Broken Arrow City Council
Meeting of: 01-19-2016
To: Mayor and City Council
From: Office of the City Attorney
Title:
title
Presentation, consideration, and discussion on the Hillside Park Retaining Wall (Tiger Hill - southwest corner of Kenosha Street and Lynn Lane), including recommendations on repairs, remediation or possible replacement of the wall, and possible action including direction to pursue a particular design of wall remediation
End
Background:
Following the partial collapse of the Flight Safety retaining wall on the east side of Tiger Hill, Department of Engineering and Construction Staff recommended evaluation of the City's retaining wall. The Acting City Manager approved a contract with Olsson Associates, Inc., a Kansas Architectural and Engineering firm that specializes in segmental block retaining walls, to conduct a geotechnical investigation of the wall.
The report provided general recommendations for remedial action to prevent failure of the wall, but did not explore in detail all possible courses of action. As Olsson's report was very comprehensive and unquestionably laid the foundation for engineering design solutions, their firm was the logical choice to design remediation, repair, or replacement of the wall. On November 19, 2015, the City Council approved a Professional Services Contract with Olsson.
On December 18, 2015, Engineering Staff received the repair recommendations for the retaining wall. Importantly, this correspondence stated that the existing wall design does not meet the several minimum standards of the National Concrete Masonry Association. Specifically, the design and construction deficiencies identified included the following:
* The blocks do not provide enough resistance to resist internal sliding, pullout and facing stability failures.
* At the taller sections, the tensile capacity of the geogrid does not provide an adequate factor of safety against breakage.
* The global anal...
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