ADDENDUM NO_ 1_06_4_26 (Fire Tower 2MG Tank).pdf

ADDENDUM NO. 1

CONTRACT DOCUMENTS AND TECHNICAL SPECIFICATIONS

June 4, 2026

PROJECT: New 2.0 MG Ground Storage Tank at Fire Tower Rd (Brogdon)

Calhoun Project No.: 358

OWNER: City of Calhoun

BID DATE: Thursday, June 18, 2026 at 2:00 p.m.

TO: All Bidders

1. CONTRACT DOCUMENTS, BID FORM, Page 00400-2, §1.5C.1 - Verification of Addenda Issuance:

It is the responsibility of the Bidder to verify that they have received all addenda in respect to the project bid. It is recommended that the Bidder contact Calhoun’s project engineer (who is handling this bid) no later than 48 hours before the bid time to confirm the total number of addenda issued. Kurt T. McCord has been assigned the project engineer role and can be reached at (706) 602-6082 (office).

All Bidders are responsible for indicating acknowledgement of each addendum issued with addendum number and date, where noted in the bid form. Failure to acknowledge all addenda in the bid form could constitute an incomplete and non-conforming bid which may or may not be read aloud.

2. CONTRACT DOCUMENTS, SUPPLEMENTARY CONDITIONS, Page 00800-

14, §35.1 – Buy American:

In general, the City certainly prefers “American made” products as indicated in the last paragraph of the supplementary conditions. However, local funds are the funding mechanism for this project and the “American made” preference should not be confused with other federal requirements (i.e. AIS or BABA). We haven’t adopted a “de minimis” policy or historically taken a hard stance on items such as steel reinforcement (Section 03200). With that said, Contractors must adhere to specifications that identify specifically approved manufacturers, especially the water distribution products (Section 02510). Furthermore, the Contractor should furnish domestically manufactured ductile iron pipe, though the use of domestic

DI fittings is not strictly enforced.

3. CONTRACT DOCUMENTS, ALLOWANCES, Page 01020-1:

Allowance amounts did not agree with the Bid Form (Section 00400). Therefore, this section was updated to coincide with the other contract documents, such as

Measurement and Payment (Section 01025). The original Allowance document should be removed and replaced by the attached version.

4. TECHNICAL SPECIFICATIONS, EARTHWORK, Page 02300-14, §3.18 –

Disposal of Suitable Materials:

The following paragraph should be added to the end of the section:

3.18 Disposal of Suitable Materials – Excess suitable soil that’s clean and free of roots/rocks/debris may be delivered and dumped at a City-owned property located at 705 West Line Street, approximately 3.4 miles from the job site.

Hauling shall be coordinated with City staff to ensure the gate is unlocked and the exact drop-off area is identified. We believe there’s enough room to accommodate all excess suitable soil from the tank site.

5. TECHNICAL SPECIFICATIONS, CAST-IN-PLACE CONCRETE, Page 03300-

6, §2.01A. – Cement:

At the end of the paragraph, please add the following statement: “Portland limestone cement Type C595 1L (12) MS will be allowed as a substitute to Type

I/II cement by the City of Calhoun.” Furthermore, please note that Section 11371 shall prevail/govern work for the prestressed concrete tank, if any discrepancies are discovered with Section 03300.

6. TECHNICAL SPECIFICATIONS, GROUND STORAGE TANK, Page 11371-1 :

Certain dimensions (i.e. tank and manway) from Section 11371 did not agree with the construction drawings. In particular, the anticipated differential settling was greater than the standard 4” membrane floor could accommodate.

Therefore, we decided to require aggregate piers, a thicker slab (6”), and a deep aggregate foundation (18”) with 2 layers of geogrid. Post-bid, we could potentially modify the 18” foundation, but we plan to stick with the aggregate piers and 6” concrete slab. Also, a couple material listings were rewritten (i.e.

interior ladder and allowed cement compositions). As a result, the Ground

Storage Tank specification was updated to concur with the design plans and Bid

Form (Section 00400). The original Ground Storage Tank document should be removed and replaced by the attached version.

7. DESIGN PLANS, GRADING & STORM DRAINAGE PLAN, Sheet 4:

After further examination, it’s been determined that the original cut/fill estimates were 10% lower than current calculations primarily due to the undercut for

GABC foundation. Revised totals are shown below.

Temporary Grading Plan: 7,223 CY Cut / 2 CY Fill

Final Grading Plan: 2 CY Cut / 301 CY Fill

Net Adjustment: 6,922 CY Cut

8. DESIGN PLANS, GROUND STORAGE TANK DETAILS, Sheet 8:

The Interior Ladder Detail shall be changed from fiberglass to T6061 aluminum with stainless steel hardware to match the exterior ladder. This modification also coincides with revisions under Section 11371.

END ADDENDUM NO. 1

City of Calhoun Project No.: 358 New 2MG Ground Storage Tank May 2026 at Fire Tower Road (Brogdon)

01020-1

SECTION 01020

ALLOWANCES

PART 1 – GENERAL

A. The Contractor shall include the allowances stated herein in their Total Base Bid. These allowances shall cover services that will be provided to the Contractor by others. The Contractor shall only utilize companies approved by the Owner. The Contractor's cost for handling, coordinating and any other costs that are necessary to complete these items but in excess of the 15% allowance mark-up shall be included in other base bid items. Any unused funds will be adjusted accordingly by change order to reflect actual cost.

PART 2 – PRODUCT

A. An allowance in the amount of $5,000 has been allocated for Geotechnical Engineering services. Only supplemental soil testing and general consultation during construction will be covered under this allowance. Aggregate pier design, soil nail design, and material testing (i.e. concrete) should be included in the Contractor’s base bid for the tank work and will be ineligible for allowance money. Any charges pertaining to the allowance must be authorized in writing by the Project Engineer in advance. Contractor will be eligible but limited to a 15% mark-up for overhead and profit. Contract change orders must be issued for any charge over and above the allocated amount. Owner has sole discretion to authorize the use of these funds.

B. An allowance in the amount of $2,500 has been allocated for special Landscaping additions, not depicted in the construction drawings. Eligible expenses would include aesthetic enhancements such as ornamental shrubs, groundcovers, stone walkways, etc..

Grassing and erosion control BMPs should be included in the Contractor’s base bid for the erosion control work and will be ineligible for allowance money. Charges must be authorized in writing by the Project Engineer in advance. Contractor will be eligible but limited to a 15% mark-up for overhead and profit. Contract change orders shall be enforced for anything over and above this amount. Owner has sole discretion to authorize the use of these funds.

The value of any work covered by an allowance shall be determined in one of the following ways:

1. Where the work involved is covered by unit prices contained in the Contract Documents, by application of unit prices to the quantities of the item involved (subject to the provisions of General Conditions, paragraphs 11.9.1 through 11.9.3, inclusive).

2. By mutual acceptance of a lump sum by Contractor and the Owner.

3. On basis of invoices plus a 15% Contractor’s Fee for overhead and profit.

4. On the basis of time and materials.

PART 3 – EXECUTION

A. Amounts stated shall include all taxes, coordination and handling that may be required to provide the equipment to the owner. Owner may choose to delay the purchase of equipment to the end of the contract.

END OF SECTION

City of Calhoun Project No. 358 at Fire Tower Road (Brogdon)

11371-1

SECTION 11371

GROUND STORAGE TANK

PART 1 GENERAL

1.01 SCOPE

A. This specification shall govern all work necessary for the design, submittals, construction and testing of a prestressed concrete tank.

B. The Contractor shall furnish all labor, materials, equipment, tools, scaffolding, shoring and incidentals required to construct a prestressed concrete tank for potable water storage as shown on the drawings and as specified herein.

C. The prestressed concrete tank shall have a wire-wound prestressed shotcrete core wall in which a steel shell diaphragm of a height equal to the full wall height has been encased. All prestressing shall be done with high tensile wire permanently bonded to the tank wall. The tank floor shall be a concrete membrane slab. The tank roof shall be a free span concrete dome.

D. The entire tank, including all portions of the floor, wall, and roof shall be built by a specialty tank contractor, using its own trained personnel and equipment.

1.02 REFERENCES

A. ACI 372R-03 – Design and Construction of Circular Wire- and Strand-Wrapped

Prestressed Concrete Structures.

B. AWWA D110-04 – Wire- and Strand-Wound, Circular, Prestressed Concrete Water

Tanks.

C. ACI 506R – Guide to Shotcrete.

D. ASTM A 821/A 821M – Standard Specification for Steel Wire, Hard Drawn for Prestressing

Concrete Tanks.

E. ASTM A 1008/A 1008M – Standard Specification for Steel, Sheet, Cold-Rolled, Carbon, Structural, High-Strength Low-Alloy and High-Strength Low-Alloy With Improved

Formability.

F. ASCE Standard 7-05 – Minimum Design Loads for Buildings and Other Structures.

G. ASTM C 881/C 881M – Standard Specification for Epoxy-Resin-Base Bonding Systems for

Concrete.

H. AWWA C652 – Disinfection of Potable Water Storage Tanks.

at Fire Tower Road (Brogdon)

11371-2

1.03 SUBMITTALS

A. Submit shop drawings in accordance with Section 01300, Submittals, Product Data, and Samples.

B. Shop Drawings: Submit detailed design drawing sealed by a professional engineer registered in the State of Georgia that provide complete plan, elevation, and sectional views showing critical dimensions including:

1. Size, location and number of all reinforcing bars.

2. Thickness of all parts of the tank structure including floor, core wall, dome and covercoat.

3. Prestressing schedule including number and placement of prestressing wires on the tank wall and total applied force per foot of wall height.

4. Location and details of all accessories required.

5. Minimum size of shop drawings shall be 18” x 24”.

C. Product Data: Submit the concrete design mixes including ingredient proportions, minimum cementitious content, and water/cementitious ratio in accordance with these specifications.

D. Design Data: Submit the structural calculations for the tank, signed and sealed by a professional engineer in accordance with Section 1.5 C. of these specifications.

E. Test Reports: Submit the concrete strength reports for 7-day and 28-day breaks.

F. Warranty Document: Submit the warranty document in Owner's name in accordance with Section 1.6A of these specifications.

G. Project Record Documents: Record the actual location layout and final configuration of tank and accessories on shop drawings and submit to engineer after construction of the tank is complete.

H. Submit Operation and Maintenance Manuals.

1.04 QUALIFICATIONS & EXPERIENCE

A. The tank Construction Company shall have the following qualifications and experience:

B. The Company constructing the tank shall be a firm with at least ten (10) years experience in the design and construction of wire-wound circular prestressed composite tanks; and shall give satisfactory evidence that it has the skill, reliability, and financial stability to build and guarantee the tank in accordance with the quality required by these specifications. The Company constructing the tank shall have built completely in its own name in the past five years, and be presently responsible for, a at Fire Tower Road (Brogdon)

11371-3 minimum of five (5) dome-covered prestressed composite tanks, which meet these specifications, and which are now giving satisfactory service.

C. The Tank Construction Company shall have on its staff a full-time professional engineer, who shall have no less than five-years experience in the design and field construction of circular prestressed composite tanks, and who shall be in responsible engineering charge of the work to be done. All working drawings and design calculations shall carry the seal of such registered professional engineer.

D. The intent of the Specification is to create a singular responsibility for the design and construction of the prestressed concrete tank. The design and construction of all aspects of the floor, wall, prestressing, shotcrete and dome roof of the prestressed concrete tank must be performed by the tank contractor using its owner-trained personnel and equipment.

E. Prequalification:

a. A responsive prestressed concrete tank bidder shall, no later than 15 days prior to the bid date, submit the following to the engineer for review:

i. Complete construction drawings with pertinent section details showing thicknesses and reinforcement size/spacing, including, but not limited to:

floor, corewall, dome compression ring, dome shell.

ii. Details of applicable appurtenances required by engineer or dictated by site specific parameter (ie: piping inlet, piping outlet, drain, manway, dome probe, handrail ladders, level indicator, hatch, ventilator, overflow, etc.). It will be assumed that appurtenances not detailed are not included in the tank manufacturer’s design.

iii. Complete design calculations with seismic and sliding analysis if applicable.

iv. Firm “as bid” construction schedule showing start window(s) with duration

b. Barring issuance of tank related addenda after the prequalification submittal deadline, prequalification submittals will be considered representative of the bidders’ design and approach to the project

1.05 STORAGE, PROTECTION, AND CHEMICAL COMPATIBILITY

A. Equipment and accessories shall be stored and protected in accordance with the manufacturer’s recommendations.

1.06 GUARANTEE

A. The tank Construction Company shall guarantee in writing workmanship and materials on the complete structural portion of the tank for a one-year period from at Fire Tower Road (Brogdon)

11371-4 date of acceptance of the work. In case leakage, or other defects appear with in the one-year period, the Tank Construction Company shall promptly repair the tank to the satisfaction of the Owner at Tank Construction Company’s expense upon written notice by the Owner that such defects have been found. Leakage is defined as a stream flow of liquid appearing on the exterior of the tank, or leakage through the base slab, the source of which is from the inside of the tank.

PART 2 PRODUCTS

2.01 ACCEPTABLE MANUFACTURERS

A. The ground storage tank shall be provided and installed by the CROM

Corporation, PreCon Corporation or Engineer approved equal as described in herein. These specifications and drawings represent the acceptable standard of quality, materials and methods of construction. The Contractor shall prepare his

Base Bid using either Crom Corporation, Inc., PreCon Corporation or Engineer approved equal and indicate on the Bid Form the tank supplier used in calculating the Base Bid by circling the name of the supplier of the tank in the schedule as indicated.”

2.02 PERFORMANCE

A. The design shall be in conformance with applicable portions of American Concrete

Institute (ACI) 372R-03 Design and Construction of Circular Wire- and Strand-

Wrapped Prestressed Concrete Structures, AWWA D110-04 Wire- and Strand-

Wound, Circular, Prestressed Concrete Water Tanks, and currently accepted engineering principles and practices for the design of such structures.

B. Capacity: 2,000,000 gallons per base bid

C. Dimensions: 90 ft inside diameter: 42’-1” sidewall depth per base bid

D. Roof Design Loads: Consideration shall be given to all applicable roof design loads in accordance with AWWA D110-04, Section 3.3 and ASCE 7.

E. Earthquake Design: Fixed percentage method as specified in AWWA D110-04, Section 4.1.

F. The thickness of the core wall shall be calculated so as to accept the initial compressive forces applied by prestressing, hydrostatic stresses induced by contents, and other applicable loads such as soil backfill and wind.

G. Backfill loads shall not be used in the design of the core wall to counteract hydraulic loads or provide residual compression in the wall.

H. Concrete:

11371-5

1. Concrete materials shall meet the requirements of ACI 301. Cement shall be

Portland Type I/II cement. Portland limestone cement Type C595 1L (12) MS will be allowed as a substitute by the City of Calhoun.

2. A maximum of 20% of cementitious material may be fly ash for all concrete mixes.

3. Floor Concrete: Minimum 4000 psi compressive strength at 28 days, maximum

¾" aggregate, 5% +/-1% air content, 6" +/-1" slump.

4. Dome Concrete: Minimum 4000 psi compressive strength at 28 days, maximum

⅜" aggregate, maximum 5% +/-1% air content, 4" +/-1" slump.

I. Shotcrete:

1. Shotcrete materials shall meet the requirements of ACI 506. Cement shall be

Portland Type I/II cement. Portland limestone cement Type C595 1L (12) MS will be allowed as a substitute by the City of Calhoun.

2. A maximum of 20% of cementitious material may be fly ash for all concrete mixes.

3. Core Wall Shotcrete: Minimum 4000 psi compressive strength at 28 days, 4" +/-

1" slump.

4. Covercoat Shotcrete: Minimum 3500 psi compressive strength at 28 days, 4" +/-

1" slump.

5. Allowable compressive stress due to final prestressing force, fg:

a. 1250 psi + 75t psi/in. with 0.45 f'g maximum (where f'g is defined as compressive strength required for final prestressing force and t is the thickness of the core wall in inches).

b. Maximum of 2000 psi.

6. Allowable compressive stress due to initial prestressing force, fgi:

a. 1250 psi + 75t psi/in. with 0.5 f'gi maximum or less (where f'gi is defined as compressive strength at time initial prestressing force is applied and t is the thickness of the core wall in inches).

b. Maximum of 2250 psi.

J. Prestressing Wire:

1. The prestressing wire shall conform to the requirements of ASTM A821, Type

B.

2. Wire size shall be 0.162" (8 gauge), 0.192" (6 gauge) or larger, but no larger than

0.250".

3. Working stress for the tank wall, fs shall be a maximum of 115,000 psi.

4. Working stress for the dome ring, fsd shall be a maximum of 120,000 psi.

5. Allowable design tensile stress before losses, fsi shall be 145,600 psi or no greater than 0.63 fu.

6. Ultimate tensile strength, fu shall be, 231,000 psi or greater for 8 gauge wire, 222,000 psi or greater for 6 gauge.

at Fire Tower Road (Brogdon)

11371-6

K. Non-prestressed Mild Reinforcing Steel:

1. Allowable design tensile stress, fs shall be a maximum of 18,000 psi.

2. Yield strength of reinforcing steel, fy shall be 60,000 psi.

2.03 FLOOR

A. Concrete membrane floors shall be a minimum of 6" thick and have a minimum thickness of 8" of concrete over all pipe encasements and around sumps.

B. A minimum percentage of 0.60% reinforcing steel shall be used in the membrane floor. The minimum percentage shall apply to all thickened sections and shall extend a minimum of 2' into the adjacent membrane floor.

2.04 CORE WALL

A. The core wall shall be constructed of shotcrete, encasing a steel diaphragm continuous the full wall height without horizontal splices.

B. The thickness of the core wall shall be calculated so as to accept the initial compressive forces applied by prestressing, backfill, and other applicable loads, but in no case be less than 3½" thick.

C. Horizontal sections of the wall shall form true circles without flat areas, excessive bumps or hollows.

D. Interior and exterior surfaces of the core wall shall be water cured for a minimum of

7 days or until prestressing begins.

E. To compensate for bending moments, shrinkage, differential drying, and temperature stresses, the following reinforcing steel shall be incorporated in the core wall.

1. The top 2' of core wall shall have not less than 1% circumferential reinforcing.

2. The bottom 3' of core wall shall have not less than 1% circumferential reinforcing.

3. Inside Face:

a. 26-gauge steel shell diaphragm continuous the full wall height without horizontal splices.

b. Additional vertical and horizontal reinforcing steel bars as required by design computations.

4. Outside Face:

a. Vertical reinforcing steel: Minimum of #4 bars at 12" center to center.

b. Additional vertical and horizontal reinforcing steel bars as required by design computations.

at Fire Tower Road (Brogdon)

11371-7

2.05 STEEL SHELL DIAPHRAGM

A. A 26-gauge steel tank shell, complying with ASTM A 1008, shall be used throughout the core wall, providing a waterstop. The steel shell diaphragm shall be encased and protected with shotcrete no less than 1" thick at all places.

B. The steel shell is to be formed and erected so that a mechanical key is created between the shotcrete and diaphragm.

C. The sheets of steel diaphragm shall be continuous from top to bottom of wall;

horizontal joints or splices will not be permitted.

D. All vertical joints in the diaphragm shall be sealed watertight by epoxy injection.

E. Epoxy injection shall be carried out from bottom to top of wall, using a pressure pumping procedure, after the steel shell has been fully encased, inside and outside, with shotcrete.

F. The sealant shall conform to the requirements of ASTM C881, Type III, Grade 1, and shall be 100% solids, moisture insensitive, low modulus epoxy system. When pumped, maximum viscosity of the epoxy shall be 10 poises at 77°F.

G. The epoxy sealant shall be suitable for bonding to concrete, shotcrete, and steel.

H. In all tanks designed to use a waterstop at the floor/wall joint, the steel shell diaphragm shall be epoxy bonded to this waterstop.

2.06 SHOTCRETE

A. All shotcrete shall be applied by or under direct supervision of experienced nozzlemen certified by the American Concrete Institute (ACI) as outlined in ACI certification publication CP-60.

B. Shotcrete mixes shall have a minimum of 1 part cementitious material to 3 parts of sand.

C. Each shotcrete layer shall be broomed prior to final set to effect satisfactory bonding of the following layer.

D. No shotcrete shall be applied to reinforcing steel or diaphragm that is encrusted with overspray.

E. No less than ⅛" thick shotcrete shall separate reinforcing steel and prestressing wire.

at Fire Tower Road (Brogdon)

11371-8

2.07 DOME ROOF

A. The dome roof shall be constructed of reinforced concrete and circumferentially prestressed.

B. Dome shell reinforcement shall consist of reinforcing bars or welded wire fabric meeting ASTM A185, not galvanized. Bolsters for wire fabric and reinforcing bars shall be plastic tipped. Wire ties shall be galvanized.

C. The dome ring girder shall be prestressed with sufficient wire to withstand the dome dead load and design live loads. The ring girder shall have cross section suitable to accept the applied prestressing forces.

D. The high-water level in the tank shall be permitted to encroach on the dome shell no higher than the upper horizontal plane of the dome ring girder.

E. Overflow outlets or the overflow pipe shall be capable of providing an open overflow area three times the area of the largest tank pipe.

F. The dome roof shall be cured for a minimum of 7 days or until prestressing begins.

G. The dome shall be designed as a free-span, spherical thin shell with one-tenth rise in accordance with the following:

1. Typical Dome Design: The typical dome thickness and steel reinforcement shall meet the requirements of AWWA D110-04, Section 3.6.3. "Thickness and reinforcement". In all cases, the thickness of the dome shall be no less than 3".

2. Dome Edge Design: The dome edge and upper wall shall be designed to resist the moments, thrusts, and shears that occur in this region due to dome and wall prestressing and loading conditions. The following design parameters shall be used.

a. Dome Edge Thickness:

(1) A determination of the buckle diameter shall be made, as defined by:

ddb trd = 5.2 rounded up to the next foot

Where: bd = buckle diameter in feet dr = dome radius in feet dt = typical dome thickness in feet at Fire Tower Road (Brogdon)

11371-9

(2) Dome edge thickening shall begin at a radial location on the dome, defined as 2s which is at least one buckle diameter away from the tank wall.

(3) A springline haunch shall be provided, which extends radially from the inside face of the tank wall to radial location 1s which is defined as:

dd trs = 5.16.01 rounded up to the next foot

This springline haunch shall begin at the inside face of the tank wall with a springline thickness as required by paragraph (6) below and shall end at radical location 1s with the following thickness:

dd tt = 33.11

Where: 1dt = minimum thickness at 1s in feet dt = typical dome thickness in feet at one buckle diameter from tank wall

(4) Beginning at 1s and continuing to 2s the dome shell shall be a straight line taper.

(5) Parameters (2), (3), and (4) above are not required for domes where the calculated typical dome thickness is less than 75% of the actual typical dome thickness.

(6) Sufficient concrete thickness at the springline of the dome shall be provided so that no more than 2' of the springline haunch is considered in calculating the effective dome edge ring cross sectional area.

Compressive stress in this area shall not exceed 1000 psi when subjected to initial prestressing, offset by dead load only.

b. Dome Edge Steel Reinforcement

(1) Throughout the dome edge, the percentage of steel reinforcement, both radially and circumferentially, shall be no less than 0.25% of the gross cross-sectional area of concrete.

(2) Along the dome edge, steel reinforcement shall be distributed between the upper and lower layers unless finite element analysis calculations indicate that tensile stress does not exist in the concrete along the bottom face of the dome edge. In that case, only top bars are required radially and circumferentially. In addition, radial and circumferential reinforcing bars will not be required along the bottom face of the dome at Fire Tower Road (Brogdon)

11371-10 edge where the calculated typical dome thickness is less than 75% of the actual typical dome thickness.

(3) Where reinforcing bars are required in the bottom layer, they shall be anchored near the tank wall to ensure adequate development at the intersection between dome and wall.

(4) In all cases, the percentage of circumferential steel reinforcement in the first 2' of the dome edge shall be no less than one percent of the gross cross-sectional area of concrete.

(5) Where bottom dome edge steel reinforcement is required, vertical steel reinforcement along the inside face of the tank wall shall be no less than 0.5% of the cross-sectional area of wall shotcrete.

2.08 HORIZONTAL PRESTRESSING

A. Circumferential prestressing of the tank shall be achieved by the application of cold-drawn, high-carbon steel wire complying with ASTM 821 Type B, placed under high tension. A substantial allowance shall be made for prestressing losses due to shrinkage and plastic flow in the shotcrete and due to relaxation in the prestressing steel.

B. Placement of the prestressing steel wire shall be in a continuous and uniform helix of such pitch as to provide in each lineal foot of core wall height an initial force and unit compressive stress equal to that shown on the design drawings. Splicing of the wire shall be permitted only when completing the application of a full coil of wire or when removing a defective section of wire.

C. Areas to be prestressed will contain not less than 10 wires per foot of wall for 8-gauge and 8 wires per foot of wall for 6-gauge. A maximum of 24 wires per layer per foot for 8-gauge and 20 wires per layer per foot for 6-gauge will be allowed.

Shotcrete shall be used to completely encase each individual wire and to protect it from corrosion. To facilitate this encasement, the clear space between adjacent wires is to be no less than one wire diameter.

D. Prestressing shall be accomplished by a machine capable of continuously inducing a uniform initial tension in the wire before it is positioned on the tank wall. Tension in the wire shall be generated by methods not dependent on cold working or re-drawing of the wire. In determining compliance with design requirements, the aggregate force of all tensioned wires per foot of wall shall be considered rather than the force per individual wire, and such aggregate force shall be no less than that required by the drawings.

E. The tank construction company shall supply equipment at the construction site to measure tension in the wire after it is positioned on the tank wall. The stress at Fire Tower Road (Brogdon)

11371-11 measuring equipment shall include electronic direct reading stressometer accurate to within 2%, calibrated dynamometers and a test stand to verify the accuracy of the equipment.

F. After circumferential prestressing wires have been placed, they shall be protected by encasement in shotcrete. This encasement shall completely encapsulate each wire and permanently bond the wire to the tank wall.

G. When multiple layers of wire are required, shotcrete cover between layers shall be no less than ⅛" thick.

H. After all circumferential prestressing wires have been placed, a shotcrete cover having a thickness of no less than 1" shall be placed over the prestressing wires.

2.09 WALL OPENINGS

A. When it is necessary for a pipe to pass through the tank wall, the invert of such pipe or sleeve shall be no less than 18" above the floor slab, and the prestressing wires required at the pipe elevation shall be distributed above and below the opening leaving an unbanded strip around the entire tank.

B. Unbanded strips shall have a vertical dimension of no more than 36" unless an axi-symmetric shell analysis is performed to account for shear and moments caused by displacement of the prestressing wires into adjacent bands.

C. All wall pipes and sleeves passing through the wall shall be sealed to the steel shell diaphragm by epoxy injection.

2.10 TANK ACCESSORIES

A. The tank construction company shall furnish, install and guarantee for five (5) years the follow tank accessories.

B. The tank shall have a minimum of one, 1'-8" x 2'-8" (inside clearance or larger to accommodate scaffolding) rectangular Type 316 stainless steel wall manway for access to the interior of the tank. The cover and the bolts shall be of Type 316 stainless steel.

C. Exterior ladder made of T6061 aluminum with Type 316 stainless steel fasteners, safety cage, gate, and safety climbing system conforming to applicable OSHA standards.

D. Interior ladder made of T6061 aluminum with Type 316 stainless steel fasteners and safety climbing system conforming to applicable OSHA standards.

at Fire Tower Road (Brogdon)

11371-12

E. Roof hatch cover, roof ventilator, and liquid level indicator shall be made of fiberglass with Type 316 stainless steel fasteners.

F. Through-wall pipe sleeves shall be Type 316 stainless steel sleeves with neoprene modular-seal units using stainless steel tightening bolts.

2.11 PAINTING

A. Substrate shall be clean, dry, and free of contaminants prior to coating.

B. Exterior paint system shall consist of the following system:

1. Two coats of Tnemec Series156 Enviro-Crete Modified Waterborne Acrylate or

Engineer approved equal applied at 4.0 – 6.0 mils per coat. Minimum 8.0 total

DFT.

C. Paint shall be applied a minimum of 28 days after final application of shotcrete. All application procedures for paint shall be in accordance with manufacturer’s recommendations. COLOR TO BE SELECTED BY OWNER

PART 3 EXECUTION

3.01 EXAMINATION

A. Verify elevations, placement and grading for tank prior to starting tank construction.

3.02 INSTALLATION

A. Tank Floor:

1. The floor shall be vibratory screeded to effect consolidation of concrete and proper encasement of floor reinforcing steel.

2. The floor shall be continuously water cured until tank construction is completed.

B. Tank Wall:

1. The wall shall be constructed in a predesigned manner utilizing steel shell diaphragm, layers of shotcrete and prestressing wire.

2. The diaphragm shall be protected against damage before, during, and after erection. Nail or other holes shall not be permitted in the steel shell for erection or other purposes except for inserting wall pipes or sleeves, reinforcing steel, bolts, or other special appurtenances. Such penetrations shall be sealed with an approved epoxy sealant.

at Fire Tower Road (Brogdon)

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3. Interior and exterior portions of the shotcrete wall shall be water cured for a minimum of 7 days or until prestressing is started.

C. Roof:

1. All concrete shall be consolidated by means of a vibrator for proper encasement of reinforcing steel and welded wire fabric.

2. All surfaces at the joint between the wall and the dome shall be coated with an approved bonding epoxy.

3. Dome shall be water cured for 7 days after casting or until prestressing is completed.

D. Prestressing: The initial tension in each wire shall be read and recorded to verify that the total aggregate force is no less than that required by the design. Averaging or estimating the force of the wire on the wall shall not be considered satisfactory evidence of correct placement of prestressing wires.

3.03 FIELD QUALITY CONTROL

A. Weather Requirements:

1. Cold weather pours: Ambient temperatures must remain above 39.5° F until the concrete has reached the design strength threshold. Heated blankets will only be considered for the floor slab and structures below grade.

2. Warm weather pours: Ambient temperatures must remain below 95.5° F until the concrete has reached the design strength threshold.

B. Inspection and Testing:

1. Hydrostatic Testing: Test completed tank for liquid tightness by filling tank to its overflow elevation with water provided by Owner. The tank shall remain filled for a period of at least 24 hours to allow for absorption. The liquid volume loss for a period of 24 hours shall not exceed one-twentieth of one percent of the tank capacity. If the liquid volume loss exceeds this amount, leakage shall be considered excessive, and the tank shall be repaired and retested.

2. Cold Concrete and Shotcrete Testing: Test all concrete and shotcrete used in the tank structure in accordance with Section 03300.

3.04 CLEANING AND DISINFECTION

A. Clean interior and exterior of tank to remove debris, construction items, and equipment.

B. Disinfection Procedure: Use AWWA C652 Method 2.

C. The Contractor shall collect the water samples and the Owner shall perform bacteriological testing.

11371-14

3.05 WATER FOR CLEANING & TESTING

A. The Owner will furnish without costs to the Contractor the potable water necessary for hydrostatic testing and disinfecting the tank one (1) time. If tank fails the hydrostatic test and/or the bacteriological test and additional water is needed for re-testing, the Contractor shall reimburse Owner at current commercial rates for all water required for re-testing.

END OF SECTION