Municipal Pipe Lining: Sanitary and Storm Mains, Laterals and Manholes

What a municipal lining program covers

A city's buried sewer system is its largest asset and its least visible one. Sanitary mains from 8 to 60 inches and larger, laid from the 1880s through the 1970s in clay, brick, concrete and asbestos-cement; storm mains and culverts in concrete and corrugated metal; tens of thousands of service laterals, the public portion of each under the street; and the manholes that connect it all, their concrete eaten by hydrogen sulfide. The symptoms are familiar to any utility manager: sanitary sewer overflows after rain, sinkholes over a storm line, pump stations and a treatment plant handling twice the flow they should because half of it is groundwater, and a consent decree or a state order that counts all of it. Sewer pipe lining is the tool that lets a utility address that by the mile rather than by the block, without closing streets or replacing pavement, and it has been the dominant method of sewer rehabilitation in the United States for forty years.

Condition assessment comes first

A program starts with knowing what is in the ground. Crawler cameras survey each reach from manhole to manhole, and the inspection is coded under NASSCO's Pipeline Assessment Certification Program, PACP, so that a crack in one basin means the same thing as a crack in another and the defects can be scored. Manholes get the companion MACP coding; laterals, LACP. Flow monitoring in the basin, dry-weather against wet-weather, measures the infiltration and inflow that the rehabilitation is meant to remove. Smoke testing and dye testing find the inflow sources, roof drains and sump pumps tied into the sanitary system, that lining will not fix. The output is a ranked list of reaches, each with a PACP score, a diameter, a depth, a groundwater condition and a recommendation: liner, point repair, burst, spin-cast or replace, which the camera inspection page describes in more detail.

Lining a main from manhole to manhole

A reach is lined in one shot from one manhole to the next. The flow is plugged upstream and bypassed, the reach is cleaned and inspected again, and the liner goes in: a felt tube, wet out under vacuum at a plant and delivered refrigerated, inverted with water or air under ASTM F1216 and cured with hot water or steam; or, increasingly, a glass-reinforced tube pulled in under ASTM F2019 and cured by an ultraviolet light train drawn through it at a logged speed. UV glass liners have taken a growing share of the 8- to 48-inch market because they are thinner for the same design load, cure in a fraction of the time, are not affected by groundwater temperature and produce a cure record automatically. Each lateral connection is then reinstated by a robotic cutter, and a post-lining PACP inspection closes the record. The sewer pipe liners page compares the two liner systems; the sewer pipe lining equipment page covers the light trains, steam rigs and cutters a specification will ask about.

Laterals, manholes and the rest of the basin

Lining the main stops the infiltration through its joints and cracks, which is a large share of the groundwater in most older systems. It does not stop what enters through the laterals and the manholes, and a program that lines only mains often measures less reduction than it expected. Lateral lining addresses the connection with a top-hat or brim liner that seals the junction between the lateral and the new main liner, or a full lateral liner from the main to the cleanout at the property line, installed from the main by a lateral-launch unit. Manhole rehabilitation seals the chimney and the bench, usually with sprayed cementitious or epoxy liners, or a spin-cast structural shell on badly corroded structures, as the spin-cast lining page covers. The most effective programs do all three in the same basin and verify the result with flow monitoring afterward. Storm systems are a separate program with their own materials and methods, covered on the storm drain lining page.

Where lining is not the answer

A main with a sag that holds solids, a reach that has lost grade, or one that is undersized for the development above it is a pipe bursting or an open-cut replacement candidate, and bursting can upsize. A collapsed section gets a point repair or a short dig before the liner. Large-diameter concrete and brick above roughly 36 inches often goes to spin-cast mortar rather than CIPP on cost. A good assessment sorts the system into these categories before the specification is written, so that the lining contract is for pipe that should be lined. The pipe lining vs pipe bursting page lays out the division.

Specification, design and testing

Most municipal CIPP specifications descend from NASSCO's guideline specification and the ASTM standards it references. The specification names the method (F1216 inversion, F1743 pull-in, F2019 UV glass), the material standard (D5813), and a design: the liner thickness for each reach is calculated under the F1216 design appendix from the diameter, depth of cover, groundwater head, soil load, host-pipe ovality and the resin's long-term flexural modulus, discounted from the initial value by a creep retention factor, typically 50 percent, over a 50-year design life. It requires the contractor to submit the design, the manufacturer's certification of the liner and resin, and the cure procedure. It requires a sample of cured liner cut from each reach, or from a restrained mold at the manhole, to be tested by a third-party laboratory under ASTM D790 for flexural strength and modulus, with the F1216 minimums of 4,500 psi and 250,000 psi for felt liners or the design values for glass. It requires pre- and post-lining PACP video, a leak or pressure test on some reaches, and a warranty term on top of the design life. The industrial pipe lining page covers the chemically resistant resin selection that process and plant sewers add to this.

Bypass pumping and the public

Flow does not stop for the cure. Bypass pumping, with the upstream manhole plugged and pumps lifting the flow through a temporary surface line to a downstream manhole, is how a reach is lined dry, and on large-diameter mains it is the biggest cost after the liner. Bypass is sized to peak wet-weather flow with a standby pump and continuous attendance, because a bypass failure is a sewage spill. Residents on the reach are notified that their service will be interrupted for the day of the cure and that styrene odor from a polyester resin may be noticed; traffic control is set for the manholes in use. A well-run contractor handles this routinely, and the specification should say who notifies, how far in advance, and what happens if a lateral cannot be reinstated the same day.

How municipal lining is bid

Unit price per linear foot by diameter, with mobilization, cleaning, pre- and post-inspection, bypass pumping, lateral reinstatement, point repairs, manhole work and testing as separate pay items, on estimated quantities that the engineer's assessment provides. Per-foot prices for mains are a fraction of residential lateral prices because the fixed costs of mobilization and equipment spread over thousands of feet, and they vary with diameter, depth, groundwater and local market, so a city comparing bids compares the whole schedule rather than the liner line. Multi-year programs are often bid as indefinite-quantity contracts so that a qualified contractor can be issued work orders basin by basin. Federal and state programs fund a great deal of it, through the Clean Water State Revolving Fund in particular, and a condition assessment with PACP scoring is usually a prerequisite for that funding.

Qualifying the contractor

The liner is only as good as the crew that installs it, and specifications qualify the contractor accordingly: documented experience with the specified method and diameter range, a minimum of completed footage, PACP-certified inspection operators, the equipment to perform the cure and produce its records, the liner manufacturer's certification of the installer, and references from comparable utilities. For smaller municipalities and districts that do not run a full program, the state guides on this site identify the verified lining contractors by territory; many of them perform municipal and district work alongside residential and commercial lining, and the national line can identify regional specialists for larger diameters and ultraviolet work.

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