NATIONAL PARK SERVICE 

CHAPTER 3.0 AFFECTED ENVIRONMENT 

 

 

For the purposes of this plan, the study area is the area considered to be directly influenced by 

the GMP/EIS. The study area for each affected resource includes this area but may extend 

outside to adjacent areas indirectly influenced by the GMP/EIS, depending upon the resource. 

 

3.1 LAND USE AND SOCIO-ECONOMIC CONDITIONS 

Land uses in the study area were inventoried to characterize the surrounding context of Great 

Falls Park. Land uses along with visitor activities within the park were also analyzed to 

understand how the park currently functions. Land use inventories for the park and 

surrounding area result from field observations and a review of aerial photographs of the area, 

contemporary and historic maps, Fairfax County’s comprehensive plan and zoning ordinance, 

and Montgomery County’s comprehensive plan and zoning ordinance. Visitor activities were 

characterized through use of an existing survey, field observations, and meetings with park staff. 

3.1.1 Land Use and Property Boundaries 

Land Use Patterns of the Surrounding Area

Great Falls Park is located in the northeast portion of Fairfax County, Virginia. This portion of 

Fairfax County consists of low-density, single-family residences, and open space uses. The 

Potomac River, under the State of Maryland’s jurisdiction, borders the park to the east. 

Montgomery County, Maryland, is located to the east of the river. Similar to Fairfax County, 

this area of Montgomery County, within proximity of the park, consists of open space uses and 

low density, single-family residences. 

The R-E (Residential Estate District) is the predominant zoning district adjacent to the park in 

Fairfax County. This district promotes agricultural uses, and low density residential dwellings at 

a density not to exceed one dwelling unit for every two acres. Other zoning districts within 

Fairfax County, that are located beyond the immediate surrounding area, include the R-A (Rural 

Agricultural District), R-1 (Residential District, one dwelling unit per acre), R-2 (Residential 

District, two dwelling units per acre), C-5 (Neighborhood Retail Commercial District), and C-8 

(Highway Commercial District). 

On the east side of the river, in Montgomery County, the RE-2 District (Residential, One-Family 

District) is the most prevalent zoning district in the area adjacent to the park. The district 

promotes low-density residential development. 

Surrounding roadways include Old Dominion Drive, which provides public vehicular access to 

the park, Georgetown Pike (Route 193), which connects to Interstate 495 (Capital Beltway) 

located approximately four miles to the south, and Riverbend Road which connects to 

residences to the west of the park. 

There are a number of open space uses including parks and trails adjacent to the park. To the 

north, Riverbend Regional Park provides approximately 400 acres of open space and shares a 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.2

portion of a common boundary with Great Falls Park. It is managed by Fairfax County Park 

Authority and includes a nature center, a boat ramp for private boat launches, a pavilion and 

picnic area, a playground for children, refreshment vending, and pedestrian and equestrian 

trails. The North River Trail, a multipurpose biking, hiking, and horseback riding trail within 

Great Falls Park, continues as a pedestrian trail into Riverbend Park. 

To the east, the Chesapeake and Ohio Canal National Historical Park (C&O Canal NHP), 

managed by the NPS, is located immediately east of the Potomac River in Maryland. The park 

preserves the C&O Canal, a cultural resource listed in the National Register of Historical Places 

that extends for 185 miles from Georgetown (Washington, D.C.) to Cumberland, Maryland. 

Activities available at the park include backpacking, bicycling, bird watching, boating, camping, 

climbing, cross country skiing, fishing, hiking, horseback riding, interpretive programs, 

kayaking, nature walks, and wildlife viewing. 

The Difficult Run Stream Valley Park, managed by Fairfax County Park Authority, is located to 

the west of the park, and Madeira School, a private boarding school, is located to the south. 

Other major open space uses, beyond the immediate surrounding area of Great Falls Park, 

include Spring Hill Recreational Center, and the Great Falls Grange Park (managed by Fairfax 

County), Scotts Run Nature Preserve (managed by Fairfax County Park Authority), and River 

Bend Golf and Country Club, a private facility. 

 

Land Use Patterns within Great Falls Park

Great Falls Park consists of two parcels, separated by Old Dominion Drive, which total 

approximately 800 acres. The larger parcel is shaped in a long and narrow configuration and 

located along the Potomac River. It extends for approximately 2.5 miles in the north-south 

direction, and varies between approximately 800 feet at the narrowest location, and 3,400 feet at 

the widest location. The smaller parcel is somewhat triangular in shape. Its longest side 

borders Old Dominion Drive and extends approximately a half-mile in the north-south 

direction. 

The park includes wooded areas, developed areas, cultural resource areas, and recreational 

areas. These are located as follows: 

• Wooded Areas: The wooded areas cover most of the park. These include the park 

property to the west of Old Dominion Drive, most of the area to the west of the Old 

Carriage Road Trail, the area to the south of where the Patowmack Canal meets the 

Potomac River (canal cut area), the area north and west of the northern parking lot, and 

portions of the area to the east of the Patowmack Canal. 

• Developed Area: The developed area is located towards the northern portion of the park 

and consists of three parking areas, a visitor center, maintenance facility, a law 

enforcement trailer, a comfort facility, and an entrance station. The maintenance facility 

is a fenced in area located near the entrance of the park that includes a single-storied 

structure where maintenance equipment is stored, and four temporary structures that 

house additional maintenance equipment and interpretive supplies. The law 

enforcement trailer provides offices for U.S. Park Police (USPP) personnel. See Figure 

1.3: Park Facilities. 
AFFECTED ENVIRONMENT 

3.3 NATIONAL PARK SERVICE 

 View of the Potomac River with C&O Canal NHP in the background 

Wooded areas cover a large portion of the park 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.4

• Cultural Resource Areas: The major cultural resource areas include the Patowmack 

Canal and Matildaville. The Canal runs parallel to the Potomac River and extends from 

an area close to the northern parking lot, to the canal cut located approximately at the 

mid-point of the park’s eastern boundary. Matildaville consists of structural remnants of 

buildings that are located to the west of the canal and south of the southern parking lot. 

In addition, there are a number of cultural resources that are scattered across the park 

(see Section 3.2 of this document for more details). 

• Recreational Areas: Recreational uses at the park include overlook areas to view the 

Great Falls, a system of hiking, biking, and horseback riding trails, picnicking, rock 

climbing, whitewater boating, and fishing. The picnic area is a grassy area, with picnic 

tables and grills, that is located adjacent to the entrance road, between the visitor center 

and the lower parking lot. The rock climbing area is located along the Potomac River, 

largely between Overlook 3 and Cow Hoof Rock. Access to the river for whitewater 

rafting and kayaking occurs at Fisherman’s Eddy and AA Gorge, and fishing occurs at 

these locations and many others along the river, as well as along Difficult Run. Kayaking 

and fishing are also available off Sandy Landing further to the south. See Figure 3.1: 

Recreational Opportunities. 

Boundaries and Land Protection

As a part of the current planning effort, the boundaries for Great Falls Park are consistent with 

the area within NPS’s authority that is illustrated in Figure 1.2: Aerial Map. These boundaries 

were identified based on criteria consistent with NPS management policy: to include significant 

or key natural and cultural resources that are central to protecting and fostering public 

understanding of Great Falls Park, a unit of the GWMP; to provide for visitor services and 

interpretation; to protect park resources critical to fulfilling the park's purposes; to address 

operational and management issues; and to protect the unique environments of the Mather 

Gorge of the Potomac River. 

3.1.2 Visitation and Visitor Activities 

Great Falls Park’s visitation was 415,770 in 2005.1

 This is somewhat similar to the visitation in 

previous years (425,290 visitors in 2004; 399,399 in 2003; 430,200 in 2002; 440,852 in 2001; and 

432,937 in 2000). A visitor survey conducted in April/May 1996 identified that the predominant 

visitor uses within the park consist of both passive and active recreational activities.2

 These 

activities, indicated in order of usage per activity, include viewing the Great Falls, 

walking/hiking, viewing wildlife, visiting the Patowmack Canal, picnicking, climbing, bicycling, 

walking pets, nature study, white water boating, jogging, fishing, ranger led walks/talks, and 

horseback riding. 

Of these, the most common activities were identified as viewing the Great Falls (73 percent of 

the respondents), walking/hiking (56 percent), viewing wildlife (41 percent), and visiting the 

Patowmack Canal (31 percent). 

 

1 NPS Public Use Statistics Office (http://www2.nature.nps.gov/mpur/index.cfm) 

2 Great Falls Park, Virginia – Visitor Study. Cooperative Park Studies Unit, University of Idaho. Spring 1996. 
AFFECTED ENVIRONMENT 

3.5 NATIONAL PARK SERVICE 

Developed area of the park 

Portion of the Patowmack Canal
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.6

Opportunities for these activities are achieved at the overlook areas, visitor center, park trails, 

picnic areas, rock climbing areas, and areas where the river can be accessed (see Figure 3.1: 

Recreational Opportunities). 

• Overlook Areas: The most active portion of the Park is located in the vicinity of the 

visitor center and picnic area. There are three overlook areas (Overlook 1 also referred 

to as the Jetty Overlook, Overlook 2 and Overlook 3), located east of the visitor center, 

that allow visitors to view the falls. These three areas are connected by foot trails that 

branch out towards the river from the Patowmack Canal Trail. The park recently 

upgraded the overlook structures and provided ADA compliant accessibility to 

Overlooks 2 and 3.3

 

• Visitor Center: The visitor center consists of two, two-storied structures that are 

connected on the second floor. The building includes approximately 870 square feet of 

offices for the NPS staff (both administrative and interpretive), a 70-seat auditorium, a 

bookstore, a food concession stand, restrooms, and a 2,000-square-foot exhibit area for 

interpretation, and ranger talks. The park offers a variety of interpretive programs for 

visitors including a 10-minute slide presentation on the history of the Great Falls Park, 

ranger talks, and hikes with rangers on various trails within the park and programs for 

children. Due to its age and size, the visitor center is in need of several improvements. 

This includes a reconfiguration of the access ramps to meet ADA standards for slope and 

landing areas, and improvements to the restrooms to meet ADA accessibility standards. 

• Picnic Area: The park offers a picnic area for visitors in an open expanse of land between 

the southern and middle parking areas. This area includes picnic tables and barbeque 

grills. During summer months and warm weekends, the tables are fully utilized. 

• Rock Climbing: There are several stretches of rock faces along the Potomac River and 

Mather Gorge that provide opportunities for rock climbing. Some of the most popular 

are: Dihedrals, Juliet’s Balcony, Seclusion, Matildaville Trail Shortcut, Romeo’s Ladder, 

Aid Box, and Bird’s Nest.4

 These are accessible off the River Trail. The park encourages 

climbers to register at the visitor center or at the lower parking lot; however, no 

equipment or formal programs are offered at the park for visitors interested in this 

activity. Most visitors either bring their own equipment, or come as part of groups 

organized by private businesses that service rock climbing activities. NPS issues a permit 

to these businesses on an annual basis and issued ten such permits in 2006.5

 

• Nature Study: The park offers a significant amount of preserved and largely undisturbed 

open space in a suburban environment. It includes woody vegetation, some of which is 

more than a 100 years old, rare plant and animal species including more than 150 

different varieties of birds. A number of visitors visit the park to appreciate its natural 

environment and participate in activities such as bird watching and nature photography. 

 

3

 Document of Decision and Finding Of No Significant Impact - Improvements To Trails And Overlooks at Great Falls Park, 

Virginia, Great Falls Park, Virginia, 2003. 4

 Brinkworth, Marinda, The Complete Great Falls Climbing Guide, Dog Days Graphics, Maryland, 1998.

5 Incidental Business Permits 2006, GWMP, dated November 16, 2006.
AFFECTED ENVIRONMENT 

3.7 NATIONAL PARK SERVICE 

Data Source: NPS, 2002 

Figure 3.1: Recreational Opportunities 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.8

• Trails: There are eleven trails within Great Falls Park. These vary by use, length, and the 

experience that they offer. The trails closest to the visitor center and parking areas 

experience the most usage as a large number of visitors tend to remain in this portion of 

the park. Usage is significantly reduced along trails that extend further away from the 

developed area of the park. The system of trails within the park are illustrated on Figure 

3.2: Existing Trails, and consist of the following: 

o The Old Carriage Road Trail is a multipurpose trail that runs for approximately 

1.6 miles in the north-south direction. The trail connects from the northern end 

of the park to Georgetown Pike in an area to the north of Difficult Run. The trail 

is for walkers, joggers, hikers, bicyclists, and horseback riders. 

o The Patowmack Canal Trail is another north-south trail that runs parallel to the 

Patowmack Canal for approximately 1.25 miles. The Patowmack Trail connects 

to the upper parking lot to the north, and River Trail to the south. The trail is a 

single-purpose trail restricted to foot traffic. It is one of the most heavily used 

trails, as it connects the parking areas to the overlooks and the picnic area. 

 

o The River Trail also runs in the north-south direction, parallel to the Potomac 

River for approximately 1.5 miles. The trail connects to the Patowmack Canal 

Trail to the north, in the vicinity of the picnic area, and the Ridge Trail to the 

south. The trail is a single-purpose trail that is restricted to walkers, joggers, and 

hikers. It offers views of the Potomac River, including the Mather Gorge. The 

trail is heavily used by visitors seeking to walk along the river, as well as to access 

climbing areas. 

o The Matildaville Trail runs for approximately 1.1 miles in the north-south 

direction. It connects to the Old Carriage Road Trail to the north, in the vicinity 

of the restrooms near the lower parking lot, and to the Ridge Trail to the south. 

The trail is open to horseback riders, walkers, joggers, and hikers. 

o The Ridge Trail is approximately 1.5 miles long and runs in the east-west 

direction. It is a multipurpose trail that originates to the west at Old Dominion 

Drive and terminates at the Difficult Run Trail to the southeast. The trail is for 

hikers, walkers, joggers, bicyclists, and horseback riders. 

o The Swamp Trail is approximately 0.4 miles long. It connects to the Old Carriage 

Road Trail to the north, and the Swamp-Ridge Connector Trail to the south. The 

trail is a single-purpose trail, restricted to foot traffic. 

o The Swamp-Ridge Connector Trail is approximately 0.4 miles long and connects 

Swamp Trail to the north and Ridge Trail to the south. Similar to Swamp Trail, 

the Swamp-Ridge Connector Trail is a single-purpose trail, restricted to foot 

traffic. 

o Riverbend Road Trail is approximately 0.4 miles long that runs in the east-west 

direction and connects Riverbend Road to the Fire Road. The trail is restricted 

to foot traffic and horseback riders. 
AFFECTED ENVIRONMENT 

3.9 NATIONAL PARK SERVICE 

Data Source: NPS, 2002 

Figure 3.2 : Existing Trails 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.10

o The Difficult Run Trail is approximately 0.7 miles long and runs in the east-west 

direction adjacent to Difficult Run, between Georgetown Pike and the Potomac 

River. It is a multipurpose trail for hikers, walkers, joggers, bicyclists, and 

horseback riders. 

o Mine Run Trail is approximately 0.5 miles long and runs in the north-south 

direction. The trail branches off from the Fire Road and loops around Clay 

Pond. It is restricted to foot traffic and horseback riders. 

 

o North River Trail is approximately 0.25 miles long and run in the north-south 

direction between the northern parking lot and Riverbend Park. The trail is a 

single-purpose trail, restricted to foot traffic. 

 

o The Fire Road is approximately 0.4 miles long and runs in the north-south 

direction. It connects the northern parking lot and Riverbend Park. It is a 

multipurpose trail for hikers, walkers, joggers, bicyclists and horseback riders. 

• Surrounding Trails: The Great Falls Park is a primary node in a growing network of 

existing and proposed trails. On the north, a trail in the park connects with a trail in 

Riverbend Park, managed by the Fairfax County Park Authority (FCPA). On the 

southwest side of the park, the multi-purpose Difficult Run Trail, also managed by 

FCPA, extends upstream from the Park, and is part of the 40-mile Fairfax CCT which 

connects to Pohick Stream Valley Trail in the southern part of the County. In the 

northwest-southeast direction, the park will serve as a trailhead for a planned segment of 

the PHNST along Georgetown Pike, currently under study by Fairfax County. Along 

with trails in Great Falls Park and Riverbend Park and the 10-mile Potomac Heritage 

Trail and 17-mile Mount Vernon Trail in GWMP (south of I-495), PHNST would 

potentially include a 116-mile trail system between Prince William Forest Park in 

southern Prince William County and White’s Ferry in Loudoun County, connecting with 

the C & O Canal Towpath in Georgetown and at White’s Ferry. Trails within the park, 

where the geology transitions between the Atlantic Coastal Plain and the Piedmont, are 

some of the most prominent features in the 425-mile PHNST corridor between the 

mouth of the Potomac River and the Allegheny Highlands. 6

 

• Whitewater Boating and Kayaking: Visitors can gain access to the Potomac River from 

Great Falls Park for whitewater rafting and kayaking. The park does not offer any 

equipment or formal programs for visitors interested in this activity. Most visitors either 

bring their own equipment, or come as part of groups organized by a number of private 

businesses that service non-motorized boating activities. NPS issues a permit to these 

businesses on an annual basis and issued three such permits in 2006. Access to the river 

is gained off Fisherman’s Eddy, located between Overlooks 2 and 3, and AA Gorge area. 

In addition, access to the river can be achieved from Sandy Landing. 

 

6

 Implementation Plan for the Potomac Heritage National Scenic Trail in Fairfax County, Prepared by the Northern Virginia 

Regional Commission, September 2002.
AFFECTED ENVIRONMENT 

3.11 NATIONAL PARK SERVICE 

Patowmack Canal Trail 

Kayaking in the Potomac River 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.12

• Fishing: The park provides access to the Potomac River for recreational fishing. A 

Virginia or Maryland fishing license is required for those over the age of 16 years. Access 

to the river is from Fisherman’s Eddy, located between Overlooks 2 and 3, and other 

locations in the park such as near the Aqueduct Dam and AA Gorge. 

Visitor Safety

Each year the park is the scene of accidents involving visitors engaged in a variety of activities. 

While most of these accidents are minor, sometimes these result in serious injuries, including 

fatalities. Accident records indicate that most victims are visitors engaged in passive recreational 

activities who had come to picnic, view the falls and fish, rather than visitors engaged in active 

recreational activities such as kayaking or climbing. Incidents such as getting too close to the 

edge of the cliffs, fishing near swift water, deciding to wade, or trying to scramble on some of the 

steep slopes, have resulted in the most serious injuries, as well as fatalities, in recent years. 

Accident locations have varied greatly from year-to-year. Typically, the park may experience 

two to five years of low incident and accident rates followed by several years of increased 

incidents/accidents. In 2004, there were a total of 99 emergency medical incidents. Of these, six 

required advanced life-support treatment. There were also three fatalities in 2004 (two of these 

were the result of people scrambling on a steep area over the river). While the fatality rate was 

higher than in the past several years, the number of medical incidents was not significantly 

different (when one considers the improved reporting that was used in 2004). 

3.1.3 Community Facilities - Police, Fire, and Rescue Services 

The park is served by the USPP. The USPP uses a trailer for their offices, and leases space in a 

nearby stable (outside the park) for keeping its horses. In addition to the personnel at the park, 

USPP support from regional USPP facilities is provided when necessary. This includes 

helicopter support to access remote areas of the park. 

Fairfax County also provides fire and rescue services to the park. There are four fire stations 

within a five-mile radius of the park: Company 12 on Georgetown Pike northwest of the park; 

Company 29 on Leesburg Pike south of the park; Company 1 near Dolley Madison Boulevard, 

southeast of the park; and, Company 39 on Leesburg Pike, northwest of the park. Of the four 

stations, Company 12 usually provides the first response to any emergency at the park. 

3.1.4 Neighboring Population and Socio-Economic Conditions 

The 2000 U.S. Census provides the basis for analyzing the demographic composition of the area 

around the park. Population, household, and income data from the Census provide useful 

demographic information. Executive Order (EO) 12898 requires federal agencies to: 

1) identify any disproportionately high and adverse effects on human health or human 

environment of minority and/or low-income populations resulting from federal programs, 

policies, and activities, and 2) identify alternatives that may mitigate these impacts. 

Characterization of a group of persons as a potentially “affected community” under EO 12898 

requires the fulfillment of one of the three following criteria: a minority population of the 

affected area that exceeds 50 percent; a low-income population based on the Bureau of Census 
AFFECTED ENVIRONMENT 

3.13 NATIONAL PARK SERVICE 

Current Population reports; or a minority population meaningfully greater than the minority 

population percentage in the general population, or other appropriate geographic units. 

Demographic data was collected and analyzed to determine the existing socio-economic 

conditions in the Great Falls Park study area. The potential impacts that may result from future 

activities at the park are localized; therefore, the potentially affected area can be defined 

narrowly. For this project, the study area was defined to include four adjacent census tracts in 

Fairfax County, Virginia and three adjacent census tracts in Montgomery County, Maryland.7

 

Additional data for Fairfax and Montgomery Counties was also collected and analyzed in order 

to draw a comparison between the study area and the larger geographical area. 

Population

Based on data from the 2000 Census, the population of the study area is 43,401 (25,898 persons 

in Fairfax County and 17,503 in Montgomery County). This figure represents approximately 

2.36 percent of the total population of Fairfax and Montgomery Counties (1,843,090 persons). 

The racial composition of the study area is less diverse than the greater geographic area (see 

Table 3.1: Population Characteristics in the Surrounding Area). 

Table 3.1: Population Characteristics in the Surrounding Area

 Total 

Population 

Declared 

One Race 

(%) 

White (%) Asian (%) 

Black/ 

African 

American 

(%) 

Others 

Declared 

One Race 

(%) 

Declared 

More than 

One Race 

(%) 

Fairfax 

County 969,749 934,311 (96) 677,904 

(70) 126,038 (13) 83,098 (9) 47,271 (5) 35,438 (4) 

Fairfax 

County 

Portion of 

Study Area 

25,898 25,173 (97) 21,286 (82) 2,534 (10) 876 (3) 477 (2) 725 (3) 

Montgomery 

County 873,341 843,224 

(97) 565,719 (65) 98,651 (11) 132,256 (15) 46,598 (5) 30,117 (3) 

Montgomery 

County 

Portion of 

Study Area 

17,503 17,155 (98) 13,691 (78) 2,755 (16) 560 (3) 149 (1) 348 (2) 

Note: Percentage is based on Total Population. 

Source: US Census 2000 

Census 2000 data also indicates that the median age in the study area is slightly higher compared 

to the two Counties. The median age in the Fairfax County portion of the study area was 40.4, 

compared to 35.9 in Fairfax County. Similarly, in the Montgomery County portion of the study 

area, the median age was 42.3, compared to 36.8 in Montgomery County. The Metropolitan 

Washington Council of Government anticipates population in Fairfax County to grow by 

approximately 234,000 persons between 2000 and 2025 (an approximate increase of 24.1 

percent), and in Montgomery County to grow by approximately 165,000 persons (an 

approximate increase of 19.3 percent) for the same period.8

 

7

 Tracts 4801, 4804, 4819 and 4803, in Fairfax County, and Tracts 7006.08, 7060.07 and 7060.08 in Montgomery County. 8

Metropolitan Washington Council of Government’s Round 6.2, intermediate series, Summer of 2000.
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.14

Housing

The Fairfax County portion of the study area contains 8,807 housing units, representing 2.5 

percent of all housing units in Fairfax County. The vacancy rate of 2.4 percent in this area is 

comparable to the County. The owner occupancy rate of 87.4 percent in the Fairfax County 

portion of the study area is significantly greater than the occupancy rate of 70.9 percent for 

Fairfax County. 

The Montgomery County portion of the study area contains 5,578 housing units, representing 1.7 

percent of all housing units in the County. The vacancy rate of 2.7 percent in this area is slightly 

less compared to the County (3.0 percent). The owner occupancy rate of 92.2 percent in the 

Montgomery County portion of the study area is much greater than the occupancy rate of 68.7 

percent for Montgomery County. 

The median value of owner-occupied housing in the Fairfax County portion of the study area 

varied between $418,100 and $755,600 in different Census Tracts (Census 2000). These are 

substantially higher than Fairfax County, where the median value of owner-occupied housing 

was $233,300. With regards to rental housing, the median rent in the Fairfax County portion of 

the study area is substantially higher compared to Fairfax County overall. 

The median value of owner-occupied housing in the Montgomery County portion of the study 

area varied between $488,200 and $787,200 in different Census Tracts (Census 2000). These are 

substantially higher than Montgomery County, where the median value of owner-occupied 

housing was $210,600. With regards to rental housing, the median contract rent in the three 

Census Tracts within Montgomery County is greater than $2,000 per month. These rents are 

significantly higher than the median contract rent of $856 for the County. 

Income Levels

The median household income in 1999 in three of the Census Tracts in Fairfax County portion 

of the study area varies between $156,614 and $167,568. These are approximately 1.9 to 2.1 times 

the median household income of $81,050 for Fairfax County. The median household income in 

Census Tract 4819 in 1999 was $76,261, approximately 94 percent of the County’s median 

household income. 

 

The median household income in 1999 for the three Census Tracts in Montgomery County is 

greater than $155,373. By comparison, the median household income in 1999 in Montgomery 

County was $71,551. 
AFFECTED ENVIRONMENT 

3.15 NATIONAL PARK SERVICE 

3.2 CULTURAL RESOURCES 

 

NPS Management Policies (2006) prescribe that the NPS “will protect, preserve, and foster 

appreciation of the cultural resources in its custody and demonstrate its respect for the peoples 

traditionally associated with those resources through appropriate programs of research, 

planning, and stewardship.” 

 

3.2.1 Summary of Great Falls Park History 

Pre-historic Context

American Indians once occupied various areas in the greater metropolitan Washington DC area. 

The lands along the Potomac and Anacostia Rivers, and the many tributaries that ran through 

the Washington DC, area offered game animals and fish, a variety of plant foods, and lithic 

resources. Locations along streams were often selected by American Indians for camp or village 

sites and for the exploitation of food resources. 

Prior to the existence of the Patowmack Canal, American Indians occupied areas now within the 

park. They engaged in fishing in the Potomac River and obtained other sustenance from the 

surrounding forest. While the boundaries of the Patowmack Canal can be documented as 

occupying the low-lying land adjacent to the Potomac River, the activity zones of these prehistoric peoples are not so clearly defined. A 1969 archeological report documenting aboriginal 

occupation within Great Falls indicates the existence of seasonally occupied campsites and a 

trade network.9

 

Historic Context

The Patowmack Canal at Great Falls Park was built between 1786 and 1802 to establish a 

navigable route around the Great Falls on the Potomac River. The attempt to provide a 

transportation link to the Ohio River Valley began with the formation of the Ohio Company in 

1749. George Washington, his brothers Lawrence and Augustus, and other prominent families 

were among the company’s many stockholders. The company developed an overland route 

westward through the Potomac River basin, establishing numerous settlements along the way. 

However, financial losses during the French and Indian War (1756-1763) resulted in the 

company’s demise. No canals were built and the Revolutionary War soon followed. 

After the Revolutionary War, George Washington embarked on an extensive inspection of 

western lands to speculate on possible water routes to the Ohio Valley. In 1785, a charter was 

obtained to establish the Patowmack Company that was delegated the responsibility of 

constructing canals and roads from the eastern waters leading toward Lake Erie. Construction 

of the Patowmack Canal commenced in 1785 and was completed in 1802. The canal functioned 

until 1828, at which time the C&O Canal was completed on the Maryland side of the Potomac 

River. Subsequent to the opening of the C&O Canal, the Patowmack Canal locks were 

dismantled and abandoned. 

 

9

 Gardner, William M., Stephen J. Gluckman, Ellis E. McDowell, and Charles W. McNett, Jr., A Report of Excavations at the 

Stout Site. Quarterly Bulletin of the Archaeological Society of Virginia 24(1):133-143, 1969. 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.16

Matildaville

In 1790, an act of the Virginia state legislature provided for a town of 40 acres to be established 

adjacent to the canal.10 The act specified that the town be laid out in one-half acre lots. The lots 

were sold at auction under the provision that the purchaser erect “a dwelling house, 16 feet 

square with a brick or stone chimney,” to be finished and fit for habitation within five years of 

the date of sale. Over 80 plots were available, however, not a large number of them were sold 

during auctions held between 1795 and 1797. 

At the height of development, Matildaville, as the town was called, consisted of a number of 

dwellings, a springhouse, a forge, a gristmill, a sawmill, several warehouses, an inn, and a handful 

of company buildings. Although some of the structures in the town continued to be occupied 

throughout the 19th century, the official recognition of Matildaville ceased in 1839 when an act 

was passed to incorporate another town, South Lowell, at the same location. 

Mid-1800s to Mid-1900s

The majority of land currently comprising Great Falls Park was purchased in 1854 by the Great 

Falls Manufacturing Company. In 1895 the Great Falls Power Company purchased the rights to 

the land. The Power Company expanded its ownership to 900 acres. In the early part of the 20th

Century, a portion of the land was leased for a resort that included a carousel and lookout 

tower. Between 1906 and 1934, the Great Falls and Old Dominion Railroad provided a 14-mile 

public trolley line along Old Dominion Drive that originated in Georgetown, Washington, DC. 

In the 1920’s, a religious retreat, Camp Clark, provided water sports and overnight stays, and was 

operated above Sandy Landing, below the exit of the lowest lock of the Canal. 

National Park Service Acquisition

A brief change in title occurred in August of 1947 when the Washington Railway and Electric 

Company took control. A week later, the Potomac Electric Power Company (PEPCO) became 

the titleholder of the property. In 1953, the Fairfax County Park Authority purchased 16 acres 

adjacent to the Falls. In 1960, an agreement was reached between the U.S. Government and 

PEPCO, whereby PEPCO leased 790 acres of land in Great Falls, Virginia to the National Capital 

Parks. In return, the U.S. Government leased 390 acres of land in Prince George’s County, 

Maryland (known as the Blue Ponds Property) to PEPCO. In 1965, the U.S. House and Senate 

passed enabling legislation that authorized the NPS to swap the Blue Ponds property and “not 

more than one million dollars” for the Great Falls property. 

3.2.2 Archaeological Resources 

The museum collection for Great Falls Park consists of over 76,000 artifacts primarily associated 

with American Indian prehistory and the Patowmack Canal-era history of the park. A large 

percentage of the objects were collected and documented during archaeological excavations. 

Several sites that have been investigated include the Patowmack Canal (limited testing), Stout 

 

10

 Barnes, Arthur G., History of Potomac Canal: Matildaville, Southside Historical Sites, Inc., College of William and Mary, 

Williamsburg, Virginia, March 1978.
AFFECTED ENVIRONMENT 

3.17 NATIONAL PARK SERVICE 

site, William Dickey House, “Ruins of Old Jail”, Springhouse, Samuel Briggs Grist Mill, Potts 

and Wilson Iron Forge/Foundry.11

Recent archeological investigations unearthed additional evidence of past human activities in 

Great Falls Park.12 Two sites of refuse disposal dating from early to mid-twentieth century were 

identified during an excavation to locate a cell tower. Preliminary analysis of other recovered 

artifacts indicated that an early to mid-19th century domestic site existed near the area of impact. 

In addition to the resources that have been revealed, the park has the potential to contain 

additional archaeological resources. These could be associated with the Patowmack Canal (its 

construction, use and abandonment), Matildaville, the trolley line, Camp Clark, and other 

prehistoric Native American Indian and historic period sites and structures that have existed 

within the park. 

Petroglyph Site

The park contains a petroglyph site that was discovered in the 1980s and is believed to be 

attributable to pre-historic American Indians. The petroglyph (a carving or inscription on a 

rock) depicts four stick figures in a possible atlatl spear throwing sequence. An atlatl is a device 

like a hooked stick and is used to help propel a spear or dart with greater force. The exact age 

and nature of the petroglyphs are unknown. 

3.2.3 Historic Resources 

 

Patowmack Canal Section at the Park

The Great Falls Park section of the Patowmack Canal is a designated National Historic Civil 

Engineering Landmark, as well as a National Historic Landmark for being one of the earliest 

canals in the history of the U.S. and an engineering accomplishment of its time. In addition, the 

canal is an “extraordinary manifestation of certain leaders of the early American republic, 

notably George Washington and James Madison”. 13 The Patowmack Canal included a series of 

five skirting canals around falls areas on the Potomac River spaced from Georgetown to Harpers 

Ferry, and approximately 5,400 feet of the Great Falls skirting canal is located in the park. 

Principal elements of the canal system that survive in various degrees of preservation within the 

park include a large wing dam above the Great Falls, upper and lower guard gates linking a 

relatively long channel that includes a large Holding Basin, and a series of five locks running 

from below the Lower Guard Gate to the Potomac River below the falls.14 NPS’s List of 

Classified Structures (LCS) identifies properties that are either listed or eligible for listing on the 

National Register of Historic Places based on their historical, architectural or engineering 

significance (see Table 3.2, which identifies structures in the park that are on the NPS’s LCS).15

 

11

 Little, Barbara J., National Capital Area Archaeological Overview and Survey Plan, U.S. Department of Interior, NPS-NCR, 

1995. 12

 Environmental Assessment, Bell Atlantic Mobile Application for Wireless Telecommunication Facility, Ridge Trail Site, Great 

Falls Park, Virginia. 2001. 13 National Register of Historic Places Inventory – Nomination Form, National Park Service, 1984. 14

 Ibid. 15

 Documentation and Stabilization of Various Masonry Features – Condition Assessment Report, Patowmack Canal, Great 

Falls Park, GWMP. Prepared by the Historic Preservation Training Center, NPS, 1998.
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.18

Table 3.2: List of Classified Structures within Great Falls Park 

Feature Description 

 

Canal Inlet and Wing Dam Wing Dam extended into the Potomac River to channel water into the canal. The canal inlet 

and dam still allow water into the canal, although most of the dam has washed away. The 

remnants of the inlet and dam are still visible during low water. 

Upper Spillway Located on the river side, next to the upper guard gate, it functioned as a stone dam that 

allowed excess water to overflow and return to the river. It continues to divert water to the 

river. 

Upper Guard Gate/Bull Nose This includes the stone-lined portion of canal between upper spillway and upper guard dam. 

The guard gate functioned to protect the rest of the canal from excessive water. No remains 

exist of the gate. The canal walls and bull nose at the guard gate were recently stabilized. 

Lower Spillway, Dam, and 

Waste Weir 

The canal splits at the southeast end of the middle canal, and is in a state of ruin. The dam is in 

poor condition. 

Mill Site The mill site, known as Brigg’s Mill, is located on the upstream portion of the lower canal. The 

mill was powered by water from the canal to produce flour for Matildaville. 

Collecting Basin or Upper 

Holding Basin including the 

West Wall, East Wall, and 

Control Gate 

A basin area of approximately two acres was used to dock, hold, and turn boats, and to store 

water for the canal locks. The basin is mostly filled in and the perimeter is used as part of the 

park’s trail system. It now consists of low vegetation and large shade trees. The walls of the 

basin still exist, as do the remnants of the control gates. 

Forge Foundry Site The foundry site, known as Pott’s Forge, is located adjacent to the access trail to Fisherman’s 

Eddy. Footings and foundation of the foundry remain. These are overgrown with vegetation 

and are barely visible. There are also some remains of stone foundation walls adjacent to the 

foundry. These may be from the railroad/amusement park period, or from the canal operation 

period. 

Waste Weir / Spillway The weir/spillway is located at the southeast end of the holding basin. It functioned to regulate 

water depth and allowed for drainage of the entire canal. Adjacent to the weir, there are 

remains of two rectangular foundation walls that may have been a lumber mill. Portions of the 

building footprint and dry laid stone walls were recently stabilized by the park. 

Lower Guard Gate and Walls The lower guard gate, also identified as the head gate, is located at the southeastern end of the 

upper holding basin. The walls adjacent to the gate, along with flat strap iron clamps in the 

stone walls, still remain. The channel leading to the gate is filled with soil and grass. 

Lock Number 1 including canal 

walls between the Locks 1 and 2 

Lock number 1 is 14 feet wide by 100 feet long. The walls are made of ashlar-dressed, red 

Seneca sandstone with rubble interiors. (Two pairs of wood-swing mitre-type gates, with 

sliding wicket gates that controlled the flow of water, still exist and are on display in the Visitor 

Center.) 

Lock Number 2 Lock number 2 is 12 feet wide by 88 feet long. Wood-swing, mitre-type gates with butterfly 

wicket gates controlled the flow of water. Part of the wall has collapsed and part is covered 

with vegetation. 

Locks Number 3, 4 and 5 The three locks form a step-like system and share gates. Lock 3 cuts into the riverside wall and 

creates a small holding area. It also bends slightly towards locks 4 and 5. The locks were 

severely damaged during the 1996 floods and have since been stabilized. 

Upper Guard Gate Dam The dam consists of a stone dam and earthern berm that runs perpendicular to the canal. 

False Canal This feature is located 600 feet upstream from the Wing Dam. It is approximately 1,200 feet 

long and 30 feet wide and may have functioned as a mooring place for boats entering the canal. 

This area is in a state of ruin and is filled with water due to debris that has dammed up either 

end of this feature. 
AFFECTED ENVIRONMENT 

3.19 NATIONAL PARK SERVICE 

Feature Description 

 

Upper Canal Walls and Bed The upper portion of the canal, between the inlet area and the upper spillway is approximately 

800 feet long and 20 feet wide. It consists of earthern walls. This portion of the canal is filled 

with water and is silted. There are three stone spring houses, concrete culverts, and chimney 

remains in the vicinity of this portion of the canal. 

Middle Canal The middle portion of the canal, from the upper guard gate to lower spillway, is 300 feet long 

and 30 feet wide. The walls are constructed of dry-laid stone with slight batter. The walls are 

20 feet thick and 10 feet high, above the canal bed. The stone walls are still present, although 

overgrown vegetation is causing deterioration of the stonework. The canal bed is also visible. 

At the southeast end of this portion of the canal, a lot of silting has occurred near the lower 

spillway dam. 

Lower Canal The lower portion of the canal consists of the portion between the lower spillway to the upper 

holding basin. The canal in this stretch is 1,200 feet long and 20 feet wide. Most of this portion 

of the canal is filled in with soil and only the top of the canal walls are visible in many locations. 

D.A.R. Bronze Plaque This plaque is in memory of George Washington of Fairfax County, Virginia. As president of 

the Patowmack Company, he was responsible for the construction of the canal. 

Double AA Canal Route A 12 feet wide feature, located adjacent to the lower guard gate and similar in appearance, 

probably functioned as a spillway for the alternative canal route to the river. This feature is in 

poor condition and overgrown with vegetation. The alternate canal route ties into the natural 

ravine to the river. Boats in this stretch may have been pulled with ropes rather than moved 

through a system of locks. Stone retaining walls are visible at the downstream end of the upper 

holding basin, south and east of the waste weir. The exact route and function of this canal is 

unknown. This feature is in poor condition and overgrown with vegetation. 

Lower Holding Basins (2nd and 

3rd, between Locks 1 and 2 and 

Locks 2 and 3 along AA route) 

The second holding basin, located between Locks 1 and 2, along the AA route, fed water into 

locks and functioned as a holding area for boats. The crumbled walls of the second basin are 

still visible, although these are in a state of ruin and overgrown with vegetation. The third 

holding basin, located between Locks 2 and 3, along the AA route, fed water into the canal at 

Lock 3. The area between the holding basin and Lock 3 was substantially damaged during the 

1996 flood. 

Higg’s Hole This feature is a diamond-shaped hole, 15 feet across, and cut into solid rock. The function of 

this feature is unknown. 

National Historic Civil 

Engineering Landmark Plaque 

The plaque recognizes the engineering feat of constructing the canal and George Washington’s 

role in its construction. 

Jetty The jetty is cut into rock at the base of Lock 5. It was built to protect the end of the canal and 

to facilitate the entry and exit of boats. This feature has been damaged by flood action and is 

barely visible. 

Matildaville Landscape The Matildaville landscape includes several ruins, of which the following three are identified 

in the LCS16: Dicky’s Inn (Pile of rubble and chimney remains that are surrounded by rusted 

scaffolding); Canal Superintendent’s House (Foundation walls and corner stones remain 

visible); and Spring House (Stone foundation walls and stairs remain with a spring, which is 

rarely visible, but that continues to run through it). 

 

16

 An archaeological survey carried out in 1978 that located 31 structures and features in the area thought to be Matildaville. 

Source: Barka, Norman F. and Charles G. Troup. Southside Historical Sites, Inc. College of William and Mary, Williamsburg, 

Virginia, March 1978. 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.20

Other Historic Resources within the Park

There are several other resources that have been identified as culturally important within the 

park.17 However, additional research is needed to understand their archaeological or historic 

significance. The resources include old road traces, domestic sites, American Indian sites, 

railroad and industrial sites, and remains of the old amusement park site. Examples include the 

Hubble Farmstead, the Native American Indian Stout Site (prehistoric), Carousal Site, and 

Quarry Site. Some old road traces continue to function as trails (e.g. Old Carriage Road Trail 

and Ridge Road), while others are no longer in use. These cultural resources also contribute to 

the park’s history and are illustrated (without identification to prevent potential damage) on 

Figure 3.3: Cultural Resources. 

Historic Resources in the Vicinity of the Park

Other historical sites in the immediate vicinity of Great Falls Park which have been listed on the 

National Register of Historic Places include the C&O Canal NHP, located directly across the 

Potomac River, Cornwell Farm, just west of the park on Georgetown Pike, and Colvin Run Mill, 

approximately 2 miles to the west. 

The C&O Canal NHP includes over 50 features on the LCS. As such, they are mandated for 

preservation through the park’s enabling legislation (Public Law 91-664—Chesapeake and Ohio 

Canal Development Act). 

Among the features listed are: several miles of the C&O Canal; the canal towpath and six locks 

(numbers 15-20); the Great Falls Tavern, located above the Great Falls at Lock 20 of the Canal; 

Mary’s Wall (according to the Dry Stone Wall Conservancy "...one of, if not the tallest canalcarrying retaining walls in the world."); Old Anglers Inn adjacent to the C&O Canal; and the 

Civil War-era gold mines. As a result, the C&O Canal General Plan for this area has been 

designated as Zone A, a National Interpretive Center Zone, which must have a superior 

significant cultural landscape. The Great Falls Maryland Zone A area (4.2 miles in length) is thus 

described because of the integrity of the historic canal operations and natural setting. Since the 

beginning of the twentieth century, preservation in the Great Falls area has been interpreted to 

mean preservation not only of material structures but also of the cultural ambiance of the 

landscape of the area. 

Cornwell Farm is a residential structure that is important for its Georgian Architecture. It was 

constructed in the early 1800s and is privately owned. Colvin Run Mill is a 19th century water 

powered gristmill that is still operational. The property is managed by the Fairfax County Park 

Authority. 

Georgetown Pike runs parallel to the southwestern boundary of the park and was designated as 

the Commonwealth’s first Virginia Byway in 1974. In 1993, the Virginia Department of Historic 

Resources determined that Georgetown Pike appears to meet the criteria for listing in the 

Virginia Landmarks Register as well as the National Register of Historic Places. Historical 

documentation (de la Camp 1866) indicates the Ridge Trail was at one time the original road 

trace for the Old Georgetown and Leesburg Road, the predecessor to Georgetown Pike. 

 

17 List compiled by Historian Jim Putman, Cultural Resource Preservation Team, GWMP, 1990. 
AFFECTED ENVIRONMENT 

3.21 NATIONAL PARK SERVICE 

Data Source: NPS, 2002 

Figure 3.3: Cultural Resources 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.22

There are also several historic properties within two miles of the park that are listed on 

Virginia’s Landmark Register and Fairfax County Inventory of Historic Sites. These are 

identified in the following table: 

 

Table 3.3: Historic Properties within Approximately two miles of Great Falls Park that are Listed on the 

Virginia Landmark Register (VLR) or Fairfax County Inventory of Historic Sites (IHS)18

 

Resource 

 

Listed On Resource Listed On 

Bethel Primitive Baptist Church Fairfax County IHS Four Stairs VLR, Fairfax County IHS 

Bull Neck Gold Mine Fairfax County IHS Great Falls Grange VLR, Fairfax County IHS 

Coleman (George C.) House Fairfax County IHS Great Falls Post Office (old School 

House) 

Fairfax County IHS 

Colvin Run Community Center Fairfax County IHS Greek Revival House Fairfax County IHS 

Colvin Run Mill Fairfax County IHS Gunnell’s Run Fairfax County IHS 

Colvin Run Miller’s House Fairfax County IHS Jackson (Verlinda) House Fairfax County IHS 

Cornwell (Henry) House Fairfax County IHS Kalorama Springs (Site) Fairfax County IHS 

Cornwell Farm Fairfax County IHS King Subdivision Fairfax County IHS 

Eastern Shore House Fairfax County IHS Leigh (Dr. Alfred) House Fairfax County IHS 

Feighery Store and House, 

(Thelma’s Ice Cream) 

Fairfax County IHS Towlston Grange Fairfax County IHS 

Follin (J.N.) House Fairfax County IHS 

Forestville Colored School VLR, Fairfax County IHS 

Turner (Mark) Dairy Farm Fairfax County IHS 

3.2.4 Viewsheds 

This section describes several noteworthy viewsheds, both within, and outside the park, that 

could be affected by any changes in the park. 

Views within the Park

The view of Great Falls is one of the most important resources in the park. A large number of 

visitors come to the park to see this view. Three overlooks provide a formal area for viewing. In 

addition, the falls can be seen from portions of the Patowmack Canal Trail. Also important are 

views of the river and the Potomac Gorge that are available at various locations along the River 

Trail. While there are no formalized viewing areas south of the three overlooks, there are several 

natural areas, including the Cow Hoof Rock and the Mather Plaque location, where visitors 

experience views of the river and gorge. 

Another important view is the entrance into the park. After going past the entrance station, one 

of the first views offered to a visitor is that of the maintenance facility and the wooden fence that 

surrounds it. The facility and fence are unattractive and often the southern gate is open and 

reveals the storage area adjacent to the maintenance facility to visitors. 

 

 

 

 

 

 

 

18

 Sources: Virginia Department of Historic Resources website (http://www.dhr.virginia.gov/registers/register.htm); Email 

communication with Fairfax County Department of Planning and Zoning dated 02/15/2005. 
AFFECTED ENVIRONMENT 

3.23 NATIONAL PARK SERVICE 

View of the Potomac River and Gorge from Cow Hoof Rock 

Park entrance with a view of the Maintenance facility 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.24

Views from Surrounding Areas 

 

Views from C & O Canal NHP 

Great Falls Park, Virginia contributes to the visual quality of the C&O Canal NHP. The 

McMillan Commission, created to study and recommend improvements to Washington’s park 

system, and included among its members the noted landscape architect Frederick Law Olmsted, 

Jr., wrote in 1901: 

“...the surroundings of the Great Falls on both sides of the river should, in our opinion, be 

converted into a national park... No buildings should be allowed between the drives and the 

river, and no change should come to pass in the character of the canal that will tend to 

transform its primitive character and quaint beauty. The canal has a charm of its own, as, half 

disclosed and half revealed, it winds among the trees; and not the least part of this charm, so 

desirable to be preserved, is the slow, old-fashioned movement of the boats and the people 

on and near this ancient waterway [emphasis added].”19

Visitors within the C&O Canal NHP, along the Billy Goat Trail, adjacent to the Potomac, along 

the outlooks and observations decks, or along Mary’s Wall, are offered a view of Great Falls 

Park’s natural character on the opposite banks of the river. Any changes within the park have 

the potential to impact these sensitive viewsheds from C&O Canal NHP. 

Views along Georgetown Pike 

Georgetown Pike is a designated Virginia Byway. According to the Virginia Department of 

Transportation, such designation is ascribed to road corridors that contain aesthetic or cultural 

values near areas of historical, natural, or recreational significance. The park shares a major 

portion of its southwestern border with Georgetown Pike. In this portion, the road is primarily 

wooded on either side. Any changes within this portion of the park would have the potential to 

affect views from the road. 

 

19

 Environmental Assessment, Bell Atlantic Mobile Application for Wireless Telecommunication Facility, Ridge Trail Site, Great 

Falls Park, Virginia. 2001.
AFFECTED ENVIRONMENT 

3.25 NATIONAL PARK SERVICE 

3.3 NATURAL RESOURCES 

3.3.1 Geophysical Resources 

Geology

The NPS Management Policies (2006) prescribe that NPS “will preserve and protect geologic 

resources as integral components of park natural systems,” and would “allow natural geologic 

processes to proceed unimpeded.” 

The park is within the Piedmont physiographic province, resting upon igneous and 

metamorphic rock, formed during a history of complex geological activities. The geologic 

materials of the park began as clay, silt, and sand deposited in a sea over 440 million years ago. 

The sediments underwent intrusion by magma, metamorphosis, and folding during the course 

of tectonic events resulting in mountain building in North America. Eventual tilting of the 

Potomac region toward the east resulted in streams cutting through Piedmont materials from 

the west and the deposition of sediment in what would become the Coastal Plain province.20

Over the past approximately 100,000 years, the Potomac River has continued to erode through 

the Piedmont and deposit sediment in the Coastal Plain. The promontories at the park, and the 

adjacent water falls in the Potomac, are the result of differential erosion by the Potomac on 

resistant Piedmont rocks and softer sedimentary Coastal Plain materials over thousands of 

years. 

Within Great Falls Park, geologic mapping published by the United States Geological Survey 

(USGS) identifies and locates common groups of formations. The geology of the park consists 

of: surficial boulders deposited on Glade Hill; surficial deposits of alluvium, colluvium, and fill 

from construction in lower drainage areas; metamorphosed sedimentary rocks of the Mather 

Gorge Formation on the rolling hills between Glade Hill terrace and lower areas; and igneous 

rocks along the Gorge at the southeastern portion of the park.

Topography

Six terrace levels, resulting from erosion at various past Potomac River elevations, are evident in 

the Potomac Gorge area. The two upper-most elevation terraces are exhibited in Great Falls 

Park. The highest terrace is at the crest area of Glade Hill. The entrance, parking, visitor center, 

and Patowmack Canal areas of the park are located at the second highest terrace level.21

The topography and slopes at Great Falls Park are mapped in Figure 3.4: Site Topography and 

Slopes. The elevation of the property ranges from about 75 to 320 feet above mean sea level. In 

general, the property consists of rolling hill topography common to the Piedmont, as well as 

cliffs along the eastern boundary of the park, descending to the edge of the Potomac River. The 

average change in elevation from the top of the cliffs to the base is about 45 feet. Several 

drainage courses descend more gradually from the park to the river level. 

 

20 Potomac Gorge Site Conservation Plan, Nature Conservancy, 2001. 21

 Southworth, Scott. Geologic Map of the Potomac Gorge: Great Falls Park, Virginia, and Part of the C&O Canal 

National Historical Park, Maryland. USGS. 2000. 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.26

Data Source: NPS, 2002 

Figure 3.4: Site Topography and Slopes 
AFFECTED ENVIRONMENT 

3.27 NATIONAL PARK SERVICE 

Soils 

In 1963, the soils at Great Falls Park were mapped as part of the Fairfax County Soil Survey. An 

updated soil survey for Fairfax County is currently being conducted by the U.S. Department of 

Agriculture Natural Resources Conservation Service (NRCS). It is likely that the NRCS survey 

will result in changes to the list of soil series currently considered present at the park. 

According to the 1963 survey, the soils at Great Falls Park include eight specific soil series 

(Captina, Wehadkee, Glenville, Chewacla, Manor, Glenelg, Meadowville, and Elioak) and 

several generalized soil types including rocky land, very rocky land, mixed alluvial land, fill, 

pond, and unknown soils. The distribution of these units in the park was mapped in the 1963 

survey. In general, more poorly drained soils are present in the floodplain while moderately 

well-drained to well-drained soils are present on the rolling topography above the floodplain. 

The NPS Management Policies (2006) prescribe that “NPS will actively seek to understand and 

preserve the soil resources of parks, and to prevent, to the extent possible, the unnatural 

erosion, physical removal, or contamination of the soil, or its contamination of other resources.” 

3.3.2 Water Resources 

 

Watersheds and Resource Protection Areas

Within the park, drainage occurs toward the permanent streams of Mine Run and Difficult Run, 

as well as toward temporary tributaries of the Potomac River including the Patowmack Canal 

channel. The Mine Run Watershed is lightly developed, with land cover consisting primarily of 

forest and private residences of lots of two or more acres. Mine Run Watershed has a relatively 

low impervious surface ratio of approximately 5.2 percent. The Great Falls Park drainage area, 

including the Mine Run drainage, is located within the 88-square-mile Difficult Run watershed 

(as delineated by the Chesapeake Bay Program). Approximately 95 percent of the watershed is 

under the jurisdiction of Fairfax County. The Chesapeake Bay Program reports that the land 

cover of the overall Difficult Run Watershed is approximately 75 percent urban, 2 percent 

agricultural, 19 percent forest, 4 percent barren, and the remainder is water. In 2000, the 

population within the watershed was estimated to be 146,855.22

The Difficult Run Watershed is a component of the Middle Potomac-Catoctin Watershed, 

which encompasses 2,517 square miles.23 The Middle Potomac-Catoctin Watershed is within the 

14,679-square mile watershed of the Potomac River, which is within the Chesapeake Bay 

Watershed that totals 66,387 square miles.24

Watersheds of the Chesapeake Bay are protected and managed as vital habitat under the 

Chesapeake 2000 Bay Agreement, as signed by Virginia, Maryland, Pennsylvania, the District of 

Columbia, the Environmental Protection Agency, and the Chesapeake Bay Commission. In the 

Agreement, the signatory states establish goals for living resource protection and restoration, 

vital habitat protection and restoration, water quality protection and restoration, sound land 

 

22 Chesapeake Bay Program. http://maps.chesapeakebay.net/wsp/, 2002. 23

 Ibid. 24

 Ibid.
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.28

use, and stewardship and community engagement. In accordance with the Agreement, Virginia 

implements the Commonwealth’s Chesapeake Bay Preservation Act. Areas subject to the 

Chesapeake Bay Preservation Act include Resource Protection Areas (RPAs) and Resource 

Management Areas (RMAs). 25 RPAs include tidal shores; tidal wetlands; non-tidal wetlands 

connected by surface flow and contiguous to tidal wetlands, or water bodies with perennial 

flow; and, a 100-foot buffer located landward from these features. In Fairfax County, all areas 

which do not meet the RPA definition are designated RMAs.26 The RPAs within Great Falls Park 

are along the Potomac River, Difficult Run, and Mine Run, with the remainder of the park 

designated as RMAs. See Figure 3.5: Water Resources. A conservation plan for the Potomac 

Gorge, completed recently by the Nature Conservancy has emphasized the need for cooperative 

management and restoration on watersheds that embrace the gorge, including Great Falls Park.27

Surface Water

NPS Management Policies (2006) specify that surface waters should be perpetuated by NPS as 

an integral component of park aquatic and terrestrial systems. The two permanent streams 

present within the park, Difficult Run and Mine Run, flow into the Potomac River, which flows 

into the Chesapeake Bay. Clay Pond is another surface water feature in the park, located across 

the road from the northern-most parking area. These features are illustrated on Figure 3.5: 

Water Resources. 

As the river passes through the Potomac Gorge, it is a Sixthth-order stream. On average, the river 

exhibits a one-day mean discharge of 11,397 cubic feet per second (cfs), not adjusting for 

municipal water withdrawals.28

 

 

Groundwater

The project area is situated within the Piedmont province aquifer system. According to the 

Potomac Gorge Site Conservation Plan the hydrology of groundwater in the Potomac Gorge 

area has not been studied in detail, but was summarized by Feller in 1997 as follows29

: 

“Aquifers within the... Piedmont province are characteristically small, particularly in metamorphic strata... Springs are 

numerous, exhibit flow rates of low magnitude and many are seasonal. Nutter’s (1974) analysis of well data... suggests 

joints are probably the most important structural features for transmitting water within the strata and these disappear or 

become narrow with depth. Although precipitation is highest in spring and summer, the greatest input to groundwater 

aquifers occurs in winter and spring. Temporal recharge asymmetry is due primarily to phototranspiration uptake by 

plants during the growing season. When plants are dormant, from November to April, groundwater infiltration is 

highest and spring emergence flow rates peak.” 

Groundwater springs and seeps in the Potomac Gorge provide habitat for a variety of 

groundwater invertebrates including rare species.30 The locations of known seeps, as well as 

general areas of groundwater recharge at Great Falls Park are illustrated as ‘groundwater 

recharge’ in Figure 3.5: Water Resources. 

 

25

 Commonwealth of Virginia Chesapeake Bay Local Assistance Department. http://www.cblad.state.va.us, 2003. 26 Irons, Ellie L., Comments from the Commonwealth of Virginia Department of Environmental Quality on the Draft GMP/EIS, 

12 October 2005. 27

 Potomac Gorge Site Conservation Plan, Nature Conservancy, 2001. 28 Ibid. 

29 Ibid. 30

 Ibid.
AFFECTED ENVIRONMENT 

3.29 NATIONAL PARK SERVICE 

Data Source: NPS, 2002 

Figure 3.5: Water Resources 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.30

Wetlands and Waters of the United States

Activities affecting Waters of the United States (WOUS), including Special Aquatic Sites, are 

regulated by the U.S. Army Corps of Engineers (COE) under Section 404 of the Clean Water Act 

of 1977. WOUS are defined in 33 CFR Part 328.3(a) as “waters used in interstate or foreign 

commerce; waters subject to the ebb and flow of the tide; all interstate waters, including 

wetlands; all other waters such as intrastate lakes, rivers, streams, mudflats, sandflats, playa 

lakes, natural ponds (the use, degradation, or destruction of which could affect interstate or 

foreign commerce); and waters which are or could be used for recreation by interstate or foreign 

travelers, the taking of fish and/or shellfish sold in interstate or foreign commerce, or industrial 

purposes used in interstate commerce.” Special Aquatic Sites, which are regulated as a subset of 

WOUS, include sanctuaries, refuges, mud flats, vegetated shallows, coral reefs, pool and riffle 

complexes, and wetlands. Except for wetlands, none of these Special Aquatic Sites are present 

within the park. 

NPS specifically addresses the protection of wetlands on NPS parkland in the NPS Management 

Policies (2006), stating a goal to achieve net gain of wetlands across the park system by achieving 

no net loss of existing wetlands and by implementing restoration of previously degraded or 

destroyed wetlands. 

The National Wetlands Inventory (NWI) of the U.S. Fish and Wildlife Service produces 

information on the characteristics, extent, and status of the Nation’s wetlands and deepwater 

habitats. Both federal and state regulatory agencies utilize this information in determining 

locations of regulatory wetlands. In the project area, the NWI has identified wetlands at 

locations as illustrated in Figure 3.5: Water Resources. According to the NWI characterization 

of the wetlands in Great Falls Park, the area contains both palustrine (swamp) and riparian 

(streamside) wetlands. The NWI mapping of wetlands has not been field-tested in the park, and 

smaller wetlands (less than 0.5 acres) are not included due to the scale of aerial surveys. Small 

wetlands on site may include riverine wetlands along intermittent and perennial streambeds. 

Floodplains

The U.S. Federal Emergency Management Agency (FEMA) classifies areas of the nation 

regarding susceptibility to flooding. According to FEMA mapping, approximately 15 percent of 

the Great Falls Park land area is within the 100-year floodplain, as illustrated in Figure 3.5: Water 

Resources. In general, the lower drainage lying areas of Difficult Run, Mine Run, and the 

Patowmack Canal are in the 100-year floodplain. 

NPS Management Policies (2006) specify that NPS should manage floodplains on parklands to: 

“protect, preserve and restore the natural resources and functions of floodplains; avoid the 

long- and short- term environmental effects associated with the occupancy and modification of 

floodplains; and avoid direct and indirect support of floodplain development and actions that 

could adversely affect the natural resources and functions of floodplains or increase flood 

risks.” 

 

 

 

 
AFFECTED ENVIRONMENT 

3.31 NATIONAL PARK SERVICE 

Water Quality

With regard to water quality, NPS Management Policies (2006) specify that NPS will “determine 

the quality of park surface and groundwater resources and avoid, whenever possible, the 

pollution of park waters by human activities occurring within and outside of parks.” In 

addition, under the Chesapeake Bay Agreement of 2000, Virginia and the other signatories of 

the Agreement have committed to a goal to achieve and maintain the water quality necessary to 

support the aquatic living resources of the Bay and its tributaries and to protect human health. 

USGS studies the water quality of the major river basins and aquifers of the nation through the 

National Water Quality Assessment (NAWQA) program. In 1998, the NAWQA program 

published a report on Water Quality in the Potomac River Basin- Maryland, Pennsylvania, 

Virginia, West Virginia and the District of Columbia, 1992-1996. The report disclosed several 

major issues discovered in the Potomac River basin including: nutrients and pesticides in 

streams and groundwater, organic contaminants and metals in streams, and radon in ground 

water. 

The elevated concentrations of nutrients and pesticides in streams of the Potomac River Basin 

are among the highest in the nation at several sites, and are generally related to agricultural or 

urban land in the watershed. The concentrations of PCBs, organochlorides, trace elements, and 

semivolatile organic compounds (SVOCs) in streams that drain intensely agricultural or urban 

areas are also among the highest measured by the NAWQA program areas, and exceeded 

criteria for the protection of aquatic life at some sites.31

In general, the pesticides, nitrate, and dissolved solids present in the groundwater of the 

Potomac River Basin are related to agricultural land uses, particularly in carbonate aquifers. The 

occurrence of radon in the groundwater of the Potomac watershed is related to the geology of 

the aquifers. Rocks that contain more uranium, and are therefore associated with higher radon 

levels, include igneous, metamorphic, and carbonate rocks.32

 

Beyond the USGS assessment of water quality in the major U.S. watersheds, under the Clean 

Water Act of 1977, the EPA is responsible for developing water quality standards that define 

goals for U.S. waterbodies by designating uses, setting criteria to protect those uses, and 

establishing provisions to protect water quality from pollution. To assess water quality 

conditions, the EPA monitors criteria related to aquatic life, human health, bioassessment, 

nutrients, microbiology (pathogens), and wetlands.33

 

According to EPA data (managed by Virginia Department of Environmental Quality) from the 

year 2004, the Potomac was not impaired with regard to the designated uses within the vicinity 

of the park. However, 2.93 miles of Difficult Run was impaired, where the water body did not 

meet the state water quality standards for aquatic life use or recreation use.34 This includes the 

0.5 mile portion of Difficult Run that flows through the park. The source of the impairment is 

 

31

 USGS NAWQA Program. Water Quality in the Potomac River Basin- Maryland, Pennsylvania, Virginia, West Virginia and the 

District of Columbia, 1992-1996. 1998. 32

 Ibid. 33

 U.S. Environmental Protection Agency website, 2002. (http://www.epa.gov/waterscience/criteria/) 34

 Virginia Department of Environmental Quality website 

(http://gisweb.deq.virginia.gov/deqims/factsheet2004.cfm?tmdlid=VAN-A11R-01)
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GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.32

unknown. Three years of benthic macro invertebrate sampling indicates that the water quality in 

Mine Run is considered acceptable.35

The Nature Conservancy Potomac Gorge Site Conservation Plan reports the viability of both 

Difficult Run and Mine Run as fair. Mine Run supports relatively rich fish communities overall, 

but shows great variability in the richness of fish and benthic invertebrate species across 

different subwatersheds. Difficult Run exhibits moderate richness of fish communities, with 

average diversity in the communities higher than in many other Fairfax County watersheds. 

However, taxa richness in the benthic macroinvertebrate communities of Difficult Run varies 

greatly across subwatersheds. In addition, most of the macroinvertebrate communities sampled 

in Difficult Run were dominated by tolerant aquatic worms (oligochaetes). 

3.3.3 Biological Resources 

Vegetation

The vegetation of Great Falls Park includes a complex of upland and floodplain forest 

communities, as well as several rare vegetation types that occupy the bedrock terraces, exposed 

rocks, and frequently flooded river shores. Although disturbed, secondary forests are common 

in formerly cleared areas of the park, especially around the historical town of Matildaville, much 

of the contemporary forest consists of maturing second-growth stands that belong to the 

following ecological groups36 : basic mesic forest, mesic mixed hardwood forest, acidic oakhickory forest, oak/heath forest, and Piedmont/Mountain floodplain forest. Older-age stands (> 

100 years) occur on ridges at both the northern and southern ends of the park. Abrams and 

Copenheaver (1999) documented several white oak (Quercus alba) individuals more than 200 

years old on the northern ridge.37

The park’s complex topography, varied hydrological influences, and diversity of floodinfluenced habitats foster a corresponding diversity of vegetation types, some of them of 

significant conservation concern. On the bedrock terrace, the ancient oxbow west of the Old 

Carriage Road supports one of the largest known examples in Virginia of a Coastal 

Plain/Piedmont basic seepage swamp (G4G5/S2). On flats along the rocky rim of the terrace are 

two other rare forest communities that are scoured by periodic catastrophic floods: the 

Riverside Bedrock Terrace Pine Woodland (G1/S1), known only from the Potomac Gorge in 

Virginia and Maryland and the New River Gorge in West Virginia; and the Potomac River 

Bedrock Terrace Oak - Hickory Forest (G1G2S1), which is endemic to the Potomac Gorge. Rare 

communities of exposed rocks on the lower portions of the bedrock terrace, the gorge rim, and 

the river channel shelf include the Central Appalachian / Piedmont riverside prairie (G2G3S1) 

and the Potomac Gorge riverside outcrop barren (G2/S1). A substantial number of regionally 

rare plants associated with these rocky habitats are unknown elsewhere in Virginia, including 

 

35 Grulkowski, Darin, Rob Moreton, Melissa Kangas, and Brent Steury. NPS George Washington Memorial Parkway Stream 

Monitoring Program 2006 Annual Report. NPS, George Washington Memorial Parkway, McLean, Virginia. 2006.

36 Fleming, G.P., P.P. Coulling, K.D. Patterson, and K. Taverna. 2005. The Natural Communities of Virginia: Classification of 

Ecological Community Groups. Second approximation. Version 2.1. Virginia Department of Conservation and Recreation, 

Division of Natural Heritage, Richmond, Virginia (web site http://www.dcr.virginia.gov/dnh/ncintro.htm) 37

 Abrams, M.L. and C.A. Copenheaver. 1999. Temporal variation in species recruitment and dendroecology of an oldgrowth white oak forest in the Virginia Piedmont, USA. Forest Ecology and Management 124: 275-284. 
AFFECTED ENVIRONMENT 

3.33 NATIONAL PARK SERVICE 

Nantucket shadbush (Amelanchier nantucketensis), sterile sedge (Carex straminea), western 

sunflower (Helianthus occidentalis), and sticky goldenrod (Solidago racemosa).38

Finally, the frequently flood-scoured channel shelf of the river above the falls contains good 

examples of the Piedmont/Mountain Low Herb Sand Bar/River Shore, Water-Willow Rocky 

Bar and Shore, Sycamore-River Birch River-Scour Woodland, and Mixed Bedrock Floodplain 

River-Scour Woodland communities. While these have not yet been formally ranked by Natural 

Heritage ecologists, at least two of them are likely to be rare throughout their total range 

(globally rare) and as well as within their state range (state rare).39

Wildlife Habitat

Great Falls Park exhibits exceptional wildlife habitat within the context of the predominantly 

developed suburban environment. The diverse types of wildlife habitat existing in the park 

include uplands, terraces, cliffs, and riparian areas. 

A large population of whitetail deer utilize Great Falls Park habitat. In a 2001 study, deer were 

found in the park at an approximate average density of 88 deer per square mile; in 2002 the 

average density was found to be about 72 deer per square mile. Thirty-four deer per square mile 

were counted at Great Falls Park in 2004. The number has been decreasing due to controlled 

hunting that occurs at Riverbend Park. Ongoing research has suggested varying deer carrying 

capacities that allow for the maintenance of plant and bird biodiversity in habitats. Studies by 

whitetail specialist David Decalestra (for a different part of the country) have estimated that 

sustainable carrying capacity for deer habitat is about 40 deer per square mile. That 

recommended density has been used to gauge deer herd sustainability in the National Capital 

Region parks. Great Falls Park could potentially sustain a higher density herd if deer are feeding 

outside of the park. 

Rare, Threatened, and Endangered Species

While there are no Federally listed rare, threatened, or endangered species known to reside in 

the park, the Potomac Gorge area provides a variety of habitat for a diverse range of plants and 

animals. These include 28 plant species found in the park that are on the State list of rare, 

threatened or endangered species. 40In 2001, the Nature Conservancy prepared a plan to specify 

a protection strategy for the biological resources of the Potomac Gorge.41 To address 

conservation of the overall biological diversity of the Gorge, the Plan identifies threats to, and 

protection measures for, particular target biological resources (conservation targets) 

encompassing all known rare, threatened, and endangered species and communities in the 

Gorge including: riparian communities, terrace communities, upland forest blocks, tributary 

stream systems, rare groundwater invertebrates, anadromous and semianadromous fish, and 

 

38

 Townsend, J.F. Natural Heritage Resources of Virginia: Rare Plants. Natural Heritage Technical Report 04-06. Virginia 

Department of Conservation and Recreation, Division of Natural Heritage, Richmond, VA. 56 pp. plus appendices. 2004. 39 Irons, Ellie L. (Gary Fleming) , Comments from the Commonwealth of Virginia Department of Environmental Quality on the 

Draft GMP/EIS, 12 October 2005. 40 Townsend, John F. Natural Heritage Resources of Virginia: Rare Plants. Natural Heritage Technical Report 02-13. 

Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, Virginia. 2002. 41

 Potomac Gorge Site Conservation Plan, Nature Conservancy, 2001.
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.34

wetlands. The following paragraphs highlight sensitive species identified at the park in 

association with respective conservation targets. 

Sensitive Plant Species 

Relatively recently, record searches and field surveys were performed to identify sensitive plant 

species present at Great Falls Park. From October 1992 through September 1993, research was 

conducted by Cris Fleming to identify and locate rare plant species at the park.42 From October 

1993 to October 1994, Fleming conducted research to identify and locate watchlist and 

uncommon plant species present at the park.43 From late 2002 through 2004, Virginia Natural 

Heritage Program (VANHP) ecologist Gary Fleming documented additional rare species 

occurrences while conducting an intensive study of the park's vegetation ecology. VANHP 

botanist John F. Townsend and NPS botanist Brent Steury also documented rare plant 

populations during the past several years. The areas of sensitive vegetation habitat identified 

Cris Fleming's reports, as well as the more recent fieldwork, correspond to several of the 

conservation targets specified in The Nature Conservancy's conservation plan. 

 

Riparian communities occur along the Potomac River at elevations that flood relatively 

frequently and are dominated by species associated with floodplains (see Figure 3.6: Sensitive 

Plants and Habitats). Riparian communities are subject to stresses by: roads, trails and utility 

corridors; park facilities, operation, maintenance, and use; deer over-browsing; and invasive 

species. Overall, riparian communities in the Gorge are considered to have good viability based 

on good size, good landscape context, and the fair condition of resources (Nature Conservancy 

2001). At Great Falls Park, the sandy/gravelly shores and bedrock floodplain north of the falls 

provides habitat for rare species including Sparfina pectinata (G5S2), Eleocharis compressa

(G4S2), Solidago racemosa (G5T3S1), Desmodium cuspidatum var. cuspidatum (G5T5S2), and 

Hemicarpha micrantha (G5S1). The floodplain forest above the falls contains the rare species 

Hasteola suaveolens (G3G4S2), Erythronium albidum (G5S2), Maianthemum stellatum (G5S2), 

and a large colony of Valeriana pauciflora (G4S2). Watch list species identified in riparian 

communities at the park include Bapfisia australis, Cardamine douglassii, Carex conjuncta, 

Carex hirtifolia, Erigenia bulbosa, and Floerkea proserpinacoides. 

Terrace communities include bedrock terrace, outcrop, and cliff areas located at higher 

elevations along the Potomac River that are flooded less frequently than riparian areas and are 

dominated by upland species. Terrace communities are subject to stresses by: roads, trails and 

utility corridors; cultural resources; park facilities, operation, maintenance, and use; deer overbrowsing; and invasive species (Nature Conservancy 2001). Overall, terrace communities in the 

Gorge are considered to have good viability based on good size, good landscape context and the 

fair condition of resources (Nature Conservancy 2001). At Great Falls Park, the greatest 

concentration of rare plants occurs south of the falls in terrace communities. The globally rare 

Amelanchier nantucketensis (G3QS1), as well as the state-rare species Carex straminea (G5S1), 

Cerastium arvense ssp. Velutina (G4T4S2), Eleocharis compressa (G4S2), Helianthus 

occidentalis (G5S1), and Solidago racemosa (G5T3S1) occur in the bedrock terrace area. Another 

globally rare plant, Sida hermaphrodita (G2G3S1), was recorded in a gully of the bedrock terrace 

in 1979 but has not been seen recently. The rocky bluffs and sandy coves area supports the rare 

 

42 Fleming, Cris. Report on Rare Plant Search at Great Falls Park, Virginia, 1993. 43 Fleming, Cris. Report on Search for Watchlist and Uncommon Species at Great Falls Park, Virginia, 1994. 
AFFECTED ENVIRONMENT 

3.35 NATIONAL PARK SERVICE 

species Hasteola suaveolens (G3G4S2), Solidago rupestris (G4S1), Solidago racemosa (G5T3S1), 

Rhododendron arborescens (G4G5S2), Helianthus occidentalis (G5S1), and Cerastium arvense 

ssp. Velutinum (G5T4S2). Within the Terrace Forest area near Sandy Landing, the rare Arabis 

shortii (G5S2) and Onosmodium virginianum (G4S2) are found. The only known Virginia 

population of Carex davisii (G4S1) was recently found by Brent Steury on the Terrace near 

Matildaville. Watchlist species identified in terrace communities at the park include Baptisia 

australis, Cornus amomum ssp. obliqua, Juglans cinerea, and Packera paupercula. Regionally 

uncommon species found in the riparian and terrace communities at the park include Agalinis 

setacea, Apocynum sibiricum, Aralia nudicaulis, Arisaema dracontium, Asclepias verticillata, 

Aster schreberi, Celtis tenuifolia, Clematis viorna, Clitoria mariana, Commelina diffusa, 

Commelina erecta, Coreopsis tripteris, Coreopsis verticillata, Dirca palustris, Dryopteris 

cristata, Epigaea repens, Gentiana villosa, Iris cristata, Jeffersonia diphylla, Lathyrus venosus, 

Liatris spicata, Lilium superbum, Liparis lilifolia, Lycopus rubellus, Magnolia macrophylla, 

Matelea obliqua, Mecardonia acuminata, Myosotis verna, Orchis spectabilis, Orontium 

aquaticum, Passiflora lutea, Polygala verticillata, Ranunculus pusillus, Rhus aromatica, Rhus 

vernix, Rhynocospora glomerata, Rosa virginiana, Scleria triglomerata, Spiraea alba (S. latifolia), 

Trautvetteria carolinensis, Trientalis borealis, Tsuga canadensis, and Viburnum rafinesquianum. 

Upland forest blocks exist in the Potomac Gorge on rolling upland terrain that rarely or never 

experiences flooding. Upland forest blocks are subject to stresses by: roads, trails and utility 

corridors; cultural resources; park facilities, operation, maintenance, and use; deer overbrowsing; and invasive species. Overall, upland forest habitat in the Gorge are considered to 

have only fair viability based on the fair condition of resources, fair landscape context and poor 

size (Nature Conservancy 2001). In Great Falls National Park, the upland forest habitat contains 

rare examples of mature forest, including an old growth stand. As previously discussed, tree 

species in the old growth stand included: Quercus alba, Quercus rubra, Liriodendron tulipifera, 

Fagus grandifolia, Carya glabra, Acer rubrum, Nyssa sylvatica, and Ostrya virginiana (Abrams 

1999). The oldest trees in the stand are white oaks (Quercus alba) of 251, 232, and 208 years of 

age (Abrams 1999). With the exception of a 166-year-old Nyssa Sylvatica, the other trees in the 

stand were less than 100 years old. 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.36

Data Source: NPS, 2002 

Figure 3.6: Sensitive Plants and Habitats 
AFFECTED ENVIRONMENT 

3.37 NATIONAL PARK SERVICE 

Mammals 

Four species of bats were found to be present at Great Falls Park during a 2001 survey.44 None of 

the identified species are considered uncommon; however, the park does contain potential 

roost habitat for the Eastern small-footed myotis (Myotis leibii), a Virginia-listed S1 species. 

There are also historic records of the presence of the Eastern small-footed myotis at Plummers 

Island, approximately 10 miles north of D.C. in Montgomery County, Maryland. Additionally, 

the hoary bat is also likely to utilize habitat in the park during seasonal periods of movement 

(generally spring and fall).

Records indicate that the Allegheny woodrat (Neotoma magister), a Virginia-listed species of 

concern, was historically present at Great Falls Park. Usual habitat for the woodrat includes 

rock slides, talus, cliffs, boulders, and caves.45

Birds 

While no federally threatened or endangered birds have been documented nesting in Great Falls 

Park, a pair of bald eagles is known to have nested near the park on Conn Island for the last 12 

years. In 2002, the mating pair was not located, however the Conn Island area is still considered 

an active nesting site by NPS. 

The Nature Conservancy Potomac Gorge Site Conservation Plan lists eight species of Forest 

Interior Dwelling and neotropical migratory birds that are associated with upland forest blocks 

in the Gorge. Seven species are considered priorities for conservation by the Partners in Flight 

Program, and one additional species (the ovenbird) is included because it is a priority species for 

upland forest. The identified bird species and their respective micro-habitats within upland 

forest are listed in the following table. 

 

Table 3.4: Priority Conservation Bird Species of Potomac Gorge Upland Forest 

 

Minimum Habitat Size in Acres Common Name Scientific Name Micro-Habitat Use 

Marginal Suitable Optimal 

Worm-eating warbler Helmitheros vermivorus Understory 15 379 2,611 

Ovenbird Seirus aurocapillus Understory 2 22.5 575.5 

Kentucky warbler Oporonis formosus Understory 13 117 1,768.5 

Wood thrush Hylocichla mustelina Mid-Canopy to 

Understory 

0.5 0.5 64 

Yellow-throated vireo Vireo flavifrons Mid-Canopy 79 876 3,540 

Scarlet tanager Piranga olivacea Canopy 2 30 319 

Louisiana waterthrush Seiurus motacilla Streams 62 817 3,510 

Acadian flycatcher Empidonax virescens Streams 0.5 36 963 

 

44

 Hobson, C. S. 2001. Results of mist net surveys for the eastern small-footed myotis. (Myotis leibii) at Turkey Run and Great 

Falls Parks, Virginia, 1999-2000. Natural Heritage Technical Report #01-04. Virginia Department of Conservation and 

Recreation, Division of Natural Heritage. Richmond. 14pp.

45

 Mengak, M. T. 1998. Status of the Allegheny woodrat (Neotoma magister) in Turkey Run Park. Report to the National Park 

Service. Environmental Science Program, Ferrum College, Ferrum, Virginia. 7pp.
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.38

The microhabitats utilized by bird species reveal the vital habitat requirements for the species 

and determine the potential habitat threats that could adversely affect the species. Understory 

birds require well developed understory vegetation, dense ground cover, and large tracts of 

unfragmented nesting habitat. Deer damage to the understory is a potential threat to understory 

birds. Mid-canopy birds require well developed subcanopy and midstory vegetation, with a 

relatively open understory. Forest canopy birds require diverse midstory vegetation and an 

open understory and utilize the largest trees available in the canopy. Habitat fragmentation is a 

potential threat to forest canopy birds. Stream birds inhabit closed-canopy forest near water 

(preferably streams), with varying levels of understory. The protection of extensive contiguous 

moist and riparian woodlands is critical to the preservation of stream birds.

Great blue herons are another bird of concern in the Potomac River Gorge. While the area is a 

good habitat for these birds, according to the Maryland Department of Natural Resources, great 

blue herons exhibit more sensitivity to disturbance in comparison to bald eagles. 

Thirteen additional bird species that occur occasionally in Great Falls Park are listed on the 

Virginia Natural Heritage database of rare and watchlist species. Seven of the thirteen species 

are considered to be of special concern, including the Brown creeper (Certhia americana), 

Golden-crowned kinglet (Regulus satrapa), Hermit thrush (Catharus guttatus), Magnolia 

warbler (Dendroica magnolia), Purple finch (Carpodacus purpureus), Swainson’s Warbler 

(Limnothlypis swainsonii), and Winter wren (Troglodytes troglodytes). These birds are listed on 

the state database for breeding occurrences only. None of these species have been observed 

breeding Great Falls Park. 

Invertebrates 

In 1997, Christopher Hobson prepared a study to “verify the presence (or absence), distribution, 

and population status of specific elements of biological diversity: federally listed threatened or 

endangered species; proposed candidate species for federal listing; and animal species 

monitored by the Virginia DCR-DNH, focusing on those species associated with groundwater 

habitats within the GWMP,” including Great Falls Park. 46 The inventory resulted in the 

identification of two rare animal species within the GWMP area. The rare animals identified 

were the amphipods Stygobromus pyzzinii (Global rarity rank G2, State rarity rank S1S2) and 

Stygobromus sp. 15 (Global rarity rank G1, State rarity rank S1). These two rare amphipods, and 

the locally abundant but narrowly endemic (thus relatively rare) Stygobromus tenuis, are 

associated with the rare groundwater invertebrates conservation target of the Nature 

Conservancy.47

In sampling conducted by Hobson at Great Falls Park in 1994, 22 species of groundwater 

invertebrates were identified at 16 sampling sites (seeps). A more recent survey (February 2005) 

by Hobson, David Culver (American University), and others found both Stygobromus pyzzinii 

and Stygobromus sp. 15 to be present in groundwater seeps in the park.48 

 

46 Hobson, Christopher, A Natural Heritage Inventory of Groundwater Invertebrates Within the Virginia Portions of the 

George Washington Memorial Parkway Including Great Falls, 1997. 47 Potomac Gorge Site Conservation Plan, Nature Conservancy, 2001.

48

 Irons, Ellie L. (Gary Fleming) , Comments from the Commonwealth of Virginia Department of Environmental Quality on the 

Draft GMP/EIS, 12 October 2005.
AFFECTED ENVIRONMENT 

3.39 NATIONAL PARK SERVICE 

The following state listed species have also been documented in Great Falls Park:49

• Snails – Fontigens bottimeri (a freshwater snail, ranked S1S2 G2), and Striatura milium

(fine-ribbed striate, ranked S1S3 G4); 

• Moths – Acronicta radcliffei (Radcliffe’s dagger moth, ranked S2S4 G5), Acronicta 

spinigera (nondescript dagger moth, ranked S1S3), Anticlea multiferata (many-lined 

carpet, ranked S1S3), Anticlea vasiliata (variable carpet, ranked S1S3), Balsa tristrigella

(three-lined Balsa moth, ranked S1S3), Bellura brehmei (narrow-leaved cattail borer 

moth, ranked S1S3), Eutelia pulcherrima (beautiful eutelia, ranked S1S4), Euxoa violaris

(violet dart, ranked S1S3), Metarranthis indeclinata (pale metarranthis, ranked S1S3), 

Oligia crytora (mantled brocade, ranked S1S3), and Papaipema pterisii (bracken borer 

moth, ranked S3); 

• Dragonflies – Cordulegaster erronea (tiger spiketail, ranked S3 G4), Gomphus fraternus

(midland clubtail, ranked S1 G5), and Neurocordulia yamaskanensis (stygian 

shadowdragon, ranked S2 G5). 

Additionally, the first Virginia records for many species including a bee, a copepod, and 14 

species of leaf beetles have been found in Great Falls Park. 

Reptiles 

Difficult Run has been designated as a Threatened and Endangered Species Water, due to the 

presence of wood turtles, which are listed by the Commonwealth of Virginia as a threatened 

species. Other streams in the vicinity of the park also support this species. Wood turtles are 

found primarily in and near clear brooks and streams in deciduous woodlands. Although 

highly terrestrial, they typically remain in moist areas. 

 

49 Roble, S.M. Natural Heritage Resources of Virginia: Rare Animal Species. Natural Heritage Technical Report 06-10. 

Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond, Virginia. 2006.
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GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.40

 3.3.4 Air Quality 

Regulatory Framework

In response to the Clean Air Act (CAA) of 1970 and the CAA Amendments of 1977 and 1990, the 

EPA has established National Ambient Air Quality Standards (NAAQS) for the protection of 

human health and welfare. Current NAAQS are set for carbon monoxide (CO), ozone (O3

), 

nitrogen dioxide (NO2

), sulfur dioxide (SO2), lead (Pb), particulate matter equal to or less than 10 

microns in size (PM10), and fine particulate matter (PM2.5). The EPA assesses the status of 

compliance with the NAAQS for geographic regions specified throughout the United States. 

Regions that meet the NAAQS are called “attainment areas” and regions that do not meet the 

NAAQS are called “nonattainment areas.” EPA has designated the Washington DC 

metropolitan area as a nonattainment area for ozone.50

For nonattainment areas, the CAA requires that each state or air quality region develop a State 

Implementation Plan (SIP) that identifies how the state or air quality region will attain and/or 

maintain the primary and secondary NAAQS. Provisions of Sections 182 and 187 of the 1990 CAA 

Amendments emphasize strategies for reducing vehicle miles traveled for areas that have nonattainment status for O3

 and CO, respectively. 

General Conformity

The CAA Amendments of 1990 require the EPA to promulgate rules to ensure that federal 

actions conform to the appropriate SIP. These rules are known together as the General 

Conformity Rule (40 C.F.R. §§ 51.850-860 and 40 C.F.R. §§ 93.150-160), which requires any 

federal agency responsible for an action in a nonattainment area to determine that the action is 

either exempt from the General Conformity Rule requirements, or that the action conforms to 

the applicable SIP. The conformity assessment process is intended to ensure that federal agency 

actions: (1) will not cause or contribute to new violations of NAAQS; (2) will not increase the 

frequency or severity of any existing violations of ambient air quality standards; and (3) will not 

delay the timely attainment of ambient air quality standards. There are exemptions established 

and available in the General Conformity Rule. In addition, an agency may establish that the 

projected emission rates would be less than specified emission rate thresholds, known as de 

minimis thresholds, and that the emissions would be less than ten percent of the area’s annual 

emission budget. If these conditions are met, then the requirement to demonstrate conformity 

is not applicable (i.e., conformity of the project is presumed and exempt from conformity 

determination). 

Regional Air Quality Conditions

Great Falls Park is located within the National Capital Interstate Air Quality Control Region 

which includes Washington DC; Arlington, Fairfax, Loudoun, Stafford, and Prince William 

Counties in Virginia; the City of Alexandria, Virginia; and Montgomery, Prince George’s, 

Calvert, Charles, and Frederick Counties in Maryland. Air pollutant concentrations are 

measured at monitoring stations throughout the region to evaluate the air quality of the area and 

 

50 U.S. Environmental Protection Agency. Area Listings: Classification of Ozone Nonattainment Areas, 2004 (www.epa.gov) 
AFFECTED ENVIRONMENT 

3.41 NATIONAL PARK SERVICE 

to determine compliance with the NAAQS. Ambient air monitoring is conducted in accordance 

with EPA-approved methodologies, and standard operating and quality assurance procedures. 

The air in the Washington DC metropolitan area has exceeded the federal health standard for 

ozone (O3

) for the last approximately 25 years and the region was previously designated by the 

EPA as a “serious nonattainment area” for ozone. In 2002, EPA redesignated the region from 

serious to “severe nonattainment area” for ozone. The number of days per year of ozone 

violations ranged from a low of 2 to a high of 27 (Federal law allows only one violation of the 

standard a year, averaged over three years, in any one location in the region). The highest levels 

of ozone generally occur during the summer, from early May to late October, when the 

increased temperature and sunlight intensity enhance its formation. 

Ozone is a colorless gas formed in and downwind of urban areas when sunlight and high 

temperatures cause photochemical reactions between emissions of volatile organic compounds 

(VOCs) and oxides of nitrogen (NOx), called ozone precursors. Major sources of VOC include, 

but are not limited to, motor vehicles, gasoline storage facilities, and refueling stations. Principal 

sources of NOx, include motor vehicles, construction equipment, fossil fuel-fired power plants, 

and open burning.51

 

In the greater metropolitan Washington DC region, automobile traffic is also a principal source 

of localized carbon monoxide (CO). While it is difficult to associate ozone levels with local 

traffic levels, because ozone is not emitted directly, CO is directly emitted and concentrates 

locally around heavily traveled roadways and congested intersections. CO levels tend to be 

highest in the winter when cold weather causes automobiles to burn gas less efficiently. 

 

51

 Metropolitan Washington Council of Governments website (http://www.mwcog.org/environment/air/) 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.42

3.3.5 Noise Levels 

Introduction and Terminology

 

Noise is generally defined as unwanted or objectionable sound. The effects of noise on people 

include annoyance, interference with speech communication, sleep disturbance, and in the 

extreme, hearing impairment. Noise levels are measured and expressed in decibels (dB), on a 

logarithmic scale. Quantification of environmental sound commonly consists of evaluating the 

frequencies of a sound according to a weighting system that reflects that the human ear is not 

equally sensitive to all frequencies within the sound spectrum. Human hearing is less sensitive at 

low frequencies and extremely high frequencies than at mid-range frequencies. A method called 

“A-weighting” is used to filter frequencies not audible to the human ear. The typical A-weighted 

noise levels for common outdoor and indoor activities are shown in Table 3.5: Typical Noise 

Levels. 

 

While an A-weighted sound level may adequately indicate the level of environmental noise at 

any instant in time, community noise levels vary continuously. Most environmental noise 

includes a conglomeration of frequencies from distant sources, creating a relatively steady 

background noise in which no particular source is identifiable. Average noise levels over a 

period of minutes or hours are usually expressed as dBA Leq, or the equivalent noise level for that 

period of time. When no time period is specified, a one hour average is assumed. Construction 

noise standards are typically stated as average noise levels over a period of 1, 8, or 12 hours. 

Human perception of noise is complicated as there is no simple correlation of perception with 

acoustical energy. It is widely accepted that the average healthy human ear can barely perceive 

noise level changes of three dBA. Based on the results of many acoustical studies, it has been 

further accepted that a five dBA change is readily perceptible, and a ten dBA increase is 

perceived as twice as loud (Caltrans 1998). 
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3.43 NATIONAL PARK SERVICE 

Table 3.5: Typical Noise Levels 

 

Common Outdoor Activities 

Noise Level 

dBA Common Indoor Activities 

 --110-- Rock Band 

Jet Fly-over at 1,000 feet (300 meters) 

 --100-- 

Gas Lawn Mower at 3 feet (1 meter) 

 --90-- 

Diesel Truck at 50 feet (15 meters), at 50 mph 

(80 km/hr) --80-- 

Food Blender at 3 feet (1 m ) 

Garbage Disposal at 3 feet (1 meter) 

Helicopter (intermediate size) at 500 feet (150 

meters) --75-- 

Noisy Urban Area, Daytime 

Gas Lawn Mower, 100 feet (30 meters) --70-- Vacuum Cleaner at 10 feet (3 meters) 

Commercial Area Normal Speech at 3 feet (1 meter) 

Heavy Traffic at 300 feet (90 meters) --60-- 

Large Business Office 

Quiet Urban Daytime --50-- Dishwasher Next Room 

Quiet Urban Nighttime --40-- Theater, Large Conference 

Quiet Suburban Nighttime Room (Background) 

 --30-- Library 

Quiet Rural Nighttime Bedroom at Night, Concert 

 --20-- Hall (Background) 

Broadcast/Recording Studio 

 --10-- 

Lowest Threshold of Human Hearing --0-- Lowest Threshold of Human Hearing 

Source: Caltrans 1998. 

Regulatory Framework

Virginia does not currently have comprehensive state-wide noise regulations. Applicable 

Fairfax County noise regulations are stated in Chapter 108 of the Code of Ordinances for Fairfax 

County. The noise standards by general zoning districts in the county are listed in the following 

table. 

Table 3.6 : Fairfax County Environmental Noise Standards 

Zoning District Level 

Industrial 72 dBA 

Commercial 60 dBA 

Residential 55 dBA 

Source: Code of Ordinances for Fairfax County, 2002. 

The Federal Highway Administration (FHWA) has established traffic noise abatement criteria 

(NAC) for various land uses adjacent to proposed FHWA projects. The GMP/EIS is not an 

FHWA project and the FHWA criteria are not directly applicable, but are useful as an objective 

means of comparison for motor vehicle noise. Traffic noise impacts occur when the predicted 

traffic noise levels approach or exceed the noise abatement criteria, as shown in Table 3.7: 

FHWA Traffic-Related Noise Abatement Criteria, or when predicted traffic noise levels 

substantially exceed the existing noise levels. 
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GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.44

Table 3.7: FHWA Traffic-Related Noise Abatement Criteria 

 

Leq(h) Description of Activity Category 

 

57 dBA Lands on which serenity and quiet are of extraordinary significance and serve an 

important public need and where the preservation of those qualities is essential if the area 

is to continue to serve its intended purpose. 

67 dBA Picnic areas, recreation areas, playgrounds, active sports areas, parks, residences, motels, 

hotels, schools, churches, libraries, and hospitals. 

72 dBA Developed lands, properties, or activities not included in categories A or B above. 

None Undeveloped lands. 

52 dBA Interior of residences, motels, hotels, public meeting rooms, schools, churches, libraries, 

hospitals, and auditoriums. 

Sensitive Noise Receptors

Sensitive noise receptors are generally considered to be human activities or land uses that may 

be subject to the stress of significant interference from noise. Land uses associated with 

sensitive receptors include residential dwellings, mobile homes, hotels, motels, hospitals, 

nursing homes, education facilities, and libraries. Sensitive receptors may also include 

threatened or endangered noise-sensitive biological species. Commercial and industrial land 

uses are not considered “noise sensitive” by most definitions. However, jurisdictions may have 

noise/land use compatibility standards or noise impact standards that apply to commercial and 

business uses. 

 

The known sensitive noise receptors currently within the park include the educational facilities 

of the visitor center. The off-site noise sensitive receptors of concern in the study area are the 

residences close to the roadways that would carry the greatest volumes of project-generated 

vehicle traffic. Specifically, the residences adjacent to Georgetown Pike, Old Dominion Road, 

and Riverbend Road are potentially of interest with regard to noise. 

3.3.6 Hazardous Materials 

A review of the EPA’s and the Virginia Department of Environmental Quality’s databases 

regarding hazardous waste indicates that neither the park nor any abutting sites were identified 

as federal or state Superfund or potential Superfund sites.52 Also, neither the park, nor abutting 

sites were identified as being engaged in the treatment, storage, and/or disposal of hazardous 

waste. 

Based on its age, the visitor center may contain outdated, now hazardous, materials such as leadbased paint and asbestos-containing materials. This may also be the case for the maintenance 

facility. If disturbed, these materials are potential health hazards through ingestion, absorption, 

or inhalation of airborne particles.

 

52 http://www.deq.virginia.gov/waste/hazardous.html 

 http://www.epa.gov/superfund/sites/cursites/index.htm 

 http://www.epa.gov/enviro/html/rcris/rcris_query_java.html 

 (Database Search of performed on November 28, 2006)
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3.45 NATIONAL PARK SERVICE 

3.4 TRANSPORTATION SYSTEM 

 

The following section provides an overview of existing traffic access, parking, and circulation 

patterns at Great Falls Park, including traffic volumes, available parking, parking utilization, and 

typical queue sizes. This summary is based on a variety of information sources including data 

obtained from the NPS, data gathered at Great Falls Park, phone interviews of park users, 

feedback from local emergency service providers, and public comments received at a public 

scoping meeting. 

Parking Supply

Great Falls Park is served by three paved parking lots, with a total of 533 parking spaces, 

including 12 designated as handicapped parking spaces. All of the parking spaces at Great Falls 

Park are designed for passenger cars. There are no designated spaces for buses, oversized 

vehicles or horse trailers. The upper lot, which contains 173 regular parking spaces, is generally 

used for overflow parking when the main lot fills. Several spaces at the northern end of the 

upper lot are taken up by trash dumpsters. The main lot is located near the visitor center and 

contains 261 parking spaces, including eight handicapped spaces. Five of the spaces in the main 

lot are reserved for park staff. The lower lot, which was constructed in 2002, contains 99 

parking spaces, including four handicap-accessible spaces. This lot is frequently used by rock 

climbers and boaters, and therefore, is sometimes referred to as the “Climber’s Lot”. 

Roadway Access

The only vehicular access to Great Falls Park is from Old Dominion Drive, a narrow two-way, 

two-lane road (10-foot lanes with no shoulders) that continues for approximately one mile from 

Georgetown Pike to the park entrance station. In addition to the park, Old Dominion Drive 

provides access to 10 single family homes that share two common driveways. At the entrance 

station, visitors pay a parking fee and are provided with maps of the park. Park staff indicated 

that in recent years on peak weekends, traffic has queued back from the entrance station along 

Old Dominion Drive. They estimated that, to their knowledge, these queues had not reached as 

far as the Georgetown Pike intersection. The frequency (10-12 times per year) and typical length 

of the peak weekend queues (usually extending about one-half to three-quarters of the way to 

the Georgetown Pike intersection) was generally corroborated by public comments received 

during the public scoping meeting and by comments received from various park users who were 

interviewed as part of the development of this plan. A new entrance station was recently 

constructed, and opened in June 2003. 

 

Traffic Volumes 

An initial assessment of traffic characteristics at Great Falls Park was made based on historical 

traffic count data obtained from NPS. The data covered an entire year, from September 2000 

through August 2002 (2001 data was unavailable) and consisted of traffic volumes collected 24-

hours-a-day by in-road sensors installed on Old Dominion Drive near the entrance fee station 

within the park. The data indicated the following trends: 

y The peak season is from May to September; 
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GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.46

y Saturday and Sunday are the peak days; 

y Sunday generally has the highest volume and was the peak day of the month for nine of 

the 12 months. Saturday was the peak day for two of the 12 months, and Christmas 

(Monday) was the peak day in December (however, the patronage was much lower on 

this day than the other peak days); 

y During the peak months, an average of approximately 490 vehicles are typically on the 

site during the peak weekend hour, compared to an average of 190 vehicles on the site 

during the peak hour from October to April; 

y On the peak day of the year (Sunday, May 5, 2002), 535 vehicles were on-site during the 

peak hour; 

y The peak hour for entering traffic is usually between 1:00 pm and 2:00 pm during the 

peak season; 

y The peak hour for exiting traffic varies more throughout the peak season (2:00 pm to 

6:00 pm); 

y The largest volume of traffic entering the park in a single day was 1,528 (Sunday, May 5, 

2002); 

y The figure below summarizes the inbound and outbound flow of vehicles at Great Falls 

Park on the peak day of Sunday, May 5, 2002: 

 Flow Through Great Falls Park On the Peak Day (May 5, 

2002)

0

50

100

150

200

250

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time of Day (hr)

Veh/hr

Entering

Exiting

Figure 3.7: Summary of Inbound/Outbound Vehicular Flow on a Peak Day 

Indicates one-in, one-out operations 
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3.47 NATIONAL PARK SERVICE 

y When comparing traffic volumes to visitor totals obtained from the NPS, the average 

vehicle occupancy is approximately 2.5 visitors per vehicle; 

y Park records indicate that about 275 heavy vehicles enter the park each year. This 

includes approximately 200 school buses, 25 tour buses, 25 delivery trucks, and 25 

tractor-trailers that enter the park accidentally; and 

y Historical traffic data indicates a slight decline in total traffic on Georgetown Pike 

outside the park over the last 10 years (approximately 5 percent reduction from 1991 to 

2001). 

 

To get a better indication of typical daily traffic patterns during a peak day, traffic was manually 

counted on Sunday, June 1, 2003 from 7:00 AM to 8:15 PM. This date was selected because it fell 

in a month that historically generated some of the highest visitor totals of the year. Attendance 

is dependent on weather conditions, and the day of data collection, while forecasted to be warm 

and sunny, turned out to be fair. 

Data was collected on Old Dominion Drive just prior to the entrance station. Since Old 

Dominion Drive is the only access road to the park, this count should reflect all vehicles that 

entered and exited the park. A total of 1,345 vehicles entered the park, including five 

trucks/buses/carpool vans and two vehicles with trailers. This total represented approximately 

85 percent of the peak daily attendance in 2002. Compared to the historical count data obtained 

from the NPS - despite the weather being “good” but not “great” - this volume was still 

representative of an average June weekend day. The peak hour traffic flow of vehicles entering 

the park was 210 vehicles/hour, which occurred between 2:00 pm and 3:00 pm. The peak flow of 

vehicles exiting the park was 218 vehicles/hour, which occurred between 4:45 pm and 5:45 pm. 

Parking Demand

In addition to traffic counts, on June 1, 2003, the number of vehicles parked in each of the three 

lots was counted at a half-hour interval throughout the day between 7:30 am and 8:00 pm. The 

maximum number of vehicles parked at Great Falls Park on the day of the data collection was 

403, which occurred at 3:00 pm. The main lot was filled (100 percent capacity) from 1:30 pm to 

5:00 pm. The lower lot reached 77 percent capacity at 3:30 pm, while the upper lot reached 48 

percent capacity at 2:30 pm. 

Although the park never reached its total parking capacity on the day of the data collection, park 

staff indicated that all three parking lots typically reach capacity (approximately 500 spaces) 

about 10 to 15 times per year during the peak days. 

Entrance Station Processing Rate

The time required to process a vehicle entering the park at the entrance station was also 

recorded randomly throughout the day on June 1, 2003. A total of 100 samples were taken in the 

morning, during midday, and in the afternoon, and also reflect several different staff members 

operating the booth. The average processing rate was found to be 21 seconds/vehicle. This 

equates to a capacity of about 170 vehicles/hour that can enter the park via the single-lane 

entrance station, which was the case during the data collection on June 1, 2003. As noted in the 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.48

previous “Traffic Volumes” section, this rate was exceeded during the peak hour (210 

vehicles/hour), resulting in a queue of approximately 650 feet. 

Queue Lengths

 

As noted previously in the “Roadway Access” section, long queues of vehicles entering the park 

occur on Old Dominion Drive an average of 10-12 times each year. Based on the historic traffic 

volume data, the entrance station processing rates, the current size of the three parking lots, and 

comments from the park staff who operate the parking lots, it appears that these long queues are 

the result of two factors: 

• On peak days, the flow of arriving vehicles may exceed the ability of the park staff to 

process them through the entrance station. This is what happened on June 1, 2003. 

• In the event that the 521 existing parking spaces fill completely, vehicles are not 

permitted to enter the park until other vehicles leave. At this point, the park operates a 

one-in, one-out process, and vehicles waiting to enter the park queue in a single line 

along Old Dominion Drive. A manually operated foldout sign indicating “Lots Full” is 

sometimes displayed on Old Dominion Drive when this occurs. 

Emergency Access

 

Company 12 Fire Station in Great Falls, Virginia was contacted to obtain feedback regarding 

emergency vehicle access to Great Falls Park, and provided the following comments: 

• The fire company recognizes that there are traffic queues on Old Dominion Drive during 

the peak summer weekends (typically in August). However, this problem is not unique 

to Great Falls Park and, therefore, they expect it and deal with it accordingly. 

• The trails throughout the park are generally adequate for emergency vehicle access. It 

was noted that “about 90 percent” of the trails are accessible and wide enough to get all 

of the fire equipment through. 

• The fire company sometimes uses Old Carriage Road to enter the park. This is a dirt 

road, but it is wide enough to handle their big trucks. Occasionally, this road requires 

grading-related maintenance. 

• The primary concern addressed by the fire company was the Sandy Landing boat ramp, 

which they use to launch boats for rescues. According to the Fire Station, this ramp is 

unable to accommodate all of their equipment. An engineering study conducted to 

redesign this ramp has been completed and reconstruction is currently being 

undertaken. 
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3.49 NATIONAL PARK SERVICE 

User Feedback

 

A telephone survey of permit-holding climbing and boating schools that use Great Falls Park 

was conducted to obtain their feedback regarding traffic and parking issues. The following 

general comments from the groups were noted: 

• Long delays are experienced when trying to access the park at midday on the weekends. 

Most permit-holding groups try to arrive early in the day to avoid the rush. Delays at the 

gate make it difficult for groups to meet within the park at a given time. 

• The groups expressed interest in having a parking permit and specific locations to park a 

bus. While buses and 15-passenger vans are available to most groups, they are difficult to 

park on site. Therefore, the rock climbing groups usually don’t use the buses and 

everyone drives individually, which contributes to the parking shortage in the park. 
CHAPTER 3 

GREAT FALLS PARK, VIRGINIA y FINAL GMP/EIS 3.50

3.5 SITE UTILITIES 

Great Falls Park has four buildings located within the park boundaries. These facilities are the 

entrance station, visitor center, maintenance building, and comfort station. The majority of the 

buildings are located in the north central section of the park. The comfort station is 

approximately 300 feet south from the lower visitor parking lot. These on-site buildings, as well 

as the USPP trailer, have utility hook-ups. 

 

3.5.1 Water 

 

The water supply distribution system is a stand-alone system under the jurisdiction of the NPS. 

A 30,000-gallon water storage tank feeds the park facilities. The storage tank is located in the 

northwestern part of the park and can only be accessed from outside the park using Jackson 

Lane. Located 100 feet east from the storage tank is a 5-foot by 5-foot concrete well. A pump 

inside the well supplies water to the tank via a 2-inch line. A 6-inch ductile iron gravity trunk 

line from the storage tank supplies potable water to the park’s distribution system. Water is 

supplied through this distribution system to the comfort facility, entrance station, maintenance 

building, and the visitor center. 

One fire hydrant is identified in the park, located just south of the maintenance building. The 

distribution system appears to have valves placed in strategic locations to isolate parts of the 

system, if necessary. 

3.5.2 Sanitary Sewer 

 

There is a large sanitary sewer interceptor that enters the park from the south and extends 

north. This system is part of the Potomac Interceptor, an extensive system, which spans several 

counties throughout Virginia and Maryland. The system begins in the District of Columbia and 

follows the Potomac River through Maryland. It crosses into Virginia following the route of the 

Potomac River and then turns southwest, paralleling the Loudoun and Fairfax county 

boundary, into Dulles Airport. 

The sanitary sewer branch that enters the park is a 54-inch reinforced concrete line. The sewer 

flows from the south towards the north bisecting the park. It is within a 60-foot easement, with 

the line located in the center of the easement through most of the park. Due to the park’s 

topography, the depth of the sewer line varies from 20 feet to 3 feet of cover. There are sewer 

manholes, approximately 900 feet apart and 48-inches in diameter, along with air-intakes or 

vents associated with each manhole. Sanitary sewer laterals from the park facilities flow into the 

54-inch branch line. 

3.5.3 Electric Supply 

 

Dominion Virginia Power provides electricity to the park. The estimated demand of power for 

the park is approximately 200kW. The electrical system consists of overhead power lines and 

below-grade conduits. The overhead electrical service enters from the west side of the park at 

two locations, through a possible easement off of River Bend Road, and off Jackson Lane. The 

underground conduits are for service connections to the various buildings within the park. 
AFFECTED ENVIRONMENT 

3.51 NATIONAL PARK SERVICE 

3.5.4 Telephone System 

Similar to the electric system, the land line telephone phone system consists of overhead lines 

and underground conduits and enters from the west property line of the park from Jackson 

Lane. It appears the telephone lines are attached to the Virginia Electric and Power (VEPCO) 

power poles and follows the VEPCO pole line into the park and to the adjacent park facilities 

Bell Atlantic Mobile constructed a 150-foot, freestanding monopole and adjacent equipment 

building that provides cellular telephone communication for users within the park and 

surrounding area. The monopole also houses NPS radio equipment. The monopole and 

equipment building are located along the Ridge Trail, less than 100 feet east of Old Dominion 

Drive. 

3.5.5 Gas Supply 

 

There is no indication of a natural gas distribution system or propane storage facilities within the 

park. Also, there is no indication of a gas transmission pipeline passing through the park or the 

indication of a natural gas pipeline easement. 

 

3.5.6 Stormwater Drainage 

 

There are isolated storm drainage systems located near the visitor center building, the north 

parking area and some roof drainage from the entrance station. The majority of the storm 

drainage from the visitor center is within the area located in the courtyard between the two 

wings of the visitor center. The courtyard is paved with concrete and is graded towards two 

catch basins approximately 50-feet diagonal from each other. There is an 8-inch pipe that 

connects the catch basins and the outfall line is a 10-inch pipe. The outfall line flows south from 

the courtyard and connects to a manhole approximate 60 feet away. The manhole also receives 

stormwater from a system that collects drainage from the visitor center building walkway and 

overhang. There is a 10-inch outfall pipe from the manhole that flows approximately 50 feet east 

to the Potomac Canal. 

The parking lot upper and main parking lots drain into catch basins that discharge water into the 

Potomac Canal. The entrance station has a 3-inch storm drain that collects roof runoff. This 

drain flows eastward and connects to the Potomac Interceptor. 

3.5.7 Solid Waste Disposal 

Solid waste is stored within the park in three dumpsters that are emptied by a private contractor 

on a weekly basis. Recyclable materials such as cardboard, plastic, and glass are stored separately 

and are also removed periodically by a private contractor.