Difficult Run Stream Valley Park


The more intense mountain bikers have known about for Difficult Run for some time.  Equestrians have known it longer.  Eight miles of unpaved trail, the Rails to River Trail (RRT), along creeks connects Reston to the Potomac River.  Bridges carry most of the busy roads overhead so you’re left with miles to enjoy nothing but the woods and the wildlife.  The price you have to pay if you’re running it is not only the sweat from the distance, but also navigating the waters themselves.  Even during July in the drought of 1999, occasional puddles could be found on the trail.  Wait until summertime after a long break between rains before attempting this, not only to save yourself some grief from the mud or potential high-water creek crossings (most without bridges), but also to prevent further erosion. 


Getting There


From the Capital Beltway, I-495

Take Exit 13, for Georgetown Pike, Rte. 193, west.  After 3.6 miles, turn left into the parking area.  As you turn left into the gravel lot, the trail head going south crosses the creek on your right (on stepping stones).  The way to the Potomac River north is beyond the gate at the end of the lot after the creek crossing on the right. 


Area Routes


River and Quarry (4.4 or 2.2 miles, IV, or II)

For those not ready to test themselves on the way south, a more modest challenge can still be had by going north toward the Potomac River and into Great Falls Park.  The first third of a mile is somewhat flat and on the dirt RRT.  The trail splits and merges on parallel paths as a result of people trying to avoid the puddles of the flood plain.  After crossing under Georgetown Pike, follow the gravel trail downward.  You’ll drop about 100 feet over the next 0.7 miles if you go all the way to the river.  For the longer route, turn left before getting to the river, up a short but steep gravel path to the Ridge Trail.  On the ridge, you’ll roll over hills but mostly climb to the Old Carriage Road.   To make a loop, turn right almost immediately onto the Matildaville Trail (no bikes).  You’ll be able to catch glimpses of the Mather Gorge and the remains of the Potowmac Canal.  The Potowmac Canal operated from 1802 to1828, allowing merchants to get past the 76 foot drop of Great Falls on the river.  It took 17 years to build the canal. The trail eventually passes through and old quarry used for making the locks.  The quarry has a crater-like appearance.  Rocky walls surround a grassy interior.  Just past this, turn around to the left, on the Old Carriage Road and return. 


Difficult Run (11.35 miles, X)

Wet Run might be a more appropriate name for this route.  The trail stays wet long after rains have past.  Don’t try it if thunderstorms threaten because you must cross the creek without benefit of bridges several times and the waters can get higher.  Previously named the Difficult Run Trail, the trail is now named the Rails to River Trail.  It connects the Washington and Old Dominion Trail (W&OD), a former railroad grade, to the Potomac River.  Wear a trail shoe if you have one; some are designed not to hold a lot of water and that will help you here.  The heavily wooded trail is for those who are adventurous.  It’s not been sanitized with improved pavements, drinking fountains or nearby phones.  If you wind-up needing help you may have to wait until someone passes by.  It’s these characteristics that makes the trail so appealing to most who try it.  Though the way can be isolated, I happened to come across a group of 15 police officers who were out enjoying themselves on bikes. 


Bikers with gusto go right to work on this by leaving the parking lot and splashing their way across Difficult Run.  It takes a head of speed and some skilled steering to get across because the water is over a foot deep in places.  If you’re running, you might be able to avoid getting wet just yet.  The less enthusiastic can rock hop their way across if the water is low enough and if the rocks, well placed by other passers-by, have not been washed away.  Just over a quarter mile upstream, a second crossing must be made.  On this one, you’ll have the benefit of concrete underfoot.  You might be able to jump over the deepest of the water but watch out for it being slippery underneath.  The way is flat for the next thee tenths of a mile.  Look for a third crossing a hundred yards past the remnants of an old cabin.  The crossing is identified by a muddy gully dropping into the water, and the crossing is sharply to the left.  If you miss it you’ll run into private property.  On this crossing, the downstream angle of approach keep you in the shallows but lengthens the crossing.  You can’t avoid getting wet, unless your on a bike.  For the next 1.7 miles, there are no creek crossings and the way continues to be mostly flat.  You’ll pass Ramey’s Meadow Park at Lee Mill Rd. on the way.  Jumps are setup at that park for those on horseback.  The last creek crossing can be made dryly by rock hopping again.  A gravel road after that takes you near Leesburg Pike, Rte. 7.  At this point, horses are routed to the left under the highway.  Go straight over the road instead. 


At Leesburg Pike, Rte. 7, cross at a traffic light and begin following Colvin Run.  The trail starts climbing more from this point on the way to Lake Fairfax Park.  It remains wooded.  In Lake Fairfax Park, follow the RRT past the picnic area and fields until you intersect a nature trail identified by red blazes.  The nature trail takes you through a campground where you can get a drink.  Continuing on, cross the Lake Fairfax dam.  Snacks and drinks can be purchased at the pool near the dam.  Turning right after the dam, go through a picnic area and return on the RRT.  The route through Lake Fairfax Park is hilly. .  Return from the picnic area, down Colvin Run and Difficult Run on the RRT. 


Nearby and Connecting Zones



What to do Afterward


Food and Drink

Café Oggi - 703 442-7360

Greek Taverna - 703 556-0788

Kazan Restaurant - 703 734-1960



Entertainment and Edification

Great Falls Grange & Old Schoolhouse - assembly hall & one room school house - 703 938-8835

Colvin Mill - off Leesburg Pike - 703 759-2771

Meadowlark Gardens - 703 255-3631

River and Quarry

Distance:          4.4 or 2.2 miles

Rating:  IV or II; paved trail on the shorter route; roads and hill on the longer one; sunny


4.4 Mile Route


       0.0   south from parking lot, through the gate; Rails to River Trail (RRT); go downstream & do not cross creek

       0.35 underpass Georgetown Pke, Rte 193


BR  0.4   onto road-like gravel trail; Difficult Run Trail/RRT

       0.45 trail X on L


L     0.9   Ridge Trail(steep gravel trail)


L     0.95 at T to stay on Ridge Trail

       1.1   coral for horses


       1.45 River Trail on R (no bikes)

       1.7   trail X on R


BR  1.75 before Carriage Rd & stairs on L


R     1.8   Matildaville Trail (no bikes)

       2.05 trail X on R to River Trail


L     2.15 at T (unmarked)


UL  2.25 just past the quarry; Carriage Rd


BL  2.6   to Ridge Tr; Matildaville Tr on L


BL  2.65 Ridge Trail

       2.7   trail X on R

       2.95 River Trail on L (no bikes)

       3.3   coral for horses


R     3.45 down to RRT/Difficult Run Trail; (!)


R     3.5   RRT/Difficult Run Trail


       3.95 trail X on R


BL  4.0   RRT on L; R is to road

       4.05 underpass Georgetown Pke, Rte 193

       4.4   parking & trail crosses creek on L



*2.2 Mile Route


S     0.9   Ridge Trail on L goes up steep hill

       1.05 trail X


U    1.1   Potomac River

       1.15 trail X

       1.3   Ridge Trail on R goes up steep hill (pickup cues at mile 3.95 on 4.4 mile route)

Difficult Run

Distance: 11.35 miles

Rating:           X; shady, often muddy trails w/wet creek crossings; mostly flat, but hills midway


CR  0.0   from parking lot cross Difficult Run on stones (!); go upstream

       0.35 cross Diff Run on wet concrete (!)

       0.4   underpass Old Dominion Rd

       0.6   old cabin


L/R 0.65 sharp L at muddy gully; angle downstream to cross Diff Run (!); no bridge (time to get wet)

       0.75 trail X on L

       0.8   rocky outcrop

       1.05 cross stream past house w/chimney

       1.15 trail X on L to house

       1.45 Leigh Mill Rd; Ramey’s Meadow

       1.75 trail X on L

       2.4   cross Diff Run on stones (!); gravel rd

       2.95 concrete bridge; begin paved road; horse trail turns L


L     3.1   Colvin Mill Rd;


CR  3.15 cross Leesburg Pike, Rte 7; road becomes Carpers Farm Way; R to continue RRT

       3.8   wooden bridge

       4.05 wooden bridge

       4.1   trail X on R

       4.4   Hunter Mill Rd; Lake Fairfax Park


L     4.5   at split to follow horse trail

       4.55 park road X; start climb ahead


R     4.95 field at the hilltop; R at the fence

       5.0   trail leaves the field; down to creek

       5.1   trail on R merges before xing creek

       5.3   trail on L merges

       5.45 trail X on R

       5.5   soccer fields; follow horse trail signs


R     5.6   trail X upon entering woods; Nature Trail; red and white blazes


R     5.9   gravel road at campground; C-34

       6.0   gravel road X on L; water/restrooms

       6.25 through the gate closing the road to the lake


R     6.45 after xing the dam, go across grass & to road going down to the picnic area


L     6.65 onto gravel rd after xing Colvin Run


BR  6.7   at split in the road; toward pavilion


L     6.8   gravel road is the RRT


BR  6.85 trail X on L merges; leave picnic

       6.95 Hunter Mill Rd; leave Lake Fairfax

       7.25 trail X on L

       7.3   wooden bridge

       7.55 wooden bridge


L     8.2   Carpers Farm Way; cross Leesburg Pke, Rte 7; becomes; Colvin Mill Rd


R     8.25 unmarked service road

       8.4   horse trail on R before concrete bridge; follow gravel road S

       8.95 cross Diff Run on stones (!); dirt trail

       9.6   trail X on R

       9.9   Leigh Mill Rd; Ramey’s Meadow

     10.2   trail X on R to house

     10.3   cross stream before house w/chimney

     10.6   rocky outcrop; trail X on R afterward


L/R 10.7  angle upstream to cross Diff Run (!); no bridge (time to get wet again)

     10.8   old cabin

     10.95 underpass Old Dominion Rd

     11.0   cross Diff Run on wet concrete (!)

L   11.35 cross Diff Run on stones (!); parking

Difficult Run