TO: Members of the Governing Board
FROM: Christopher Silke, District Engineer
REPORT BY: Anna Martinez, Assistant Engineer
SUBJECT: Approval of Plans and Specifications and Authorization to Advertise for Bids for Wastewater Pond No. 2 Slide Repair Project, NB 22-01
RECOMMENDATION
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District Engineer requests approval of plans and specifications for the Wastewater Pond No. 2 Slide Repair Project, NB 22-01, authorization to advertise for sealed bids.
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EXECUTIVE SUMMARY
On May 3, 2022 the Board authorized a professional service agreement with Geocon Consultants, Inc. for geotechnical and engineering services related to the design basis and preparation of drawings to repair a failed slope impacting operation of Wastewater Pond No. 2. Project Plans and Specifications are now complete and staff recommends Board approval for public bidding.
FISCAL & STRATEGIC PLAN IMPACT
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Is there a Fiscal Impact? |
No |
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Is it currently budgeted? |
Yes |
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Where is it budgeted? |
Fund 5240, Org 5240500, Project 22017. |
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Is it Mandatory or Discretionary? |
Discretionary |
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Discretionary Justification: |
Approval of plans and specifications and authorization to advertise for sealed bids is necessary to move to the construction phase. |
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Is the general fund affected? |
No |
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Future fiscal impact: |
In order to meet the informal schedule recommended by the Central Valley Regional Board construction is expected to commence in FY 22-23. A County loan to finance the construction and budget transfer will be requested at time of contract award. |
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Consequences if not approved: |
The project will not move forward to construction putting the District at risk of citation by Central Valley Regional Water Quality Control Board for inoperable facility and operating out of compliance with their Waste Discharge Requirements. Also, the extent of damage within the slide area could worsen costing the District more in restoration costs. |
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County Strategic Plan pillar addressed: |
Effective and Open Government |
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Additional Information |
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ENVIRONMENTAL IMPACT
ENVIRONMENTAL DETERMINATION: Consideration and possible adoption of a Categorical Exemption Class 1: It has been determined that this type of project does not have a significant effect on the environment and is exempt from the California Environmental Quality Act. [See Class 1 (“Existing Facilities”) which may be found in the guidelines for the implementation of the California Environmental Quality Act at 14 CCR §15301; see also Napa County’s Local Procedures for Implementing the California Environmental Quality Act, Appendix B.]
BACKGROUND AND DISCUSSION
Storm water runoff and percolating groundwater seeping from the toe of the bank of Wastewater Pond No. 2 led to a slope failure in late 2020 that prompted Operators and District staff to immediately isolate and dewater the facility because of instability and damage. An inspection determined the wastewater pond liner was not in jeopardy of releasing stored effluent. An evaporation system with lateral piping, risers and spray nozzles surrounding the storage pond was severed in proximity to the collapsed earth materials. The HDPE pond liner was stretched slightly but not torn and is believed to be salvageable. Temporary drainage pipe and earthwork repairs were executed to stabilize the site from further movement and to divert surface water runoff away from the slide until a permanent engineered solution is implemented by a contractor.
In late January 2022, an RFQ / RFP engineering services package detailing the Wastewater Pond No. 2 Slope Stabilization scope of work, submittal instructions and filing deadline was distributed to geotechnical engineering firms, and on May 3, 2022 a contract was awarded to Geocon Consultants, Inc. in the amount of $127,941 for the RFQ/RFP scope of services.
The proposed repair consists of the removal of the slide debris from Pond 2 and re-grading the slope to the original configuration. Installation of a subdrain that will capture and divert shallow groundwater away from the pond to prevent the risk of future slides at this location is also included. An additional design element includes the repair of a second slope failure above Pond 2, which left unrepaired may increase the risk of future slope failures onsite. The total estimated project cost to repair the slope failures and return the pond to operation is estimated to be $600,000.