,... ... Storm Water Master Plan .... September 1996 ... ..., Arlington County, Virginia Department of Public Works ... Public Works Planning Division ARLINGTON COUNTY, vm.GINIA Arlington County Board James B. Hunter, ill, Chair Ellen M. Bozman, Vice Chair Albert C. Eisenberg ... Paul Ferguson Christopher Zimmerman Arlington County Commissions Planning Commission, Elinor Schwartz, Chair ... Environment and Energy Conservation Commission, R.B. Neustadt, Chair Office of the County Manager Anton S. Gardner, County Manager ... William T. Donahue, Deputy County Manager Prepared By William H. Frost, P.E., Senior Planner Department of Public Works Public Works Planning Division Storm Water Master Plan Team .... Greg ZeIl, Department of Parks, Recreation, and Community Resources Rachael Slemons, (formerly with Department of Management and Finance) Bill Roberts, Department of Community Planning, Housing, and Development Carol McCoskrie, Office of the County Attorney Jeff Ham, Department of Environmental Services ... Mark Graham, (formerly with Department of Environmental Services) Other Assistance Many reviewers from the following departments, whose contributions are gratefully acknowledged. Department of Public Works Department of Parks, Recreation, and Community Resources Department of Community Planning, Housing, and Development Department of Environmental Services ... CONTENTS CHAPI'ER. ONE: INTRODUCTION . • o. .. 1 ORGANIZATION OF THIS MASTER PLAN . • . • . • • . .. 1 KEY CONCEPTS IN STORM WATER MANAGEMENT ......••...... 2 COMPREHENSIVE PLANNING CONTEXT ............•........• 3 mSTORY OF STORM WATER FACILITY PLANNING IN ARLINGTON. .. 4 CHAPTER TWO: POLICIES, PRINCIPLES, GOALS, AND OBJECTIVES •...... 6 SUMMARY OF EXISTING POUCIES ......0. .. 6 PROPOSED POUCIES • . • . • . .. 7 GOALS AND OBJECTIVES . • . • . .. 7 Reduce or control damages from flooding ...........•........ 7 Improve runoff quality •...••........•.....•... .. 8 Preserve and improve stream valleys ...............•....... 8 Preserve groundwater resources .......................... 9 PRINCIPLES .....•.................................... 9 Coordination principles . • . • . .. 9 Planning and design principles ........................... 10 Financing principles . • . • o. 10 Maintenance principles .. 11 CHAPI'ER. THREE: REGVLATORY REQUIREMENTS ........ .. 12 FEDERAL AND STATE LAWS AND REGULATIONS ............... 12 Federal Regulations and Programs . • . 12 State Laws and Regulations .......................•..... 12 ARL~GTONORDINANCES ................................ 13 SIGNIFICANT STATE AND FEDERAL REGULATIONS .............. 15 CHAPTER FOUR: WATERSHED EVALUATION ....................... 17 WATERSHED DELINEATION ............................... 17 CHANNEL CHARACTERISTICS ................•............ 17 WATERSHED CHARACTERISTICS ................••......... 20 l..a.nd Use. • . • • . • . • . • • • . • . • . 20 Imperviousness . 21 Forests .......................................... 24 Wetlands ........................................ 28 WATER QUALITY PROBLEMS . '. 28 o Background . · . 28 Arlington Stream Quality . 30 Chesapeake Bay Quality ............................... 32 FLOODING PROBLEMS .................................. 32 WATERSHED PRIORITY RANKINGS . 33 Classification . 33 Priorities for stream restoration . 35 Priorities for water quality improvements . • . 36 Priorities for flood damage reduction ....................... 36 \ \. ,.. CHAPTER FIVE: EXISTING AND PROPOSED PROGRAMS ............... 37 I NEW DEVELOPMENT AND REDEVELOPMENT . 38 CONSTR..UCTION . • . • • • . • • • • . • • . • • • 40 EXISTIN"G DEVELOPMENT' . • • • . • • • • . • . • • . 41 r-' POLLUTION PREVENTION - ILLICIT DISCHARGES AND SPILLS ...... 42 I POLLUTION PREVENTION - PUBLIC EDUCATION AND OUTREACH' ... 43 ROADS, HIGHWAYS, AND BRIDGES .....•................... 45 STREAMBANKS, WETLANDS, AND FLOODPLAINS ............... 45 MONITORIN"G . • . • . • . • . 46 CHAPTER SIX: CONCLUSIONS AND RECOMMENDATIONS . • • . 48 SYSTEM KNOWLEDGE . • . • • . 49 EXISTING DEVELOPMENT' ...•.................••......... 51 NEW DEVELOPMENT ..............•....••........•. ~ ... 51 BIBLIOGRAPHY ..................•......................... 52 Comprehensive Plan History . 52 Storm Sewer Plan History ..............•.•................. 52 r-' Policies, Principles, Goals, Objectives, Standards .................... 52 I Watershed Delineation . • . 54 ABBREVIATIONS ........................................... 56 APPENDIX A: FEDERAL AND STATE LAWS AND REGULATIONS ......... 58 r APPENDIX B: STORM DRAINAGE CAPITAL IMPROVEMENTS ............ 65 r ',... I ( rI ~ FIGURES Figure 1: Original and Remaining Streams ...••.•..................... 18 Figure 2: Watersheds in Arlington County and Vicinity .•.............•.... 19 Figure 3: Existing I.Jlnd Use. • . • . 22 Figure 4: Impervious Surface ........................•........... 25 Figure 5: Forest Cover ...........•.....•..........•...•....... 27 Figure .6: Potential Wetlands ..................................... 29 .~ TABLES Table 1: Comprehensive Plan Elements ..•...•..•.••.........•....... 3 Table 2: Proportion of Land Use in Each Watershed ...•.•................ 23 Table 3: Watershed Characteristics •..........•..................... 26 Table 4: Stonn Water Pollutants and Sources . •. 31 Table 5: Watershed Evaluation ............•...................... 34 ~ ! ,~ - ~ I PREFACE It has been fifty years since a comprehensive study of drainage needs has been made for Arlington County. In those five decades the technology and purpose of storm water management systems have changed substantially. Environmental regulations have added new constraints and opportunities. There is an increasing importance on designing storm drainage systems to improve runoff quality as well as control flooding. Emphasis on enhancing and restoring natural stream valleys has brought changes in the focus of storm drainage. Technology and design methods are changing rapidly, as assumptions about current engineering practices are challenged by new research. This Storm Water Master Plan has been driven by these changes. It is being written as a forum to discuss Arlington County's policies and goals for storm water management, and to reach a consensus among citizens and County agencies on programs and projects to correct runoff problems. The guiding philosophy behind the Storm Water Master Plan is that storm water management problems cannot be solved piecemeal, either site-by-site or agency-by-agency. Runoff does not respect jurisdiction boundaries or property lines, and analysis of problems must take a watershed approach. To develop technically sound projects that are supported by the community; a diverse group of specialists and interest groups are needed to contribute to planning and design. No Master Plan can guarantee a particular result. Circumstances and priorities change and the plan must be flexible enough to accommodate change. In the field of storm water management, changes have been rapid. New laws and regulations have revised many of the assumptions under which a plan would have been developed earlier. There is no reason to expect these changes to stop. An important purpose of this plan is to provide the policies and principles that can guide revisions to specific watershed projects as changes occur. The activities proposed as a result of this planning effort are somewhat unconventional. Instead of projects to be designed and built through the Capital Improvement Program (CIP), several programs are proposed to meet plan objectives. A series of proposed studies will guide project planning and may lead to future CIP projects. Steps required to develop CIP projects include (1) establishing priorities for programs and watershed studies (done as part of this Master Plan), (2) carrying out data collection and analysis with the programs discussed in Chapters 5 and 6 to identify deficiencies, (3) developing sources of funding and preliminary concepts for improvement projects, and (4) developing a detailed design. Projects requiring County capital funds are programmed in the six-year Capital Improvement Program (CIP). County Board reviews of the CIP and the annual budget are opportunities for public review of proposed storm water projects, priorities, and funding. Where new development changes runoff characteristics substantially, review of storm water management is part of the County staff review of development plans. In addition to these review opportunities, Arlington County is committed to a thorough and open public participation process in the consideration of any new County facilities. As circumstances change, the plan should represent the most current thinking of the County. Between comprehensive plan updates, amendments are appropriate. Should the goals and objectives change, should new regulations be adopted, should specific facility proposals need to be changed, then this plan should be amended. Proposed amendments should be considered by other County commissions as appropriate, and be subject to an open public participation process developed for the type of amendment. The Stonn Water Master Plan has been developed through a process of inter-agency and citizen participation. The Department of Public Works has had primary responsibility for its development, with input from a Storm Water Master Plan Project Team consisting of representatives from the following departments: Department of Environmental Services Department of Parks, Recreation, and Community Resources Department of Com~unity Planning, Housing, and Development