To the Editor:
I am not sure that the sinkhole is being filled in properly, especially if the sinkhole went under the sidewalk or any adjacent pavement. If the sinkhole created a void under the sidewalk, placing sand in the sinkhole will not provide proper support for the sidewalk or adjacent pavement if there is any. Rather, a concrete mix should have been placed in the void. A concrete having a moderate slump of say 6 to 8″ should be used to fill the sinkhole up to within approximately 4″ to 6″ below the bottom of the concrete sidewalk or pavement and the remaining void should be filled with what is known in the industry as a flowable (high slump) concrete. Alternatively, a product generically known as “Controlled Low Strength Concrete” can be used. This material, which reaches a compressive strength of 100 to 200 pounds per square inch (psi) is more than adequate to support the sidewalk or pavement. This type of material is strong enough to bear traffic once hardened.
Stuart Jacobson
Village of Gilchrist