Where actual cost exceeds estimated cost; additional work; assessment for same.

Whenever during the construction of any drain or auxiliary thereto, and before the completion thereof, it shall be made evident to the board of county commissioners that the actual cost thereof will exceed the estimated cost thereof, or that further or additional work is necessary to complete said drain or auxiliary not covered or provided for in the original contract of construction, the said board of county commissioners may enter into any or all additional contracts for the additional work necessary to complete said drain or auxiliary thereto without advertising for bids thereon, and they shall make the best contract they can for the interests of the property owners, whose lands have been and will further be assessed to construct said ditch or auxiliary, and said board of county commissioners, shall make all further and necessary assessments against the lands already assessed to pay all necessary costs and charges for the full completion of said drain or auxiliary.