Sustainable Sites Initiative

Rehabilitation of Washington’s Headquarters at Valley Forge

Size & Type of Project:
Valley Forge (VAFO) Village area of 40 acres within VAFO National Historical Park; Greenfield and greyfield development

Location:
King of Prussia, Pennsylvania

Budget:
$2.2 million dollars (total landscape costs for both Phase I and II)

Project Phase:

• Phase I (completed Spring 2007) - center asphalt road removal and pedestrian path construction
• Phase II (due for completion June 2009) - lower parking lot removal, regrading, and native grass establishment; upper parking reconfiguration, ADA and bus drop, overlook and universal access path construction with stormwater terracing

Project Overview

General George Washington made his headquarters at Valley Forge, Pennsylvania during the Winter Encampment of 1777 and 1778. The historic headquarters building and surrounding area is now part of the Valley Forge National Historical Park which preserves the site and interprets the history of the Valley Forge encampment. The park encompasses approximately 3,500acres and is visited by over 1.2million people each year. The park also provides 26miles of hiking and biking trails, which are connected to a robust regional trails system.

Prior to the project, the site exhibited multiple layers of commemorative use.  The general spatial organization of the site vaguely reflected the historic patterns of field, pasture, orchard, and village lots.  A railroad line and train station physically and visually severed the area from the adjoining Schuylkill River, creating a barrier for visitors to understand why Washington chose this location as his headquarters.  Dozens of mature and declining commemorative trees, planted in the late 19^th and early 20^th century, blocked views to the headquarters building and contributed to shady, moist conditions for the historic structure.   Additional circulation routes, including paths, drives, and parking lots had been added in inappropriate locations, dissecting the site, obscuring historical patterns, contributing to excess amounts of impervious pavement on the site.   

In order to engage in preservation treatment of the landscape, archival research and field investigation was conducted to gain an understanding of the character, features and details of the Washington's Headquarters landscape as it evolved through time. Findings from this preliminary research noted issues involving visitor confusion and wayfinding with existing circulation routes and excessive amounts of parking. Because Washington's Headquarters at Valley Forge is a valued historic site, the project integrated preservation practices, integrated best management practices, and sustainability practices to protect the historic resources of the site and enhance woodland, meadow, soils, and stormwater treatment. The project included redesign of arrival and parking with removal of an oversize 1970s asphalt parking lot and redesign of a smaller lot.  The rehabilitation effort included changes to existing parking lots and circulation, enhancement of the cultural landscape, rehabilitation of the historic Valley Forge Train Station as a visitor orientation space, and the addition of interpretive elements on the history of the encampment and the village.

Site Context

Valley Forge is located within the Atlantic Coastal Pine Barrens Ecoregion which covers approximately 6,200 square miles of the coastal plain of New Jersey, Long Island in New York, and Cape Cod, Martha's Vineyard, and Nantucket in Massachusetts, as well as nearby islands. The region has a wide variety of ecological systems, including cedar swamps, meadows, stunted pitch pine and oak forests, sphagnum bogs, heathlands, coastal salt ponds, dune systems, and the Nation's only maritime grasslands on Martha's Vineyard and Long Island. Parts of the Ecoregion represent some of the best preserved habitat in the Eastern United States, but others are among the most highly developed lands in the country.

Valley Forge National Historic Park (NHP) is one of the largest open spaces in southeastern Pennsylvania with 3,500 acres containing habitats for hundreds of plants and animals including 200 species of birds. Washington's Headquarters, located in the northwest quadrant of the Valley Forge NHP, is situated at the confluence of Valley Creek with the Schuylkill River. The hill and valley landscape of this park, along the Schuylkill River and several creeks is managed principally in native meadow and in woodland with areas of memorial trees. Most of the project took place within green open space of the park, updating visitor facilities and infrastructure, and removing pavement to create more green open space.

This area receives on average approximately 47 inches of rainfall annually.  The warmest month of the year is July with an average maximum temperature of 87 degrees Fahrenheit, while the coldest month of the year is January with an average minimum temperature of 22 degrees Fahrenheit.

Landscape Treatment Plan from Cultural Landscape Report

Sustainable Practices

Sustainable Practices implemented or built to date

Protect unique cultural and historical places: The project team conducted both archival research and field investigation in the preparation of a Cultural Landscape Report (CLR)[1] for Washington's Headquarters at Valley Forge. The CLR informed landscape treatment recommendations that provided a solid foundation basis for preservation interventions and related landscape interpretation and management into the future. The primary thrust of this focused research effort was to gain an understanding of the character, features and details of the Washington's Headquarters landscape as it evolved through time in order to engage in preservation treatment of the landscape. In addition to preserving and celebrating history, preservation of an existing place inherently recycles and reuses embodied energies of a place.

[1] A Cultural Landscape Report is a report prepared by qualified professionals that documents the history, significance and treatment of a cultural landscape. A CLR evaluates the history and integrity of the landscape including any changes to its geographical context, features, materials, and use.  A CLR will often yield new information about a landscape's historic significance and integrity, even for those already listed on the National Register.

Sustainable Practices in construction phase

Providing for optimum site accessibility, safety, and wayfinding: Findings from the Cultural Landscape Report noted issues involving visitor confusion and wayfinding with existing circulation routes and excessive amounts of parking. CLR recommendations are being implemented in a two phased construction to address these issues regarding visitor circulation, arrival experience, site interpretation sequence, and the commemorative landscape involving Washington. Restoration of the historic train station located on the site is also being undertaken as part of this phased construction to enhance visitor experience. Phase 2 is currently under construction to reroute the visitor arrival sequence from initial parking to site orientation and interpretation. Parking for the site is being accommodated with redesign of the smaller existing parking lot uphill, which will be reorganized and realigned for easier access. The topography of the lot has been altered to keep vehicles out of the viewshed of the historic core.

Promoting sustainability awareness and education: Several locations for interpretive markers were identified and an interpretive sequence was proposed throughout the site. Site interpretive themes and educational elements are currently being more fully developed by the park and an interpretive planner.

Preserving special status trees: The project team identified and saved existing commemorative and historic trees by age and location in the village area. Existing trees were inventoried and coded based on tree genus and species, and condition of canopy, trunk, and root systems. Together, the codes accurately depicted tree conditions, which were then used to select trees for removal. Trees in poor health, trees that posed hazards to the historic structure and visitors, and trees of invasive species were removed. Remaining trees were then pruned and fertilized.

During the construction process, protection areas were identified and high visibility construction fencing and silt fencing were used to mark these protection zones and protect the remaining trees.

Removing invasives: Invasive species were identified during the vegetation inventory process, and were primarily located along the steep railroad embankment. Focused areas were preselected for targeted removal. The common invasive species, Tree of Heaven/Ailanthus altimssima were manually cut and removed from the railroad embankment slope to provide views of the Schuylkill River. Stumps of the trees were not removed, but were buried to maintain the integrity of the slope. The slope was graded, stabilized with biodegradable jute mesh and overseeded with native grasses.

Protecting and restoring vegetation and soil health: Designed into the construction process was the goal of low landscape impact by establishing clear maintainable landscape types based on vegetation typology, management, and reuse of existing soils on site. Landscape types included meadow for wildlife habitat, mixed turf species for a rougher, more historical appearance, and stabilized turf grass for limited service vehicles and emergency access. Overall efforts were made to reduce intensive turf grass maintenance. Meadow areas require less maintenance efforts over the long term, needing mowing every two years.

In addition, the project team utilized traditional and innovative soil erosion control techniques, amended and reused existing soils, and limited imported soils. Cut and fill from earthworks operations was balanced by taking excess soils from the upper parking lot to restore the historic topography in the area of the removal of the large lower parking lot. Excavated soils for the reorganized parking area and stormwater terraced vegetation basins were managed and amended for reuse to establish historic grades in the lower area of fill for the large parking lot which was removed. Determination of appropriate soil characterizes involved testing for physical and chemical properties of the existing soil to be reused and testing of amended soils. Testing included identifying standard nutrient and organic levels, particle size distribution, bulk density and percolation rate that was used to determine appropriate amendments to correct soil deficiencies.

Managing stormwater/ Reducing impervious surfaces: The overall project significantly reduced impermeable surfaces within the Valley Forge Village project area. Phase 1 of the project focused on removing an asphalt road that bisected the historic site, helping to reduce the amount of impervious pavement on the site, eliminate vehicular access in the core of the historic area and restore the historic landscape. Phase 2 involves removing the two-acre parking lot from the core of historic site further reducing impervious paving and allowing for increased stormwater infiltration throughout the area. Surface runoff from the new smaller upper parking area and related drives is captured in a series of shallow, terraced basins that descend downslope from the parking lot to the Washington's Headquarters site. These shallow basins were sized for a 25 year storm event and are vegetated with native meadow grasses that filter the surface runoff, slow water velocity, and allow water to percolate into the soil. Stormwater is piped from the parking lot to the first basin for ground infiltration. As the first basin is filled, the water flows through a stabilized spillway into a second vegetated basin where the infiltration process continues. To accommodate larger less frequent storm events three additional basins are located downslope to allow capture and infiltration of stormwater run-off from the parking lot. The amended soils within each basin were specified for permeable soils at 4 inches per hour infiltration rate which allows the water to infiltrate into the soil.

Procuring of local materials: The project involved substantial reorganization of site circulation and topography, with a large portion of the project consisting of earthworks and concrete construction. Locally available suppliers for gravels and borrowed soil and soil amendments were selected. Additionally, concrete manufacturers and metal fabricators were also selected for the project, relying on regionally available skills sets and raw materials as opposed to using imported concrete color mixes or finished surface materials.

Construction Cost

Total cost for Phase I, $336,000. Total building and landscape costs for Phase II, $4,200,000, which includes the restoration of the historic train station and construction of a new restroom facility. Total landscape costs for both Phase I and II, $2.2 million dollars. Costs for implementing sustainable practices are similar to conventional costs.

Monitoring Information

Maintenance

For maintenance regimes, meadow grasses require mowing once every two to three years, rather than once every week or every other week, thus reducing the costs of fuel for mowing and staff efforts. Woodland management requires inspection on a regular interval to monitor for invasive species with two reviews spring and fall each year. Stormwater maintenance for the shallow stormwater basins requires monitoring as the meadow grasses become established to address and stabilize surface erosion. Once grasses are established, monitoring will occur after substantial rain events to check for basin damage in terms of soil erosion.

Management strategies for woodland, meadow, soils, and stormwater treatment were selected based in part on client goals, reduced construction costs, reduced maintenance costs, and good stewardship practices on behalf of the nationally significant historic landscape.

Universal access for visitors from the overlook area.

Issues/Constraints of the Site

Unique constraints included working within the existing condition and character to preserve this nationally significant historic site and the park legacy for future generations, while balancing the National Park Service mandate to provide site access for all.  Multiple laws and legal constraints of local and state governments provided design and compliance challenges.  Additionally, archeological investigations were undertaken to document and recover below ground Encampment era artifacts.   Sustainable practices had to be weighed against historic preservation and commemoration objectives for a balanced outcome.

Lessons Learned

Sustainable practices and best management practices for meadow, soils, and stormwater treatment can be balanced with preservation of a historic site in a thoughtful and meaningful way that also adds to the interpretative opportunities for visitors.

More project details

http://www.nps.gov/vafo/planyourvisit/hqprojects.htmwww.heritagelandscapes.com  Valley Forge project summary and in progress focus.

Project Consultants

Preservation Landscape Architect & Planner:
Patricia M. O'Donnell, FASLA, RLA, AICP
Heritage Landscapes LLC

Preservation Landscape Architect:
Peter Viteretto, ASLA, RLA
Project Manager, Sr. Associate
Heritage Landscapes LLC

Civil Engineer:
Brent Jones, PE
Federal Program Manager
HDR, Inc.

Preservation Architect:
Christina Carter, AIA
Project Manager, Sr. Associate
John Milner Architects