With the coping lying on the ground, mark around the inside edge of the coping with marking paint or dig a line into the earth with a spade.  The coping should then be removed to a safe place out of the way of construction.  Power excavation equipment such as a back-hoe or track-hoe should be brought into the center or outside edge of the area to be excavated and the excess material (dirt, rocks, etc) taken out.  If the material is needed to build up another area for obstacles or other uses it can be taken there at this time.  Use an excavation jig to get as close as possible to the final dimensions called for in the design.  Be sure to allow for the depth of concrete and any gravel substrate.

Excavation jig.

For accurate excavation it will be necessary to build a jig to guide the person operating the excavation equipment.  Fabricate the jig from ¾-inch plywood.  For large radial transitions, plywood can be purchased in 12-feet long sheets at most lumber yards.  Draw a radius equal to the transition desired onto the plywood.  Cut out the radius and cut handles into the plywood to aid in moving it around.  Place a 2 x 4 across the center of the jig so that a masonry level, when placed on the 2 x 4, guarantees the jig is in the proper position.  As material is removed during excavation, place the upper edge of the jig in line with the ground, make sure it is level, and use the curved edge of the jig to determine high or low spots, and remove or add more material as needed. 

This first excavation will be somewhat free-hand.  A much more exact excavation will be performed after the coping has been set in place.  Overall, careful attention must be shown during all phases of excavation as the removal of material beyond what is called for will result in the need for additional concrete.  Over cutting by even an inch in a modest-sized park would result in additional concrete costing several thousands of dollars.

Once the coping has been placed, fabricate a metal hanger from a piece of angle steel notched to fit around the outside diameter of the coping.  Attach that hanger to the excavation jig with nuts, bolts and washers.  After the coping has been set in place and leveled, the jig will hang from the coping to show precisely the amount of material to be removed or added.  Excavate carefully and accurately.  It will never get any better than what you settle for at this point without costing you more money in the form of additional concrete.

With the coping lying on the ground, mark around the inside edge of the coping with marking paint or dig a line into the earth with a spade.  The coping should then be removed to a safe place out of the way of construction.  Power excavation equipment such as a back-hoe or track-hoe should be brought into the center or outside edge of the area to be excavated and the excess material (dirt, rocks, etc) taken out.  If the material is needed to build up another area for obstacles or other uses it can be taken there at this time.  Use an excavation jig to get as close as possible to the final dimensions called for in the design.  Be sure to allow for the depth of concrete and any gravel substrate.

Excavation jig.

For accurate excavation it will be necessary to build a jig to guide the person operating the excavation equipment.  Fabricate the jig from ¾-inch plywood.  For large radial transitions, plywood can be purchased in 12-feet long sheets at most lumber yards.  Draw a radius equal to the transition desired onto the plywood.  Cut out the radius and cut handles into the plywood to aid in moving it around.  Place a 2 x 4 across the center of the jig so that a masonry level, when placed on the 2 x 4, guarantees the jig is in the proper position.  As material is removed during excavation, place the upper edge of the jig in line with the ground, make sure it is level, and use the curved edge of the jig to determine high or low spots, and remove or add more material as needed. 

This first excavation will be somewhat free-hand.  A much more exact excavation will be performed after the coping has been set in place.  Overall, careful attention must be shown during all phases of excavation as the removal of material beyond what is called for will result in the need for additional concrete.  Over cutting by even an inch in a modest-sized park would result in additional concrete costing several thousands of dollars.

Once the coping has been placed, fabricate a metal hanger from a piece of angle steel notched to fit around the outside diameter of the coping.  Attach that hanger to the excavation jig with nuts, bolts and washers.  After the coping has been set in place and leveled, the jig will hang from the coping to show precisely the amount of material to be removed or added.  Excavate carefully and accurately.  It will never get any better than what you settle for at this point without costing you more money in the form of additional concrete.

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