The Parks Department of Columbus hired a private archaeology firm to test the site for evidence that the two mounds were man made. The test and the report are not described in any detail, but the bottom line was "no evidence" that the mound was artificial.
See the exceedingly brief report at the Columbus Dispatch. The test may well have been a simple "shovel" test. If no artifacts were found, I'm unsure if that alone could have determined with the mound was built up by baskets of earth. I infer by the photographs that the renovation of the park was well underway when the test was made.
Something is not right. This message is just to keep things from messing up down the road