Bloomingdale Neighborhood Flooding Mitigation Washington, DC

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1 District of Columbia Water and Sewer Authority George S. Hawkins, General Manager Briefing on: Bloomingdale Neighborhood Flooding Mitigation Washington, DC Briefing for: Federal Water Quality Association December 12, 2013

2 Agenda Background on DC Clean Rivers Flooding in the Northeast Boundary Sewershed 2012 Flood Events & Mayor s Task Force Northeast Boundary Neighborhood Protection Project 2

3 Background DC Combined Sewer System Bloomingdale 1/3 of DC area is served by combined sewers (12,478 acres) 53 CSO outfalls 15 to Anacostia 10 to Potomac 28 to Rock Creek Three receiving waters Anacostia River Potomac River Rock Creek Long Term Control Plan = DC Clean Rivers Project 3

4 Anacostia River Projects: Implementation on Schedule 4 large storage/conveyance tunnels First 1 Street Tunnel, Nov Mar Jan Bloomingdale NE Boundary Tunnel and area projects, $606M Mar 2016 Mar Dewatering pumping station at Blue Plains Pumping station replacement at Poplar Point Schedule LTCP = 20 years ( ) Nitrogen Removal = Cost LTCP = $2.6 billion Nitrogen Removal = $950 M Total > $3.5 billion Potomac River U.S. Capitol Building Nationals Park Joint Base Anacostia- Bolling Blue Plains Tunnel, $397M Sept 2011 Nov 2015 Before 2018 Anacostia River After 2018 RFK Stadium Anacostia River Tunnel, $253M $291M Nov 2013 Sept 2017 DC Water Blue Plains AWWTP 4

5 Northeast Boundary Tunnel CSO storage and flood conveyance tunnel Flood relief = uniform 15-year 6-hour storm (per NOAA) Provide flood relief to 5 chronic flooding areas Relieve NEB trunk sewer from RFK to 6 th Street & R Street, NW Allowances for future connections Other NEB areas may not meet 15-year design standard; can be addressed by future connection to tunnel (not DCCR project) Configure the system to operate by gravity (no gates or controls) 2025 completion per Consent Decree Known Chronic Flooding Areas W. Virginia & Mt Olivet Rhode Island Metro First & P St, NW Capacity of Current System (Storm Frequency) Less than 2 yr Less than 2yr Less than 5 yr Characteristic Bowl Bowl Bowl Bloomingdale Less than 5 yr Bowl 6 th & R St NW Less than 5 yr Bowl 5

6 Background NEB Drainage Area Northeast Boundary Drainage Area (NEB) serves the Bloomingdale neighborhood Part of the District s Combined Sewer System One (1) pipe in street serves both sanitary collection and storm water runoff Built-out in the early 1900s Northeast Boundary Trunk (NEBT) Sewer Major sewer serving the NEB Drainage area Constructed circa Bloomingdale Drainage Area >700 acres Bloomingdale U.S. Capitol Building RFK Stadium 6

7 Background History of Flooding Flooding occurred soon after NEBT Sewer construction Recognition that sewer capacity was too low Many studies have identified longstanding flooding issues in Northeast Boundary 1955 Sewer Investigation 1957 Board of Engineers 1968 Burns & MacDonald 1997 Alignment Study 1999 NEB Flooding Study 2002 CSO Long Term Control Plan 2006 Bloomingdale Flood Study 1860 s Map of DC Bloomingdale (Thomas & Flagler) is the old stream valley 7

8 Background Why was Flooding not Addressed in the Past? Bloomingdale Massive scale of project Not constructible without large disruption to neighborhoods and existing infrastructure unless tunneling is used New tunneling technologies have made soft ground tunneling practical Existing NEBT Sewer Section (10-0 Diameter) Existing NEBT Sewer Section ( ) 8

9 2012 Flooding in Bloomingdale And LeDroit Park 1 st & P St NW (2001) Rhode Island & T St NW Rhode Island & 1 st St NW Rhode Island Metro Rhode Island & T St NW Flagler St NW Rhode Island Between 1 st & 2 nd St 1 st & V St NW 9 9

10 June/July 2012 Storm Events Intensity Analysis Peak Intensity of June/July 2012 Storms Date Duration Rainfall (inches)* Approx. Precipitation Frequency 7/10/ hour year storm 7/18/ minute year storm 7/19/ min year storm 9/2/ hour year storm NOTES: *Bryant Street Station Rain Gauge N.B. Radar data confirmed the measured intensity of the three July storm events 10

11 Recent Flooding has Severely Impacted Residents Major flooding July 10, 18, 19 and Sept 2, 2012 More than 200 property owners affected Flood clean-up costs $3,000-$18,000 per household Concerns about public health and safety 11

12 Bloomingdale Topography Flow from North to South McMillan Sand Filtration Site is upstream of Bloomingdale residential area Flow funnels to Flagler and 1 st Streets NW. Medstar Hospital Old Soldiers Home VA Hospital McMillan Sand Filtration Site Bloomingdale Residential Area

13 Modeling Results July 10 th Storm Event Choke point causing upstream flooding Surface Flooding Predicted Rhode Island Avenue Flooding 13

14 Modeling Results Store as much flow as possible upstream of and within Bloomingdale Increase capacity through Bloomingdale Increase capacity downstream of Bloomingdale

15 Three-step Infrastructure Plan To Mitigate Flooding 1 McMillan Site, LID, Backflow Prevention 3.1 million gallons (Existing abandoned filter cells) 1 2 First Street Tunnel 8.9 million gallons (2,800 LF, Min 18.5 I.D.) 2 3 Northeast Boundary Tunnel (23 I.D.) 3 NEBT (Future) 15

16 Schedule Place McMillan tanks in service by March 2014 to be ready for spring / summer storms Proj. Activity McMillan Stormwater Storage + Backflow Prevention Program 2 First St Tunnel (Div P) 3 Northeast Boundary Tunnel (Div J) 16

17 Three-step Infrastructure Plan To Mitigate Flooding 1 McMillan Site, LID, Backflow Prevention 3.1 million gallons (Existing abandoned filter cells) 1 2 First Street Tunnel 8.9 million gallons (2,800 LF, Min 18.5 I.D.) 2 3 Northeast Boundary Tunnel (23 I.D.) 3 NEBT (Future) 17

18 Filter Cell No. 14 After Sand Removed Photo taken May

19 McMillan Stormwater Storage Overall Site Plan DCCR First Street Tunnel Shaft & 3-acre staging area Storage Tank Online by Spring 2014 Sewer Diversions Tank Rehab Upstream Sewer Rehab In Service: until

20 First St North Capitol St. North Capitol St. First St How will McMillan Storage Tank and Sewer Diversions Work? Dry Weather & Moderate Storms No flow to Cell 14 or Tunnel Major Rain Events Cell fills & empties by gravity North Service Court North Service Court Tunnel fills by 15 gravity and is emptied by temp. pump station South Service Court South Service Court Tunnel Shaft Tunnel Shaft Flow uses existing pipes Storms that exceed the capacity of the storage tank and tunnel continue downstream 20

21 Trunk Sewer Profile HGL During Larger Storms Approaches Grade in Surrounding Service Area When Storage is Full and Weir Overtops Diverted to Storage Tank and Tunnel by Surcharging Upstream Sewers to Fill by Gravity Two Options: Automated Gate Vortex Flow Control Device 21

22 North Capitol Street Sewer Diversion: Construction Staging Outside travel lane used for offloading materials and equipment Materials staging area in McMillan site adjacent to N. Capitol Street Site occupies 2 travel lanes in North Capitol Street (6 lanes total) Night work required Diversion Chamber 20 Inside Diameter 22

23 North Capitol Street Sewer Diversion: Diversion Chamber Construction New 48 diversion sewer to tank Temporary flow maintenance Rebar for overflow weir Existing 60 storm sewer Timber lagging support of excavation Photo taken September

24 Low Impact Development Rain barrel and cistern rebate program Administered by DC Greenworks for DDOE and DC Water Irving Street LID Project 24

25 Backflow Prevention Program BWV Rebate Program Current Program Area includes Bloomingdale neighborhood & 2/3 LeDroit Park neighborhood Task Force Recommendation Expanded boundary including all of Northeast Boundary drainage area upstream of N. Capitol St. and Florida Ave. New Program Alternative 1: Area defined by Legislative boundary in DC Act Area includes Bloomingdale, LeDroit Park, and additional Florida Ave Alternative 2: Expanded boundary Area includes all of Northeast Boundary drainage area upstream of N. Capitol St. and Florida Ave. Floodproofing Rebate Program Current program No rebate offered, but engineering consultations available to Bloomingdale & LeDroit Park residents Task Force Recommendation Expanded boundary including all of Northeast Boundary drainage area upstream of N. Capitol St. and Florida Ave. New Program Alternative 1: Properties in Bloomingdale & LeDroit Park neighborhoods with reported overland flooding during 2012 storms Alternative 2: Area defined by Legislative Boundary in DC Act

26 Backflow Prevention Program Determine the nearest trunk sewer for each property 26

27 Backflow Prevention Program Estimate Basement Elevations and Depth of Sewage 27

28 Backflow Prevention Program Compare Basement Elevation to HGL 28

29 Three-step Infrastructure Plan To Mitigate Flooding 1 McMillan Site, LID, Backflow Prevention 3.1 million gallons (Existing abandoned filter cells) 1 2 First Street Tunnel 8.9 million gallons (2,800 LF, Min 18.5 I.D.) 2 3 Northeast Boundary Tunnel (23 I.D.) 3 NEBT (Future) 29

30 First Street Tunnel Min 18.5 diameter, 2,800 long Acts as storage tunnel 2022, then connects to Northeast Boundary Tunnel Contract awarded in operation Oct 2016 Block meetings held with residents this summer 30

31 Three-step Infrastructure Plan To Mitigate Flooding 1 McMillan Site, Local Storage, Backflow Prevention 3.1 million gallons (Existing abandoned filter cells) 1 2 First Street Tunnel 8.9 million gallons (2,800 LF, Min 18.5 I.D.) 2 3 Northeast Boundary Tunnel (23 I.D.) 3 NEBT (Future) 31

32 Northeast Boundary Tunnel First St Tunnel Bloomingdale Completion date accelerated from 2025 (Consent Decree) to 2022 (Mayor s Task Force) 23 diameter, about 5 miles long On schedule RFP under preparation Alignment improvements being made to minimize property impacts Provide storage for 15-year storm before treatment Northeast Boundary Tunnel Blue Plains Tunnel (Construction) Anacostia River Tun. (Construction) Tunnel Dewatering Pump. Station and ECF (Construction) 32

33 Summary Northeast Boundary Tunnel planned to provide protection from CSOs and flooding. Large storms in 2012 accelerated the schedule for NEBT and other solutions in Bloomingdale. Implementing 3-step plan to provide protection ASAP to Bloomingdale while moving forward with the NEBT. 15-year storm protection by 2022 in Bloomingdale and other areas. 33

34 Contact Essey Woldemariam DC Water, Planning Department Steve Skripnik, PE LimnoTech, DC Clean Rivers Project 34