Help with advising on old septic system design in row of old buildings

[ubonr1971]

We own an old building on a corner and theres a row of buildings connected to us. 

 

Next door they recently purchased and are doing their renovations. They have ripped up the old tile floors and right at the back of their room, on the ground floor, is what you see in the first pic. It shows the mini trench that runs through the entire set of buildings all the way along the rear of each building. 

 

Their workers are saying its not good bc during the rain season the water flows along here and smells blah blah. My tenant has a restaurant. He said they told him they saw oil and a bit of chili floating past. We turned on all the taps in our building on the ground floor and then went to see if any water was passing through. There was none. So then they said it must be coming from from the rain water in the roof passing down the the vertical pipe. 

 

But actually the owner told us they will re-do the floor and it will be covered with tiles. But their workers seem to have a power trip trying to tell us that we need to re-design things on the corner of our building outside as shown in the 3rd pic. I dont know if its an easy fix and just concrete over the round hole in the 3rd pic. 

 

My biggest concern is that the new owners will probably put concrete over that square hole in pic 1. Problem solved for them. We will not know about it until the rain season starts and I wonder where that water will go exactly. The water level will rise up and maybe it will come out the hole in pic 3

 

Do you think we should bring some officers from the district office that might support us and give an opinion. With a small envelope maybe we can tell them to say that they are not allowed to block up that hole. 

 

Any opinions on this are appreciated.