|(a) The owner or operator must maintain the visibility of all required landfill markers and the benchmark. The owner or operator shall inspect landfill markers on a monthly basis and maintain records of all inspections at the facility. The owner or operator shall replace markers within 15 days of removal, destruction, or a determination that the markers do not meet regulatory requirements. (b) Landfill markers must be installed to clearly mark significant features. The executive director may modify specific marker requirements to accommodate unique site-specific conditions. (1) All markers must be posts extending at least six feet above ground level. Markers must not be obscured by vegetation. Sufficient intermediate markers must be installed to show the required boundary. Markers must be installed at the following locations and color coded as follows: (A) black - facility boundary markers; (B) yellow - buffer zone markers; (C) green - easement and rights-of-way markers; (D) white - landfill grid system markers; (E) red - soil liner or geomembrane liner area markers; and (F) blue - 100-year flood protection markers. (2) Facility boundary markers must be placed at each corner of the facility and along each boundary line at intervals no greater than 300 feet. Fencing may be placed within these markers as required. (3) Markers identifying the buffer zone must be placed along each buffer zone boundary at all corners and between corners at intervals of no greater than 300 feet. Placement of the landfill grid markers may be made along a buffer zone boundary. (4) Easement and right-of-way markers must be placed along the centerline of an easement and along the boundary of a right-of-way at each corner within the facility and at the intersection of the facility boundary. (5) A landfill grid system must be installed at all solid waste landfill facilities unless written approval from the executive director has been received. The grid system must encompass at least the area expected to be filled within the next three-year period. Although grid markers must be maintained during the active life of the facility, post-closure maintenance of the grid system is recommended, but not required. Markers must be spaced no greater than 100 feet apart measured along perpendicular lines. Where markers cannot be seen from opposite boundaries, intermediate markers must be installed, where feasible. (6) Soil liner or geomembrane liner area markers must be placed so that all areas for which a soil liner evaluation report or geomembrane liner evaluation report has been submitted are readily determinable. Such markers are to provide facility workers immediate knowledge of the extent of constructed disposal areas. These markers must be located so that they are not destroyed during operations until operations extend into the next constructed area. The location of these markers must be tied into the landfill grid system and must be reported on each soil liner evaluation report or geomembrane liner evaluation report submitted. Area markers must not be placed inside constructed areas. (7) Flood protection markers must be installed for any area within a solid waste disposal facility that is within the 100-year floodplain. The area subject to flooding must be clearly marked by means of permanent posts not more than 300 feet apart or closer if necessary to retain visual continuity. (8) A permanent benchmark must be established at the facility in an area of the facility that is readily accessible and will not be used for disposal. This benchmark must be a bronze survey marker set in concrete and must have the benchmark elevation and survey date stamped on it. The benchmark elevation must be surveyed from a known United States Coast and Geodetic Survey benchmark or other reliable benchmark.