Hello! My name is Alex Keim, a PhD candidate in Historical Archaeology at Boston University, and I am hoping someone can help me identify a architectural feature I encountered while doing a on-site consultation in Lynn, MA. A link to photos is at the bottom of this message. The feature is located in the rear lot of a townhouse constructed in 1871. The feature in question is the remainder of a previously partially demolished brick dome or vault, about 1 meter below current surface level. Based on photographs (see link) of a very similar feature uncovered by construction crews about 30 meters away (but reburied before I could see it firsthand) I believe the feature was originally a dome with a circular opening at the top. This intact feature also had metal piping entering the dome near the base, but the partial feature I encountered had no surviving piping. The dome is roughly a meter from top to base, and the intact portion I saw was about 2 meters in diameter. The feature is constructed of bricks and mortar. It is set on a large circular pit, full of cobble sized rubble and rip-rap. I partially excavated the soil fill above the rubble and determined that it dates to after the feature's demolition, and I removed a portion of the rubble fill to try to determine the depth of the hole, but I encountered no sign of a bottom after 70 cm.
    I am thinking that this is some kind of dry well, or possibly a cesspool (but there were no cessy conditions or residue on the interior), but I have never dug something like this before and would welcome confirmation or other interpretations. If anyone has encountered a similar feature I would greatly appreciate some feedback. Following is a link to a webpage that should give you access to some photographs of the intact feature I did not see firsthand, and the partial feature I worked on. Thanks for your time!

Sincerely,
  Alex

http://img72.imageshack.us/i/intactbrickvaultfeature.jpg/
http://img512.imageshack.us/i/afterpartialremovalofru.jpg/
http://img204.imageshack.us/i/detailoffillremoval.jpg/
http://img217.imageshack.us/i/featureafterexcavationb.jpg/
http://img594.imageshack.us/i/featureafterexcavationb.jpg/
http://img143.imageshack.us/i/featureafterexcavationb.jpg/
http://img138.imageshack.us/i/intactbrickvaultfeature.jpg/