TOTAL MAXIMUM DAILY LOAD (TMDL) For Nutrients

Transcription

1 TOTAL MAXIMUM DAILY LOAD (TMDL) For Nutrients In Fenholloway River, (WBIDs 3473A and 3473B) Taylor and LaFayette Counties, Florida Prepared by: US EPA Region 4 61 Forsyth Street SW Atlanta, Georgia 30303

2 In compliance with the provisions of the Federal Clean Water Act, 33 U.S.C 1251 et. seq., as amended by the Water Quality Act of 1987, P.L , the U.S. Environmental Protection Agency is hereby establishing Total Maximum Daily Loads (TMDLs) for nutrients in the Fenholloway River (WBIDs 3473A and 3473B). Subsequent actions must be consistent with this TMDL.. /s/ James D. Giattina, Director Water Protection Division 2/19/09 Date ii

3 TABLE OF CONTENTS 1 INTRODUCTION PROBLEM DEFINITION WATERSHED DESCRIPTION WATER QUALITY STANDARD AND TARGET IDENTIFICATION Nutrient Water Quality Standards WATER QUALITY TARGET IDENTIFICATION Basis and Rationale For Nutrient Target Nutrient Target WATER QUALITY ASSESSMENT Source Assessment Point Sources Nonpoint Sources Analytical Approach Description of Coupled Hydrodynamic/Water Quality Model Model Water Quality Calibration Data Point and Nonpoint Source Nutrient Loads Model Calibration DEVELOPMENT OF TOTAL MAXIMUM DAILY LOADS Established Nutrient TMDLs Margin of Safety Seasonal Variation Alternative Wastewater Discharge Location REFERENCES...19 LIST OF TABLES Table 1. TMDLs Developed By EPA in...2 Table Land Cover Distribution (acres)...5 Table 3. Calibration Period point source and NPS TN Loads (lb/day)...13 Table 4. Calibration Period point source and NPS TP Loads (lb/day)...13 Table 5. Model Calibration Comparison for Chlorophyll-a...15 Table 6. TMDL for Total Nitrogen (lb/day)...16 Table 7. TMDL for Total Phosphorus (lb/day)...17 Table 8. Summary of TMDL Components for Fenholloway River...17 Table 9. Chlorophyll-a Levels for TMDL Conditions (µg/l)...18 LIST OF FIGURES Figure 1: Location of Fenholloway Watershed...4 Figure 2: Water Quality Sampling Stations...8 Figure 3: Water Quality Model Phytoplankton Kinetics...11 iii

4 LIST OF ABBREVIATIONS BOD Chl-a DMR DO EPA FAC FDEP HUC LA MGD MOS MS4 NLCD NPDES NPS SCI SRWMD TMDL TN TP UAA USGS WBID WLA WQS WWTF Biochemical Oxygen Demand (5-day test) Chlorophyll-a Discharge Monitoring Report Dissolved Oxygen Environmental Protection Agency Florida Administrative Code Florida Department of Environmental Protection Hydrologic Unit Code Load Allocation Million Gallons per Day Margin of Safety Municipal Separate Storm Sewer Systems National Land Cover Data National Pollutant Discharge Elimination System Nonpoint Source Stream Condition Index Suwannee River Water Management District Total Maximum Daily Load Total Nitrogen Total Phosphorus Use Attainability Analysis United States Geological Survey Water Body Identification Waste Load Allocation Water Quality Standard Wastewater Treatment Facility iv

5 SUMMARY SHEET Total Maximum Daily Load (TMDL) (d) Listed Waterbody Information State: Florida County: Taylor and Lafayette Counties Major River Basin: (HUC ) Listed Waterbodies ( (d) List): WBID Segment Name Constituent(s) 3473A Fenholloway River at Mouth Nutrients 3473B Fenholloway River below Pulp Mill Nutrients 2. TMDL Endpoints (i.e., Targets) The State of Florida s water quality standard (WQS) for nutrients states that the discharge of nutrients shall continue to be limited as needed to prevent violations of other standards contained in this chapter [Section FAC] and [i]n no case shall nutrient concentrations of a body of water be altered so as to cause an imbalance in natural populations of aquatic flora and fauna [Section FAC]. Because the State of Florida does not have specific numeric nutrient criteria, an annual average Chlorophyll-a (chl-a) concentration of 5 ug/l was determined to appropriately represent a numeric interpretation of the State s narrative WQS for the Fenholloway River. The target chl-a concentration is based on the near shore reference area of the Econfina Estuary. The TMDL prescribes allocations for Total Nitrogen (TN) and Total Phosphorus (TP) that achieve the chl-a target, which meets the State s WQS for nutrients. 3. TMDL Nutrient Components to Achieve Chl-a Endpoint in Fenholloway Estuary Stream Name Fenholloway River Fenholloway River Parameter WLA 1 (lb/day) v LA 1 (lb/day) TMDL 1 (lb/day) Percent Reduction 2 TN % TP % Note 1 : The TMDLs are expressed as annual average Note 2 : The percent reductions apply only to the WLA, as no reductions are required from nonpoint sources (LA). 4. Public Notice Date: October TMDL Considers Point Source, Nonpoint Source, or both: Both 6. Major NPDES Discharges to surface waters Facility Name NPDES No. Facility Type Receiving Stream Buckeye Florida Pulp Mill 1 FL Industrial Wastewater Fenholloway River City of Perry (no discharge land FL Domestic WWTP Spring Branch application) Note 1 : The proposed discharge point located 1.7 miles upstream from the mouth of the Fenholloway River is being evaluated. The same nutrient TMDL is applicable to the existing or proposed discharge location.

6 TOTAL MAXIMUM DAILY LOAD (TMDL) FENHOLLOWAY RIVER (WBIDS 3473A AND 3473B) 1 INTRODUCTION Section 303(d) of the Clean Water Act requires each state to list those waters within its boundaries for which technology based effluent limitations are not stringent enough to attain water quality standards applicable to the water s designated use(s). Listed waters are prioritized with respect to designated use classifications and the severity of pollution. In accordance with this prioritization, states are required to develop Total Maximum Daily Loads (TMDLs) for those water bodies that are not meeting water quality standards. The TMDL process establishes the allowable loadings of pollutants or other quantifiable parameters for a waterbody based on the relationship between pollution sources and in-stream water quality conditions, so that states can establish water quality based controls to reduce pollution from both point and non-point sources and restore and maintain the quality of their water resources (USEPA, 1991). The State of Florida Department of Environmental Protection (FDEP) developed a statewide, watershed-based approach to water resource management. Under the watershed management approach, water resources are managed on the basis of natural boundaries, such as river basins, rather than political boundaries. FDEP uses the watershed management approach for implementing TMDLs. The State s 52 basins are divided into 5 groups. Water quality is assessed in each group on a rotating five-year cycle. The Fenholloway River is located in the Econfina Basin. The Econfina Basin is part of the Group 1 basin, which was first assessed in The Florida Legislature established five water management districts (WMD) that are responsible for managing ground and surface water supplies in the counties encompassing the districts. The Econfina Basin is in the Suwannee River Water Management District (SRWMD). For the purpose of planning and management, the Econfina Basin is divided into three planning units: Econfina River, Fenholloway River and Steinhatchee River basins. A planning unit is either an individual primary tributary basin or a group of adjacent primary tributary basins with similar characteristics. These planning units contain smaller, hydrological-based units called drainage basins, which are further divided into water segments. A water segment usually contains only one unique waterbody type (stream, lake, channel, etc.) and is about five square miles. Unique numbers or waterbody identification (WBIDs) numbers are assigned to each water segment. 2 Problem Definition Florida s Section 303(d) list identified several WBIDs in the as not supporting water quality standards (WQS). The U.S. Environmental Protection Agency (EPA) assessed all available water quality information and determined the Fenholloway River to be impaired for nutrients for the WBIDs listed in Table 1. The TMDLs EPA is establishing in this report are pursuant to the 1998 Consent Decree in the Florida TMDL lawsuit (Florida Wildlife Federation, et al. v. Carol Browner, et al., Civil Action No. 4: 98CV356-WS, 1998). 1

7 Table 1. TMDLs Developed By EPA in WBID Segment Name Constituent(s) 3473A Fenholloway at Mouth Nutrients 3473B Fenholloway below Pulp Mill Nutrients In 2003, EPA proposed draft nutrient TMDLs in the Fenholloway River (WBIDs 3473A and 3473B), which were developed using a simple mass balance approach. Since that time, a more detailed modeling effort was initiated to better define the linkages between the causative agents (nutrients) and the response variables (phytoplankton) in the. One of the purposes of the modeling effort was to re-develop the nutrient TMDLs in the Fenholloway River. In October 2008, EPA re-proposed the draft nutrient TMDLs in the Fenholloway River that were based on the recent modeling effort. Based on the comments received during the 30-day public comment period, EPA is establishing the nutrient TMDLs contained in this report. In the proposed 2003 TMDLs, the nutrient loads were developed based on conservative natural loading estimates. However, based on a more recent analysis, the nutrient loads contained in this report correlate to a chl-a target based on overall system health that is expected to meet applicable WQS. In 2007, EPA established dissolved oxygen (DO) TMDLs for the Fenholloway River. The DO TMDLs reduced ammonia and BOD effluent values to a concentration necessary to achieve the WQS for DO. The nutrient allocations contained in this TMDL report are consistent with the DO TMDL and are required for either the existing discharge site or the proposed estuary discharge location at River Mile 1.7 of the Fenholloway River. 3 WATERSHED DESCRIPTION The Fenholloway River is located in northern Florida in the as shown in Figure 1. The Fenholloway River, a blackwater stream, is 36 miles long and its watershed drains approximately 392 square miles. The upper areas of the watershed are underlain by the Floridian Aquifer system. The aquifer system is confined in the upper headwaters and becomes semi-confined and unconfined as it moves southwest across San Pedro Bay. As the Fenholloway River continues toward the Gulf of Mexico, the watershed is underlain by a shallow surficial aquifer that is approximately 5 to 20 feet below ground surface. Sandy soils dominate the watershed area, though karst features are also present. Exposed limestone can be seen in the reaches on the Fenholloway River upstream of the Buckeye Florida pulp mill, which is the major point source discharge to the Fenholloway River. The pulp mill has impacted the hydrology and water quality of the Fenholloway River since The land cover for the WBIDs identified in this TMDL report are based on the National Land Cover 2

8 Dataset (NLCD) of 1995, and tabulated in Table 2. As Table 2 indicates, wetlands and forests (planted pine plantations) account for the majority of the land use in the WBIDs addressed in this TMDL report. The Fenholloway River has similar physical characteristics to the Econfina River. The Econfina River spans the length of Taylor County, which drains ultimately into the Gulf of Mexico. The Econfina River lies within the Gulf Coast Flatwoods subecoregion (75a). Within the Econfina River Basin, the land distribution is a combination of pine flatwoods and swamp forests, and the land use consists of cropland, pastures, and mixed forest. Between 1995 and 2001, the Econfina River has been sampled to establish biological community expectations and to identify specific thresholds for assessing the health of the stream system. The Stream Condition Index (SCI) has been the primary assessment method to determine stream health. The SCI process consists of collecting 20 D-frame dipnet sweeps (0.5 meter in length) of the most productive habitats in a 100 meter reach of stream. The organisms are sub-sampled, sorted, and identified to the lowest practical taxonomic level. Seven measurements of invertebrate health are calculated and compared with the expectations established by the reference site sampling. The SCI scores for the Econfina River were in the excellent range for three of the four sampling trips conducted. The lowest of the four SCI scores was in the good range in February, The physical and chemical parameters, including nutrients were sampled at three sites along the Econfina River (at Highway 14, Highway 27, and Highway 98) in April, 1999 (FDEP, 1999). Nutrient concentrations were not problematic in the Ecofina River, tending to be lower than average for Florida streams on most sampling dates. The DO concentration exceeded the Class III water quality standard of 5.0 mg/l at all stations sampled. All measured physical and chemical parameters and water quality variables at the three stations met the applicable criteria for Class III waterbodies. The healthy habitat and water quality observed in the Econfina River as well as similar landuse makes the Ecofina River an ideal reference stream for developing an appropriate target chl-a concentration for the Fenholloway River TMDLs. 3

9 Hamilton Co. Jefferson Co. Madison Co. Econfina River Fenholloway River Fenholloway River below Cooey Bridge Fenholloway River below Cooey Bridge FENHOLLOWAY 6 AT OLD FISH CAMP FENHOLLOWAY 5 FR BR ON SR A #* Spring Creek PERRY WWTF 3473B #* Taylor Co. kj Fenholloway River BUCKEYE FLORIDA Lafayette Co. : Sampling Station kj USGS_Gage #* NPDES County Boundary WBID 3473B & 3473A Other WBID's NHD flow Lines Miles Dixie Co. Figure 1: Location of Fenholloway Watershed 4

10 Table Land Cover Distribution (acres) Category Ecofina Watershed Fenholloway Watershed Steinhatchee Watershed Area % Area % Area % Residential 160 0% % 45 0% Commercial, industry, & public 95 0% 902 1% 258 0% Agriculture % % 501 0% Rangeland % % 799 0% Forest % % % Water 680 0% 351 0% 94 0% Wetlands % % % Barren and extractive % % % Transportation and Utilities 0 0% 632 0% 0 0% Total Area % % % 4 WATER QUALITY STANDARD AND TARGET IDENTIFICATION 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 The WBIDs addressed in this report are designated as Class III waters. The designated use of Class III waters is recreation, propagation and maintenance of a healthy, well-balanced population of fish and wildlife. The water quality criteria for protection of Class III waters are established by the State of Florida in the Florida Administrative Code (FAC), Section The individual criteria should be considered in conjunction with other provisions in WQS, including Section FAC [Surface Waters: Minimum Criteria, General Criteria] that apply to all waters unless alternative criteria are specified in FAC Section Nutrient Water Quality Standards The State s WQS state that the discharge of nutrients shall continue to be limited as needed to prevent violations of other standards contained in this chapter [Section FAC] and [i]n no case shall nutrient concentrations of a body of water be altered so as to cause an imbalance in natural populations of aquatic flora and fauna [Section FAC]. Because the State of Florida does not have specific numeric nutrient criteria, chlorophyll-a, total nitrogen (TN), and total 5

11 phosphorus (TP) are used to target concentrations, and subsequent loadings, necessary to achieve the State s WQS. 5 WATER QUALITY TARGET IDENTIFICATION 5.1 Basis and Rationale For Nutrient Target Algae grow in response to available light in the water column which depends on surface solar radiation and attenuation of light in the water column due to color and algae. Algae directly use inorganic forms of nitrogen and phosphorus for growth. Organic forms of nitrogen and phosphorus are mineralized to available inorganic forms. Nutrients are recycled through algal respiration and grazing by zooplankton. Both algae and particulate organic matter settle to the bottom producing a sediment oxygen demand and benthic nutrient fluxes. A brief discussion on the role of phosphorus and nitrogen on phytoplankton kinetics are described below and illustrated in Figure 3. Additional information is provided in the modeling report (HydroQual, 2008). The particulate and dissolved organic phosphorus decay in the waterbody is based on reactivity. A labile fraction describes organic material that decays on a time scale of several weeks to a month, while a refractory fraction accounts for decay processes lasting months to a year. The labile fraction decays primarily in the water column or else rapidly in the sediments; the refractory components mainly decompose in the sediments. Particulate organic phosphorus, whether refractory or labile, decomposes to dissolved organic phosphorus through hydrolysis, which is a temperature and bacterial biomass mediated reaction. The particulate fraction of organic phosphorus settles within the water column at a temperature-dependent rate and is deposited to the sediment where it is further decomposed through anaerobic processes. The dissolved form of organic phosphorus further decomposes through mineralization into the inorganic form of phosphorus which is lost through its utilization by algae as a nutrient essential for growth. The particulate and dissolved forms of nitrogen decompose through the same reaction pathways as phosphorus, with the particulate fractions settling to the sediment. The dissolved organic forms mineralize to ammonia, which is subsequently nitrified to nitrite and nitrate via a process that consumes dissolved oxygen. Nitrification is an aerobic reaction; therefore, the reaction decreases as DO concentrations decrease. Ammonia and nitrite plus nitrate are utilized by algae as nutrients for growth with ammonia being the preferred nutrient. Algae nutrient recycling replenishes the organic forms of nitrogen and ammonia during algal respiration and zooplankton grazing. Previous studies have shown that the organic nitrogen and phosphorous in pulp and paper mills is highly refractory and not subject to bacterial conversion to inorganic nutrient forms. Specific studies of the Buckeye effluent have suggested that the refractory component of the organic nutrients is approximately 80 percent and this finding is also included in the assignment of the 6

12 Buckeye organic nutrient load in the model (HydroQual, 2008). 5.2 Nutrient Target As stated in Section 4.1 of the TMDL report, FDEP s water quality standards currently have narrative nutrient criteria. Nutrient TMDLs require numerical endpoints to assess compliance with its nutrient WQS and in this case, a chl-a target was used. For these nutrient TMDLs, Barry A. Vittor & Associates, Inc. proposed an annual average chl-a target of 5 µg/l for Fenholloway River stations F10 and F11 based upon the Econfina River reference stations E08 and E10. This baseline reference level was defined such that when the annual average chl-a values in the Fenholloway system at stations F10 and F11 are less than 5 µg/l, the estuary should be considered to have good or non-impaired water quality. This is consistent with the USEPA National Coastal Condition Report II recommendations for Gulf Coast estuaries (USEPA, 2004). Because the Modeling Team determined it was a more accurate assessment of system health to judge compliance with an algal target or criterion over a region rather than at one specific location, the model results were averaged over two separate zones, each zone located near the mouth of the Econfina and Fenholloway Rivers during the growing season (May-October). These zones are analogous to the WBIDs used by FDEP for completing its water quality assessments (HydroQual, 2008). 6 Water Quality Assessment Water quality data is available from a number of sources, but the main database used for the modeling effort was collected and compiled by Environmental Planning and Analysis, Inc. (EP&A). The EP&A monitoring program collected data for the following parameters: salinity, conductivity, temperature, DO, ph, secchi depth, color, turbidity, alkalinity, chl-a, BOD 5, particulate organic nitrogen (PON), dissolved organic nitrogen (DON), total kjeldahl nitrogen (TKN), ammonia nitrogen (NH 3 ), nitrite and nitrate nitrogen (NO 2 +NO 3 ), particulate organic phosphorus (POP), dissolved organic phosphorus (DOP), orthophosphate (PO 4 ), silicate, particulate organic carbon (POC), dissolved organic carbon (DOC), total dissolved carbon, inorganic dissolved carbon, chloride, total dissolved solids, total suspended solids (TSS), particulate organic matter (POM), dissolved organic matter (DOM), particulate inorganic matter (PIM), dissolved inorganic matter (DIM), and sulfide. Samples were obtained from surface, mid-depth and bottom locations in the water column (mid-depth and bottom when possible) for 10 stations in the Fenholloway River, 8 stations in the Econfina River, and 21 stations in the near-shore Gulf of Mexico (HydroQual, 2008). Other sources of data include the FDEP ambient monitoring stations throughout the basin for the purposes of 303(d) listing and TMDL development. The Buckeye Florida Pulp Mill collects DO and other chemical data, including nutrients, in the Fenholloway River at SR-356, as well as contracted special studies in the Econfina River basin. In addition, EPA conducted special studies in both the river and estuary areas of the Econfina and Fenholloway Rivers from 1989 to All water quality data collected in the Fenholloway and Ecofina Rivers are shown in Figure 2. Additional details are provided in the Fenholloway modeling report (USEPA, 2003) and the previously mentioned Buckeye reports. 7

13 Figure 2: Water Quality Sampling Stations 6.1 Source Assessment An important part of the TMDL analysis is the identification of source categories, source subcategories, or individual sources of pollutants in the watershed and the amount of loading contributed by each of these sources. Sources are broadly classified as either point or nonpoint sources (NPS). The growth of algae in the Fenholloway River, Econfina River, and near shore Gulf area is dependent on the nutrient loads associated with the Buckeye wastewater discharge, nutrients in surface runoff (NPS), atmospheric deposition, ambient color levels and tidal exchange at the near shore Gulf model boundaries. The nutrient load from Buckeye for the calibration period ( ) was based on effluent data and measurements at station F03, just downstream of the Buckeye wastewater discharge on the Fenholloway River. Surface runoff nutrient loads were derived from nutrient measurements at station E01 on the Econfina River and estimated runoff flows developed from USGS flow data. The coastal nutrient load includes direct runoff to the Gulf plus an estimate 8

14 of groundwater nutrient input. Atmospheric deposition was estimated from National Atmospheric Deposition Program (NADP) data and a study on Tampa Bay Point Sources A point source is defined as a discernable, confined, and discrete conveyance from which pollutants are or may be discharged to surface waters. Point source discharges of industrial wastewater and treated sanitary wastewater must be authorized by National Pollutant Discharge Elimination System (NPDES) permits. NPDES permitted facilities, including certain urban stormwater discharges such as municipal separate stormwater systems (MS4) areas, certain industrial facilities, and construction sites over one acre, are storm-water driven sources considered point sources in this report. There are no MS4 jurisdictions impacting the impaired WBIDs. There is one major NPDES point source, Buckeye Florida Pulp Mill (FL ) that discharges to the Fenholloway River. Facilities discharging the pollutants of concern to surface waters are assigned a waste load allocation (WLA) in the TMDL analysis. The WLA for Buckeye Florida Pulp Mill (Buckeye) can be found in Table 8. The City of Perry Wastewater Treatment Facility (WWTF) (FL ) is located 1.7 miles upstream of the Fenholloway River, but ceased its discharge to surface waters in The City of Perry WWTF is now using a land treatment system with no river discharge; therefore, this facility is not included in the WLA portion of the TMDL. Buckeye is an industrial NPDES facility that discharges into the Fenholloway River upstream of Hwy 98, about 20 miles from the mouth of the river. Buckeye has a design flow of 43.8 million gallons per day (MGD) and is presently permitted to discharge BOD at daily average and maximum loads of 13,200 and 19, 800 lb/day, respectively. The current 2005 permit requires monitoring and limits for TN and TP. Because that permit has been appealed, it is scheduled for renewal in 2009 and new limits and reporting requirements will be incorporated into the new permit consistent with this TMDL Nonpoint Sources Nonpoint sources of pollution are diffuse sources that cannot be identified as entering a waterbody through a discrete conveyance at a single location. These sources generally, but not always, involve accumulation of pollutants on the land surface that wash off as a result of storm events. The vast majority of the nonpoint source runoff in the and Fenholloway River watershed are natural background levels of pollutants running off wetlands, forest and other non anthropogenic areas. Nonpoint source runoff in the basin is attributed to natural background loads and does not adversely impact natural water quality conditions. 6.2 Analytical Approach In 2005, HydoQual was retained by the Buckeye Florida, L.P. to develop and calibrate a coupled hydrodynamic/water quality model of the Fenholloway River downstream of the existing Buckeye wastewater discharge and the adjacent area of the Gulf of Mexico. One of the purposes of this 9

15 modeling analysis was to provide a tool that would be used by EPA Region 4 to develop nutrient TMDLs for the Fenholloway River. The model development and calibration was a collaborative effort between HydroQual, EPA Region 4, FDEP, and Buckeye. The modeling effort is the result of environmental studies from a number of sources (HydroQual Inc., Environmental Planning & Analysis, Inc., Barry A. Vittor & Associates, Inc., EPA Region 4, and FDEP). EPA and FDEP independently evaluated the water quality model used to derive the nutrient allocations in this TMDL and concur with the assumptions, model input parameters, and results. The following is a summary of the modeling analysis with the nutrient TMDLs. Additional detail can be found in the modeling report (HydroQual 2008) Description of Coupled Hydrodynamic/Water Quality Model A coupled hydrodynamic/water quality model of the Fenholloway River, Econfina River and near shore Gulf of Mexico region was developed and calibrated for completing the nutrient TMDL. The hydrodynamic model used is the Estuarine Coastal and Ocean Model (ECOM) and the water quality model used is the Row-Column AESOP (Advanced Ecological Systems Modeling Program) model (RCA), as shown in Figure 3. Both models are time-variable and three-dimensional. The model has 2,880 segments horizontally and six layers in the vertical yielding a total of approximately 17,280 model segments with 5,028 water segments. The hydrodynamic model computes time-variable currents in each model segment based on tides, freshwater flow, density and winds. The water quality model computes the growth of algae based on available light and nutrients. The models were calibrated with water quality data collected during 1998 through 2001 by EP&A approximately 6 to 12 times per year at stations throughout the study area. 10

16 Figure 3: Water Quality Model Phytoplankton Kinetics Three modeling issues that are not usually considered in most nutrient algal models were included in the nutrient TMDL model development. These issues are: the calculation of light extinction as a function of color; uptake of nutrients by submerged aquatic vegetation (SAV) and macroalgae; and representation of the refractory nature of Buckeye s effluent organic nutrients. Previous studies by EP&A have shown that there is SAV in the Gulf area of the model domain and more recent data collected by BVA has shown that there is also macroalgae growth in this area. To account for the nutrient uptake of macroalgae, epiphytes on SAV, and to some extent SAV, an uptake rate of nitrogen and phosphorous was estimated based on model calibration of Gulf nutrient and algal levels Model Water Quality Calibration Data The model was calibrated with water quality data collected between 1998 through Water quality data was collected by Environmental Planning and Analysis, Inc. (EP&A) approximately 6 to 12 times per year at most of the estuary and river stations. Field measurements included temperature, salinity, ph, dissolved oxygen (DO), secchi depth, and occasionally light extinction. Laboratory measurements were generally performed for color, carbon, nutrients, and algae (chl-a). The water quality data represent a range of wet and dry years. The USGS measured flows at Econfina River near Perry gage # and Fenholloway River near Perry gage # for the calibration years. During 1998, peak flows reached approximately 700 cfs and 1,200 cfs in the Fenholloway and Econfina Rivers, respectively. Whereas, peak flows in 2000 are less than 60 cfs in 11

17 the Econfina and 200 cfs in the Fenholloway (of which about 70 cfs is wastewater flow from Buckeye). A significant consequence of high flow is the increase in water column color as evidenced by the elevated color levels at station E06 in the Econfina River during The general patterns in water quality indicated by the data are elevated levels of color and inorganic nutrients in the Fenholloway Estuary, relative to the color and nutrient levels in the Econfina Estuary, and low levels of color and nutrients at the outer Gulf stations. The stations in the inner Gulf region represent a transition between landside water quality and outer Gulf water quality. Chla data also indicate algal levels are higher at the Fenholloway stations in comparison to the Econfina stations Point and Nonpoint Source Nutrient Loads The growth of algae in the Fenholloway River, Econfina River, and nearshore Gulf area is dependent on the nutrient loads associated with the Buckeye wastewater discharge, nutrients in surface runoff from nonpoint sources, atmospheric deposition, ambient color levels and tidal exchange at the near shore Gulf model boundaries. The nutrient load from Buckeye for the calibration period ( ) was based on effluent data and measurements below Buckeye. Surface runoff nutrient loads were derived from nutrient measurements at upper river station on the Econfina River and estimated runoff flows developed from USGS flow data. The coastal nutrient load includes direct runoff to the Gulf plus an estimate of groundwater nutrient input. Atmospheric deposition was estimated from National Atmospheric Deposition Program (NADP) data and a study on Tampa Bay. The Buckeye and NPS loads for TN and TP are summarized in Tables 3 and 4, respectively. Although there is considerable variability in nonpoint source nutrient loads due to the hydrology, the average Buckeye TN and TP load is approximately equal to the nonpoint source TN load and twice the nonpoint source TP load Model Calibration The components of the water quality model include transport (water circulation), loads and various biological and physical kinetic coefficients. The time-variable water velocities for each model segment were computed with the hydrodynamic model for use in the water quality model. Timevariable point source and nonpoint source nutrient loads were derived as previously discussed and input to the water quality model. The water quality at the boundaries of the Gulf region of the model was assigned from measurements at stations near the boundaries. The model coefficients describing algal uptake of nutrients, growth, respiration, and settling were within the typical range of values used in previous modeling studies. However, in this study, there were three modeling issues that are not usually considered in most nutrient algal models: the calculation of light extinction as a function of color; uptake of nutrients by SAV and macroalgae; and representation of the refractory nature of Buckeye s effluent organic nutrients. 12

18 Table 3. Calibration Period point source and NPS TN Loads (lb/day) Source Average Econfina NPS Fenholloway NPS Aucilla NPS Coastal NPS Atmospheric NPS Total NPS Buckeye PS Total Table 4. Calibration Period point source and NPS TP Loads (lb/day) Source Average Econfina NPS Fenholloway NPS Aucilla NPS Coastal NPS Atmospheric NPS Total NPS Buckeye PS Total The available light for algal growth in the water column is dependent on the extinction of light with depth and the total depth. In this system, the extinction of light as defined by the light extinction coefficient, k e, is strongly dependent on the water column color levels. The water color concentration in the study area is affected by the Buckeye wastewater discharge and the elevated color levels associated with high runoff flows. Because color measurements at the water quality stations were limited to 6 to 12 measurements per year, daily color levels were computed with the model based on the Buckeye effluent and runoff color inputs. The light extinction coefficient was then computed each day in all model segments from the model computed color concentration using a relationship of k e versus color derived from EP&A data. 13

19 Previous studies by EP&A have shown that there is SAV in the Gulf area of the model domain. More recent data by Barry A. Vittor and Associates, Inc. (BVA) has shown that there is also macroalgae growth in this area. To account for the nutrient uptake of macroalgae, epiphytes on SAV, and to some extent SAV, an uptake rate of nitrogen and phosphorous was estimated based on model calibration of Gulf nutrient and algal levels. An equivalent benthic nutrient uptake rate, representing the nutrient demands of all benthic primary productivity, was assigned at a range of 0-40 mgn/m 2 /day for nitrogen and 0-4 mgp/m2/day for phosphorous. To put this in perspective, an uptake rate of 40 mgn/m 2 /day of nitrogen would be equivalent to 100 g/m 2 of biomass with a nitrogen content of 1.5% growing at a rate of about 0.025/day. This base benthic nutrient uptake rate was varied with temperature to represent a seasonal growth pattern. The base nutrient uptake rate was also reduced when water column nutrients were low to represent an expected reduction in nutrient uptake rates. The spatial pattern of benthic nutrient uptake rates was assigned based on 2001 SAV maps of the area, with no SAV uptake near the mouth of the Fenholloway River and the highest SAV uptake rates in the shallow Gulf waters near the Econfina River. Benthic nutrient uptake was assigned at zero for 1998 based on providing a better model fit of the measured chl-a and nutrient data. This assumption of no benthic nutrient uptake is consistent with the likely suppression of primary productivity associated with high color levels in the Gulf resulting from high runoff flows. Previous studies have shown that the organic nitrogen and phosphorous in pulp and paper mills is highly refractory and not subject to bacterial conversion to inorganic nutrient forms. Specific studies of the Buckeye effluent have suggested that the refractory component of the organic nutrients is approximately 80 percent. To be conservative in the modeling analysis, the refractory component of Buckeye s effluent organic nitrogen and phosphorous was set at 60 percent with a corresponding 40 percent labile component. However, as a practical matter, model sensitivities demonstrated that computed algal growth is not very sensitive to the assigned refractory fraction of Buckeye effluent organic nutrients. The model calibration reproduces the temporal and spatial patterns in the data reasonably well. Specifically, the elevated chl-a levels in 1998 are reproduced by the model and the generally higher chl-a levels near the Fenholloway Estuary are also computed by the model. For the growing season (May-October) of each calibration year, the computed volume-weighted average chl-a levels in each zone were compared to the average chl-a levels measured at all the water quality stations within each zone. The results of this comparison are summarized in Table 5. The comparison between the model and data in both the Econfina and Fenholloway zones is reasonable and indicates the model is suitable for use in developing a nutrient TMDL (HydroQual, 2008). 14

20 Table 5. Model Calibration Comparison for Chlorophyll-a Year Model Calibration Comparison for Chlorophyll-a (µg/l) (Growing Season Average) Econfina River Zone Fenholloway River Zone Data Average Model Average Data Average Model Average Development of Total Maximum Daily Loads The TMDL process quantifies the amount of a pollutant that can be assimilated in a waterbody, identifies the sources of the pollutant, and recommends regulatory or other actions to be taken to achieve compliance with applicable water quality standards based on the relationship between pollution sources and in-stream water quality conditions. A TMDL can be expressed as the sum of all point source loads (Waste Load Allocations, WLA), non-point source loads (Load Allocations, LA), and an appropriate margin of safety (MOS), which takes into account any uncertainty concerning the relationship between effluent limitations and water quality: TMDL = Σ WLAs + Σ LAs + MOS The objective of a TMDL is to allocate loads among all of the known pollutant sources throughout a watershed so that appropriate control measures can be implemented and water quality standards achieved. 40 CFR (i) states that TMDLs can be expressed in terms of mass per time (e.g. pounds per day), toxicity, or other appropriate measure. The TMDLs for the Fenholloway River are expressed as annual average daily loads in units of pounds per day (lb/day). 7.1 Established Nutrient TMDLs The established nutrient TMDLs for point and nonpoint source loads achieve an annual chl-a target of 3.29 µg/l, for the critical year of In 2006, BVA proposed an annual average chla reference condition for the near shore estuary system of 5 µg/l, based upon the Econfina Estuary near shore area. Meeting the 3.29 ug/l annual average Chl-a, which is 30 percent less than the 5 ug/l chl-a target, provides a significant margin of safety. The nonpoint source nutrient loadings for this TMDL are set to the 1998 critical year nonpoint 15

21 source loading conditions as calibrated by the model. The annual average Buckeye TN and TP loads are required to be 2698 lb/day and 600 lb/day, respectively, as shown in Tables 6 and 7. These point source loads represent a 24 and 19 percent reduction from existing TN and TP loads as shown in Tables 3 and 4. These point source loads are required for either the existing or proposed River Mile 1.7 discharge site. Reductions are not required from nonpoint sources as the loadings from these sources are considered background. A summary of the TMDL components is provided in Table 8. Industrial permits typically expressed nutrient limits in terms of loads rather than concentration. This TMDL requires modification of the Buckeye permit to reflect annual average TN and TP limits consistent with the loads provided in Table 8. Table 6. TMDL for Total Nitrogen (lb/day) Source 1998* Average Econfina NPS Fenholloway NPS Aucilla NPS Coastal NPS Atmospheric NPS Total NPS Buckeye PS Total

22 Table 7. TMDL for Total Phosphorus (lb/day) Source Average Econfina NPS Fenholloway NPS Aucilla NPS Coastal NPS Atmospheric NPS Total NPS Buckeye PS Total Table 8. Summary of TMDL Components for Fenholloway River WBID Parameter WLA (lb/day) LA (lb/day) TMDL (lb/day) Percent Reduction A, 3473B TN % 3473A, 3473B TP % Note: The percent reductions apply only to the WLA, as no reductions are required from nonpoint sources (LA). The results of the computed growing season and annual average chl-a for each of the zones are summarized in Table 9 for The growing season and annual average chl-a for each of the years in both the Fenholloway and Econfina zones is less than the chl-a target of 5 µg/l as an annual average. 17

23 Table 9. Chlorophyll-a Levels for TMDL Conditions (µg/l) Year Econfina River Zone Fenholloway River Zone Growing Season Annual Growing Season Annual Note: Growing season average is May-October (2001 represents May-September) 2001 annual average represents January-September 7.2 Margin of Safety There are two methods for incorporating a MOS in the analysis: a) implicitly incorporate the MOS using conservative model assumptions to develop allocations; or b) explicitly specify a portion of the TMDL as the MOS and use the remainder for allocations. An implicit MOS was used in the TMDL analysis through multi-year modeling and an abundance of available data to assure the reliability of the modeling. Four years were simulated in the water quality model, including two critical low flow years and the high flow critical year of Meeting the 1998 annual average 3.29 ug/l chl-a, which is 30 percent less than the 5 ug/l chl-a target, provides a significant margin of safety. 7.3 Seasonal Variation Seasonal variation was incorporated in the models by using the 1998 to 2001 critical period of record of flow recorded at the gages. Seasonality was also addressed by using all water quality data associated with the impaired areas, which was collected during multiple seasons and through the use of multi-year modeling. 7.4 Alternative Wastewater Discharge Location Ongoing work is being done to evaluate an alternative estuary wastewater discharge location, with the discharge point located 1.7 miles upstream from the mouth of the Fenholloway River. The hydrodynamic and water quality model extends into the Gulf of Mexico, and the grid includes the proposed estuary discharge location. The nutrient TMDLs contained in this report are applicable to both the existing site and the alternative estuary discharge location. 18

24 8. References Barry Vittor and Associates, Inc. April 2006 Ecological Monitoring of the Fenholloway and Econfina Rivers, 2006, February 2007 Florida Department Environmental Management (FDEP), Basin Status Report: Suwannee, November FDEP, EcoSummary Ecofina Hwys 14 & 27 & 98 4/6/99, FDEP Environmental Assessment Section, Tallahassee, FL, HydroQual, Inc., August 21, Fenholloway Nutrient TMDL Modeling, Prepared for Buckeye Cellulose Corp., Mahwah, NJ. SJWMD, Interim Pollutant Load Reduction Goals for Seven Major Lakes in the Upper, May USEPA, Final Total Maximum Daily Load (TMDL) in Fenholloway River and Bevins (Boggy) Creek, (Includes TMDLs for Dissolved Oxygen, Biochemical Oxygen Demand, Unionized Ammonia, Fecal Coliform, and Dioxin), Taylor and LaFayette Counties, Florida, prepared by US EPA Region 4, Atlanta, GA, April USEPA, National Coastal Condition Report II, EPA-620/R-03/002, December USEPA, Fenholloway River and Estuary: Hydrodynamic and Water Quality Modeling Report, May USEPA, Region 4. Atlanta, GA USEPA, Nutrient Criteria Technical Guidance Manual Rivers and Streams, Office of Water, Office of Science and Technology, EPA-822-B , Washington DC, July, USEPA, Guidance for Water Quality based Decisions: The TMDL Process. U.S. Environmental Protection Agency, Office of Water, Washington, DC. EPA-440/ , April Vogelmann, J.E., S.M. Howard, L. Yang, C.R. Larson, B.K. Wylie, N. Van Driel, Completion of the 1990s National Land Cover Data Set for the Conterminous United States from Landsat Thematic Mapper Data and Ancillary Data Sources, Photogrammetric Engineering and Remote Sensing, 67: