WHITE FLINT METRORAIL STATION NORTH ENTRANCE FEASIBILITY STUDY Final Report Montgomery County, Maryland November 2019 September 8, 2017 [This page intentionally left blank] White Flint Metrorail Station North Entrance Feasibility Study Final Report November 2019 Lead Agency Washington Metropolitan Area Transit Authority Office of Planning 600 5th Street NW Washington, DC 20001 Shyam Kannan, Managing Director of Planning Robin McElhenny, Program Manager of Station Planning Sara Benson, Project Manager [This page intentionally left blank] White Flint Metrorail Station North Entrance Feasibility Study Table of Contents Executive Summary ........................................................................................................................... ES-1 1. Introduction ................................................................................................................................. 1 1.1 Study Purpose and Overview ............................................................................................ 1 1.2 Background ...................................................................................................................... 1 1.3 Study and Design Process ................................................................................................. 3 1.4 Report Organization ......................................................................................................... 3 2. Station Profile .............................................................................................................................. 4 2.1 Project Location and Description ...................................................................................... 4 2.2 Station Area Planning and Development Context.............................................................. 5 2.3 Previous Station Planning Studies ..................................................................................... 7 2.4 Site Visit and Existing Conditions ...................................................................................... 9 3. Demand Assessment.................................................................................................................. 15 3.1 Ridership Forecasting ..................................................................................................... 15 3.2 Pedestrian Activity (Rockville Pike & Old Georgetown Road Intersection) ....................... 17 4. Engineering Feasibility ............................................................................................................... 19 4.1 Design Criteria ................................................................................................................ 19 4.2 Architecture ................................................................................................................... 19 4.3 Elevator Evaluation......................................................................................................... 26 4.4 Geotechnical .................................................................................................................. 29 4.5 Structure ........................................................................................................................ 30 4.6 Mechanical ..................................................................................................................... 40 4.7 Electrical......................................................................................................................... 43 4.8 Plumbing ........................................................................................................................ 46 4.9 Utilities ........................................................................................................................... 49 4.10 Egress Analysis ............................................................................................................... 50 5. Environmental Scan ................................................................................................................... 52 5.1 Environmental Considerations ........................................................................................ 52 5.2 Environmental Resources ............................................................................................... 53 6. Constructability and Risk Assessment ........................................................................................ 59 Final Report i November 2019 White Flint Metrorail Station North Entrance Feasibility Study 6.1 Constructability Review .................................................................................................. 60 6.2 Risk Assessment ............................................................................................................. 65 7. Rough Order of Magnitude (ROM) Capital Cost Estimates ......................................................... 66 7.1 Soft Cost Assumptions .................................................................................................... 66 7.2 Estimating Assumptions ................................................................................................. 66 8. Preferred Alternative ................................................................................................................. 67 8.1 Preliminary Design Approach .......................................................................................... 68 8.2 ROM Capital Cost Estimate ............................................................................................. 73 8.3 Design Considerations for Preliminary Engineering (PE) .................................................. 73 List of Figures Figure 1-1 | White Flint Metrorail Station Location .................................................................................. 2 Figure 1-2 | Study Process ....................................................................................................................... 3 Figure 2-1 | Future bridge across WMATA tracks and station platform .................................................... 7 Figure 2-2 | Improvement 2A – 2010 White Flint Station Access Plan ...................................................... 8 Figure 2-3 | Existing North Service Rooms – Platform Level ................................................................... 10 Figure 2-4 | Cross Section – Platform North End Wall ............................................................................ 11 Figure 2-5 | Cross Section – North Service Rooms & Adjacent Train Tunnels .......................................... 12 Figure 2-6 | Longitudinal Section – North Service Rooms ....................................................................... 13 Figure 2-7 | Photo of Existing Tunnel Structure at North End of Station ................................................. 14 Figure 2-8 | Photo of Existing South Station Entrance ............................................................................ 14 Figure 4-1 | Revised North Entrance Configuration ................................................................................ 22 Figure 4-2 | Roof Plans .......................................................................................................................... 24 Figure 4-3 | Mezzanine Structural Approaches ...................................................................................... 25 Figure 4-4 | Geotechnical Subsurface Profile ......................................................................................... 30 Figure 4-5 | Cross Section of Existing South Mezzanine – Slab on Grade ................................................ 31 Figure 4-6 | Cross Section of Existing Platform – Canopy Columns Supported on Invert ......................... 32 Figure 4-7 | Site Visit Photo – Platform Manhole Removed with Standpipe Visible ................................ 33 Figure 4-8 | Long Section of Existing Cut-and-Cover Tunnel – Finished Grade Depth of 1.5’ ................... 33 Figure 4-9 | Site Visit Photo – Additional Soil Cover Over Existing Tunnel: Looking North ....................... 34 Figure 4-10 | Site Visit Photo – Additional Soil Cover Over Existing Tunnel: Looking South ..................... 34 Final Report ii November 2019 White Flint Metrorail Station North Entrance Feasibility Study Figure 4-11 | Cross Section of Existing Cut-and-Cover Tunnel ................................................................ 36 Figure 4-12 | Cross Section – Platform North End Wall Local Demolition ............................................... 37 Figure 4-13 | Ventilation Fan Units – North End Service Rooms ............................................................. 41 Figure 4-14 | North End Sanitary Drainage Below Inbound Track ........................................................... 49 Figure 5-1 | Project Location and Environmental Scan Study Area Map ................................................. 54 Figure 6-1 | Potential Construction Storage, Staging and Material Lay Down Areas ............................... 63 Figure 8-1 | Preferred Alternative Longitudinal Section ......................................................................... 69 Figure 8-2 | Preferred Alternative Platform Level .................................................................................. 70 Figure 8-3 | Preferred Alternative Mezzanine Level ............................................................................... 71 List of Tables Table 2-1 | Forecasted Station-Level Daily