Title
a. Approve Change Order No. 4 to the contract with Graniterock Company for Nacimiento Dam spillway repair work to extend the contract term to September 30, 2020; and
b. Approve Change Order No. 4 to the contract with Graniterock Company for San Antonio Dam spillway repair work to extend the contract term to September 30, 2020; and
c. Authorize the General Manager to execute both Change Orders.
Report
RECOMMENDATION:
It is recommended that the Monterey County Water Resources Agency Board of Directors:
a. Approve Change Order No. 4 to the contract with Graniterock Company for Nacimiento Dam spillway repair work to extend the contract time to September 30, 2020; and
b. Approve Change Order No. 4 to the contract with Graniterock Company for San Antonio Dam spillway repair work to extend the contract term to September 30, 2020; and
c. Authorize the General Manager to execute both Change Orders.
SUMMARY/DISCUSSION:
Nacimiento and San Antonio Dams are regulated with regard to dam safety matters by the California Department of Water Resources, Division of Safety of Dams (DSOD). Nacimiento Dam is also regulated by the Federal Energy Regulatory Commission (FERC) due to the hydroelectric plant at the dam.
After the 2017 Oroville Dam spillway incident, DSOD and FERC directed the Agency (and all high hazard dam owners) to submit Work Plans for spillway work needed before the 2017-18 winter, conduct a focused spillway inspection, and submit a Spillway Condition Assessment Report. Graniterock Company was hired in late 2017 to compete the Work Plans for Nacimiento and San Antonio spillways under Agency Board of Director’s recommendation (September 18, 2017), and Agency Board of Supervisor’s authorization of the General Manager to enter into a construction contract on an emergency basis for immediate repairs to the spillways (September 26, 2017).
A San Antonio Dam Spillway Condition Assessment Report was submitted to DSOD in May 2018, and a Nacimiento Dam Spillway Condition Assessment Report was submitted to DSOD and FERC in July 2018. The reports recommend additional work to both spillways. A scope of work addressing report recommendations for Nacimiento Dam spillway was submitted to DSOD and FERC in July 2018. DSOD and has provided approval to proceed. FERC requested revisions to the Nacimiento Dam Spillway Repair Scope of Work, which have been made and re-submitted to FERC for approval.
Change Order No. 4 to the Nacimiento contract extends the contract time to allow Graniterock Company to proceed with spillway work contained in the revised Nacimiento Dam Spillway Scope of Work when approved by FERC. The Scope of Work includes:
• Borescope exploration (drill ¾” diameter hole and insert camera) into and below spillway concrete chute slabs to indicate concrete condition and search for voids, and fill drill-hole with grout;
• Seal moving cracks, non-moving cracks, and fine cracks in spillway concrete chute;
• Repair delaminated spillway chute concrete; and
• Repair concrete spalls
Quality control and inspection of the work performed by Graniterock will be conducted by Agency staff or a qualified consultant. FERC approval is expected to be received in September 2019, and work is being planned to begin in early October 2019. Borescope exploration investigates presently unknown conditions under the spillway chute that may result in additional repair work. Therefore, Change Order No. 4 extends the time to Substantial Completion by 12 months to September 30, 2020.
Change Order No. 4 to the San Antonio contract extends the contract time to allow Graniterock Company to proceed with underdrain exploration work, repair a broken drainpipe and seal wall joints. This Change Order time extension of 12 months coincides with the Nacimiento Dam contract time extension to allow coordination of work timing at both spillways.
OTHER AGENCY INVOLVEMENT:
DSOD has approved work plans for Nacimiento Dam spillway and San Antonio Dam spillway. FERC must approve the revised scope of work for Nacimiento Dam spillway.
FINANCING:
Monies are available from FY 2019-20 Fund 116 - Nacimiento Dam Operation and Maintenance.
Prepared by: Chris Moss, Senior Water Resources Engineer, (831) 755-4860
Approved by: Brent Buche, General Manager (831) 755-4860
Attachments:
1. Change Order No. 4 for Nacimiento
2. Copy of Change Order Nos. 1, 2 and 3 for Nacimiento
3. Copy of 2017 Nacimiento Dam Spillway Emergency Repairs Project Time and Materials Contract
4. Change Order No. 4 for San Antonio
5. Copy of Change Order Nos. 1, 2 and 3 for San Antonio
6. Copy of 2017 San Antonio Dam Spillway Emergency Repairs Project Time and Materials Contract
7. Board Order