11-02-2018, 02:11 PM
(11-02-2018, 02:02 PM)tomh009 Wrote:(11-01-2018, 01:21 PM)danbrotherston Wrote: For either a french drain, or a ditch, there must be some "away" for the water to go. The ground is saturated, it cannot absorb more, so the water will pond.
A french drain can be combined with a drywell, which can provide substantial dispersal and holding capacity, but that takes more space. It can also be connected to existing storm drain systems, but simply digging a trench or french drain will only provide so much extra capacity as dirt is removed.
When you're looking at houses, you're generally simply wanting to move water away from your house, and usually theres' yard space to move it too. I'm not sure how much the right of way extends beyond the trail, but it's a hill on both sides, there isn't a lot of room to store water. Certainly elements like these could have been included, for example, a well designed dry well under the trail probably would provide a lot of capacity to solve this problem, but I don't think it's an easy or cheap fix now.
On the other hand, raising the level of the asphalt by adding another layer would help by raising the level of the path above the water, not require storage for the water. It could still overflow the path, but it would take more water.
There is substantial forest/bush next to trail. Is it higher or lower elevation than the trail? If lower, using a ditch can simply allow the water to drain to the lower elevation. If it's not lower, the French drain will still allow much more water to collect in it without pooling on the trail.
Based on the city's comment, there is lower ground and regrading next to the trail will allow the water to flow away from the trail, achieving the same function as a ditch.
I believe the trail is in a depression where the railway would have been, but I'm not intimately familiar with all the typography, at some point, it transitions to lower on one side, and I'm not sure where that is, how how much of a grade would be needed to reach it.