Common use of Casing Clause in Contracts

Casing. Use casings if the elevation of the top of the caissons is at or below the ground or expected high water elevation at any time during construction. If casings are used, set the elevation at the top of the casing a minimum of 2 feet (600 mm) above the ground or 4 feet (1200 mm) above the expected high water elevation at the site, whichever is greater. Cut off any permanent casing used as shown on the Plans. Use casing that is a metal shell of a thickness to withstand handling, internal and external pressures, and that is watertight, smooth and clean. If the elevation of the top of the caisson is below ground level or water level at the time of concrete placement, use an oversize casing from ground elevation to a point below the top of the caisson to prevent soil from caving into the fresh concrete. Do not allow the top of the permanent casing, if required, to extend above the top of the drilled caisson. Use casing in all materials that do not have sufficient strength to safely remain open and stable during and after excavation. When casing is used, do not use casing with an outside diameter less than the specified diameter of the caisson. That portion of the caisson below the casing may be slightly smaller than the normal outside diameter of the caisson. However, use drilling tools to excavate the caisson below the casing that are no smaller than the Plan diameter of the caisson minus 2 inches (50 mm). Do not leave casing in place unless permitted by the Engineer, and cut off any permanent casing as shown on the Plans. Provide adequate equipment during concrete placement to prevent pulling up the reinforcing cage during casing extraction. The casing may be pulled in partial stages. Maintain a sufficient head of concrete above the bottom of the casing to overcome hydrostatic pressure. Extract the casing at a slow uniform rate with pull in line with the center of the caisson. In open-water locations, provide containment at the top of the casing to prevent any material from spilling into the water. Install casing to a depth and in a manner that will produce a positive seal at the bottom of the casing. Do not allow water or other materials, into or out of the excavation area at or below the bottom of the casing. Do not leave casings in place unless permitted by the Engineer. If casings that are to be removed become bound in the caisson excavation and cannot be practically removed, or if the permanent casing is lowered below the proposed tip elevation, drill the caisson excavation deeper and extend the caisson, including reinforcement, as directed by the Engineer to compensate for loss of capacity due to the presence of the casing. No compensation will be made for the casing remaining in the excavation. The additional length of caisson including excavation, reinforcing steel, concrete and other items incidental to the Work will be paid for at the unit bid price for drilled caissons.