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A3.1 reservoir apr8 2014
- 1. RESERVOIR PLANNING STUDY: A COMPREHENSIVE ASSESSMENT OF EVANSTON’S WATER STORAGE NEEDS Presentation to City Council April 8, 2014
- 2. Reports Completed to Date • CTL Group’s structural evaluation of 1913 facilities (2010) • CTL Group’s structural evaluation of 1934 Reservoir and 1948 Settling Basins No. 1 & 2 (2012) • CDM Smith’s review of CTL Group’s report on 1934 reservior (2013) • CTL Group’s Inspection of 1934 Reservoir (2013) • CDM Smith’s 1934 Reservoir Inspection Report (2013) • Walker Restoration Consultants1934 Reservoir Roof Slab Report (2013) prepared for Northwestern University
- 3. Reason for Current Study • Comprehensive evaluation of several factors: Finished water storage requirements Water treatment requirements Efficient pump operation Recommendations based on decision criteria: Industry best management practices Age and deteriorated condition of existing structures Life cycle cost for repair and / or replacement
- 4. Reason for Current Study • Complete a life cycle cost analysis to weigh short-term repairs against long-term solutions. Repairing the reservoir would extend its life by 20 years maximum Compare long-term financial impacts of building a new reservoir now or in 20 years Is it cost-effective to invest millions of dollars rehabilitating the 1913 and 1923 facilities when the concrete structures are likely at the end of their useful life?
- 5. Existing Condition of Storage Facilities Evanston’s water storage is provided by five facilities that must be evaluated together: Storage Facility Gross Storage (MG) Year of Construction Condition West Plant Clearwells 2.4 1913 and 1923 Poor East Plant Clearwells 2.0 1948 and 1964 Unknown Finished Water Reservoir 5.0 1934 Poor South Standpipe 5.0 1984 Good North Standpipe 7.5 1986 Good
- 6. Water Plant Structural Evaluations and Concerns 1913 1923 1934 1948
- 7. 1913 Clearwells Existing Condition Vertical and horizontal wall cracks are prevalent inside the clearwells
- 8. 1913 Clearwells Existing Condition Cracking was also found on the outer clearwell wall faces and in the filter walls above the clearwells
- 9. 1913 Clearwells Existing Condition “It is CTLgroup’s opinion that the most reliable method to repair the clearwell cracks and eliminate infiltration would be to 1) excavate to expose all roof and wall surfaces, 2) execute full- thickness crack repairs, and 3) apply a water proof coating to all exterior surfaces. However, given the highly-invasive nature of such a repair, it is questionable whether such measures would be considered practical” John J. Roller, CTL Group, registered professional engineer and registered structural engineer in the state of Illinois.
- 10. 1934 Reservoir Existing Condition • CTL Group found cracks throughout the underside of the roof slab in their 2012 inspection • Walker Restoration Consultants found “near disintegration” of the top 1.5 – 2 inches of the roof slab in their 2013 inspection
- 11. 1934 Reservoir Existing Condition Steel rebar is exposed and corroded in many locations on the roof slab
- 12. 1934 Reservoir Existing Condition CDM Smith’s 2013 report states of the 1934 Reservoir: “Given that this concrete structure is about 80 years old, the rate of deterioration and degradation is expected to be accelerating for the remainder of its useful life. Under normal conditions, the average expected useful life of a concrete structure is about 100 years. This life span can be significantly reduced if the concrete structure is subject to constant high humidity and repeated freeze-thaw cycles. This is exactly the case for the finished water reservoir, especially for the roof slab of the reservoir. Therefore, …it is probable that the useful life of the walls and the floor slab will not exceed 100 years.” Wendell Yang, CDM Smith, registered professional engineer (1983) and registered structural engineer (1985) in the state of Illinois.
- 13. QUESTIONS?
- 14. Study will consider six alternatives • 1 – Replace 1934 Reservoir roof and modify to use entire volume, repair 1913/1923 Clearwells • 2 – Replace 1934 Reservoir in existing footprint, repair 1913/1923 Clearwells • 3 – Replace 1934 Reservoir in larger footprint, decommission 1913/1923 Clearwells • 4 – Construct a new clearwell on the east side of Sheridan Road, decommission 1934 Reservoir • 5 – Construct a new reservoir and pumping station at Leahy Park • 6 – Repair 1934 Reservoir roof and modify to use entire volume, repair 1913/1923 Clearwells
Editor's Notes
- We called this a Reservoir Planning Study because the most immediate concern and most expensive component is the 1934 Reservoir. However, this is really a comprehensive study of all of Evanston’s water storage facilities, how they operate together, and how much storage we need based on water system operations and contractual requirements to our wholesale customers.
- In 2008 as the filter shop area was being constructed, unexpected damage occurred to the concrete structure. In 2009 the Department raised concerns about the structural integrity of the concrete in several locations of the treatment plant. Visual inspection of the older filter areas showed signs of concrete failure. Council members toured the plant facility and they were taken to the old filter areas to observe some of the conditions and concerns. CTL was awarded the first 2 studies based on responses to RFPs 10-75 ($56,250) and RFP 12-158 ($89,000) CTL’s study expressed immediate concern of the reservoir roof slab, since this was the first time the reservoir had been inspected. CDM was asked to review the CTL report, confirm the estimated cost to repair, and provide more information about the probable duration of the work and impact to the water treatment processes if the reservoir was taken out of service. Based on reports and concern that vehicles and snow load on reservoir might cause a problem, NU was advised of situation. They then hired Walker who did inspection in November with report dated December 2013. CTL re-inspected the reservoir again in 2013 ($20,000) and CDM also participated in the 2013 inspection ($24,262 for both reports and to participate in inspection) The 2013 inspection revealed that there was no significant deterioration between the 2012 and 2013 inspection.
- The overall goal of the department was to complete the structural evaluation of the concrete for the facilities built at different times. The Department had programed funding for concrete repairs in the CIP based on the reports. However, the findings that the 1913 (and assumed 1923) facilities as well as the 1934 facility are in such poor structural condition a comprehensive plan on how to approach the issues based on
- At the very least, we are facing an investment of several million dollars to repair the reservoir roof and the 1913/1923 clearwells, as well as to modify the reservoir in order to be able to use the entire volume. The analysis will determine whether it is cost-effective to invest millions of dollars in structures that are already at or near the end of their useful life, or if there is a more cost-effective option that will provide us with a reservoir that can last another 80-100 years. Furthermore, we know that IEPA loan and government bond interest rates are favorable now. We do not know if they will still be favorable in 15-20 years. The study will consider the uncertainty in future lending terms and factor that into the life cycle costs. With the completion of the parking garage, Northwestern will no longer need to use the reservoir top as a parking lot. Plans for that space include anything from tennis courts to a new sports facility.
- 1913 clearwell walls and bottom slab are known to be in poor condition and the roof slab has not undergone structural testing, but is assumed to be in the same condition as the 1934 reservoir roof slab since it is made of the same non-air-entrained concrete and exposed to the same conditions. Not only concerned with concrete, but also of valves and design By wholesale contracts, must equitably apportion the water stored at the plant in the event of emergency Evanston avg daily demand is 8 MG, therefore should have 16 MG storage (2 days). 12.5 in standpipes but only 3.1 at plant for total of 15.6. And this assumes that the structures are full and that they can be completely drained. Standpipes are scheduled to be painted in 2014 & 2015. would want them in service prior to doing any work at the plant
- The 1913 filtration plant (clearwells and filters) was inspected in 2010 by CTL Group. Significant structural deterioration was found. The adjacent 1923 filtration plant has not yet been inspected, but it is assumed to be in similar condition since it was constructed of the same non-air-entrained concrete as the 1913 plant. The 1934 reservoir and 1948 settling basins (No. 1 & No. 2) were inspected in 2012 by CTL Group. The settling basins are in good condition, with only minor defects found. The reservoir walls and floor slab showed deterioration, but nothing immediately concerning given the structure’s age. The reservoir roof showed significant deterioration in the 2012 inspection. Cores taken from the roof demonstrated that the slab was cracked throughout its entire thickness. The follow-up inspection in 2013 showed little change, meaning the slab should remain safe in the near-term. However, three consultants (CTL, CDM Smith, and Walker) have all recommended extensive rehabilitation or complete replacement of the slab within the next five years to prevent structural failure.
- CTL Group conducted a structural inspection of the entire 1913 facility in 2010. Cores were taken from the walls but not the roof slab. However, the roof slab is only 4” thick and has been subject to the same freeze/thaw damage as the 1934 Reservoir, so it is assumed to be in similar condition.
- Significant efflorescence on the outer clearwell wall face (as viewed from the adjacent pipe gallery) indicates moisture is getting through the walls through a significant horizontal crack visible at the top of this patch of efflorescence. Several vertical wall cracks are visible in the wall of Filter #2 above the clearwells.
- Cores were not taken from the roof slabs at the time of this study. Based on the findings at the 1934 Reservoir, it is likely the clearwell roof slab would have the same severe deterioration to the point where major rehabilitation or complete replacement of the roof slab would be warranted. CTL’s cost estimate for injecting resin into the cracks from the interior of the clearwells, plus other structural repairs needed in the 1913 facility, was almost $1 million in 2010. A major rehabilitation or complete replacement of the clearwell roof slabs would add several million dollars to the cost.
- Again, not only concerned about the concrete structure but also the valves, piping and design. The current reservoir has 48” pipe running through it. It does not have any baffling to ensure there is no short circuiting of the water and it has not wet well which would allow for complete draining of the structure.
- Conclusion: Repair or replacement of the reservoir roof slab will extend the life of this structure by 20 years at most. At that time we will have no alternative but to construct a new reservoir at increased cost.
- Alt. 1 is a temporary fix and would work only if it is determined that no additional storage is needed beyond being able to use the entire 5 MG. A new reservoir/clearwell would be needed within 20 years. Alt. 2 is for comparison to Alt. 1, to compare the life cycle cost of replacing the reservoir in kind today versus doing it in 15-20 years. Alt. 3 would require negotiation with NU, though it is certainly a possibility depending on NU’s future plans for North Campus. Alt. 4 would require the City purchase the Fahner residence at 2437 Sheridan Road, but at the same time perhaps there would be some offsetting concessions by Northwestern in exchange for relinquishing the City’s rights to the current reservoir site. Alt. 5 is a less ideal scenario from an operational perspective, but would provide much more area to work with in the case we need significantly more storage volume. Alt. 6 is similar to Alt. 1 except it involves rehab of the roof slab in place rather than complete replacement of the roof slab. This alternative was added to the scope by addendum on February 2, 2014, after the Utilities Dept. received a report from Northwestern’s structural consultant (Walker) proposing the procedure. As with Alt. 1, this is only a temporary fix.