City Council Agenda
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Memo to: |
Manteca City Council |
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From: |
Kevin Jorgensen II, Director of Engineering/City Engineer |
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Prepared by: |
Kyzen Nicolas, Associate Engineer; Somporn Boonsalat, Deputy Director of Engineering |
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Date: |
April 15, 2025 |
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Subject: |
Approval of Award of Construction Contract with C. Overaa & Co. in the amount of $22,865,000 and Approval of Amendment No. 2 with Carollo Engineers, Inc. (C2023-136) in the amount of $800,000 for the WQCF Sludge Thickener Capital Improvement Program Project (CIP 24006) and the Dewatering Unit No. 3 System Design Capital Improvement Program Project (CIP 24007) |
Recommendation:
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Adopt a resolution determining C. Overaa & Co. as the lowest, responsive, and responsible bidder for the WQCF Sludge Thickener & Dewatering Unit No. 3 System Design Project CIP No. 24006 & 24007; awarding the construction contract to C. Overaa & Co. in the amount of $22,865,000; approving Amendment No. 2 to Agreement C2023-136 for Professional Services with Carollo Engineers, Inc. for an amount not-to-exceed $800,000; approving a Project contingency of $2,000,000; and authorizing the City Manager or designee to execute the construction contract, Agreement Amendment, approve construction change orders and Agreement amendments up to the total Project budget, and take all appropriate actions necessary to carry out the purpose and intent of the resolution.
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Background:
In March 2022, the City of Manteca (City) completed a capacity assessment study (Study) for the Wastewater Quality Control Facility (WQCF). The Study identified 10 interim improvements needed to optimize the WQCF treatment process:
1. Glycerin Injection System (completed and in-service)
2. Replace Waste Activated Sludge (WAS) Pumps (in construction)
3. Replace Return Activated Sludge (RAS) Pumps (in construction)
4. Replace Internal Mixed Liquor Recycle Pumps (in construction)
5. Fix Flow Split to North Plant Aeration Basin (in construction)
6. Add New Independent Mixing System to Zone B (in construction)
7. Add Process Aeration Control to Improve Monitoring and Control of Denitrification (in construction)
8. Sidestream Treatment (in Design)
9. Centrifuge No.3 or Equivalent (included in this project, CIP 24006)
10. Add DAF No.3 or Equivalent (included in this project, CIP 24007)
On November 6, 2023, the City entered into an Agreement C2023-136 (Attachment 5) for Professional Services with Carollo Engineers, Inc. (Carollo) to evaluate, design, and prepare biddable project Plans, Specifications, and Estimates (PS&E) for the WQCF Sludge Thickener (CIP No. 24007) and Dewatering Unit No. 3 (CIP No. 24006) System Design Project (“Project”).
During the initial Project evaluation, Carollo was required to prepare a Preliminary Design Report (PDR) evaluating the following alternatives:
1. Review addition of a third Dissolved Air Flotation Tank (DAFT).
2. Review technology change to Rotary Drum Thickeners (RDTs).
3. Review replacement of the existing DAFTs with Gravity Belt Thickeners (GBTs).
4. Analysis of co-thickening of the Primary Sludge (PS) and the WAS.
5. Review addition of a third centrifuge that matches the existing units.
6. Review addition of a third centrifuge with a higher capacity than the existing units.
7. Review replacement of the centrifuges with screw press technology.
The Final PDR made the following recommendations:
Sludge Thickener
• Design the new sludge thickening process to allow for co-thickening of primary sludge and secondary sludge to maximize the total solids concentration of the sludge feed to the digesters and homogenize the sludge feed to reduce process upsets.
• Install new RDT technology which allows for co-thickening of primary sludge and secondary sludge.
• Convert existing DAFTs into sludge blending tanks and install required yard piping.
• Replace MCC-E (motor control center) to support new process equipment.
Dewatering
• Continue with the design of the addition of a third centrifuge that matches the existing units as this is the most economical solution.
Based on the PDR, the following recommended alternatives would be most beneficial and economical to increase treatment capacity at the WQCF:
• Sludge thickening system: Replacement of the existing DAFTs with RDTs and co-thickening of PS and WAS
• Dewatering system: Addition of a third centrifuge that matches the existing units
On August 1, 2024, the City executed Amendment C2023-136-A1 (Attachment 6) to the Agreement for an expanded design and environmental services as recommended in the PDR for the Project.
On December 17, 2024, the City Council approved the Project plans and specifications and authorized the Call for Bids.
On January 29, 2025, the Project was advertised for bid, and a mandatory job walk was held on February 6, 2025 and on February 27, 2025. The deadline to submit questions and/or inquiries was on March 3, 2025 and responses to questions/inquiries received prior to the deadline was published on the City’s website on March 6, 2025.
Three bids were received and opened on March 11, 2025:
• C. Overaa & Co. $22,865,000
• Shimmick Construction $24,876,000
• Clark Bros Inc. $27,300,000
Staff has requested Carollo to provide an expanded task and fee to provide engineering support during the construction phase of the project. Staff has completed agreement amendment negotiations with Carollo for an amount not-to-exceed $800,000.
Fiscal Impact:
The Design, Construction and Contingency cost for the WQCF Sludge Thickener (CIP 24007) and Dewatering Unit No. 3 (CIP 24006) System Design Project is $27,561,818. The expense breakdown of these costs is as follows:
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Description |
Original Contract |
Amendment No. 1 |
Amendment No. 2 |
Contingency |
Total |
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Design (Carollo): |
$966,983 |
$929,835 |
$800,000 |
- |
$2,696,818 |
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Construction (Overaa) |
$22,865,000 |
- |
- |
- |
$22,865,000 |
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Project Contingency |
- |
- |
- |
$2,000,000 |
$2,000,000 |
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Total |
$23,831,983 |
$929,835 |
$800,000 |
$2,000,000 |
$27,561,818 |
A portion of the total project costs of $10,783,491 is within the Fiscal Year 2025 Capital Improvement Program Budget, allocated amongst both CIP projects 24006 and 24007 in Funds 640 Sewer O&M and 650 Sewer Improvement.
Projects (CIP 24006 and 24007) Funding is as follows:
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Description |
FY25 Amended Budget |
Expended to Date |
Remaining in FY25 |
Future Funding in FY26 |
Total |
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CIP 24006 |
$3,800,000 |
$883,457.66 |
$2,916,542.34 |
$3,800,000 |
$7,600,000 |
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CIP 24007 |
$6,983,491 |
$883,457.71 |
$6,100,033.29 |
$18,400,000 |
$25,383,491 |
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Total |
$10,783,491 |
$1,766,915.37 |
$9,016,575.63 |
$22,200,000 |
$32,983,491 |
Approval of the Fiscal Year 2026 Capital Improvement Program future funding needs of $22,200,000 for these agreements is contingent upon Council approval through the upcoming annual budget process.
Documents Attached:
1. Attachment 1 - Resolution
2. Attachment 2 - Construction Contract
3. Attachment 3 - Bid Tabulations
4. Attachment 4 - Subcontractor List
5. Attachment 5 - Agreement C2023-136
6. Attachment 6 - Amendment No. 1 (C2023-136-A1) to the Agreement C2023-136
7. Attachment 7 - Amendment No. 2 to the Agreement C2023-136
8. Attachment 8 - Location Map