U.S. Coast Guard Headquarters

The U.S. Coast Guard headquarters site was faced with a fly ash contaminated steep slope within an area of Washington, D.C. that is protected for visual quality. Protection of the sloping green fringe around the city, or “Green Bowl” as it is known, meant designing the facility with a low profile that blended into its surroundings. The aging stormwater system serving the area had a history of being overloaded, leading to frequent incidences of flooding. Like any large urban facility, concerns about heat island and other negative socio-environmental effects were magnified by the massive scale of the project.

Solution

To meet the significant challenges facing the U.S. Coast Guard headquarters site, the designers used a less traditional approach. Rather than a large monolithic icon, the building mass was instead arranged in a series of low profile interconnected units that emerge more subtly from the hillside to form protected courtyards for workplace gatherings or casual meetings. Extensive and intensive green roofs on top of the builidngs mitigate viewshed impacts, capture stormwater, lower heat gain, and provide habitat. Excess stormwater flows down the green roof and courtyard terraces to a retention pond, where it is recirculated through a series of fountains and wetlands and used for site irrigation. 

• The stormwater management system includes a stormwater retention pond, a network of 18 green roofs, two constructed wetlands, and 7 bioretention areas around buildings and within courtyards.
• The buildings are covered with a total of 400,000 sf of vegetation on 18 separate yet interconnected green roofs. The green roofs are of different depths and soils mixes with over 25,000 sedum plugs and a range of grass and native perennials used. 
• The green roofs incorporate areas of gravel pockets to provide nesting habitat for Killdeer, a small ground-nesting bird. 
• Eight interconnected courtyards features native vegetation and hardscape that calls out the character of five D.C.-area eco-regions: Blue Ridge, Piedmont, Northern Piedmont, Southeastern Plains, and Middle Atlantic Coastal Plain. 
• Some of the courtyards serve as outdoor hallways, while others feature seating and shade structures to serve as spaces for lunch or meetings.
• A 2.4-acre stormwater retention pond was designed to capture and hold runoff from up to the 25-year rain event. The pond includes vegetated shelves to treat the water and enriched habitat. All site-based irrigation and water features are sourced from this pond.
• A total of 247,462 individual plants from 104 native species were planted on the site. Species include: Asclepias Syriaca (Common Milkweed), Aster Ericoides (Heath Aster), Aster Oblongifolius (Fall Aster), Baptisia Tinctoroa (Yellow Wild Indigo), Danthonia Spicata (Poverty Oat Grass), Eragrostis Spectablis (Purple Love Grass), Eupatorium Hyssopifolium (Thoroughwort), Trandescantia Ohiensis (Ohio Spiderwort), and Allium cernuum (Nodding Wild Onion). 
• Hundreds of historic trees were preserved, in addition to the 985 individual trees from 34 native species that were planted.
• Bald eagle nesting area was protected by moving a security fence and removing a second helipad from the design. Bald eagles are regularly observed on the site.
• North of Headquarters buildings, bioswales with check dams direct stormwater flows down the slope.
• Reforestation along the north slope of the site helps to purify air and water, while providing habitat for surrounding wildlife. 
• The public bus stop, serviced by two bus lines and a multi-use path at Gate 4, provide employees with low-carbon, sustainable options for commuting. 

• Discordant landscape aesthetics with some U.S. Coast Guard personnel led to the mowing of areas intended to be tall grass. Earlier engagement with USCG personnel regarding key landscape functions may have helped ensure that the site would be maintained in accordance with the design intent.
• Unexpected algae growth in the stormwater retention pond resulted in algaecides being used during summer 2014 and 2015. It may have been beneficial to plan for managing algae growth until the constructed wetland plants were fully established.
• A lack of regular weeding in the courtyard beds during 2014 resulted in many installed plants being outcompeted, thus necessitating the replacement of many lost plants. 
• In the first few years following the site’s completion, the landscape managers pruned the  meadow grass vegetation on the green roof during the fall season, rather than leaving the plants standing on the roof until late winter. Late winter removal was recommended for two reasons: (1) to provide shelter and food for wildlife into the winter, including bald eagles, and (2) to provide plant cover to mitigate the visual impact of the building during the fall and early winter. A landscape management plan would have helped to better communicate the design intent of the green roof plantings and coordinate vegetation removal.
• Canada geese were a nuisance during construction. While geese protection was not included in the construction drawings and specifications, it could have prevented vegetation losses along the pond edge.
• Native plant material was difficult to find locally in large quantities. More advanced plant procurement coordination and contract growing would have made it easier to procure plant material from more local sources.

Site Furniture
Trash Receptacle: Sitescapes-Cambridge
Citrus Table, Vista Chair: Forms and Surfaces  
Flag Pole: Baartol Company

Lumber and Decking
Wood Boardwalk: AltruwoodIpe 

Fencing, Gates, Walls 
Ipe Wood Benches: Altruwood
Garage Planters: Palmetto Planters
Corten Steel Wall: AIW, Inc. 

Stone
Boulder: Champlain Stone
River Stone, Mexican Beach Pebbles: Hudson River Stone
Aggregate Stone: Aggregate Industries
Granite Edge: Coldspring

Soils
Organic Compost Material: Recycled Green

Planting
Bio Fiber Log: Rolanka International, Inc. 
Metal Edge: Gordon Contractors
Shredded Bark Mulch: Grant County Mulch
Burlap Weed Blocker: Wholesale Erosion & Landscape Products
Meadow and Wildflower Mix, Woodland Wetland Mix, Woodland Upland Mix, Hydroseed
Semper Green, Sedum Mat: Ernst Conservation Seeds, Inc. 
Trees, Shrubs: Myers Cove Nursery
Trees: Hawkersmith & Sons Nursery
Trees: Cleveland Tree Company Nursery
Trees: Tucahoe Nurseries
Trees: Little River Nursey
Trees: Three AM Growers Nursery
Trees: Charlies Creek Nursery
Trees: Fort Mcnair, Washington, D.C. 
Shrubs: American Native Plants
Shrubs: Carolina Native Nursery

Roof
Green Roof Soil: Rooflite
Geoedge: Permaloc

Water Feature
Water Feature Design: Bradford Products

Drainage Erosion
East Coast Erosion Blanket: ECS2
Ornamental Grate: Neenah Foundry 

Hardscape
Grass Pavers: Tufftrack 

Irrigation
Weather Station, Control Station: Rainbird
Lighting: Bega
Lighting: Kim
Lighting: Lumec
Lighting: Hess
Lighting: Spaulding

Project Team

Client: U.S. General Services Administration
Design Excellence Landscape Architect: Andropogon Associates, Ltd
Design/Build Landscape Architect, Interiors, Sustainability: HOK
Landscape Project Team: Todd Montgomery 
Preservation Landscape Architecture: Heritage Landscapes LLC
Landscape Contractor: ValleyCrest
Design Excellence Architect: Perkins + Will
Design/ Build Architect of Record, Headquarters Building: WDG Architecture, PLLC
Design/ Build Architect of Record, Garage/Support Building: Mckissack & Mckissack 
Engineering Design Build Team: GIRARD Engineering, MEP
Structural Engineering Design Build Team: Cagley & Associates, Inc.
Civil Engineering Design Build Team: Loiederman Soltesz Associates, Inc.
Civil Engineering: William H. Gordon Associates, Inc.
Survey and Civil Engineering: Greenhorne & O’Mara
Hydrogeological Investigations: GeoConcepts Engineering, Inc. 
Soil Scientist: Craul Land Scientists
Ecologist/Environmental Biologist: Continental Conservation
Arborists: Morris Arboretum
General Contractor: Clark Construction
Design/Build Lighting Designer: MCLA
Design/ Build Historic Consultant: Quinn Evans

Role of the Landscape Architect

Andropogon was the “Design Excellence Landscape Architect” creating the fundamental concepts and layout for the site with the help of the entire Design Excellence team of engineers, scientists, and architects. This team included Heritage Landscapes LLC, who worked with Andropogon to help them better understand the role of historical preservation in the project. HOK was the “Landscape Architect of Record” working as part of a Design Build team of engineers, architects, and contractors to create contract documents for the project and provide construction administration services throughout the building of the project.