(c)    The board may grant a variance to the stormwater management requirements of article V only if at least one of the following conditions exist:

(1)    Alternative requirements for onsite management of stormwater discharges have been established in a stormwater management plan approved by the director.

(2)    Provisions are made to manage stormwater by an existing offsite facility that is adequately sized to provide a level of stormwater control at least equal to that which would be afforded by onsite practices and there is a legally obligated entity responsible for long-term maintenance of the offsite facility.

(3)    The board finds that meeting the minimum onsite management requirements is not feasible because of physical characteristics of the site.

The board may not vary the stormwater management requirements of article V if the variance would result in any of the following impacts in the downstream waterway:

    (1)    Deterioration of existing culverts, bridges, dams or other structures;

    (2)    Degradation of biological functions or habitat;

    (3)    Accelerated stream bank or stream bed erosion or siltation;

    (4)    Increased threat of flood damage.

If a variance granted by the board will likely result in a lower level of stormwater control, the board shall impose reasonable mitigation measures including, but not limited to, the following:

(1)    The purchase and donation of privately owned lands or the grant of an easement to be dedicated for preservation or reforestation.  These lands must be adjacent to a stream corridor in order to provide permanent buffer areas to protect water quality and aquatic habitat.

(2)    The construction of a stormwater management facility or other drainage improvements on previously developed property, whether public or private, which currently lacks stormwater management facilities, designed and constructed in accordance with the standards and purposes of this chapter and the city’s Stormwater Management and Water Quality Manual.

(3)    At the petitioner’s request, monetary contributions to fund stormwater related studies and projects including regional wetland delineation studies, stream monitoring studies, hydrologic studies, stream assessment studies, including stream monitoring studies for water quality and macroinvertebrates, stream flow monitoring, threatened and endangered species studies and stream restoration projects.  The monetary contribution shall be in accordance with a schedule established by the director and shall be based on the cubic feet of storage required but not provided for the stormwater management of the property in question.