5.3.3 Permanent Markers

All intersections of the subdivision boundary property line and all intersections of street property lines within the subdivision shall be marked with permanent monuments.  Monuments of ferrous material must have at least a one-half inch diameter, and must be at least 18 inches in length (longer in soft or unstable soil). Concrete monuments shall be at least 4 inches in width by 24 inches in length, reinforced with an iron rod at least one-fourth inch in diameter.  All monuments shall contain a precise mark on top indicating the exact location of the corner. Should conditions prohibit the placing of monuments in line, off-set marking will be permitted, provided, however, that exact off-set courses and distances are shown on the subdivision plat.  Where a benchmark is not existing within reasonable distance, a permanent benchmark shall be accessibly placed, the elevation of which shall be based on the North American Datum of 1983 (NAD 83) for horizontal control and the North American Vertical Datum of 1988 (NAVD 88) for vertical control, as determined by the National Geodetic Survey (NGS), and accurately noted on the subdivision plat.