Special Board of Aldermen 04-26-2021 Page 3
the system gets overwhelmed then there’s discharge points on those rivers. Four in Nashua and five on
the Merrimack. We have 8 siphon chambers which carries storm water and sanitary flow under the rivers
and those are comprised of 22 separate barrels ranging in sizes from 6 inch to 60 inch.
I’m not going to read all this on the slide but as you can see, our system dates back to the 1860s when the
first sewers were installed. We have a number of large brick sewers and then sewers ranging in 6 to 100
ages. Sewer depths range from 3 to over 31 feet. So you can imagine it’s problematic to replace
something that that’s deep. The other stats and figures are shown there. On the right-hand side, you see a
picture of sewer on Canal Street — one of the brick sewers.
So under this program, we asses and then repair sewers. As part of the assessment, we need to clean the
pipes and that is important. As you can see in the upper right-hand picture, there’s a root ball there. So we
cleaned the pipe and then we video inspect it through closed circuit television. That enables us to see
which sections of pipe need a treatment. The cleaning effort in itself is valuable in that it restores the pipe
to its full capacity. On the bottom right you can see that happening — a jet jetting water in a brick sewer
main.
Under the program, we do rehabilitation of the pipes and structures. One of the methods is pipe repair.
When we have a collapse at one location that’s showing on the right-hand side, we'll go in and dig that up
and just make a repair to that a small segment pipe. There’s other more extensive repairs so on the bottom
left you can see that’s a pipe that we video inspected and it had some issues but is still of a shape that we
could line it. So on the right-hand side, you can see that we (inaudible) lining so that restores structurally
sound pipe that is smooth again.
In the upper right-hand side is showing an epoxy lining of a manhole looking down from the top. That just
protects against groundwater leaks and stuff into the structure through cracks. It basically seals up the
inside. It's another measure we do here.
Some more pictures upper left. You can see that’s quite extensive root obtrusion in the pipe. On the right-
hand side after we cleaned the pipe and lined it, that’s what it looks like. Bottom pictures are just some
more of the types of deterioration we find.
Not all pipes can be lined. We do like lining. We’re doing more and more of it because it’s very cost
effective. Much more disruptive to actually have to replace a pipe, disruptive to traffic, much more
expensive. Almost 20 times as expensive as lining it. We are trying to line everything that we can but
occasionally that’s not possible and we have to dig up and replace the pipe. So these pictures show some
of those efforts and some of the problems we found before we actually addressed them.
Just looking at a little budget history for the program going back 10 years or so. The program has
escalated over the last 5 or so years and over the last few years, we’ve been in a similar $5 million plus
range and that’s enabled us to do more and more work.
Here’s some of the results of that work. Some of the older data — maybe we don’t have all of the
information on but our more recent data is fairly accurate. You can see replacement. We've reduced
actually the amount of replacement that we’ve been doing and have been doing more and more lining.
We're prioritizing our looking in the system at the pipes that are oldest and types of materials that are most
prone to having this used. As we work through the system and find and address those and the pipes get
newer and of materials that are better, we would expect over time that we would see less and less
replacement need.
On the right-hand side is just a picture of some dig work, some new piping and a new structure. That’s
what | have. I’d be happy to answer any questions.
