A timing source for a pulse generator is disclosed, which timing source includes an input for receiving a reference clock output at a reference operating frequency. A cover with a V-groove defines an optical axis. The mandrel is then moved upwardly from the bottom of the cavity and aggregate is deposited in the bottom of the cavity following which the mandrel is lowered so that its lower end engages the deposited aggregate and densifies the aggregate by vertical vibratory action and static force with these steps being repeated until the pier top is near the surface of the earth.