The Lennox City Council voted to not open the Lennox swimming pool for the season at a special meeting held Thursday, May 25. The council was first made aware of exposed cracks at the pool during a special meeting on May 4, one crack in particular caused concern. Over the course of the next several weeks geo core and structural studies were done. It was at Thursday’s meeting the final report from Rise Structural Associates Inc. was presented. City Engineer Mitch Mergen from Stockwell Engineers was at the meeting to address the council.
The report described the field data: “A large crack is present roughly parallel with the east side and extends for nearly the full length of the shallow end. The crack appears to be full depth (Le. 6”±) for the majority of its length. Previous repair efforts are evident. There are three locations along the crack with surface spalls. There is a large (approximately 2’ x 4’) surface spall at the south end of the crack. Within this spall a small approximately 4” x 8” hole is present. Less severe cracking (those designated as small cracks on the map) is present throughout the west half of the floor. There is a spider web of patched cracks in the northeast quadrant. Surface delamination has occurred over approximately 25 percent of the floor.”
The analysis and recommendation in the final report from Rise stated: “We concur with the conclusion reached by Geotek that the subsurface soils are the cause of the floor slab distress. To reiterate, the clay soil is moderately to highly frost susceptible and the fat clay is somewhat expansive. Freeze/thaw cycles in combination with the effects of expansive pressure exerted by the fat clay soil has caused movement over the life of the pool. The slab was not designed to resist this pressure thus cracks developed to relieve the internal stresses. Surface spalls are the result of pool chemicals penetrating the slab through very small cracks, reacting with the reinforcing steel and initiating the process of corrosion. As the reinforcing expands due to the corrosion, pressure is exerted causing a phenomenon termed blow-out which results in surface spalls.
“We understand there is a desire to apply a temporary ‘patch’ to the large crack in order to allow the pool to be used this season. In discussions with several manufacturers of concrete repair products we have found that no product is available to effectively plug the crack without extensive rehabilitation work that typically involves the complete removal and replacement of that section of the slab containing the crack. All the product suppliers we talked to would either not recommend or warrant their product without first repairing the crack. It is our opinion any concrete rehabilitation work is not justified or recommended without addressing the cause of the distress which is the underlying clay soils. Distress (cracking) will likely continue under the present soil conditions.”
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