Olinda Outdoor Pool - Structural Review

Transcription

1 Report Olinda Outdoor Pool - Structural Review Prepared for Yarra Ranges Shire Council By Beca Pty Ltd ABN: May 2014 Beca 2014 (unless Beca has expressly agreed otherwise with the Client in writing). This report has been prepared by Beca on the specific instructions of our Client. It is solely for our Client s use for the purpose for which it is intended in accordance with the agreed scope of work. Any use or reliance by any person contrary to the above, to which Beca has not given its prior written consent, is at that person's own risk.

2 Olinda Outdoor Pool - Structural Review Revision History Revision Nº Prepared By Description Date A Peter Cole Draft Report 11 April 2014 B Peter Cole Report 13 May 2014 Document Acceptance Action Name Signed Date Prepared by Peter Cole PWC 12 May 2014 Reviewed by Timothy Cox TJC 12 May 2014 Approved by Paul Collier PHC 13 May 2014 on behalf of Beca Pty Ltd Beca // 13 May 2014

3 Table of Contents 1 Introduction Limitations Background Summary of Received Reports Sharp and Howells Concrete Test Report Infracorr Electrochemical Potential Testing Report EJ s Plumbing Pipework Pressure Test Report Beca Inspection and Findings Site Visit 21 January Site Meeting 11 February Site Visit 17 February Recommendations Works Required For Non Liner Option Works Required For Liner Option Conclusion Appendices Appendix A - Sharp and Howells Pty Ltd Concrete Test Report Appendix B - Infracorr Electrochemical Potential Testing Report Beca // 13 May 2014 // Page ii

4 1 Introduction In response to a request from the Yarra Ranges Shire Council (Council), Beca has undertaken a structural review of the Olinda Pool, located on Olinda Monbulk Road, Olinda. The purpose of the review is to inform Council of the suitability of the pool shell for future use. As part of the review, Beca personnel visited the site on: Tuesday 21 January 2014 to meet Council representatives and to inspect the pool shell; Tuesday 11 February 2014 to meet Council representatives and staff from Liner Specialists Australia to discuss the option of a pool liner; Monday 17 February 2014 to meet with representatives from Council and from concrete testers Sharp and Howells Pty Ltd and their subconsultant Infracorr Consulting Pty Ltd to witness the commencement of concrete testing. This report summarises and discusses the findings of Beca s site inspections, the concrete testing and Beca s previous report regarding water turnover rates. 2 Limitations This report is limited to a review and advice regarding the main pool shell only and does not include the toddler s pool and outbuildings. The limitations relating to this report are: This report is by exception: i.e. items visually assessed as satisfactory are not discussed. Beca has undertaken a visual walk-over inspection of the pool shell, limited to areas where safe and ready access existed at the time of inspection. As advised by Council, the scope of the investigation did not include geotechnical investigations, mechanical and hydraulics testing, occupational health and safety review, Disability Discrimination Act (DDA) or Aquatic Facility Safety Assessment (AFSA) reviews. It is recommended that these tasks be separately commissioned by Council if not already undertaken to gain a holistic understanding of the asset. We have not carried out any structural checks by design calculation. In preparing the report, we have relied upon documentation and verbal reports provided by Council and by third parties. Except as otherwise stated in the report, Beca has taken this information to be true and correct. Beca will not be liable in relation to incorrect conclusions should any documentation or verbal reports be incorrect or have been concealed, withheld, misrepresented or otherwise not fully disclosed to Beca. 3 Background It is understood that the outdoor pool was constructed in 1964, and is therefore 50 years old. The pool was almost empty at the time of the site visits, with approximately 300mm of water remaining at the deep end. It is a first generation type pool typical of the era and has not undergone significant upgrade since construction, with the exception of the decommissioning of the scum gutters. They have been replaced by 6 nos of 55mm dia soiled water supply (SWS) inlets with star safety covers along the east (long) wall. It is understood that the low level soiled water drain (ELWS) located at the sump in the deep end has been decommissioned. A blind sump remains. Beca // 13 May 2014 // Page 1

5 The pool is approximately 11m wide x 27m (30 yards) long and ranges in depth from 0.9m to 3.5m as noted from the observed depth markings. The pool rapidly increases in depth towards the south end. The pool holds approximately 650,000L of water when full. It is not heated Previous Beca Reports Beca previously reviewed the pool with regard to pool water turnover rates; refer Olinda Outdoor Pool Interim Report dated 13 August In summary, the findings contained in that report were: The pool water circulation rate was estimated to be significantly lower than that required for a commercial pool with typical design bather loads. The current hydraulic piping arrangement does not allow for efficient collection of contaminants via skimming or low level extraction. The ELWS at the deep end has been decommissioned. Chlorinated water is provided to the filtered water returns (FWR) located along the south wall (deep end) only and thus the distribution of chlorinated water is limited. It is understood that the water chlorination and turnover arrangement has not changed since this report was published Council Report Council reported on their website (dated 20 December 2013) that: during a routine inspection of the pool in preparation for summer, Council staff and pool maintenance contractors found the water level in the pool had significantly dropped. A 1.5m drop in water level was recorded this year compared to the average 150mm drop recorded in previous years..the cracks are so significant that when drained, ground water was running through the pool wall into its shell. Photo 1 has been has been reproduced from the website courtesy of Council. This is addressed in Section 5.3. Beca // 13 May 2014 // Page 2

6 Photo 1 Ingress of groundwater through the concrete pool shell 4 Summary of Received Reports 4.1 Sharp and Howells Concrete Test Report Sharp and Howells Pty Ltd (Sharp and Howells) undertook physical, visual and chemical investigation and analysis of the concrete pool shell. They attended site on 17 February 2014 and took 20 concrete core samples from the walls and floor of the pool shell. Their subconsultant Infracorr Pty Ltd conducted electrochemical potential testing on the same day. Sharp and Howells report is included in Appendix A. Beca s interpretation of the findings in their report with associated explanation is provided below. Beca // 13 May 2014 // Page 3

7 4.1.1 Concrete carbonation Carbonation is the formation of calcium carbonate when carbon dioxide from the air reacts with the calcium hydroxide present in concrete. It decreases the concrete alkalinity, which is essential for corrosion prevention of the reinforcing steel. The depth of carbonation was considered to be low. ph profile testing indicated that the concrete remains alkaline Chloride levels Calcium chloride, and to a lesser extent sodium chloride, can leach calcium hydroxide from the concrete and cause chemical changes in the cement, leading to loss of strength, as well as attacking the reinforcing steel, which can cause corrosion. Low to moderate chloride levels were found at depths in the vicinity of the reinforcing steel. Some elevated levels were found at the surface and up to a depth of 40mm in laboratory samples 14/N/0203, 0205, 0207 and Sulphate levels Sulfates in solution in contact with concrete can cause chemical changes to the cement, which can cause significant microstructural effects, leading to the weakening of the cement in the concrete. Sulphates can also cause damage to porous cement through crystallization and recrystallization (salt attack). Sulphate levels were found to be within what is considered to be the normal (acceptable) range Compressive strength Compressive strength was minimum 40MPa which is satisfactory. This supports the generally acceptable readings for chloride and sulphate levels Cement content The cement content is within what is considered to be in the normal range Volume of voids The volume of voids was moderate, with some significant voids found in selected cores. Refer laboratory sample numbers 14/N/0196, 14/N/0198 corresponding to the location shown in Photo 1 and discussed in Section 5.3. The density of the concrete is considered to be satisfactory Reinforcing steel condition The condition of reinforcing steel is reported as good, with corrosion noted at concrete crack or concrete defect locations only. 4.2 Infracorr Electrochemical Potential Testing Report Sharp and Howells subconsultants Infracorr Consulting Pty Ltd (Infracorr) undertook investigation and analysis of the concrete shell for electrochemical corrosion potential. Infracorr s report is included in Appendix B. Beca s interpretation of the findings in their report with associated explanation is provided below. Beca // 13 May 2014 // Page 4

8 4.2.1 Electrochemical potential testing Corrosion of the reinforcing steel in concrete is normally prevented by the alkaline nature of the concrete. If the concrete cover is carbonated, or if chloride ions extend through the concrete cover to the reinforcing steel, then the corrosion reaction can commence, provided a sufficient supply of oxygen and moisture are both present. Depassivation of the reinforcing steel by either or both of the above mechanisms will promote anodic and cathodic activity at sites throughout the reinforcing steel. For reinforcing steel in concrete, anodic regions normally correspond to more negative potentials whilst cathodic regions correspond to less negative potentials and the anodic areas can corrode. The Infracorr report stated that the electrochemical potential results indicate that the reinforcing steel is likely to be actively corroding. The report states that this is likely to be influenced by the pool being predominantly empty at the time of testing, which introduces available oxygen into the cracks thereby exacerbating the recorded electrochemical potential results. The Infracorr report states that the observed cracking of the pool shell is unlikely to have occurred from corrosion during the in-service condition (expansion of the reinforcing steel causing concrete cracking and ultimately spalling) Corrosion rate The Infracorr report states that the rate of corrosion varies significantly and ultimately depends on the availability of oxygen, which is affected by whether the pool remains empty for a long period. At the high end of the recorded corrosion rate, concrete spalling could be expected in the medium term if the pool shell is not repaired and is left open to the air for prolonged periods. 4.3 EJ s Plumbing Pipework Pressure Test Report EJ s Plumbing Pty Ltd (EJ s Plumbing) reported that Australian Leak Detection undertook pressure testing of the SWS and FWR pipework between the Plantroom and pool shell. The tests indicated that: The FWR pipework to the shallow end passed; The FWR pipework to the deep end failed; and The SWS pipework failed. Australian Leak Detection also noted that the stabilised water level in the pool was below the pipework level, which indicates that there are leak(s) in the pool shell at this level. 5 Beca Inspection and Findings 5.1 Site Visit 21 January 2014 Beca personnel visited the site on 21 January 2014 to inspect the condition of the main pool shell. The concrete pediment appeared relatively level and in line (by eye). In conjunction with relatively little vertical or diagonal cracking noted in the pool shell walls, this indicates that the footings and underlying subgrade has been relatively stable over time. The pool shell walls are largely free of significant cracks, with the exception of a significant vertical crack at the climb-out return midway along the east side long wall. This is not a recent crack. It requires structural repair. Refer Photo 2. Beca // 13 May 2014 // Page 5

9 Photo 2 Vertical crack at climb out With the exception of the crack shown in Photo 2, there are no other significant cracks evident in the walls. Repairs of past defects in the walls and the now decommissioned scum gutters appear to generally be in a satisfactory condition. The floor consists of concrete floor panels that abut each other and the wall footing, providing a floor perimeter joint approximately 1.0 metres off the wall, with transverse joints between the floor panels. There is a continuous section of floor at the deep end. There is a flexible top sealant in these joints, which was generally in a good condition, however it has delaminated at selected locations. Council has advised that from previous repair works undertaken, there is no waterstop present beneath the top sealant, meaning that where delamination has occurred, the pool shell will leak. It is recommended that the top sealant be removed and replaced with a hydrophilic waterstop and top sealant system to limit leakage in the medium term. Significant recent, mainly longitudinal cracking in the mid-span of the floor panels was observed. This phenomenon is consistent with heave of the floor due to a high surrounding groundwater level Beca // 13 May 2014 // Page 6

10 in combination with a low pool water level. These cracks will require significant structural repair. Refer Photo 3 and Photo 4. The observed ingress of water through the pool shell wall on the west side (refer Photo 1) is consistent with the surrounding groundwater being higher than the pool water level, in combination with the concrete being porous. The high groundwater levels at the pool site may be due to one or a number of mechanisms in combination with saturated or low permeability soil conditions and an ineffective subsoil drainage system. Beca understand that subsoil drainage exists at least part way around the pool. Photo 3 Recent cracks in concrete floor panels Beca // 13 May 2014 // Page 7

11 Photo 4 Recent longitudinal and transverse cracks in concrete floor panel These mechanisms could be: Leakage of the pool water through the pool shell into the surrounding soil; Leakage from the pool s hydraulic pipework; Leakage from nearby water mains / plumbing; Runoff from Olinda Monbulk Road (particularly to the south west corner of the pool shell) that has infiltrated into surrounding soil. It is recommended that the subsoil drainage system is investigated. Council reported that leakage from the pool shell over the 2013 winter was more pronounced than in previous years, refer Section The cause of the recent leak is not obvious but could be related to the aforementioned vertical concrete crack at the climbout (refer Photo 2) and to the porous concrete (refer Photo 1). It does not appear to be solely related to the hydraulic pipework, as the pool emptied of its own accord to a level some 1.5 metres below operating level (refer Section 3.1.2), indicating that a leak is at this level (as well as others possibly higher in the wall). A leak test of the pool shell is recommended to be undertaken to ascertain the cause of the recent major leak. The pool shell requires repainting prior to recomissioning should a liner not be installed. Beca // 13 May 2014 // Page 8

12 5.2 Site Meeting 11 February 2014 Beca personnel attended site on Tuesday 11 February 2014 with a Council representative to meet representatives from Liner Specialists Australia. Liner Specialists Australia proposed the installation of an Aquaforce 3 ply reinforced vinyl membrane 1.14mm thick. The product has a 10 year limited product warranty and the firm provides a 7 year warranty on their labour. The product has previously been installed at the Croydon Leisure and Aquatic Centre. It is understood to have performed satisfactorily. A successful liner solution is reliant on the substrate material (ie concrete pool shell) being sound and non-porous (noting that porous concrete is evident at at least one location as shown in Photo1). Carefully detailed interfaces with penetrations through the liner such as filtered water returns and soiled water pipework are required to ensure the liner does not delaminate. It is essential that the surrounding groundwater level is kept low and that the hydraulic pipework does not leak during the service life of the liner. Should the liner option be selected, groundwater relief drains would need to be unblocked and/or repaired and maintained in a serviceable condition. The liner is required to terminate below the level of the decommissioned scum gutter tiles to prevent pool water leakage from the scum gutter penetrating behind the liner. Council would need to ensure that the capacity of the soiled water lines is sufficient so that during times of high bather load, the pool water level does not rise over the top of these inlets. Council would need to undertake a significant amount of work to prepare the pool shell and make good the pool s hydraulic pipework prior to the installation of a liner. 5.3 Site Visit 17 February 2014 Beca personnel attended the site on Monday 17 February 2014 with a representative from Council, Sharp and Howells and their subconsulants Infracorr. Beca personnel witnessed the coring of concrete laboratory samples 14/N/0196, 0197 and 0198, all located in the west wall near the location of the ingress of groundwater shown in Photo 1. Photos of laboratory samples 14/N/0196 and 0197 are shown in Photos 5 and 6 respectively. The key features of laboratory sample 14/N/0196 is: the length of concrete 143mm. significant voids noted throughout, particularly at back face. cementitious repair to the front face, variable depth. 2 layers of steel reinforcing, one at the front and one at the back back concrete faces approx. 50mm depth from the core ends. The key features of laboratory sample 14/N/0197 is: the length of concrete 152mm. significant voids noted throughout, particularly near the reinforcement. Thick cementitious repair to the front face to the depth of reinforcement approximately 70mm deep. 2 layers of steel reinforcing, one at the front and one at the back back concrete faces approx. 50mm depth from the core ends. Beca // 13 May 2014 // Page 9

13 Both samples indicate significant removal and repair of the internal concrete face of the pool shell wall at some stage at this location. The reason for the repair is not known. The reinforcement is in good condition, with little corrosion evident. This repair and significant voids are generally consistent with the observed leakage through the pool shell wall at this location. The voids may have been formed due to poor concrete compaction practices during construction, possibly at a cold concrete joint. This area requires repair. A further 7 core samples were taken from the east and west walls and 10 cores were taken from the floor slabs. Core samples obtained from the walls ranged in length from 81 to 265mm, noting that these core lengths may be less than the thickness of the wall. Core samples obtained from the floors ranged in length from 110 to 179mm, noting that these core lengths maybe less than the thickness of the floor. The test results (apart from laboratory samples 14/N/0196 and 14/N/0197 discussed above) indicate that the concrete shell is generally in a satisfactory condition for its age and form of construction, noting that the quality of construction was generally of a high standard. Should the pool be recommissioned without a liner, it is recommended that at the location of the water ingress through the wall, the existing repair material is removed, the substrate cleaned and primed and the wall repaired with an epoxy mortar. Beca // 13 May 2014 // Page 10

14 Photo 5 Photograph of Laboratory Sample 14/N/0196 Provided that the recommended structural repair work is undertaken and preventative and reactive maintenance is undertaken in a diligent manner, the test results indicate that the pool shell can remain serviceable in the medium term. Beca // 13 May 2014 // Page 11

15 Photo 6 Photograph of Laboratory Sample 14/N/ Recommendations 6.1 Works Required For Non Liner Option Should the concrete pool shell be recommissioned without the liner option, the following works are recommended to extend its service life in the medium term. 1. Structural repair of wall cracks, in particular the vertical crack at the climb-out return midway along the east side long wall. 2. Structural repair of the porous concrete at the west wall at the deep end. 3. Structural epoxy repair of the recent cracks located in the floor panels. 4. Installation of a hydrophilic waterstop and top sealant in the floor joints. Beca // 13 May 2014 // Page 12

16 5. Undertake a leak test to confirm that the recent major leak has been remedied. This will require the pool to be filled at the completion of the structural repair work. The pool may need to be reemptied and additional locations repaired if further leaks are discovered. 6. Pressure clean, prepare and repaint the pool shell. The following ancillary works in addition to the above listed works are required to minimise leaks and reduce the risk of future structural damage due to a high surrounding groundwater table. These items should be undertaken prior to the structural repairs outlined above to ensure that groundwater does not affect the repair work. 7. Repair all hydraulic pipework, identified as being the FWR lines at the deep end and the SWS line. 8. Unblock groundwater relief drains. These recommendations pertain solely to improving the structural integrity of the pool shell. For budgetary purposes an allowance of $100,000 is recommended. 6.2 Works Required For Liner Option Should the concrete pool shell be recommissioned with a liner, the works relating to structural crack repair are not essential provided the future service life of the pool is viewed as being medium term. It is essential however, that risk of damage to the liner or the formation of bubbles behind it that can be caused by the surrounding groundwater table is mitigated. The following works are recommended: Item 7 above. Item 8 above 9. Significant works to improve the groundwater relief drain system to ensure that the groundwater level remains below the bottom of the pool floor at all times. 10. Probable improvement to the soiled water supply line capacity to ensure the level of the pool water does not rise over the top of these inlets. 11. Preparation of the concrete pool shell surface. 12. Works at the liner penetrations. 13. Works at the termination level of the liner. These recommendations pertain solely to improving the structural integrity of the pool shell prior to the supply and installation of a liner. For budgetary purposes an allowance of $80,000 is recommended, excluding the cost to supply and install the liner. In addition to these works, it is recommended that Council investigate the following issues: Detailed investigation of the pool plant and hydraulic pipework arrangement to confirm water quality and turnover rates for design bather loads to comply with Health Regulations Occupational health and safety. Equal access (DDA). Aquatic Facility Safety Assessment. The condition and serviceability of outbuildings. These issues may drive changes to the configuration of the pool shell such as a reduction in depth or the addition of a wet deck. Beca // 13 May 2014 // Page 13

17 7 Conclusion Beca s site inspection and the concrete testing undertaken by Sharp and Howells indicates that apart from some significant specific defects requiring repair as noted in Section 6, the concrete shell is generally in a satisfactory condition for its age and form of construction, noting that the quality of construction in 1964 was generally of a high standard. The hydraulic pipework pressure testing undertaken by Australian Leak Detection indicates that repair and/or replacement of some of the pipework is required, notwithstanding that on completion of a hydraulic review, replacement maybe required in any case due to the pipework being undersized. In order to re-commission the concrete pool shell, an allowance of $100,000 is recommended. Should the installation of a liner be considered, and an allowance of $80,000 to prepare the pool shell and associated pipework is recommended. This does not include an allowance for the supply and installation of the liner. Holistically, the pool shell structural repair work needs to be considered in conjunction with all other compliance issues that directly impact on the operation and health and safety of the pool operators and the pool customers. It is recommended that Council investigate the following issues: Detailed investigation of the pool plant and hydraulic pipework arrangement to confirm water quality and turnover rates for design bather loads. Upgrade of these items and the inclusion of a balance tank is often required for pools of this era. Occupational health and safety. Equal access (Disability Discrimination Act). Aquatic Facility Safety Assessment. The condition and serviceability of outbuildings. On completion of these activities, a complete understanding of the upgrade needs of the facility can then be determined. Beca // 13 May 2014 // Page 14

18 Appendix A Sharp and Howells Concrete Test Report

19 Appendix B Infracorr Electrochemical Potential Testing Report