Finance Committee - 3/6/2019 Page 8
Alderman Laws
The lining goes inside of the sewer, correct?
Amy Gill, Senior Staff Engineer
Yes it goes, you will take a manhole and drop the lining inside the sewer and then it’s like | said ...
Alderman Laws
And it fills up the sewer. Does it affect flow rates is my question.
Amy Gill, Senior Staff Engineer
It actually improves the flow rate, while you lose the diameter of the pipe ever so much say in a 15 inch pipe
the inner diameter may be reduced approximately an inch/inch and a half. There is a flow rate value that is
increased because the interior pipe is no longer a rough surface as you have a pipe, but now you have a
smooth practically plastic pipe which you have when it is all cured and that helps with the velocity of the flow.
Alderman Laws
That’s great. Especially for downtown where flow rates are an issue with a lot of businesses, this might
actually help them.
Amy Gill, Senior Staff Engineer
Yes actually because it is a much smoother surface, the calculations for flow tend to increase a little bit.
Alderwoman Kelly
| had two, | am going to try to remember the second one by the time I’m done with the first one. Oh |
remember, so question one, are we ever able to line it more than once or is it just a one time and then you
have to replace it?
Amy Gill, Senior Staff Engineer
| am not aware of any pipes yet that have been lined twice. The philosophy that we are trying to use with the
City is we are trying, we are working with lining companies, this is our second, or third lining contract and we
are trying to do as many pipes as possible. There is a range of condition when we are going into the pipes,
some have more severe cracking than others.
We do line the pipe once no matter how significant the problems are, but we do feel if there is an area, for
instance we lose the shape of the pipe and therefore its structural ability, we wouldn’t be able to line that a
second time but we would actually probably have to excavate and then replace it with a new pipe.
Alderwoman Kelly
Follow up? My second question was whether we ever go in after we’ve looked it by camera and realized that it
can’t be lined that is much further gone than we expected?
