Final TMDL for Lake Thonotosassa Unionized Ammonia and Lead

TOTAL MAXIMUM DAILY LOAD (TMDL)

For Unionized Ammonia and Lead

In Lake Thonotosassa (WBID 1522B)

(HUC 03100205)

Prepared by:

US EPA Region 4 61 Forsyth Street SW

Atlanta, Georgia 30303

December 2005

Unionized Ammonia and Lead TMDL Lake Thonotosassa (WBID 1522B)

December 2005 Page ii

Under the authority of Section 303(d) of the Clean Water Act, 33 U.S. Code §1251 et.seq., as amended by the Water Quality Act of 1987 (PL 100-4), the U.S Environmental Protection Agency is hereby establishing Total Maximum Daily Loads (TMDLs) for unionized ammonia and lead in the Hillsborough River Basin: Lake Thonotosassa. Subsequent actions must be consistent with this TMDL. _________________/s/_____________________ _ December 20, 2005 James D. Giattina, Director Date Water Management Division


December 2005 Page iii

Executive Summary

Section 303(d)(1)(C) of the Clean Water Act (CWA), 33 U.S.C. §1313(d)(1)(C), and the

U.S. Environmental Protection Agency’s implementing regulation, 40 CFR §130.7(c)(1), require the establishment of Total Maximum Daily Loads (TMDLs) for waters identified by states as not meeting water quality standards under authority of §303(d)(1)(A) of the CWA. Each of these TMDLs are to be established at a level necessary to implement applicable water quality standards with seasonal variations and a margin of safety, accounting for lack of knowledge concerning the relationship between pollutant loading and water quality.

EPA is proposing the Lake Thonotosassa Unionized Ammonia and Lead TMDL included

in this document as required by the 1999 Consent Decree entered in the case of Florida Wildlife Federation, Inc., et al. v. Carol M. Browner, et al., No. 4:98CV356-WS (N.D. Fla., Tallahassee Division, April 22, 1998). The Florida Department of Environmental Protection (FDEP) was the primary author of this TMDL. FDEP could not submit the TMDL to EPA for approval/disapproval action in the allocated timeframe provided in the Consent Decree. However, FDEP is continuing the process of establishing this TMDL to submit to EPA for approval/disapproval action. It is EPA’s expectation that FDEP will establish the TMDL included in this document and submit to EPA in the near future. At this time, EPA proposes the TMDL under V.A.1 of the Consent Decree.


December 2005 Page iv

Table of Contents

Executive Summary ______________________________________ iii Web sites ________________________________________________________ vi

Chapter 1: INTRODUCTION _______________________________1

Purpose of Report ___________________________________________________1

Identification of Waterbody ____________________________________________1

Background_________________________________________________________5 Development of TMDLs ______________________________________________5

Chapter 2: DESCRIPTION OF WATER QUALITY PROBLEM ______________________________________7

Information on Unionized Ammonia_____________________________________7

Information on Lead__________________________________________________9

Chapter 3. DESCRIPTION OF APPLICABLE WATER QUALITY STANDARDS AND TARGETS _________10

Classification of the Waterbody and Criteria Applicable to the TMDL ________10

Chapter 4: ASSESSMENT OF SOURCES__________________11

Types of Sources ___________________________________________________11 Potential Sources of Unionized Ammonia and Lead________________________11 Land Uses and Nonpoint Sources _____________________________________12

Chapter 5: DETERMINATION OF ASSIMILATIVE CAPACITY_____________________________________17

Overall Approach ___________________________________________________17 Data Used in the Determination of the TMDL _____________________________19

Chapter 6: DETERMINATION OF THE TMDL_______________20

Expression and Allocation of the TMDL_________________________________20

Margin of Safety (MOS) ______________________________________________21

Chapter 7: NEXT STEPS: IMPLEMENTATION PLAN DEVELOPMENT AND BEYOND _________________22

References ______________________________________________23


December 2005 Page v

Appendices______________________________________________24

Appendix A: Background Information on Federal and State Stormwater Programs__________________________________________________________24

Appendix B: Summary of Unionized Ammonia Data for WBID 1522B Lake Thonotosassa ______________________________________________________24

List of Tables

Table 1.1. WBIDs in the Lake Thonotosassa Drainage Basin __________________2 Table 2.1. Verified Impaired Segments in Lake Thonotosassa _________________7 Table 2.2. Summary of Unionized Ammonia Data ___________________________7 Table 4.1. Classification of Land Use Categories (SWFWMD, 1999) in the

Thonotosassa Watershed____________________________________13 Table 6.1. TMDL Components for Lake Thonotosassa ______________________21

List of Figures

Figure 1.1: Location of Lake Thonotosassa (WBID 1522B) in the Hillsborough

River Basin _______________________________________________3 Figure 1.2: Lake Thonotosassa and Baker Creek HCEPC Water Quality Stations _4 Figure 2.1: Unionized Ammonia in Lake Thonotosassa ______________________8 Figure 4.1. Census Information in the Thonotosassa Watershed______________14 Figure 4.2. Spatial Distribution of Land Use Types in the Thonotosassa

Watershed_______________________________________________15 Figure 5.1: Lake Thonotosassa Temperature Data _________________________17 Figure 5.2: Lake Thonotosassa pH Data __________________________________18 Figure 5.3: Lake Thonotosassa Total Nitrogen_____________________________18

Draft Unionized Ammonia and Lead TMDL Lake Thonotosassa (WBID 1522B)

December 2005 Page vi

Web sites

Florida Department of Environmental Protection, Bureau of Watershed Management

TMDL Program http://www.dep.state.fl.us/water/tmdl/index.htm Identification of Impaired Surface Waters Rule http://www.dep.state.fl.us/water/tmdl/docs/AmendedIWR.pdf STORET Program http://www.dep.state.fl.us/water/storet/index.htm 2000 305(b) Report http://www.dep.state.fl.us/water/305b/index.htm Criteria for Surface Water Quality Classifications http://www/dep.state.fl.us/legal/legaldocuments/rules/ruleslistnum.htm Basin Status Report for the Hillsbourough River Basin http://www.dep.state.fl.us/water/tmdl/stat_rep.htm Water Quality Assessment Report for the Hillsborough River Basin http://www.dep.state.fl.us/water/tmdl/stat_rep.htm Allocation Technical Advisory Committee (ATAC) Report http://www.dep.state.fl.us/water/tmdl/docs/Allocation.pdf

U.S. Environmental Protection Agency, National STORET Program

http://www.epa.gov/storet/

http://www.dep.state.fl.us/water/tmdl/index.htm

http://www.dep.state.fl.us/water/tmdl/docs/AmendedIWR.pdf

http://www.dep.state.fl.us/water/storet/index.htm

http://www.dep.state.fl.us/water/305b/index.htm

http://www/dep.state.fl.us/legal/legaldocuments/rules/ruleslistnum.htm

http://www.dep.state.fl.us/water/tmdl/stat_rep.htm

http://www.dep.state.fl.us/water/tmdl/stat_rep.htm

http://www.dep.state.fl.us/water/tmdl/docs/Allocation.pdf

http://www.epa.gov/storet/


December 2005 Page 1

Chapter 1: INTRODUCTION

Purpose of Report

This report presents the Total Maximum Daily Load (TMDL) for Unionized Ammonia for Lake Thonotosassa located in the Hillsborough River Basin. The lake was verified as impaired for unionized ammonia based on the methodology in Chapter 62-303, Florida Administrative Code, (Identification of Impaired Surface Waters, which is commonly referred to as the Impaired Waters Rule or IWR). Available data indicate that 21 percent of the samples exceeded the Class III unionized ammonia criteria during the verification period (January 1, 1996 – June 30, 2003) and was included on the Verified List of impaired waters for the Hillsborough River Basin that was adopted by Secretarial Order in May 2004. The TMDL establishes the allowable in-lake nutrient concentration and loading to Lake Thonotosassa that would restore the waterbody so that it meets the applicable water quality criterion for unionized ammonia.

The TMDL for Lead was developed because there were three samples taken at the mouth of Flint Creek, the discharge from Lake Thonotosassa, which exceeded the chronic water quality criteria for Lead. The hardness based Lead water quality criterion for these samples is 2.70 ppb with a hardness value of 88 mg/l. The TMDL is expressed as a percent reduction based upon the mean of the exceedances relative to the water quality criterion. A 60 percent reduction in Lead discharges to the Lake would be required based upon this analysis.

Identification of Waterbody

Lake Thonotosassa is located in the Hillsborough River Basin, and has a 32,000 square-mile (mi2) drainage area, with roughly 9 square miles falling within urbanized portions of Plant City at the eastern edge of the basin. (Figure 1.1). The lake is 2.5 km long and 1.5 km wide at its widest point, and has an average depth of about 2.5-m. Major centers of population within the basin include Plant City (29,915), on the east side of the basin and the City of Tama (315,140), just west of the basin. The Lake and its tributaries are Class III water bodies, whose designated uses under Rule 62-302.400, Florida Administrative Code (F.A.C.), include human recreation and the “propagation and maintenance of a healthy, well-balanced population of fish and wildlife.” Additional information about the Hillsborough River Basin hydrology and geology are available in the Tampa Bay Tributaries Basin Status Report (Florida Department of Environmental Protection [FDEP], 2002).

For assessment purposes, the Department has divided the Hillsborough River Basin into

water assessment polygons with a unique waterbody identification (WBID) number for each watershed or stream reach. Lake Thonotosassa has been given WBID number 1522B, as shown in Figure 1.1, and this TMDL addresses pollutant loadings for WBIDs located in the lakes drainage area, as listed in Table 1.1.



Table 1.1. WBIDs in the Lake Thonotosassa Drainage Basin

WBIDs in the Hillsborough River Drainage Basin

1522B Lake Thonotosassa 1544 Mill Creek 1547 Seffner Canal

1547A Lake Valrico 1547B Lake Weeks - Open Water 1565 Moore Lake

1547C Moore Lake Drain 1561 Sparkman Branch 1542 Pemberton Creek 1544 Baker Creek Tributary

1522C Baker Creek



Figure 1.1: Location of Lake Thonotosassa (WBID 1522B) in the Hillsborough River Basin

%

%

Plant City

Temple Terrace

Tampa

Hillsborough River

Flint Creek

1522B

Map prepared May 24, 2004 by the Bureau of Watershed Management, Division of Water

Resource Management. This map is a representation of ground conditions and is not

intended for delineations of analysis of the features shown. For more information of copies, contact

Aaron Lassiter at (850) 245.8462, or [email protected].

N

2 0 2 4 Miles

Waterbody IDsWaterCity Limits Water Lines

Legend

%

%

Plant City

Temple Terrace

Tampa

Hillsborough River

Flint Creek

1522B





N

2 0 2 4 Miles

Waterbody IDsWaterCity Limits Water Lines

Legend



Figure 1.2: Lake Thonotosassa and Baker Creek HCEPC Water Quality Stations

#S

#S

#S

Flint Creek

1522B

Baker Creek

21FLHILL118

21FLHILL135

21FLHILL107

Hillsborough River





N

Legend 0.6 0 0.6 1.2 Miles

WBID Boundaries

Thonotosassa Basin

Lakes

Water

Major Rivers

#S Storet Stations



Background

This report was developed as part of the Florida Department of Environmental Protection’s (Department) watershed management approach for restoring and protecting state waters and addressing TMDL Program requirements. The watershed approach, which is implemented using a cyclical management process that rotates through the state’s fifty-two river basins over a five-year cycle, provides a framework for implementing the requirements of the 1972 federal Clean Water Act and the 1999 Florida Watershed Restoration Act (Chapter 99-223, Laws of Florida).

A TMDL represents the maximum amount of a given pollutant that a waterbody can assimilate and still meet water quality standards, including its applicable water quality criteria and its designated uses. TMDLs are developed for waterbodies that are verified as not meeting their water quality standards. TMDLs provide important water quality restoration goals that will guide restoration activities. This TMDL Report will be followed by the development and implementation of a Basin Management Action Plan, or BMAP, to reduce the concentration of Unionized Ammonia that caused the verified impairment of Lake Thonotosassa. These activities will depend heavily on the active participation of the Southwest Florida Water Management District (SWFWMD), local governments, businesses, and other stakeholders. The Department will work with these organizations and individuals to undertake or continue reductions in the discharge of pollutants and achieve the established TMDLs for impaired waterbodies.

Development of TMDLs

Development of the unionized ammonia TMDL is dependent on the restoration efforts set forth in the Southwest Florida Water Management Districts Lake Thonotosassa Surface Water Improvement and Management (SWIM) plan. Work performed under the SWIM plan focuses on the implementation of the water quality improvement projects designed to treat non-point source pollution prior to entering the lake as well as improved regulation of point source discharges. The water quality target proposed by SWIM for lake restoration is a TSI of 60 (moderately eutrophic), which is consistent with historical conditions as supported by analyses of sediment cores taken from the lake bottom. A TSI value of 60 would provide adequate water quality to support the lake’s native wildlife populations and desirable recreational uses, reduce nutrient loading (and resulting blue-green algae blooms) in the City of Tampa drinking water reservoir, and improve water quality in the Hillsborough River and, ultimately, Tampa Bay.

To achieve an annual TSI of 60, target concentrations of total phosphorus and total nitrogen are 0.07 mg/L and1.2 mg/L, respectively. The corresponding average annual TP and TN loads are 3,400 kg/yr and 65,600 kg/yr, respectively. To meet the total phosphorus load allocation, a reduction of approximately 20,500 kg/yr of phosphorus from nonpoint sources will be needed. Due to lack of complete information for the existing total nitrogen load estimate, the SWIM does not report a TN load reduction goal. Load estimates were obtained using the EUTROMOD model.



The TMDL for unionized ammonia will be implemented based on the total nitrogen

concentration Pollution Load Reduction Goal (PLRG), as set forth by the Southwest Florida Water Management district. Based on the ratio of ammonia to total nitrogen (0.019 mg/L), and a worse case scenario (maximum temperature (35°C), and maximum pH of 10.8), the total nitrogen concentration would provide the necessary reductions to achieve the unionized ammonia criterion of 0.02 mg/L. Achieving needed reductions in nutrient concentrations and loadings will require continued coordination between state and federal regulatory agencies, the water management district, local governments (City of Plant City, Hillsborough County), the Tampa Port Authority, federal and state agricultural agencies, local agricultural operations, private property owners, and other private-sector participants. The continued implementation of water quality improvement and habitat restoration projects as well as strict regulation of existing (and future) point source discharges are critical to the long-term health of the lake and downstream water bodies.

The revised Lake Thonotosassa SWIM Plan (February 2003) outlines strategies to improve

water quality and habitat within the lake and its watershed, while providing details for projects that implement these strategies. In addition to improving water quality and habitat within Lake Thonotosassa, several of these projects will be used to refine the District and County’s understanding of the lake system. The Lake Thonotosassa SWIM Plan serves as the guidance document for coordinating the efforts of the District, Hillsborough County and the State of Florida to restore and protect Lake Thonotosassa. The lead TMDL addresses the use impairment determined by using EPA’s toxic pollutant assessment methodology that considers any waterbody impaired if two or more sample events taken in a three-year period exceed the chronic water quality criterion. This stringent assessment methodology is designed to protect the aquatic community from exposure to no more than one chronic toxic event in a three-year period. The potential sources of lead in the watershed are the stormwater runoff from MS4 areas, stormwater discharges from industrial sites documented in the SWIM Plan, and legacy pollutants from the use of leaded gasoline that may be present in the Lake sediments. The implementation of this TMDL should focus on monitoring potential sources and sampling the lake sediment for lead and hardness. It is possible that the lead exceedances are principally due to re-suspension of contaminated lake sediments under severe weather conditions.



Chapter 2: DESCRIPTION OF WATER QUALITY PROBLEM

Information on Unionized Ammonia

Under Section 303(d) of the Federal Clean Water Act, states are required to submit to the EPA lists of waters that are not fully meeting their applicable water quality standards (designated uses). The Department has developed such lists, commonly referred to as 303(d) lists, since 1992. However, the 1999 Florida Watershed Restoration Act (FWRA, Section 403.067, Florida Statutes [F.S.]) stated that all previous Florida 303(d) lists were for planning purposes only and directed the Department to develop, and adopt by rule, a new science-based methodology to identify impaired waters. After a long rule-making process, the Environmental Regulation Commission adopted the new methodology as Rule 62-303, F.A.C. (Identification of Impaired Surface Waters Rule, or IWR), in April 2001.

The Department has subsequently used the IWR to assess water quality impairments in

Lake Thonotosassa and has verified the impairments listed in Table 2.1. The impairments to WBID 1522B are Nutrients (TSI), and Unionized Ammonia. This TMDL specifically covers the Unionized Ammonia impairment. Table 2.2 provides summary statistics of unionized ammonia data for the verification period in Lake Thonotosassa. Figure 2.1 displays the unionized ammonia data collected in the verified period (1996-2002).

Table 2.1. Verified Impaired Segments in Lake Thonotosassa

WBID Water Segment Name Parameters Assessed

Using the Impaired Waters Rule (IWR)

Priority for TMDL Development

Projected Year For TMDL Development

1522B LAKE THONOTOSASSA Nutrients (TSI) Medium 2008

1522B LAKE THONOTOSASSA Unionized Ammonia High 2003

Table 2.2. Summary of Unionized Ammonia Data

Water Quality Station Number of Samples Mean Median Max 21FLHILL118 188 0.0119 0.0069 0.1693 21FLHILL135 194 0.0133 0.0073 0.0650



Figure 2.1: Unionized Ammonia in Lake Thonotosassa

A number of water quality problems have been identified that indicate an imbalance in flora

and fauna in Lake Thonotosassa. These problems include the following: an increase of undesirable blooms of algae, loss of desirable rooted aquatic plants and other adverse ecological changes. Following an extremely large fish kill that occurred in the lake during 1969, efforts to improve treatment of domestic and industrial wastewater were initiated throughout the watershed. Since the early 1900’s the shift from eutrophic (TSI=60) to hypereutrophic (TSI>70) water quality conditions in Lake Thonotosassa occurred as a result of increasing nutrient loadings from a combination of domestic wastewater, industrial effluents, and agricultural and urban stormwater runoff.

Although improvements in total phosphorous concentrations have occurred since 1992 (and prior years), monitoring data collected by the Environmental Protection Commission (EPC), indicate that overall water quality in Lake Thonotosassa has remained unacceptably low during the ten year period of 1991-2000. For example, annual average chlorophyll-a concentrations that provide a measure of algal biomass and degree of lake eutrophication have ranged from 62 µg/L to 179 µg/L during this time period. The median value for chlorophyll-a in Florida Lakes is 18.5 mg/L (Friedmann and Hand 1989). In addition, EPC data also show a substantial increase in chlorophyll-a from 1998-2000. This apparent increasing trend is likely due to an ongoing

Lake Thonotosassa Unionized Ammonia

0

0.04

0.08

0.12

0.16

0.2

10/2.

..

5/15/9

6

12/1/

96

6/19/9

71/5

/98

7/24/9

82/9

/99

Date

mg/

L

21FLHILL118

21FLHILL135

UNNH4 Criterion



severe drought that began in 1998 and has continued through 2001. It is believed that a substantial lack of rainfall over this time period (especially during the historic dry season, March – May) lead to reduced flushing of the lake and stagnant conditions (SWFWMD February 2003). These conditions, combined with an abundance of existing in-lake nutrients and organic sediment, could have promoted an increase in chlorophyll-a over this three-year period. It is important to note, because nutrient supplies are often in excess of the algae populations’ ability to fully utilize them, other environmental factors, such as micronutrients, light, temperature, and wind can become the driving forces behind algal productivity in eutrophic and hypereutrophic lakes (Dynamac Corp. 1992).

Information on Lead

EPA reviewed the FDEP request to delist Lake Thonotosassa for Lead and determined that the available data documented that three exceedances of the lead criterion occurred in 2002. More than one exceedance in three years is sufficient to determine that there is a water quality use impairment for a toxic pollutant such as lead. The three sample events that exceeded the water quality criterion taken in Lake Thonotosassa at the mouth of the Flint Creek in 2002 are as follows: 1) 1/16/02- 5 ppb at 90.5 mg/l hardness; 2) 3/20/02- 10 ppb at 88 mg/l hardness; and 3) 5/15/02- 5 ppb at 88 mg/l hardness. All other samples were at or below the detection level or no hardness data was available to calculate the water quality criterion. These exceedances of the lead criterion could adversely impact the health of the lake’s aquatic community.



Chapter 3. DESCRIPTION OF APPLICABLE WATER QUALITY STANDARDS AND TARGETS

Classification of the Waterbody and Criteria Applicable to the TMDL

Florida’s surface waters are protected for five designated use classifications, as follows: Class I Potable water supplies Class II Shellfish propagation or harvesting Class III Recreation, propagation, and maintenance of a healthy, well-

balanced population of fish and wildlife Class IV Agricultural water supplies Class V Navigation, utility, and industrial use (there are no state

waters currently in this class)

Lake Thonotosassa is a Class III waterbody, with a designated use of recreation, propagation, and maintenance of a healthy, well-balanced population of fish and wildlife. The Class III water quality criterion for unionized ammonia is ≤ 0.02 mg/L as NH3. The Department determined that the unionized ammonia criterion should be achieved if the SWIM Plan Total Nitrogen concentration target of 1.2 mg/L is met. The methodology used for making this determination is described in Chapter 5. The water quality criterion for lead is defined by the State of Florida as “Less than or equal to a value of e(1.273[lnH]-4.705) micrograms per liter, where ‘lnH’ means the natural logarithm of total hardness expressed as milligram/L of CaCO3. For metals criteria involving equations with hardness, the hardness shall be set at 25 mg/L if actual hardness is less than 25 and set at 400 mg/L if actual hardness is greater than 400 mg/L.” (FAC 62-302.530 (40)). For Lake Thonotosassa the lead water quality criterion at the lowest hardness value of 88 mg/l is 2.70 ppb.



Chapter 4: ASSESSMENT OF SOURCES

Types of Sources

An important part of the TMDL analysis is the identification of pollutant source categories, source subcategories, or individual sources of nutrients in Lake Thonotosassa and the amount of pollutant loading contributed by each of these sources. Sources are broadly classified as either “point sources” or “nonpoint sources.” Historically, the term point sources has meant discharges to surface waters that typically have a continuous flow via a discernable, confined, and discrete conveyance, such as a pipe. Domestic and industrial wastewater treatment facilities (WWTFs) are examples of traditional point sources. In contrast, the term “nonpoint sources” was used to describe intermittent, rainfall driven, diffuse sources of pollution associated with everyday human activities, including runoff from urban land uses, agriculture, silviculture, and mining; discharges from failing septic systems; and atmospheric deposition.

However, the 1987 amendments to the Clean Water Act redefined certain nonpoint sources

of pollution as point sources subject to regulation under the EPA’s National Pollutant Discharge Elimination Program (NPDES). These nonpoint sources included certain urban stormwater discharges, including those from local government master drainage systems, construction sites over five acres, and a wide variety of industries (see Appendix A for background information on the federal and state stormwater programs).

To be consistent with Clean Water Act definitions, the term “point source” will be used to

describe traditional point sources (such as domestic and industrial wastewater discharges) AND stormwater systems requiring an NPDES stormwater permit when allocating pollutant load reductions required by a TMDL. However, the methodologies used to estimate nonpoint source loads do not distinguish between NPDES stormwater discharges and non-NPDES stormwater discharges, and as such, this source assessment section does not make any distinction between the two types of stormwater.

Potential Sources of Unionized Ammonia and Lead

Point Sources There are no significant NPDES permitted point sources that discharge into the Lake

Thonotosassa drainage area. Based on the priority rankings established through the nonpoint source load assessments, the SWIM document identifies a number of proposed initiatives, programs and projects to determine load allocations (LAs). This includes surface water and groundwater monitoring and atmospheric deposition monitoring to refine existing nutrient loading estimates, new modeling to account for nitrogen-fixing taxa, and future land use effects on loadings. The following NPDES facility was not included in the loading calculations: Crystals International, FL0037389, discharges heated but uncontaminated cooling water into the Westside Canal and thence to Pemberton Creek. Located approximately 13.5 miles Southeast of Lake Thonotosassa, this discharge is not a significant source of nutrients. There are



approximately 50 small wastewater treatment plants in the area of the watershed, but they are not authorized to discharge to surface waters. Permitted dischargers to groundwater include three dairy operations, two phosphate companies, five landfills, and three injection wells. These dischargers are listed in the June 1996 Surface Water Improvement and Management (SWIM) Plan for Lake Thonotosassa. Two sites selected for the National Priorities (“Superfund”) List by the U.S. EPA are Schuylkill Metals and Taylor Road Landfill. Approximately 400 Surface Water Management permits (listed in the SWIM document) have been issued by the SWFWMD for stormwater discharge in the Lake Thonotosassa watershed and its immediate vicinity.

Municipal Separate Storm Sewer System Permittees Phase 1 or Phase 2 MS4s. Within the Hillsborough River Basin, the stormwater collection

systems owned and operated by Hillsborough County, City of Plant City, and the Department of Transportation in Plant City and west to Tampa, are covered by an NPDES municipal separate storm sewer system (MS4) permit.

Land Uses and Nonpoint Sources

Additional nitrogen loadings to Lake Thonotosassa that contribute to unionized ammonia exceedances are generated from nonpoint sources in the basin. Nonpoint sources addressed in this study primarily include loadings from surface runoff, precipitation directly on the surface of Lake Thonotosassa, and the contribution from leaking septic tanks.

Land Uses The spatial distribution and acreage of different land use categories were identified using

the 1999 SWFWMD land use coverage (scale 1:40,000) contained in the Department’s geographic information system (GIS) library. The Thonotosassa watershed drains about 71 square miles into Lake Thonotosassa. Figure 4.2 provides information on the spatial distribution of different land use types in the Thonotosassa watershed.

Areas of different land use categories in the Thonotosassa watershed were obtained by

aggregating GIS land use coverage based on the simplified Level 1 code. These areas are listed in Table 4.1. The table also shows percent distributions of each land use category in the watershed. According to Table 4.1, the dominant land use category in the Thonotosassa watershed is agriculture, which accounts for about 36 percent of the total area of the watershed. Low-density residential accounts for another 19 percent of the total watershed area. The areas occupied by nonhuman land uses account for about 17 percent of the total watershed area. The largest human land use category is agriculture, which covers about 36% of the watershed. The second largest human land use category is low-density residential, followed by water/wetlands, urban open and medium-density residential. The remaining percentage of the watershed is occupied by utilities, followed by forests/rural and open areas. In total the area of human land use categories cover about 83 percent of the total area of the Thonotosassa watershed.



Table 4.1. Classification of Land Use Categories (SWFWMD, 1999) in the Thonotosassa

Watershed

Code Landuse AREA (ACRES) PERCENT 1000 Urban Open 5574.3 9.72 1100 Low-density residential 10977.0 19.14 1200 Medium-density residential 4649.0 8.11 1300 High-density residential 2069.3 3.61 2000 Agriculture 20572.5 35.87 3000 Rangeland 193.0 0.34 4000 Forest/rural open 2504.6 4.37

5000/6000 Water/Wetlands 7061.7 12.31 7000 Disturbed Land 215.5 0.38 8000 Utilities 3539.0 6.17

TOTAL 57355.9 100.00

Population According to the U.S Census Bureau, the population density in and around WBID 1522B

in the year 2000 was at or less than 0-458 people per square mile (10 person/mi2 is the minimum used by the Census Bureau) (Figure 4.1). The Bureau reports that, in Hillsborough County, which includes (but is not exclusive to) WBID 1522Bthe total population for 2000 was 998,948 with 425,962 housing units. For all of Hillsborough County, the Bureau reported a housing density of 8-5212 houses per square mile.



Figure 4.1. Census Information in the Thonotosassa Watershed



1522B

1443BHillsborough River

Lake Thonotosassa

Thonotosassa Drainage Basin Landuse

0.7 0 0.7 1.4 2.1 Miles

Water BodiesWater LinesMajor Rivers

Urban and Built-UpAgricultureRangelandUpland ForestsWaterWetlandsBarren LandRoads and Highways

Legend

N

Map prepared May 24, 2004 by the Bureau of Watershed Management, Division of W ater Resource Management. This map is a representation of ground conditions and is not intended for delineations of analysis of the features shown. For more information of copies, contact Aaron Lassiter at (850) 245.8462, or [email protected].

Figure 4.2. Spatial Distribution of Land Use Types in the Thonotosassa Watershed

Modeling of Nonpoint Sources The SWFWMD established PLRGs for TP and TN loads to achieve a target annual average TSI of 60. Since the focus of this TMDL is TN, the following describes the development of the TN loading. The SWFWMD used the EUTROMOD model to obtain initial estimates of target TN loadings that would be consistent for a lake exhibiting the hydraulic loadings and detention times observed in Lake Thonotosassa to meet the TN concentration target of 1.2 mg/L. The model estimates loadings in Lake Thonotosassa to be 65,596 kg/yr as the average annual nitrogen load (mass of nitrogen entering the lake (kg/yr)) that would be consistent with an in-lake TN concentration of 1.2 mg/L and TSI avg =60 (SWFWMD, 2003). Because a significant proportion of the total nitrogen load may be entering the lake through routes other than Baker Creek, however, the loading targets should be interpreted as applying to all inputs rather than to the creek alone (SWFWMD, 2003).



TN concentrations measured at the mouth of Baker Creek showed a generally declining

trend over the 1985-1994 period (which is the period used to develop the load target), but a flat or slightly upward trend within the lake. The differences observed between the two trends suggest that other (unmeasured) sources, rather than the measured inputs entering via Baker Creek, may play a predominant role driving temporal TN trends in the lake water column.

Potential sources of unmeasured TN loads could conceivably be external (e.g. cattle

operations, citrus groves, or septic systems located on the lake shore), internal (e.g. N fixation; sediment release), or a combination of the two. More complete information on the identities and magnitudes of those potential sources is needed, because absence of complete information on TN inputs may hinder efforts to develop appropriate load reduction goals. The potential sources of lead in the watershed are the stormwater runoff from MS4 areas, stormwater discharges from industrial sites documented in the SWIM Plan, and legacy pollutants from the use of leaded gasoline that may be present in the Lake sediments. The implementation of this TMDL should focus on monitoring potential sources and sampling the lake sediment for lead and hardness. It is possible that the lead exceedances are principally due to re-suspension of contaminated lake sediments under severe weather conditions.



Chapter 5: DETERMINATION OF ASSIMILATIVE CAPACITY

Overall Approach

Lake Thonotosassa was placed on the Verified List of impaired waters for Unionized Ammonia following the procedures established in Rule 62-303, FAC. The mean concentration of TN for the verified period is 2.56 mg/L. The annual average concentration of Total Nitrogen in the Lake once the TMDL and PLRG are achieved has been calculated as 1.2 mg/L. The current ratio between ammonia and TN is 0.016 (based on the average ammonia/TN ratio during 1996-2002). Based on this ratio, the annual average total ammonia concentration in the Lake after the TMDL is achieved is calculated as (1.2 mg/L * 0.016) 0.019 mg/L. This value is below the unionized ammonia criterion of 0.02 mg/L specified in Rule 62-302.530, FAC. This indicates that under the PLRG TN concentration target, the unionized ammonia concentration is expected to meet water quality standards.

For the lead impairment, the three sample values that exceeded the water quality criterion

of 2.70 ppb at 88 mg/l hardness were averaged and a percent reduction in lead was calculated to achieve the water quality criterion. The mean exceedance value is 6.67 ppb and a 60% reduction is necessary to achieve the 2.70 ppb water quality criterion for lead.

Figure 5.1: Lake Thonotosassa Temperature Data

Lake Thonotosassa HCEPC Long Term Stations Temperature

05

1015

20

25

30

3540

6/15/1

994

10/28

/...

3/11/1

997

7/24/1

998

12/6/

1999

4/19/2

001

9/1/20

02

1/14/2

004

Date

Tem

p (°

C)

21FLHILL118

21FLHILL135



Figure 5.2: Lake Thonotosassa pH Data

Figure 5.3: Lake Thonotosassa Total Nitrogen

Lake Thonotosassa Total Nitrogen

0

1

2

3

4

5

6

7

8

9

10

6/15/1

994

10/28

/...

3/11/1

997

7/24/1

998

12/6/

1999

4/19/2

001

9/1/20

02

1/14/2

004

Date

TN (m

g/L)

Total Nitrogen

Lake Thonotosassa HCEPC Long Term Stations pH

0

2

4

6

8

10

12

6/15/1

994

10/28

/...

3/11/1

997

7/24/1

998

12/6/

1999

4/19/2

001

9/1/20

02

1/14/2

004

Date

pH

21FLHILL11821FLHILL135



Data Used in the Determination of the TMDL

The SWIM plan for Lake Thonotosassa is the basis for the unionized ammonia TMDL. The SWIM plan requires a reduction of total nitrogen of 65,596 kg/yr in order to sufficiently reduce the algal production and total nitrogen concentration to achieve a TSI value of 60. The presumption is that by controlling excessive algal production in high temperature waters Figure 5.1, the high pH values, greater than 8, produced by this algal production, Figure 5.2 , would be reduced sufficiently to reduce the toxic effect of unionized ammonia. The significant total nitrogen load reduction required by the SWIM plan also will result in a reduction of unionized ammonia. As seen in Figure 5.3, the total nitrogen concentrations in the lake are well above the 1.2 mg/l target concentration. Documentation of the unionized ammonia data is presented in Appendix B.



Chapter 6: DETERMINATION OF THE TMDL

Expression and Allocation of the TMDL

The objective of a TMDL is to provide a basis for allocating acceptable loads among all of the known pollutant sources in a watershed so that appropriate control measures can be implemented and water quality standards achieved. A TMDL is expressed as the sum of all point source loads (Waste Load Allocations, or WLAs), nonpoint source loads (Load Allocations, or LAs), and an appropriate margin of safety (MOS) that takes into account any uncertainty concerning the relationship between effluent limitations and water quality:

TMDL = ∑ WLAs + ∑ LAs + MOS As discussed earlier, the WLA is broken out into separate subcategories for wastewater

discharges and stormwater discharges regulated under the NPDES Program: TMDL ≅ ∑ WLAswastewater + ∑ WLAsNPDES Stormwater + ∑ LAs + MOS It should be noted that the various components of the revised TMDL equation may not sum

up to the value of the TMDL because a) the WLA for NPDES stormwater is typically based on the percent reduction needed for nonpoint sources and is accounted for within the LA, and b) TMDL components can be expressed in different terms (for example, the WLA for stormwater is typically expressed as a percent reduction, and the WLA for wastewater is typically expressed as mass per day).

WLAs for stormwater discharges are typically expressed as “percent reduction” because it

is very difficult to quantify the loads from MS4s (given the numerous discharge points) and to distinguish loads from MS4s from other nonpoint sources (given the nature of stormwater transport). The permitting of stormwater discharges also differs from the permitting of most wastewater point sources. Because stormwater discharges cannot be centrally collected, monitored, and treated, they are not subject to the same types of effluent limitations as wastewater facilities, and instead are required to meet a performance standard of providing treatment to the “maximum extent practical” through the implementation of BMPs.

This approach is consistent with federal regulations (40 CFR § 130.2[I]), which state that

TMDLs can be expressed in terms of mass per time (e.g., pounds per day), toxicity, or other appropriate measure. TMDLs for Lake Thonotosassa are expressed in terms of kg/year for total nitrogen and as a percent reduction in concentration for lead and represent the maximum annual pollutant loads the lake can assimilate and maintain the water quality criteria (Table 6.1).

While neither the WLA nor the LA are broken into individual sources or source categories,

the division of the available assimilative capacity between the WLA and LA was determined using information about individual sources and source categories. The allocation methodology followed the recommendations in the 2001 Report to the Governor and Legislature on the Allocation of Total Maximum Daily Loads (FDEP, February 2001). Under this approach, initial



reductions for the lake were targeted at nonpoint source loads, assuming the implementation of BMPs. As BMP implementation alone did not result in sufficient reductions, all anthropogenic sources, including the upstream load, were reduced by the same percentage until the assimilative capacity was met, with the exception that prior treatment or prior commitments in treatment improvements was taken into account for individual point sources. Allocation calculations were conducted using an Excel spreadsheet, and table versions of the spreadsheets used to allocate loadings. (Interested parties can request an electronic copy of the spreadsheet if they would like to see spreadsheet formulas).

Table 6.1. TMDL Components for Lake Thonotosassa

WBIDs Parameter TMDL

(kg/year) WLA1

(kg/year) LA

(kg/year) MOS

1522B Total Nitrogen 65,596 32,798 32,798 Implicit

1522B Lead 60% reduction

60% reduction

60% reduction Implicit

The combined WLA is designed to allow flexibility so that reductions from one discharger

can be shifted to another as long as the net reduction reaches the TMDL. It should be noted, however, that the objective of the TMDL Program is to eventually allocate loads among all of the known pollutant sources throughout the watershed, so that appropriate control measures can be implemented and water quality standards achieved. As such, a more detailed allocation of the TMDL will be determined as part of the development of the implementation plan for this TMDL (the Basin Management Action Plan, or BMAP). Individual WLAs will take into account the existing treatment levels and economic feasibility and location of dischargers, and individual WLAs will be encoded in the facility’s NPDES permit. Reductions required to meet allocations to nonpoint sources will be voluntary, but will be aggressively pursued by multiagency and stakeholder efforts.

Margin of Safety (MOS)

The unionized ammonia concentration was calculated using the worst-case temperature and pH observed in the verified period to insure compliance of the state criterion of 0.02 mg/L.

For lead, a conservative approach of calculating the percent reduction to achieve the water

quality criterion of 2.70 was used. Only values that exceeded the criteria were used to calculate the percent reduction, 3 of 16 samples exceeded the detection limit reported as 3-4 ppb.

1 As described in Section 6.2, this WLA includes a percent reduction in current loading from sources covered by the NPDES Stormwater Program.



Chapter 7: NEXT STEPS: IMPLEMENTATION PLAN DEVELOPMENT AND BEYOND

Following the adoption of this TMDL by rule, the next step in the TMDL process is to

develop an implementation plan for the TMDL, which will be a component of the Basin Management Action Plan (BMAP) for the Hillsborough River Basin. This document will be developed over the next year in cooperation with local stakeholders and will attempt to reach consensus on more detailed allocations and on how load reductions will be accomplished. The BMAP will include the following:

• Appropriate allocations among the affected parties,

• A description of the load reduction activities to be undertaken,

• Timetables for project implementation and completion,

• Funding mechanisms that may be utilized,

• Any applicable signed agreement,

• Local ordinances defining actions to be taken or prohibited,

• Local water quality standards, permits, or load limitation agreements, and

• Monitoring and follow-up measures.



References

Florida Administrative Code, Chapter 62-302, Surface Water Quality Standards.

Florida Administrative Code, Chapter 62-303, Identification of Impaired Surface Waters.

Florida Department of Environmental Protection, 2003. Basin Status Report: Tampa Bay Tributaries. Bureau of Watershed Management.

Florida Department of Environmental Protection. 2001. A Report to the Governor and the Legislature on the Allocation of Total Maximum Daily Loads in Florida. Tallahassee, Florida: Bureau of Watershed Management.

Friedemann, M. and J. Hand, 1989. Typical Water Quality Values for Florida’s Lakes, Streams and Estuaries. Florida Department of Environmental Protection. Tallahassee, Florida.

Southwest Florida Water Management District, 2003. Lake Thonotosassa Surface Water Improvement and Management (SWIM) Plan.

Appendices

Appendix A: Background Information on Federal and State Stormwater Programs

In 1982, Florida became the first state in the country to implement statewide regulations to address the issue of nonpoint source pollution by requiring new development and redevelopment to treat stormwater before it is discharged. The Stormwater Rule, as authorized in Chapter 403, F.S., was established as a technology-based program that relies on the implementation of BMPs that are designed to achieve a specific level of treatment (i.e., performance standards) as set forth in Rule 62-40, F.A.C.

The rule requires the state’s water management districts (WMDs) to establish stormwater

pollutant load reduction goals (PLRGs) and adopt them as part of a SWIM plan, other watershed plan, or rule. Stormwater PLRGs are a major component of the load allocation part of a TMDL. To date, stormwater PLRGs have been established for Tampa Bay, Lake Thonotosassa, the Winter Haven Chain of Lakes, the Everglades, Lake Okeechobee, and Lake Apopka. No PLRG has been developed for Newnans Lake at the time this study was conducted.

In 1987, the U.S. Congress established Section 402(p) as part of the federal Clean Water

Act Reauthorization. This section of the law amended the scope of the federal NPDES stormwater permitting program to designate certain stormwater discharges as “point sources” of pollution. These stormwater discharges include certain discharges that are associated with industrial activities designated by specific Standard Industrial Classification (SIC) codes, construction sites disturbing five or more acres of land, and master drainage systems of local governments with a population above 100,000, which are better known as municipal separate storm sewer systems (MS4s). However, because the master drainage systems of most local governments in Florida are interconnected, the EPA has implemented Phase 1 of the MS4 permitting program on a countywide basis, which brings in all cities (incorporated areas), Chapter 298 urban water control districts, and the Florida Department of Transportation throughout the fifteen counties meeting the population criteria.

An important difference between the federal and state stormwater permitting programs is

that the federal program covers both new and existing discharges, while the state program focuses on new discharges. Additionally, Phase 2 of the NPDES Program will expand the need for these permits to construction sites between one and five acres, and to local governments with as few as 10,000 people. These revised rules require that these additional activities obtain permits by 2003. While these urban stormwater discharges are now technically referred to as “point sources” for the purpose of regulation, they are still diffuse sources of pollution that cannot be easily collected and treated by a central treatment facility similar to other point sources of pollution, such as domestic and industrial wastewater discharges. The Department recently accepted delegation from the EPA for the stormwater part of the NPDES Program. It should be noted that most MS4 permits issued in Florida include a re-opener clause that allows permit revisions to implement TMDLs once they are formally adopted by rule.

Appendix B: Summary of Unionized Ammonia Data for WBID 1522B Lake Thonotosassa

WBID Station Date Parameter Result

1522B 21FLHILL118 1/24/96 UNNH4 0.00334 1522B 21FLHILL118 1/24/96 UNNH4 0.00406 1522B 21FLHILL118 2/21/96 UNNH4 0.00315 1522B 21FLHILL118 2/21/96 UNNH4 0.00383 1522B 21FLHILL118 4/17/96 UNNH4 0.00274 1522B 21FLHILL118 4/17/96 UNNH4 0.00333 1522B 21FLHILL118 5/15/96 UNNH4 0.01256 1522B 21FLHILL118 5/15/96 UNNH4 0.01527 1522B 21FLHILL118 6/19/96 UNNH4 0.13925 1522B 21FLHILL118 6/19/96 UNNH4 0.16931 1522B 21FLHILL118 7/17/96 UNNH4 0.00922 1522B 21FLHILL118 7/17/96 UNNH4 0.01121 1522B 21FLHILL118 8/21/96 UNNH4 0.01233 1522B 21FLHILL118 8/21/96 UNNH4 0.01499 1522B 21FLHILL118 9/25/96 UNNH4 0.00671 1522B 21FLHILL118 9/25/96 UNNH4 0.00816 1522B 21FLHILL118 10/16/96 UNNH4 0.00423 1522B 21FLHILL118 10/16/96 UNNH4 0.00514 1522B 21FLHILL118 11/20/96 UNNH4 0.00645 1522B 21FLHILL118 11/20/96 UNNH4 0.00785 1522B 21FLHILL118 12/11/96 UNNH4 0.00489 1522B 21FLHILL118 12/11/96 UNNH4 0.00595 1522B 21FLHILL118 1/22/97 UNNH4 0.00472 1522B 21FLHILL118 1/22/97 UNNH4 0.00574 1522B 21FLHILL118 2/19/97 UNNH4 0.02014 1522B 21FLHILL118 2/19/97 UNNH4 0.02449 1522B 21FLHILL118 3/19/97 UNNH4 0.02911 1522B 21FLHILL118 3/19/97 UNNH4 0.03539 1522B 21FLHILL118 4/16/97 UNNH4 0.00601 1522B 21FLHILL118 4/16/97 UNNH4 0.00731 1522B 21FLHILL118 5/21/97 UNNH4 0.00765 1522B 21FLHILL118 5/21/97 UNNH4 0.0093 1522B 21FLHILL118 6/18/97 UNNH4 0.00766 1522B 21FLHILL118 6/18/97 UNNH4 0.00931 1522B 21FLHILL118 7/23/97 UNNH4 0.00737 1522B 21FLHILL118 7/23/97 UNNH4 0.00896 1522B 21FLHILL118 8/20/97 UNNH4 0.00672 1522B 21FLHILL118 8/20/97 UNNH4 0.00817 1522B 21FLHILL118 9/17/97 UNNH4 0.0069 1522B 21FLHILL118 9/17/97 UNNH4 0.00839 1522B 21FLHILL118 10/15/97 UNNH4 0.00046 1522B 21FLHILL118 10/15/97 UNNH4 0.00056 1522B 21FLHILL118 11/19/97 UNNH4 0.0003 1522B 21FLHILL118 11/19/97 UNNH4 0.00036 1522B 21FLHILL118 12/10/97 UNNH4 4.8E-05 1522B 21FLHILL118 12/10/97 UNNH4 5.9E-05 1522B 21FLHILL118 1/21/98 UNNH4 0.00052


1522B 21FLHILL118 1/21/98 UNNH4 0.00063 1522B 21FLHILL118 2/18/98 UNNH4 0.00823 1522B 21FLHILL118 2/18/98 UNNH4 0.01001 1522B 21FLHILL118 3/18/98 UNNH4 0.00153 1522B 21FLHILL118 3/18/98 UNNH4 0.00186 1522B 21FLHILL118 4/22/98 UNNH4 0.00229 1522B 21FLHILL118 4/22/98 UNNH4 0.00278 1522B 21FLHILL118 5/20/98 UNNH4 0.00687 1522B 21FLHILL118 5/20/98 UNNH4 0.00835 1522B 21FLHILL118 6/17/98 UNNH4 0.03734 1522B 21FLHILL118 6/17/98 UNNH4 0.0454 1522B 21FLHILL118 7/22/98 UNNH4 0.04168 1522B 21FLHILL118 7/22/98 UNNH4 0.05068 1522B 21FLHILL118 8/26/98 UNNH4 0.0225 1522B 21FLHILL118 8/26/98 UNNH4 0.02736 1522B 21FLHILL118 9/16/98 UNNH4 0.00359 1522B 21FLHILL118 9/16/98 UNNH4 0.00436 1522B 21FLHILL118 10/21/98 UNNH4 0.0001 1522B 21FLHILL118 10/21/98 UNNH4 0.00012 1522B 21FLHILL118 11/18/98 UNNH4 0.00266 1522B 21FLHILL118 11/18/98 UNNH4 0.00323 1522B 21FLHILL118 12/9/98 UNNH4 0.06517 1522B 21FLHILL118 12/9/98 UNNH4 0.07924 1522B 21FLHILL135 1/24/96 UNNH4 0.00164 1522B 21FLHILL135 2/21/96 UNNH4 0.00127 1522B 21FLHILL135 2/21/96 UNNH4 0.00155 1522B 21FLHILL135 4/17/96 UNNH4 0.00408 1522B 21FLHILL135 4/17/96 UNNH4 0.00496 1522B 21FLHILL135 5/15/96 UNNH4 0.00602 1522B 21FLHILL135 5/15/96 UNNH4 0.00732 1522B 21FLHILL135 6/19/96 UNNH4 0.0271 1522B 21FLHILL135 6/19/96 UNNH4 0.03295 1522B 21FLHILL135 7/17/96 UNNH4 0.01651 1522B 21FLHILL135 7/17/96 UNNH4 0.02007 1522B 21FLHILL135 8/21/96 UNNH4 0.04052 1522B 21FLHILL135 8/21/96 UNNH4 0.04926 1522B 21FLHILL135 9/25/96 UNNH4 0.00567 1522B 21FLHILL135 9/25/96 UNNH4 0.00689 1522B 21FLHILL135 10/16/96 UNNH4 0.00484 1522B 21FLHILL135 10/16/96 UNNH4 0.00588 1522B 21FLHILL135 11/20/96 UNNH4 0.00363 1522B 21FLHILL135 11/20/96 UNNH4 0.00442 1522B 21FLHILL135 12/11/96 UNNH4 0.00334 1522B 21FLHILL135 12/11/96 UNNH4 0.00406 1522B 21FLHILL135 1/22/97 UNNH4 0.00429 1522B 21FLHILL135 1/22/97 UNNH4 0.00521 1522B 21FLHILL135 2/19/97 UNNH4 0.01007


1522B 21FLHILL135 2/19/97 UNNH4 0.01225 1522B 21FLHILL135 3/19/97 UNNH4 0.00597 1522B 21FLHILL135 3/19/97 UNNH4 0.00726 1522B 21FLHILL135 4/16/97 UNNH4 0.02293 1522B 21FLHILL135 4/16/97 UNNH4 0.02787 1522B 21FLHILL135 5/21/97 UNNH4 0.00769 1522B 21FLHILL135 5/21/97 UNNH4 0.00935 1522B 21FLHILL135 6/18/97 UNNH4 0.00749 1522B 21FLHILL135 6/18/97 UNNH4 0.0091 1522B 21FLHILL135 7/15/97 UNNH4 0.01903 1522B 21FLHILL135 7/15/97 UNNH4 0.02314 1522B 21FLHILL135 7/23/97 UNNH4 0.00683 1522B 21FLHILL135 7/23/97 UNNH4 0.00831 1522B 21FLHILL135 8/20/97 UNNH4 0.00635 1522B 21FLHILL135 8/20/97 UNNH4 0.00772 1522B 21FLHILL135 9/17/97 UNNH4 0.00657 1522B 21FLHILL135 9/17/97 UNNH4 0.00799 1522B 21FLHILL135 10/15/97 UNNH4 0.00025 1522B 21FLHILL135 10/15/97 UNNH4 0.00031 1522B 21FLHILL135 11/19/97 UNNH4 0.00113 1522B 21FLHILL135 11/19/97 UNNH4 0.00137 1522B 21FLHILL135 12/10/97 UNNH4 9.2E-05 1522B 21FLHILL135 12/10/97 UNNH4 0.00011 1522B 21FLHILL135 1/21/98 UNNH4 0.00021 1522B 21FLHILL135 1/21/98 UNNH4 0.00026 1522B 21FLHILL135 2/18/98 UNNH4 0.00075 1522B 21FLHILL135 2/18/98 UNNH4 0.00091 1522B 21FLHILL135 3/18/98 UNNH4 0.00093 1522B 21FLHILL135 3/18/98 UNNH4 0.00112 1522B 21FLHILL135 4/22/98 UNNH4 0.00064 1522B 21FLHILL135 4/22/98 UNNH4 0.00078 1522B 21FLHILL135 5/20/98 UNNH4 0.02059 1522B 21FLHILL135 5/20/98 UNNH4 0.02504 1522B 21FLHILL135 6/17/98 UNNH4 0.02534 1522B 21FLHILL135 6/17/98 UNNH4 0.03081 1522B 21FLHILL135 7/22/98 UNNH4 0.05068 1522B 21FLHILL135 7/22/98 UNNH4 0.06162 1522B 21FLHILL135 8/26/98 UNNH4 0.00184 1522B 21FLHILL135 8/26/98 UNNH4 0.00223 1522B 21FLHILL135 9/16/98 UNNH4 0.00054 1522B 21FLHILL135 9/16/98 UNNH4 0.00066 1522B 21FLHILL135 10/21/98 UNNH4 7.9E-05 1522B 21FLHILL135 10/21/98 UNNH4 9.6E-05 1522B 21FLHILL135 11/18/98 UNNH4 0.00083 1522B 21FLHILL135 11/18/98 UNNH4 0.00101 1522B 21FLHILL135 12/9/98 UNNH4 0.00026 1522B 21FLHILL135 12/9/98 UNNH4 0.00031

Documents

Final TMDL for Lake Thonotosassa Unionized Ammonia and Lead