Unfortunately, Lake Lehman no longer exists. Owned by PH Glatfelter Co., the lake was drained, and the dam dismantled. The company is currently returning the site to its natural conditions prior to dam construction and is exploring the possibility of turning it over to the local municipality for use as a park. Says Ben Zimmerman
There's a good 2-mile-long class II-III whitewater section on Gunpowder Falls nearby, the Graves Run Road to Prettyboy Reservoir
portion. When the conditions are right this section of Gunpowder Falls is a fun section of river for whitewater kayaking or rafting.