Examination of Thermal Impacts From Stormwater Best Management Practices Prepared by The University of New Hampshire Stormwater Center Prepared with Support from U.S. Envvironmental Protection Agency Region 1 TMDL Program January 2011 TABLE OF CONTENTS TABLE OF CONTENTS ...........................................................................................................................................II LIST OF FIGURES .................................................................................................................................................. IV LIST OF TABLES ...................................................................................................................................................... V LIST OF EQUATIONS .............................................................................................................................................. V ACKNOWLEDGEMENTS ..................................................................................................................................... VI TASK 1: MONITORING OF BMP SYSTEM PERFORMANCE .......................................................................... 7 EXECUTIVE SUMMARY ......................................................................................................................................... 7 INTRODUCTION ....................................................................................................................................................... 8 BACKGROUND .......................................................................................................................................................... 9 LITERATURE REVIEW ......................................................................................................................................... 10 STUDY DESIGN ....................................................................................................................................................... 10 SITE DESCRIPTION AND RUNOFF .................................................................................................................... 11 SYSTEM DESCRIPTIONS ...................................................................................................................................... 12 RETENTION POND .................................................................................................................................................... 12 DETENTION POND .................................................................................................................................................... 12 GRAVEL WETLAND ................................................................................................................................................. 13 BIORETENTION ........................................................................................................................................................ 13 VEGETATED SWALE ................................................................................................................................................. 13 HYDRODYNAMIC SEPARATORS ................................................................................................................................ 13 ADS INFILTRATION SYSTEM ................................................................................................................................... 14 STORMTECH ISOLATOR ROW ................................................................................................................................... 14 MATERIALS AND METHODS .............................................................................................................................. 14 SITE DATA COLLECTION .......................................................................................................................................... 14 DATA ANALYSIS ...................................................................................................................................................... 15 RESULTS AND DISCUSSION ................................................................................................................................ 16 ANNUAL QUARTILE ASSESSMENT ........................................................................................................................... 21 SEASONAL QUARTILE ASSESSMENT ........................................................................................................................ 22 TIME SERIES ANALYSIS ........................................................................................................................................... 25 ANNUAL CUMULATIVE DISTRIBUTION FUNCTIONS ................................................................................................. 25 SEASONAL CUMULATIVE DISTRIBUTIONS FUNCTIONS ............................................................................................ 29 FREQUENCY DISTRIBUTIONS ................................................................................................................................... 29 NATURAL STREAMS AND MIXING ............................................................................................................................ 34 SUMMARY ................................................................................................................................................................ 36 STORMWATER BMP EVENT MEAN TEMPERATURE ................................................................................................. 36 CONCLUSIONS AND RECOMMENDATIONS ................................................................................................... 37 CONCLUSIONS ......................................................................................................................................................... 37 FUTURE RESEARCH ................................................................................................................................................. 37 REFERENCES .......................................................................................................................................................... 47 TASK 2: OUTREACH AND EDUCATION ........................................................................................................... 49 WORKSHOP .............................................................................................................................................................. 49 WEB PAGE ............................................................................................................................................................... 50 ii APPENDIX A: STORM CHARACTERISTICS ................................................................................................... 51 APPENDIX B: STORM DISTRIBUTION STATISTICS .................................................................................... 57 APPENDIX C: MEAN JULY STATISTICS ......................................................................................................... 60 APPENDIX D: SYSTEM CDF STATISTICS ....................................................................................................... 78 APPENDIX E: SYSTEM TREATMENT STATISTICS .................................................................................... 121 APPENDIX F: CALCULATION OF AN EVENT MEAN TEMPERATURE ................................................. 146 iii LIST OF FIGURES Figure 1: Thermal Energy Balance ................................................................................................ 9 Figure 2: Distribution of Storm Characteristics for 120 Monitored Storms ................................ 18 Figure 3: Summer Storm Characteristic Correlations ................................................................. 19 Figure 4: Winter Storm Characteristic Correlations ................................................................... 20 Figure 5: Annual Quartile Distributions for Event Mean Temperatures ..................................... 21 Figure 6: Summer Quartile Distributions for Event Mean Temperatures3 ................................. 23 Figure 7: Winter Quartile Distributions of Event Mean Temperatures3 ..................................... 24 Figure 8: Annual Cumulative Distribution Function for Event Mean Temperatures .................. 27 Figure 9: Annual Cumulative Distribution Function for Event Mean Temperatures .................. 27 Figure 10: Annual Cumulative Distribution Function for Event Mean Temperatures ................ 28 Figure 11: Summer Cumulative Distribution Function for Event Mean Temperatures ............... 30 Figure 12: Summer Cumulative Distribution Function for Event Mean Temperatures ............... 30 Figure 13: Summer Cumulative Distribution Function for Event Mean Temperatures ............... 31 Figure 14: Winter Cumulative Distribution Function for Event Mean Temperatures ................. 32 Figure 15: Winter Cumulative Distribution Function for Event Mean Temperatures ................. 32 Figure 16: Winter Cumulative Distribution Function for Event Mean Temperatures ................. 33 Figure 17: Cumulative Distribution of Natural Streams .............................................................. 35 Figure 18: Cumulative Distribution of Natural Streams vs. Stormwater BMPs .......................... 35 Figure 19: Time Series of Event Mean Temperatures for a Gravel Wetland and Bioretention ... 38 Figure 20: Time Series