artificial obstruction造句

If during the execution of the Works the Contractor shall encounter physical conditions ( other than weather conditions or conditions due to weather conditions ) or artificial obstructions which conditions or obstructions could not in her / his opinion reasonably have been foreseen by an experienced contractor the Contractor shall as early as practicable give written notice thereof to the Engineer.
It's difficult to find artificial obstruction in a sentence. 用artificial obstruction造句挺难的