Index is a town of 153 people in the Skykomish valley, tucked under steep, rocky walls. Rain comes down those walls in a hurry. Yards are small clearings, and the mountain is the neighbor on every side. On a hillside the drain belongs above the lawn and above the wall, where the water is still concentrated. A drain at the bottom is a mop.
Snohomish County · ZIP 98256 · 2020 population 153
Intercept the water at the top of the slope
We cut a line across the slope, deep enough to catch the seep, and we outlet it to the side, not down the middle of the yard. The pipe has to be protected from the rock and the fill that move every winter. Cleanouts go in where a mountain silt load will eventually arrive.
A French drain is not a retaining wall. If the bank is moving, the wall comes first or with it. Pipe alone in a slumping cut just becomes a crushed pipe.
The ground in Index
There is no subdivision playbook here. Access can be a single lane, the soil is thin over rock, and a “backyard” may be forty feet of level ground before the timber starts. Intense runoff is the design constraint. A wall has to be heavy enough to stay put, and a drain has to daylight somewhere that does not wash out the next switchback.
We keep planting short and native. Anything that needs summer water and a gardener will lose. Gravel and hardscape earn their place because they stay usable when the ground is soaked. Pruning and cleanup are how you keep the forest from taking the roof, the line of sight on the drive, and the ditch that is supposed to carry the runoff.
How we do the work
A French drain is a perforated pipe in washed rock, wrapped so the fines do not fill it, sloped to a place the water can actually leave. We do not end a drain in a dry well of hope, and we do not outlet it at the neighbor’s shed.
The trench is deep enough to catch the water you are chasing, which is often the downspout and the wet line along the foundation, not a decorative strip in the middle of the lawn. Surface grading still matters. A drain cannot fix a patio that pitches at the house.
What we look at first
- Where the water shows up, and where it can daylight
- Downspouts that are dumping at the footing
- Utilities before we trench
- Whether the wet spot is a seep that will need more than one line
Maintenance
Silt arrives. Cleanouts and a flush every few years keep the pipe a pipe. Catch basins, if we used one, need the leaves emptied. A drain with no access becomes a dig when it clogs, so we put the access in.
Cost follows the outlet
A short line with an easy daylight is a different job from a line that has to cross a drive, miss a gas service, and reach a ditch fifty feet away. We price it after we see the outlet. We do not quote a per-foot number from the curb.
Downspouts
Solid pipe until it is away from the house, then into the drain if the drain can take the roof. We do not dump a whole roof into a two-inch pop-up in the middle of the lawn and call it drainage.
More from this crew
- French drain installation across Snohomish County
- Retaining walls in Index
- Gravel installation in Index
- Landscaping in Index
- Patio installation in Index
- French drain installation in Gold Bar
- French drain installation in Sultan
Sources for the climate and the water
- USDA plant hardiness map for choosing plants that can take a Snohomish County winter.
- EPA WaterSense on watering less once a lawn or a new planting is established.
- EPA Soak Up the Rain on keeping roof and yard water from becoming someone else’s problem.
