The commission shall limit all assessments to the special benefits conferred upon the property assessed, and in no case shall there be levied on any lot or parcel of land any assessments for any or all purposes within a period of five years in excess of thirty-three and one-third per cent (33-1/3%) of the actual value thereof after the improvement is made. Assessments levied for the construction of main sewers shall not exceed the sum that, in the opinion of the commission, would be required to construct an ordinary street sewer or drain of sufficient capacity to drain or sewer the lots or lands to be assessed for such improvement, nor shall any lots or lands be assessed that do not need local drainage, or which are provided therewith.