These trails are getting to be more and more popular. The trail network is extremely tight and twisty though it lets you loose for the occasional but short fast sections.
While named Lake Sawyer, you can't actually get to Lake Sawyer. the trails that lead to that section are posted no trespassing. But no worries as there are plenty trails in the open area (East of the old railroad).
How to get there:
From Renton take HWY 169 (The Maple Vallye Highway) East towards Black Diamond. After passing through Four Corners look for some power lines. Pass under thoses and then start looking for pull outs to the right. There are several options. You can also turn right onto 288th and park in the small area directly to the left.