Mountlake Terrace is mid-century houses on city lots, with newer buildings near the transit line. The slopes are gentle, the soils are compacted, and the yards were not designed for the amount of roof water a remodels-worth of downspouts can dump. City water problems are usually a roof pointed at a foundation in a yard with no slope. The drain has to reach a legal outlet, often the street or a connection we confirm first.
Snohomish County · ZIP 98043 · 2020 population 21,272
Downspouts, tight side yards, and the street
Side yards are narrow. We dig by hand when a machine will not fit, and we still slope the pipe. A level trench in a side yard is a storage tank against the house.
We check whether the city allows a curb outlet before we promise one. Some streets do, some want a permit, some are a hard no. The estimate says which. Tie-ins to an old clay footing drain get a camera or a test, not a guess, because those pipes are often already full of roots.
The ground in Mountlake Terrace
Lots are modest. A patio, a small lawn, a side yard that has become a moss strip, and a fence that is older than the owners. That is the usual visit. The soil has been walked on for sixty years. Aeration and dethatching change the lawn more than a bag of seed thrown on top.
Where the lot tips, it tips a little, and a low wall or a re-graded swale is enough. We are not cutting roads into a mountain. Pavers get people off the mud by the back door, and a pressure wash takes the black film off a walk that has not seen sun all winter. Plantings should stay in scale with the house. A hedgerow that needs a lift every year is the wrong tree for a forty-foot lot.
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.
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.
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 Mountlake Terrace
- Gravel installation in Mountlake Terrace
- Landscaping in Mountlake Terrace
- Patio installation in Mountlake Terrace
- French drain installation in Lynnwood
- French drain installation in Edmonds
- French drain installation in Brier
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.
