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APPROVE MOTION TO AUTHORIZE CONTRACT AMENDMENT NO. 1 WITH CAROLLO ENGINEERS, INC FOR THE WESTSIDE SEWER INTERCEPTOR CONDITION ASSESSMENT (UW20018) (CITYWIDE)
recommended action
RECOMMENDATION
It is recommended that the City Council approve a motion authorizing Contract Amendment No.1 with Carollo Engineers, Inc. of Sacramento, CA, for the Westside Sewer Interceptor Condition Assessment (UW20018). If approved, Amendment No. 1 (Attachment A) will add $140,552 to the contract, bringing the total contract amount to $323,676.
It is further recommended that the City Manager be authorized to take appropriate and necessary actions to carry out the purpose and intent of this motion.
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Summary
The Municipal Utilities Department (MUD) operates the City’s Wastewater Utility, which includes a sanitary sewer collection system of approximately 900 miles of gravity sewer main, 554 miles of lower lateral pipe, 27 pump stations, and 30 miles of pressurized force main that convey sewage to the Regional Wastewater Control Facility (RWCF) for treatment.
The 2022 Wastewater Master Plan Update recommended that all sanitary sewer force mains be assessed for deficiencies to improve reliability and reduce operating costs.
The City currently has an active contract with Carollo Engineers, Inc. for the Westside Sewer Interceptor Condition Assessment Project (UW20018), which has the same scope of work needed for the North‑South Sewer Interceptor. After issuing a Request for Proposals (RFP) for the North‑South Sewer Interceptor Condition Assessment, no proposals were received. Therefore, staff are requesting an amendment to the existing Carollo contract to add the North-South Sewer Interceptor Condition Assessment.
If approved, Amendment No. 1 will add $140,552, bringing the total contract amount to $323,676.
DISCUSSION
Background
The Westside Sewer Interceptor (WSI) conveys wastewater from North Stockton to the RWCF at 2500 Navy Drive. The North-South Sewer Interceptor (NSS) collects wastewater from Northwest Stockton, beginning at the northwest corner of the Swenson Golf Course. From there, it flows south along Interstate 5, crossing Fourteen Mile Slough and the Calaveras River before converging at the Smith Canal Pump Station. At this point, the NSS divides into two force mains that continue beneath Smith Canal and the Stockton Deep Water Channel. One line crosses Rough & Ready Island, and both lines traverse the San Joaquin River where they are subsequently conveyed to the RWCF by gravity for treatment.
The 2022 Wastewater Master Plan Update recommends that the City complete an assessment of the condition of sanitary sewer force mains citywide to identify deficiencies, improve reliability, and reduce operating costs.
On December 6, 2024, the Municipal Utilities Department (MUD) advertised an RFP for condition assessment services for the Westside Sewer Interceptor.
On July 15, 2025, the City Council approved Resolution No. 2025-07-15-1213 awarding a Professional Engineering Services Contract in the amount of $183,124 to Carollo Engineers, Inc. of Sacramento for the condition assessment of the Westside Sewer Interceptor.
On October 24, 2025, MUD staff advertised an RFP for the North-South Sewer Interceptor Condition Assessment. No proposals were submitted by December 11, 2025.
Present Situation
After evaluating the option of re-advertising, staff determined that directly negotiating with Carollo Engineers, Inc. was the most efficient path forward. This approach leverages Carollo’s ongoing work on the Westside Sewer Interceptor Condition Assessment, an identical in scope of work, which ensures continuity, efficiency, and technical consistency across both sewer systems. Staff successfully negotiated a fee of $140,552 with Carollo Engineers Inc., which is considered reasonable for a project of this size and complexity.
If approved by the City Council, Amendment No. 1 will add $140,552 to the contract with Carollo Engineers Inc., for a total contract not-to-exceed amount of $323,676.
FINANCIAL SUMMARY
There are sufficient funds available in the Wastewater CIP Project UW20018, account 6518-000-800007-610-612-00-65-000-000, for the Westside Sewer Interceptor Condition Assessment, for the proposed Amendment No. 1.
This action has no impact on the General Fund, or any other unrestricted funds.
Attachment A - Standard Agreement Amendment No. 1