an atlbike.org weblog

It’s been a lot of work getting to this point.  I was ready to set the french drains into place for the grate at the east entrance of the Brushy Mtn Tunnel. To keep the gravel and french drain from clogging with mud and silt I engineered a two stage filter and 3″ over-flow pipe.
In the photo below you can see the open cell foam block which will act as the first filter. I fabricated a filter wall to allow water flow into the gravel and 20 ft of manufactured french drain. I also removed the mud from the legacy drain pipe and plugged it with filter foam to hold back the gravel. The wall is a three layer assembly of filter fabric, garden fence (for strength) and 1/2″ plastic mesh to retain the drain gravel. A short piece of 3″ pipe was inserted as a place holder and later replaced with the actual over-flow pipe. (click images to enlarge)

Filter "wall" installed

There was still much digging of muck and contouring the trench in preparation of placing the 20 ft of drain line.  Much of the material still in the trench needed to be removed.  You can see the two 10 ft segments of drain line.

French Drain and Trench

After the trench was preped, the drains were assembled and placed in the trench.  The trench was filled with gravel to the level of the over-flow.  The 3″ over-flow PVC line was assembled and laid after this (not in photo).  The first portion of the trench was then back-filled with gravel.

Drain with gravel fill.

It was getting late and I didn’t have time for photos.   The drain area was back-filled with gravel to the top of the grate and gravel was spread the length of the drain pipe.   The gravel and drains were then covered with silt fence fabric to prevent mud from fouling the works.

We rode up on Tuesday and I’m pleased to report that everything functioned perfectly in the torrential rains of the previous night.

Drain section w/ over-flow pipe

Much work to be done; need to get the lines buried.   Hoping Tony can help this weekend…

3" over-flow pipe