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Alan sutton

  1. 1. “CASE STUDY OF THE DESIGN AND INSTALLATION OF STRUCTURAL LININGS FOR OVIFORM SEWERS” ALAN SUTTON B.Sc (Eng). CPEng. MIEAust. Engineering & Overseas Development Manager Kembla Watertech P/L
  2. 2. ABSTRACT • Sydney Water Corporation (SWC), in common with other major authorities, has a number of critical sewer mains of oviform shape. While this ‘egg’ shape has the advantage of providing a self cleaning velocity at low flows, the same shape makes it very difficult to design and install a lining that will restore structural strength to the sewer without loss of flow capacity. • Kembla Watertech was approached by SWC regarding the rehabilitation of two of their oviform sewers using a cured in place pipe (CIPP) type lining. • This presentation will first highlight the discussions between client and contractor to design structural linings to satisfy external load conditions (e.g. 13m depth) and then will detail the installation work which was undertaken at night during restricted hours and involved large scale sewer bypass and traffic control set ups.
  3. 3. SHORT BACKGROUND TO KEMBLA • Kembla Watertech P/L has been active in the pipeline rehabilitation market since 1993 • Kembla has been actively involved with SWC since 1993 • Currently some 170 personnel and 50 installation units • Kembla currently has Term Contracts for sewer/water main rehabilitation with SWC, Hunter Water, South East Water, City West Water, Brisbane Water & Citiwater Townsville.
  4. 4. ENVIROLINER PIPE LINING SYSTEM • Enviroliner is a process for the renovation of pipelines by the installation of a resin impregnated flexible tube which is inverted into the existing conduit by use of hydrostatic pressure. • The tube is cured to a hardened state while held in intimate contact with the conduit. This type of system is classified as a Cured In Place Pipe (CIPP) and is a trenchless method for restoring full structural integrity to deteriorating pipelines. A number of companies in Australia offer CIPP linings. • The system is suitable for all diameters from 100mm to 2000mm but generally is more cost effective in the larger diameter range. • A CIPP liner is tailor made to suit the circumference of the pipe and because it is inserted in a softened state it will take the shape of the host pipe. This makes it ideal for non circular shapes such as OVIFORM.
  5. 5. WHY AN OVIFORM SEWER ? • A velocity of 1 m/sec is capable of moving solids and debris in a pipe flow condition. • Early studies also showed that the lower part of a "V" channel shape could carry sanitary waste flow efficiently while the upper portion had sufficient capacity to transport storm water. • This then led to the evolution of the ‘egg’ or oviform shaped pipe. • When new sewers were designed for London, Paris etc in the last half of the 1800s, oviform shaped sewers were determined to be the best cross-section for the larger "combined" sewers.
  6. 6. OVIFORM SHAPE • Over time, the “self cleaning” characteristics of the oviform shape proved to be as effective as the engineers had projected and this shape was used extensively in early sewer construction not only in Europe but in Australia as well. • Given that many of the first major sewers constructed in Australia used oviform shaped pipes then it is no real surprise to find that they now represent a critical component of the sewer network. • Cities have “grown up” above these early sewers and they are most often found in densely populated areas. • The two sewers chosen for this presentation highlight the difficulties now facing authorities with ageing oviform sewers. • The concept of oviform shaped pipes had many advantages over circular profiles: higher flow rates during low flow periods - improved self cleaning effect - reduced trench width - higher load carrying capacity - a higher vertical profile which makes man access easier. • The downside unfortunately was that with the advent of large diameter spun concrete pipes they became too expensive to produce or lay and were phased out as a new sewer pipe option many years ago.
  7. 7. PROJECT BACKGROUND • Kembla is one of two specialised contractors working on the Sewer Rehabilitation Program 2006/09 for SWC . • Worth stating again that SWC, in common with many other authorities, has a number of critical sewer mains of oviform shape. While this shape has the advantage of providing a self cleaning velocity at low flows, the same shape makes it very difficult to design and install a lining that will restore structural strength to the sewer without loss of flow capacity. • Oviform GRP segments have been trialled but have not proven cost effective because of: - the loss of cross section - the cost of filling the gap with grout - the cost of the purpose-built moulds
  8. 8. Site 1: O’CONNOR ST HABERFIELD 760mm x 600mm concrete sewer in O'Connor St, Haberfield. This sewer is approximately 95 m in length and includes a 90 degree bend. 760mm x 600mm approximates to a 650mmm circular liner It was rightly identified by SWC as being in need of urgent rehabilitation, particularly in the vicinity of the bend where CCTV survey had A revealed holes in the side of the pipe. The sewer is located in a roadway and SWC asked Kembla to “investigate this matter with a view to rehabilitating this asset by installing a continuous lining.”
  9. 9. Site 2: LYONS RD DRUMMOYNE At the same time as investigation was being done on Haberfield we were also asked to look at the lining option for a 533mm x 406mm concrete oviform sewer in Drummoyne. (Approximates to a 450mm dia. lining). A CCTV survey had revealed serious deterioration of the inside concrete surface of the sewer.
  10. 10. A B C PHOTO PHO TO As shown above, this sewer was laid UNDER Lyons Rd near to its intersection with Victoria Rd, two very busy thoroughfares. The following factors made this job extremely difficult: --- the sewer was 13m deep at access chamber B, which itself was located in the middle of Lyons Rd --- total length to be lined was 350m from A to D D --- a 225mm diameter rising main discharged at access chamber D and the only feasible route to bypass the flow from D to A was across Lyons Rd. --- local streets were narrow and densely populated
  11. 11. CROSS SECTION OF DRUMMOYNE SEWER The lining from C to A was eventually installed in one single 250m long installation because of constraints with access to chamber B in the middle of Lyons Rd. The thickness and length of this lining made it one of Lyons Rd the most difficult CIPP linings ever installed in Australia. Access 13 m chambers deep B C A 250m length
  12. 12. DESIGN OF A STRUCTURAL LINING SWC has issued a technical specification “limited to non man-entry linings to be installed in intact oviform conduits that do not rely on any bond with the existing sewer for their structural capacity.” It assumes that the existing sewer is in good condition and capable of carrying the externally imposed earth and traffic loading. The liner is designed for hydrostatic loading caused by a water table located above the sewer. Oh
  13. 13. DESIGN OF A STRUCTURAL LINING • There were numerous meetings between Kembla and SWC design staff to determine the appropriate design criteria to be applied. The lining was required to be designed to satisfy the SWC performance criteria for buckling, strength, deflection and minimum liner thickness. • Each lining was checked for buckling with the oviform liner considered as a circular pipe with an equivalent circular diameter of Deq = 1.75 * Ow • Strength and deflection design was then undertaken based on the procedure set out in the Water Research Centre, Sewer Rehabilitation Manual 2001 Volume II Chapter 5 for non circular linings. • Calculations were carried out to ensure long term bending stresses and strains were less than the maximum permissible values for the lining. The liner critical length (Lcrit) is defined as the greater of Ow or 2/3*Oh and the maximum allowable deflection of the liner (Δall) shall not exceed 3% of Lcrit. The critical length shape factor (R) is specified as 0.5.
  14. 14. DESIGN RESULTS 1) Haberfield: This sewer, although larger in dimension than the Drummoyne sewer, is only at a shallow depth and if the sewer pipe could be considered as “intact” then the design thickness required was 16 mm. This thickness was within normal limits and so the more critical aspect of this project became how to provide an ‘intact’ pipe at the deteriorated 90 degree bend. 2) Drummoyne: The 13m depth of the Drummoyne sewer was a problem and a design thickness of over 22mm resulted from the use of the normal design criteria. This is not a practical option in a lining that correlates to a 450mm diameter. After consultation with SWC and the manufacturer of the linings as well as overseas CIPP contractors, an 18mm thickness was adopted as the maximum thickness that could be manufactured and confidently installed at this diameter.
  16. 16. LINING INSTALLATION • Because of their non-standard size, the linings were specially manufactured at an ISO 9001 accredited facility in the UK which supplies CIPP linings worldwide. • Mixing and impregnation of the resin was carried out at Kembla’s CIPP factory in Newcastle. • Cleaning of oviform pipes is a unique process requiring special cleaning techniques. In keeping with our preferred policy, Kembla used its own experienced cleaning crew and equipment for this work rather than sub contractor. • To ensure no structural damage was done during pressure cleaning and no debris was missed that could effect the lining installation process, we employed a live CCTV coverage of the cleaning process.
  17. 17. LINING INSTALLATION • The impregnated linings were stacked into a refrigerated truck for transport to site. If kept cold, the impregnated linings have a considerable shelf life which provides a contingency against unforeseen events. • Either a head of water or air pressure is used to create internal pressure to the lining which turns (or inverts) the liner inside out and presses the resin felt composite tight against the pipe wall. • Because of the oviform shape, water was used for the inversion process in this case.
  18. 18. LINING INSTALLATION • The weight of the liner required the use of a crane to lift it from inside the trailer into position. • The internal pressure is maintained at all times so that the lining is held tight against the pipe wall. • Once the lining reaches the far end hot water or steam is circulated inside the lining while the internal pressure is maintained until the lining is fully cured in place. Given the thickness of 18mm and the oviform shape, the 250m single length installation at Drummoyne was one of the most difficult ever undertaken in Australia. This lining had a total weight of 8.7 tonnes and was successfully installed over one night ------- highlighting the speed and efficiency of this type of lining system.
  19. 19. PROJECT EXECUTION: SEWER BYPASS • Sewer bypass at Haberfield was reasonably straightforward and Kembla used its own 100mm portable pumps and hoses. • The Drummoyne project however presented a very difficult bypass situation where the dry weather flow capacity had to be 165 L/sec. • As previously mentioned the only feasible route to bypass the flow was up one narrow street, across Lyons Rd and then down to the discharge chamber. Consideration was given to directional drilling under Lyons Rd however this was cost prohibitive. Instead, a 400mm wide x 500mm deep trench was dug by Kembla’s own civil crews who laid 2 x 200mm lay flat hose lengths within the trench.
  20. 20. PROJECT EXECUTION: SEWER BYPASS • Coates Hire was employed as subcontractor for this activity. • The bypass operation included maintaining balance of pump flows during high and low conditions, fuelling of pumps, maintenance of pumps and in the event of breakdown the engagement of standby pumps and repair of the duty pump. • The system employed was 2 x 200mm high pressure lay flat hoses supplied by 2 x 200mm portable silenced diesel pumps. The lay flat hose arrangement allowed for quick dismantling once installations were completed. • All entry to access chambers for plug installations was carried out by Kembla’s site personnel who are all trained in confined space entry. • While a logistical nightmare, the flow management strategy proved effective and efficient in bypassing the existing sewer flow for the duration of all site activities without a single environmental incident.
  21. 21. PROJECT EXECUTION: SEWER BYPASS : sewer 600m of twin 200m hose
  22. 22. PROJECT EXECUTION: SEWER BYPASS The following steps were implemented to ensure the safe isolation of the Oviform sewer pipes.  Flow Management Plan developed and approved.  Weather checked prior to commencement of bypass.  Work to be done at night during low flow periods.  Special plug to be used on Oviform pipes.  Continuous monitoring.  Emergency spill trailer on site to mitigate spills.
  23. 23. PROJECT EXECUTION: CUSTOMER RELATIONS • Given the high profile location and densely populated streets, Customer Relations was always going to be a major focus for both Kembla and SWC personnel. • A preliminary meeting was held with Sydney Water Communications team to discuss details of the work, roles and responsibilities. • After defining the perimeters for the directly affected residents and commercial customers, site specific letters were prepared detailing dates and work times for directly affected residents and commercial customers. Directly Affected Commercial Customers Directly Affected Residents
  24. 24. PROJECT EXECUTION: CUSTOMER RELATIONS • Kembla’s Customer Relations Officer was on site at Drummoyne throughout the night work activity. • Residents were advised of this prior to work commencing to give them a sense of assurance that there was someone on hand who was aware of their situation and who could provide them assistance should they need it. • When the work was completed at both Drummoyne and Haberfield the Customer Relations officer visited all residents (who were home) and Commercial customers, to advise that work had been completed and to thank them personally for their patience during this time. Many advised that there had been no disruption to their life and routines at all, which would certainly had not been the case if Trenchless Technology had not been adopted.
  25. 25. PROJECT EXECUTION: TRAFFIC CONTROL Detailed traffic control plans were drawn up for Haberfield and Drummoyne following extensive consultation with both Local Government and the RTA. The Haberfield Oviform required O’Connor Street to be closed for 3-4 weeks including the time needed to concrete encase the bend in the oviform.
  26. 26. PROJECT EXECUTION: CONCRETE ENCASEMENT • When the up to date CCTV survey was carried out on the Haberfield sewer the condition of the bend was found to have deteriorated further than previously observed and confirmed Sydney Water’s wisdom is nominating this section for rehabilitation. • Because of the design requirement for the sewer to be in an “intact” condition, SWC decided to concrete encase the bend to provide long term stability to the sewer. • The CIPP lining was to be installed first and this was carried out successfully through the 90 degree bend in its deteriorated condition.
  27. 27. PROJECT EXECUTION: CONCRETE ENCASEMENT • Once the lining had hardened, the existing sewer was able to be exposed for the encasement work without the need to bypass the flow. • Even though a SWC approved sub contractor was used for this work they were still required to be site inducted by Kembla before work could commence. The civil subcontractor was required to submit an Authority to Work Permit on the afternoon prior to commencing work the next day and this enabled us to track the subcontractor’s activities and provided us with a check list of who will be onsite, their skills mix and to confirm each person had been inducted.
  28. 28. This paper has attempted to highlight some of the design and installation difficulties facing any authority with oviform or egg shaped sewer mains. The ‘before and after’ videos below, are proof of the ability of an experienced No Dig specialist contractor to work closely with the owner of the asset to provide a long term rehabilitation option for what are now ageing oviform sewer conduits.