# TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



# Appendix B-6: Statistical Analysis of Ambient Water Quality Data

in Florida Streams by FDEP’s Nutrient Regions

# TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



# B6-1 

# Appendix B-6. Statistical Analysis of Ambient Water Quality Data in Florida

Streams by FDEP’s Nutrient Regions

The United States Environmental Protection Agency’s (U.S. EPA) Nutrient Criteria Technical

Guidance Manual: Rivers and Streams (USEPA 2000a) describes several general approaches,

with certain options, that can be used to deve lop numeric nutrient criteria for streams. In all

cases, consistent with the Clean Water Act (CWA), the objective is to determine a level of

nutrients that will provide protection of aquatic li fe both in-stream and downstream of a point of

application. The approach most often preferred is to quantify a stressor-response relationship

between excess nutrients and adverse effects on a quatic life and then use that relationship to

establish effects-based criteria. The necessary observed dose-response relationship could be

described by a model (e.g., trophic state classifi cation, regional predic tive model, nutrient

sensitive biocriteria), which, in tu rn, would link nutrient concentra tions to the relative risk of

environmental harm. Nutrient criteria based on a cause-effect relationship between nutrients and

valued ecological attributes coul d thus be considered directly linked to maintaining designated

uses. Such criteria might be scientifically defe nsible but have proved to be elusive. While the

underlying relationship certai nly exists, in nature it has often been difficult to quantify because

of the complexity of nutrient dynamics a nd the influence of in terfering factors.

Without data and information to quantify biolog ical dose-response relati onships for nutrients,

U.S. EPA recommends the reference condition approach as an alternative. With that approach, a

reference condition in term s of nutrient concentration is determined empirically from a statistical

distribution of nutrient data that can be assumed to inherently protect aquatic life. Under U.S.

EPA’s reference condition approach, one option involves setting criteria on the basis of an

inclusive distribution of nutrient values obtained from minima lly disturbed reference sites in a

designated ecoregion (based on climate and geol ogy). In such a case, U.S. EPA recommends

using an upper percentile value of this distribution to represent a level of nutrient concentration

that will inherently protect aquatic life. This methodology will ensure that nutrient

concentrations associated with biologically healthy, well-balanced communities would be

considered acceptable as protective of those comm unities. However, the approach is an inference

model and does not definitively demonstrate th at exceeding the threshold established by the

distribution of reference sites re sults in harm (impairment) to the aquatic life in a particular

waterbody. Multiple factors can strongly influen ce the expression of biological responses to

nutrients across waterbodies, such as water velo city, residence time, availability of the other

nutrients, presence of grazers, av ailability of light (because of tree cover and/or water

transparency), and availability of suitable habitat. The minimally affected reference water

approach identifies concentrations that are presumed to be inhere ntly protective of the waterbody

because these concentrations are associated with demonstrated minimally disturbed systems with

healthy biological communities

Also under U.S. EPA’s reference condition approac h, another option can be used to extrapolate a

reference condition of nutrient c oncentration that can be assumed to inherently protect aquatic

life. In those situations where a cause-effect relationship cannot be numerically quantified (but is

nonetheless firmly qualitatively established, e.g., nutrient impact s are documented) and where

known, documented reference sites ar e either unavailable or of insufficient number, U.S. EPA

suggests an option that is often referred to as the all streams approach. In this application of U.S.

# TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



# B6-2 EPA’s reference condition approach, a distribution of nutrient data is assembled from all sites in

an ecoregion (or, alternatively, a random selecti on of sites). Assuming th e pool of sites in the

distribution is large enough to represent all waters in the re gion and can be presumed to

reasonably reflect the full range of ambient conditi ons with a disturbance gr adient from least to

most affected, the selection of a lower percentile of this distribution (e.g., 25 th 

# percentile) should

provide a nutrient level that can be assumed to inherently prot ect aquatic life. Because of the

intended scale of application and the availability of data at th e time of publication, U.S. EPA

used this method to develop and publish under CWA section 304(a) recommended nutrient

criteria for streams and lakes in nutrient ecoregi ons IX, XII, and XIII. Although an all sites data

distribution approach does not dire ctly link nutrient concentrations to valued ecological attributes

(healthy, well-balanced populations of flora or fauna), it does make the presumption that the 25 th



# percentile will closely approximate a reference condition for that geographic location. Several

examples with data from actual reference si tes have supported this assumption (USEPA 2000a;

USEPA 2000b)

The purpose of the analysis presented here is to evaluate data from all sites by the Florida

Department of Environmental Protection (FDEP) nutrient region, not simply by reference site.

The 25 th 

# percentile was published by U.S. EPA in guidance on developing nutrient criteria

(USEPA 2000a; USEPA 2000b; USEP A 2001; USEPA 2007), and the 25 th 

# percentile of the

entire site population was the basis of U.S. EPA’s recommende d ecoregional criteria (USEPA

2000c; USEPA 2000d). Although the 25 th 

# percentile was recommende d, other percentiles are

presented in this appendix because they might have application elsewhere. Benchmark site

distributional statistics, computed elsewhere, are compared to the all streams statistics presented

here.



# Data Processing Steps

This section provides an overview of the data used and processing steps to compute the 25 th



# percentile statistics by FDEP nutrient region.

 FDEP provided the all streams data set to EP A. The data were quality assurance (QA)

reviewed and screened and se rved as the population of sites from which FDEP drew the

benchmark data set. FDEP verified that thes e data, primarily from STORET, are of known or

defensible quality and the data are data that are very representative of Florida’s flowing

waters. The all streams data set containe d 92,360 records corresponding to 7,373 sites. The

latitude and longitude from the Impaired Wate rs Rule (IWR) database, Run 35 was used for

44 all streams sites that did not have latitude and longitude in the FDEP-provided all streams

data set.

 The updated site locations were entered into a geographic information system (GIS) along

with the revised FDEP nutrient regions and Florida waterbody ID (WBID) coverage, also

provided by FDEP. Sites were further attribut ed with the FDEP nutrient region and WBID.

Removing sites that did not exist in one of the FDEP nutrient re gions and sites that were not

in a WBID left 6,383 sites, or 78,370 records, for further consideration.

 One of the FDEP outlier analysis steps for benchmark sites was to remove observations

greater than the upper adjacent value. When a pplied to the total phosphorus (TP) and total

nitrogen (TN) data by FDEP nutrient region, 5% to 12% of the data would be removed

depending on FDEP nutrient region and parameter. This approach was abandoned in lieu of a

# TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



# B6-3 simple screening threshold to remove erroneous data. The screening th resholds of 15 mg/L

and 100 mg/L of TP and TN, respectively, were selected, and 18 TP and 20 TN observations

were removed. The same threshold of 100 mg/L wa s applied to the other nitrogen parameters

analyzed. Further, if any nitr ogen parameter exceeded 100 mg/L, all nitrogen parameters for

that sample were removed. Data from canals and samples with a specific conductivity

exceeding 5,000 μS/cm were removed from the anal ysis so as to focus on freshwater streams

and rivers. That process reduced the number of records from 78,370 to 65,311 for processing.

 Total inorganic nitrogen (TIN) was co mputed as the sum of ammonia (NH 3 

# ) plus nitrite (NO 2 

# )

plus nitrate (NO 3 

# ), and organic nitrogen (OrgN) was computed as Total Kjeldahl Nitrogen

(TKN) minus NH 3 

# only when both component parameters were reported.

 The analyzed chl . a data are for suspended chlor ophyll and are for raw and pheophytin

corrected values.

 Data were organized by WBID-Y ear, and observation counts were made in a manner identical

to that used by FDEP’s analysis of benchmar k sites. That is, whenever the TP observation

count for a particular WBID-Year was less than four, all TP observations for that WBID-Year

were dropped. A similar process for TN and all other nitrogen parameters was implemented.

That process reduced the number of records from 65,311 to 51,366 for processing.

 The TP, nitrogen, and chlorophyll parameters were transformed by taking the natural

logarithm (e.g., LN(TP), LN(TN)). Log transf ormation converts data that are positively

skewed to more symmetrically (closer to nor mally) distributed da ta. The mean of the

transformed data was computed for each WBID -Year remaining in the analysis after the

above screening steps.

 The above analyses were performed using MS Access®. To check the computations, the 2005

data from WBID 1443D were extracted from th e original FDEP file and analyzed using a

spreadsheet. The end results were compared to the results from MS Access® and found to be

the same. Also, individual data for site 21F LGW_3549 were compared to the benchmark data

set. All nitrogen and phosphorus results were identical for the 99 samples that were in

common. The benchmark data set did have one add itional sample (the most recent) that might

be attributed to source data status, but it was not believed to be a si gnificant issue for the

current work.



# Nutrient Results

Using the data processed as described earlier , the mean, standard deviation, and various

percentiles were estimated by FDEP nutrient re gion (Tables B6-1 and B6-2). The means and

standard deviations from Tables B6-1 and B6-2 were used to compute theoretical distributions

assuming a lognormal distribution and were back -transformed (Tables B6-3 and B6-4). The

percentiles shown in Table B6-1 were also back-transformed and are shown as “empirical

computed distribution statistic s” in Table B6-3 as well.

TP distributional statistics are presented for th e Bone Valley and North Central Regions (Figure

B6-1) and for the Northeast, Panhandle, and Peni nsula Regions (Figure B6-2). TN distributional

statistics are presented for the Panhandle Regi on and the combined Northeast-North CentralPeninsula-Bone Valley Region (Figure B6-3). In Figures B6-1, B6-2, and B6-3, open symbols

indicate percentiles computed from an assu med lognormal distributi on while solid symbols

# TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



# B6-4 indicate those from the empiri cal distribution. When comparing the empirical and theoretically

derived 25 th 

# percentiles (i.e., 0.236 mg/L and 0.227 mg/L TP for the Bone Valley from Table B6-

3), the maximum difference was 0.009 mg/L fo r TP and 0.029 mg/L for TN. The maximum

difference for the other nitrogen parameters was 0.079 mg/L.

Although little difference existed between the th eoretical and empirical computed results, the

theoretically computed percentiles from this an alysis were used and compared to similarly

computed values from the benchmark sites (Table B6-5). In all instances for all nutrient species,

the 25 th 

# percentile from the all streams data was less than the 75 th 

# percentile (and therefore the

90 th 

# percentile) from the benchmark data set. In particular, the all streams 25 th 

# percentile TP was

approximately 25% of the benchmark 90 th 

# percentile and 40% of the benchmark 75 th 

# percentile

in the North Central and Panha ndle Regions. The all streams 25 th 

# percentile TP ranged from 42%

to 60% of the benchmark 90 th 

# percentile and 57% to 80% of the 75 th 

# benchmark percentile in the

Bone Valley, Northeast, and Peninsula Re gions. TN values for the all streams 25 th 

# percentile TN

ranged from 51% to 53% of the benchmark 90 th 

# percentile and 67% to 69% of the benchmark

75 th 

# percentile. The all streams 25 th 

# percentile TIN and OrgN ranged from 28% to 38% of the

benchmark 90 th 

# percentile and 67% to 69% of the benchmark 75 th 

# percentile. The all streams 25 th



# percentile nitrate/nitrite (NO

x 

# ) ranged from 13% to 18% of the benchmark 90 th 

# percentile and

26% to 37% of the benchmark 75 th 

# percentile.TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh WatersB6-5Table B6-1. Distributional StatisticsComputed from the Natural Logarithm Transformed All Streams DataObservationsDistributional Statistics Estimated from LN Transformed DataParameterFDEP NutrientRegionNumberof WBIDYearsNumberof WBIDs Mean LNStd DevLN10th%tileLN25th%tileLN50th%tileLN75th%tileLN90th%tileLNTP (mg/L) Bone Valley555 142 -0.8694 0.8489-1.84547 -1.48194 -0.95708 -0.35687 0.32167TP (mg/L) North Central 420 50 -1.6507 1.0598-2.85363 -2.3291 -1.75383 -1.15221 -0.30526TP (mg/L) Northeast347 111 -2.3968 0.8153 -3.27757 -2.88301 -2.45331 -2.00467 -1.61934TP (mg/L) Panhandle435 167 -3.417 0.9884 -4.61254 -4.16749 -3.39228 -2.92946 -2.04425TP (mg/L) Peninsula1843 427 -2.1644 0.7407 -3.0213 -2.63774 -2.22592 -1.78303 -1.20475TN (mg/L) Panhandle404 146 -0.427 0.5999 -1.18593 -0.79297 -0.42644 -0.10844 0.31278TN (mg/L) NE-NC-Pen-BV 2902 702 0.16763 0.44259 -0.34988 -0.09828 0.14958 0.422094 0.712191NOx(mg/L) Panhandle429 164 -2.1851 1.5555 -4.57421 -3.10851 -2.00869 -1.02489 -0.30105NOx(mg/L) NE-NC-Pen-BV 3054 718 -2.6932 1.3904 -4.4457 -3.76488 -2.79399 -1.68176 -0.76233TKN (mg/L) Panhandle417 153 -0.9832 0.6733 -1.70945 -1.35516 -1.05565 -0.59287 -0.17034TKN (mg/L) NE-NC-Pen-BV 3053 716 -0.078 0.6005-0.73685 -0.36267 -0.02878 0.272575 0.590616NH3(mg/L) Panhandle432 168 -3.8099 0.9212 -4.83967 -4.4046 -3.9082 -3.37018 -2.90618NH3(mg/L) NE-NC-Pen-BV 3070 720 -3.2901 0.8493 -4.27856 -3.84872 -3.35899 -2.82754 -2.2563OrgN (mg/L) Panhandle407 153 -1.0882 0.6501 -1.82163 -1.44124 -1.16697 -0.66765 -0.23547OrgN (mg/L) NE-NC-Pen-BV 2959 707 -0.1606 0.6033 -0.81399 -0.44129 -0.10173 0.201359 0.507311TIN (mg/L) Panhandle418 162 -1.6997 1.1814 -3.2562 -2.53151 -1.74731 -0.87647 -0.13871TIN (mg/L) NE-NC-Pen-BV 2938 707 -1.9287 1.019-3.1485 -2.68879 -2.02119 -1.24331 -0.55262TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh WatersB6-6Table B6-2. Distributional StatisticsComputed from the Natural Logarithm Transformed All Streams DataObservationsDistributional Statistics Estimated from LN Transformed DataParameterFDEP NutrientRegionNumberof WBIDYearsNumberofWBIDsMean LNStd DevLN10th%tileLN25th%tileLN50th%tileLN75th%tileLN90th%tileLNBone Valley 128 375 0.6921 1.5871 -0.8557 -0.6931 0.3365 1.6752 3.0910North Central 42 77 -0.4064 1.0975 -0.8557 -0.8557 -0.8557 -0.2231 0.8107Northeast 106 302 0.7960 1.5322 -0.8557 -0.6931 0.6864 1.9364 2.8951Panhandle 150 360 0.1228 1.0592 -0.8557 -0.8557 -0.1625 0.9163 1.2781Corrected Chl. a(μg/L)Peninsula 366 1221 1.2804 1.6974 -0.8557 -0.3567 1.2940 2.7726 3.4770Panhandle 150 360 0.1228 1.0592 -0.8557 -0.8557 -0.1625 0.9163 1.2781Corrected Chl. a(μg/L)NE-NC-Pen-BV 642 1975 1.0494 1.6786 -0.8557 -0.6931 0.8755 2.4849 3.3585Bone Valley 74 321 1.5383 1.5054 -0.3567 0.4055 1.3610 2.5802 3.6507North Central 24 72 -0.2869 1.2013 -1.7720 -1.0498 -0.4620 0.4700 1.3191Northeast 31 183 1.2276 1.5247 -0.6931 0.0062 1.4294 2.4169 3.1407Panhandle 54 104 0.9944 0.58480.9163 0.9163 0.9163 0.9163 1.0986Chl. a (μg/L)Peninsula 229 1029 1.5916 1.9983 -0.6931 0.4054 1.9315 3.0972 3.7057Panhandle 54 104 0.9944 0.58480.9163 0.9163 0.9163 0.9163 1.0986Chl. a (μg/L)NE-NC-Pen-BV 358 1605 1.4472 1.8796 -0.6931 0.2401 1.6177 2.9147 3.6066TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh WatersB6-7Table B6-3. Distributional Statistics Computed from the Back Transformed Results of the All Streams DataParameter Region 10th%tile 25th%tile 50th%tile 75th%tile 90th%tileDistribution Statistics Computed from theTheoretical Lognormal Distribution ParametersTP (mg/L)Bone Valley 0.141 0.236 0.419 0.743 1.244NorthCentral0.049 0.094 0.192 0.392 0.746Northeast0.032 0.053 0.091 0.158 0.259Panhandle0.009 0.017 0.033 0.064 0.116Peninsula0.044 0.070 0.115 0.189 0.297Empirically Computed Distribution StatisticsBoneValley0.158 0.227 0.384 0.700 1.379NorthCentral0.058 0.097 0.173 0.316 0.737Northeast0.038 0.056 0.086 0.135 0.198Panhandle0.010 0.015 0.034 0.053 0.129Peninsula0.049 0.072 0.108 0.168 0.300Distribution Statistics Computed from theTheoretical Lognormal Distribution ParametersPanhandle0.302 0.435 0.652 0.978 1.407NE-NC-Pen-BV0.671 0.877 1.182 1.594 2.085Empirically Computed Distribution StatisticsPanhandle0.305 0.452 0.653 0.897 1.367TN (mg/L)NE-NC-Pen-BV 0.705 0.906 1.161 1.525 2.038Distribution Statistics Computed from theTheoretical Lognormal Distribution ParametersPanhandle0.015 0.039 0.112 0.321 0.826NE-NC-Pen-BV0.011 0.026 0.068 0.173 0.402Empirically Computed Distribution StatisticsPanhandle0.010 0.045 0.134 0.359 0.740NOx(mg/L)NE-NC-Pen-BV 0.012 0.023 0.061 0.186 0.467Distribution Statistics Computed from theTheoretical Lognormal Distribution ParametersPanhandle0.158 0.238 0.374 0.589 0.887NE-NC-Pen-BV0.428 0.617 0.925 1.387 1.997Empirically Computed Distribution StatisticsPanhandle0.181 0.258 0.348 0.553 0.843TKN (mg/L)NE-NC-Pen-BV 0.479 0.696 0.972 1.313 1.805TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh WatersB6-8Parameter Region 10th%tile 25th%tile 50th%tile 75th%tile 90th%tileDistribution Statistics Computed from theTheoretical Lognormal Distribution ParametersPanhandle0.007 0.012 0.022 0.041 0.072NE-NC-Pen-BV0.013 0.021 0.037 0.066 0.111Empirically Computed Distribution StatisticsPanhandle0.008 0.012 0.020 0.034 0.055NH3(mg/L)NE-NC-Pen-BV 0.014 0.021 0.035 0.059 0.105Distribution Statistics Computed from theTheoretical Lognormal Distribution ParametersPanhandle0.146 0.217 0.337 0.522 0.775NE-NC-Pen-BV0.393 0.567 0.852 1.279 1.845Empirically Computed Distribution StatisticsPanhandle0.162 0.237 0.311 0.513 0.790OrgN(mg/L)NE-NC-Pen-BV 0.443 0.643 0.903 1.223 1.661Distribution Statistics Computed from theTheoretical Lognormal Distribution ParametersPanhandle0.040 0.082 0.183 0.405 0.831NE-NC-Pen-BV0.039 0.073 0.145 0.289 0.536Empirically Computed Distribution StatisticsPanhandle0.039 0.080 0.174 0.416 0.870TIN (mg/L)NE-NC-Pen-BV 0.043 0.068 0.132 0.288 0.575TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh WatersB6-9Table B6-4. Distributional Statistics Computed from the Back Transformed Results of the All Streams DataDistribution Statistics Computed fromthe Theoretical Lognormal DistributionParametersParameter Region10th%tile 25th%tile 50th%tile 75th%tile 90th%tileBoneValley 0.261 0.685 1.998 5.827 15.272NorthCentral 0.163 0.318 0.666 1.396 2.719Northeast 0.311 0.789 2.217 6.230 15.793Panhandle 0.291 0.553 1.131 2.310 4.394Corrected Chl. a (μg/L)Peninsula 0.409 1.145 3.598 11.305 31.681Panhandle 0.291 0.553 1.131 2.310 4.394Corrected Chl. a (μg/L)NE-NC-Pen-BV 0.332 0.921 2.856 8.860 24.548BoneValley 0.676 1.687 4.657 12.854 32.058NorthCentral 0.161 0.334 0.751 1.688 3.500Northeast 0.484 1.220 3.413 9.545 24.085Panhandle 1.278 1.822 2.703 4.010 5.719Chl. a (μg/L)Peninsula 0.379 1.276 4.912 18.905 63.594Panhandle 1.278 1.822 2.703 4.010 5.719Chl. a (μg/L)NE-NC-Pen-BV 0.382 1.197 4.251 15.104 47.276TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh WatersB6-10Table B6-5. Comparison of Distributional Statistics from the All Streams Dataand Alternative Benchmark Distribution ScenariosTheoretical Percentiles Computedfrom Mean LN and Std Dev LN fromAll Streams DataFDEPcalculationfromBenchmark_Regions_051109.xlsxScenario 1:All 4 outlierWBIDsremoved(1653_,1807c_1811_, and3401_)Scenario 2: 2outlier WBIDsremoved(1653_ and3401_); 1807c_and 1811_retained inBone ValleyScenario 3:BenchmarkWBID-yeardistributions,WBID 1653removed.All Streams25th%tile /Scenario 3Benchmark75thand 90th%tileParameter Region10th%tile25th%tile50th%tile75th%tile90th%tile75th%tile90th%tile75th%tile90th%tile75th%tile90th%tile75th%tile90th%tile75th%tile90th%tileTP (mg/L)Bone Valley0.1410.2360.4190.7431.2440.751.1680.340.4510.410.5590.410.55957%42%North Central0.0490.0940.1920.3920.7460.2350.3590.2160.3220.2160.3220.2350.35940%26%Northeast0.0320.0530.0910.1580.2590.0660.1010.0660.1010.0660.1010.0660.10180%52%Panhandle0.0090.0170.0330.0640.1160.0430.0690.0430.0690.0430.0690.0430.06939%25%Peninsula0.0440.0700.1150.1890.2970.0880.1160.0880.1160.0880.1160.0880.11679%60%TN (mg/L)Panhandle0.3020.4350.6520.9781.4070.630.820.630.820.630.820.630.8269%53%NE-NC-Pen-BV0.6710.8771.1821.5942.0851.311.731.311.731.311.731.311.7267%51%TIN (mg/L)Panhandle0.0400.0820.1830.4050.8310.180.290.180.290.180.290.180.2946%28%NE-NC-Pen-BV0.0390.0730.1450.2890.5360.130.200.130.190.130.200.130.1958%38%Panhandle0.1460.2170.3370.5220.7750.450.6848%32%OrgN (mg/L)NE-NC-Pen-BV0.3930.5670.8521.2791.8451.121.4951%38%Panhandle0.0150.0390.1120.3210.8260.150.3126%13%NOx(mg/L)NE-NC-Pen-BV0.0110.0260.0680.1730.4020.070.1437%18%Bone Valley0.2610.6852.005.8315.3North Central0.1630.3180.6661.402.72Northeast0.3110.7892.226.2315.8Panhandle0.2910.5531.132.314.34CorrectedChl. a (μg/L)Peninsula0.4091.153.6011.331.7Panhandle0.2910.5531.132.314.40CorrectedChl. a (μg/L)NE-NC-Pen-BV0.3320.9212.868.8624.5

# TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



# B6-11 Figure B6-1. TP distributional statistics for the Bone Valley and North Central Regions.

Figure B6-2. TP distributional statistics for the Northeast, Panhandle, and Peninsula Regions.

# TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



# B6-12 Figure B6-3. TN distributional statistics for the Panhandle Region and the combined NortheastNorth Central-Peninsul a-Bone Valley Region.