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



# Appendix B-7: Distribution Statisti cs for Streams and Rivers Using U.S. EPA's Nutrient Watershed RegionsTSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



### B7-1 

## Appendix B-7. Distribution Statistics for Streams and Rivers Using U.S. EPA's Nutrient Watershed Regions
The United States Environmental Protection Agency’s (U.S. EPA) Nutrient Criteria Technical Guidance Manual: Rivers and Streams (USEPA 2000) describes se veral general approaches, with certain options, that can be used to devel op numeric nutrient criteria for streams. One line of evidence, referred to as the reference condition approach, for developing candidate endpoints is to evaluate distributional statis tics from benchmark sites, typi cally using the higher end of the distribution (e.g., 75 th 

### percentile, 90 th 

### percentile). Another line of evidence is to evaluate data from all sites, not simply benchmark sites, wh ere it is most common to emphasize the lower end of the distribution (e.g., 25 th 

### percentile). For further informati on and justification for the use of the reference condition approach, se e the introduction of Appendix B6.

This appendix documents the U.S. EPA’s analyses of benchmark sites and all stations using U.S. EPA nutrient regions 1 

### . Although the 25 th 

### and 75 th 

### percentiles were the recommended and most commonly considered percentiles in U.S. EPA gu idance, numerous percentiles are presented in this document for consideration as they might be used for other purposes. This appendix also provides a comparison of dissolved oxyge n (DO) data to 3 mg/L and 5 mg/L.



## Data Processing Steps
The overall approach was to generally replicate the approach that had been implemented by the Florida Department of Environmental Protecti on (FDEP) in previous analyses used for evaluating benchmark sites including data aggreg ation, computational approaches, and the like.

 FDEP provided an update to the All Streams da ta to EPA. The updated data addressed an error with DO data (the previous DO analysis found that DO % saturation was mixed with DO concentration data). That data set also incl udes sample time and temperature. This file contains 270,024 records for 8,614 sites—many of the additional records are associated with water temperature samples with no correspond ing nutrient data. FDEP also provided a supplemental data set for agency 21FLGW that included 16,971 records.

 Under the analyses described in Appendix B 6, each site had been attributed with a corresponding waterbody ID (WBID) . In a related analysis, U.S. EPA developed a revised set of nutrient regions, corresponding more consistently to draina ge basins and assigned each WBID to an U.S. EPA nutrient region. With th is information, each site was attributed to an U.S. EPA nutrient region.

 Total nitrogen (TN) was comput ed as the sum of nitrite (NO 2 

### ) plus nitrate (NO 3 

### ) and Total Kjeldahl Nitrogen (TKN) only when both component parameters were reported. Chl. a data are for corrected chl. a

.

1 U.S. EPA conducted a statistical distribution analysis for 3 Nutrient Watershed Regions (NWR s - Panhandle, Peninsula, and Bone Valley). Since that analysis, U.S. EPA identified a fourth NWR (North Central) and is proposing a regionalization scheme reflecting those 4 NWRs. A statistical distribution analysis fo r the 4 NWRs would re flect the same approach taken for the 3 NWRs.TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



### B7-2  One of the FDEP outlier analysis steps for benchmark sites was to remove observations greater than the upper adjacent value. 2 

### This approach was abandoned in lieu of a simple screening threshold to remove erroneous data. The screen ing thresholds of 15 mg/L total phosphorus (TP), 100 mg/L TN, 1,000 mg/L chlor ophyll, and 20 mg/L DO were selected. A total of 115 samples were removed from further consideration. Further justification of this screening approach is provided in Appendix B6.

 Upon filtering the data for sites within one of th e U.S. EPA nutrient regions and having data of interest (i.e., TN, TP, DO, or chlorophyll) , 89,672 samples remained. The DO results from these samples are used in the Dissolved Oxygen Comparison to 3 mg/L and 5 mg/L section of this appendix.

 Data were organized by Region- WBID-Year and observation counts were made in a manner identical to that used by FDEP’s analysis of benchmark sites. That is, whenever the TP observation count for a particular Region-WBID-Year was less than four, all TP observations for that Region-WBID-Year were dropped. A si milar process for TN, DO, and chlorophyll was implemented.

 TP, TN, and chlorophyll paramete rs were transformed by taki ng the natural logarithm (e.g., LN(TP), LN(TN)). Log transformation converts data that are positively skewed to more symmetrically (closer to normally) distribute d data. DO data from benchmark sites were reviewed for distribution. It was found that DO data did not follow a log-normal distribution, and were therefore not transformed. 3



###  The mean of transformed TN, TP, and chlorophy ll data and raw DO data were computed for each Region-WBID-Year. The values resulting fro m these data processing steps are used in the distribution statistics portion of this report.



## DO Comparison to 3 mg/L and 5 mg/L
Using the raw DO data, the number of samples w ith observations less than 3 mg/L and 5 mg/L were computed. Also, the number of WBIDs with at least one obs ervation less than 3 mg/L and 5 mg/L were computed. Table B7-1 presents th e results for benchmark and non-benchmark sites, organized by U.S. EPA nutrient region. Figures B7-1 present B7-2 these results graphically. The following observations are made:

 At benchmark sites, from 20% to 28% of DO ob servations were less than 5 mg/L by U.S. EPA nutrient region. Overall, 25% of benchmar k DO observations were less than 5 mg/L. At non-benchmark sites, 16% of Panhandle observations were less than 5 mg/L, while the other two regions ranged from 38% to 39%. Overal l, 36% of non-benchmar k DO observations were less than 5 mg/L.

 At benchmark sites, from 4% to 11% of DO ob servations were less than 3 mg/L by U.S. EPA nutrient region. Overall, 8% of benchmark DO observations were less than 3 mg/L. At nonbenchmark sites, 6% of Panhandle observations were less than 3 mg/L while the other two

2 The upper adjacent value is defined as th e largest observation that is less than or equal to the upper quartile plus 1.5 x Interquartile Range.
3 The raw DO data at benchmark sites had an Anderson-Darling test statis tic of 20.3 while the natural logarithm transformed data had an Anderson-Darling test stat istic of 431.2. The data were not normally or log-normally dist ributed; however, the raw data deviated less; thus the DO data were processed without transformation.TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



### B7-3 regions ranged from 16% to 17%. Overall, 15 % of non-benchmark DO observations were less than 3 mg/L.

 At benchmark WBIDs, 100%, 61%, and 95% of WBIDs from the Bone Valley, Panhandle, and Peninsula respectively had at least one observation less than 5 mg/L, overall 82% of benchmark WBIDs had at least one observation less than 5 mg/L. At non-benchmark WBIDs, 83%, 43%, and 86% of WBIDs from the Bone Va lley, Panhandle, and Peninsula respectively had at least one observation le ss than 5 mg/L, overall 74% of non-benchmark WBIDs had at least one observation less than 5 mg/L.

 At benchmark WBIDs, 60%, 35%, and 78% of WB IDs from the Bone Valley, Panhandle, and Peninsula respectively had at least one obs ervation less than 3 mg /L, overall 61% of benchmark WBIDs had at least one observation less than 3 mg/L. At non-benchmark WBIDs, 67%, 26%, and 68% of WBIDs from the Bone Va lley, Panhandle, and Peninsula respectively had at least one observation le ss than 3 mg/L, overall 57% of non-benchmark WBIDs had at least one observation less than 3 mg/L.



## Distribution Statistics
Using the Region-WBID-Year mean of the na tural logarithm tran sformed TP, TN, and chlorophyll data and the Region-WBID-Year mean of the raw DO that were computed as described in the Data Processing Steps section of this document, the mean and standard deviation were estimated by regi on and across all regions. These su mmary statistics were used to compute theoretical distributions assuming a lo gnormal distribution for TP, TN, and chlorophyll and a normal distribution for DO (see Tables B7 -2 through B7-5). These distributions were plotted in Figures B7-3 through B7-6. The following results were observed:

Total Phosphorus

 At all sites, the 25 th 

### percentile TP for the Bone Valley, Panhandle, and Peninsula nutrient regions was 0.174 mg/L, 0.018 mg/L, and 0.068 mg/L. Across all regions, the 25 th 

### percentile TP at all sites was 0.059 mg/L.

 At benchmark sites, the 75 th 

### percentile TP for the Bone Valley, Panhandle, and Peninsula nutrient regions was 0.643 mg/L, 0.063 mg/L, and 0.178 mg/L. Across all regions, the 75 th 

### percentile TP at benchm ark sites was 0.149 mg/L.

Total Nitrogen

 At all sites, the 25 th 

### percentile TN for the Bone Valley, Panhandle, and Peninsula nutrient regions was 0.97 mg/L, 0.45 mg/L, and 0.88 mg/L. Across all regions, the 25 th 

### percentile TN at all sites was 0.79 mg/L.

 At benchmark sites, the 75 th 

### percentile TN for the Bone Valley, Panhandle, and Peninsula nutrient regions was 1.20 mg/L, 0.76 mg/L, and 1.36 mg/L. Across all regions, the 75 th 

### percentile TN at benchm ark sites was 1.19 mg/L.TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



### B7-4 Chlorophyll

 At all sites, the 25 th 

### percentile chlorophyll for the B one Valley, Panhandle, and Peninsula nutrient regions was 0.98 μg/L, 0.60 μg/L, and 1.08 μg/L. Across all regions, the 25 th 

### percentile chlorophyll at all sites was 0.92 μg/L.

 At benchmark sites, the 75 th 

### percentile chlorophyll for the Bone Valley, Panhandle, and Peninsula nutrient regions was 1.78 μg/L, 1.33 μg /L, and 1.52 μg/L. Across all regions, the 75 th 

### percentile chlorophyll at benchmark sites was 1.47 μg/L.

Dissolved Oxygen

 At all sites, the 25 th 

### percentile DO for the Bone Valley, Panhandle, and Peninsula nutrient regions was 4.55 mg/L, 5.54 mg/L, and 4.41 mg/L. Across all regions, the 25 th 

### percentile DO at all sites was 4.56 mg/L.

 At benchmark sites, the 75 th 

### percentile DO for the Bone Valley, Panhandle, and Peninsula nutrient regions was 7.19 mg/L, 7.75 mg/L, and 6.89 mg/L. Across all regions, the 75 th 

### percentile DO at benchmark sites was 7.19 mg/L.



## Quality Control Check

Raw data from benchmark sites in the Bone Valley were extracted from the database. Distribution statistics for the da ta were computed using a separate procedure and found to be consistent with those computed from the primary algorithms used to prepare the results presented in this document.TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



### B7-5 Table B7-1. Number of DO Observ ations Less than 3 mg/L or 5 mg/L and WBIDs with at Least One Observation Less than 3 or 5 mg/L , organized by U.S. EPA Nutrient Region

Benchmark Sites/WBIDs
DO Observations WBIDs U.S. EPA Nutrient Region Total Observations Observations < 5 mg/L % Observations < 5 mg/L Total WBIDs WBIDs with one observ.

< 5 mg/L % WBIDs with one observ. < 5 mg/L Bone Valley 294 62 21% 5 5 100% Panhandle 3,712 746 20% 51 31 61%
Peninsula 5,375 1,527 28% 76 72 95%
Total 9,381 2,335 25% 132 108 82%
Non-benchmark Sites/WBIDs
DO Observations WBIDs

U.S. EPA Nutrient Region Total Observations Observations < 5 mg/L % Observations < 5 mg/L Total WBIDs WBIDs with one observ.

< 5 mg/L % WBIDs with one observ. < 5 mg/L Bone Valley 13,222 5,184 39% 332 275 83% Panhandle 8,105 1,301 16% 424 181 43% Peninsula 47,989 18,283 38% 844 722 86%
Total 69,316 24,768 36% 1,600 1,178 74%
Benchmark Sites/WBIDs
DO Observations WBIDs

U.S. EPA Nutrient Region Total Observations Observations < 3 mg/L % Observations < 3 mg/L Total WBIDs WBIDs with one observ.

< 3 mg/L % WBIDs with one observ. < 3 mg/L Bone Valley 294 13 4% 5 3 60% Panhandle 3,712 151 4% 51 18 35%
Peninsula 5,375 597 11% 76 59 78%
Total 9,381 761 8% 132 80 61%
Non-benchmark Sites/WBIDs
DO Observations WBIDs

U.S. EPA Nutrient Region Total Observations Observations < 3 mg/L % Observations < 3 mg/L Total WBIDs WBIDs with one observ.

< 3 mg/L % WBIDs with one observ. < 3 mg/L Bone Valley 13,222 2,237 17% 332 223 67% Panhandle 8,105 470 6% 424 112 26% Peninsula 47,989 7,512 16% 844 578 68%
Total 69,316 10,219 15% 1,600 913 57%TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh WatersB7-6Table B7-2. Distributional Statistics Computed from the Natural Logarithm Transformed TP DataObservations DistributionStatisticsEstimated fromNatural Logtransformed DataPercentiles Computed from Mean and StandardDeviation Back Transformed to Regular UnitsParameterU.S. EPANutrient RegionNumber ofWBIDYearsNumber ofWBIDsMean Std Dev10th%tile25th%tile50th%tile75th%tile90th%tileBone Valley 739 194 -1.1240 0.9289 0.099 0.174 0.325 0.608 1.069Panhandle 600 190 -3.2549 1.1335 0.009 0.018 0.039 0.083 0.165Peninsula 2,915 634 -2.12350.8336 0.041 0.068 0.120 0.210 0.348TPatAll SitesAll Regions 4,254 1,018 -2.1095 1.0774 0.030 0.059 0.121 0.251 0.483Bone Valley 21 5 -1.0155 0.8505 0.122 0.204 0.362 0.643 1.077Panhandle 198 51 -3.3516 0.8715 0.011 0.019 0.035 0.063 0.107Peninsula 407 75 -2.3196 0.8802 0.032 0.054 0.098 0.178 0.304TP atBenchmarkSitesAll Regions 626 131 -2.60231.0394 0.020 0.037 0.074 0.149 0.281Table B7-3. Distributional Statistics Computed from the Natural Logarithm Transformed TN DataObservations DistributionStatisticsEstimated fromNatural Logtransformed DataPercentiles Computed from Mean and StandardDeviation Back Transformed to Regular UnitsParameterU.S. EPANutrient RegionNumber ofWBIDYearsNumber ofWBIDsMean Std Dev10th%tile25th%tile50th%tile75th%tile90th%tileBone Valley 627 182 0.2534 0.4174 0.75 0.97 1.29 1.71 2.20Panhandle 546 166 -0.3793 0.6328 0.30 0.45 0.68 1.05 1.54Peninsula 2,684 593 0.1737 0.4406 0.68 0.88 1.19 1.60 2.09TNatAll SitesAll Regions 3,857 941 0.1084 0.5099 0.58 0.79 1.11 1.57 2.14Bone Valley 16 5 0.0489 0.1949 0.82 0.92 1.05 1.20 1.35Panhandle 184 48 -0.6243 0.5185 0.28 0.38 0.54 0.76 1.04Peninsula 372 74 0.0129 0.43550.58 0.76 1.01 1.36 1.77TN atBenchmarkSitesAll Regions 572 127 -0.19110.5474 0.41 0.57 0.83 1.19 1.67TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh WatersB7-7Table B7-4. Distributional Statistics Computed from the Natural Logarithm Transformed Chlorophyll DataObservations DistributionStatisticsEstimated fromNatural Logtransformed DataPercentiles Computed from Mean and StandardDeviation Back Transformed to Regular UnitsParameterU.S. EPANutrient RegionNumber ofWBIDYearsNumber ofWBIDsMean Std Dev10th%tile25th%tile50th%tile75th%tile90th%tileBone Valley 466 170 0.7504 1.1498 0.49 0.98 2.12 4.60 9.24Panhandle 458 172 0.0324 0.81010.37 0.60 1.03 1.78 2.92Peninsula 1,792 517 0.9672 1.3194 0.48 1.08 2.63 6.41 14.27ChlorophyllatAll SitesAll Regions 2,716 859 0.7724 1.2660 0.43 0.92 2.16 5.08 10.97Bone Valley 14 4 0.1487 0.6343 0.51 0.76 1.16 1.78 2.62Panhandle 123 34 -0.1972 0.7102 0.33 0.51 0.82 1.33 2.04Peninsula 201 66 -0.1911 0.9088 0.26 0.45 0.83 1.52 2.65ChlorophyllatBenchmarkSitesAll Regions 338 104 -0.17920.8324 0.29 0.48 0.84 1.47 2.43Table B7-5. Distributional Statistics Computed from the Untransformed DO DataObservations DistributionStatisticsEstimated fromUntransformed DataPercentiles Computed from Mean and StandardDeviation of Untransformed DataParameterU.S. EPANutrient RegionNumber ofWBIDYearsNumber ofWBIDsMean Std Dev10th%tile25th%tile50th%tile75th%tile90th%tileBone Valley 873 231 5.6296 1.5955 3.58 4.55 5.63 6.71 7.67Panhandle 654 193 6.7056 1.73274.49 5.54 6.71 7.87 8.93Peninsula 3,081 644 5.4887 1.6054 3.43 4.41 5.49 6.57 7.55DOatAll SitesAll Regions 4,608 1,068 5.68811.6747 3.54 4.56 5.69 6.82 7.83Bone Valley 22 5 6.2736 1.3584 4.53 5.36 6.27 7.19 8.01Panhandle 212 46 6.6771 1.58504.65 5.61 6.68 7.75 8.71Peninsula 443 74 5.9580 1.37444.20 5.03 5.96 6.89 7.72DO atBenchmarkSitesAll Regions 677 125 6.1935 1.4787 4.30 5.20 6.19 7.19 8.09TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



### B7-8

% Observations Total

Pen Pan BV

<>BM BM <>BM BM <>BM BM <>BM BM

40 30 20 10 0 40 30 20 10 0 < 3 mg/L < 5 mg/L



### Figure B7-1. Percent of benchmark (BM) a nd non-benchmark (<>BM) DO observations less than 3 mg/L and 5 mg/L organi zed by U.S. EPA nutrient region.

% WBIDs Total

Pen Pan BV

<>BM BM <>BM BM <>BM BM <>BM BM

10080604020 0 10080604020 0 < 3 mg/L < 5 mg/L



### Figure B7-2. Percent of benchmark (BM) and non- benchmark (<>BM) WBIDs with at least one DO observation less than 3 mg/L and 5 mg/L organized by U.S. EPA nutrient region.TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



### B7-9 0.0 0.3 0.6 0.9 1.2

0 10 20 30 40 50 60 70 80 90 100

PERCENTILESTP (MG/L) Bone Valley (All-Sites) Panhandle (All-Sites) Peninsula (All-Sites) All Regions (All-Sites) Bone Valley (Benchmark) Panhandle (Benchmark) Peninsula (Benchmark) All Regions (Benchmark)



### Figure B7-3. TP distribution statistics.

0.0 1.0 2.0 3.0

0 10 20 30 40 50 60 70 80 90 100

PERCENTILESTN (MG/L) Bone Valley (All-Sites) Panhandle (All-Sites) Peninsula (All-Sites) All Regions (All-Sites) Bone Valley (Benchmark) Panhandle (Benchmark) Peninsula (Benchmark) All Regions (Benchmark)



### Figure B7-4. TN distribution statistics.TSD for U.S. EPA’s Proposed Numeric Nutrient Criteria for FL Inland Surface Fresh Waters



### B7-10 0.0 3.0 6.0 9.0 12.0 15.0

0 10 20 30 40 50 60 70 80 90 100

PERCENTILESChlorophyll (UG/L) Bone Valley (All-Sites) Panhandle (All-Sites) Peninsula (All-Sites) All Regions (All-Sites) Bone Valley (Benchmark) Panhandle (Benchmark) Peninsula (Benchmark) All Regions (Benchmark)



### Figure B7-5. Chlorophyll di stribution statistics.

0.0 2.0 4.0 6.0 8.0 10.0

0 10 20 30 40 50 60 70 80 90 100

PERCENTILESDO (MG/L) Bone Valley (All-Sites) Panhandle (All-Sites) Peninsula (All-Sites) All Regions (All-Sites) Bone Valley (Benchmark) Panhandle (Benchmark) Peninsula (Benchmark) All Regions (Benchmark)



### Figure B7-6. DO distribution statistics.