WATER TREATMENT FACILITY UPGRADE
BENNINGTON, VT

Aerial photo of completed facility

Bids were opened in May 2005 with Penta Corporation, of Moultonboro, NH, as the sole bidder on the project with a bid of $6,909,970, aproximately $1,100,000 above available funds. In order to proceed with the project funded under with the State of Vermont Revolving Loan Fund Program, construction costs needed to be significantly reduced. The Town, D&A and Penta worked together to reduce the project by eliminating space reserved in the filtered water pump station for future UV disinfection units and pumps as well as several miscellaneous items. The changes reduced the construction cost by nearly $1.6 million dollars and allowed the project to proceed to construction June 2005.

KEY FEATURES

1.2 MG Clearwell constructed by Natgun

• Rehabilitation of existing facility to meet current water quality and disinfection regulations.
• Construction activities coordinated to maintain treatment facility operations.
• Electrically activated flow control valves to reduce turbidity spiking in filtered water.
• Carbon dioxide and lime feed systems for corrosion control and calcium addition to control calcuim leaching from pipes and storage tanks.
• Radio telemetry SCADA system at 4 pump systems and 3 storage tanks.
• Upgrade of 27 year old filter controls.
• Upgraded solids handling with replacement of process residual setting lagoons with solids thickener and freezing/drying bed.

Treated Water Pumps located in new pump building

Under the leadership of Stuart Hurd, Town Manager, the Town of Bennington voters approved a Bond Article of $7,000,000 for a water system improvement project in March 2004 and construction activities began in June 2005 with completion scheduled for fall of 2006.

The water system customers will pay for the project entirely. The Vermont Water Supply Division has identified the Bennington Water System as the #1 priority project again this year. Bennington is eligible to receive funding assistance with a low interest loan through the Drinking Water State Revolving Loan program (DWSRLF) for up to $6,500,000 of eligible costs.

The improvements to the water treatment facility include reduction in disinfection by products (DBP’s) by making modifications to the intake to reduce organics from entering the raw water transmission system. At the treatment facility, improvements include the elimination of prechlorination prior to filtration, individual filter flow controllers, construction of a new 1.2 million gallon clearwell for chlorine contact time and installation of an ammonium sulfate feed system for the generation of chloramines as a secondary disinfectant.

Carbon Dioxide and Lime feed systems

In addition to the DBP’s issue, the surface water source of supply is calcium deficient. The potable drinking water gradually rises in pH to a saturation of 10.2 by leaching the calcium from the mortar lining in the concrete pipe as well as from the walls of the concrete storage tanks. To correct this issue a hydrated lime feed system in conjunction with a carbon dioxide feed system will be installed. The lime and carbon dioxide will also be used as corrosion control chemicals, replacing a long used Sodium Hydroxide and Sodium Bicarbonate combination Other site modifications include the removal of two existing waste process water settling lagoons and associated piping. The process wastes will be pumped to a new 0.2 million-gallon thickener tank and the tank emptied on to a 3,000 square foot freezing/drying bed for solids handling and dewatering.

Terry Morse is the Water Resources Superintendent for Bennington and has overall technical responsibility for the project.