Title
Resolution to Approve Amendment No. 1 to the Professional Services Agreement with NTH Consultants, Ltd. for the Barton Dam Piezometer Installation and Slope Stability Analysis Project - RFP989 ($ 26,400.00)
Memorandum
This memorandum and resolution requests approval of Amendment No. 1 to the professional services agreement for professional engineering services with NTH Consultants, Ltd. Council approved a professional services agreement for $189,400.00 with NTH Consultants in February 2017 as part of Resolution No. R-17-047.
The City is seeking to amend the professional services agreement with NTH Consultants to accommodate additional professional engineering services based on initial field exploration of an observed sinkhole at Barton Dam on the embankment. An approximately 4" dia. x 18" deep sinkhole was discovered on top of the embankment near the Barton Dam concrete spillway on April 7, 2017. The dam impounds the Barton Pond, which serves as the source of 85% of the City's raw water. The sinkhole represents a potential dam safety issue.
NTH conducted an initial site visit after a sinkhole was discovered during a routine inspection of the Barton Dam embankment. NTH performed a field evaluation, testing and recommended temporary remedial measures. The additional scope that comprises this amendment includes providing further investigation and evaluation of the sinkhole, developing recommendations for permanent remedial action, as well as providing support, coordination and report preparation for the Federal Energy Regulatory Commission (FERC) who regulates the dam.
The original scope of this project included installing additional piezometers, collecting piezometer data, performing a stability analysis of the embankment, developing recommendations for remediation, and coordinating and responding to FERC. The scope of work in this Amendment consists of non-destructive subsurface soil exploration, dye testing, inspection of dam components, assessing...
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