Granite Falls takes the mountain rain and sits on ground that falls away toward the river and the falls. Steep sides of lots are normal. Water concentrates, finds the weak spot in a bank, and leaves a rill where the lawn used to be. 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 98252 · 2020 population 3,572
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 Granite Falls
Properties on the edge of town back into fir and alder. The lawn, if there is one, is a cleared bench. The rest is slope, stump, and shade. We get called when a bank has started to slump after a wet winter, or when a path down to the lower yard has turned into a creek.
Rock walls and a drain at the top of the slope do more than plants will. Beauty bark in the deep shade keeps the weeds down and the mud off the house, but it will not hold a bank by itself. Tree work is practical: limbs over the roof, and sightlines where the forest is closing the drive. Aerator and seed belong on the flat piece only. Treating the whole hillside like a turf job is how you waste a season.
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
What the trench looks like
Fabric, washed rock, pipe with the holes oriented the way the detail calls for, then rock, then fabric closed, then soil. The lawn or the bark goes back on top. A trench of pit-run gravel with a pipe tossed in will silt up, and we do not build those.
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.
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.
More from this crew
- French drain installation across Snohomish County
- Retaining walls in Granite Falls
- Gravel installation in Granite Falls
- Landscaping in Granite Falls
- Patio installation in Granite Falls
- French drain installation in Arlington
- French drain installation in Lake Stevens
- French drain installation in Marysville
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.
