CITY COUNCIL MEETING
JANUARY 24, 2023
DOCUMENTS RECEIVED
AFTER PUBLISHED
AGENDA
PUBLIC COMMENTS
(ecomments)
AGENDA
QUESTIONS AND ANSWERS
AGENDA QUESTIONS & ANSWERS
MEETING DATE: January 24, 2023
Item #5 CONS 23‐033
Adopt a Resolution Approving the Plans and Specifications and Calling for Bids for the Safe Routes to School Project, Project No. 05319
On Item 5 Safe Routes to School:
Does Chavez Middle School have bike racks available on site to accommodate the additional bike traffic anticipated?
The school reports that it has secured bike parking. These improvements are not expected to generate a significant increase in bike usage in the short term.
Item #6 CONS 23‐035
Adopt a Resolution Increasing the Construction Contract with GSW Construction, Inc, Contract No. 23054, by $34,000 for a Total Not‐To‐Exceed Amount of $241,500 for the Trash Capture Device Installation on Cotter Way Project No. 07675
On Item 6 Trash Capture Device:
Do we know where the petroleum contamination in the soil came from on the original site?
Staff believes the petroleum contamination came from the two gas stations on Foothill Blvd (Chevron and 76). Both are in the same drainage area as the Cotter Way storm pipe and their drainage flows toward the trash capture device. Staff have been involved in moving forward the talks between the responsible party (property owner) and the Water Board for remediation of the area. However, the extent of the contamination is unknown and historically the efforts have been slow.
Item #7 CONS 23‐047
Adopt a Resolution Authorizing the City Manager to Award a Contract to Carbon Supply Inc. for Bio‐Gas Conditioning System Media Replacement Project No. 07618 in an Amount Not‐to‐Exceed $319,800 RECOMMENDATION
On Item 7 WPCF Bio Gas conditioning system:
It seems like we have to replace these frequently; is there other technology out there with a longer life span?
The gas conditioning system skid currently treats biogas to remove hydrogen sulfide and siloxanes (a by‐product of silicone containing products, lubricants, and sealants among other things) prior to combustion in the cogeneration engine. Removal of these components is necessary to prevent fouling and corrosion of the engine. WPCF staff perform tasks designed to prolong the life of the media including monitoring the pH of the media and maintaining the media within optimal pH by periodically dosing it with a solution of soda ash and water.
Several years ago, WPCF staff experimented with using an alternative media to iron sponge (Sulfatreat) to determine if it could serve longer to remove hydrogen sulfide; however, this was unsuccessful lasting only 6 months versus the iron sponge media that lasts 9‐12 months. Regarding the siloxane vessels, carbon is the only media currently available for removing siloxanes. WPCF staff achieve 9 to 12 months of service life per vessel for the siloxane removal system. The system was sized to provide a design life of approximately 6 months, so the system is outperforming the original design basis.
Since the gas conditioning system was designed (approximately 2012) and installed (2014), there may have been advances in treatment systems designed for treating biogas including methods to regenerate media in place rather than removing and replacing the media. Staff have engaged Brown and Caldwell, a leading water and wastewater consulting firm, to design the WPCF Improvements Phase II Project. As part of that project, a solids master plan study will be conducted which will guide the WPCF solids handling processes including use of biogas for the next twenty years. As part of the master plan, staff will request Brown and Caldwell evaluate alternative gas conditioning and treatment technologies to see if there have been technological developments that will result in a more sustainable and cost‐effective method of treating the biogas.