CITY OF SAN MATEO
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CITY OF SAN MATEO
Agenda Report
City Hall
330 W. 20th Avenue
San Mateo CA 94403
www.cityofsanmateo.org
Agenda Number: 15 Section Name: CONSENT CALENDAR Account Number: 72-4671 File ID: 25-10257 TO: City Council
FROM: Alex Khojikian, City Manager
PREPARED BY: Public Works Department
MEETING DATE: August 18, 2025
SUBJECT:
Wastewater Treatment Plant Annual Major Components – Contingency Reserve Increase RECOMMENDATION:
Approve an increase to the project contingency of the Digester 2 Coatings Project being performed by Brand Energy Services of California, Inc. by $160,000, for a total contingency reserve in the amount of $242,000; and authorize the Public Works Director to approve any necessary change orders within the approved contingency amount.
BACKGROUND:
The Clean Water Program (CWP) Annual Major Components (AMC) Projects includes several capital improvement projects that are currently under development or under construction and are intended to upgrade or rehabilitate aging infrastructure in the City’s sewer collection system and Wastewater Treatment Plant (WWTP). The AMC includes the WWTP Biogas and Biosolids Evaluation project which is being conducted by Brown and Caldwell (B&C). The scope includes condition assessment and inspection of both digesters. An initial condition assessment of Digester 2 was recently completed, and it revealed that the coatings of the draft tube and interior of the digester need repair. This will help prevent wear and tear related issues caused by the composition digester sludge and gas.
Digester 2 is currently offline due to the mixer failure in 2022. The mixer is currently being repaired off site and is expected back in late August 2025. The WWTP is currently operating with only Digester 1. Digester 1 is the older of the two digesters and there is concern about its current condition. It is in the City’s best interest to bring Digester 2 online as soon as possible. Operating the plant with only Digester 1 causes an increase in the liquid content in the off-haul material. This has increased the cost of hauling the material by $26,000 per month.
With Digester 2 offline, the City performed a cleaning and condition assessment of Digester 2. To facilitate the condition assessment, an internal scaffold was installed which was a costly effort. At the end of March 2025, after being notified that the inspection and evaluation was complete, the consultant recommended re-coating the digester and draft tube, as the existing coating was completely worn off. Without the coating, the interior of the digester vessel would be vulnerable to accelerated corrosion and degradation once Digester 2 is back in operation. Additionally, completing the coating work while the scaffold was still in place offered a clear economic advantage.
On June 2, 2025, City Council approved an agreement with Brand Energy Services of California, Inc. (Brand Energy) to conduct the WWTP Digester 2 Coatings in an amount not to exceed $406,881.35 and a contingency of $82,000.00.
Through a competitive bidding process, Brand Energy was the lowest bidder and considered competent and qualified. B&C also reviewed and accepted their coatings methodology.
On June 16th, Brand Energy mobilized and began preparation work. After the crew completed the blasting process (the first step to coatings), B&C requested the City to view the bottom of the digester, which was not visible at the time of their
CITY OF SAN MATEO
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inspection in March. The findings of their inspection revealed corroded and pitted areas of the steel. These needed to be welded before the coatings service could continue. Brand Energy had to pause their services until the welding was complete. The cost incurred in standby equipment rental and fuel costs to pause their services resulted in a negotiated amount of $80,000, which exhausted most of the project contingency.
Brand Energy resumed their services on July 29, 2025. The next step was a chloride wash of the vessel, and its purpose was to remove soluble salts to prevent under-film corrosion, salt blooming, adhesion issues, and blistering. Additionally, given the WWTP proximity to the Bay, exposure to salt water accelerates these risks. Therefore, performing a chloride wash and meeting chloride levels per the manufacturer’s specifications is essential. Brand Energy conducted the chloride wash; however, it did not achieve the required chloride levels at the lower bottom third of the tank. The elevated chloride concentration in this area was unanticipated. This is potentially due the shape of the tank where there is a higher concentration of chloride that accumulates per square foot at the bottom.
The contractor initially requested an additional $166,932.32 for the additional wash and labor required for this work. After negotiations and discussions, the change order request was reduced to $81,683.95.
Staff recommends $160,000 be authorized and added to the contingency amount to address this change order and for any other potential changes that may arise due to the nature of this work. The original duration of this work was 27 working days. This change has pushed the duration by five working days.
BUDGET IMPACT:
There are sufficient funds available in the CWP WWTP Annual Major Components Project (46t090) budget to fund this increase to the contingency reserve. With the execution of Contract Change Order No.1 for $80,000 to cover the costs of standby equipment rental and fuel and this requested contingency increase of $160,000, the available contingency reserve balance will be $162,000.
ENVIRONMENTAL DETERMINATION:
This Council action is exempt from CEQA as an “existing facility,” because it consists of the operation, repair, maintenance, permitting, leasing, licensing, or minor alteration of existing public or private structures, facilities, mechanical equipment, or topographical features, involving negligible or no expansion of existing or former use. (CEQA Guidelines Section 15301.)
NOTICE PROVIDED
All meeting noticing requirements were met.
ATTACHMENTS
None
STAFF CONTACT
Thomas Ruark, Senior Project Manager
[email protected]
650-522-7280
Tom Williams, Engineering Manager
[email protected]
(650) 552-7307
Matthew Fabry, Director of Public Works
[email protected]
(650) 522-7303