You are describing a Bury Hydrant.
Put one wrench on the vertical galvanized pipe and one on the handle attachment that threads onto galvanized pipe.
When your removing this, once it unscrews, there will be a long rod attached to the handle.
At the bottom of this rod, there will be a replaceable washer or leather that needs replaced to stop the leaks.
All depends on the age of the bury hydrant.
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