International Stormwater Best Management Practices (BMP) Database Pollutant Category Statistical Summary Report Solids, Bacteria, Nutrients, and Metals

Prepared by Geosyntec Consultants, Inc. Wright Water Engineers, Inc. Under Support From Water Environment Research Foundation Federal Highway Administration Environment and Water Resources Institute of the American Society of Civil Engineers

December 2014

International Stormwater BMP Database

Disclaimer The BMP Database (“Database”) was developed as an account of work sponsored by the Water Environment Research Foundation (WERF), the American Society of Civil Engineers (ASCE)/Environmental and Water Resources Institute (EWRI), the American Public Works Association (APWA), the Federal Highway Administration (FHWA), and U.S. Environmental Protection Agency (USEPA) (collectively, the “Sponsors”). The Database is intended to provide a consistent and scientifically defensible set of data on Best Management Practice (“BMP”) designs and related performance. Although the individuals who completed the work on behalf of the Sponsors (“Project Team”) made an extensive effort to assess the quality of the data entered for consistency and accuracy, the Database information and/or any analysis results are provided on an “AS-IS” basis and use of the Database, the data information, or any apparatus, method, or process disclosed in the Database is at the user’s sole risk. The Sponsors and the Project Team disclaim all warranties and/or conditions of any kind, express or implied, including, but not limited to any warranties or conditions of title, non-infringement of a third party’s intellectual property, merchantability, satisfactory quality, or fitness for a particular purpose. The Project Team does not warrant that the functions contained in the Database will meet the user’s requirements or that the operation of the Database will be uninterrupted or error free, or that any defects in the Database will be corrected. UNDER NO CIRCUMSTANCES, INCLUDING CLAIMS OF NEGLIGENCE, SHALL THE SPONSORS OR THE PROJECT TEAM MEMBERS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES INCLUDING LOST REVENUE, PROFIT OR DATA, WHETHER IN AN ACTION IN CONTRACT OR TORT ARISING OUT OF OR RELATING TO THE USE OF OR INABILITY TO USE THE DATABASE, EVEN IF THE SPONSORS OR THE PROJECT TEAM HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. The Project Team’s tasks have not included, and will not include in the future, recommendations of one BMP type over another. However, the Project Team's tasks have included reporting on the performance characteristics of BMPs based upon the entered data and information in the Database, including peer reviewed performance assessment techniques. Use of this information by the public or private sector is beyond the Project Team’s influence or control. The intended purpose of the Database is to provide a data exchange tool that permits characterization of BMPs solely upon their measured performance using consistent protocols for measurements and reporting information. The Project Team does not endorse any BMP over another and any assessments of performance by others should not be interpreted or reported as the recommendations of the Project Team or the Sponsors.

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Acknowledgements Report Preparation 1 Primary Authors: Marc Leisenring, P.E., Geosyntec Consultants, Inc. Jane Clary, Wright Water Engineers, Inc. Paul Hobson, Geosyntec Consultants, Inc. Reviewers: Eric Strecker, P.E., Geosyntec Consultants, Inc. Jonathan Jones, P.E., D.WRE, Wright Water Engineers, Inc.

Project Information WERF Project Director: Theresa Connor, P.E., Water Environment Research Foundation Principal Investigators: Eric Strecker, P.E., Geosyntec Consultants, Inc. Jonathan Jones, P.E., D.WRE, Wright Water Engineers, Inc. Project Steering Committee: Susan Jones, P.E., Federal Highway Administration Christopher Kloss, P.E., Office of Water/Office of Science & Technology, U.S. Environmental Protection Agency Brian Parsons, P.E., Environmental and Water Resources Institute of American Society of Civil Engineers Marcel Tchaou, Ph.D., P.E., P.H., MBA, Federal Highway Administration Office of Project Development and Environmental Review Courtney Thompson, American Public Works Association Project Subcommittee: Michael E. Barrett, Ph.D., P.E., D.WRE, Center for Research in Water Resources, University of Texas Bob Carr, P.E., Gresham, Smith and Partners David R. Graves, CPESC, Environmental Science Bureau, New York State Dept. of Transportation Gregory E. Granato, U.S. Geological Survey Jesse Pritts, P.E., Engineering and Analysis Division Office of Water/Office of Science & Technology, U.S. Environmental Protection Agency

1

Contact Jane Clary ([email protected]) or Marc Leisenring ([email protected]) with questions regarding this summary.

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Table of Contents 1

INTRODUCTION .......................................................................................................... 1

2

DATA SUMMARY APPROACH...................................................................................... 2 2.1 2.2 2.3

3

BMPS ANALYZED AND DATA SCREENING APPROACH .................................................... 2 GRAPHICAL SUMMARIES ................................................................................................ 3 TABULAR SUMMARIES .................................................................................................... 3 SOLIDS ....................................................................................................................... 6

3.1 3.2 4

TOTAL SUPENDED SOLIDS ............................................................................................... 6 TOTAL DISSOLVED SOLIDS............................................................................................... 7 BACTERIA ................................................................................................................... 8

4.1 4.2 4.3 5

ENTEROCOCCUS .............................................................................................................. 8 ESCHERICHIA COLI ........................................................................................................... 9 FECAL COLIFORM .......................................................................................................... 10 METALS .................................................................................................................... 11

5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 6

ARSENIC......................................................................................................................... 11 CADMIUM ..................................................................................................................... 13 CHROMIUM ................................................................................................................... 15 COPPER ......................................................................................................................... 17 IRON .............................................................................................................................. 19 LEAD .............................................................................................................................. 21 NICKEL ........................................................................................................................... 23 ZINC ............................................................................................................................... 25 NUTRIENTS............................................................................................................... 27

6.1 6.2

PHOSPHORUS ................................................................................................................ 27 NITROGEN ..................................................................................................................... 30

7

REFERENCES ............................................................................................................. 35

8

ATTACHMENTS......................................................................................................... 35 Attachment 1. Attachment 2. Attachment 3. Attachment 4.

Solids Statistical Summary Report Bacteria Statistical Summary Report Metals Statistical Summary Report Nutrients Statistical Summary Report

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1 INTRODUCTION In 2010-2011, the Water Environment Research Foundation (WERF), Federal Highway Administration (FHWA), and the American Society of Civil Engineers’ Environmental and Water Resources Institute (EWRI) co-sponsored a comprehensive stormwater best management practice (BMP) performance analysis technical paper series relying on data contained in the International Stormwater BMP Database (BMPDB) . 2 This series included papers for solids, bacteria, nutrients, and metals, with each paper summarizing the regulatory context of the constituent category, primary sources, fate and transport processes, removal mechanisms, and statistical summaries of BMP performance for data contained in the BMPDB. In 2012, an update of the statistical summaries provided in that series was prepared to include the data from over 50 new studies added to the database in late 2011. This 2014 report is yet another update of the statistical summaries that includes additional study data entered into the database in 2013 and 2014. This report is not intended to replace the discussion and context provided in the previous technical papers; instead, this report provides updated statistical summaries only. Constituents summarized in this report are listed in Table 1. Table 1. Constituents Summarized by Pollutant Category Pollutant Category Solids Bacteria

Metals

Nutrients

Summarized Constituent Total suspended solids (TSS) Total dissolved solids (TDS) Fecal coliform Escherichia coli (E. coli) Enterococcus Arsenic (total and dissolved) Cadmium (total and dissolved) Chromium (total and dissolved) Copper (total and dissolved) Iron (total and dissolved) Lead (total and dissolved) Nickel (total and dissolved) Zinc (total and dissolved) Total phosphorus Orthophosphate Dissolved phosphorus Total nitrogen Total Kjeldahl nitrogen (TKN) Nitrate (NO3) Nitrate plus nitrite (NO3 + NO2) Nitrate and Nitrate plus nitrite (NOx)

2

The BMP Database is a long-term project that began in 1994 through the vision of members active in the Urban Water Resources Research Council of ASCE and the leadership of EPA. Funded for many years by EPA, the project is now supported by a coalition of partners including WERF, FHWA, EWRI and the American Public Works Association (APWA). The technical reports can be downloaded from www.bmpdatabase.org/BMPPerformance.htm.

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2 DATA SUMMARY APPROACH The BMP performance analyses provided in this report are based on the BMP performance data for selected pollutants in the BMPDB as of December 16, 2014. The analyses are based upon the distributions of influent and effluent water quality sample concentration data for individual events by BMP category, thereby providing greater weight to those BMPs for which there are a larger number of data points reported. In other words, the performance analysis presented in this technical summary is “storm-weighted,” as opposed to “BMP weighted.” 3 This update does not include BMP weighted analyses (i.e., analyses of individual study site central tendencies). A summary of the BMPs analyzed and data screening approach is provided below followed by descriptions of the graphical and tabular summaries provided in this report. The statistical attachments provide additional detailed analysis organized by constituent and BMP type for the three main constituent categories: Solids, Bacteria, Metals, and Nutrients. Data for other pollutants not included in this report may also be available and can be obtained from www.bmpdatabase.org.

2.1 BMPs Analyzed and Data Screening Approach The BMP categories included in this analysis are grass strips, bioretention, bioswales, composite/treatment train BMPs, detention basins (surface/grass-lined), media filters (mostly sand filters), porous pavement, retention ponds (surface pond with a permanent pool), wetland basins (basins with open water surface), a combined category including both retention ponds and wetland basins, and wetland channels (swales and channels with wetland vegetation). The effectiveness and range of unit treatment processes present in a particular BMP may vary depending on the BMP design. Several other BMP categories and sub-classes are included in the database, but these have been excluded from this analysis due to limited data sets available for meaningful categorical comparisons. Additionally, the BMPDB contains approximately 100 manufactured devices, which are no longer provided as a general BMP category for analysis in this report because of the wide range of unit treatment processes present among various manufactured devices. Green roof data sets have also been excluded from this report due to relatively small numbers of comparable data sets and significant variation in monitoring program designs. Individual BMP performance analysis reports can be viewed and downloaded from www.bmpdatabase.org for manufactured devices, green roofs, and other BMP types not included in this summary report. For example, see http://www.bmpdatabase.org/map.html to view monitoring locations with other BMP types not included in this report. To be included in this category-level summary, at least three BMP studies must be included in the BMP category, with each BMP study having influent and effluent data for at least three storms for the pollutant of interest. Additional data screening include the exclusion of base flow samples from BMP studies, exclusion of grab samples for BMPs without permanent pools (i.e., 3

There are several viable approaches to evaluating data in the BMP Database. Two general approaches that have been presented in the past (Geosyntec Consultants and Wright Water Engineers, 2008) are the “BMP-weighted” and “storm-weighted” approaches. The BMP-weighted approach represents each BMP with one value representing the central tendency and variability of each individual BMP study, whereas the storm-weighted approach combines all of the storm events for the BMPs in each category and analyzes the overall storm-based data set. The stormweighted approach has been selected for this report because it provides a much larger data set for analysis. Pollutant Category Statistical Summary Report December 2014

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only event mean concentrations (EMCs) are used except for retention ponds and wetland basins), and exclusion of studies with a gross imbalance in the number of inflow and outflow sample results. A variety of additional screening criteria are applied for purposes of category-level analysis to make sure that the data sets and BMP designs are reasonably representative, as documented in the “Monitoring Station” table of the BMP Database, which can be downloaded from www.bmpdatabase.org. Poor performance of a BMP is not a reason for data exclusion.

2.2 Graphical Summaries In the subsections below, side-by-side box plots for the various BMPs measurements have been generated using the influent and effluent concentrations from the studies. For each BMP category, the influent box plots are provided on the left and the effluent box plots are provided on the right. A key to the box plots is provided in Figure 1. Figure 1. Box Plot Key

2.3 Tabular Summaries In addition to the box plots, tables of influent/effluent medians, 25th and 75th percentiles, and number of studies and data points are provided, along with 95% confidence intervals about the medians. The median and interquartile ranges were selected as descriptive statistics for BMP performance because they are non-parametric (do not require distributional assumptions for the underlying data set) and are less affected by extreme values than means and standard deviations. Additionally, the median is less affected by assumptions regarding values below detection limits and varying detection limits for studies conducted by independent parties over many years.

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Since confidence intervals about the median can still be affected by outliers if simple substitution is used, a robust regression-on-order statistics (ROS) method as described by Helsel and Cohn (1988) was utilized to provide probabilistic estimates of non-detects before computing descriptive statistics. Despite use of this robust method, conclusions regarding BMP performance should carefully consider the influence of large percentages of non-detects. For example, pollutant removals may be found to be statistically insignificant for a BMP, but that BMP may still provide removals at higher influent concentrations. The number of influent and effluent non-detects should be reviewed before making conclusions, particularly for dissolved metals where non-detects are most prevalent. The number of non-detects are tabulated for each BMP/constituent combination in the associated attachments. For more information on the influence of non-detects on dissolved metals data in the BMP Database, see the discussion in the Metals Technical Summary (Wright Water Engineers and Geosyntec, 2011), accessible at www.bmpdatabase.org). Confidence intervals in the boxplots and tables were generated using the bias corrected and accelerated (BCa) bootstrap method described by Efron and Tibishirani (1993). This method is a robust approach for computing confidence intervals that is resistant to outliers and does not require any restrictive distributional assumptions.4 Comparison of the confidence intervals about the influent and effluent medians can be used to roughly identify statistically significant differences between the central tendencies of the data. However, non-parametric hypothesis tests, such as the Mann-Whitney rank sum test or the Wilcoxon signed-rank test, can provide additional and more robust results for evaluating significant differences between medians. The Mann-Whitney test applies to independent data sets, whereas the Wilcoxon test applies to paired data sets (Helsel and Hirsch, 1992). Results of these tests are provided in the attached statistical summary reports for solids, bacteria, metals, and nutrients. In some cases, the Mann-Whitney and Wilcoxon hypothesis test results produce conflicting conclusions regarding statistically significant differences. Such cases are more likely to occur where there are imbalances in the number of influent and effluent samples for a particular data set because the Mann-Whitney test operates on the entire data set whereas the Wilcoxon test only operates on data pairs. For BMPs with short residence times and limited storage, the Wilcoxon hypothesis test results may be more reliable for evaluating whether concentration reductions are statistically significant because the test operates on the individual paired differences of influent and effluent storm event mean (EMC) concentrations. For BMPs with long residence times and/or permanent pools (e.g., wet ponds), the paired storm event hypothesis test results relying on the Wilcoxon test may be less reliable than the Mann-Whitney test because of variations in sampling program designs for collection of influent and effluent samples that may not enable accurate event-based pairing of monitoring data. For example, inflow for a storm event on a particular date may mix with water from a previous event that has been stored since the previous storm. Thus, in cases where the Mann-Whitney and Wilcoxon test results conflict for BMPs with permanent pools, the MannWhitney results may provide a better indicator of pollutant removal performance. In the summary tables which follow, effluent values in bold green indicate the upper 95% confidence interval of the effluent median is less than the lower 95% confidence interval of the 4

Due to random statistical sampling that is conducted as part of the BCa method, insignificant variations in the calculated statistical result values may occur, causing minor inconsistencies between the values presented in the attachments relative to the tables presented in the main body of the report.

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influent median. Effluent values in red bold italics indicate the lower 95% confidence interval of the effluent median is greater than the upper 95% confidence interval of the influent median. Values are also footnoted to indicate whether the hypothesis test results presented in the attachments indicate statistically significant differences. Be aware that for some BMP types, a statistically significant difference between influent and effluent concentrations may not be present, but the effluent concentrations achieved by the BMP are relatively low and may be comparable to the performance of other BMPs that have statistically significant differences between inflow and outflow. For example, data sets that have low influent concentrations and similarly low effluent concentration (i.e., clean water in = clean water out) may not show statistically significant differences. However this does not necessarily imply that the BMP would not have been effective at higher influent concentrations. Lastly, this report focuses soley on influent and effluent concentrations and does not characterize influent and effluent loads. For BMPs that provide significant volume reduction, load reductions may still occur in the absence of concentration reductions. Volume-related data can also be retrieved from the BMPDB and have been evaluated in detail for some BMP categories. For example, see International Stormwater Best Management Practices (BMP) Database Addendum 1 to Volume Reduction Technical Summary (January 2011) Expanded Analysis of Volume Reduction in Bioretention BMPs (Geosyntec and Wright Water Engineers 2012), accessible at www.bmpdatabase.org.

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3 SOLIDS 3.1 Total Supended Solids Figure 2. Box Plots of Influent/Effluent TSS Concentrations

Table 2. Influent/Effluent Summary Statistics for TSS (mg/L) BMP Type

Count of Studies and EMCs In 19; 361 23; 399 22; 461 10; 202 22; 321 23; 381 8; 356 56; 923 19; 395

Out 19; 282 23; 346 22; 393 10; 174 22; 336 23; 358 8; 220 56; 933 19; 385

25th Percentile In 20.0 9.0 18.0 42.4 21.0 21.1 35.0 15.0 11.0

Out 10.0 10.0 4.9 8.0 10.0 3.0 14.0 4.3 3.5

Median (95% Conf. Interval)* In 44.1 (39, 48) 27.7 (21, 31.6) 38.1 (31, 42) 87.6 (75.1, 101.5) 68.2 (52.3, 77.3) 50.9 (42.8, 58) 90.3 (69, 115) 47.7 (40, 54) 24.5 (19.1, 28.9)

Out 19 (15.9, 21)** 21.6 (17.8, 24)** 9.9 (7, 10)** 18.4 (14, 19.3)** 23.3 (19.5, 26)** 8.4 (6.3, 9.8)** 24.9 (21.5, 27)** 11.5 (10, 12.3)** 9.4 (7.4, 11)**

Biofilter - Grass Strip Biofilter - Grass Swale Bioretention Composite Detention Basin Media Filter Porous Pavement Retention Pond Wetland Basin Wetland 75; 1318 75; 1318 13.3 4.0 37.9 (34, 41.6) 10.9 (9.6, 11.7)** Basin/Retention Pond 8; 171 8; 151 12.0 8.0 18.9 (16, 21) 14.4 (10, 16)** Wetland Channel NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 1 shows statistically significant decreases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

75th Percentile In 90.0 67.0 86.0 178.8 128.0 110.5 230.0 139.8 63.3

Out 35.0 43.0 20.0 36.5 47.0 19.9 44.4 28.0 20.6

110.0

25.4

47.5

27.0

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3.2 Total Dissolved Solids Figure 3. Box Plots of Influent/Effluent TDS Concentrations

Table 3. Influent/Effluent Summary Statistics for TDS (mg/L) BMP Type Biofilter - Grass Strip Biofilter - Grass Swale Bioretention Composite Detention Basin Media Filter

Count of Studies and EMCs In 11; 208 12; 112 NA NA 6; 69 13; 186

Out 11; 147 12; 89 NA NA 6; 55 13; 174

25th Percentile In 24.0 41.5 NA NA 70.0 24.5

Out 58.0 33.0 NA NA 66.0 44.0

Median (95% Conf. Interval)* In 47.9 (40, 53) 70.2 (60, 77.4) NA NA 105 (74.5, 120) 46 (35.8, 52.5)

Out 91.5 (76, 98)*** 65.9 (52, 77) NA NA 99.5 (76, 114.1) 77.7 (63.2, 91.8)***

NA NA NA NA NA NA Porous Pavement 15; 165 15; 144 68.0 72.3 119.2 (99.3, 130) 169.3 (138.6, 183)*** Retention Pond 2; 24 2; 18 67.3 143.5 112.9 (74, 157.8) 197.6 (80, 258)*** Wetland Basin Wetland 17; 189 17; 162 68.0 76.1 118.8 (97, 127.2) 170.2 (142.6, 182.5)*** Basin/Retention Pond NA NA NA NA NA NA Wetland Channel NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). ***Hypothesis testing in Attachment 1 shows statistically significant increases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

75th Percentile In 80.0 87.3 NA NA 150.0 82.2

Out 134.0 92.0 NA NA 129.9 134.0

NA

NA

176.1 168.8

303.8 292.0

176.1

303.3

NA

NA

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4 BACTERIA 4.1 Enterococcus Figure 4. Box Plots of Influent/Effluent Enterococcus Concentrations

Table 4. Influent/Effluent Summary Statistics for Enterococcus (#/100 mL) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

In Out In Out In Out Biofilter - Grass Strip NA NA NA NA NA NA Biofilter - Grass Swale NA NA NA NA NA NA Bioretention 3; 48 3; 49 178 32 601 (225, 922) 235 (58, 437)** Composite NA NA NA NA NA NA Detention Basin NA NA NA NA NA NA Media Filter NA NA NA NA NA NA Porous Pavement NA NA NA NA NA NA Retention Pond NA NA NA NA NA NA Wetland Basin 4; 53 4; 53 227 30 997 (250, 1605) 390 (100, 630)** Wetland 6; 86 6; 86 207 20 869 (354, 1457) 196 (80, 388)** Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 1 shows statistically significant decreases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

75th Percentile In NA NA 2437 NA NA NA NA NA 3973

Out NA NA 2187 NA NA NA NA NA 1842

4263

1651

NA

NA

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4.2 Escherichia coli Figure 5. Box Plots of Influent/Effluent E. coli Concentrations

Table 5. Influent/Effluent Summary Statistics for E. coli (#/100 mL) BMP Type

Count of Studies and EMCs

25th Percentile

Biofilter - Grass Strip Biofilter - Grass Swale Bioretention Composite Detention Basin Media Filter Porous Pavement

In NA 5; 39 4; 61 NA NA NA NA

Out NA 5; 39 4; 61 NA NA NA NA

In NA 411 44 NA NA NA NA

Out NA 1200 6.0 NA NA NA NA

Retention Pond

4; 69

4; 65

582

10

Median (95% Conf. Interval)* Out NA 4182 (1200, 5900) 101 (9, 213)** NA NA NA NA

In NA 11000 2400 NA NA NA NA

Out NA 10000 2400 NA NA NA NA

100 (24, 172)**

5500

697

Wetland Basin 5; 60 5; 59 383 88 637 (279, 988)** Wetland 9; 129 9; 124 403 36 1713 (988, 2433) 311 (100, 485)** Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 2 shows statistically significant decreases for this BMP category.

7169

2376

6100

1300

NA

NA

Pollutant Category Statistical Summary Report December 2014

In NA 4010 (411, 5600) 290 (52, 820) NA NA NA NA 2063 (1000, 3106) 1369 (694, 2336)

75th Percentile

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4.3 Fecal Coliform Figure 6. Box Plots of Influent/Effluent Fecal Coliform Concentrations

Table 6. Influent/Effluent Summary Statistics for Fecal Coliform (#/100 mL) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In NA

Out NA

In NA

Out NA

In NA

Out NA

In NA

Out NA

Biofilter - Grass Swale

11; 87

11; 82

1014

1045

4236 (1350, 5000)

4777 (2500, 6200)

20250

16750

NA 36690 11866 10333 NA 23000 22783

NA 20570 7104 5573 NA 6110 7233

23448

6386

NA

NA

Bioretention NA NA NA NA NA NA Composite 4; 64 4; 56 5477 4075 14715 (9633, 19191) 12287 (6805, 17162) Detention Basin 15; 170 15; 194 400 60 1832 (1100, 2680) 727 (371, 1483)** Media Filter 15; 184 15; 169 120 33 996 (400, 1528) 420 (200, 800)** Porous Pavement NA NA NA NA NA NA Retention Pond 10; 121 10; 123 300 25 3677 (1470, 5000) 581 (92, 800)** Wetland Basin 5; 42 5; 39 2400 185 10956 (3200, 15177) 1031 (230, 1900)** Wetland 15; 163 15; 162 611 42 5017 (2500, 7700) 679 (208, 1125)** Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 2 shows statistically significant decreases for this BMP category.

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5 METALS 5.1 Arsenic Figure 7. Box Plots of Influent/Effluent Dissolved Arsenic Concentrations

Table 7. Influent/Effluent Summary Statistics for Dissolved Arsenic (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

In Out In Out In Out Biofilter - Grass Strip 11; 208 11; 148 0.16 0.24 0.55 (0.35, 0.68) 0.61 (0.50, 0.77)*** Biofilter - Grass Swale 8; 45 8; 37 0.50 0.50 0.60 (0.50, 0.70) 0.60 (0.50, 0.66) Bioretention NA NA NA NA NA NA Composite NA NA NA NA NA NA Detention Basin 5; 44 5; 42 0.60 0.63 1.05 (0.77, 1.20) 1.04 (0.80, 1.20) Media Filter 9; 104 9; 100 0.26 0.33 0.50 (0.48, 0.56) 0.58 (0.5, 0.66) Porous Pavement NA NA NA NA NA NA Retention Pond NA NA NA NA NA NA Wetland Basin NA NA NA NA NA NA Wetland NA NA NA NA NA NA Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). ***Hypothesis testing in Attachment 3 shows statistically significant increases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

75th Percentile In 1.00 1.70 NA NA 1.30 1.13 NA NA NA

Out 2.02 0.85 NA NA 1.30 1.00 NA NA NA

NA

NA

NA

NA

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Figure 8. Box Plots of Influent/Effluent Total Arsenic Concentrations

Table 8. Influent/Effluent Summary Statistics for Total Arsenic (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 11; 208

Out 11; 149

In 0.30

Out 0.35

In 0.96 (0.73, 1.1)

Out 0.88 (0.53, 1.10)

In 1.73

Out 2.50

Biofilter - Grass Swale

8; 44

8; 37

1.07

0.60

1.69 (1.3, 1.81)

1.18 (0.95, 1.30)**

2.65

2.10

Bioretention NA NA NA NA NA NA Composite NA NA NA NA NA NA Detention Basin 6; 78 6; 72 1.43 1.20 1.99 (1.74, 2.36) 1.71 (1.49, 1.82) Media Filter 9; 104 9; 100 0.50 0.48 0.95 (0.69, 1.20) 0.77 (0.57, 0.98) Porous Pavement 4; 240 4; 118 2.50 2.50 2.50 (2.50, 2.50) 2.50 (2.50, 2.50) Retention Pond 4; 25 4; 23 1.00 0.52 1.29 (1.00, 1.80) 0.89 (0.50, 1.00)** Wetland Basin NA NA NA NA NA NA Wetland 4; 25 4; 23 1.00 0.52 1.29 (1.00, 1.80) 0.89 (0.50, 1.00)** Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category.

NA NA 2.70 1.85 2.50 2.00 NA

NA NA 2.23 1.30 2.50 1.41 NA

2.00

1.41

NA

NA

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5.2 Cadmium Figure 9. Box Plots of Influent/Effluent Dissolved Cadmium Concentrations

Table 9. Influent/Effluent Summary Statistics for Dissolved Cadmium (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 11; 207

Out 11; 148

In 0.05

Out 0.04

In 0.11 (0.09, 0.19)

Out 0.09 (0.07, 0.11)**

In 0.23

Out 0.20

Biofilter - Grass Swale

12; 83

12; 75

0.10

0.08

0.20 (0.15, 0.30)

0.12 (0.09, 0.15)**

0.40

0.20

Bioretention 4; 98 4; 85 0.02 0.03 0.03 (0.02, 0.03) 0.08 (0.04, 0.10)** Composite NA NA NA NA NA NA Detention Basin**** 8; 135 8; 141 0.07 0.05 0.12 (0.10, 0.14) 0.39 (0.20, 0.50)*** Media Filter 10; 117 10; 112 0.10 0.13 0.19 (0.12, 0.20) 0.16 (0.14, 0.19) Porous Pavement 4; 250 4; 123 0.03 0.02 0.06 (0.05, 0.07) 0.04 (0.02, 0.06)** Retention Pond**** 3; 54 3; 69 0.20 0.13 0.27 (0.21, 0.33) 0.13 (0.13, 0.13)** Wetland Basin 4; 36 4; 30 0.06 0.13 0.12 (0.07, 0.16) 0.28 (0.13, 0.30)** Wetland 7; 90 7; 99 0.12 0.13 0.20 (0.18, 0.23) 0.13 (0.13, 0.20)** Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 3 shows statistically significant increases for this BMP category. ****Conclusions are limited for this BMP category due to a large percentage of non-detects in the influent.

0.05 NA 0.22 0.20 0.10 0.48 0.21

0.20 NA 0.50 0.20 0.10 0.20 0.45

0.33

0.30

NA

NA

Pollutant Category Statistical Summary Report December 2014

Page 13

International Stormwater BMP Database

Figure 10. Box Plots of Influent/Effluent Total Cadmium Concentrations

Table 10. Influent/Effluent Summary Statistics for Total Cadmium (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 11; 208

Out 11; 149

In 0.20

Out 0.06

In 0.49 (0.40, 0.58)

Out 0.18 (0.09, 0.20)**

Biofilter - Grass Swale

14; 136

14; 124

0.35

0.19

0.44 (0.40, 0.47)

0.23 (0.22, 0.24)**

0.63

0.30

Bioretention**** 6; 127 6; 112 0.04 0.04 0.07 (0.05, 0.09) 0.07 (0.05, 0.08) Composite**** 5; 90 5; 87 0.12 0.25 0.26 (0.19, 0.34) 0.30 (0.25, 0.50)*** Detention Basin 12; 168 12; 173 0.14 0.13 0.30 (0.22, 0.38) 0.24 (0.20, 0.28)** Media Filter 16; 194 16; 194 0.10 0.03 0.29 (0.20, 0.36) 0.09 (0.07, 0.11)** Porous Pavement**** 4; 264 4; 130 0.13 0.25 0.24 (0.21, 0.28) 0.25 (0.25, 0.25) Retention Pond 24; 366 24; 404 0.17 0.09 0.39 (0.30, 0.42) 0.20 (0.15, 0.20)** Wetland Basin 7; 125 7; 136 0.10 0.10 0.26 (0.19, 0.30) 0.17 (0.11, 0.20)** Wetland 31; 491 31; 540 0.14 0.10 0.34 (0.29, 0.40) 0.19 (0.16, 0.20)** Basin/Retention Pond Wetland Channel 3; 69 3; 54 0.18 0.20 0.50 (0.27, 0.50) 0.47 (0.25, 0.50) NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 3 shows statistically significant increases for this BMP category. ****Conclusions are limited for this BMP category due to a large percentage of non-detects in the influent.

0.16 0.50 0.71 0.60 0.50 0.98 0.64

0.14 2.50 0.44 0.20 0.50 0.42 0.36

0.87

0.42

0.50

0.50

Pollutant Category Statistical Summary Report December 2014

In 0.80

Out 0.33

Page 14

International Stormwater BMP Database

5.3 Chromium Figure 11. Box Plots of Influent/Effluent Dissolved Chromium Concentrations

Table 11. Influent/Effluent Summary Statistics for Dissolved Chromium (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 11; 208

Out 11; 148

In 1.00

Out 1.00

In 1.98 (1.55, 2.20)

Out 1.62 (1.20, 1.80)

In 3.83

Out 3.60

Biofilter - Grass Swale

6; 37

6; 29

1.00

1.00

1.30 (1.00, 2.80)

1.37 (1.00, 2.70)

3.40

3.20

NA NA 2.30 1.00 0.50 2.00 NA

NA NA 1.60 1.00 3.80 1.00 NA

2.00

1.00

NA

NA

Bioretention NA NA NA NA NA NA Composite NA NA NA NA NA NA Detention Basin 4; 58 4; 52 0.43 0.41 0.95 (0.59, 1.35) 0.82 (0.52, 1.00) Media Filter 10; 114 10; 109 0.50 0.53 0.95 (0.62, 1.00) 1.00 (1.00, 1.00) Porous Pavement**** 4; 262 4; 129 0.50 1.70 0.50 (0.50, 0.50) 2.64 (2.29, 2.80)*** Retention Pond 4; 67 4; 81 1.00 0.87 1.23 (1.00, 1.48) 1.00 (1.00, 1.00)** Wetland Basin NA NA NA NA NA NA Wetland 4; 67 4; 81 1.00 0.87 1.23 (1, 1.48) 1.00 (1.00, 1.00)** Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 3 shows statistically significant increases for this BMP category. ****Conclusions are limited for this BMP category due to a large percentage of non-detects in the influent.

Pollutant Category Statistical Summary Report December 2014

Page 15

International Stormwater BMP Database

Figure 12. Box Plots of Influent/Effluent Total Chromium Concentrations

Table 12. Influent/Effluent Summary Statistics for Total Chromium (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 12; 211

Out 12; 152

In 2.90

Out 1.28

In 5.17 (4.20, 5.80)

Out 2.63 (2.05, 3.10)**

Biofilter - Grass Swale

6; 37

6; 29

1.80

1.50

4.53 (2.10, 6.30)

2.33 (1.50, 3.30)**

9.20

4.80

Bioretention 3; 72 3; 63 1.47 0.06 2.67 (2.04, 3.20) 0.35 (0.09, 0.49)** Composite NA NA NA NA NA NA Detention Basin 5; 68 5; 62 2.53 1.59 3.98 (3.10, 4.66) 2.55 (1.93, 3.15)** Media Filter 10; 115 10; 109 1.20 0.82 1.90 (1.50, 2.30) 1.00 (1.00, 1.10)** Porous Pavement 4; 264 4; 130 2.06 2.37 3.56 (3.31, 3.96) 3.89 (3.19, 4.57) Retention Pond 12; 153 12; 162 2.35 1.00 4.00 (3.70, 4.73) 1.37 (1, 1.85)** Wetland Basin NA NA NA NA NA NA Wetland 12; 153 12; 162 2.35 1.00 4.00 (3.70, 4.73) 1.37 (1.00, 1.85)** Basin/Retention Pond Wetland Channel 3; 70 3; 55 1.00 0.50 1.72 (1.20, 2.19) 1.40 (0.50, 1.93)** NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 3 shows statistically significant increases for this BMP category. ****Conclusions are limited for this BMP category due to a large percentage of non-detects in the influent.

4.59 NA 6.70 3.37 5.80 7.60 NA

1.96 NA 3.50 1.70 6.38 3.36 NA

7.60

3.36

3.23

4.00

Pollutant Category Statistical Summary Report December 2014

In 8.40

Out 6.20

Page 16

International Stormwater BMP Database

5.4 Copper Figure 13. Box Plots of Influent/Effluent Dissolved Copper Concentrations

Table 13. Influent/Effluent Summary Statistics for Dissolved Copper (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 11; 221

Out 11; 159

In 4.80

Out 2.80

In 10.94 (8.00, 12.00)

Out 5.28 (4.7, 6.00)**

In 19.00

Out 8.45

Biofilter - Grass Swale

16; 172

16; 139

3.30

3.49

6.58 (5.00, 7.86)

5.64 (4.61, 6.70)**

13.70

9.48

Bioretention 7; 125 7; 107 3.03 2.81 5.21 (4.10, 5.99) 5.79 (3.93, 7.54) Composite 2; 31 2; 27 9.24 5.90 18.34 (9.48, 30.0) 8.13 (6.09, 10.00)** Detention Basin 9; 186 9; 196 2.00 1.29 4.79 (3.65, 6.035) 2.86 (2.14, 3.45)** Media Filter 11; 189 11; 176 1.64 1.50 3.75 (2.65, 4.1) 3.24 (2.47, 3.80)** Porous Pavement 7; 351 7; 206 2.40 2.85 4.90 (4.00, 5.00) 5.05 (4.08, 5.10)** Retention Pond 16; 363 16; 364 3.09 2.30 4.90 (4.29, 5.40) 3.25 (3.00, 3.50)** Wetland Basin 6; 106 6; 100 2.69 1.18 3.97 (3.33, 4.38) 2.54 (1.69, 3.33)** Wetland 22; 469 22; 464 3.00 2.00 4.54 (4.16, 4.90) 3.18 (2.90, 3.33)** Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category.

9.70 30.00 10.25 7.60 7.70 7.33 5.75

13.45 10.00 8.36 6.90 7.00 4.89 4.27

7.00

4.82

NA

NA

Pollutant Category Statistical Summary Report December 2014

Page 17

International Stormwater BMP Database

Figure 14. Box Plots of Influent/Effluent Total Copper Concentrations

Table 14. Influent/Effluent Summary Statistics for Total Copper (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 12; 225

Out 12; 163

In 10.00

Out 4.70

In 23.21 (19.0, 26.0)

Out 7.19 (6.40, 7.90)**

Biofilter - Grass Swale

19; 320

19; 256

5.00

4.40

10.81 (8.95, 12.9)

9.28 (7.95, 10.5)**

24.2

15.3

Bioretention 13; 294 13; 259 4.80 3.50 8.75 (7.80, 9.75) 5.33 (4.58, 5.70)** Composite 6; 108 6; 98 6.82 4.01 11.79 (10.0, 15.2) 6.86 (5.45, 8.03)** Detention Basin 15; 249 15; 250 4.13 1.85 8.88 (7.34, 10.6) 4.99 (4.00, 5.96)** Media Filter 20; 345 20; 330 4.97 2.46 9.74 (8.5, 10.0) 5.52 (4.58, 6.29)** Porous Pavement 11; 397 11; 246 7.50 4.00 11.54 (10.4, 12.1) 7.52 (6.80, 8.00)** Retention Pond 40; 715 40; 717 4.43 2.70 8.95 (7.71, 9.38) 4.39 (4.00, 4.77)** Wetland Basin 10; 243 10; 238 4.18 2.00 7.23 (6.33, 8.00) 3.38 (3.00, 3.99)** Wetland 50; 958 50; 955 4.26 2.40 8.35 (7.68, 9.00) 4.07 (4.00, 4.32)** Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category.

16.7 30.0 23.3 16.9 19.9 16.1 11.7

10.0 10.0 12.0 10.0 11.0 6.8 6.0

14.4

6.6

NA

NA

Pollutant Category Statistical Summary Report December 2014

In 47.0

Out 11.5

Page 18

International Stormwater BMP Database

5.5 Iron Figure 15. Box Plots of Influent/Effluent Dissolved Iron Concentrations

Table 15. Influent/Effluent Summary Statistics for Dissolved Iron (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 4; 67

Out 4; 53

In 23.2

Out 46.0

In 47.8 (30.0, 73.0)

Out 157 (52.0, 199)***

In 149

Out 510

Biofilter - Grass Swale

NA

NA

NA

NA

NA

NA

NA

NA

NA NA NA NA 120 120 NA

NA NA NA NA 190 120 NA

120

120

NA

NA

Bioretention NA NA NA NA NA NA Composite NA NA NA NA NA NA Detention Basin NA NA NA NA NA NA Media Filter NA NA NA NA NA NA Porous Pavement 4; 260 4; 129 35.8 70.0 70.6 (60.0, 80.0) 100 (90, 120)*** Retention Pond 5; 115 5; 125 19.6 27.2 53.2 (31.0, 60.0) 62.1 (46.0, 71.5) Wetland Basin NA NA NA NA NA NA Wetland 5; 115 5; 125 19.6 27.2 53.3 (31.0, 60.0) 62.1 (46.0, 72.2) Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). ***Hypothesis testing in Attachment 3 shows statistically significant increases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

Page 19

International Stormwater BMP Database

Figure 16. Box Plots of Influent/Effluent Total Iron Concentrations

Table 16. Influent/Effluent Summary Statistics for Total Iron (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 4; 67

Out 4; 53

In 291

Out 135

In 789 (490, 1000)

Out 616 (190, 897)

In 1800

Out 1330

Biofilter - Grass Swale

3; 55

3; 49

39.0

40.0

152 (40, 180)

142 (44, 220)

514

350

805 5095 NA 1435 NA 3160 NA

1845 454 NA 421 NA 485 NA

2090

480

NA

NA

Bioretention 3; 44 3; 42 253 478 515 (280, 615) 1027 (510, 1380)*** Composite 3; 67 3; 56 477 157 1593 (820, 2170) 264 (166, 330)** Detention Basin NA NA NA NA NA NA Media Filter 7; 144 7; 132 257 113 608 (437, 754) 211 (163, 258)** Porous Pavement NA NA NA NA NA NA Retention Pond 16; 317 16; 312 393 153 1037 (820, 1200) 265 (224, 301)** Wetland Basin NA NA NA NA NA NA Wetland 18; 404 18; 399 269 165 686 (540, 825) 277 (240, 300)** Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 3 shows statistically significant increases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

Page 20

International Stormwater BMP Database

5.6 Lead Figure 17. Box Plots of Influent/Effluent Dissolved Lead Concentrations

Table 17. Influent/Effluent Summary Statistics for Dissolved Lead (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 11; 220

Out 11; 160

In 0.10

Out 0.09

In 0.49 (0.24, 0.90)

Out 0.24 (0.18, 0.32)**

In 2.60

Out 1.00

Biofilter - Grass Swale

14; 112

14; 95

0.60

0.49

1.35 (0.83, 1.52)

1.08 (0.76, 1.60)

6.25

3.21

0.13 32.4 1.70 1.50 0.50 4.00 1.29

0.10 3.20 1.36 1.00 0.50 3.50 1.45

3.20

3.17

NA

NA

Bioretention 5; 101 5; 88 0.04 0.02 0.07 (0.05, 0.08) 0.05 (0.03, 0.06)** Composite 3; 33 3; 28 0.24 0.08 2.56 (0.32, 10.2) 0.59 (0.07, 1.00)** Detention Basin 8; 164 8; 165 0.23 0.22 0.64 (0.44, 0.92) 0.55 (0.41, 0.70) Media Filter 10; 155 10; 150 0.32 0.42 1.00 (1.00, 1.00) 0.99 (0.51, 1.00) Porous Pavement**** 4; 292 4; 144 0.50 0.50 0.50 (0.50, 0.50) 0.50 (0.50, 0.50) Retention Pond 11; 163 11; 172 0.17 0.12 1.00 (0.66, 2.00) 0.81 (0.37, 1.00) Wetland Basin 4; 36 4; 30 0.38 0.35 0.67 (0.39, 0.84) 0.71 (0.37, 1.01) Wetland 15; 199 15; 202 0.19 0.15 0.90 (0.56, 1.06) 0.76 (0.43, 1.00) Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category. ****Conclusions are limited for this BMP category due to a large percentage of non-detects in the influent.

Pollutant Category Statistical Summary Report December 2014

Page 21

International Stormwater BMP Database

Figure 18. Box Plots of Influent/Effluent Total Lead Concentrations

Table 18. Influent/Effluent Summary Statistics for Total Lead (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 12; 225

Out 12; 163

In 3.10

Out 0.68

In 7.94 (6.00, 9.70)

Out 1.88 (1.30, 2.20)**

Biofilter - Grass Swale

18; 279

18; 230

1.32

1.26

3.91 (2.40, 4.10)

3.19 (2.19, 3.95)**

18.2

9.90

Bioretention 7; 138 7; 121 0.86 0.09 2.15 (1.56, 2.93) 0.19 (0.13, 0.25)** Composite 8; 140 8; 135 8.33 2.00 21.8 (18.5, 25.9) 5.29 (3.00, 6.00)** Detention Basin 13; 223 13; 214 2.19 1.32 7.37 (5.20, 9.53) 3.86 (2.86, 5.14)** Media Filter 19; 297 19; 289 2.69 0.71 10.2 (7.82, 12.0) 1.66 (1.20, 2.00)** Porous Pavement 8; 338 8; 183 0.49 0.07 2.24 (1.47, 3.20) 0.40 (0.22, 0.57)** Retention Pond 39; 618 39; 639 3.00 1.00 9.05 (6.70, 9.71) 2.87 (2.00, 3.00)** Wetland Basin 8; 145 8; 141 1.14 0.70 2.38 (1.88, 3.00) 1.32 (1.00, 1.78)** Wetland 47; 763 47; 780 2.00 1.00 7.11 (6.00, 8.00) 2.32 (2, 2.86)** Basin/Retention Pond Wetland Channel 5; 91 5; 78 1.05 1.00 3.47 (1.80, 6.30) 2.40 (1.06, 3.41) *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category.

6.13 56.3 35.0 22.0 9.55 26.0 7.72

0.56 11.6 11.2 3.78 1.64 8.6 3.60

20.80

7.00

21.4

6.60

Pollutant Category Statistical Summary Report December 2014

In 24.0

Out 4.50

Page 22

International Stormwater BMP Database

5.7 Nickel Figure 19. Box Plots of Influent/Effluent Dissolved Nickel Concentrations

Table 19. Influent/Effluent Summary Statistics for Dissolved Nickel (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 11; 208

Out 11; 148

In 1.19

Out 1.52

In 2.56 (2.06, 2.80)

Out 2.09 (2.00, 2.10)

In 3.80

Out 3.00

Biofilter - Grass Swale

5; 31

5; 23

2.80

2.00

4.92 (2.90, 5.90)

2.00 (2.00, 2.40)**

8.35

2.50

Bioretention NA NA NA NA NA NA Composite NA NA NA NA NA NA Detention Basin 5; 68 5; 62 1.32 1.31 2.33 (2.00, 2.75) 2.10 (1.60, 2.45) Media Filter 10; 114 10; 109 0.82 0.74 1.74 (1.00, 2.00) 1.41 (0.98, 2.00) Porous Pavement 4; 262 4; 129 0.63 0.24 1.10 (0.96, 1.30) 0.44 (0.35, 0.52)** Retention Pond 4; 43 4; 42 1.05 1.23 1.81 (1.30, 2.00) 2.33 (1.54, 3.01) Wetland Basin NA NA NA NA NA NA Wetland 4; 43 4; 42 1.05 1.23 1.81 (1.30, 2.00) 2.33 (1.54, 3.01) Basin/Retention Pond Wetland Channel NA NA NA NA NA NA NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category.

NA NA 3.85 2.10 1.80 2.85 NA

NA NA 3.18 2.00 0.82 4.30 NA

2.85

4.30

NA

NA

Pollutant Category Statistical Summary Report December 2014

Page 23

International Stormwater BMP Database

Figure 20. Box Plots of Influent/Effluent Total Nickel Concentrations

Table 20. Influent/Effluent Summary Statistics for Total Nickel (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 11; 208

Out 11; 149

In 3.20

Out 2.10

In 5.08 (4.40, 5.75)

Out 2.95 (2.40, 3.00)**

Biofilter - Grass Swale

5; 31

5; 23

5.15

2.35

9.25 (5.10, 12.0)

3.16 (2.30, 4.20)**

14.5

4.65

Bioretention 3; 65 3; 56 2.10 3.23 3.33 (2.39, 3.80) 4.53 (3.65, 5.20)*** Composite NA NA NA NA NA NA Detention Basin 6; 76 6; 70 3.10 2.00 5.04 (4.30, 5.50) 2.73 (2.18, 3.30)** Media Filter 10; 115 10; 109 2.00 1.12 3.22 (2.43, 3.6) 2.00 (2.00, 2.37)** Porous Pavement 4; 264 4; 130 2.40 1.20 3.51 (3.15, 3.75) 1.71 (1.40, 1.80)** Retention Pond 10; 113 10; 109 2.50 2.00 4.56 (3.50, 5.63) 2.23 (2.00, 2.70)** Wetland Basin NA NA NA NA NA NA Wetland 10; 113 10; 109 2.50 2.00 4.56 (3.50, 6.00) 2.23 (2.00, 2.70)** Basin/Retention Pond Wetland Channel 3; 68 3; 53 2.00 2.00 2.81 (2.13, 3.00) 2.20 (2.00, 2.45)** NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 3 shows statistically significant increases for this BMP category.

5.90 NA 9.03 5.10 5.82 9.38 NA

8.20 NA 4.20 3.40 2.60 5.92 NA

9.38

5.92

3.73

3.00

Pollutant Category Statistical Summary Report December 2014

In 8.50

Out 4.30

Page 24

International Stormwater BMP Database

5.8 Zinc Figure 21. Box Plots of Influent/Effluent Dissolved Zinc Concentrations

Table 21. Influent/Effluent Summary Statistics for Dissolved Zinc (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 11; 221

Out 11; 159

In 14.0

Out 6.00

In 33.7 (27.0, 38.0)

Out 13.7 (8.73, 15.0)**

In 68.0

Out 28.5

Biofilter - Grass Swale

16; 172

16; 139

17.1

13.5

33.2 (27.3, 35.8)

19.8 (16.7, 22.0)**

70.1

32.3

Bioretention 6; 126 6; 112 10.7 2.72 19.7 (15.0, 24.0) 12.2 (5.20, 15.3)** Composite 3; 67 3; 56 10.0 3.04 30.0 (20.0, 40.0) 9.53 (3.35, 10.0)** Detention Basin 9; 186 9; 197 5.44 3.00 13.1 (9.20, 15.5) 7.83 (5.4, 10.0)** Media Filter 11; 189 11; 175 11.2 1.82 29.2 (21.0, 36.0) 5.78 (3.37, 8.10)** Porous Pavement 7; 351 7; 206 6.40 0.38 13.4 (11.1, 15.1) 1.52 (1.00, 2.12)** Retention Pond 18; 360 18; 346 10.0 5.60 23.0 (19.0, 25.0) 14.9 (11.9, 16.4)** Wetland Basin 6; 106 6; 100 13.3 4.07 21.8 (18.8, 24.3) 7.64 (5.97, 8.71)** Wetland 24; 466 24; 446 11.0 5.2 22.6 (19.5, 23.95) 12.1 (10.0, 14.0)** Basin/Retention Pond Wetland Channel 3; 64 3; 56 4.61 3.04 11.7 (6.32, 16.9) 9.56 (3.05, 10.0) *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for analyzed BMPs for total zinc.

53.5 50.0 36.6 84.0 24.1 40.0 31.8

23.0 20.0 25.0 21.0 10.2 29.8 14.0

37.0

24.5

20.0

20.0

Pollutant Category Statistical Summary Report December 2014

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International Stormwater BMP Database

Figure 22. Box Plots of Influent/Effluent Total Zinc Concentrations

Table 22. Influent/Effluent Summary Statistics for Total Zinc (µg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 12; 225

Out 12; 163

In 48.0

Out 11.0

In 97.3 (80.0, 110)

Out 24.3 (13.6, 26.0)**

Biofilter - Grass Swale

21; 354

21; 286

20.0

17.8

40.0 (34.2, 50.0)

29.8 (23.0, 30.8)**

110

55.0

Bioretention 14; 329 14; 293 24.0 5.00 48.1 (39.0, 54.0) 12.0 (9.0, 13.0)** Composite 8; 148 8; 131 52.8 20.0 97.5 (80.0, 117) 35.5 (29.8, 40.0)** Detention Basin 15; 249 15; 251 21.5 6.00 49.8 (37.0, 61.8) 21.3 (14.6, 26.7)** Media Filter 23; 387 23; 358 23.3 4.19 62.8 (52.4, 70.0) 14.2 (11.4, 16.0)** Porous Pavement 12; 409 12; 256 20.5 1.73 49.3 (40.0, 50.8) 10.5 (7.56, 13.3)** Retention Pond 47; 787 47; 760 29.0 11.0 49.1 (42.4, 50.0) 21.67 (20.0, 23.2)** Wetland Basin 13; 271 13; 266 33.4 11.4 48.5 (43.2, 54.0) 20.0 (15.8, 21.7)** Wetland 60; 1058 60; 1026 30.0 11.0 48.9 (44, 50) 21.2 (20.0, 22.7)** Basin/Retention Pond Wetland Channel 4; 107 4; 86 13.5 10.0 23.0 (16.0, 30.0) 15.6 (11.0, 20.0)** *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 3 shows statistically significant decreases for analyzed BMPs for total zinc.

94.2 160 151 141 92.4 86.0 85.5

29.0 60.3 57.7 30.0 29.2 38.9 33.1

85.9

37.0

42.0

30.0

Pollutant Category Statistical Summary Report December 2014

In 180

Out 53.0

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International Stormwater BMP Database

6 NUTRIENTS 6.1 Phosphorus Figure 23. Box Plots of Influent/Effluent Total Phosphorus Concentrations

Table 23. Influent/Effluent Summary Statistics for Total Phosphorus (mg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 19; 360

Out 19; 276

In 0.075

Out 0.097

In 0.137 (0.120, 0.150)

Out 0.173 (0.150, 0.199)***

In 0.249

Out 0.339

Biofilter - Grass Swale

22; 393

22; 341

0.062

0.095

0.110 (0.100, 0.124)

0.171 (0.150, 0.190)***

0.240

0.280

Bioretention 27; 515 27; 435 0.062 0.080 0.120 (0.110, 0.140) 0.240 (0.183, 0.280)*** Composite 10; 184 10; 166 0.173 0.086 0.344 (0.276, 0.397) 0.132 (0.116, 0.144)** Detention Basin 21; 307 21; 322 0.169 0.114 0.253 (0.224, 0.27) 0.197 (0.178, 0.213)** Media Filter 22; 365 22; 349 0.070 0.040 0.150 (0.140, 0.170) 0.089 (0.075, 0.097)** Porous Pavement 7; 325 7; 192 0.119 0.071 0.176 (0.150, 0.178) 0.100 (0.093, 0.110)** Retention Pond 54; 874 54; 867 0.088 0.045 0.206 (0.184, 0.224) 0.091 (0.08, 0.099)** Wetland Basin 17; 376 17; 369 0.078 0.053 0.130 (0.115, 0.138) 0.093 (0.080, 0.100)** Wetland 71; 1250 71; 1236 0.082 0.047 0.168 (0.157, 0.18) 0.091 (0.082, 0.098)** Basin/Retention Pond Wetland Channel 8; 165 8; 146 0.090 0.093 0.156 (0.138, 0.170) 0.144 (0.122, 0.160) *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 4 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 4 shows statistically significant increases for this BMP category.

0.246 0.650 0.410 0.283 0.350 0.421 0.212

0.600 0.219 0.319 0.160 0.155 0.200 0.200

0.354

0.200

0.238

0.229

Pollutant Category Statistical Summary Report December 2014

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International Stormwater BMP Database

Figure 24. Box Plots of Influent/Effluent Orthophosphate Concentrations

Table 24. Influent/Effluent Summary Statistics for Orthophosphate (mg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 13; 276

Out 13; 219

In 0.010

Out 0.016

In 0.031 (0.021, 0.032)

Out 0.055 (0.039, 0.065)***

In 0.094

Out 0.145

Biofilter - Grass Swale

6; 175

6; 145

0.016

0.033

0.025 (0.022, 0.028)

0.077 (0.061, 0.094)***

0.040

0.129

Bioretention 18; 268 18; 239 0.007 0.043 0.020 (0.017, 0.032) 0.257 (0.162, 0.300)*** Composite 3; 51 3; 42 0.065 0.034 0.095 (0.070, 0.132) 0.075 (0.041, 0.102) Detention Basin NA NA NA NA NA NA Media Filter 7; 116 7; 115 0.020 0.015 0.037 (0.028, 0.05) 0.030 (0.022, 0.040) Porous Pavement 5; 142 5; 87 0.030 0.042 0.049 (0.044, 0.056) 0.072 (0.059, 0.079)*** Retention Pond 33; 527 33; 508 0.020 0.006 0.064 (0.054, 0.070) 0.021 (0.016, 0.026)** Wetland Basin 9; 259 9; 250 0.019 0.011 0.036 (0.030, 0.039) 0.032 (0.021, 0.041) Wetland 42; 786 42; 758 0.020 0.008 0.052 (0.046, 0.057) 0.024 (0.019, 0.028)** Basin/Retention Pond Wetland Channel 3; 84 3; 63 0.010 0.038 0.030 (0.016, 0.038) 0.058 (0.040, 0.064)*** NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 4 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 4 shows statistically significant increases for this BMP category.

0.090 0.192 NA 0.090 0.080 0.150 0.071

0.485 0.145 NA 0.070 0.104 0.060 0.100

0.130

0.070

0.060

0.082

Pollutant Category Statistical Summary Report December 2014

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International Stormwater BMP Database

Figure 25. Box Plots of Influent/Effluent Dissolved Phosphorus Concentrations

Table 25. Influent/Effluent Summary Statistics for Dissolved Phosphorus (mg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 3; 21

Out 3; 17

In 0.060

Out 0.180

In 0.076 (0.030, 0.080)

Out 0.253 (0.160, 0.260)***

In 0.140

Out 0.380

Biofilter - Grass Swale

6; 65

6; 53

0.030

0.045

0.056 (0.038, 0.070)

0.069 (0.047, 0.082)***

0.096

0.250

Bioretention NA NA NA NA NA NA Composite 8; 167 8; 153 0.073 0.042 0.140 (0.111, 0.170) 0.077 (0.060, 0.087)** Detention Basin 10; 137 10; 137 0.050 0.030 0.083 (0.069, 0.090) 0.081 (0.054, 0.096) Media Filter 10; 111 10; 100 0.013 0.016 0.047 (0.030, 0.060) 0.044 (0.030, 0.060) Porous Pavement 4; 214 4; 110 0.030 0.040 0.047 (0.040, 0.050) 0.050 (0.048, 0.060)*** Retention Pond 18; 373 18; 360 0.070 0.030 0.132 (0.111, 0.147) 0.069 (0.060, 0.075)** Wetland Basin 5; 115 5; 115 0.044 0.023 0.081 (0.059, 0.092) 0.047 (0.035, 0.060)** Wetland 23; 488 23; 475 0.060 0.030 0.114 (0.102, 0.126) 0.064 (0.057, 0.07)** Basin/Retention Pond Wetland Channel 5; 92 5; 89 0.048 0.060 0.079 (0.067, 0.096) 0.089 (0.070, 0.100) NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 4 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 4 shows statistically significant increases for this BMP category.

NA 0.224 0.159 0.097 0.080 0.212 0.127

NA 0.129 0.140 0.097 0.080 0.140 0.125

0.200

0.140

0.150

0.140

Pollutant Category Statistical Summary Report December 2014

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International Stormwater BMP Database

6.2 Nitrogen Figure 26. Box Plots of Influent/Effluent Total Nitrogen Concentrations

Table 26. Influent/Effluent Summary Statistics for Total Nitrogen (mg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 8; 138

Out 8; 122

In 0.81

Out 0.80

In 1.34 (1.06, 1.51)

Out 1.13 (1.00, 1.23)**

In 2.05

Out 1.55

Biofilter - Grass Swale

8; 241

8; 207

0.44

0.55

0.77 (0.65, 0.90)

0.87 (0.76, 1.02)

1.50

1.60

1.87 3.49 1.93 2.11 NA 2.64 1.87

1.61 1.80 2.94 1.72 NA 1.70 1.62

2.37

1.68

2.08

1.80

Bioretention 13; 245 13; 194 0.75 0.59 1.16 (1.01, 1.28) 0.92 (0.79, 1.02)** Composite 7; 138 7; 127 1.18 1.04 1.93 (1.70, 2.21) 1.37 (1.22, 1.45)** Detention Basin 5; 90 5; 89 0.87 0.85 1.32 (1.05, 1.52) 1.60 (1.10, 2.12) Media Filter 9; 154 9; 151 0.79 0.73 1.23 (1.03, 1.36) 1.04 (0.90, 1.16) Porous Pavement NA NA NA NA NA NA Retention Pond 26; 397 26; 425 1.01 0.81 1.63 (1.45, 1.78) 1.20 (1.10, 1.25)** Wetland Basin 7; 232 7; 235 0.80 0.87 1.13 (1.03, 1.23) 1.19 (1.04, 1.21) Wetland 33; 629 33; 660 0.92 0.84 1.43 (1.36, 1.50) 1.20 (1.12, 1.24)** Basin/Retention Pond Wetland Channel 5; 81 5; 78 1.21 0.93 1.57 (1.32, 1.72) 1.21 (1.01, 1.42)** NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 4 shows statistically significant decreases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

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International Stormwater BMP Database

Figure 27. Box Plots of Influent/Effluent Total Kjeldahl Nitrogen Concentrations

Table 27. Influent/Effluent Summary Statistics for Total Kjeldahl Nitrogen (mg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

Biofilter - Grass Strip

In 18; 352

Out 18; 268

In 0.75

Out 0.75

In 1.20 (1.12, 1.40)

Out 1.10 (0.97, 1.11)

Biofilter - Grass Swale

18; 314

18; 265

0.33

0.41

0.70 (0.55, 0.83)

0.76 (0.67, 0.85)

Bioretention 21; 410 21; 346 0.60 0.55 1.10 (0.86, 1.10) 1.34 (1.10, 1.40) Composite 7; 136 7; 127 0.80 0.54 1.57 (1.26, 1.80) 0.95 (0.81, 1.09)** Detention Basin 13; 205 13; 196 0.82 0.83 1.37 (1.10, 1.50) 1.49 (1.18, 1.63) Media Filter 20; 316 20; 312 0.56 0.29 0.96 (0.84, 1.08) 0.51 (0.43, 0.54)** Porous Pavement 6; 345 6; 196 1.40 0.70 2.17 (1.80, 2.30) 1.00 (0.95, 1.10)** Retention Pond 36; 498 36; 493 0.76 0.70 1.23 (1.10, 1.31) 1.01 (0.91, 1.03)** Wetland Basin 8; 96 8; 91 0.61 0.62 0.99 (0.84, 1.12) 0.82 (0.67, 0.90) Wetland 44; 594 44; 584 0.73 0.67 1.16 (1.06, 1.25) 0.97 (0.92, 1.03)** Basin/Retention Pond Wetland Channel 6; 120 6; 110 0.94 0.85 1.44 (1.30, 1.60) 1.25 (1.10, 1.35)** *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 4 shows statistically significant decreases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

75th Percentile In 1.93

Out 1.65

1.38

1.23

2.10 2.71 2.60 1.80 3.10 2.00 1.33

2.47 1.39 2.50 1.00 1.50 1.50 1.24

1.90

1.45

2.00

1.60

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International Stormwater BMP Database

Figure 28. Box Plots of Influent/Effluent NO3 as Nitrogen Concentrations

Table 28. Influent/Effluent Summary Statistics for NO3 as Nitrogen (mg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

75th Percentile

Biofilter - Grass Strip

In 12; 228

Out 12; 167

In 0.290

Out 0.180

In 0.60 (0.48, 0.68)

Out 0.44 (0.33, 0.51)**

In 1.10

Out 0.96

Biofilter - Grass Swale

11; 95

11; 77

0.230

0.260

0.49 (0.34, 0.60)

0.45 (0.30, 0.52)

0.86

0.77

0.45 0.77 1.20 0.59 NA 0.83 0.67

0.50 0.43 1.00 0.94 NA 0.50 0.16

0.81

0.50

0.31

0.30

Bioretention 3; 32 3; 27 0.168 0.195 0.31 (0.18, 0.40) 0.39 (0.20, 0.48) Composite 3; 54 3; 55 0.213 0.150 0.49 (0.37, 0.65) 0.28 (0.18, 0.33)** Detention Basin 6; 82 6; 75 0.392 0.360 0.76 (0.52, 0.88) 0.65 (0.47, 0.73) Media Filter 12; 178 12; 174 0.200 0.300 0.32 (0.27, 0.35) 0.56 (0.46, 0.63)*** Porous Pavement NA NA NA NA NA NA Retention Pond 15; 251 15; 247 0.250 0.120 0.49 (0.40, 0.54) 0.26 (0.19, 0.28)** Wetland Basin 5; 48 5; 38 0.127 0.032 0.29 (0.15, 0.42) 0.08 (0.05, 0.12)** Wetland 20; 299 20; 285 0.22 0.10 0.47 (0.367, 0.48) 0.22 (0.19, 0.26)** Basin/Retention Pond Wetland Channel 4; 82 4; 70 0.120 0.100 0.20 (0.16, 0.24) 0.17 (0.10, 0.20) NA – not available or less than 3 studies for BMP/constituent. *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 4 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 4 shows statistically significant increases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

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International Stormwater BMP Database

Figure 29. Box Plots of Influent/Effluent NO2 + NO3 as Nitrogen Concentrations

Table 29. Influent/Effluent Summary Statistics for NO2 + NO3 as Nitrogen (mg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

Biofilter - Grass Strip

In 7; 132

Out 7; 116

In 0.12

Out 0.10

In 0.25 (0.17, 0.29)

Out 0.19 (0.17, 0.22)**

Biofilter - Grass Swale

10; 267

10; 233

0.10

0.11

0.25 (0.2, 0.29)

0.22 (0.20, 0.24)

Bioretention 22; 435 22; 364 0.20 0.15 0.35 (0.31, 0.37) 0.37 (0.31, 0.43) Composite 7; 112 7; 99 0.36 0.34 0.59 (0.47, 0.72) 0.53 (0.45, 0.66) Detention Basin 9; 154 9; 154 0.21 0.06 0.44 (0.33, 0.53) 0.27 (0.14, 0.33)** Media Filter 9; 162 9; 154 0.24 0.38 0.36 (0.31, 0.40) 0.57 (0.48, 0.68)*** Porous Pavement 7; 358 7; 209 0.34 0.84 0.60 (0.53, 0.64) 1.35 (1.22, 1.51)*** Retention Pond 30; 439 30; 451 0.16 0.02 0.39 (0.34, 0.43) 0.13 (0.10, 0.16)** Wetland Basin 8; 220 8; 226 0.09 0.02 0.25 (0.20, 0.30) 0.09 (0.05, 0.12)** Wetland 38; 659 38; 677 0.126 0.02 0.34 (0.31, 0.37) 0.11 (0.09, 0.13)** Basin/Retention Pond Wetland Channel 4; 65 4; 61 0.41 0.08 0.77 (0.52, 0.99) 0.33 (0.14, 0.77)** *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 4 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 4 shows statistically significant increases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

75th Percentile In 0.42

Out 0.30

0.50

0.46

0.54 1.40 0.70 0.59 0.90 0.80 0.50

0.97 0.96 0.58 0.94 2.02 0.34 0.29

0.67

0.33

2.86

1.34

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International Stormwater BMP Database

Figure 30. Box Plots of Influent/Effluent NOx as Nitrogen Concentrations

Table 30. Influent/Effluent Summary Statistics for NOx as Nitrogen (mg/L) BMP Type

Count of Studies and EMCs

25th Percentile

Median (95% Conf. Interval)*

Biofilter - Grass Strip

In 19; 360

Out 19; 283

In 0.20

Out 0.14

In 0.41 (0.36, 0.46)

Out 0.28 (0.23, 0.32)**

Biofilter - Grass Swale

21; 478

21; 310

0.10

0.14

0.26 (0.23, 0.29)

0.27 (0.22, 0.30)

Bioretention 24; 468 24; 391 0.20 0.17 0.35 (0.31, 0.37) 0.38 (0.32, 0.42) Composite 10; 166 10; 154 0.33 0.27 0.56 (0.45, 0.65) 0.43 (0.36, 0.48)** Detention Basin 15; 236 15; 229 0.26 0.13 0.53 (0.43, 0.60) 0.38 (0.28, 0.45)** Media Filter 21; 340 21; 328 0.21 0.34 0.34 (0.30, 0.37) 0.57 (0.50, 0.63)*** Porous Pavement 7; 358 7; 209 0.34 0.84 0.60 (0.53, 0.64) 1.35 (1.22, 1.51)*** Retention Pond 45; 690 45; 698 0.19 0.05 0.43 (0.40, 0.47) 0.18 (0.15, 0.20)** Wetland Basin 13; 270 13; 266 0.09 0.02 0.26 (0.20, 0.29) 0.08 (0.05, 0.11)** Wetland 58; 960 58; 964 0.16 0.04 0.38 (0.34, 0.40) 0.15 (0.12, 0.16)** Basin/Retention Pond Wetland Channel 8; 147 8; 131 0.18 0.09 0.34 (0.27, 0.40) 0.19 (0.15, 0.22)** *Computed using the BCa bootstrap method described by Efron and Tibishirani (1993). **Hypothesis testing in Attachment 4 shows statistically significant decreases for this BMP category. ***Hypothesis testing in Attachment 4 shows statistically significant increases for this BMP category.

Pollutant Category Statistical Summary Report December 2014

75th Percentile In 0.87

Out 0.62

0.50

0.52

0.53 1.05 0.87 0.59 0.90 0.82 0.52

0.92 0.83 0.72 0.94 2.02 0.43 0.27

0.73

0.38

0.73

0.56

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International Stormwater BMP Database

7 REFERENCES Efron, B. and Tibishirani, R. (1993). An Introduction to the Bootstrap. Chapman & Hall, New York. Helsel, D.R. and Cohn, T.A. (1988). “Estimation of Descriptive Statistics for Multiply Censored Water Quality Data.” Wat. Res. Research, 24(12): 1997-2004. Helsel, D.R. and Hirsch, R.M. (1992). Statistical Methods in Water Resources. Studies in Enivironmental Science. Elsevier, N.Y. Geosyntec and Wright Water Engineers (2012). International Stormwater Best Management Practices (BMP) Database Addendum 1 to Volume Reduction Technical Summary (January 2011) Expanded Analysis of Volume Reduction in Bioretention BMPs. Prepared under Support from WERF, FHWA, EWRI/ASCE and EPA. Wright Water Engineers and Geosyntec and (2011). International Stormwater Best Management Practices (BMP) Database Technical Summary: Metals. Prepared under Support from WERF, FHWA, EWRI/ASCE and EPA. August.

8 ATTACHMENTS Attachment 1. Attachment 2. Attachment 3. Attachment 4.

Solids Statistical Summary Report Bacteria Statistical Summary Report Metals Statistical Summary Report Nutrients Statistical Summary Report

Pollutant Category Statistical Summary Report December 2014

Page 35