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