Hate to answer my own question! Guess I should have read Petrie first.

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Petrie
Soon after passing this granite, we got into the lower part of the entrance passage, which was clear nearly to the bottom. Here a quantity of mud had been washed in by the rains, from the decayed limestone of the outside of the Pyramid, thus filling the last 30 feet of the slope. This was dug out and spread narrow passage; no truck arrangement could be easily worked, owing to the granite block lying in the passage. Work down at the bottom, with two lanterns and six men, in the narrow airless passage, was not pleasant; and my visits were only twice a day, until they cut through to the chamber. Here I had the rest of the earth piled up, clear of the walls, and also of the well, and so re-established access to these lower parts.

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So I read that there was 30 feet of mud at the bottom of the DP but Petrie had it cleared. I don’t see any reason to interpret that he did not have it cleared enough to get a measurement.

What am I missing?

RLH