Tiburon moves closer to closing sanitation ponds

Tiburon has picked a firm to complete the closure of sanitation ponds it purchased in April.

The Town Council approved a contract last week with WestRock Engineering, based in San Francisco, for $284,375.

“This has been a 10-year effort,” said Holli Thier, the vice mayor. “I am thrilled, thrilled that we are at the moment where we have acquired these ponds for public space, and we are moving in the direction of closing these ponds.”

The town bought the defunct sanitation ponds at 510 Tiburon Blvd. from the Richardson Bay Sanitation District for $573,704.05. The purchase expanded the town’s open space by 32,820 square feet.

As part of the property purchase, the town agreed to cover the costs of closing the ponds and to comply with a state-approved closure plan.

The base bid, which is the option Town Council approved, includes removing the fence and retaining walls; placing and compacting clean fill within the ponds; and grading the area with a small slope. Any wastewater pond piping and structures would be removed, and storm drain infrastructure would be added. The town engineer estimated the work to cost $348,000, according to a staff report.

An alternative bid would also include dewatering the ponds; removing wastewater pond piping and structures; and installing storm drain infrastructure. However, the design would not grade the area, just fill the ponds. It would also keep the retaining walls and the fence, although the barbed wire would be removed. The town engineer estimated this option to cost $332,000.

Both bids included two items that could be added onto the contract. One item is paving a section of access road on the district’s property next to the ponds, which the sanitation district would pay for. The second item is to save, instead of demolish, the concrete blocks in the retaining walls.

“We could use them in the future and/or sell them,” said David Eshoo, the engineering manager for the town.

WestRock Engineering’s bid came in at $282,375 for option one with another $40,000 to pave the access road section and $2,000 to save the concrete blocks. The firm said it would cost $246,000 for the alternative option, but paving the access road would cost $100,000 because of the extra grading needed.

Eshoo said the town received a second bid from Maggiora and Ghilotti Inc., but its base bid came in at $398,200, and $358,800 for the alternative.

Thier said the ponds need to be filled in, even if the area will eventually be transformed into something else. Eshoo said the ponds must be filled pursuant to state regulations.

“The town has to follow state law, and if we don’t follow the state law we can never do anything with that space and we may lose it,” said Thier.

Eshoo said the ponds should be decommissioned “as soon as possible” to prevent legal issues with permitting — the sanitation district has an open permit on the ponds until the town closes them — and to limit the possibility of construction costs increasing. He added that winter rains could complicate construction.

Included in the Town Council’s approval was an amendment of $116,826 to the fiscal year 2024-25 budget to pay for the project. Funding for the project includes $250,000 from the town’s capital improvement plan in fiscal year 2024-25. The town has already spent $15,251 on preliminary engineering.

The total cost of the project — which includes a $35,200 construction management contract and a 10% construction contingency — is $460,351.

Eshoo said crews aim to begin work the first week of October and to finish before Thanksgiving.

Councilmember Jack Ryan was absent from the council meeting.