Johnston Construction Co.

Owner:

Tidewater Utilities, Inc.

Architect:

Johnston Construction Company

Scope Of Work

Johnston Construction Company was the lead design-build team member providing engineering, construction, and commissioning services for the $1,558,500 lump sum contract.

The project involved the design and construction of a new water treatment facility to serve areas of Frankford, Sussex County, Delaware. The water for the project is supplied from two on-site wells with pretreatment facilities for iron oxidation, iron removal, and disinfection prior to discharging the treated water to the on-site elevated water storage tower for delivery to the water distribution system.

Water supply is provided by two wells and pretreatment includes a variety of equipment. An 8-inch diameter well and 10-inch diameter well are anticipated to produce 550 GPM and 700 GPM respectively. Well pumps are sized at 30 HP and 50 HP to provide sufficient pressure through the treatment units and accomplish the head required to pump the treated water to the elevated water storage tower prior to flowing into the distribution system. A 75’x 40’x 35’ high water treatment plant building houses most of the pretreatment equipment for the project. Chemical storage and feed systems for sodium hypochlorite and potassium permanganate are provided to pre-treat the groundwater before it enters the three 10-foot diameter green sand pressure filters manufactured by Roberts Water Technologies for iron removal. Filter backwash will be conveyed to a 60,000 gallon concrete backwash holding tank. Settled sludge solids from the backwash holding tank will be withdrawn for disposal and a decant pump will withdraw clear water from the top of the tank that will return to the head of the plant for treatment. Following the filtration process, a chlorination point for disinfection is located prior to the treated water flowing into the elevated water storage tower. A 250 kW outdoor emergency power generator was installed on site.

Several improvements were integrated into the project by Johnston Construction Company. The grinder pump station was relocated next to the water treatment plant building to eliminate the need for deep gravity piping. The use of a metal building for the water treatment building and a pre-cast concrete backwash storage tank saved overall construction time during the winter on the project. Johnston Construction Company coordinated the process and instrumentation drawings and electrical design to integrate supplied equipment and instrumentation with the owner’s Main Control Panel. The HVAC installation was also integrated with the architecture of the building.

The project was started in November 2007. Final design, construction, and performance testing was completed in May 2008.