A dry basement is a wonderful thing. And my partner Tom Whitmore and I enjoyed one beneath our house in Ballard for more than 20 years.
Then came the dreadful night last January, when I went downstairs to the basement and found myself ankle-deep in water.
Since we’d never had water issues in our basement before, I jumped to the erroneous conclusion that our hot water heater must have ruptured. I grabbed mops and a dozen old beach towels and started trying to soak it up. But the water just kept coming — far more than could be accounted for by a hot water heater. Plus — and I should have noticed this — the water was very cold.
When the initial panic subsided and Tom and I were able to get a better look at things, we realized the water was coming up like a small fountain through a seam in the concrete slab beneath our 90-year-old house. Our gutters were working properly, and the foundation walls were fairly dry. But, thanks to the cracked slab, the floor was a shallow lake.
Seattle’s challenges with groundwater
Brian Sleight, a supervising engineer with the Water and Land Resources Division for King County, gave a grim chuckle when I told him my story. Our basement flooded during a month when the Puget Sound region’s precipitation dramatically exceeded the average for a January.
“We had people calling and saying, ‘I have water where I’ve never seen it before!’ ” he said. “When a storm fills the groundwater up, and then there’s another big storm on top of that, that’s when we see a lot of problems.”
Sleight said that in most areas in and around Seattle, a relatively shallow layer of permeable soil sits atop a dense layer of “glacial till’’— soil that was packed hard beneath glaciers as they advanced and retreated some 15,000 to 17,000 years ago.
“[The soil] we have in King County is close to being impervious,” Sleight said. “So when water gets down there, it travels horizontally. It might come out as a spring, it might recharge a stream or it might come up in a building. If there are any seams or cracks creating a place where water can seep through, it will.”
Sleight likens it to a layer cake: “You have a nice spongy cake — liquid will soak a layer of cake, but when it hits the frosting layer, it starts coming out the side of the cake.”
Like me, you can go for years without realizing you have a potential problem. But all it takes is a period of extreme rainfall that soaks the ground, and any excess water has nowhere to go but into your basement.
When you are in the midst of a flooding situation caused by extreme weather, you probably aren’t alone. Enter into just about any neighborhood social media forum and you’ll hear from plenty of other homeowners who are bailing and mopping and spending hours on hold with their plumber, just like you.
During the wettest parts of the year, plumbers are booked solid. And if your flooding problem involves groundwater, like mine did, a plumber will likely need to refer you to a drainage specialist. This spring, drainage pros were booking work two to three months out.
“We encountered many groundwater issues this year,” said Paul Korenovsky, owner of Everett-based Allied Waterproofing & Drainage. He advises homeowners awaiting help from a plumber or drainage company to use a wet vac to remove water that’s coming through the foundation walls or slab.
Keeping your basement dry
Once the initial flooding is under control, there are a variety of long-term solutions for basement groundwater problems. Korenovsky said the best method depends on your particular situation.
If water is coming in through the walls of the foundation, a good solution is installing French drains around the perimeter of the house. This involves digging down to slab level, installing large PVC pipes with holes to admit groundwater, filling the trenches with gravel and connecting the pipes to the property’s stormwater drainage system.
“These days, when they build new houses, they put in those perforated pipes for drainage,” Korenovsky said. “But if you have an old house, there may never have been drains, or the old clay pipes may be broken.”
Installing an exterior drainage system can, however, be time-consuming and costly. If you have a patio, walkways, decks or trees close to your house, those may have to be removed and replaced.
A less expensive — and less invasive — solution is putting a French drain and sump pump inside the basement. When the sump (cavity) fills with water, a sensor triggers the electric pump to channel water into the household sewer system.
Rolf Petersen, one of my neighbors in Ballard, chose this solution several years ago. “In 2009, we had a big snowstorm, and the next day it was 60 degrees and suddenly we had water everywhere,” he recalled. “I pumped out 60 gallons of water in 12 hours.”
Petersen opted for an interior French drain and sump pump, along with the addition of plastic sheathing along the walls of his foundation. “It was the right decision,” he said. “Ever since then, we’ve been dry.”
An interior drain solution is also appealing if you have an unfinished basement that allows direct access to the concrete slab. This was the case for Petersen, and for our house, as well.
Our project took just over two days to complete. On the first day, the drainage team broke up the slab, dug the trench and ran the PVC pipe. On the second day, they installed the sump pump, connected it to the sewer system, tested the pump, filled the trench with gravel and poured the concrete. On the third day, an electrician came and installed a dedicated 20-amp circuit for the sump pump.
Why a dedicated circuit? Jeff Bartz, president of Bellevue Electric, explained: “If you have another appliance sharing the outlet, it could trip the circuit and shut off the breaker. If that happened, your sump pump wouldn’t pump if it filled up with water.”
I shuddered at the thought. It may be a few years before we have another set of back-to-back storms, but when we do, I don’t want to be down in a chilly basement with a mop and towels.