(CBS) — It has been six weeks since a six-year-old boy was rescued after being swallowed up by a mysterious hole on Mt. Baldy. Today, they’re hauling more equipment onto the closed sand dune as they continue to try to solve the mystery.

The fences and ropes protecting areas of Mt. Baldy for a grass restoration project have been coming down to make way for the EPA to come in and perform a ground conductivity survey.

The science behind the survey, which uses electromagnetic waves, is used by archaeologists to locate underground structures.

Park Ranger Bruce Roe says it is a fairly quick way to survey all 42 acres of Mt. Baldy.

He says any anomalies can then get a closer look with ground-penetrating radar.

On Wednesday Nathan Woessner, the seven-year-old boy who survived being buried under Mt. Baldy, will be reunited with the first-responders who rescued him in a ceremony at City Hall in Michigan City.

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