Viewing a single comment thread. View all comments

LilGeographersRoom OP t1_j29co4d wrote

Reply to comment by TorontoNeverSkeets in Mystery WMATA/Metro survey markers: Can any intrepid city planners or engineers explain what these discs are (or were) used for? I seem them all over the place, even sometimes away from Metro stops. by LilGeographersRoom

Is there a reason these are branded with Metro specifically?

4

the_real_dmac t1_j2a744q wrote

Much of the metro’s miles of tunnels were constructed using cut & cover, digging down from the surface, pouring concrete and laying steel, then covering it back up. (Not the deep stations along the redline, those were bored into bedrock). Disrupt that much soil and there will be compaction that occurs years later, and that can damage infrastructure built above. So metro monitors surface elevations around tunnels for that problem.

36

LilGeographersRoom OP t1_j2du9gv wrote

Does Metro maintain these discs alone, or do they keep their measures in tangent with USGS?

1

TorontoNeverSkeets t1_j29p2l1 wrote

My guess is because they’re for doing monitoring on/around wmata property. Probably used for some combination for new construction and or vibration/settlement monitoring.

16

aegrotatio t1_j2a84v7 wrote

Even when very far away from Metro entrances on the surface you are still standing above or near a station, tunnel, or other Metro structure. Metro stations are massive.

13