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.

Below is a comparison of tank walls (AWWA D110-04 / AWWA D115-06). 
View full comparison.

Wall:	AWWA D110-04 Code	Wrapped Prestressed Tank	AWWA D115-06 Code	Tendon Prestressed Tank
Minimum Thickness	3.5.4	as low as 3.5" - depending on wall type I, II, III or IV	3.7.3	9", however 11" -12" is most common
Required minimum horizontal residual compression from prestressing	3.4.2.2	200 psi for wall above grade, 50 psi for wall below grade - only concrete core wall within the wrapping is prestressed - shotcrete coatings on prestressing steel has no residual compression and is usually in tension	3.7.4.1	200 psi for wall above grade, 100 psi for wall below grade - entire wall thickness is prestressed with minimum residual compression
Required minimum vertical residual compression from prestressing	3.5.3	200 psi only on concrete core wall within the wrapping is prestressed - shotcrete coatings on prestressing steel has no residual compression	3.7.5	200 psi for above grade, 125 psi for below grade - entire wall thickness is prestressed with minimum residual compression
Sheet steel diaphragms provide watertightness?	3.5.6	yes - if wall type II, III or IV. If not vertically post-tensioned wall must have a steel diaphragm. Vertical rebar may be eliminated depending on design.		steel diaphragms not used or required as quality concrete is impermeable
Steel sheet diaphragms provide flexural reinforcement?	2.5.1.3, 2.9.1	26 gauge steel sheets relied on for watertightness and vertical flexural reinforcement - field joints require field-applied sealants, type IV walls require field-applied sealants at form tie holes		steel diaphragms not used or required as quality concrete is impermeable
Inside face concrete cover on vertical mild reinforcement	3.5.4.2, 3.5.6.2	1" on steel sheet diaphragm and rebar	3.11	1.5" on rebar if not two-way prestressed, 1" on rebar if two-way prestressed
Precast panel misalignment?	5.2.7	up to 3/8" misalignment allowed for precast wall segments,		wall segments are cast-in-place, no misalignment possible
Vertical mild reinforcement ratio	3.5.6	0.0025 each face (steel diaphragm is included in ratio for type II, III and IV walls)		no minimum may be required if prestressed and depending on concrete stresses
Vertical prestressing protection		"unbonded grouted" system - grade 150 bar in a PVC duct with epoxy grout, vertical prestressing only used on type I tanks	1.3	5" minimum cover of bi-axially precompressed concrete, HDPE duct and coating in accordance with PTI and ACI standards
Horizontal prestressing protection	5.3.3.3.4	Sacrificial galvanizing on wire with one inch of non-prestressed shotcrete cover. Shotcrete cover goes into tension as it shrinks and when tank is filled, cover can delaminate, leakage source difficult to locate - water migrates beneath the shotcrete.	1.3	3" minimum cover of bi-axially precompressed concrete, HDPP duct, high-performance grouting in accordance with PTI and ACI standards
Wall construction methods	1.1.1	four different wall types that can result in sole sourcing of a particular type		cast-in-place construction is non-proprietary
Shotcete cover on metal diaphragms	3.5.4.2, 3.5.6.2	for diaphragms, 1" inside face cover and 0.5" cover on outside prior to wrapping