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): Second
Title:
Title
2024 Leachate Storage Tank Replacement - Contract Change Order No. 009 - Roblar Sitework
End
Recommended Action:
Recommended action
A) Authorize the Director of Public Infrastructure to execute a Contract Change Order for the construction contract with Anvil Builders, Inc. for the 2024 Leachate Storage Tank Replacement Project, in an amount not to exceed $764,611, and with an associated contract time extension up to 100 days.
B) Adopt and approve revised plans and specifications for the Project.
C) Adopt Budget Resolution authorizing a budget adjustment in the Sonoma County Public Infrastructure Fiscal Year 2025-2026 Refuse Disposal-Former Urban Landfill Adopted Budget in an amount not to exceed $1,299,751 from the Former Urban Landfill (41123) available fund balance.
(4/5th Vote Required)
end
Executive Summary:
Sonoma County Public Infrastructure (SPI) is seeking Board authorization to execute a Contract Change Order in a not-to-exceed amount of $764,611 for the 2024 Leachate Tank Replacement Project, originally awarded to Anvil Builders, Inc. on June 4, 2024, for $8,665,002. The requested Change Order includes a contract time extension of up to 100 days. This Change Order addresses unforeseen subsurface conditions discovered at the Roblar Closed Landfill site on December 10, 2024, which made implementation of the original tank foundation design unfeasible.
Specifically, the contractor encountered persistent groundwater seepage and a higher-than-anticipated perched water table, which required halting work and redesigning key site infrastructure. To date, emergency stabilization and design modifications have been implemented, including regrading, installation of a subdrain system, storm drain realignment, new retaining walls, and structural drainage improvements.
The remaining work includes final site regrading, asphalt concrete (AC) paving, slope stabilization, and installation of new guardrails. The revised scope has resulted in a critical path delay requiring a time extension of 71 working days (or 100 contract days). The proposed change order includes compensation for work already completed on a time-and-materials basis, as well as a negotiated lump sum for the remaining items.
The Board is requested to authorize the SPI Director to execute the change order upon completion of final cost negotiations with the contractor. In no event will the total cost exceed $764,611, nor will the time extension exceed 100 contract days. If approved, substantial completion is projected for October 22, 2025, with final completion on November 5, 2025.
Approval of this item will allow SPI to resume work at the Roblar site without further delay and adopt the revised plans and specifications reflecting the updated design.
Discussion:
Background
The County of Sonoma is responsible for seven legacy closed landfill sites throughout the County, including the Guerneville, Roblar, and Sonoma Closed Landfills. Each of the sites has a leachate collection and recovery system consisting of collection sumps, transfer pumps, and mobile 22,000-gallon storage tanks. Leachate is pumped to the tanks and removed intermittently by tanker trucks. The leachate is typically hauled to the Laguna Sub-regional Wastewater Treatment Plant for treatment and disposal.
During peak wet weather events, such as major winter storms, these sites can produce leachate volumes that exceed existing storage capacity, requiring continuous trucking to avoid overflows. In recent years, the treatment plant has experienced intermittent multi-day closures, further increasing stress on the system. As a result, sites that were once considered adequately equipped are now vulnerable to overflow events. Enhancing leachate storage capacity is essential to improve system resiliency and ensure uninterrupted operations during high-flow periods or temporary disruptions in treatment facility access.
Leachate Tank Storage Tank Replacement Agreement
On June 4, 2024, the Board awarded a construction contract to Anvil Builders, Inc. in the amount of $8,665,002 for the removal and replacement of aging 22,000-gallon steel Baker tanks with permanent 200,000-gallon stainless steel leachate storage tanks at three County closed landfill sites: Guerneville, Roblar, and Sonoma. Each site is to receive two (2) 200,000-gallon tanks significantly increasing storage capacity and improving system resiliency during peak wet weather events. The Notice to Proceed was issued on October 21, 2024, with a planned final completion date of July 8, 2025.
During excavation and site preparation at the Roblar site, on December 6, 2024, Anvil encountered persistent standing water and elevated groundwater seepage levels that differed significantly from geotechnical assumptions. These conditions rendered the original foundation design infeasible. Work at the Roblar site was suspended while GHD, Inc., the County’s contracted design consultant, developed a revised, site-specific plan responsive to these field conditions.
To date, several design modifications have been implemented, including site regrading, storm drain realignment, structural drainage improvements, and construction of retaining walls. Remaining work includes slope stabilization, additional grading, asphalt concrete (AC) paving, and the installation of safety guardrails.
On January 20, 2025, Anvil formally notified the County of the differing site conditions and potential impacts to the project schedule. A Change Order request was submitted on March 11, 2025. The proposed not-to-exceed amount of $764,611 reflects actual time-and-materials costs incurred to date and a negotiated lump sum for remaining scope items as well as compensation for delay. County staff has reviewed the supporting documentation, and negotiations are ongoing to finalize the Change Order amount.
Staff is requesting delegated authority for the Director of Public Infrastructure to execute the Change Order immediately upon conclusion of negotiations. This will facilitate prompt resumption of work and associated payments to the contractor, avoiding any further delays. Approval of this item also serves to adopt the revised plans and specifications for the Roblar site (Attachment 1). If approved, substantial completion is projected for October 22, 2025, with final completion on November 5, 2025.
The Board is also requested to adopt a budgetary adjustment for the project as reflected in the attached resolution. The requested adjustment establishes a contingency of 15%, or $1,299,751, to account for unanticipated costs to complete the project, including the subject 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 2: Invest in capital systems to ensure continuity of operations and disaster response.
Objective: Objective 1: Align the Board of Supervisor’s strategic priorities, policy, and operational goals with funding and resources.
Racial Equity:
Was this item identified as an opportunity to apply the Racial Equity Toolkit?
No
Prior Board Actions:
06/04/2024 Board approved a construction agreement with Anvil Builders, Inc. for the 2024 Leachate Storage Tank Replacement Project.
Fiscal Summary
|
Expenditures |
FY25-26 Adopted |
FY26-27 Projected |
FY27-28 Projected |
|
Budgeted Expenses |
|
|
|
|
Additional Appropriation Requested |
$1,299,751 |
|
|
|
Total Expenditures |
$1,299,751 |
|
|
|
Funding Sources |
|
|
|
|
General Fund/WA GF |
|
|
|
|
State/Federal |
|
|
|
|
Fees/Other |
|
|
|
|
Use of Fund Balance |
$1,299,751 |
|
|
|
General Fund Contingencies |
|
|
|
|
Total Sources |
$1,299,751 |
|
|
Narrative Explanation of Fiscal Impacts:
Costs associated with this Change Order request are set to a not-to-exceed amount of $764,611. This amount was not included in the Public Infrastructure Fiscal Year 2025-26 Adopted Budget. Additional appropriations from fund balance in the amount of $1,299,751 are requested in the attached Resolution from the Former Urban Landfill Fund (41123-34050300).
The source of funds for this Change Order are generated through the collection of Concession Fees under the Master Operations Agreement with Republic Services of Sonoma County, Inc., on each ton of Municipal Solid Waste and Organic Solid Waste collected at the County-owned Solid Waste Facilities.
Narrative Explanation of Staffing Impacts (If Required):
N/A
Attachments:
Attachment 1 - Project Plans, Revised
Attachment 2 - Budget Adjustment Resolution
Related Items “On File” with the Clerk of the Board:
Construction Contract for the Closed Landfill Leachate Tank Replacement Project with Anvil Builders, Inc.