To: Board of Supervisors
Department or Agency Name(s): Sonoma County Public Infrastructure
Staff Name and Phone Number: Johannes J. Hoevertsz, 707-565-2550
Vote Requirement: 4/5th
Supervisorial District(s): Fifth
Title:
Title
Wohler Road Bridge over the Russian River Seismic Retrofit Project, C01136, Construction Contract Change Order and Construction Contract Increase
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Recommended Action:
Recommended action
Approve and authorize the Director of Sonoma County Public Infrastructure to execute a construction contract change order in the amount of $665,500 and approve an increase in the Wohler Road Bridge over the Russian River Seismic Retrofit Project construction contract amount by a total of $3,000,000 for a new, total, not-to-exceed contract amount including contingencies of $22,794,083.
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Executive Summary:
The Department of Public Infrastructure (SPI) requests Board approval of construction Contract Change Order (CCO) fifteen (15) in the amount of $665,500 on the Wohler Road Bridge over the Russian River Seismic Retrofit Project (C01136). CCO fifteen is required to pay for dewatering work necessary to complete the foundation construction of pier four. If approved, this CCO in conjunction with CCO fourteen (14) approved by the Board on December 16, 2025, will increase the total contract amount by $3,000,000, for a new, total, not-to-exceed contract amount including contingencies of $22,794,083.
Discussion:
The Wohler Road Bridge Seismic Retrofit Project (Project) is the largest and most complex bridge project undertaken by the County of Sonoma to date. The Project retrofits the existing historical, seismically deficient one-lane Wohler Road Bridge (Bridge Number 20C-155), with a new lightweight concrete deck, seismic isolation bearings, steel truss reinforcement, and foundation reinforcement.
On February 6, 2024, the Board awarded a construction contract for the Project to Ghilotti Construction Company, Inc. in the amount of $17,994,621, and authorized a 10% contingency in the amount of $1,799,462, for a total not-to-exceed contract amount of $19,794,083.18. On December 16, 2025, the Board authorized the Director of Sonoma Public Infrastructure to execute CCO fourteen (14) up to the amount of $2,300,000 due to differing site conditions and schedule acceleration.
In this item, SPI is requesting authority to execute Contract Change Order (CCO) fifteen (15) in the amount of $665,500 to pay for changed dewatering operations in order to complete Pier 4 foundation construction. At the time of bid, the Contractor reasonably assumed that dewatering could be performed using an Active Treatment System (ATS) with treated discharge at approved locations. Following contract award, the Contractor submitted an ATS system for approval. During regulatory review, the North Coast Regional Water Quality Control Board (NCRWQCB) determined that groundwater in the vicinity of the proposed discharge locations may be used for domestic drinking water, and that discharge of treated water from an ATS posed a potential risk of drinking water contamination. As a result, the Water Board disallowed use of the ATS system for Pier 4 dewatering operations. This restriction was not disclosed in the Contract Documents and was identified only after ATS submittal, constituting a change in conditions beyond the Contractor’s reasonable bid assumptions. As a direct result of the ATS disallowance, the Contractor was required to implement a dewatering system utilizing water storage tanks and off-hauling groundwater to approved off-site treatment facilities.
This item also includes a request to increase the construction contract amount by a total of $3,000,000 for a new, total, not-to-exceed contract amount including contingencies of $22,794,083. This request accounts for the $665,500 requested in this Board Item in addition to the $2,300,000 approved by the Board on December 16, 2025, and all other CCOs approved by the Director of SPI under delegated authority within the original 10% contract contingency amount.
Funding for the construction project is 88.53% Federal Highway Administration (FHWA) funds administered by Caltrans. SPI has conferred with Caltrans during the project, received assurance the costs are reimbursable and has submitted a request for reimbursement for this contract change order.
Strategic Plan:
This item directly supports the County’s Five-year Strategic Plan and is aligned with the following pillar, goal, and objective.
Pillar: Resilient Infrastructure
Goal: Goal 3: Continue to invest in critical road, bridge, bicycle, and pedestrian infrastructure.
Objective: Objective 1: Continue to maintain road segments, including designated turnouts where feasible, increase efforts on vegetation removal and drainage features, and improve pavement conditions in neighborhoods.
Racial Equity:
Was this item identified as an opportunity to apply the Racial Equity Toolkit?
No
Prior Board Actions:
12/16/2025: Board authorized SPI Director to execute construction contract change order for differing site conditions and acceleration in an amount up to $2,300,000
2/06/2024: Board awarded project construction contract to Ghilotti Construction Company, Inc.
12/07/2021: Board approved Third Amendment to the design contract with Dewberry Engineers, Inc.
5/15/2020: Board adopted an Addendum to the Mitigated Negative Declaration
7/10/2018: Board approved Second Amendment to the design contract with Drake Haglan and Associates, Inc.
5/24/2016: Board approved First Amendment to the design contract with Drake Haglan and Associates, Inc.
11/24/2014: Board adopted a Mitigated Negative Declaration and Mitigation Monitoring Program and approved the Project
9/24/2013: Board approved design contract with Drake Haglan and Associates, Inc.
Fiscal Summary
|
Expenditures |
FY25-26 Adopted |
FY26-27 Projected |
FY27-28 Projected |
|
Budgeted Expenses |
$ 1,878,450 |
$7,513,802 |
|
|
Additional Appropriation Requested |
|
|
|
|
Total Expenditures |
$1,878,450 |
$7,513,802 |
|
|
Funding Sources |
|
|
|
|
General Fund/WA GF |
|
|
|
|
State/Federal |
$1,662,992 |
$6,651,969 |
|
|
Fees/Other |
$215,458 |
$861,833 |
|
|
Use of Fund Balance |
|
|
|
|
General Fund Contingencies |
|
|
|
|
Total Sources |
$1,878,450 |
$7,513,802 |
|
Narrative Explanation of Fiscal Impacts:
As of February 2026, $13,401,831 of work had been performed on this contract. If the new, not to exceed contract amount of $22,794,083 is approved by the Board the remaining balance of $9,392,252 will be expended in calendar year 2026. Appropriations for expected contract costs in FY 2025-26 are available in the Roads Capital (11051-34010103) Adopted Budget and appropriations for FY2026-27 planned expenditures will be included in the FY 2026-27 Roads Capital Recommended Budget.
The project is eligible for 88.53% reimbursement through the Federal Highway Administration (FHWA). SPI has applied for reimbursement of these expenditures, but the application has not yet been approved. In the even the application is denied, the Department would use annual allocations from traditional Road funding sources such as the Highway User Tax Account (HUTA) or the Road Maintenance and Rehabilitation Account (SB1) to pay for the additional contract costs.
Narrative Explanation of Staffing Impacts (If Required):
None.
Attachments:
Change Order
Related Items “On File” with the Clerk of the Board:
None.