525.1 General Description
This work consists of designing, constructing, maintaining, dewatering, removing, and disposing of cofferdams, which are necessary for constructing substructures and for protecting personnel and adjacent structures, roadbeds, tracks, channels, slopes, or other property (public or private) whether on or off the Rights-of-Way from water, caving soil, and other dangers.
525.1.01 Definitions
General Provisions 101 through 150.
525.1.02 Related References
A. Standard Specifications Section 109—Measurement and Payment Section 211—Bridge Excavation and Backfill Section 500—Concrete Structures B. Referenced Documents General Provisions 101 through 150.
525.1.03 Submittals
A. Drawings The Engineer may require the Contractor to submit drawings of proposed cofferdams for review. If this is required, the Contractor shall not start work until the Engineer completes the review. The review will not relieve the Contractor of the responsibility for providing an adequate and safe cofferdam.
525.2 Materials
Materials used in cofferdam construction may be of any type suitable for the design requirements and for the particular dam being constructed, subject to the Engineer’s approval. Earth dams, sand bags, or dams constructed using excavated materials are not considered cofferdam construction.
525.2.01 Delivery, Storage, and Handling
General Provisions 101 through 150.
525.3 Construction Requirements
525.3.01 Personnel
General Provisions 101 through 150.
525.3.02 Equipment
A. Pumps Supply sufficient pumping capacity to dewater the cofferdam.
525.3.03 Preparation
General Provisions 101 through 150.
525.3.04 Fabrication
General Provisions 101 through 150.
525.3.05 Construction
A. Designing Cofferdams Cofferdams shall be structurally adequate to withstand external and internal forces including the following: 1. Forces and pressures from an excavation depth of not less than 6 ft. (1.8 m) below the elevation of the bottom of the footing 2. Forces and pressures from surcharge loads from adjacent structures, roadbeds, tracks, slopes, and equipment. Design the cofferdam to meet these conditions: • Cofferdams shall permit placing pumping equipment outside the footing forms. • Cofferdams shall permit driving piling between braces. • Cofferdams shall be watertight to permit the construction of the footings, seals, or substructure. B. Correcting Cofferdams Correct to the Engineer’s satisfaction cofferdams that tilt or move laterally during construction. C. Lowering Cofferdams Substructure elevations shown on the Plans are approximate; therefore, the Engineer may require that both substructures and cofferdams be lowered by a specified amount. D. Dewatering Cofferdams Try to dewater cofferdams without using seal concrete unless the plans require seals. 1. Dewatering Cofferdams Without Seal Concrete Use all reasonable methods to provide a dewaterable enclosure, including the following: a. Drive all sheeting within the cofferdam to a depth of at least 1 ft. (300 mm) below the bottom of the excavation. b. Provide a double-walled cofferdam lined with clay or other reasonably impervious material. The Engineer decides if the Contractor has used all reasonable methods to provide watertight cofferdams. If the enclosures are not dewaterable, and the Engineer decides the Contractor has not used all reasonable methods to provide watertight cofferdams, the Engineer may do either of the following: • Require the Contractor to place Seal Concrete at the Contractor’s expense. • Permit the Contractor to place Seal Concrete at the Contractor’s expense instead of trying further dewatering methods without a seal. 2. Dewatering Cofferdams with Seal Concrete If all reasonable methods to provide a dewaterable enclosure have been used and the Engineer determines that seal concrete is necessary, place the concrete as outlined in Subsection 500.3.05.V, Place Seal Concrete. When using seal concrete, dewater the cofferdam no earlier than 24 hours after the concrete is placed unless the Engineer determines that a longer period is necessary. E. Removing Cofferdams Unless otherwise specified, completely remove all cofferdam material. This material shall remain the property of the Contractor.
525.3.06 Quality Acceptance
General Provisions 101 through 150.
525.3.07 Contractor Warranty and Maintenance
General Provisions 101 through 150.
525.4 Measurement
A. Measuring Cofferdams for Separate Payment Cofferdams will be measured for separate payment only when set up as a Pay Item on the plans. Separate measurement will be made only for cofferdams constructed at the specific locations required on the plans, regardless of cofferdams built at other locations within the limits of the structure and regardless of site conditions. The Contractor may request permission to enclose more than one footing in a single cofferdam at a pay measurement location. If the Engineer approves, the number of cofferdams measured for payment will equal the number of footings enclosed within that single cofferdam. If cofferdams are not set up as a Pay Item on the plans and their use becomes necessary, they will not be measured for payment. B. Measuring Lowered Cofferdams for Payment The following restrictions apply to lowered cofferdams: 1. If lowering a footing requires lowering a separately measured cofferdam, lower the cofferdam enough distance to permit construction at an elevation not to exceed 6 ft. (1.8 m) below Plan elevation at the Contractor’s expense. 2. Any lowering of a cofferdam to permit construction at an elevation more than 6 ft. (1.8 m) below plan elevation will be paid for as Extra Work. 3. The Specifications intend that no Extra Work be paid for lowering a separately measured cofferdam until the Contractor completes the cofferdam to the extent that footings or substructure can be successfully constructed at an elevation no more than 6 ft. (1.8 m) below plan elevation. No Extra Work shall be done under this Item until the requirements of Subsection 109.05, Extra Work have been met.
525.4.01 Limits
General Provisions 101 through 150.
525.5 Payment
A. Cofferdams Measured for Separate Payment. Each cofferdam eligible for separate measurement and payment will be paid for at the Contract Price per each, complete in place, maintained, dewatered, removed, and disposed of. B. Cofferdams Not Measured for Separate Payment. The cost of cofferdams not measured for separate payment will be included in the Contract Price for bridge excavation. If lowering a footing requires lowering a cofferdam not measured for separate payment, the compensation for extra depth excavation provided for in Subsection 211.5.A, “Bridge Excavation”, will be full compensation for the cost of lowering the cofferdam. Payment for cofferdams eligible for separate measurement will be made under the following: Item No. 525 Cofferdams Per each
525.5.01 Adjustments
A. Partial Payment Adjustments Partial payment for measured cofferdams will be made as follows: 1. After a satisfactory initial dewatering of the cofferdam, 75 percent of the Contract Price per cofferdam will be included in the next statement. 2. The remaining 25 percent will be included in the next statement after the satisfactory removal and disposal of the cofferdam. B. Extra Work Qualifications When the excavation elevation reaches 6 ft (1.8 m) below the Plan elevation and the cofferdam is satisfactory (as determined by the Engineer) for dewatering to that elevation, then any lowering of the cofferdam to permit construction at an elevation more than 6 ft (1.8 m) below Plan elevation will be considered Extra Work.
Cofferdams in other states
Get an email when 525 changes
Georgia revises spec sections through supplementals and new editions. We check this one every week and email you the day it changes. Free, no account.