Final answer:
Without concrete strength data and safety factor information, it is impossible to assess the safety of a 20" x 20" concrete pier supporting 300,000 lbs. Safety evaluation requires the allowable stress of the material to be compared with the stress caused by the load, which cannot be determined from the information provided.
Step-by-step explanation:
The question asks whether a 20" x 20" concrete pier can safely support a load of 300,000 lbs. To investigate the safety of the concrete pier, one must consider factors such as the compressive strength of the concrete, the design and distribution of the load, local building codes, and safety factors. In the absence of specific material properties and design codes, it is not possible to definitively say whether the pier is safe or unsafe. Typically, engineers would calculate the stress on the concrete pier by dividing the total load by the cross-sectional area of the pier. The resulting stress would then be compared to the allowable stress for the concrete used in the pier's construction. A pier is deemed unsafe if the stress exceeds the material's allowable stress. Given the lack of detailed information, including the strength of the concrete and the factor of safety applied, no accurate assessment can be provided. Therefore, we cannot conclude if it's safe or unsafe without further details.