The nutrient management plan shall also provide for a site, with or without a permanent structure, for the storage of poultry wastes. The site shall be located on the same parcel as the poultry house to which it is an accessory use. If, however, a grower whose facilities were in operation prior to July 9, 1991, is unable to locate a site on the same parcel because of insufficient acreage or topographical hardship, then the Zoning Administrator, after consultation with the grower's engineer, may permit the storage site to be located on adjacent land owned by the grower; or if the grower has a valid agreement for off-site disposal, as provided for above, the Zoning Administrator may permit the storage site to be located on a parcel specified in the agreement for off-site disposal. A professional engineer registered in Virginia, a representative of the Lord Fairfax Soil and Water Conservation District or a representative of the United States Department of Soil Conservation Service shall certify that the site:
(1) Is out of all drainageways.
(2) Is protected from the elements.
(3) Has sufficient capacity to accommodate 100% of the waste produced by the poultry facility's operation on the parcel during the four consecutive months in which the maximum number of cleanouts of such poultry facilities may occur.