I assume it must be draining to somewhere, but don't know where or why. It is under a brick patio and concrete driveway, and in a bad place for excavation.

The house was built in 1911 so I suppose this could be an oil tank or something like that. I wonder if it also has some potential for a sewer line leak, though it doesn't seem to be in the right position and the sewer line is very shallow at this point.

Can it be filled with gravel and sealed? Do you have any other suggestions?

A: A number of possibilities come up, including the following scenarios:

1. Old fuel oil tank - if this is the case it will need to be destroyed under permit from Sacramento County Hazardous Materials Division. (875-8550)
2. Old cess pool or septic tank - If this is the case, it will need to be abandoned under permit from Building Inspection or Sacramento County Environmental Health. (875-8440)
3. Old water well - If this is the case, it must be destroyed under permit from Sacramento County Environmental Health. (875-8440)
4. None of the above or possible surface drainage - If it is none of the above, fill it with sand, gravel or concrete to the point where it is not a trip or injury hazard.

At a minimum, it should be examined to confirm that it is not a large cavity with the potential for cave-in.

A licensed plumbing contractor can help you determine whether you can just fill it in with sand, or if it's a more serious problem. Then you will have the information you need to decide whether you can tackle the problem yourself, including getting the necessary permits, or if you would prefer to hire some professional help.

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