South King County
Landscaping & Hardscaping in Covington, WA
Quick answer
Covington sits on a glacial till plateau around 400 feet, so hardpan and standing winter water drive nearly every project here. We build drainage-first paver patios, retaining walls, fences and sprinkler systems, about twelve minutes out Kent-Kangley Road from our Kent shop. Backflow assemblies are required by Covington Water District.
- From our Kent shop
- about 12 minutes
- ZIP codes served
- 98042
- Licensed in WA
- Bonded & insured
Covington only became a city in 1997. The neighborhoods are older than that. Most of what we work on was platted while this was still unincorporated King County, through the 1980s and into the 90s. Generous lots by South King County standards, wide streets, cul-de-sacs. Back yards big enough that people here actually use them. Timberlane is the classic example. Big flat parcels, mature Douglas fir and western red cedar left standing between the houses, and thirty-year-old landscaping that has reached the end of its life all at once.
The plateau runs around 400 to 500 feet of elevation. That's high enough to change the weather. Covington is measurably wetter than the Green River valley a few miles west. We're at the front edge of the Cascade foothill gradient that keeps climbing toward Maple Valley and Black Diamond. More rain, landing on ground that won't take it. That's the whole story of landscaping here.
Underneath is till. Dig anywhere in Covington and you go through a foot or two of soil, then hit a cemented hardpan that a shovel rings off. Water doesn't get through it. It perches on top and moves sideways. That's why the Covington complaint sounds the same from house to house. The back lawn is a sponge from November to March. The dog tracks mud through the kitchen. The swing set sits in a puddle. Somebody put in a French drain in 2014 and it did nothing, because it discharged into ground just as saturated as the ground it drained. The gravel operations along Kent-Kangley and SR 18 are working outwash sand and gravel that runs in bands through this same landscape. So what's under any given Covington lot can go from free-draining gravel to concrete-hard till inside one property line.
So we design the drainage first and the pretty part second. A Covington patio base gets built with a route for the perched water, not a dam across the slope. Finish grade is set with fall to a real outlet. Catch basins go where the water already collects. Tidy on a plan doesn't matter. Fence posts often need an auger with real torque, or a hand-jack, to get through the hardpan. A post hole that fills with water overnight gets drain rock in the bottom, not a bag of dry mix dumped in a puddle. And sod laid over unamended till will fail its first winter. Subgrade prep and compost tilled into the top layer is why the lawn survives.
For planting we use what thrives on this plateau. Sword fern, salal and evergreen huckleberry under the conifers the builder left. Kinnikinnick and hebe on the gravelly, sunnier sections. Red twig dogwood and carex in the low corner that will never be truly dry. Vine maple and rhododendron where a yard needs some height. Covington is twelve minutes out Kent-Kangley Road from the shop. A spring irrigation start-up or a fall blowout is a routine stop for us, not a special trip.
Ground conditions in Covington
Covington sits on the glacial till plateau east of the Green River valley at roughly 400 to 500 feet. The dominant soil is Alderwood gravelly sandy loam over dense, nearly impermeable Vashon till. Hardpan usually shows up between 12 and 30 inches. Some parts of the city are on recessional outwash instead, coarse sand and gravel that drains freely, and the boundary between the two can run straight through a single lot. What you get is perched groundwater. Winter rain saturates the shallow soil, then travels sideways on top of the hardpan until something intercepts it. Annual rainfall here is meaningfully higher than in Kent or Auburn, because Covington sits at the start of the foothill gradient. Jenkins Creek, Little Soos Creek and Big Soos Creek drain the area. Wetlands are common in the low ground between plats.
Permits
The City of Covington handles its own permitting from City Hall on SE 271st Street. Its surface water design manual is based on the King County standard. A retaining wall over 4 feet from the bottom of the footing to the top needs a permit and stamped engineering. Tiered walls, or walls carrying a surcharge, can get reviewed together as one taller structure instead of separate short ones. Covington drains to Jenkins Creek and the Soos Creek system, so stream and wetland buffers are a live issue on a surprising number of lots. Buffers on fish-bearing streams here are wide. Clearing and grading volume triggers its own review. So does new plus replaced impervious surface past the drainage review threshold. Either one can catch a large patio or a paver driveway with no wall involved. Standard residential fences within the height limits generally don't need a permit. Covington updates its adopted manuals periodically, so we verify current thresholds with the city at permit time.
Neighborhoods we work in
- Timberlane
- Jenkins Creek
- Pipe Lake
- Lake Lucerne
- Soos Creek
- Covington Town Center
- Kentwood area
Services we offer in Covington
Most requested in Covington
Covington: common questions
Why does my Covington yard hold water every winter?
Hardpan. The glacial till under most of the city is close to impermeable. Once the shallow soil above it saturates, everything that falls after that perches on the layer and runs sideways until it finds a low spot. Adding topsoil won't fix it. Neither will aerating. Water has to go somewhere, so it needs a graded collection point and a solid line to a place it can legally discharge.
What does yard drainage typically cost around here?
A residential catch basin network with a solid tightline running to a legal outlet usually runs roughly $2,500 to $7,500 installed in the Puget Sound market. What moves that number is run length, depth through hardpan, and how far away the discharge point is. Treat it as a typical market range for planning. It isn't a quote. We walk the site to get you a real number.
Do I need a permit for a retaining wall in Covington?
Over 4 feet from the bottom of the footing to the top, yes, with stamped engineering. Under that with no surcharge, usually not. Two things catch people out here. Tiered walls can be evaluated as one taller wall. And a lot backing onto Jenkins Creek or Soos Creek may have a stream buffer that restricts where you can build at all. We check both before pricing.
Who handles backflow testing on a Covington sprinkler system?
Covington Water District serves most of the city. They require an approved backflow assembly on an irrigation connection, tested every year by a certified tester, with the results reported to the district. We install the assembly to district requirements and get the initial test done. Then we hand you the paperwork, so the annual notice doesn't catch you off guard.
Can you set fence posts in Covington hardpan?
Yes. It's slower than a valley job and we price it that way. Till this dense usually needs a rock auger or hand work to reach depth. A hole that fills overnight gets drain rock at the bottom, so the post base isn't standing in water four months a year. Skip that step and the post rots at the ground line. That's what happened to a lot of the thirty-year-old fences around here.