Client North Texas Municipal Water District

6.0 Million Gallon Ground Storage Tank

Garland, TX

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.

At a glance

Total storage at the tank will be 6.0 million gallons

The tank will measure roughly 65-feet in height on completion

The preliminary construction cost estimate for the project is $7.5 million

The design is being prepared for a prestressed concrete tank

The triangular tank site is confined by high voltage transmission power lines, a railroad and an industrial warehouse

Design includes a rigid pavement access road in order to protect the existing 42-inch transmission pipeline from excessive construction loading

Features

Five separate operating scenarios were considered in preliminary design to ensure maximum flexibility

Evaluations included passive and active tank mixing as well as a combination of the two

An onsite detention pond was designed to accommodate future draining of the tank for maintenance with minimal impact to municipal storm water systems

Services

Design

Land & Site Devel