TO: Board of Supervisors
FROM: Steven Lederer - Director of Public Works
REPORT BY: Dewey Phan, Assistant Engineer
SUBJECT: Approve Amendment #3 to Professional Services Agreement No. 210301B with ADKO Engineering for RDS 21-30 and approval of Plans and Specifications for the Storm Slide Repairs at Dry Creek Road MPM 6.2, 9.48, 9.75, and Diamond Mountain Road MPM 1.1.
RECOMMENDATION
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Director of Public Works requests the following actions:
1. Approval of the plans and specifications and authorization to advertise for sealed bids and opening of the bids at a time, date, and location to be published by the Director of Public Works pursuant to Section 20150.8 of the Public Contract Code for the following projects:
a. Dry Creek Road MPM 6.2, RDS 21-30
b. Dry Creek Road MPM 9.48, RDS 21-39
c. Dry Creek Road MPM 9.75, RDS 21-06
d. Diamond Mountain Road MPM 1.1, RDS 21-04
2. Approval of and authorization for the Chair to sign Amendment No. 3 to Agreement No. 210301B with ADKO Engineering (ADKO) increasing maximum compensation by $23,609 for a new maximum of $498,054 adding Dry Creek MPM 6.2 Storm Slide Repair to their scope.
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EXECUTIVE SUMMARY
In 2017 a series of storms caused significant damage at several locations, including the following project sites:
1. Dry Creek Road mile post marker (MPM) 9.75 - Sustained about 70 feet of embankment failure;
2. Diamond Mountain Road MPM 1.1 - Sustained about 50 feet of roadway and embankment failure.
Another site, most likely a result of the 2019 rains, was discovered at Dry Creek Rd. MPM 9.48, where 15 feet of roadway and embankment failure occurred. During later heavy rains, Dry Creek eroded the creek bank next to Dry Creek Road MPM 6.2, causing two significant slides and other damage. At this location, two separate retaining walls are being designed to repair the existing slide areas. Due to the potential susceptibility of a future slide in the area between ...
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