San Francisco’s Favorite Outdoor Volunteer Program
Re-designing and applying the top layer of trail is a great way to mitigate pooling and encourage draining - but it wont work everywhere. For areas that see a lot of water all at once (think of a trail with steep, rocky up-slopes), drains are the way to go.
On March 28th I, along with Gered Doherty and Pieter Buysschaert (neither of whom had any idea what they were getting themselves into), hiked up the Upper Historic Trail to put in a trench drain. The drain is ten inches deep and eight inches wide with a half-inch layer of sand on the bottom to buffer the organic material. On top of the sand we put a two-inch layer of gravel and two layers of larger rocks. But you’d never know it to look at it. All you can see from the trail is our top layer of gravel and the log we used to create a gutter effect. Also un-seeable to the passer-by is the off-drain that carries the water from the drain across the trail and down hill. This little drain is packed with gravel to help filter the water as it passes though. We finished the top layer on our April 4th volunteer day and the drain and trail have been fairing well since.
Then, we filled it with sand, gravel, and rock.
(That's Gered moving rock, photo taken by Pieter)
Putting in the final layer of gravel.
The finished drain!