PORTLAND A Southeast Portland homeowner was shocked to find a 20-foot deep sinkhole in his backyard, following heavy rain this week.

Justin Nguyen doesn t know if it s safe to spend time in his home anymore, worried that the sinkhole could grow even bigger.

It might spread wider. If you add more weight to edge of the sinkhole, it could fall down there, he said, pointing to the edge of the deep hole.

Firefighters visited Nguyen s home Wednesday and checked the sinkhole. But all they could do to help was surround it with yellow caution tape.

Right now, we don't know what do, Nguyen said. We re still doing research and trying to find a company that repairs it. We don't know what to do.

The sinkhole is not very wide, but quite deep. Thankfully, it was discovered before anyone fell into it.

That was not the case at another home in Southeast Portland on Tuesday. A woman and her dog fell into a sinkhole in the backyard of a home on Southeast 38th Avenue.

More: Woman falls into sinkhole

The woman was rescued by firefighters after a passerby heard her cries for help and called 911. The dog was also found and safely lifted out of the hole.

It was later determined that the sinkhole had formed after a sewer cesspool collapsed underground.

There are thousands of these cesspools in the Portland Metro area, explained Mike Runyan with Environmental Works. He helps find and decommission old cesspools.

More: How to find cesspools

Runyan said dangerous cesspools are most often found at homes built before the 1930s. His company uses high-tech equipment to locate sinkholes which pose the most risk, because they have not been properly filled.

He said concerned homeowners can also find more information through city resources, including the Portland maps website.

You can click on the historic permit tab on their website in order to pull records that show drawings where a cesspool potentially is located, he said.

The cost of decommissioning an old cesspool can run around $1700. As for Nguyen, he has no idea what it will cost, but he s determined to find a way to make sure all signs of the gaping sinkhole in his yard are gone.

We can't leave it any longer, he said.

In the meantime, Nguyen said he ll move out of the house until he s sure it s safe.

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