Sammamish sits on a plateau above Lake Sammamish, and most of it was built out as subdivisions in the last thirty years. Under a thin layer of topsoil is glacial till, a hardpan that water barely soaks into, and many lots back onto tall stands of Douglas fir. A soggy bed under firs may be canopy drip and poor surface grade, not a spring. We do not trench through a root plate to solve a grading problem.
King County · ZIP 98074
Wet shade is often surface water plus a tree
We watch a rain before we cut roots. If the water is sheeting from a patio or a downspout, we catch it uphill of the tree and move it. If the soil is wet because it never sees sun, a drain helps only when there is an outlet. Otherwise we change the planting and the grade.
Roots in the trench get cut clean if they must, and we do not promise a tree will not notice a line dug through half its roots. Sometimes the line moves.
The ground in Sammamish
The till is the reason so many yards here stay soggy in winter and dry out fast in summer. Water sits on top of the hardpan, so a new lawn or patio needs drainage planned in from the start. We put in French drains, grade the yard away from the house, and build patio bases deep enough that they do not heave.
Many neighborhoods have HOA rules for fences, front yards, and plant choices, and we work to those standards. Lots along the greenbelts get heavy shade and needle drop, so we use shade-tolerant planting and bark where grass has given up. Larger backyards here are a good fit for a full redesign: a paver patio, a low retaining wall to level the slope, and irrigation on a timer for the dry months.
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.
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 the region
- Retaining walls in Sammamish
- Gravel installation in Sammamish
- Landscaping in Sammamish
- Patio installation in Sammamish
- French drain installation in Mercer Island
Sources for the climate and the water
- USDA plant hardiness map for choosing plants that can take a King 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.
