Upon finding by the Director that the standards and specifications set forth in this Chapter 104 would, for a particular project, impose an unreasonable hardship and a variance would not: 1) violate the spirit and intent of this chapter, 2) cause or be likely to cause substantial injury to the public health, safety and general welfare; 3) be injurious to other property or improvements to the neighborhood; or 4) substantially increase the congestion of public streets, alternate standards and specifications, in accordance with good engineering principles, may be approved. Such alternate requirements shall be part of and a condition of the public works agreement.