Seeps are small, ground water springs that bubble to the surface through small pores. The amount of discharge from a seep is not as evident as from a spring. Seeps and springs at the Summit Unit near Cresson, PA form the headwaters for Blair Gap Run to the east, and to the lesser extent, Bradley Run to the north. Seeps existing at the Staple Bend Tunnel Unit are fed from collapsed mines and have high metals content, resulting in the formation of iron mounds on park property.