Whenever obstructions are encountered during the progress of the work and interfere to such an extent that an alteration in the plan is required, the Engineer shall have the authority to approve the plans and order a deviation from the line and grade or arrange with the owners of the structures for the removal, relocation or reconstruction of the obstructions. Where gas, water, telephone, electrical, hot water, steam, or other existing utilities are an impediment to the vertical or horizontal alignment of the proposed pipe line, the engineer shall require a change in grade or alignment or shall direct the Contractor to arrange with the owners of the utilities for their removal.