DEPARTMENT: Transportation
FILE TYPE: Consent Action
TITLE
title
Authorization To Execute Third Contract Amendment With Alliant Engineering, Inc., For Professional Engineering Services For County Road Retaining Wall Assessments And Final Design Of County State Aid Highway 38 (McAndrews Road) Retaining Walls, County Project 97-218
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PURPOSE/ACTION REQUESTED
Authorize execution of the third contract amendment with Alliant Engineering, Inc. to complete additional engineering design services required to address newly identified site constraints, structural design complexities, and extended project coordination necessary for the successful delivery of County Project (CP) 97-218.
SUMMARY
Dakota County is advancing CP 97-218 to analyze, repair, and replace deteriorating retaining walls along County roadways to maintain safe and reliable infrastructure. Twenty-four retaining walls have been evaluated to determine condition, prioritize repairs, and support capital planning needs. Four priority walls along County State Aid Highway (CSAH) 38 were advanced into final design due to documented deterioration and the potential for impacts to roadways and bike/pedestrian facilities (Attachment: Location Map).
During design development, significant and unanticipated physical constraints were encountered, including extraordinary wall height, reduced construction areas, sightline limitations, and the need to avoid private property impacts. These conditions required substantial modification to the original scope, including extensive geotechnical review, specialized structural design, and multiple design iterations to ensure constructability within the County's right of way.
As walls 11 and 14 presented more complex design challenges, the project team determined that separate plan sets would be required for walls 12/13 and walls 11/14. TKDA was added as a subconsultant to provide specialized structural engineering and quality control for these advanced design elements. These ...
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