The Little Pour

Last September I posted an entry about patching my driveway called The Big Pour. By the amount of cement used, yesterday’s pour was nowhere near as big a job. But the patch covers a far more serious problem (see photo)—one that I hope went away as mysteriously as it appeared.

I first noticed evidence of a sinkhole in the flat lower area of my driveway last winter. It showed up as a circular-shaped depression in the asphalt about the size of a large wok. I ignored it until last June when a couple of ominous cracks appeared (see photo below). The cause of the cracks was obvious as soon as I broke through the asphalt—about a half-yard of the dirt fill under the driveway had vanished!

No one I talked to, including my neighbor or the former owner of my house, had a good idea what caused the sinkhole. We looked for water-line leaks and for evidence of washed-out fill dirt along the rock wall at the edge of the driveway. When neither check yielded a clue, their theory was that a large stump had slowly decayed causing the dirt around it to collapse. Maybe. A half-yard is a lot of volume to just disappear, although the asphalt could have been stoically hiding the problems underneath for years.

Online I read up on sinkholes. Scary stuff. With vast amounts of porous limestone interacting with flowing groundwater, Florida seems to have the worst. There are stories about sinkholes swallowing cars and swimming pools and threatening roads and buildings. On some web sites, people post details about their sinkholes, seeking sympathy, explanations, and solutions. While my sinkhole is worth an entry in my own blog, that’s as far as I plan to go with it. It didn’t actually swallow anything man-made unless you count the money I’m out for gravel and cement.

My neighbor advised me to leave the sinkhole open during the summer to see if it would continue to grow. Summers are dry in Western Washington so the issue of rainwater entering the hole was minimal. I filled the sinkhole to within an inch or two of the top with black gravel, marked the area with an orange traffic cone, and waited. Nothing happened. The level of the gravel didn’t change. Last Monday’s all-day rain was a reminder that with fall here it was time to act. That’s unless I want driveway runoff to aid whatever sinkhole-causing forces might remain.

After yesterday’s little pour, the sinkhole is now sealed from the top. I’m hoping for the best.