By Hugh B. Mickel, P.E.
| Tuesday, August 01, 2017 | 2177 Views |
I am often asked, "How much does a reline project cost?". Before making an attempt to answer this let’s begin with some perspective, relative to traditional approaches. When comparing reline options to open cut and replace options, segmental sliplining is nearly always the most cost-effective approach, unless the site has some unusual features (such as low traffic volumes over the top, short detour distances, shallow cover with no utilities, etc).
Of course generalized cost estimates that don’t factor in specific design and construction constraints could end up being highly inaccurate. The factors that usually contribute most to the costs include:
- Condition of host pipe
- Installation plan to get the new pipe inside the host pipe safely
- Size, shape & fit of the new pipe
- Material type
- Expected service life and structural design goals for the new pipe
- Amount of annulus grout
- Type of access
- Appurtenant improvements required
- Traffic control (if needed)
- Bypass costs (if needed)
- Labor and operator wage rates
- Skill set of local contractors; etc.
Segmental sliplining is nearly always the most cost-effective approach, and high end CMP products (aluminized steel type 2, aluminum, polymer coated) are nearly always the least expensive. It’s important when designing with CMP to check the pH and resistivity at low level flow to make sure a material is selected which will provide the intended service life. Part of this process should include a hydraulic design analysis and a look at the 2 year velocity to determine material suitability for the expected abrasion level. FHWA defines abrasion levels and the Contech CMP Design Guideline provides recommendations on material selection. From a material selection standpoint, here are other options we offer:
- DuroMaxx® SPRE – cost-effective and both abrasion and corrosion resistant
- SPR™ PE – ideal for closed system storm and sanitary sewers and culverts with limited access
- Tunnel Liner Plate – ideal hand-placed solution, available in ALT2 and Aluminum
- Snap-Tite® solid wall HDPE pipe
- A2™ Liner PVC Pipe
- ULTRA FLO® spiral rib pipe
- Aluminum structural plate and a host of other plate and precast products are also effective depending on the size and shape needed - including SUPER-SPAN™, SUPER-PLATE®, CON/SPAN® and BEBO®
Although convenient, an open end at the inlet or outlet of a pipe to be relined isn't a requirement. Access shafts and insertion pits can be cost effective and still allow segmental sliplining to be the best overall, and least expensive approach. Each situation must be evaluated and the services of a qualified engineer can be a huge benefit.
For closed systems, or systems with tough access, no access, or other challenging characteristics, wound-in-place technology is available. It is called SPR™ PE and the liner pipe is manufactured inside the host pipe via manholes or created access points. The equipment and materials that produce the SPR™ PE can fit through a standard manhole opening. Costly bypass pumping can often be avoided too.
Now back to the question, "How much does a reline project cost?"
A general rule of thumb for the cost of lining a culvert, large diameter storm sewer or small bridge is often in the range of 2.5 – 4 times the sliplining material cost, but most situations are unique so it’s difficult to pinpoint a cost estimate until some preliminary design work is done. This factor can be 2 and it can be over 6. So unfortunately there’s no easy answer to this question.
The good news with all of the Contech reline options is that no specialized training or equipment is needed (except with SPR™ PE ), so any local utility or underground contractor can do this work.