GSE Construction


Antioch Water Treatment Plant Project Wins Public Works Award

The city of Antioch’s recently completed new water treatment plant solids handling facility and Plant B expansion project won an American Public Works Association Award for the project of the year in 2007.

The 15.2 million project won in the environment category for projects over $ 2 million. Livermore-based GSE Construction Co. was contracted in July 2006 as the general contractor on the project, which was set for completion within 500 calendar days.

The solids handling facilities portion of the project consist of the construction of an equalization tank, reclaimed water pump station, Actiflo sludge holding tank, Deskins sludge drying beds, a polymer feed and storage building, and associated piping to deliver the backwash water and sedimentation waste from Plants A and B to the new handling facilities.

Plant B expansion consisted of the construction of flocculation and sedimentation basins and six new filters.

According to GSE, rehabilitation and expansion efforts at the city’s water treatment facility increased production capacity by 38% and allows the city to protect the environment by recovering virtually all of the 900,000 gallons of water currently needed to backwash filters.

The plant treats raw water principally from San Joaquin River and the Contra Costa Canal to produce potable water for Antioch residents. Orginally Constructed in 1948, the plant has undergone periodic upgrades to meet growing water demands and to confirm to increasingly strigent water quality requirements. While the most recent expansion and upgrade project increased production capacity from 26 mgd to 36 mgd, the major change involved reclaiming filter backwash and filter to waste. In the past, each of the city’s 12 filters required 50,000 gallons of water for each backwash cycle – none of which was recovered. With the solids handling upgrades, including the addition of six new filters, the demand for water topped out from 600,000 gallons to 900,000 gallons for each cycle of filter backwashing.

By upgrading to a backwash recovery system, the city is now able to recover and re-treat virtually all backwashes and filter to waste water. To recover the backwash water, the city decided to use the Actiflo, which uses sand-ballasted flocculation to accelerate and enhanced solids capture. To recover the backwash water, two Actiflo units, each with a capacity of 1 MGD were installed.

In addition to the Actiflo units, special drying beds, using the Deskins system received the captured solid waste from backwash treatment as well as the sediment solids from the plant for drying. The water drained in this drying process is thus also recovered. The solids drying in four beds can handle a total capacity of 43,200 cu ft of sedimentation.

Other principals on the projects include Brown & Caldwell as construction manager, and Black & Veatch the design engineers.

GSE says that working collaboratively as a team, the city, GSE and Brown and Caldwell were able to stay ahead of the project and resolve issues before they adversely affected the schedule. The team’s ability to stay ahead of potential project issues kept costs down and resulted in change orders tallying just over 2% of the construction budget, which is below industry standards. GSE Construction and Brown and Caldwell met with the Water Treatment Plant Superintendent regularly and scheduled downtime during the winter to minimize the impact to operations that could not have been tolerated during the summer months when wter demands peak. The schedule also accommodated buld storage deliveries of chlorine, alum and ammonia required for the day to day plant operations. Coordinating the pipeline construction along the main plant access roads used for deliveries helped keep the project on schedule.