State of Technology Report for Force Main Rehabilitation, Final ...

A whole host of ASTM specifications and AWWA standards cover the various types of materials and
installation practices that may be used in a renewal project. Many of these are included in this report,
along with a brief description. Some of the ASTM standards include non-mandatory design appendices,
which are all patterned after Appendix X1 of ASTM F1216. ASTM F1216 is the standard practice for the
rehabilitation of gravity and/or pressure pipes using a CIPP inversion product.
For gravity applications, the design appendix in ASTM F1216 requires that the liner be designed to
support (without buckling) any external hydrostatic head if the host pipe is partially deteriorated and all
external loads (without buckling) if fully deteriorated. Of course, the determination of whether the host
pipe is partially or fully deteriorated is subjective. Likewise, depending on the ratio of the diameter of
any holes in the pipe to the pipe diameter, the liner is designed to either act as a flat plate with fixed edges
covering the hole or, if the host pipe is fully deteriorated, then as a thin ring under hoop stress from the
internal pressure. In both of these design cases, either the long-term flexural strength or the long-term
tensile strength is used. However, there is no standardized test method defined to determine either of
these properties for a CIPP product. It is up to each manufacturer to establish those long-term properties.
Based on a survey of CIPP producers, few if any have embarked on an extensive test program similar to
that required for the pressure design of FRP/GRP or thermoplastic pipes.
Most of the QC requirements in the ASTM and AWWA standards pertain to use in a gravity sewer or a
pressure water main. None combine the corrosion resistance necessitated by the sewer effluent and the
long-term tensile strength of a pressurized main. Post-installation closed circuit television (CCTV) is the
most common QC requirement for all liners followed by the retrieval of samples for physical property
verification. Leak tightness testing is also recommended.
Operation and Maintenance
Some of the best practices for O&M are cleaning, addition of cathodic protection, installation of
continuous corrosion monitoring, pressure monitoring, leak monitoring, and acoustic monitoring of
prestressed concrete cylinder pipe (PCCP) for wire breaks. These measures can be effective in either
prolonging the life of a buried sewer force main or allowing a utility to monitor real-time performance so
action can be taken as needed to repair, rehabilitate, or replace before a catastrophic failure occurs.
Proper cleaning can improve the capacity and hydraulic performance of a sewer force main. Cathodic
protection can arrest any further external electrochemical-induced corrosion of ferrous mains.
Continuous corrosion monitoring can be installed on new mains or added to existing mains. Ultrasonic
sensors measure loss of internal wall thickness. Leaks can be a precursor of failure and locating leaks in a
force main using acoustic devices can help to prevent catastrophic failures.
A rehabilitated main effectively adds to the range of material that must be potentially repaired in an
emergency. There are no set procedures for repair of rehabilitated (i.e., lined) force mains. This is an
area of concern for utilities and certainly makes them reluctant to line their mains because they do not
know how to deal with them when emergency repair becomes necessary.
Gaps Between Needs and Available Technologies
Little data are obtained on force main condition upon which assessment and subsequent rehabilitation
decisions can be based. So rehabilitation decision-making is often based on operational indicators such as
power consumption, air release valve operation, or main breaks. The renewal decision should be based
on three elements: the rate of deterioration of assets; the condition of critical locations; and whether
spending can be deferred. A first step is to establish risk-based assessment methods to identify force
mains with serious consequences of failure, either in operational or environmental and public impact
viii