Only contiguous lands located within the same zoning district and Pinelands management area as the proposed system or systems may be utilized for septic dilution purposes, except for the development of an individual single-family dwelling on a lot existing as of January 14, 1981, nonresidential development on a lot of five acres or less existing as of January 14, 1981, or cluster development as permitted by N.J.A.C. 7:50-5.19;