Water > Project Case Study

Project awarded "Excellence in Construction"
by American Builders Association

Project received "Honorable Mention" by ACEC NH

The City of Somersworth draws its drinking water supply from the Salmon Falls River, which is susceptible to high color and turbidity events. The poor source water quality limited the capacity of the water treatment facility and the finished water quality. 

Average daily flows were approximately 2 MGD, with peak demands exceeding the current facility capacity of 3 MGD. In addition, organic loadings and disinfection with free chlorine had created disinfection by-products which exceeded the current MCL for TTHM and HAA5.

Wright-Pierce was retained by the City to screen treatment alternatives to upgrade the conventional treatment facility.  The ultimate goal of the facility upgrade was to increase treatment capacity to 6 MGD and reduce the organic loading by 60 - 70% while retaining the existing building envelope.

After conducting a  screening analysis of treatment alternatives, a ballasted sand pre-treatment technology was selected for pilot testing and full scale design. Several enhancements were incorporated into the scope of the project to achieve the most feasible long term solution. The enhancements include a new powder activated carbon-feed system; chemical feed system upgrades; control valve upgrades; filter modifications/upgrades; lagoon enhancements; new raw and finished water pumps; and SCADA control and upgrades.

The ballasted sand treatment selected for the Somerset facility is the first-of-its-kind application in New England. ACEC NH recognized Wright-Pierce for the innovative design and construction of the facility upgrade by selecting it the winner of the 2009 ACEC NH "Excellence in Construction" award.

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