Long time residents of Black Diamond, Judy and I love our community and the unique natural beauty and colorful history we have here. Join us in learning more about our history, local wildlife, must do hikes, conservation areas to explore and the opportunities and challenges faced by our community. Craig Goodwin

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Bill Kombol

Horseshoe Lake is essentially a water-table lake whose level generally reflects groundwater. A couple of factors contributed to the flooding. Interesting, the lake was often full of water in the summer and dry in the winter, a counter-intuitive fact that landed Horseshoe Lake into the Ripley's Believe It Or Not, newspaper column with a cartoon-like depiction of the lake and the above fact. Sadly, though I once held that column in my hand, I can no longer find it. Back in the 1960s or 1970s, the owners tried to seal the bottom of the lake in order to create a year-round lake which previously was either filled with water or bone-dry. Bulldozers plowed the silty soils which lined the bottom of the lake, but little was created but a small pond where groundwater could no longer freely infiltrate as it had done for centuries. Despite the attempt to seal the bottom, there was no possibility of preventing rising groundwater from filling this low area as it always had. The next, and biggest problem, was that those who built homes ignored the fact that during certain years of exceptionally high groundwater, the lake was higher than usual. The clue, which still exists along northeast corner of the lake, was Douglas fir trees. Douglas fir is a specie which can not tolerate flooding, or what is called "wet feet." Many species such as spruce, cedar, and cottonwood can tolerate periods of inundation, but Douglas fir can't. If those who were building homes had examined the lowest topographic level at which mature Douglas fir trees survived, they would have known that would be the lowest level that anyone would want to build a home. Anything topographically lower would be subject to flooding in years of high groundwater. This was a fact well-known to old-timers who had lived in and around the Black Diamond area for decades. But, this critical institutional knowledge was not tapped resulting in a situation where King County issued building permits, homeowners built lake front homes, and several years later fingers were pointed everywhere except the mirror.


I hadn't noticed it when commented in 2016, but one thing stands out in the 1936 aerial photo. Surrounding the portion of Horseshoe Lake that was inundated the day this photo was taken, is a large area of grassy lands where no trees grow. That grassy area reflects the high water table level when the lake was completely full.

Pete Butkus

I remember in the late 80’s King County was considering applying to the State Public Works Board (I was the Executive Director then) to do a surface dig that would permit gravity drainage of the lake in high water events. An alternative was to construct a permanent pumping station.

The issue became moot because key property owners would not permit use of their lands to construct one or the other solution. The County did not want to go through a condemnation process so the whole idea of a permanent solution died.


Craig Goodwin

Thanks Bill and Pete for your historical insight.

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