Title
Approve Change Order No. 12 to the contract with Graniterock Company for Nacimiento Dam spillway repair work to increase the contract amount by $400,000; and authorizing the General Manager to execute the Change Order.
(Staff: Mark Foxworthy)
Report
RECOMMENDATION:
It is recommended that the Monterey County Water Resources Board of Directors:
Approve Change Order No. 12 to the contract with Graniterock Company for Nacimiento Dam spillway repair work to increase the contract amount by $400,000; and authorize the General Manager to execute the Change Order.
SUMMARY/DISCUSSION:
Graniterock Company has performed repair work at Nacimiento Dam spillway in 2017, 2018, 2019, 2020, 2021 and 2023 in accordance with Federal Energy Regulatory Commission (FERC) and California Dept. of Water Resources, Division of Safety of Dams (DSOD) approved Scopes of Work consisting of delaminated concrete removal and replacement, concrete spall repair, sealing concrete slab joints, grinding concrete slab joint offsets, assisting with borescope exploration under concrete chute slabs, and concrete crack repair. The original contract with Graniterock Company to begin emergency spillway repairs was executed in 2017. Eleven change orders have been executed to continue repair work over multiple fiscal years, paying $1,074,034.27 for spillway repair work since 2017.
The spillway chute is designed to be fully supported by the rock foundation. Non-destructive testing to evaluate concrete contact with the rock foundation was performed in 2018, and locations indicating possible void spaces under the spillway chute concrete were found. The FERC approved Spillway Repair Scope of Work included boring small diameter holes through the spillway chute concrete to visually observe concrete/foundation contact conditions. In 2019, 45 boreholes were drilled, and conditions documented. An area 5 feet x 40 feet under spillway chute concrete Panel 14R was found to be suspended above the rock foundation, a condition it is not designed for. Plans and specifications have been submitted to, and approved by, FERC and DSOD for removal and replacement of the concrete chute in this area. Change Order #9 increased the amount of the contract with Graniterock Company by $769,700 to remove the suspended portion of spillway chute concrete Panel 14R, replace it upon firm foundation. Timing of approval to proceed delayed work on the spillway planned to occur in 2022. Construction of an access road on the south side of the spillway near panel 14R was completed in 2022 in support of Panel 14 R repairs but was underestimated. Change Order #10 extended the term of the contract to allow completion of Panel 14R repairs in 2023 under the current contract. Execution of Change Order #11 brought the contract total with Graniterock Company for Nacimiento Dam spillway repair to $1,581,217 to ensure completion of work on Panel 14R in conformance with approved plans and specifications and completed by November of 2023. The repairs to Panel 14R were delayed due to the unavailability of the contractor to mobilize and complete the repairs ahead of the 2023 rainy season Execution of Change Order #12 will bring the contract total with Graniterock Company for Nacimiento Dam spillway repair to $1,981,217 to ensure completion of work on Panel 14R and ongoing annual spillway maintenance ahead of this year’s anticipated rainy season.
No other change orders are anticipated, and this contract will expire December 31, 2024.
OTHER AGENCY INVOLVEMENT:
Plans and Specifications for repair of spillway chute Panel 14R must be approved by FERC and DSOD. Plans and Specifications were submitted to FERC and DSOD on April 21, 2022.
FINANCING:
Panel 14R Repairs- $753k payable from FY 2023-24 Fund 116 - Nacimiento Dam Operation and Maintenance; Potentially payable from $6.1mil in State Funding through DWR.
Annual Spillway Repairs- $150k payable FY2023-24 Fund 116 Nacimiento Operation and
Maintenance
Prepared by: Mark Foxworthy, Interim Senior Water Resources Engineer (831) 755-4860
Approved by: Ara Azhderian, General Manager (831) 755-4860
Attachments:
1. Change Order No. 12
2. Change Order Nos. 1 through 11 to Graniterock Contract for Nacimiento Dam Spillway
3. 2017 Nacimiento Dam Spillway Emergency Repairs Project Time and Materials Contract
4. Board Order