Williamsburg Boulevard Green Streets Project. April 27, 2011 Williamsburg Middle School

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1 Williamsburg Boulevard Green Streets Project April 27, 2011 Williamsburg Middle School

2 What is a Green Street? A green street incorporates facilities that reduce the impact of polluted runoff on our streams and the Chesapeake Bay.

3 Rain Gardens A landscaped depression with the ability to capture, temporarily retain, and filter surface runoff A rain garden is a storm water treatment facility. Fairlington Community Center Also known as: Bioretention, Biofilter, Bioretention Filter, Bioretention Basin

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10 Residential Rain Garden Runoff Plants Ground surface 6-12 ponding area 3 mulch 1-2 planting soil

11 Bioretention Rain Garden Runoff Plants Overflow str Water Surface Ground surface 6-12 ponding area 3 mulch 2-3 soil underdrain 4-6 pea gravel 1-2 coarse gravel

12 Why Rain Gardens? Traditional stormwater management isn t as effective at protecting water quality. Many localities are using new stormwater management techniques where possible to improve water quality. Woodmont

13 Most of Arlington County developed without stormwater management Storm drain to local stream To the Potomac River Water in storm drains does not go to a treatment plant On to the Chesapeake Bay

14 Effect of Urbanization Impervious surface Runoff speed and volume Water Quality Groundwater supply Stream Corridor Restoration, FISRWG, 1998 Stream health

15 Impacts from Stormwater Runoff Potomac River is our source of drinking water. Stormwater runoff erodes local streams, carrying sediment downstream, killing trees, and damaging sewer lines.

16 Regulatory Requirements Virginia Stormwater Permit requires us to reduce stormwater pollution from existing and new development. Permit requirements are becoming more stringent. Chesapeake Bay TMDL in development. Master Transportation Plan includes recommendations for street trees and reduction of stormwater runoff.

17 Chesapeake Bay TMDL Required Pollution Reductions Nitrogen 25% Phosphorus 24% Sediment 20% Arlington Statistics 7125 acres of rooftop & pavement ~3500 acres to be treated by 2025

18 Impervious cover in Arlington County Alley 0.2% Airport 3.8% Handicap ramp 0.1% Driveway 7.4% Buildings 30.1% Parking lot 15.7% Paved median 0.6% Sidewalks 8.4% Roads 33.8%

19 Stormwater Master Plan Update Storm Sewer Capacity Analysis County-wide stream inventory Watershed retrofit plans to identify locations where stormwater treatment facilities can be added to help slow down and filter stormwater runoff. Each plan contains an inventory of projects. Rain gardens Removing pavement/impervious surface Little Pimmit Run Watershed Retrofit Plan alservices/cpe/page75627.aspx

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22 Project Components Two square foot rain gardens between 33 rd and 34 th Rds N New curbs, improved intersections and repaving New canopy trees between Old Dominion Dr. and 33 rd Rd N and between 35 th St and 34 th Rd N.

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25 Williamsburg Rain Gardens A 4 sections B 3 sections AS- Allegheny Serviceberry; RB Red Buckeye

26 Williamsburg Rain Gardens A 4 sections B 3 sections

27 Williamsburg Rain Gardens

28 Rain Garden Drainage Areas Total drainage area: 1.8 acres Impervious area treated: 1.1 acres Water treated: 5310 ft 3 (39,718 gallons) A B

29 Williamsburg Bioretention Typical Cross-Section 13 6 plants 6 curb Max 3 underdrain 3 mulch 3 soil 3 pea gravel 1 gravel

30 Trees and Plants 12 trees and 2 shrubs will be removed Includes 3 mature trees (> 10 dbh) all exhibiting signs of stress 7 canopy trees; 9 small trees and multiple shrubs will be planted Numerous flowering perennials, grasses and vines All plants will be native, salt tolerant

31 Red buckeye Smooth blue aster Obedient plant Blackeyed susan Little bluestem Winterberry Beardtongue Pachysandra

32 Concrete weir Curb cut Pipe 5-8 River Rock Concrete weir 3-5 River Rock

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34 Maintenance Initially, after any large storms Thereafter, quarterly Remove sediment Weed, inspect, replant, prune plants Remove trash Make sure underdrain, overflow all working correctly

35 Next Steps Choose plants and finalize planting plan Peer engineering review and subsequent revisions Utilities Construction: Fall-Winter 2011

36 Green Streets Projects 209 projects identified to date 1 in construction Patrick Henry Dr (at 9 th Rd N) median bioretention 7 projects in planning or design Williamsburg Blvd median bioretention Old Dominion to 35th St N Harrison to Edison N (NC project) Kensington Blvd & 32 nd St N streetscape bioretention John Marshall Dr median bioretention Patrick Henry Dr (at Inglewood) street bioretention 8 th St S streetscape bioretention Pentagon City streetscape & median bioretention

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38 Questions?? Contact info: Phone: (703) Web: Residents Environment Watershed Management mentalservices/epo/page74076.aspx