Running (Street & Trail) 1:26:47  8.26 mi (10:30 / mi) +186m 9:49 / mi
Black Hills Regional Park; Boyds, MD. Starting from the Little Seneca Boat Launch, on Clarksburg Rd., I went north across the bridge over the lake where there used to be Ten Mile Creek many years ago (there's a wide shoulder on the bridge and further north for a little while). The lake is one of the larger drinking water reservoirs in the area. I got on the extension of the Hoyles Mill Trail on the north side of the bridge, returned to Clarksburg Rd., and continued north. I took the Cool Spring Run Trail to the northernmost end of the lake and soon after I got on the Ten Mile Creek Trail. The Ten Mile Creek Trail took me all the way back to where I'd started. I had printed and taken a country trail map with me, and I read it along the way. It was mostly accurate and I was glad to have it. When I'd finished, my watch had registered 1,200 ft. of climb, but that seems to have gotten adjusted down to half of that. The trails seem mostly well graded but designed for mountain biking with many small ups and downs. For a little while in the middle of the run, the ball of my right foot was feeling like the callus on it was hurting it. My left knee ached a little toward the end.
The Ten Mile Creek Trail goes up and down fingers of the lake and it's larger reentrants. There's a mix of thick, and open forest along the trail, but the park land is mostly too narrow to be effective for orienteering usage.
From the north end of Clarksburg Rd. to the south end of it, a distance of 6.45 miles, there was only about 3 steps on pavement. That was crossing Ganley Rd. where it dead ends. I'd explored some of the west side of Black Hills Regional Park before, but that exploration was about 21 years ago. I was mountain biking with a GPS at the time, and doing it for a running guide book that I was making. There were some big fields then, but now those areas appeared to be tree covered (probably the thick forests that I saw). The route made a really fun run for me, and I had a great day to do it on--sunny and in the 50s F. There are a lot of good views to be seen with the trail often high over the water, and there being no leaves to block one from seeing far away. The ground at the shoreline tends to be steep. The water looked deep too, with a pleasant green color. The trail tends to get close to the water at the mouths of the lake fingers.
With the long shape, the lake seemed similar to some Scottish Lochs. Initially there were few people to see, but as I got closer to the southern end, more people were to be found hiking and cycling.
Doing the loop as I did it is probably not common. I guess that most probably go out and back on Ten Mile Creek Trail from where I started/ended. Where the trail emerges north of the lake bridge, the upper parts of Clarksburg Rd. incur a steadily climb, but the road also narrows there with no shoulders. People drive fast on it.