The Arizona Diamondbacks became very familiar with this situation during construction of the players' parking lot at the Bank One Ballpark in Phoenix. Unknown to all parties involved, the parking lot was built on a dried out riverbed. This riverbed consisted of cobbles that were unable to sufficiently support the pressure of the structure above it. As a result, the parking lot began to sink.
O'Brian Concrete Pumping was contracted to raise the parking lot to its original height and secure the structure in place. O'Brian knew they must reinforce the parking lot by pumping concrete under it and fast. O'Brian consulted TEI Rock Drills of Montrose, CO, who suggested drilling with a Numa Champion 35 down hole hammer off a Bobcat 835 with TEI's HCM 528 drilling attachment. This method would provide an inexpensive and quick means to drill the holes while insuring safety of other nearby structures - like the brand new multi-million-dollar baseball park.
The project required holes to be drilled 20 to 30 feet (6.1 - 9.2 m) deep to reach the area where concrete could be pumped under the structure to raise it and secure it in place. All drilling was conducted off a Bobcat/TEI rig that supplied 250 cfm (118 l/sec) and 150 psi (10.2 bar) of air to a Numa Champion 35 down hole hammer. After each 3-1/2" (89 mm) diameter hole was completed, casing was installed and concrete pumped down to raise the lot. The Champion 35 hammer more than lived up to its reputation as it successfully drilled more than 50 holes within several days, which enabled O'Brian to successfully complete the project in plenty of time before the new baseball season began.