2012-09-06_REVISION - M2008070 (25)

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Design and Operations Plan Western Gravel E & P Waste Disposal Facility 6.0 POST - CLOSURE MAINTENANCE October 24, 2011 Page 48 of 51 During the post - closure period and following establishment of vegetation, the property can convert to the original zoned use for agricultural purposes (e.g. grazing, open range) provided such uses do not damage closed landfill components (e.g. final cover, liner, containment systems). Post - Closure care consisting of inspections conducted under the direct supervision of a Professional Engineer registered in Colorado, will be conducted for a period of up to 30 years or a shorter time period acceptable to CDPHE. It should be noted that CDPHE has the authority to impose a longer post - closure monitoring period if deemed necessary. Discrete landfill units (e.g. cells) that can be monitored and maintained separately will begin and end the post- closure period independent of entire facility closure. In the event that a reduced period of post - closure care is demonstrated to be sufficient to protect public health and the environment, the owner may request a reduced post- closure maintenance period. Verification of all monitoring and inspection results will be through an independent Environmental Professional and documentation of all results will be placed in the Operating Record and forwarded to CDPHE in an annual report. Alterations to the monitoring schedule may be recommended to CDPHE for approval, based upon previous results. Various different inspections and monitoring will be conducted concurrent, as practicable. Appropriate maintenance and repairs will be conducted by the owner based upon inspection results. Documentation of semi - annual and annual inspections will be placed into the facility Operating Record. Observed additional problems including but not limited to vectors and other nuisances, final cover erosion, reclamation damage, unpredicted subsidence and /or water ponding, and illegal dumping will be documented in a report prepared subsequent to each inspection. One inspection per annum will be conducted by a qualified engineer as the annual inspection. Inspections of all facilities, engineered structures, and general property conditions will be conducted. Inspections shall include but not be limited to the following. • Final re- graded areas (final cover) will be inspected for structural integrity, effectiveness of the final cover, signs of erosion and /or animal damage, and verified as operating properly as designed. Required repairs will be conducted as required in order to correct settlement, subsidence, erosion, other events, and preventing run -on and run -off from eroding or damaging the final cover. • Illegal dumping, site access controls, signage, nuisance conditions. • Remaining surface water controls including stormwater retention ponds, surface run -on and run -off controls. • Wet/dry wells, LDS, and LCRS shall be inspected semi - annually during the post - closure period. Monitoring will be conducted in accordance with the schedule summarized below and include but not be limited to the following facility components. An alternative monitoring schedule may be proposed in the future based upon historic monitoring results. • Wet/dry wells will be monitored for the presence of liquid on a quarterly basis. In the event that liquid is discovered, procedures previously discussed will be implemented including terrace face seep monitoring. • Leachate collection system will be monitored for the presence of leachate on a quarterly or more frequent basis, based upon leachate generation rates. In the event that leachate is present, management and disposal procedures previously discussed will be implemented. Since leachate NWCC, Inc.