Durable & Watertight

DuraStor™ Tanks are ideal for use in water storage and treatment structures – high strength steel tendons apply compression to the tank floor, walls, and roof to counteract the applied forces and provide residual compression.

Why Cut Corners?

DuraStor™ Tanks (AWWA D115 Tendon Prestressed Concrete Tanks) offer the benefits of prestressed concrete and the geometric flexibility of conventionally reinforced concrete. Unlimited Applications – Any Shape, Any Size

Economical – 25% Cost Savings

Pre-stressing allows for thinner members – reducing materials, labor, construction schedule, and costs compared with conventionally reinforced tanks.

The Most Versatile & Durable Concrete Tank Available


DuraStor™ Applications:
  • Water Storage
  • Water/Wastewater Process & Treatment
  • Thermal Energy Storage
  • Combined Sewer Overflow Systems

DuraStor™ Tanks (AWWA D115 Tendon Prestressed Concrete Tanks) offer the benefits of prestressed concrete and the geometric flexibility of conventionally reinforced concrete.


Unlimited Applications – Any Shape, Any Size

Whether driven by process or space considerations, DuraStor™ Tanks may be engineered and built into any shape or size, similar to conventionally reinforced tanks.


Durable & Watertight

STRUCTURAL TECHNOLOGIES’ DuraStor™ Tanks are ideal for use in water storage and treatment structures – high strength steel tendons apply compression to the tank floor, walls, and roof to counteract the applied forces and provide residual compression. This method actively reinforces the structure providing crack free concrete, joint free slabs, and no measurable leakage.


Economical – up to 25% Cost Savings

Based on size and other design criteria, DuraStor™ tanks may offer a significant savings in construction and long-term maintenance investments compared to other concrete tank alternatives available. Compared to conventional concrete – DuraStor™ tanks reduce materials, labor, and schedule, saving up to 25% in initial construction investment.


Featuring VSL Post-Tensioning

DuraStor™ Tanks are reinforced with VSL systems – which have been used as the industry standard for post-tensioning throughout the world.

VSL® is the registered trademark of VSL International Ltd.


DuraStor™ Tanks are prestressed concrete storage tanks reinforced with post-tensioning tendons (governed by ACI 350 and AWWA D115). This method actively reinforces the structure and significantly enhances its watertightness and long-term durability. DuraStor™ Tanks can be constructed in many shapes to suit project needs – there are no practical limitations. Tanks have been constructed with capacities up to 30,000,000 gallons. Experience the benefits of prestressed concrete with the geometric flexibility of conventionally reinforced concrete.

Tank Roof Options

Flat Roof Option

Similar to the floor, the roof slab is cast in a single placement with no construction joints. This method results in a watertight slab that eliminates the possibility of substances entering the tank and contaminating the contents. The roof slab is column-supported with typical spans in the 30-foot range each way. Slab thickness is approximately 8 inches. Roof shoring is placed immediately following the column and column footing placement to minimize construction time. Post-tensioning tendons are placed orthogonally as in a typical two-way suspended slab and are "stage stressed" in the same manner as the floor slab tendons. After the tendons are stressed, the shoring is removed through access hatches. Dome roof prestressed concrete tank

Dome Roof Option

Column-supported flat roofs are often chosen for buried tanks or where a less visible tank is desired. A cast-in-place concrete dome is an efficient option for circular tanks where a flat roof is not required

AWWA D110-04 vs. AWWA D115-06 tank roof comparison chart


Tank Walls

The wall is composed of full-height segments frequently 12-inches thick. They’re cast in lengths of approximately 75 feet with no horizontal construction joints. Post-tensioning tendons placed horizontally may be tensioned at pilasters or pilasters may be eliminated depending on the project requirements. Tendons are also placed vertically to provide compression to the concrete and accommodate vertical bending moments and thermal stresses.

On large tanks it is possible to place as many as four wall segments per week. Column footings and columns are cast concurrently with the wall to minimize the duration of construction. If required, walls may have any architectural finish, form liner or coating to meet the project’s aesthetic requirements.

AWWA D110-04 vs. AWWA D115-06 tank wall comparison chart


Tank Floor Slabs

Joints in a floor slab can allow liquids to leak out of a tank – creating the possibility of adversely affecting the environment and/or undermining the structure’s foundation. Joints can also allow substances to seep into the tank and potentially contaminate the contents.

DuraStor™ tank floors are cast in a single placement with no joints or dowels. The floor is a highly reinforced ductile concrete membrane, normally five inches thick, that can tolerate differential movements while maintaining watertightness. The tendons are "stage-stressed" within 48 hours of casting the floor slab to eliminate shrinkage cracks by providing immediate precompression to the concrete.

AWWA D110-04 vs. AWWA D115-06 tank floor comparison chart


Design & Engineering Support

Design & Engineering Support

Our skilled, dedicated professionals bring innovation to every project need. STRUCTURAL TECHNOLOGIES provides technical support during the planning and construction phases of projects. Our comprehensive range of services includes feasibility studies, cost estimates, preliminary designs, alternative proposals, detailing, project coordination, contractor consulting, and execution of the work utilizing VSL products and equipment.

Because each project presents a unique opportunity, STRUCTURAL TECHNOLOGIES teams with contractors, owners, and engineers to evaluate projects and determine optimal solutions. Our engineers have extensive experience in structural design and are active members of technical organizations such as the Post-Tensioning Institute (PTI), the American Segmental Bridge Institute (ASBI) and the American Concrete Institute (ACI).



Post-Tensioning Engineering Team Leader
John Crigler, P.E.

John Crigler, PE

With over 30 years of experience at VSL, Crigler is a recognized expert in post-tensioning. He is an active member of several industry associations including the American Segmental Bridge Institute (ASBI), Post-Tensioning Institute (PTI), American Society of Civil Engineers (ASCE) and American Concrete Institute (ACI).  In 2008, he received the ASBI Leadership Award given for outstanding leadership for the development of the segmental bridge industry. Crigler received his Bachelor of Civil Engineering from Virginia Polytechnic Institute and is a registered professional engineer in Virginia, as well as numerous other states.



STRUCTURAL TECHNOLOGIES' licensed engineering services are provided by StrongPoint Engineering, LLC - A Structural Group Company, or through other licensed engineers.

Our Services

Design & Planning

  • Preliminary designs& estimates
  • Performance specifications
  • Bidding assistance
  • Structural design
  • Plans & specifications

STRUCTURAL TECHNOLOGIES’ engineers have the experience to assist designers in developing a range of alternatives, solution development, cost and constructability consulting, and design assistance to help project teams select the best potential solution.


Construction Support

  • Supply of prestressing systems & equipment
  • Installation, training & QA/QC support
  • Value engineering

DuraStor™ tanks are typically built in unison with a local tank contractor. Our staff is recognized globally for scaling to the needs of projects to provide expert installation of our prestressing systems as well as general constructability support.


Tank Repair, Strengthening & Modification

  • Inspection & maintenance programs
  • Repair & modification
  • Structural rehabilitation

Whether adapting tanks for process improvements or developing repair and maintenance programs to extend their service life, we provide a full range of services including analysis support, repair system design, materials, and full repair services from a single source.




STRUCTURAL TECHNOLOGIES — A Structural Group Company

With member companies dating back to 1902, Structural Group is firmly committed to its ongoing mission of making new and existing structures stronger and last longer. Through its member companies, Structural Group delivers turnkey solutions that integrate technology, engineering, and construction. Structural Group provides state-of-the-art products and engineering support services through STRUCTURAL TECHNOLOGIES and specialty contracting services through STRUCTURAL and PULLMAN

Learn more about Structural Group and its member companies.