You may well be right, however what I have been getting around to saying politely which didn't work, is simply this (impolitely).
If you don't know what you are looking at you are bleedin' clueless with respect to implications. A cover in a road may lead to a sewer it may not, it may lead to a telecoms duct or merely be a rodding eye for a pipeline. If, in the absence of a drawing that tells you the full SP on what it is, you haven't lifted the cover and had a bleedin' good look you are merely guessing like a lot of stuff on here.
Agreed.
I can tell by the cover on the ground whether it is rainwater (aka agua or pluvias), whether it is a sewer (aka esgotas) or whether it is a telecoms manhole (labelled with the name of the telecoms company e.g. CTT). Telecoms holes are normally roughly half the size of the other two. Sewers don't need to be large, 'cos Luz is not large.
The biggest pipes seem to be storm drainage. For 9 or 10 months of the year it is bone-dry here with zero rainfall. For a month or two it throws it down like we live with tropical monsoons.
The 2007 works were 90cm wide, which suggests a pipe size of around 75cm, which in English is 30 inches or 2.5 feet. Enough to get a Maddie-sized child down with room to spare.
I saw works in Gaivota (west of Luz) in 2012, where the storm drains being put in looked around 1.5m diameter. That's enough to stuff a large adult into the pipe.
The problem with the manhole covers in Luz is this. I would guestimate that every 25 to 30m you get a pair of covers, one for rainwater, one for sewage, normally side by side. If I had to guestimate how many such covers there are in Luz, I would put it at high hundreds to several thousand.
Whatever the number is, if I go around pulling all the covers up, I am in danger of 2 things. 1) Getting charged with investigating a crime. 2) Getting run over by traffic. Plus, I have no capability to examine the pipes, only the manholes.
Over to Scotland Yard!