Monday, June 18, 2007

Sewer Plant Grows With The Flow

Sewer Plant Grows With The Flow
By Barry Eberling

Laborers Tim Gomez, left, and Dale Hurd install sprinklers inside aeration basins at the Fairfield-Suisun Sewer District plant. The basins were originally constructed in 1976 to treat sludge, but are now being reconfigured to handle waste water. (Zachary Kaufman/Daily Republic)

FAIRFIELD - As Fairfield and Suisun City grow, so does the unceasing flow of sewage from every house, business and factory day after day.

The Fairfield-Suisun sewer district plant along Chadbourne Road on the edge of Suisun Marsh is growing, too. It's got to keep turning the increasing amounts of raw sewage into water clean enough to be poured into the environmentally sensitive marsh and used to irrigate a nearby turf farm.

"In the end, our job is to meet the cities' needs," said Larry Bahr of the district as he watched workers use a hose attached to a crane to pump cement into a wooden form as wind whipped across the marsh flatlands.

Workers have started a $35 million expansion project that will continue into 2009. They are driving piles 65 feet deep into soft marsh soils and pouring cement to create huge settling basins.

The existing sewage plant, opened in 1976 and expanded at various points during the 1980s, is handling about 85 percent of its capacity. The latest expansion is designed to keep pace with the growth plans of the two cities through 2020.

The Fairfield-Suisun plant is located on 160 acres behind fences. It is a world of concrete basins and concrete buildings scattered amid open spaces decorated with ice plant, small evergreens and other landscaping.

Some 70 miles of district sewer pipes bring almost 15.5 million gallons of sewage to the plant each day. The plant takes this soiled, smelly water and makes it clean enough under state laws to be piped to Boynton Slough in the heart of the marsh.

The plant does this by pumping the water through a series of structures. Filters, aeration basins and settling basins make it progressively cleaner. The removed solids are treated and trucked off to Potrero Hills Landfill.

Workers are readying more of these structures. They are repairing concrete on an old aeration basin, which was built in 1976 but seldom is used. In the basin, air will bubble through the water, promoting the growth of microorganisms that will eat some of the waste in the water.

They have also started work on the foundations for two clarifiers - circular, concrete structures that will be about 15 feet high and 120 feet in diameter. Water will simply sit in the clarifiers, allowing the heavier solids to sink to the bottom and removing the microorganisms left over from the aeration basin.

But building in the Suisun Marsh area isn't easy, given that the 115,000-acre marsh contains 10 percent of the state's wetlands and a number of rare creatures. Environmental laws have tightened since the original plant was built three decades ago.

Orange, plastic fences surround a quarter-acre that is a stone's throw from where workers dug up the ground for the new clarifiers. These fences put off-limits a low-lying spot that could contain vernal pools, a rare type of wetlands that are home to threatened flowers and shrimp.

Bahr isn't convinced the wetlands at the sewer plant are vernal pools. But doing the necessary testing for indicator species during multiple dry and wet seasons could take at least 18 months, which would add another $3 million to the project because of swiftly rising construction costs, he said.

Instead, the district agreed to treat the wetlands as vernal pools. It's cheaper to preserve the wetlands on site and preserve almost two acres of vernal pool land in eastern Solano County at a cost of about $300,000.

"It's just part of building projects these days," Bahr said. "You have to do it."

After sewage water is cleaned up and treated with chlorine, much of it takes a mile-long journey in a concrete pipe to Boynton Slough. But this pipe sits amid soft, unstable marsh soils that shake like jelly during earthquakes.

"If we were to get a large earthquake, we're not certain that pipe would be in pristine condition anymore," district Assistant General Manager Talyon Sortor said.

So, the district is building a new pipe to the marsh, this one made of a plastic and leading to Ledgewood Creek about 1.5 miles away. That will give the district another option should earthquakes, repairs or other problems ever close down the Boynton Slough pipe. Also, it will allow the district to drain more treated water from the plant.

After all, the demands put on the plant from the two cities are relentless. The sewage plant can't take a day off.

The area in pioneer days had no sewage treatment plant. For example, Suisun City in 1906, with a population of about 625, had a pipe spilling raw waste at the edge of town near several homes. Some citizens saw it as a health threat.

"The sewer should be extended further into the tules so that the refuse would be carried away by the water," the Solano Republican newspaper said.

By 1951, Fairfield and Suisun City had a combined population of 4,000. The state approved forming the sewer district so the two cities could build a treatment plant and stop raw sewage spilling into Suisun Slough.

The district built its first treatment plant in 1957 in Suisun City, near today's City Hall along Suisun Slough, at a cost of about $500,000. That's about $3.5 million in today's dollars, only a tenth the cost of the expansion project. The cities used the plant until 1976, with Suisun City tearing it down about a decade ago.

Reach Barry Eberling at 425-4646 Ext. 232 or at

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