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Villanova University the Graduate School Department of Civil And Villanova University The Graduate School Department of Civil and Environmental Engineering The Implications of the First Flush Phenomenon on Infiltration BMP Design A Thesis in Civil Engineering by Tom Batroney Submitted in partial fulfillment of the requirements for the degree of Master of Science in Water Resources and Environmental Engineering May 2007 Acknowledgements Without the love and support of my father, Matthew, and my mother, Carol, this thesis would not have been possible. I truly feel blessed to have been raised by such caring individuals. They instilled virtues such as hard work, dedication, honesty, and faith which provided the cornerstones in which to achieve my goals and aspirations in life. I also hold Dr. Robert Traver in the same regard and see in him all the same characteristics as my parents. His drive to make the VUSP, its members, and everyone within the Villanova community (which includes me) the best they can be is truly amazing. Combine his hard work with his expertise in everything regarding stormwater and you have a perfect combination for success. Upon first meeting Dr. Traver when visiting potential graduate schools, I knew I wanted to come to Villanova University immediately because I thought so highly of him then. Upon leaving Villanova I hold him in even higher regard and I feel forever in debt for everything he provided me. Very special thanks also to Clay Emerson who provided so much help and insight into my questions and problems. I affectionately called him "the master" for a reason. It was amazing how quickly he could diagnose a situation and present a brilliantly simple solution. I would also like to thank Dr. Bridget Wadzuk, Bill Heasom, George Pappas, Nick Grosso, Mary Ellen Dukart, Hans Benford, Keisha Ricketts, David Salas, Krista Hankins, Matt Machusick, Matt Gore, Erika Tokarz, Megan Vanacore, Erin Burke, and Deniz Yurtserver for providing me support on both an academic and personal level. They will forever have my eternal friendship. 3 Abstract The stormwater runoff entering the Villanova University Stormwater Partnership (VUSP) Infiltration Trench was sampled incrementally during storm events between September 2006 and May 2007 in order to observe the change in pollutant concentration with respect to storm depth. The drainage area (20,400 ft2) consists of a 100 percent impervious parking deck used exclusively for Villanova University faculty and staff. The intention of this sampling methodology was to ascertain the existence of an initial high pollution concentration, otherwise known as the first flush phenomena. It was determined that total suspended solids, total dissolved solids, dissolved copper, and dissolved cadmium exhibited a first flush behavior which lasted until a rainfall depth of 1.0 inches was reached. The depth of 1.0 inches was further verified using Student's statistical T-test. Total phosphorus, total nitrogen, nitrite, nitrate, phosphate, and dissolved chromium did not exhibit a first flush. Using the observed data, a theoretical pollutant capture percent on the VUSP Infiltration Trench was determined. For all observed storm events since the trench's construction in July 2004, the theoretical pollutant capture on the pollutants ranged from 43% to 15%. Had the VUSP Infiltration Trench been constructed to the state recommended standard of 5:1 drainage area to footprint ratio, the theoretical pollutant capture percent would have ranged from 97% to 90%. The VUSP Infiltration Trench is intentionally undersized (158:1 drainage area to footprint ratio) in order to accelerate lifespan processes. 4 TABLE OF CONTENTS ACKNOWLEDGEMENTS..........................................................................................................................3 ABSTRACT ...................................................................................................................................................4 TABLE OF CONTENTS..............................................................................................................................5 TABLE OF FIGURES ..................................................................................................................................8 TABLE OF TABLES ..................................................................................................................................10 CHAPTER 1 - INTRODUCTION ................................................................................................................11 1.1 INTRODUCTION.........................................................................................................................11 1.2 FIRST FLUSH AT THE VUSP INFILTRATION TRENCH...................................................13 1.3 RESEARCH OBJECTIVES ........................................................................................................13 CHAPTER 2 - INFILTRATION TRENCH SITE DESCRIPTION.............................................................15 2.1 INTRODUCTION.........................................................................................................................15 2.2 SITE LOCATION.........................................................................................................................15 2.3 CONTRIBUTING DRAINAGE AREA ......................................................................................17 2.4 SURROUNDING SOIL AND SUBSURFACE CONDITIONS ................................................19 2.4 INFILTRATION TRENCH DESIGN.........................................................................................21 2.5 INFILTRATION TRENCH CONSTRUCTION .......................................................................23 2.5.1 INVESTIGATION OF PRE-CONSTRUCTION SITE PLANS ............................................................23 2.5.2 RETAINING WALL CONSTRUCTION ..........................................................................................24 2.5.3 TRENCH EXCAVATION PROCEDURES .......................................................................................25 2.5.4 INSTALLATION OF SAFETY OVERFLOW MECHANISMS............................................................27 CHAPTER 3 – LITERATURE REVIEW.....................................................................................................31 3.1 STORMWATER BEST MANAGEMENT PRACTICES IN THE URBAN SETTING ........31 3.1.1 INFILTRATION TRENCHES AS BEST MANAGEMENT PRACTICES .............................................32 3.2 SUSTAINABILITY OF INFILTRATION TRENCH BMPS ...................................................34 3.3 FIRST FLUSH PHENOMENON ................................................................................................36 3.3.1 EMPIRICAL BASED FIRST FLUSH THEORY ...............................................................................37 3.3.2 CONCENTRATION BASED FIRST FLUSH THEORY .....................................................................38 3.3.3 MASS BASED FIRST FLUSH THEORY.........................................................................................39 3.4 THE AMBIGUOUS FIRST FLUSH DEFINITION ..................................................................44 CHAPTER 4 – METHODS...........................................................................................................................48 4.1 INTRODUCTION.........................................................................................................................48 4.2 INFILTRATION TRENCH INSTRUMENTATION AND SETUP – QUANTITY ...............49 5 4.2.1 RAINFALL MONITORING ...........................................................................................................49 4.2.2 INFLOW MONITORING...............................................................................................................50 4.2.3 STORAGE DEPTH/VOLUME MONITORING ................................................................................52 4.2.4 OVERFLOW MONITORING.........................................................................................................53 4.2.5 DATA LOGGING AND RETRIEVAL .............................................................................................57 4.3 INFILTRATION TRENCH INSTRUMENTATION AND SETUP – QUALITY ..................66 4.3.1 INFLOW SAMPLING PROCEDURES AND INSTRUMENTATION....................................................66 4.3.2 OVERFLOW SAMPLING PROCEDURES AND INSTRUMENTATION..............................................71 4.4 INSTRUMENTATION CALIBRATION ...................................................................................75 4.4.1 RAIN GAGE ................................................................................................................................76 4.4.2 PS9800 PRESSURE TRANSDUCERS ............................................................................................76 4.4.3 SIGMA 900 AUTOMATED SAMPLERS.........................................................................................78 4.5 LABORATORY TESTING AND PROCEDURES ...................................................................78 4.5.1 LABORATORY METHODS - NUTRIENTS ....................................................................................79 4.5.2 LABORATORY METHODS – SOLIDS...........................................................................................80 4.5.3 LABORATORY METHODS – DISSOLVED METALS .....................................................................81 4.5.4 LABORATORY METHODS – LOW TRACE IONS .........................................................................81
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