The only problems i can see with this is sewage workers coming out to check on the pipes. Other then that it gets alot of direct sun light. for those of you who dont know what im talking about I drew a picture.
for sewage litter and to see if the lids have been lifted.problems on the sewage network tend to recur, if that section of pipe gets blocked it's more likely someone will come out to check it. If it's a big enough pipe some one might have to walk along it to check for problems now and then.
If I LST and keep the plants low and off to the side, nearer to the woods then the manholes, i think it should be a straight spot, there isnt enought room for a car to pass which is good because that means they didnt intended to be down there enoght to where they thought it would be an advantage to be able to drive a car down there.