More on the chestnut sidewalk
The second problem with the storm drain area
involves a sink hole behind the storm drain basin. We had no idea what
the problem was but we knew we couldn't pour a sidewalk over a sink
hole without finding what caused it and then we must repair it. The
city had filled in the sink hole with some dirt in the past but there
was already a hole developing again. Once we removed all the kudzu and
the broken fence (that was built in the right of way) we could see this
sink hole, the wall, the pipe and the spring fed stream feeding the
pipe. The below shot shows the retaining wall, the spillway that will
be rip-raped that will allow the flue to drain into the stream bed and
also where the sink hole is located. As you can see the sink hole is
right under where the sidewalk needs to be.
The next shot shows a closeup of the problem. What
has happened is the first section of pipe has pulled out of the next
section of pipe that is attached to the roadside storm water drain
basin and the pipe then continues under the road. Right now the only
problem is with this first section of pipe, as the rest of the pipe
under the road is all OK. But if this isn't repaired fairly soon, it
will erode the dirt around the pipe under the road and the whole road
will need to be dug up! That would easily quadruple the cost of
this repair.
This is typical of the kind of problem that creates
a sink hole and is why pipes like this need to be sealed up well. It's
also a good example of why you don't want to pipe a stream unless you
have to, like in this case where the stream goes under a road. There
are a couple of ways of repairing this and right now we are letting the
city storm water manager look into this issue and how best to fix this.