FARM CREEK AND MARUMSCO CREEK WATERSHED MANAGEMENT PLAN PREPARED FOR: PRINCE WILLIAM COUNTY DEPARTMENT OF PUBLIC WORKS PREPARED BY: ENVIRONMENTAL SERVICES DIVISION PARSONS BRINCKERHOFF WATERSHED MANAGEMENT BRANCH HERNDON, VIRGINIA 5 COUNTY COMPLEX COURT PRINCE WILLIAM, VIRGINIA DECEMBER 2009 Farm Creek and Marumsco Creek PB Watershed Management Plan December 2009 Table of Contents Executive Summary...............................................................................................................................1 CHAPTER 1: Introduction .....................................................................................................................4 1.1 Background..............................................................................................................................4 1.2 Purpose ...................................................................................................................................4 1.3 Report Organization .................................................................................................................5 CHAPTER 2: Watershed Characterization............................................................................................6 2.1 General Watershed Characteristics ..........................................................................................6 2.1.1 Location and Scale...............................................................................................................6 2.1.2 Geomorphology....................................................................................................................8 2.1.3 Watershed History and Development.................................................................................. 15 2.1.4 Existing and Long Range Land Uses.................................................................................. 16 2.1.5 Storm Drain Infrastructure and Stormwater Management.................................................... 25 2.2 Summary of Reference Data and Reports .............................................................................. 27 2.2.1 Prince William County Stream Protection Strategy.............................................................. 27 2.2.2 Marumsco Acres Lake Litter Study ..................................................................................... 28 2.2.3 303(d) Listings and Total Maximum Daily Loads (TMDLs) .................................................. 28 CHAPTER 3: Watershed Assessment................................................................................................. 30 3.1 Introduction ............................................................................................................................ 30 3.2 Existing Flood Studies............................................................................................................ 30 3.3 Stream Corridor Assessments................................................................................................ 35 3.3.1 Assessment Protocol.......................................................................................................... 35 3.3.2 General Findings................................................................................................................ 36 3.4 Stormwater Management Facilities......................................................................................... 59 CHAPTER 4: Watershed Action Plan.................................................................................................. 61 4.1 Initial Watershed Management Strategies............................................................................... 61 4.2 Recommendations ................................................................................................................. 62 4.2.1 Stream Corridor Improvement ............................................................................................ 62 4.2.2 Flood Mitigation.................................................................................................................. 64 4.2.3 BMP Retrofits & Maintenance............................................................................................. 65 4.2.4 Geologic Water Quality Impacts ......................................................................................... 67 4.2.5 Coastal Zone Improvement ................................................................................................ 68 4.2.6 Maintenance and Outreach Programs ................................................................................ 71 4.2.7 Upland Considerations ....................................................................................................... 71 CHAPTER 5: References..................................................................................................................... 73 Appendix A: Project Concept Plans: Stream Corridor Improvements Appendix B: Inspection Reports: Stormwater Management Facilities Appendix C: Project Concept Plans: Coastal Zone Improvements Appendix D: FEMA Flood Insurance Rate Maps (FIRMETTE’s) i Farm Creek and Marumsco Creek PB Watershed Management Plan December 2009 List of Figures Figure 2-1: Marumsco Creek and Farm Creek Subwatersheds ................................................................7 Figure 2-2: Geology within the Marumsco Creek and Farm Creek Watersheds ...................................... 11 Figure 2-3: Soil Types within the Marumsco Creek and Farm Creek Watersheds ................................... 14 Figure 3-1: Very Severe to Moderately Severe Rated Outfall Locations with Restoration Potential ......... 39 Figure 3-2: Erosion Site Locations ......................................................................................................... 42 Figure 3-3: Impacted Buffer Site Locations............................................................................................. 45 Figure 3-4: Utility Impact Site Locations ................................................................................................. 48 Figure 3-5: Trash and Debris Site Locations .......................................................................................... 51 Figure 3-6: Stream Crossing Site Locations ........................................................................................... 53 Figure 3-7: Channel Modification Site Locations..................................................................................... 56 Figure 3-8: SWM Facility Survey Locations............................................................................................ 60 List of Tables Table 2-1: Subwatershed Acreages .........................................................................................................6 Table 2-2: Summary of Primary Soil Types in Marumsco Creek and Farm Creek Watersheds................ 12 Table 2-3: Long Range Land Uses in Marumsco Creek and Farm Creek Watersheds............................ 25 Table 2-4: Stormwater Management Facilities........................................................................................ 26 Table 3-1: Number of Impact Assessment Sites..................................................................................... 36 Table 3-2: Observed Water Quality Impact Lengths ............................................................................... 36 Table 3-3: Outfall Severity Ratings......................................................................................................... 38 Table 3-4: Erosion Severity Ratings....................................................................................................... 41 Table 3-5: Impacted Buffer Severity Ratings .......................................................................................... 44 Table 3-6: Utility Crossing Severity Ratings............................................................................................ 47 Table 3-7: Trash and Debris Severity Ratings ........................................................................................ 50 Table 3-8: Stream Crossing Severity Ratings......................................................................................... 52 Table 3-9: Stream Crossing Severity Ratings......................................................................................... 54 Table 3-10: Coastal Zone Severity Ratings ............................................................................................ 58 Table 4-1: Stream Corridor Improvement Projects – Cost Estimates ...................................................... 63 Table 4-2: SWM Facility Survey Summary............................................................................................. 66 Table 4-3: SWM Facility Project Recommendations and Costs .............................................................. 67 Table 4-4: Coastal Zone Improvement Projects – Cost Estimates .......................................................... 70 ii Marumsco Creek and Farm Creek PB Watershed Management Plan December 2009 EXECUTIVE SUMMARY This study presents a watershed-based analysis of the Marumsco and Farm Creeks that involves assessment of the conditions and resources within the watersheds. The primary objective of this study is to assess stream corridor and stormwater management (SWM) best management practice (BMP) conditions to develop conceptual plans that can be used to prioritize and plan Capital Improvement Projects (CIPs) within the Marumsco Creek and Farm Creek watersheds. This study