Buffer Required. A minimum 10-foot landscaped buffer or screen shall be required around the sides and rear of the park. The front yard buffer shall be a minimum of 20 feet, within which shall be erected an ornamental wall, fence, or screen planting, acceptable to the administrative official, and no less than five feet in height around the perimeter of the manufactured home park. If screen plantings are to be used, the plants should be of sufficient size so as to provide immediate screening benefit. If, in the opinion of the planning commission, it is unreasonable to require this screening along the side and rear boundaries due to the nature of the existing topography or other conditions that might render such screening ineffective, the commission, at its discretion, may waive or modify the requirements as specified in this section. A permanent irrigation system shall be installed to ensure adequate maintenance of the landscaping in these areas.