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Quantifying the Effects of Residential Infill Redevelopment on Urban Stormwater Quality

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Quantifying the Effects of Residential Infill Redevelopment on Urban Stormwater Quality QUANTIFYING THE EFFECTS OF RESIDENTIAL INFILL REDEVELOPMENT ON URBAN STORMWATER QUALITY by Kyle Gustafson Copyright by Kyle R. Gustafson 2019 All Rights Reserved A thesis submitted to the Faculty and the Board of Trustees of the Colorado School of Mines in partial fulfillment of the requirements for the degree of Master of Science (Hydrology). Golden, Colorado Date Signed: Kyle Gustafson Signed: Dr. John McCray Thesis Advisor Golden, Colorado Date Signed: Dr. Jonathan Sharp Professor and Department Head Dept. of Hydrologic Science and Engineering ii ABSTRACT The population of Denver, Colorado is expected to nearly double by 2050, raising concerns of local and regional decision makers regarding water supply and water quality. Urban redevelopment trends in the Denver metro area have been focusing on higher density development and infrastructure that support increased populations, typical of many cities undergoing similar changes. These redevelopment trends, referred to as infill redevelopment, typically include reducing the pervious lawn space and increasing impervious surface with building coverage. Urban redevelopment distinctly increases stormwater runoff quantity, but little work has been conducted on quantifying the effects on stormwater runoff quality. The focus of this project is to correlate water quality effects to urban redevelopment in order to aid data driven decision-making by local planners. In collaboration with the City of Denver, this study has been monitoring stormwater quality at three sites in a neighborhood of northwestern Denver that is undergoing rapid urban and commercial redevelopment. Each site is representative of a different stage of redevelopment, providing a redevelopment gradient. Stormwater sampling was conducted over 18 months: the first period started in May 2018 and continued through August 2019. A total of 15 wet-weather events were sampled and results indicate that phosphorous, total nitrogen, total dissolved solids, total recoverable copper and zinc concentrations are predominantly higher than previously reported values, which are currently used by local stormwater managers for water quality planning. While our goal to understand infill development impacts on water quality could not be realized, we did show that neighborhood scale sampling is likely to produce significantly different results than city-wide EMC averages. The City of Denver aims to use this locally collected data to inform new regulations associated with urban redevelopment, and potentially in the design of distributed green infrastructure or a regional stormwater treatment facility on City Parks and Recreation land near the study area. It is believed that locally focused stormwater monitoring can provide useful information for decision-making related to green infrastructure and water quality planning. iii TABLE OF CONTENTS ABSTRACT .................................................................................................................................................. iii LIST OF FIGURES ...................................................................................................................................... vi LIST OF TABLES ...................................................................................................................................... xiv CHAPTER 1: INTRODUCTION AND RESEARCH QUESTIONS ............................................................... 1 1.1 Project Background ............................................................................................................................ 1 1.2 Research Questions ........................................................................................................................... 3 1.3 Chapter Outline .................................................................................................................................. 3 CHAPTER 2: LITERATURE REVIEW ......................................................................................................... 4 2.1 Urban Runoff Sampling ...................................................................................................................... 4 2.2 Established Sampling Strategies ....................................................................................................... 5 2.3 Reported Trends in Stormwater Quality ............................................................................................. 7 2.4 Statistical Analysis and Applied Regression .................................................................................... 10 2.5 Infill Development and Effects on Water Quality .............................................................................. 11 2.6 Metals in Stormwater: sources, types, and forms ............................................................................ 13 2.7 Nutrients: Sources, Types, and Forms ............................................................................................. 15 CHAPTER 3: METHODS ........................................................................................................................... 18 3.1 GIS Delineation ................................................................................................................................ 18 3.2 Impervious Area Determination ........................................................................................................ 18 3.3 Zoning Distribution ........................................................................................................................... 18 3.4 Rainfall Estimation ........................................................................................................................... 19 3.5 Sampling Locations .......................................................................................................................... 19 3.6 Field Collection Procedures ............................................................................................................. 19 3.7 Lab Analysis Methods ...................................................................................................................... 21 3.8 Load Comparisons ........................................................................................................................... 22 3.9 CDPHE Water Quality Standards .................................................................................................... 23 3.10 Statistical Methods ......................................................................................................................... 24 3.10.1 Summary Statistics .................................................................................................................. 24 3.10.2 Anderson-Darling test for normality ......................................................................................... 25 3.10.3 Pearson Correlation ................................................................................................................. 25 3.10.4 Box-Cox Transformation .......................................................................................................... 26 3.10.5 One-Way Analysis of Variance (ANOVA) ................................................................................ 26 3.10.6 Analysis of Covariance (ANCOVA) ......................................................................................... 28 CHAPTER 4: RESULTS ............................................................................................................................ 30 4.1 GIS Analysis ..................................................................................................................................... 30 4.2 Dry Weather Urban Water Quality ................................................................................................... 33 4.3 Snowmelt Results ............................................................................................................................ 37 iv 4.4 Wet Weather Results ....................................................................................................................... 37 4.5 Loading Comparison Results ........................................................................................................... 45 4.6 Correlation Results ........................................................................................................................... 46 4.7 ANOVA and Comparison Results .................................................................................................... 47 4.7.1 Dry Weather Site Comparisons ................................................................................................. 47 4.7.2 Comparison between Sites ........................................................................................................ 48 4.7.3 Comparison with UDFCD Values .............................................................................................. 49 4.8 ANCOVA Results ............................................................................................................................. 50 CHAPTER 5: DISCUSSION ...................................................................................................................... 52 5.1 GIS Delineation and Land Use ......................................................................................................... 52 5.2 Dry Weather Water Quality .............................................................................................................
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