In an effort by the North Texas Municipal Water District (NTMWD) to adhere to a TCEQ Potable Transfer Line Staff Guidance memorandum requiring transfer lines to maintain a minimum internal pressure of 5 pounds per square inch above any expected local external hydrostatic pressure, a 6.0 million gallon ground storage tank is required to act as a standpipe in their South System. LAN was selected to provide design, bidding, and construction phase services for the tank that is to be located off of McCree Road in Garland, Texas.

During preliminary design numerous flow conditions and operational requirements of the District were evaluated to determine that mixing of the tank was required to minimize the potential for stratification and maintain disinfectant residual, either of which would lead to water quality issues. Consideration was given to both plug flow operation and a fill/draw operation with evaluation for cost, system impact and system operational flexibility weighted in the decision. To address the potential for stratification in the tank, active mixing was included in the design.

The 6.0 million gallon ground storage tank (now in final design) will be a prestressed concrete ground storage tank that will include a 58-foot sidewater depth, reagentless chlorine analyzer and detailed site design to accommodate future construction of a second tank if/as required by the District.