I'm sorry to say that there is not currently a map showing the mile markers.
But I understand how useful this would be, so I will build that feature. It may take several days, so unfortunately that won't help you right now. But it's in the works and I'll post something here when it's ready.
In the meantime, here's what to do:
1. Go to the Towns and Services
2. The fourth column tells you the mile marker number at each town, for example Portland is mile 115.9.
3. Go to the Katy Trail Map
4. Right under the map, you'll see "Center Map at" - select Portland from this list.
5. Below that, you'll see "Show mile markers every" - select 1 mile
and click Update Map
6. Now you see the distance measurements from Portland. Since you know Portland is at mile marker 115.9, you know the 117-118 closure is between roughly 1 to 2 miles west of Portland (note that 117-118 is west of Portland, not east).
So again, sorry that you currently have to go through the above steps to see this info on a map, but I will get a "Mile Marker" feature added to the map ASAP.