 

Appendix 4 and further described in Zarbock et al. (1994) and Pribble et al. (2001). 

The values are from a number of stormwater sampling programs and represent 

averaged values from multiple samples from each program. 

Because base flow is a component of water sampled in channels during periods of 

runoff, base flow characteristics were assumed to be represented in these storm 

samples. Therefore, base flows were not estimated separately. 

6.1.2 Methods 

All nonpoint source loads for existing conditions were estimated using a modelbased approach, so that an equitable comparison to modeled future loads could be 

made. An empirical hydrologic model was developed to provide estimates of 

nonpoint source surface water inflows (Zarbock et al., 1996a). Model construction 

and methods for estimating nonpoint source loads are summarized below. 

Empirical data analyses indicated that the preferred model for predicting runoff in 

the Tampa Bay watershed was based on a log-linear relationship with rainfall and 

land use categories as independent variables. Rainfall for two previous months was 

included in the model in addition to rainfall for the present month. The land use 

composition of each basin was included through an adjustment factor (a). The 

model used was: 

FLOW = exp[ a + ( b0 *RAIN0 + b1 *RAIN1 + b2 *RAIN2 )] (Equation 1) 

 and, 

 

a = (c1 *L1) + (c2 *L2) + (c3 *L3) + (c4 *L4) 

where 

FLOW = nonpoint source flow (meters per month) for a given basin, 

year, and month, 

 

 RAIN0 = rainfall (meters per month) in the month, 

RAIN1 = rainfall (meters per month) in the month before the present 

month, 

RAIN2 = rainfall (meters per month) two months before the present 

month, 

6-3
L1 = the fraction of the basin in the URBAN land use category, 

 L 2 = the fraction of the basin in the AGRICULTURAL land use 

 category,

L3 = the fraction of the basin in the WETLANDS land use category, 

 L 4 = the fraction of the basin in the FORESTS land use category, and 

 

 c1, c2, c3, c4, b0, b1, and b2 are parameters to be estimated. 

The parameters associated with rainfall (b0, b1, and b2) act as weighting factors when 

averaging rainfall over three months. Their absolute magnitude also affects the 

slope of the relationship between rainfall and runoff. The parameters associated 

with land use categories (c1, c2, c3, and c4) define an aggregate adjustment factor (a) 

that affects both the slope and the intercept of the relationship between rainfall and 

runoff. 

The units of flow and rainfall listed above, meters per month (m/mo), were chosen 

for computational purposes. For flow, m/mo represents the total flow from a land 

area over the time period (month), expressed as a volume of water with an area 

equal to the land area, and the depth in meters. Although the unit is listed as depth, 

the volume is implicitly accounted for in the land area. For rainfall, m/mo 

represents the depth of rainfall over the land area during the time period (month). 

A least squares regression with no intercept was used to estimate the seven 

parameters in Equation (1) after taking the natural logarithm of both sides of the 

equation: 

 

 log(FLOW) = (c1*L1) + (c2*L2) + (c3*L3) + (c4*L4) + 

 ( b0 *RAIN0 + b1 *RAIN1 + b2 *RAIN2) (Equation 2) 

Model development resulted in the definition of four separate rainfall/runoff 

relationships, varying with season and basin land use characteristics. "More urban" 

basins were defined as having greater than 19% urban land use, and "less urban" 

basins had less than 19% urban land use. The selection of the 19% level was based 

on an investigation of the distribution of urban land cover and the goodness of fit of 

the rainfall/runoff relationships. Months were classified into two categories based 

on rainfall: dry season (November through June) or wet season (July through 

October). The model was run for each combination of these categories, resulting in 

four complete sets of parameter estimates for the following conditions: 

6-4
 19% urban, dry season 

 19% urban, wet season 

 > 19% urban, dry season 

 > 19% urban, wet season 

Total monthly flow for each subbasin was estimated using Equation (1) with the 

appropriate parameter estimates. The next step of estimating pollutant loads was to 

estimate the fraction of the total subbasin flow that originated from each land use. 

The total subbasin flow was apportioned among the constituent land use categories 

within each subbasin as follows: 

∑ =

i

i i

i i

i A R

FLOW A R FLOW

*

* * (Equation 3) 

where 

 

 FLOWi = the total nonpoint source flow (m/mo) from land use category 

i, 

FLOW = the total nonpoint source flow (m/mo) from a subbasin, 

 

 Ai = area (acres) in land use category i, and 

 

 Ri = the runoff coefficient (fraction of rainfall that runs off) for land 

use category i. 

The above calculation resulted in the disaggregation of the total nonpoint source 

flow for a subbasin into flows generated by individual land use types. 

Subbasin pollutant loads were then estimated by land use using land use/soilspecific runoff coefficients and land use-specific pollutant concentrations. Nonpoint 

source runoff generated by an individual land use type within a basin was 

calculated by prorating the total flow using land use-specific runoff coefficients and 

the area of that land use type within the basin (Equation 3). Nonpoint source 

pollutant loads for specific land uses were then estimated for the desired time 

period according to the following equation: 

 

Pollutant loading for land use i = FlowLUi * PCLui (Equation 4) 

 where: 

PCLUi =Average pollutant concentration for land use i and 

6-5
FlowLUi =Total flow from land use i.

The land use-specific pollutant loads were then summed to yield a total load for the 

subbasin. Subbasins within a larger area (jurisdictional area or bay segment major 

basin) were then summed as appropriate to obtain the loading estimates at their 

desired spatial scale. 

6.2 2010 Conditions Nonpoint Sources Loading Estimates 

All nonpoint source loads for projected future conditions were model-based. 

Projected future condition loads were estimated on a monthly basis for twelve 

calendar months and then summed to yield a representative annual load for the year 

2010. 

6.2.1 Data Sources 

Average monthly rainfall was calculated using the same NWS data that were used 

for the 1992-94 conditions load estimates. The monthly rainfall amounts were used 

to drive the empirical model. All future condition loading estimates were modelbased, and were calculated in the same manner as existing condition loadings. The 

future and existing loadings were calculated by changing only the land use, and by 

applying pollutant loading attenuation factors to the new urban land uses to account 

for surface water permit treatment requirements. 

A previous study by the TBNEP (Zarbock et al., 1996a) developed projections of 

2010 land use conditions to estimate future nonpoint source pollutant loadings. For 

that work, 1990 land use data obtained from SWFWMD was used as a base, and 

was changed to future conditions (2010) after consultation with local planning 

agencies. The methods used to estimate future land use coverage within the 

watershed (by basin) were based on 1990 land use coverage, population projections 

for 2010 developed by the U.S. Census Bureau, and population and employment 

information obtained from local planning agencies. 

Changes in projected 2010 land uses may be the result of changes between the 

District’s 1990 GIS land use coverage and the newer “current conditions” (1995) 

land use coverage. Changes also may result from revised population and housing 

projections developed by local planning agencies or from changes in mapping 

boundaries. 

Local government planners were interviewed, and provided with the estimates of 

2010 land use previously derived (Zarbock et al., 1996a) and with the 1995 land 

use. In addition to the interviews, local planning department documents, maps, and 

population projections were evaluated. Individuals from Hillsborough, Pinellas, 

6-6
Manatee, Pasco, and Polk counties were interviewed to obtain local expertise with 

respect to projected spatial and temporal growth trends for incorporated and 

unincorporated jurisdictions within the watershed. Some local governments used 

U.S. Census Bureau information or trends in land use changes to project where 

future growth would occur. Other jurisdictions used transportation-based analyses 

for their land use trend analysis. Information sources, individuals interviewed from 

each local government, and assumptions used to make the land use projections are 

discussed below. 

Pinellas County and Incorporated Jurisdictions

Population and employment projections for Pinellas County, Clearwater, St. 

Petersburg, and other incorporated jurisdictions within the county were obtained 

from the Pinellas County Planning Department (1998). Revised projections had 

been developed by the department in 1998, and were enumerated by the 12 

Planning Sectors in the county (Beardslee, pers. comm.). 

The 1995 GIS land use coverage had some significant differences compared to the 

1990 coverage. Medium density residential in St. Petersburg (Middle Tampa Bay 

and Boca Ciega Bay basins) declined 60%, according to the GIS coverage. This is 

likely either an artifact of the methods used to develop the two coverages or a result 

of reclassification of existing residential areas within the city, and may not reflect 

actual changes in land cover. However, this did result in changes to the future land 

use estimates. 

Projected changes in population within each Planning Sector between 1995 and 

2010 were determined. For drainage basins that encompassed more than one 

Planning Sector, a composite population change for the basin was estimated by 

weighting the contributions of each Planning Sector, based on area. Assumptions 

used for the Pinellas County projections include: 

• Because 1997 population was the earliest reported by the county and 

the land use base used for update was based on 1995 aerial 

photography, the projected 1997-2010 population changes were 

increased by 8% to account for the two year difference in time period. 

• Within each planning unit, all residential and commercial land uses 

were assumed to change at a rate sufficient to accommodate projected 

population changes. 

• Industrial and institutional land uses were assumed to change on a 

site-specific basis. 

• Agricultural, forested, and open lands were assumed to decrease 

corresponding to the urban land increase. 

6-7
• Open water and wetlands were assumed to not change. 

Hillsborough County and Incorporated Jurisdictions

Revised population, housing, and employment projections for Hillsborough County, 

Tampa, and other incorporated jurisdictions within the county (Plant City, Temple 

Terrace) were obtained from the Hillsborough County City County Planning 

Commission (1999a, 1999b). Projections had been developed by the agency using 

U.S. Census Bureau data, land use change trends, occupancy change rates, and 

other sources (Cullen, pers. comm.). Data for 1995 and 2010 were obtained by 

census tract and Planning Area. 

The population estimates for the north-central portion of the County and “New 

Tampa” were revised upwards from the earlier estimates. Higher growth rates in the 

Cypress Creek and upper Hillsborough River Basins resulted in revisions to the 

future land use estimates. 

Projected changes in population within each Planning Area between 1995 and 

2010 were determined. For drainage basins that encompassed more than one 

Planning Area, a composite population change for the basin was estimated by 

weighting the contributions of each Planning Area, based on area. Assumptions 

used for the Hillsborough County projections include: 

• Within each planning unit, all residential and commercial land uses 

were assumed to change at a rate sufficient to accommodate projected 

population changes. 

• Industrial and institutional land uses were assumed to change on a 

site-specific basis. 

• Agricultural, forested, and open lands were assumed to decrease 

corresponding to the urban land increase. 

• Open water and wetlands were assumed to not change. 

Manatee County and Bradenton

Revised population and employment projections for Manatee County and 

Bradenton were obtained from the Manatee County Planning Department (1999). 

Projections had been developed by the department using U.S. Census Bureau data, 

land use change trends, occupancy change rates, and other sources (Kotecki, pers. 

comm.). Population estimates and projections for 1995 and 2010 were obtained by 

Planning Sub-Areas. 

It should be noted that the latest population and building projections are 

substantially higher than the projections used for the original future land use 

6-8
estimates (Kotecki, pers. comm.). Residential land use estimates for 2010 rose 28% 

using the new revised population projections. Also, there were significant 

differences in the baseline land use coverage for Manatee River basin. The 1995 

land use coverage showed a 34% increase in medium density residential land uses 

over the 1990 coverage, which likely are the result of both actual land use changes, 

and differences in photo-interpretation. Both these factors contributed to the revised 

estimates of urban land use in the Manatee River basin increasing substantially. 

Projected changes in population within each Sub-Area between 1995 and 2010 

were determined. For drainage basins that encompassed more than one Sub-Area, a 

composite population change for the basin was estimated by weighting the 

contributions of each Sub-Area, based on land area. Assumptions used for the 

Manatee County projections include: 

• Within each planning unit, all residential and commercial land uses 

were assumed to change at a rate sufficient to accommodate projected 

population changes. 

• Industrial and institutional land uses were assumed to change on a 

site-specific basis. 

• Agricultural, forested, and open lands were assumed to decrease 

corresponding to the urban land increase. 

• Open water and wetlands were assumed to not change. 

Pasco County and Incorporated Areas

Population and industrial, commercial, and service employment projections for 

Pasco County and incorporated jurisdictions within the county were obtained from 

the County Planning Department (1999). Projections had been developed by the 

department using U. S. Census Bureau data, land use change trends, occupancy 

change rates, and other sources (Burbridge, pers. comm.). Data for 1995 and 2010 

projected populations were obtained by census tract and Planning Division. 

Projected changes in population within each Planning Division between 1995 and 

2020 were determined. All Planning Divisions fell within a single basin, so no 

weighting of land use change rates was required. Assumptions used for the Pasco 

County projections include: 

• Within each planning unit, all residential and commercial land uses 

were assumed to change at a rate sufficient to accommodate projected 

population changes. 

• Industrial and institutional land uses were assumed to change on a 

site-specific basis. 

6-9
• Agricultural, forested, and open lands were assumed to decrease 

corresponding to the urban land increase. 

• Open water and wetlands were assumed to not change. 

Polk County

No population projections other than at a county-wide scale were available from 

Polk County (Hommel, pers. comm.). Because of the lack of spatially- appropriate 

data, land use changes in the area of the Tampa Bay Watershed encompassed by 

Polk County were assumed to change at the same rate as lands in Pasco and 

Hillsborough counties within the same basin (upper Hillsborough River). 

The updated 2010 land use estimates are presented in Appendix 5. The most 

common land use type projected for the year 2010 is pasture, at 14% of the total 

watershed area. All types of agriculture combined encompass 29% of the total area. 

Residential land uses account for over 18% of the total area. All urban land uses 

combined (except mining at 7%) make up 26% of the total area. It should be noted 

that the watershed acreage includes Tampa Bay itself, and not only the watershed. 

The bay comprises 13% of the total area. 

A comparison of the 1990 and 1995 land use coverages, and of the original (1996) 

and revised (2000) 2010 land use projections, are included in Appendix 5. As 

stated above, changes between coverages of land use acreages in various categories 

account for some of the differences in the original and new 2010 land use 

projections. As can be seen, on a watershed–wide scale, the 1990 and 1995 

coverages do not differ greatly, generally under 10% for most major urban and 

agricultural land use types. One exception to this is row crops, which covers 58% 

more land in the 1995 coverage than in the 1990 coverage. Additionally, several 

wetland types are very different. Differences are more pronounced on a major 

basin or basin level. 

Reasons for the differences could include changes in methodologies for mapping 

and photo-interpretation, real land use changes, or changes in the boundary of the 

mapping. Boundary changes are most evident for open salt water and tidal flats, 

which were not included in the 1990 coverage but were in the 1995 coverage. 

A comparison of the original (1996) and revised (2000) 2010 land use projections 

reveals a fairly good agreement in most urban and agricultural categories. On a 

watershed scale, urban land uses differed by under 15%. Row crops differed by 

53%, but this can be accounted for by the differences in baseline coverages. 

The assumptions used in making the projections were the same in both cases, so 

differences in upland land uses are the result of changes in the baseline coverage, 

and in the updated population, employment, and building projections made by the 

6-10
local planning agencies. Differences in wetland and water land covers are thought 

to be attributable mainly to changes in mapping methodologies and photointerpretation, real land use changes, or changes in the boundary of the mapping. 

There are two areas of the watershed where future land use projections changed the 

most: in the north-central Hillsborough County/New Tampa/south-central Pasco 

County area, and in western and central Manatee County. Both these areas have 

experienced accelerated growth during the past five years, necessitating substantial 

revisions to population and land use projections. For example, the revised 

residential projections for 2010 in the Manatee River basin increased by 28% over 

the original projections, with corollary reductions in range and pasture land uses. 

These increases reflect current conditions and were verified by discussions with 

County planners. 

A comparison of the acreages of aggregated land use types in the watershed of each 

bay segment from the 1990 and 1995 land use coverages, and the previously 

developed and updated 2010 land use, is provided in Table 6-1. In the watershed 

of each bay segment, the updated 2010 land use shows more urban area than from 

the previous 2010 effort. Additionally, the updated 2010 land use shows greater 

areas of agricultural land use in the Hillsborough Bay, Middle Tampa Bay, Terra 

Ceia Bay, and Manatee River watersheds. Concomitantly, within the watersheds of 

almost all bay segments, pasture and rangeland and forested areas are less in the 

updated 2010 estimate than in that developed previously. 

6.2.2 Methods 

Future condition nonpoint source loads for the entire watershed were estimated 

using the same empirical hydrologic model that was used to estimate flows and 

loads for current. Model inputs included monthly rainfall, land use, soils, land usespecific runoff coefficients and water quality concentrations, and subbasin 

delineation. Monthly nonpoint source loads for 2010 were estimated using the 

same NWS data, those for 1992-1994, which were used for existing conditions. 

Therefore, for the future conditions loadings, only the land use was different from 

the existing conditions. The resultant twelve monthly loads were summed to yield a 

representative annual load for 2010. 

After the future land use-based loads were estimated, the future loads were 

subtracted from current (1992-94) loads. The difference between the existing and 

future loads represented new urban land. The loads associated with the new urban 

land were then attenuated to account for water quality treatments that will be 

required for new development through surface water permit requirements. 

Attenuation rates were 35% for TN loads, and were based on values of typical 

treatment efficiencies for stormwater best management practices (BMPs) obtained 

from a literature review (Coastal Environmental, 1995). 

6-11
Table 6-1. Comparison of land use proportions (% of segment watershed) for 1990, 

1995, previous 2010 estimate, and updated 2010 estimate, by bay segment. 

Old Tampa Bay 

Land Use Type Land Use Type 1990 1995 Previous 2010 Updated 2010 

Urban 51.8 52.2 54.1 56.4

Agricultural 1.9 2.0 1.7 1.7

Pasture & Rangeland 19.1 16.9 16.9 14.0

Mining 0.3 0.3 0.3 0.3

Forest & Barren 7.7 7.1 7.1 6.1

Freshwater & Wetlands 20.3 21.6 20.3 21.5

Hillsborough Bay 

Land Use Type Land Use Type 1990 1995 Previous 2010 Updated 2010 

Urban 21.2 22.5 24.2 26.8

Agricultural 5.4 6.6 1.7 6.2

Pasture & Rangeland 32.0 29.7 30.8 26.2

Mining 11.9 12.3 12.1 12.3

Forest & Barren 10.3 9.8 9.7 9.4 

Freshwater & Wetlands 19.3 19.1 17.6 19.1

Middle Tampa Bay 

Land Use Type Land Use Type 1990 1995 Previous 2010 Updated 2010 

Urban 17.7 18.3 19.2 20.1

Agricultural 15.0 20.5 14.7 19.4

Pasture & Rangeland 39.9 33.6 39.1 30.9

Mining 2.0 2.9 2.0 5.4

Forest & Barren 9.2 9.0 8.7 8.4

Freshwater & Wetlands 16.3 15.7 16.3 15.9

Lower Tampa Bay 

Land Use Type Land Use Type 1990 1995 Previous 2010 Updated 2010 

Urban 21.0 22.8 24.7 29.1

Agricultural 24.8 23.1 24.6 22.9

Pasture & Rangeland 27.0 27.0 23.6 21.1

Mining 2.4 2.4 2.4 2.6

Forest & Barren 3.8 4.2 3.6 3.5

Freshwater & Wetlands 21.1 20.5 21.0 20.7

6-12
Boca Ciega Bay 

Land Use Type Land Use Type 1990 1995 Previous 2010 Updated 2010 

Urban 84.2 84.3 83.8 87.4

Agricultural 0.2 0.3 1.3 0.2

Pasture & Rangeland 9.0 8.2 7.7 5.5

Mining 0.0 0.0 0.0 0.0

Forest & Barren 3.1 2.6 3.3 2.2

Freshwater & Wetlands 3.5 4.6 3.9 4.7

Terra Ceia Bay 

Land Use Type Land Use Type 1990 1995 Previous 2010 Updated 2010 

Urban 43.3 45.4 50.0 57.1

Agricultural 8.7 10.0 8.7 9.2

Pasture & Rangeland 29.9 27.7 24.0 17.7

Mining 0.0 0.0 0.0 0.0

Forest & Barren 7.0 7.8 6.3 7.1

Freshwater & Wetlands 11.1 9.0 11.1 9.0

Manatee River 

Land Use Type Land Use Type 1990 1995 Previous 2010 Updated 2010 

Urban 11.2 12.6 15.6 20.2

Agricultural 13.2 18.5 12.8 16.7

Pasture & Rangeland 43.7 40.8 40.3 35.6

Mining 1.2 1.3 1.2 1.4

Forest & Barren 15.7 11.7 15.0 11.0

Freshwater & Wetlands 15.1 15.1 15.1 15.1

6-13
7. RESULTS OF LOADING ANALYSIS 

Current and projected future TN loadings to Tampa Bay were estimated for bay segments 

by source and by local government jurisdiction, as discussed in the following section. 

These model-based loading estimates have been developed to assist the TBEP in setting 

living resource targets and in working with local governments to reexamine allocation of 

pollutant load reductions set previously. 

In the following discussion, bay segment loadings by source included major external 

sources of TN inputs (atmospheric deposition, nonpoint sources, domestic and industrial 

point sources, material losses of fertilizer product, groundwater, and springs). Loadings by

jurisdiction included only land-based, manageable loadings (nonpoint sources, point 

sources, and material losses). Because groundwater, springs, and atmospheric deposition 

loadings cannot be accurately apportioned among jurisdictions, they were not accounted 

for in the jurisdictional loading tables. 

7.1 Current Conditions 

Current Conditions Bay Segment Loadings by Source

For the current period, an annual load of approximately 3,666 tons of TN reached the bay. 

Current condition TN loading estimates are presented by source and bay segment in Table 

7-1. For comparison purposes, the previously estimated 1994 conditions loadings using 

the 1990 landuse (Zarbock et al., 1996a) are shown in Table 7-2. Note that rounding to 

whole number tons and percentages may cause summation discrepancies. From the 

updated estimate of current conditions, nonpoint sources had the highest contribution with 

1,427 tons/year (39% of the total external load). Atmospheric deposition had the second 

highest contribution with 1,142 tons/year (31%). Domestic and industrial point sources 

contributed approximately 436 (12%) and 382 tons/year (10%), respectively. Material 

losses of fertilizer products totaled 32 tons/year (1%). Groundwater and spring loadings 

totaled 247 tons/year (7%), with the great majority of that (approximately 245 tons/year) 

originating from springs. 

Of the seven major bay segments, Hillsborough Bay (HB) received the highest TN loadings 

from the watershed, approximately 1,369 tons/year (37% of the total bay-wide loading). 

The sources with the highest contributions to Hillsborough Bay included nonpoint source 

(487 tons/year, or 36%), domestic point sources (281 tons/year, or 21%), and groundwater 

and springs (246 tons/year, or 18%). Industrial point sources (202 tons/year, or 15%), 

material losses (32 tons/year, or 2%), and atmospheric deposition (121 tons/year, or 9%) 

made up the balance of the TN load to Hillsborough Bay. 

Middle Tampa Bay (MTB) received the next highest TN loading for existing conditions 

(approximately 695 tons/year). The largest contributors included atmospheric deposition 

(322 tons/year, or 47%), nonpoint source (290 tons/year, or 42%), and industrial point 

7-1
sources (60 tons/year, or 9%). No other source contributed more that 3% to this bay 

segment. Atmospheric deposition loading was the largest external TN source for this 

segment because of the large open water area of that segment with respect to the 

contributing watershed-based inputs. 

Old Tampa Bay (OTB) received the next highest TN loading for existing conditions (516 

tons/year). The highest source-specific load was atmospheric deposition (258 tons/year, or 

50%). Atmospheric deposition loading was a significant external source for Old Tampa 

Bay because of the relatively large open water area of that segment with respect to the size 

of the watershed. The second highest contributor was nonpoint source (167 tons/year, or 

32%). Domestic point source (87 tons/year, or 17%) was the only other significant TN 

source to Old Tampa Bay. 

The Manatee River (MR) segment received approximately 464 tons TN/year for the current 

period. Nonpoint source loads were most significant (379 tons/year, or 82% of the total). 

Industrial and domestic point source contributed 12 tons/year (3%) and 27 tons/year (6%), 

respectively. Atmospheric deposition contributed 47 tons/year (10%). These loadings 

reflect the Manatee River’s large tributary basin with respect to other inputs. 

Lower Tampa Bay (LTB) received 400 tons/year for the current period, with 277 tons/year 

(69%) of that total from atmospheric deposition. Again, the large surface area of water with 

respect to watershed area, and the lack of other significant sources, makes atmospheric 

deposition by far the most important external source for this bay segment. 

Boca Ciega Bay received a total TN load of 193 tons/year, with 99 tons/year (51%) 

originating from atmospheric deposition and 79 tons/year (41%) from nonpoint sources. 

Domestic point sources contributed approximately 14 tons/year (7%). 

Terra Ceia Bay had the smallest TN loading of the bay segments, with only 28 tons/year. 

Of that amount, approximately 19 tons/year (68%) originated as atmospheric deposition, 6 

tons/year (21%) was from nonpoint sources, and 4 tons/year (14%) resulted from domestic 

point sources. 

Differences between the updated current conditions loadings and those previously derived 

in Zarbock et al. (1996a) for 1994 total about 204 tons, with the updated loadings higher 

than those estimated previously. This difference results from both the increased point 

source and springs loading estimates for the updated current conditions loadings, and the 

large decline in material losses. The loads from these sources are representative of those of 

the most recent year for which data exist, 1998, as described in Pribble et al. (2001). This 

time period included the high rainfall period of the winter of 1997-1998 associated with 

the El Niño event. The elevated loadings for the updated current conditions are at least 

partially related to this event. 

7-2
Table 7-1. Updated current conditions annual TN loading by source and bay segment (all sources). 

BAY SEGMENT SOURCE OTB HB MTB LTB BCB TCB 

tons 258 121 322 277 99 19 

Atmospheric Deposition % 50 9 47 69 51 68 

tons 87 281 23 1 14 4 

Domestic Point Source % 17 21 3 <1 7 14 

tons 4 202 60 103 0 0 

Industrial Point Source % 1 15 9 26 0 0 

Material Losses tons 0 32 0 <1 0 0 

% 0 2 0 <1 0 0 

tons 167 487 290 19 79 6 

Nonpoint Source % 32 36 42 5 41 21 

tons <1 246 <1 <1 <1 <1 

Groundwater+Springs % <1 18 <1 <1 <1 <1 

tons 516 1369 695 400 193 28 

TOTAL % 14 37 19 11 5 1 

Table 7-2. Previous 1994 conditions annual TN loading by source and bay segment (all sources) (Zarbock 

BAY SEGMENT SOURCE OTB HB MTB LTB BCB TCB 

tons 227 115 306 288 93 20 

Atmospheric Deposition % 50 8 48 86 51 67 

tons 85 220 20 1 15 4 

Domestic Point Source % 19 16 3 <1 8 15 

tons 0 82 58 <1 0 0 

Industrial Point Source % 0 6 9 <1 0 0 

Material Losses tons 0 233 0 24 0 0 

% 0 17 0 7 0 0 

tons 145 534 254 20 74 5 

Nonpoint Source % 32 39 40 6 41 18 

tons <1 196 <1 <1 <1 <1 

Groundwater+Springs % <1 14 <1 <1 <1 <1 

tons 457 1381 638 334 182 30 

TOTAL % 13 40 18 10 5 1 
Current Conditions Bay Segment Loadings by Jurisdiction

The updated current conditions land-based TN loadings are presented by bay segment for 

each jurisdiction in Table 7-3. For comparison purposes, the previously estimated 1994 

conditions loadings using the 1990 landuse (Zarbock et al., 1996a) are shown in Table 7-4. 

Atmospheric deposition and groundwater+springs were not included because it is not 

feasible to apportion those loads to a jurisdiction. It should be noted that Pasco, Polk, and 

Sarasota counties are included in Tables 7-3 and 7-4. Although these jurisdictions have not 

been active in the TBEP allocation process, their contributions are shown for reference and 

for accounting purposes. Land-based loads combined for approximately 2,277 tons/year 

for the updated current conditions. 

For allocating all land-based, manageable loads to local governments, it was necessary to 

apportion all nonpoint source, point source, and material loss loadings to a jurisdiction. 

For example, although MacDill Air Force Base is owned by the Federal government, 

loadings from the base’s wastewater treatment plant were assigned to the City of Tampa. 

Local jurisdictions were also assigned industrial point source loadings for facilities 

discharging within the governmental boundaries. One exception is material loss loadings 

to Hillsborough Bay, which were assigned to Hillsborough County. This was done 

because of the active role that the county plays in regulating the phosphate industry and 

this source of nutrient loads. 

Of the participating jurisdictions (Pinellas, Hillsborough, and Manatee counties and the 

cities of Tampa, St. Petersburg, Clearwater, and Bradenton), Hillsborough County had the 

highest contribution at 804 tons/year (35% of the bay-wide total). Of this load, 436 

tons/year entered Hillsborough Bay, 275 tons/year entered Middle Tampa Bay, and 93 

tons/year entered Old Tampa Bay. 

Manatee County had the second highest contribution, with 543 tons/year (24% of the baywide total). Manatee County’s loads were dispersed to four bay segments, including 

Manatee River (366 tons/year), Lower Tampa Bay (123 tons/year), Middle Tampa Bay (44 

tons/year), and Terra Ceia Bay (10 tons/year). The City of Tampa generated approximately 

14% of the bay-wide load, contributing 303 tons/year to Hillsborough Bay and 25 

tons/year to Old Tampa Bay. The City of St. Petersburg contributed approximately 122 

tons/year (5%) of the total existing conditions TN load, distributed between Middle Tampa 

Bay (55 tons/year), Boca Ciega Bay (47 tons/year), and Old Tampa Bay (20 tons/year). 

Pinellas County contributed 119 tons/year (5% of the total TN load), distributed between 

Old Tampa Bay (73 tons/year) and Boca Ciega Bay (46 tons/year). The City of Clearwater 

contributed approximately 2% of the total TN load, all 44 tons/year going to Old Tampa 

Bay. The City of Bradenton contributed approximately 2% of the total TN load, with all 47 

tons/year going to the Manatee River. 

Differences between the updated current conditions loadings by jurisdiction and those 

previously derived in Zarbock et al. (1996a) for 1994 total about 114 tons, with the 

7-4
updated loadings higher than those estimated previously. This difference is largely due to 

the increased point source loading estimates for the updated existing conditions loadings. 

The loads from these sources are representative of those of the most recent year for which 

data exist, 1998, as described in Pribble et al. (2001). This time period included the high 

rainfall period of the winter of 1997-1998 associated with the El Niño event. The elevated 

loadings for the updated current conditions are at least partially related to this event. 

Table 7-3. Updated current conditions annual TN loading by bay segment and jurisdiction 

(land-based sources). 

BAY SEGMENT 

JURISDICTION OTB HB MTB LTB BCB TCB MR TOTAL

tons 93 436 275 0 0 0 0 804

Hillsborough County % 36 44 73 0 0 0 0 35

tons 73 0 0 <1 46 0 0 119

Pinellas County % 28 0 0 <1 49 0 0 5

tons 0 0 44 123 0 10 366 543

Manatee County % 0 0 12 100 0 100 87 24

tons 25 303 0 0 0 0 0 329

Tampa % 10 30 0 0 0 0 0 14

tons 20 0 55 0 47 0 0 122

St. Petersburg % 8 0 15 0 51 0 0 5

tons 44 0 0 0 0 0 0 44

Clearwater % 17 0 0 0 0 0 0 2

tons 0 0 0 0 0 0 47 47

Bradenton % 0 0 0 0 0 0 11 2

tons 0 231 0 0 0 0 0 231

Polk County % 0 23 0 0 0 0 0 10

tons 1 31 0 0 0 0 0 33

Pasco County % 1 3 0 0 0 0 0 1

tons 0 0 0 0 0 0 5 5

Sarasota County % 0 0 0 0 0 0 1 <1

tons 258 1002 374 123 93 10 418 2277

Total % 11 44 16 5 4 <1 18 100

7-5
Table 7-4. Previous existing conditions (1994) annual TN loading by bay segment and 

jurisdiction (land-based sources) (Zarbock et al., 1996a). 

BAY SEGMENT 

JURISDICTION OTB HB MTB LTB BCB TCB MR TOTAL

tons 85 540 238 0 0 0 0 862

Hillsborough County % 37 51 72 0 0 0 0 40

tons 63 0 0 0 40 0 0 103

Pinellas County % 27 0 0 0 45 0 0 5

tons 0 0 41 46 0 10 351 447

Manatee County % 0 0 12 100 0 100 91 21

tons 24 283 1 0 0 0 0 307

Tampa % 10 26 <1 0 0 0 0 14

tons 15 0 53 0 49 0 0 118

St. Petersburg % 7 0 16 0 55 0 0 5

tons 41 0 0 0 0 0 0 41

Clearwater % 18 0 0 0 0 0 0 2

tons 0 0 0 0 0 0 31 31

Bradenton % 0 0 0 0 0 0 8 1

tons 0 216 0 0 0 0 0 216

Polk County % 0 20 0 0 0 0 0 10

tons 2 31 0 0 0 0 0 33

Pasco County % 1 3 0 0 0 0 0 2

tons 0 0 0 0 0 0 5 5

Sarasota County % 0 0 0 0 0 0 1 <1

tons 230 1070 332 46 89 10 387 2163

Total % 11 50 15 2 4 <1 18 100

7-6
7.2 2010 Conditions 

Future Conditions Bay Segment Loadings by Source

For the period ca. 2010, an estimated average annual load of 3,132 tons/year of TN is 

projected to reach the bay. Projected future condition TN loadings are presented by source 

and bay segment in Table 7-5. For comparison purposes, the previously estimated future 

conditions loadings (Zarbock et al., 1996a) are shown in Table 7-6. From the updated 

future estimate, nonpoint sources were projected to have the highest contribution with 

approximately 1,432 tons/year (49%), and atmospheric deposition was projected to have 

the second highest contribution with 578 tons/year (20% of the total external load). 

Domestic and industrial point sources were estimated to contribute approximately 453 

(15%) and 204 tons/year (7%), respectively. Material losses of fertilizer products were 

estimated to total 36 tons/year (1%). Groundwater and springs loadings were estimated to 

total 247 tons/year (8%), with much of that (about 246 tons/year) originating from springs. 

Of the bay segments, Hillsborough Bay was expected to receive the highest future TN 

loading, estimated at 1,257 tons/year. The sources with the highest expected future 

contributions to Hillsborough Bay included nonpoint source (502 tons/year, or 40% of the 

total), domestic point sources (283 tons/year, or 23% of the total), and industrial point 

sources (130 tons/year, 10% of the total). Springs and groundwater were projected to 

contribute 246 tons/year (20%), atmospheric deposition 60 tons/year (5%), and material 

losses 36 tons/year (3%). 

Middle Tampa Bay was projected to have the second highest future condition TN loading 

(515 tons/year). Nonpoint sources were estimated to be the most significant TN loading 

source (265 tons/year, or 51% of the total). Atmospheric deposition was estimated to be 

another significant source, contributing 159 tons/year, or 31% of the total. Industrial and 

domestic point sources combined for 89 tons/year, or 17% of the total load. 

The Manatee River segment was projected to receive the next highest loading for future 

conditions, approximately 438 tons/year. Nonpoint source loads were expected to be most 

significant (366 tons/year, or 84% of the segment total). Industrial and domestic point 

sources were expected to contribute 11 tons/year (3%) and 31 tons/year (7%), respectively, 

and atmospheric deposition approximately 29 tons/year (7% of the total to that segment). 

Old Tampa Bay was expected to receive the next highest TN loading for future conditions 

(388 tons/year). The highest source-specific load was projected to be from nonpoint 

sources (183 tons/year, or 47%). Atmospheric deposition loads were estimated to be 117 

tons year (30% of the total). Atmospheric deposition will continue to be a significant 

external TN source for Old Tampa Bay because of the relatively large open water area of 

that segment, and because of the small contributions of other sources (small tributary 

drainage area and few point sources). Domestic point sources (84 tons/year, or 22%) and 

7-7
industrial point sources (4 tons/year, or 1%) were the only other significant TN sources to 

Old Tampa Bay. 

Lower Tampa Bay was expected to receive an average of approximately 176 tons/year for 

ca. 2010, with 153 tons/year (87%) of that total from atmospheric deposition. Again, the 

large surface area of water and the lack of other significant sources made atmospheric 

deposition by far the most important external source for this bay segment. Of the 

remainder, 21 tons/year (10%) is expected to be from nonpoint sources, with 2 tons/year 

(1%) from domestic point sources. Less than 1 ton/year is expected from the material 

losses at Port Manatee. 

Boca Ciega Bay was projected to receive a total TN load of 150 tons/year, with 88 

tons/year (59%) from nonpoint sources and 48 tons/year (32%) originating from 

atmospheric deposition. Domestic point sources were expected to contribute about 14 

tons/year (9%). Terra Ceia Bay had the smallest projected future TN loading of the bay 

segments, with almost 26 tons/year. Of that amount, approximately 11 tons/year (42%) 

was expected to originate as atmospheric deposition and 7 tons/year (27%) from nonpoint 

sources. 

The updated future loading estimate is approximately 720 tons less than those from the 

previous estimate. This difference is largely due to the decreases in atmospheric deposition 

loading predicted for the period. The decreased nitrogen emissions resulting from the 

TECO facilities are expected to decrease atmospheric nitrogen concentrations. As 

discussed previously, for the updated future loading estimate, a decrease in concentrations 

of 46% is assumed. This reduction leads to predicted atmospheric deposition loads of 

approximately half of those from the previous prediction. Further differences between the 

updated and previous future loading estimates result from the decrease in the predicted 

material losses loading. This decrease results from the improved handling operations and 

refined loss estimates compared to those used previously. The lower loss rate was applied 

after discussions with phosphate industry representatives (Pribble et al., 2001). 

As discussed previously, three methods of estimating 2010 atmospheric deposition were 

utilized to provide some bounds on expected changes in deposition due to emission 

reductions. The results of the method using a 46% reduction in atmospheric nitrogen 

concentration, proportional to the 46% reduction in emissions, are shown in Table 7-5 

below. The second method used estimated a 1-ton reduction in deposition for a 400-ton 

reduction in emissions. The third method assumed no changes in atmospheric nitrogen 

concentrations from 1998 levels. A comparison of the results of these methods are shown 

below: 

Method Deposition

Percentage reduction: 578 tons/yr 

400:1 ratio: 898 tons/yr 

No change in deposition: 1142 tons/yr 

7-8
Table 7-5. Updated future conditions annual TN loading by source and bay segment (all sources). 

BAY SEGMENT SOURCE OTB HB MTB LTB BCB TCB 

tons 117 60 159 153 48 11 

Atmospheric Deposition % 30 5 31 87 32 42 

tons 84 283 32 2 14 7 

Domestic Point Source % 22 23 6 1 9 27 

tons 4 130 58 0 0 0 

Industrial Point Source % 1 10 11 <1 0 0 

Material Losses tons 0 36 0 <1 0 0 

% 0 3 0 <1 0 0 

tons 183 502 265 21 88 8 

Nonpoint Source % 47 40 51 12 59 31 

tons <1 246 <1 <1 <1 <1 

Groundwater+Springs % <1 20 <1 <1 <1 <1 

tons 388 1257 515 176 150 26 

TOTAL % 13 43 17 6 5 1 

Table 7-6. Previous future conditions annual TN loading by source and bay segment (all sources) (Zarboc

BAY SEGMENT SOURCE OTB HB MTB LTB BCB TCB 

tons 249 126 336 317 102 23 

Atmospheric Deposition % 54 9 50 86 53 77 

tons 47 283 20 3 15 0 

Domestic Point Source % 10 19 3 1 7 0 

tons 0 77 58 <1 0 0 

Industrial Point Source % 0 5 9 <1 0 0 

Material Losses tons 0 247 0 26 0 0 

% 0 17 0 7 0 0 

tons 165 540 256 23 78 7 

Nonpoint Source % 36 37 38 6 40 23 

tons <1 196 <1 <1 <1 <1 

Groundwater+Springs % <1 13 <1 <1 <1 <1 

tons 463 1470 670 369 195 29 

TOTAL % 13 40 18 10 5 1 
Future Conditions Bay Segment Loadings by Jurisdiction

The updated future conditions TN land-based loadings by bay segment and jurisdiction are 

presented in Table 7-7. For comparison purposes, the previously estimated future 

conditions loadings using the 1990 landuse (Zarbock et al., 1996a) are shown in Table 7-8. 

As with existing conditions, atmospheric deposition and groundwater+springs are not 

included because it is not feasible to apportion those loads to a jurisdiction. It should be 

noted that Pasco, Polk, and Sarasota counties are included in Tables 7-7 and 7-8. Although 

these jurisdictions have not been active in the TBEP process, their contributions to Tampa 

Bay loadings are shown for reference and for accounting purposes. 

Of the participating jurisdictions (Pinellas, Hillsborough, and Manatee counties and the 

cities of Tampa, St. Petersburg, Clearwater, and Bradenton), Hillsborough County had the 

highest contribution, at 741 tons/year (35% of the total load to the bay). Of this load, 378 

tons/year were expected to go to Hillsborough Bay, 267 tons/year to Middle Tampa Bay, 

and 97 tons/year to Old Tampa Bay. The large proportion of projected future loadings 

from Hillsborough County resulted from a large contributing land area, and significant 

point source inflows. 

Manatee County had the second highest expected contribution, with 434 tons/year (20%). 

Manatee County’s loads were dispersed to four bay segments, including Manatee River 

(365 tons/year), Middle Tampa Bay (31 tons/year), Lower Tampa Bay (23 tons/year), and 

Terra Ceia Bay (15 tons/year). 

The City of Tampa was expected to generate approximately 16% (331 tons/year) of the 

total bay-wide load, with 303 tons/year going to Hillsborough Bay and 28 tons/year going 

to Old Tampa Bay. The City of St. Petersburg was expected to contribute 6% (128 

tons/year) of the future TN load, distributed between Middle Tampa Bay (57 tons/year), 

Boca Ciega Bay (51 tons/year), and Old Tampa Bay (21 tons/year). Pinellas County was 

expected to contribute 5% (110 tons/year) of the future TN load, distributed between Old 

Tampa Bay (59 tons/year), and Boca Ciega Bay (51 tons/year). 

The City of Bradenton was projected to contribute approximately 2% of the total future TN 

load, with all 39 tons/year going to the Manatee River. The City of Clearwater was 

projected to contribute approximately 3% of the total TN load, all 65 tons/year going to 

Old Tampa Bay. Polk, Pasco, and Sarasota counties combined for an additional 275 

tons/year, or approximately 12% of the total future bay loading.

Differences between the updated future conditions loadings by jurisdiction and those 

previously derived in Zarbock et al. (1996a) total about 135 tons, with the updated 

loadings higher than those estimated previously. This difference is largely due to the 

increased point source loading estimates for the updated future conditions loadings. As 

described in Pribble et al. (2001), six industrial sources were identified for inclusion in the 

updated future loading estimate that were not included in the previous estimate, including 

7-11
five in the Hillsborough Bay watershed and one in the Old Tampa Bay watershed. 

Additionally, revisions to planned increases in domestic point source loadings, resulting 

from the interviews described in Appendix 1, led to increased loadings. Both industrial 

and domestic point source contributions were higher in the updated future estimate than 

previously. 

Table 7-7. Updated future conditions annual TN loading by bay segment and jurisdiction 

(land-based sources). 

BAY SEGMENT 

JURISDICTION OTB HB MTB BCB TCB MR TOTAL

tons 97 378 267 0 0 0 0 741

Hillsborough County % 36 40 75 0 0 0 0 35

tons 59 0 0 <1 51 0 0 110

Pinellas County % 0 0 <1 50 0 0 5

tons 0 0 31 23 0 15 365 434

Manatee County % 0 9 100 0 100 89 20

tons 28 303 0 0 0 0 0 331

Tampa % 32 0 0 0 0 0 16

tons 21 0 57 0 51 0 0 128

St. Petersburg % 0 16 0 50 0 0 6

tons 65 0 0 0 0 0 0 65

Clearwater % 0 0 0 0 0 0 3

tons 0 0 0 0 0 0 39 39

Bradenton % 0 0 0 0 0 10 2

tons 0 219 0 0 0 0 0 219

Polk County % 23 0 0 0 0 0 10

tons 1 41 0 0 0 0 0 52

Pasco County % 4 0 0 0 0 0 2

tons 0 0 0

Sarasota County 

LTB

22

0

10

8

24

0

0

<1

0 0 0 4 4

% 0 0 0 0 0 0 1 <1

tons 271 951 355 23 102 15 409 2125

Total % 13 45 17 1 5 <1 19 100

7-12
Table 7-8. Previous future conditions annual TN loading by bay segment and jurisdiction 

(land-based sources) (Zarbock et al., 1996a). 

BAY SEGMENT 

JURISDICTION OTB HB MTB LTB BCB TCB MR TOTAL

tons 87 530 237 0 0 0 0 855

Hillsborough County % 41 40 71 0 0 0 0 38

tons 44 0 0 0 40 0 0 83

Pinellas County % 27 0 0 0 43 0 0 4

tons 0 0 40 53 0 7 372 472

Manatee County % 0 0 12 100 0 100 90 21

tons 24 365 1 0 0 0 0 390

Tampa % 11 32 <1 0 0 0 0 17

tons 16 0 56 0 53 0 0 125

St. Petersburg % 8 0 17 0 57 0 0 5

tons 40 0 0 0 0 0 0 40

Clearwater % 13 0 0 0 0 0 0 2

tons 0 0 0 0 0 0 36 36

Bradenton % 0 0 0 0 0 0 9 2

tons 0 222 0 0 0 0 0 222

Polk County % 0 19 0 0 0 0 0 10

tons 2 30 0 0 0 0 0 32

Pasco County % 1 3 0 0 0 0 0 1

tons 0 0 0 0 0 0 6 6

Sarasota County % 0 0 0 0 0 0 1 <1

tons 213 1148 334 53 92 7 414 2260

Total % 9 51 15 2 4 <1 18 100

7-13
8. CONCLUSIONS 

To attain its seagrass restoration goal, the TBNEP developed the Nitrogen Management 

Strategy. The Strategy seeks to prevent future impacts due to excessive nitrogen loadings to 

Tampa Bay. To provide quantifiable goals for the Strategy, a suite of models were 

developed relating total nitrogen loading to chlorophyll concentrations in the bay and 

chlorophyll concentrations to light attenuation. These models suggested that light 

availability necessary for obtaining seagrass restoration goals could be met by establishing 

a “hold the line” strategy for nitrogen loads. The Tampa Bay Nitrogen Management 

Consortium adopted this strategy in 1996. 

To implement this strategy, local government partners agreed to preclude increases in 

future nitrogen loadings to the bay. The ca. 2010 total nitrogen loading estimates 

presented in Zarbock et al. (1996a) were developed to quantify expected TN loading 

increases, and were used for the TBNEP Allocation Workshops. This report presents the 

results of an update of the ca. 2010 total nitrogen loadings for use in reviewing the 

previous allocations for load preclusion. 

The following provides the conclusions from this update. 

• The greatest difference in predicted future loadings from any source is for 

atmospheric deposition. As a result of planned decreases in nitrogen 

emissions from TECO facilities, the updated load is approximately half of the 

previously predicted load. A more conservative method of deposition 

reduction estimation (400:1 ratio) still results in a reduction of 25% from that 

predicted previously. 

• The updated future loading predictions from domestic and industrial point 

sources are higher than previously. Revised estimates for domestic facilities 

include recent modifications to planned future operations. Revised estimates 

for industrial facilities include six additional facilities that were not included 

in the previous estimate. 

• The updated future loading predictions from material losses are less than 

those predicted previously. This is largely the result of improved operations 

at several facilities, resulting in lower material losses, and improved loss 

estimation methods. 

• The updated future nonpoint source loadings did not change appreciably 

from the previous prediction, despite an update of the future land use 

showing a larger proportion of urban land use than previously predicted. 

This is likely due to the load attenuation from any new development 

incorporated into the estimate. 

8-1
9. LITERATURE CITED 

Beardslee, Gordon. 2000. Pinellas County Planning Department. Personal 

Communication. 

Burbridge, Katherine. 2000. Pasco County Development Services Branch. Personal 

Communication. 

Brooks, G.R., T.L. Dix, and L.J. Doyle. 1993. Groundwater/surface water interactions in 

Tampa Bay and implications for nutrient fluxes. Prepared for: Tampa Bay National Estuary 

Program. St. Petersburg, Florida. 44 p. 

Coastal Environmental, Inc. 1995. Guidebook to Stormwater Best Management Practices 

in the Tampa Bay and Central Florida Regions. Prepared for Tampa Bay National Estuary 

Program. St. Petersburg, Florida. 

Cullen, Terry. 2000. Hillsborough County City-County Planning Commission. Personal 

Communication. 

Environmental Science & Engineering, Inc. 1987. Florida Acid Deposition Study – Fiveyear data summary. Prepared for: Florida Electric Power Coordinating Group. Tampa, 

Florida. 

Florida Department of Environmental Protection (FDEP). 2000. Personal communication 

with R. Pribble, Janicki Environmental, from Tom Rogers, FDEP, 5 June 2000. 

Florida Department of Transportation Thematic Mapping Section (FDOT). 1985. Florida 

land use, cover and forms classification system. Second ed. Tallahassee, Florida. 81 p. 

Foose, D. 1993. U.S. Geological Survey WRD. Personal communication. Tallahassee, 

Florida. 

Freeze and Cherry. 1979. Groundwater. Prentice-Hall, Inc. Englewood Cliffs, NJ. 604 p. 

Hillsborough County City-County Planning Commission. 1999a. 1999 Population and 

Housing Estimates by Jurisdiction and Census Tract. Prepared for Hillsborough Country 

Board of County Commissioners. Tampa, FL. 

Hillsborough County City-County Planning Commission. 1999b. 2020 Population and 

Housing Projections by Jurisdiction and Census Tract. Prepared for Hillsborough Country 

Board of County Commissioners. Tampa, FL. 

Hommel, Christina. 2000. Polk County Planning Department. Personal Communication. 

9-1
Hutchinson, C.B. 1983. Assessment of the interconnection between Tampa Bay and the 

Floridan Aquifer, Florida. U.S. Geological Survey Water Resources Investigations Report 

82-54. Tallahassee, Florida. 61 p. 

Janicki, A. and D. Wade. 1996. Estimating critical external nitrogen loads for the Tampa 

Bay estuary: An empirically based approach to setting management targets. Prepared for: 

Tampa Bay National Estuary Program. Prepared by: Coastal Environmental, Inc. Tampa 

Bay National Estuary Program Technical Publication #06-96. 

Kotecki, Leon. 2000. Manatee County Planning Department. Personal Communication. 

Manatee County Planning Department. 1999. Resident Population Projections and 

Distribution, 1990-2025 Manatee County, Florida. . Prepared for Manatee Country Board 

of County Commissioners. Bradenton, FL. 

Morrison, G., and R. Eckenrod. 1994. Personal Communication. Estimated Fugitive 

Emissions to Tampa Bay, 1985 to 1991. Tampa, Florida. 

Pasco County Development Services Branch. 1999. Population and Employment 

Projections Pasco County, 1997-2020. Prepared for Pasco County Board of County 

Commissioners. New Port Richey, FL 

Pinellas County Planning Department. 1998. Population and Employment Projections 

Pinellas County, 1997-2030. Prepared for Pinellas County Board of County 

Commissioners. Clearwater, FL. 

Pribble, R., A. Janicki, S. Janicki, and M. Winowitch. 2001. Estimates of total nitrogen, 

total phosphorus, total suspended solids, and biochemical oxygen demand loadings to 

Tampa Bay, Florida: 1995-1998. Draft Report. Prepared for: Tampa Bay Estuary Program. 

Prepared by: Janicki Environmental, Inc. 

Southwest Florida Water Management District – Mapping and GIS Section 1992. 

Geographic Information System Data Distribution Procedures. Subbasin boundary ARC 

INFO coverage. Brooksville, Florida. 

St. Petersburg, City of. 1993. Reclaimed water and injection well monitoring data for 

1986 to 1992. Department of Sanitary Sewers. St. Petersburg, Florida. 

Tampa Bay Estuary Program (TBEP). 1999. Partnership for Progress, the Tampa Bay 

Nitrogen Management Consortium Action Plan 1995-1999. Tampa Bay Estuary Program, 

St. Petersburg, FL. 

9-2
Tampa Bay National Estuary Program (TBNEP). 1996. Charting the Course for Tampa Bay, 

the Comprehensive Conservation and Management Plan for Tampa Bay. Tampa Bay 

National Estuary Program in cooperation with the US Environmental Protection Agency, 

Region IV. St. Petersburg, FL. 

Tampa Electric Company (TECO). 2000. Presentation at the 28 January 2000 Tampa Bay 

Nitrogen Management Consortium meeting, St. Petersburg, FL. Presented by Greg Nelson, 

Manager, Environmental Planning Department, TECO. 

Zarbock, H., A. Janicki, D. Wade, D. Heimbuch, and H. Wilson. 1994. Estimates of Total 

Nitrogen, Total Phosphorus, and Total Suspended Solids Loadings to Tampa Bay, Florida. 

Technical Publication #04-94. Prepared by Coastal Environmental, Inc. Prepared for 

Tampa Bay National Estuary Program. St. Petersburg, FL. 

Zarbock, H., A. Janicki, D. Wade, S. Janicki, and R. Pribble. 1996a. Model-based 

estimates of total nitrogen loading to Tampa Bay. Prepared for: Tampa Bay National 

Estuary Program. Prepared by: Coastal Environmental, Inc. Tampa Bay National Estuary 

Program Technical Publication #05-96. 

Zarbock, H., A. Janicki, and S. Janicki. 1996. Estimates of Total Nitrogen, Total 

Phosphorus, and Total Suspended Solids Loadings to Tampa, Bay, Florida. Technical 

Appendix: 1992-94 Total Nitrogen Loads to Tampa Bay. Technical Publication #19-96. 

Prepared by Coastal Environmental, Inc. Prepared for Tampa Bay National Estuary 

Program. St. Petersburg, FL. 

9-3
APPENDIX 1 

INDIVIDUALS CONTACTED FOR FUTURE CONDITIONS POINT SOURCE 

INFORMATION AND SUMMARY OF INTERVIEWS 

1
Domestic Point Sources Projected Plans for 2010 

City of St. Petersburg Southwest 

City of St. Petersburg Albert Whitted 

City of St. Petersburg Northeast 

City of St. Petersburg Northwest 

In 2000 spoke to Mr. Bill Johnson of the City of St. Petersburg and he stated that the 

predictions from previous interview with Mr. Dave Schulmister (1995) are still the same. 

City of Largo 

Spoke to Brian Dean of the City of Largo Plant. Said that Plant capacity did increase to 18 

MGD (i1997). Reclaimed water (reuse) is hoped to be at 70% reuse by 2005 and 90% 

reuse by 2010. Do not foresee any changes in nutrient loading and have no plans to 

expand the plant. 

City of Clearwater Northeast 

City of Clearwater East 

Spoke to Mr. Joe Reckenwald in 2000. He stated that the NE plant 2010 predictions will 

remain the same from his previous interview in 1996. Says that East plant is currently at 

50% reclaimed and anticipates that number increasing to 75% by 2010. 

City of Lakeland 

Mr. Don Schulender, Planning Engineer for Wastewater Division of the City of Lakeland, 

was contacted in 2000. He stated that out of 10 MGD, 25%-33% will goto Reuse. There 

is a possiblity that the city is expanding their power plant and will take all of the effluent, 

so 100% reuse. Mr. Schulender still anticipates no modifications in effluent quality from 

the plant. 

Bradenton 

Mr. John W. Cumming, Director of Public Works, was contacted in August of 2000. Mr. 

Cumming related that the City plan to expand the system, with SWFMD assistance, is a 

multi-year plan reaching about four years (2004) into the future. That plan calls for 

addition of transmission piping, storage and pumping facilities. The original plan calls for 

system extensions to agricultural lands to the southeast and to a manmade wetland 

2
discharging to the Braden River downstream of the City’s drinking water reservoir. Recent 

events and additional demands for reclaimed water have, however, brought about some 

change to the plan and may result in more changes. 

A major change has been the inclusion of Tropicana Products as a major user of reclaimed 

water. A project now under construction will provide Tropicana with approximately 1.2 

MGD of the City’s reclaimed water. Other industrial users have begun discussion with the 

City regarding use of 2.0 to 4.0 MGD of reclaimed water. That need may occur by early 

2004. Should such be the case, the manmade wetland may be replaced by a user or users 

that would otherwise require ground or surface water supplies. The Florida Power and 

Light orimulsion conversion mention in the last report, did not come to pass so there is no 

proposed use at that location. 

The following information was received from Mr. Cumming in August 2000. 

Year Population Functional 

Population 

Estimated ADF 

(MGD) 

2000 50,500 57,065 6.13 

2005 53,000 59,880 6.43 

2010 55,500 62,715 6.74 

Manatee County Southeast 

North County Regional (Manatee) 

Mr. Leon Kotecki, Planning, was contacted in August 2000. Mr. Kotecki related that the 

Manatee County SE area has had lot of development since 1995, such as Lakewood Ranch 

and six other developments. He also states that there are no changes in discharge methods 

or treatment methods. 

Below is a information provided by Mr. Kotecki: 

Facility Year Population Population 

plus Snowbirds

SE 2010 98,332 114,884 

N 2010 40,082 52,707 

Usage Rate: 105 GPD 

Figure Snowbirds are around for 6 months/year. 

3
City of Oldsmar 

Mr. Jerry Wein was contacted in September 2000, who said there were no changes 

anticipated from the previous estimate. 

City of Mulberry 

Mr. Troy Cassidy was contacted in August 2000 and stated that there were no changes 

from what was last reported. The discharge from the plant would be approximately 0.415 

MGD by 2016. No changes in effluent quality were expected. 

Plant City 

Spoke to Steve Saffels, said they have a new permit as of January 1997, going to have an 

annual of 2.68MGD by 2010. All discharge should be to reuse. The plant is allowed an 

emergency pop-off of 30% of its annual total flow to the East Side Canal. Reuse will be for 

industrial purposed, with approximately 2 MGD to CF Industries. Projected flows for 2012 

were 5.0 MGD. Effluent quality would remain the same for the future. 

City of Palmetto 

Mr. Don Patterson, Interm Public Works Director, said they are permitted for 2.4 MGD but 

currently averages 1.2 MGD over the year. Currently they discharge 50% to Bay (2000) 

hopes by year 2004 have 100% reuse. Predicts flow of plant to be 2.36MGD by 2010 

4
Dale Mabry 

Van Dyke 

Northwest Regional Water Reclamation Facility 

River Oaks 

Falkenburg 

Valrico 

South County 

Summerfield 

Eagles 

Ms. Carole Awad, Senior Engineer, Water/Reclaimed Water Planning Team, Mr. Nick 

Leprici, Engineer II, Wastewater Planning, and Ms. Anita Wang, Engineer II, Wastewater 

Planning, of Hillsborough County, were contacted in August 2000 for information relating 

to the plants of the county. 

Ms. Awad stated that no changes in water quality would occur, as most of the plants were 

already AWT, with the exceptions of Summerfield and Van Dyke, both of which were 

secondary plants. The Van Dyke plant, with all effluent used for spray irrigation, and the 

Eagles plant, with all discharge to a percolation pond, were on-line in 1995. Van Dyke 

was previously a private plant, with 1.5 MGD capacity and approximately 0.6 MGD flow. 

According to Mr. Garrett, the Eagles plant in 1995 had flow of only 0.02 MGD. Ms. Awad 

related that the Summerfield plant is scheduled to go off-line in 1998, with its flow diverted 

to the Falkenburg and Valrico plants. Ms. Awad also stated that the Southern Regional 

facility scheduled to come on-line in 2005 was longer planned. 

Information on the changes in discharge and the modifications in effluent reuse 

percentages were calculated from graphs and tables obtained in a visit with the abovementioned contacts. The county's goal is to have 100% reuse by 2015. 

The following information was obtained from the graphs and tables provided by Ms. Awad 

and Mr. Leprici. 

Hillsborough County Domestic Facilities 

Dale Mabry 

 1995 2000 2005 2010 2015 2020 

Plant Capacity (MGD) 6 6 6 6 6 6 

Plant ADF 3.86 4.35 4.48 4.72 4.96 5.19 

Total Reuse ADF 3.43 * * * * * 

Non-Reuse ADF 0.43 * * * * * 

5
Van Dyke 

 1995 2000 2005 2010 2015 2020 

Plant Capacity (all MGD) 1.5 1.5 1.5 1.5 1.5 1.5 

Plant ADF 0.62 0.7 0.9 1.1 1.3 1.5 

Total Reuse ADF 0.62 * * * * * 

Non-Reuse ADF 0 * * * * * 

Northwest Regional Water Reclamation Facility 

River Oaks 

NW & River Oaks 1995 2000 2005 2010 2015 2020 

NW Plant Capacity (MGD) 5 5 5 5 5 5 

NW Plant ADF 2.49 3.5 3.76 4.02 4.28 4.54 

RO Plant Capacity 10 10 10 10 10 10 

RO Plant ADF 8.14 6.33 7.08 7.41 7.74 8.07 

NW/RO Total Reuse ADF 1.69 * * * * * 

NW/RO Non-Reuse ADF 8.94 * * * * * 

Combined Total Northwest 

Plant ADF 15.11 14.88 16.22 17.25 18.28 

Reuse ADF 5.74 6.53 11.47 13.12 14.09 14.61 

Non-Reuse ADF 9.37 8.35 4.75 4.13 4.19 4.69 

* In 2000, the Northwest WWTP reuse systems were interconnected and flows were 

transferred throughout reuse systems. Reuse & Non-Reuse ADF shown is for entire 

Northwest area 

Falkenburg 

Valrico 

Falkenburg & Valrico 1995 2000 2005 2010 2015 2020 

F Plant Capacity (all MGD) 6 6 9 9 9 12 

F Plant ADF 3.8 4.87 6.34 6.56 8.45 10.35 

V Plant Capacity 3 4 6 12 12 12 

V Plant ADF 2.7 3.72 4.76 6.94 8.38 9.55 

TOT Total Reuse ADF 3.58 * * * * * 

TOT Non-Reuse ADF 2.92 * * * * * 

 

6
* Combined Valrico and Falkenburg 

Val/Falk Plant Flow 6.5 8.59 11.1 13.5 16.83 19.9 

Val/Falk Reuse ADF 3.58 6.51 * * * 22.6 

Val/Falk Non-Reuse ADF 2.92 4.97 * * * 1.6 

*In 1998, the Valrico and Falkenburg reuse systems were interconnected. 

149A,B - South County 

South County 1995 2000 2005 2010 2015 2020 

Plant Capacity (all MGD) 4.5 4.5 4.5 4.5 4.5 4.5 

Plant Flow ADF 2.7 2.88 3.89 4.5 4.5 4.5 

Plant Reuse ADF 2.4 2.42 * * * * 

Plant Non-Reuse ADF 0.3 0.46 * * * * 

 

* Combined Central and South Reuse Systems 

S-C Plant ADF 9.2 11.47 14.99 18 21.33 24.4 

S-C Reuse 5.98 8.93 14.12 17.68 20.12 22.72 

S-C Non-Reuse ADF 3.22 2.54 0.87 0.32 1.21 1.68 

* In 2002, WWTP's in the South/Central area are anticipated to be interconnected. Reuse 

& Non-Reuse ADF shown is for entire South/Central area 

Summerfield - Offline in 1998 

Eagles 

Summerfield 1995 2000 2005 2010 2015 2020 

Plant Capacity 0.75 0.75 

Demand 0.12 0.22 

Eagles 1995 2000 2005 2010 2015 2020 

Plant Capacity 0.15 0.3 0.3 0.3 0.3 0.3 

Demand 0.01 0.12 0.17 0.22 0.24 0.24 

Eastlake Woodlands 

Pine Ridge 

Tarpon Woods 

Tarpon Lake Village 

No changes to current discharge rate. 100% reclaimed. 

By 2010, Tarpon Lake & Tarpon Woods are to be diverted to the NW Facility. 

7
MacDill 

Mr. Mike Harr, Water Program Manager was contacted in 2000. He stated that the plant 

capacity will remain the same, and effluent quantity will as well. Currently at 100% reuse. 

Howard Curren 

Spoke to Mr. Bill Schafer, Head of Planning, said in the next 10 years the plant will remain 

the same. 

The following information on projected growth demand (MGD) was obtained from the 

Tampa Comprehensive Plan: 

Year 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 

ADF 0.54 0.75 0.96 1.07 1.13 1.19 1.25 1.31 1.37 1.43 

Extrapolations to 2010 were as follows: 

Year 2005 2006 2007 2008 2009 2010 

ADF 1.49 1.55 1.61 1.67 1.73 1.79 

8
Industrial Point Sources Projected Plans for 2010 

IMC AGRICO - Kingsford 

IMC AGRICO - Four Corners 

IMC AGRICO - Port Sutton 

IMC AGRICO - Lonesome 

Received no information regarding any changes from Mr. Greg Williams, Environmental 

Superintendent. 

CF Industries - Plant City 

Corresponded with Mr. Tom Edwards, Superintendent, who stated that the Plant City 

facility does plan on increasing production and does expect an increase in the volume of 

nutrients produced. He also stated that they do not anticipate any extra runoff due to the 

closing of a gypsum stack by 2004. They expect to be very dynamic over the next 10 

years which will keep the quality and quantity of nitrogen from their facility to be the 

same. 

Pakhoed Dry Bulk Terminals - 

Spoke to Mr. Chris Tolbert, Manager of Environmental Safety and Health and he anticipates 

no increase in quality or quantity nitrogen from their facility. 

Farmland Hydro - Green Bay Plant 

Mr. Chuck Jenkins, Manager of Environment and Safety Services, stated that they have 

decreased nitrogen output over the past four years and he anticipates no increase in quality 

or quantity of nitrogen from their facility. 

Tropicana 

 

Contacted Mr. Doug Foster, Environmental Affairs Manager, who said that they plan to be 

100% deep well injection by end of 2000. They anticipate no other changes. 

9
AGRIFOS – Nichols Mine 

Spoke to Mr. Tom Abel, Environmental Engineer, who said the facility was closed on 6 

August 2000 and there is no anticipated reopening date at the time. He also stated that if 

the facility did reopen that they expect no changes that would affect nitrogen loadings. 

CARGILL – East Tampa 

 

Ms. Melody Foley was contacted in September 2000, and anticipates no increase in the 

quality or quantity of nitrogen from their facility. 

TECO - Gannon Station 

TECO - Big Bend Station 

Contacted Mr. Stan Maloy who anticipates no increase in quality or quantity of nitrogen 

from their facility. 

Bridgeway Acres Class I Landfill 

Spoke with Ms. Kelsy Oswald, Solid Waste Specialist, who stated that the landfill is 

currently changing intake structures to decrease turbidity which should then decrease 

metals in their runoff. She stated that their runoff is rainfall driven so it is difficult to predict 

completely runoff amounts. Ms. Oswald also stated that they are starting new plans to 

have 0% of wastewater to go offsite. This should all take place before 2010. 

DEP Stock Enhancement Program 

Corresponded with Frank Courtney, Assistant Research Scientist, who said that any changes 

to the Stock Enhancement Research facility are funding dependent. If increase funding, 

plan to increase stock production. Along with that there would be an increase to the 

wastewater treatment systems. They do plan to implement better treatment methods if this 

expansion does happen. 

Florida Juice 

 

Was being sold as of August 1999 and was unable to reach anyone other than the 

receptionist who had no comment. 

10
Mulberry Phosphates 

Spoke with Mr. Paul Moore who anticipates no increase in quality or quantity of nitrogen 

from their facility. 

Nitram Chemical 

Mr. Dan Ross was contacted, and anticipates no increase in quality or quantity of nitrogen 

from their facility. 

Coronet Industries 

Spoke with Mr. Viet Ta, Environmental Manager, who anticipates no increase in quality or 

quantity of nitrogen from their facility. 

11
APPENDIX 2 

AGGREGATED FLORIDA LAND USE AND COVER CLASSIFICATION 

SYSTEM CATEGORIES 

1
URBAN LAND USE CATEGORIES 

Coastal Land Use Code FLUCCS Code 

1 - Low Density Residential 1100 

2 - Medium Density Residential 1200 

3 - High Density Residential 1300 

4 - Commercial 1400 

5 - Industrial 1500 

7 - Institutional, Transportation, Utilities 1700 

8100 

8200 

8300 

AGRICULTURAL LAND USE CATEGORIES

Coastal Land Use Code FLUCCS Code 

6 - Mining 1600 

11 - Groves 2200 

2210 

2220 

2230 

12 - Feedlots 2300 

13 - Nursery 2400 

14 - Row and Field Crops 2100 

2140 

2150 

2440 

2
UPLAND FORESTED LAND USE CATEGORIES

Coastal Land Use Categories FLUCCS Code 

8 - Range Lands 1480 

1800 

1900 

2420 

2600 

3100 

3200 

3300 

9 - Barren Lands 7100 

7200 

7300 

7400 

10 - Pasture 2110 

2120 

2130 

15 - Upland Forests 4100 

4110 

4120 

4200 

4300 

4340 

4400 

3
WATER AND WETLANDS LAND USE CATEGORIES

Coastal Land Use Categories FLUCCS Code 

16 - Freshwater 2500 

2540 

2550 

5100 

5200 

5210 

5220 

5230 

5240 

5300 

5310 

5320 

5330 

5340 

5500 

5600 

6440 

6450 

17 - Saltwater 5400 

9113 

9116 

9121 

18 - Forested Freshwater Wetlands 6100 

6110 

6150 

6200 

6210 

6240 

6300 

19 - Saltwater Wetlands 6120 

6420 

20 - Non-forested Freshwater Wetlands 6400, 6410, 

6411, 6430 

6530 

21 - Tidal Flats 6500, 6510 

6520 

4
APPENDIX 3 

LAND USE-SPECIFIC SEASONAL RUNOFF COEFFICIENTS 

1
Seasonal Land Use-Specific 

Runoff Coefficients

Coastal Land Use Classification and 

Land Use Type 

Hydrologic 

Soil 

Group

Dry 

 Season 

 Runoff 

 Coefficient

Wet 

Season 

Runoff 

Coefficient

1) Single Family Residential A 0.15 0.25 

B 0.18 0.28 

C 0.21 0.31 

D 0.24 0.34 

2) Medium Density Residential A 0.25 0.35 

B 0.30 0.40 

C 0.35 0.45 

D 0.40 0.50 

3) Multifamily Residential A 0.35 0.50 

B 0.42 0.57 

C 0.50 0.65 

D 0.58 0.75 

4) Commercial A 0.70 0.79 

B 0.74 0.83 

C 0.78 0.97 

D 0.82 0.91 

5) Industrial A 0.65 0.75 

B 0.70 0.80 

C 0.75 0.85 

D 0.80 0.90 

6) Mining A 0.20 0.20 

B 0.30 0.30 

C 0.40 0.40 

D 0.50 0.50 

2
Seasonal Land Use-Specific 

Runoff Coefficients

Coastal Land Use Classification and 

Land Use Type 

Hydrologic 

Soil 

Group

Dry 

 Season 

 Runoff 

 Coefficient

Wet 

Season 

Runoff 

Coefficient

7) Institutional, Transportation Utils. A 0.40 0.50 

B 0.45 0.55 

C 0.50 0.60 

D 0.55 0.65 

8) Range Lands A 0.10 0.18 

B 0.14 0.22 

C 0.18 0.26 

D 0.22 0.30 

9) Barren Lands A 0.45 0.55 

B 0.50 0.60 

C 0.55 0.65 

D 0.60 0.70 

10) Agricultural - Pasture A 0.10 0.18 

B 0.14 0.22 

C 0.18 0.26 

D 0.22 0.30 

11) Agricultural - Groves A 0.20 0.26 

B 0.23 0.29 

C 0.26 0.32 

D 0.29 0.33 

12) Agricultural - Feedlots A 0.35 0.45 

B 0.40 0.50 

C 0.45 0.55 

D 0.50 0.60 

3
Seasonal Land Use-Specific 

Runoff Coefficients

Coastal Land Use Classification and 

Land Use Type 

Hydrologic 

Soil 

Group

Dry 

 Season 

 Runoff 

 Coefficient

Wet 

Season 

Runoff 

Coefficient

13) Agricultural - Nursery A 0.20 0.30 

B 0.25 0.35 

C 0.30 0.40 

D 0.35 0.45 

14) Agricultural - Row and Field Crops A 0.20 0.30 

B 0.25 0.35 

C 0.30 0.40 

D 0.35 0.45 

15) Upland Forested A 0.10 0.15 

B 0.13 0.18 

C 0.16 0.21 

D 0.19 0.24 

16) Freshwater - Open Water A 0.80 0.90 

B 0.80 0.90 

C 0.80 0.90 

D 0.80 0.90 

17) Saltwater - Open Water A 1.0 1.0 

B 1.0 1.0 

C 1.0 1.0 

D 1.0 1.0 

18) Forested Freshwater Wetlands A 0.50 .60 

B 0.55 0.65 

C 0.60 0.70 

D 0.65 0.75 

4
Seasonal Land Use-Specific 

Runoff Coefficients

Coastal Land Use Classification and 

Land Use Type 

Hydrologic 

Soil 

Group

Dry 

 Season 

 Runoff 

 Coefficient

Wet 

Season 

Runoff 

Coefficient

19) Saltwater Wetlands A 0.95 0.95 

B 0.95 0.95 

C 0.95 0.95 

D 0.95 0.95 

20) Non-forested Freshwater Wetlands A 0.45 0.55 

B 0.50 0.60 

C 0.55 0.65 

D 0.60 0.70 

21) Tidal Flats A 1.0 1.0 

B 1.0 1.0 

C 1.0 1.0 

D 1.0 1.0 

5
APPENDIX 4 

LAND USE-SPECIFIC RUNOFF WATER QUALITY CONCENTRATIONS 
Land Use-Specific Nonpoint Source Water Quality Concentrations 

URBAN LAND USES

Land Use Classification Land Use-Specific Water Quality 

Concentrations

Coastal 

Land Use 

Classification

Land Use 

Description Reference

TN 

(mg/L)

TP 

(mg/L)

TSS 

(mg/L)

BOD 

(mg/L)

1 

(LDR)

Low Density 

Single Family 

Residential 

(SFR)

(1) 

(1) 

(1) 

(1) 

(1) 

(1) 

(4) 

(8) 

(9) 

(10) 

(11) 

(13)

2.31 

2.14 

0.605 

1.18 

3.0 

2.2 

1.87 

1.46 

1.56 

2.04 

2.88 

-

0.40 

0.32 

0.073 

0.307 

0.45 

0.25 

0.39 

0.401 

0.27 

0.593 

0.72 

-

33.0 

28.0 

7.2 

3.5 

- 

- 

- 

19.0 

20.8 

49.7 

56.8 

-

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

4.4

min 

mean 

max

0.605 

1.93 

2.88

0.073 

0.380 

0.598

3.5 

27.3 

56.8

- 

4.4 

-

2 

(MDR)

Medium 

 Density 

(See notes)

mean 2.04 0.44 33.5

- 

7.4 

-

3 

(HDR)

Multifamily 

Residential

(1) 

(1) 

(1) 

(1) 

(1) 

(1) 

(4) 

(8) 

(9) 

(10) 

(11) 

(13)

1.61 

2.57 

4.68 

1.91 

1.02 

1.91 

1.65 

2.05 

2.04 

2.05 

2.00 

-

0.33 

0.45 

0.72 

0.73 

0.033 

0.51 

0.33 

1.34 

0.282 

0.150 

0.56 

-

53.0 

36.8 

95.6 

- 

67.6 

14.3 

- 

29.0 

10.7 

8.3 

41 

-

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

11.0

min 

mean 

max

1.02 

2.14 

4.68

0.033 

0.49 

1.34

8.3 

39.6 

95.6

- 

11.0 

-
Coastal 

Land Use 

Classification

Land Use 

Description Reference

TN 

(mg/L)

TP 

(mg/L)

TSS 

(mg/L)

BOD 

(mg/L)

4 Low Intensity 

Commercial 

High Intensity 

Commercial 

Commercial 

(Office) 

Commercial 

(Retail)

(1) 

(1) 

(1) 

(1) 

(1) 

(8) 

(9) 

(10) 

(11) 

(8) 

(10) 

(11)

1.19 

1.10 

2.81 

3.53 

2.15 

2.38 

1.08 

1.40 

1.05 

1.69 

1.28 

2.12

0.15 

0.10 

0.31 

0.82 

0.15 

0.305 

0.495 

0.113 

0.145 

0.253 

0.177 

0.22

22.0 

45.0 

94.3 

- 

- 

36.5 

50.6 

6.2 

13.8 

9.3 

14.5 

36.3

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

-

Combined 

Commercial

min 

mean 

max

1.05 

1.82 

3.53

0.100 

0.270 

0.495

6.2 

32.9 

94.3

- 

17.2 

-

5 Industrial (1) 

(1) 

(4) 

(8) 

(9) 

(10) 

(11) 

(13)

1.42 

1.42 

1.18 

2.28 

1.77 

1.92 

3.00 

-

0.19 

0.31 

0.15 

0.332 

0.465 

0.490 

0.503 

-

71.8 

102.0 

- 

18.2 

28.3 

84.3 

70.0 

-

- 

- 

- 

- 

- 

- 

- 

9.6

6 Mining (4) 

(13)

1.18 

-

0.15 

-

35 (e) 

-

- 

9.6

7 Institutional (4) 

(13)

1.18 

-

0.15 

-

35 (e) 

-

- 

8.2
AGRICULTURAL LAND USES

Land Use 

Classification

Land Use-Specific 

Water Quality Concentrations

Coastal 

Land Use 

Classification

Land Use 

Description Reference

TN 

(mg/L)

TP 

(mg/L)

TSS 

(mg/L)

BOD 

(mg/L)

10 Pasture (1) 

(1) 

(2) 

(3) 

(4) 

(5) 

(13)

2.37 

2.48 

2.0 

3.0 

1.02 

5.1 

-

0.697 

0.27 

0.3 

0.25 

0.16 

3.2 

-

- 

8.6 

- 

- 

- 

- 

-

- 

- 

- 

- 

- 

- 

5.1

11 Grove (7) 

(13)

2.31 

-

0.10 

-

- 

-

- 

2.55

11,13 Grove, 

Nursery

(4) 

(13)

0.92 

-

0.41 

-

- 

-

- 

2.55

12 Feed Lot (3) 

(3) 

(5) 

(13)

29.3 

3.74 

26.0 

-

5.1 

1.13 

5.1 

-

- 

- 

- 

-

- 

- 

- 

5.1

14 Field Crop (2) 

(3) 

(4) 

(13)

2.5 

2.5 

3.75 

-

0.25 

2.5 

1.13 

-

- 

- 

- 

-

- 

- 

- 

5.1

Mixed Agricultural

10,11 Citrus+ 

Pasture

(1) 

(1) 

(1) 

(1) 

(1)

1.57 

1.33 

2.58 

2.68 

3.26

0.09 

0.09 

0.046 

0.562 

0.24

- 

4.6 

180 

- 

28.0

- 

- 

- 

- 

-

11,14 Citrus+ Row 

Crops

(6) 1.78 0.3 5.6 -

(See following page for summarized agricultural water quality concentrations.) 
SUMMARIZED AGRICULTURAL LAND USE DATA

Land Use 

Classification

Land Use-Specific 

Water Quality Concentrations

Coastal 

Land Use 

Classification

Land Use 

Description Reference

TN 

(mg/L)

TP 

(mg/L)

TSS 

(mg/L)

BOD 

(mg/L)

8 Range min 

mean 

max

0.90 

1.24 

1.47

0.02 

0.01 

0.21

4.8 

11.0 

17.3

- 

1.45 

-

10 Pasture min 

mean 

max

1.0 

2.66 

5.1

0.16 

0.81 

3.2

8.6 

8.6 

8.6

- 

5.1 

-

11 Grove min 

mean 

max

0.92 

1.67 

2.31

0.10 

0.27 

0.41

5.0 

5.3 

5.6

- 

2.55 

-

12 Feed Lot min 

mean 

max

3.74 

19.7 

29.3

1.13 

3.8 

5.1

50(e) 

- 

5.1 

-

13 Nursery 

(See notes)

mean 1.67(e) 0.27(e) 5.3(e) 2.55

14 Row Crop 

(See notes)

mean 2.91 0.54 10 5.1
WATER/WETLAND AND FOREST/UNDEVELOPED LAND USES

Land Use 

Classification

Land Use-Specific 

Water Quality Concentrations

Coastal 

Land Use 

Classification

Land Use 

Description Reference

TN 

(mg/L)

TP 

(mg/L)

TSS 

(mg/L)

BOD 

(mg/L)

8 Open Space/ 

Non-forested

(1) 

(1) 

(1) 

(4) 

(13)

1.38 

0.90 

1.47 

1.02 

-

0.07 

0.02 

0.07 

0.16 

-

17.3 

4.8 

- 

- 

-

- 

- 

- 

- 

1.45

15 Upland Forest (2) 

(3) 

(4) 

(13)

0.1 

0.2 

1.02 

-

0.007 

0.007 

0.16 

-

- 

- 

- 

-

- 

- 

- 

1.45

16,17 Open Water (1) 

(1) 

(1) 

(13)

0.79 

0.73 

2.22 

-

0.17 

0.04 

- 

-

- 

0.00 

6.2 

-

- 

- 

- 

0.00

18,20 Freshwater 

Wetland

(1) 

(1) 

(1) 

(1) 

(4) 

(13)

2.26 

1.02 

1.24 

1.88 

0.79 

-

0.09 

0.16 

0.018 

0.33 

0.17 

-

13.4 

- 

4.6 

12.7 

- 

-

- 

- 

- 

- 

- 

4.63

17 Saltwater NA NA NA NA

19 Saltwater 

Wetlands

NA NA NA NA

21 Tidal Flats NA NA NA NA
Notes: • Concentrations for CLUCCS code 2 (MDR) are an average of CLUCCS codes 

1 (LDR) and 3 (HDR). 

• Concentrations for CLUCCS code 4 (Commercial) are an average of reported 

values for "low intensity" and "high intensity" commercial. 

• Estimated (e) agricultural values were based on similar land uses data when 

no land use specific data were identified. 

 • Row crop data were often reported with other agricultural uses. 

 • Saltwater and saltwater wetlands were assigned zero loads. 
References 

(1) Harper, H.H. 1991. Estimation of Loading Rate Parameters for Tampa Bay Watershed. 

Southwest Florida Water Management District. Brooksville, Florida. 

(2) Delwiche, Lora L.D. and D.A. Haith. 1983. Loading Functions for Predicting Nutrient 

Losses from Complex Watersheds. Water Resources Bulletin vol. 19, no. 6. p. 951-959. 

(3) Haith, D. A. and L.L. Shoemaker. 1987. Generalized Watershed Loading Function for 

Stream Flow Nutrients. Water Resources Bulletin. vol. 23, no. 3. p. 471-477. 

(4) Camp, Dresser, & McKee. 1992. Point/Non-Point Source Loading Assessment for Sarasota 

Bay. SBNEP, Sarasota, Florida. 

(5) Andrews, W.J. 1992. Reconnaissance of Water Quality at Nine Dairy Farms in North 

Florida, 1990-1991. USGS WRI 92-4058. Tallahassee, Florida. 

(6) Flannery, M.S. et al. 1991. Increased Nutrient Loading and Baseflow Supplementation in 

the Little Manatee Watershed. in: Treat, F.S. and P.A. Clark (eds.) Proceedings, Tampa Bay 

Area Scientific Information Symposium 2. 1991 February 27-March 1. Tampa, Florida. p. 

369-396. 

(7) Allhands, M. 1993. Water Quality Data for Gator Slough Groves. Agricultural 

Management Services. Punta Gorda, Florida. 

(8) Hillsborough County Engineering Services. 1993. NPDES Part 2 Application. Tampa, FL. 

(9) City of Tampa Stormwater Management Division. 1994. NPDES Part 2 Application. 

Tampa, FL. 

(10) Pinellas County Department of Environmental Management. 1993. NPDES Part 2 

Application. Clearwater, FL. 

(11) City of St. Petersburg Engineering Department. 1993. NPDES Part 2 Application. St. 

Petersburg, FL. 

(12) Carr, D.W. and B.T. Rushton. 1995. Integrating a Native Herbaceous Wetland into 

Stormwater Management. Southwest Florida Water Management District Stormwater 

Research Program. Brooksville, FL. 

(13) Harper, H.H. 1994. Stormwater Loading Rate Parameters for Central and South Florida. 

Environmental Research & Design, Inc. Orlando, FL. 
APPENDIX 5 

EXISTING AND PROJECTED FUTURE LAND USE ACREAGES, FROM PREVIOUS STUDY 

(ZARBOCK ET AL., 1996A) AND UPDATED 
Previous Analysis - Tampa Bay Watershed, 1990 Land Use (Acres) by Segment and Basin 

Bay 

Segment

Basin 

Single 

Family 

Res. 

Medium

Density 

High 

Density 

Res. 

Comm. Indust. Mining

Inst. 

Trans.

Utility 

Range Barren Land Pasture Grove Feedlot Nursery Row Crops Upland Forest Fresh Water Forest Wetl. 

 OTB  02306647 730 1647 3205 850 617 194 454 1282 11 79 249 0 37 0 340 1523 738  02307000 2050 2989 5007 392 156 34 885 4682 60 2680 512 0 120 24 929 2744 4809  02307359 1844 2031 269 15 0 55 203 3248 5 3094 1273 0 108 0 2961 1958 5451  206-1 4492 21584 6855 3685 143 9834 9729 157 2205 316 0 165 0 6459 2779 5840  LTARPON 862 989 357 1 5 405 1752 26 441 26 0 12 0 862 414 2005  HB  02300700 409 230 151 104 19 78 379 2425 0 5801 1158 5 97 2934 2122 516 1480  02301000 4541 5840 457 617 798 29171 1871 4755 47 16220 8202 2470 126 447 5194 3547 4762  02301300 157 0 0 0 4 15591 101 2142 0 5734 3202 0 0 0 2615 469 5437  02301500 3953 1472 44 235 237 41306 619 3460 357 16479 5577 235 279 1537 6620 1430 9468  02301695 467 1400 557 113 0 0 140 581 3 291 96 0 6 0 225 157 257  02301750 411 1863 987 1073 20 710 1638 48 829 221 221 38 7 0 560 362 121  02303000 10246 9260 3686 1971 1512 2703 2426 21138 336 46164 4351 756 376 724 15196 2905 24222  02303330 11892 4802 2068 1506 661 627 1355 14902 523 31261 4801 189 984 3148 9671 2975 3154  02304500 6877 8178 5227 2785 669 290 4374 25552 608 28662 3846 121 214 608 17975 5276 31985  204-2 1905 6161 467 413 6 2383 595 3973 94 12374 652 299 105 62 10640 1109 4590  205-2 100 496 10588 3318 152 27 1589 918 2 0 20 0 3 0 374 373 43  206-2 2086 1948 7799 4252 2036 1560 6062 6203 1213 6520 133 133 115 112 4174 1855 682  TBYPASS 2255 1629 1426 1616 587 174 1231 2275 154 1810 530 123 64 0 1006 742 999  MTB  02300500 816 274 85 112 0 2293 185 14411 46 35459 9443 34 123 5586 9428 4311 10104  02300530 0 38 941 155 0 0 167 1047 0 482 0 0 5 412 360 321 611  203-3 1876 1342 934 352 113 130 963 5606 37 8119 3371 36 198 4899 4766 1055 4614  206-3C 0 6 14 3 0 0 2677 52 2 0 0 0 0 0 514 68 151  206-3E 118 117 864 219 126 1238 924 2183 5 4756 767 6 118 2624 936 555 1688  206-3W 82 1256 12966 2347 637 0 2009 1835 6 0 0 0 44 0 836 857 510  LTB  206-4 809 794 493 166 67 448 1528 2326 21 2625 3724 10 170 647 669 635 2915  BCB  206-5 29 308 1251 90 0 0 566 947 1 0 0 0 0 0 171 101 42  207-5 987 2191 24933 4954 2136 16 3569 3417 53 18 433 0 162 27 1411 855 844  TCB  206-6 600 379 1073 288 39 0 301 756 0 1094 409 0 106 27 432 130 516  MR  02299950 0 0 0 0 0 1120 127 16106 0 9790 2731 0 0 529 6702 16 1171  202-7 4815 2909 8213 2095 882 213 2584 11675 91 22644 5156 739 502 9984 11018 1718 11329  EVERSRES 479 221 1198 30 0 1245 548 6426 19 8194 322 0 17 3057 7351 1104 2843  LMANATEE 205 0 0 0 0 0 132 10156 52 10081 2553 8 0 3045 8854 1446 1739 TOTAL 64266 65262 119253 37283 15160 101754 50441 186008 4758 283298 64074 5202 4263 40433 141371 44306 145120 

Fresh 

Res. 

2665

2766
Previous Analysis - Tampa Bay Watershed Future Conditions (circa 2010), Land Use (Acres) by Major Basin 

Bay SegmentBasin 

Single Family Res. 

MediumDensity Res. 

High Density Res. 

Comm Indust. Mining 

Inst. Trans.Utility 

Range Barren Land Pasture Grove Feedlot Nursery Row Crops Upland Forest Fresh Water Forest Fresh Wetl. 

OTB 

 02306647 621 1812 3686 935 630 194 454 769 10 75 199 0 37 0 273 1523 738 

 02307000 1845 3577 6008 431 164 34 972 4236 60 2268 409 0 120 20 2744 4349  02307359 2213 2416 331 15 55 213 2932 5 2784 1252 0 95 0 2795 1958 5451  206-1 4752 22460 6994 3697 143 9002 157 2007 316 0 165 0 6001 2779 5840  LTARPON 905 1137 3181 375 1 5 409 1409 331 23 0 12 0 690 414 2005  HB 

 02300700 460 219 156 19 78 379 1940 0 5801 1089 5 97 2729 2122 516 1480 

 02301000 4768 6424 594 838 30040 1871 4256 47 16230 6935 2470 126 424 5077 3524 4762  02301300 157 0 0 4 101 2142 0 3202 0 0 0 2615 469 5437  02301500 4623 1829 88 419 284 41306 647 3291 357 15989 5361 235 279 1383 6319 1430 9468  02301695 490 1540 624 119 0 0 140 465 3 235 77 0 6 0 180 157  02301750 411 1863 987 1073 20 1638 48 828 221 221 38 7 0 560 362 121  02303000 12927 11277 4637 2562 1663 2703 2547 18157 336 44317 3959 756 376 652 13976 2905 24222  02303330 14268 5956 2689 1807 694 1355 14902 523 28135 4105 189 984 2883 9273 2975 3154  02304500 8547 10854 5996 3117 669 290 4374 22784 608 26647 3547 121 214 781 17436 5276 31985  204-2 2267 7393 701 496 6 2383 625 3655 94 11319 619 299 105 59 10108 1109 4590  205-2 100 496 10588 3318 152 918 2 0 0 3 0 374 373 43  206-2 2141 2031 8072 4262 2049 1560 6062 6069 1212 6333 133 133 115 4098 1855 682  TBYPASS 2255 1521 1648 593 174 1231 2207 154 1756 488 123 0 956 742 999  MTB 

 02300500 1624 411 128 182 0 2293 370 13739 46 35702 9443 34 8861 4311 10104 

 02300530 0 941 155 0 0 167 1047 0 482 0 0 5 412 360 321 611  203-3 2183 1543 1046 370 115 130 963 5494 37 7808 3371 36 198 4807 4641 1055 4614  206-3C 0 6 14 3 0 0 2677 52 2 0 0 0 514 68 151  206-3E 142 152 1123 263 132 1237 933 2074 5 4613 767 6 118 2546 889 555 1688  206-3W 80 13422 2370 637 0 2009 1431 5 0 0 0 44 0 794 857 505  LTB 

 206-4 1052 1112 592 199 69 448 1528 1946 21 2360 3707 10 170 634 649 635 2915 

 BCB 

 206-5 29 317 1289 91 0 0 566 900 1 0 0 0 0 0 170 101 42 

 207-5 960 2191 25422 5009 2136 16 3569 2910 53 18 433 0 162 27 1411 855 834  TCB 

 206-6 780 493 1188 294 39 0 301 605 0 875 409 0 106 24 390 130 516 

 MR 

 02299950 0 0 0 0 0 1120 127 16106 0 9790 2731 0 0 529 6702 16 1171 

 202-7 7223 4364 11498 2514 926 213 2636 9924 91 18794 5156 739 9097 9916 1718 11329  EVERSRES 958 442 2396 36 0 1245 548 5783 19 7365 322 0 17 2967 7010 1104 2842  LMANATEE 226 0 0 0 0 0 132 9953 52 9984 2808 8 0 3069 8854 1446 1739 TOTAL 77334 77827 131441 39892 15537 102622 51069 171146 4754 267973 61102 5202 4251 38488 134850 44283 144644 

836

0 

2721 9936

26

818 

679 

0 15591 5734

257 

710627

27 1589 20

106

1710 64

123 5339

38

0 0

1231

503
Updated Analysis - Tampa Bay Watershed Future Conditions (circa 2010), Land Use (Acres) by Major Basin

Bay SegmentBasin 

Single 

Family

Res. 

Med. 

Density 

Res. 

High 

Density 

Res. 

Comm. Indust. Mining

Inst. 

Trans.

Utility 

Range Barren Land Pasture Grove Feedlot Nursery Row Crop Upland Forest Fresh Water Open Saltwater F

W

 OTB 02306647 2083 3600 976 711 104 587 639 0 45 109 0 16 0 300 1492 0 02307000 1937 3861 6064 470 101 12 1198 3590 0 2021 694 0 99 0 664 2916 0 02307359 2322 2663 374 19 0 77 225 2278 0 3093 1219 0 122 0 2773 2066 0 206-1 2735 4906 23247 7722 3975 217 10723 7281 46 1825 291 0 109 0 5198 2992 46512 LTARPON 924 1683 3267 443 2 0 563 1010 0 85 20 0 7 0 567 2982 0  HB 02300700 656 427 288 163 35 141 427 1915 12 3427 1243 5 173 4769 2124 623 0 02301000 5871 7581 590 1188 1017 29301 4249 170 11011 3585 17 116 1877 6551 2305 0 02301300 315 31 0 13 0 18862 83 838 0 5112 2810 7 32 148 1989 613 0 02301500 5183 2047 175 436 288 41494 669 3255 237 14691 6134 178 94 2569 5629 2155 0 02301695 510 1800 903 130 0 0 161 178 0 84 79 0 10 0 176 148 0 02301750 439 2115 1638 1383 27 0 906 825 7 442 125 0 10 0 398 420 0 02303000 12851 10787 5260 2681 1824 2737 3167 18300 42550 5117 343 14268 2963 0 02303330 14792 6301 2576 2103 766 672 1708 10314 175 23811 4518 154 779 2787 8798 3249 0 02304500 10641 13618 7829 4238 848 557 5872 14797 146 24231 5360 73 255 615 17890 5985 0 204-2 2467 7127 1155 503 9 2296 697 2673 10 11281 667 285 309 1105 9777 1342 511 205-2 119 505 11138 3609 161 10 1581 272 0 0 22 0 2 0 124 650 5 206-2 2405 2058 9027 4512 2327 1181 6266 4677 678 6059 287 121 58 171 4338 2343 19850 TBYPASS 2421 1750 1622 1790 633 170 1307 1875 9 1688 456 67 56 13 949 1151 0  MTB 02300500 1368 448 130 185 36 8169 320 10005 62 29180 10143 35 282 10906 8119 4505 0 02300530 43 52 1131 182 0 0 174 891 0 521 0 0 2 287 276 346 0 203-3 2291 1536 1193 364 125 200 1435 3673 12 5775 3465 40 200 5836 1151 1391 206-3C 0 5 0 0 2666 86 15 0 0 0 0 494 84 60483 

339 1119 261 166 1549 1217 1350 0 3749 816 5 117 3197 901 620 1184 

206-3W 73 189 14583 2445 668 0 1999 1536 2 0 0 0 44 0 664 912 2219  LTB 206-4 1199 451 1351 184 140 450 1993 1583 17 2392 3667 10 188 420 685 709 59996  BCB 206-5 38 33 1642 97 0 0 594 892 22 0 0 0 0 0 174 99 11431 207-5 858 1321 27801 5255 2287 7 3564 1865 30 15 45 0 0 838 1670 9123  TCB 206-6 732 526 1445 371 46 0 371 340 10 737 443 0 109 8 420 138 3855  MR 02299950 0 0 0 0 0 1337 275 15570 0 7453 3862 0 0 2058 6452 151 0 202-7 8502 5776 14551 3443 1192 220 3540 6203 59 16414 5278 361 341 11218 7099 1811 7616 EVERSRES 921 1552 2752 178 0 1500 976 5682 35 7381 383 0 5 3245 6202 1423 0 LMANATEE 589 19 0 50 0 0 211 9694 0 10141 3419 0 20 6637 4247 1631 0 TOTAL 84138 83584 146477 45399 17383 111264 57576 138336 1775 235214 64256 2268 3951 58865 123742 51646 157296 1

672

2102 

20 912 998

4657

0 27 0

206-3E 264

54
Updated Analysis - Tampa Bay Watershed, 1995 Land Use (Acres) by Segment and Basin

Bay SegmentBasin 

Single 

Family 

Res. 

Med 

Density 

Res. 

High 

Density 

Res. 

Comm Indust. Mining

Inst. 

Trans.

Utility 

Range Barren Land Pasture Grove Feedlot Nursery Row Crops Upland Forest Fresh Water Open Saltwater F

W

OTB 02306647 746 1984 3000 929 697 104 534 1040 0 64 156 0 27 0 334 1658 0 

02307000 2152 3677 5053 447 91 12 4025 0 2377 771 0 124 0 781 2916 0 02307359 2019 2048 250 12 77 161 2590 0 3437 1354 0 136 0 3081 2066 0 206-1 2604 4460 22140 7020 3786 217 10213 9022 91 2147 324 0 136 0 6116 2992 46512 LTARPON 840 1530 2970 403 2 0 469 1500 0 121 20 0 7 0 709 2982 0 HB 02300700 418 272 262 109 22 94 356 2128 12 3707 1243 5 173 4769 2236 623 0 02301000 5592 7220 536 1132 969 29301 2002 4473 170 11478 3585 17 116 2086 6551 2305 0 02301300 178 17 0 7 0 19054 47 838 0 5112 2810 7 32 148 613 0 02301500 4712 1861 175 363 240 42341 608 3356 237 14996 5841 178 2446 5629 2155 0 02301695 425 1500 704 109 0 0 161 445 0 279 99 0 10 0 220 148 0 02301750 366 1922 1092 1317 25 0 697 1324 7 736 250 0 10 0 568 0 02303000 10709 8989 4384 1520 2281 2639 20334 20 46250 5117 912 343 998 15085 2963 0 02303330 11834 5041 2061 1683 613 672 1366 11460 175 25609 5315 193 974 3484 9775 3249 0 02304500 7094 9078 5592 3027 707 507 4517 19121 183 32308 5955 121 255 615 17890 5985 0 204-2 2056 6197 1050 457 7 2296 581 2970 10 11972 702 356 309 1105 10292 1342 511 205-2 111 472 10606 3373 151 10 1581 907 0 0 22 0 2 0 309 650 5 206-2 2291 1871 8206 4297 2115 1181 5967 5772 848 6326 319 151 64 190 4566 2343 19850 TBYPASS 2305 1591 1544 1705 603 170 1189 2083 17 1875 507 133 62 15 1006 1151 0 MTB 02300500 912 299 86 124 22 4085 200 11117 62 30883 10143 35 282 12118 9022 4505 0 02300530 27 49 1028 166 0 0 158 954 0 549 0 0 2 319 306 346 0 203-3 2083 1085 331 114 200 944 4591 12 6417 3850 40 200 5174 1151 1391 206-3C 0 0 5 0 0 2666 15 0 0 0 0 494 84 60483 206-3E 200 257 848 198 126 1174 922 1544 0 4411 907 5 146 949 620 1184 206-3W 72 185 14297 2397 655 0 1999 1853 2 0 0 0 44 0 699 912 2219 LTB 206-4 951 358 146 111 450 1581 2006 17 2990 3667 10 188 420 761 709 59996 BCB 206-5 37 32 1594 94 0 0 571 959 22 0 0 0 0 0 183 99 11431 207-5 825 1270 26731 5053 2199 7 3511 3109 30 15 64 0 77 0 1048 1670 9123 TCB 206-6 581 418 1147 294 42 0 294 561 10 1134 492 0 109 10 467 138 3855 MR 02299950 0 0 0 0 0 1337 136 15708 0 7453 3862 0 0 2058 6452 151 0 202-7 5001 3398 8560 2296 917 220 2950 8270 84 23610 6598 722 487 13198 7887 1811 7616 EVERSRES 576 776 1720 99 0 1364 813 6343 35 8201 383 0 5 3605 6892 1423 0 LMANATEE 393 12 0 42 0 0 141 9891 0 10311 3109 0 20 6637 4470 1631 0 Total 68111 68182 127820 39867 15733 107152 51172 160380 2061 264770 67463 2884 4433 64071 131942 51812 224174 1

1198

0

1989

94 

420 

2234

1396 6484

27 86 0

3366

1072