Outdoor repair activities involving boats, vehicles, trailers and other mechanical equipment may not be undertaken on any property in the POB, NB or GB Zone Districts used only for residential purposes or on any property in a residential zone, except under the following restrictions: observance of the restrictions of subsection 22-5.3b, 18; no more than one item may be under repair at any time and repairs may not be performed on an aggregate total of more than 30 days in any year. Such outdoor repair activities may not be undertaken on any property in the POB, NB or GB Zone Districts not used only for residential purposes except in accordance with specific site plan approval by the Municipal Agency.