River running under our houses?

[gburke]

A while ago, I was able to input my exact address (but results were given by a bit broader range) on the USGS website and it would tell me the location of all of the underground rivers. I can’t find this anymore. Any remember how to get to it? Thanks!

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[metrognome]

is this what you’re looking for? if you click on the map icon on the left, you can enter an address. http://waterdata.usgs.gov/nwis

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[gburke]

Hmmmm…maybe, not sure though. It doesn’t look like that is showing any underground springs or streams in our area. Is that real?

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[JayDee]

@gburke:

I hope I can answer your question without literally muddying the waters. Underground, in the geology we have around here, water (or groundwater) exists in the pores or spaces between grains of sand or silt. Think of a swimming pool filled with sand, which is only half-filled with water. The level the water comes up to is the water table. This is the situation for much of West Seattle. The sand is called the Esperance Sand and the bottom of the pool is the underlying clay, the Lawton clay. The surface of the clay is not even, so water pools on-top of it.

So rather than a river, most of our houses sit on-top of a pool of groundwater. At the edges of the pool, where the topography sinks down and encounters the water table and the edge of the pool, groundwater discharges to springs and those give us the surface water creeks like Longfellow Creek and Schmitz Park Creek. Similar springs often discharge to curbs, or to storm drains where it sounds like a creek runs even in summer. Other sand/silt layers in the area behave in the same way.

Actual underground rivers are very uncommon in general but occur in Kentucky, Eastern WA, or other areas where actual limestone, fractured bedrock, or lava flows and lava tubes channel groundwater like a pipe and as such could resemble a river. While it would be cool to have such a underground river here we have no such luck. But on the other hand, you could use that pool of groundwater to both heat and cool your house, but it would involve drilling wells. And that gets expensive.

Parts of West Seattle (Pigeon Point, Delridge) have a three layer geology. The Vashon Till over the Esperance Sand, over the Lawton Clay. The Till is a combination of gravel/sand/silt and clay and it is very tough to dig into–if you have it, you know it. Bad for drainage and water in the crawlspace. I simplify things a bit. Plus we all live in a fault zone.

<http://green2.kingcounty.gov/groundwater/map.aspx&gt; shows boring logs in the area with the very approximate geology and where groundwater occurs in your area.

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