2012-09-06_REVISION - M2008070 (25)

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Design and Operations Plan October 24, 2011 Western Gravel E & P Waste Disposal Facility Page 44 of 51 collected samples will be analyzed for BTEX and TPH for GRO and DRO. In addition, sodium and chloride will be analyzed since these constituents may be indicators of waste impacts. In the event that petroleum constituents are reported in collected samples, confirmation samples may be collected. However, potential laboratory and/or field cross contamination will be evaluated. A trip blank will be used in order to help evaluate potential sample cross contamination. CDPHE must be notified and analytical samples collected within 7 days of discovery. Analytical results must be reported to CDPHE within 7 days of sample analytical results receipt. CDPHE shall be notified in order to determine appropriate corrective actions. 4.8.4 Stormwater Retention Pond In the unlikely event that stormwater run -off from an active landfill cell breaches a diversion control (e.g. perimeter berm, ditch) and enters a stormwater retention pond, CDPHE must be notified and analytical samples collected. Additionally, if petroleum constituents are observed (e.g. sheen on water) or detected in stormwater retention pond samples based upon analytical reports, CDPHE will be contacted in order to determine appropriate corrective actions. At a minimum, analysis will include sodium, chloride, and BTEX. Petroleum constituents reported above the MDLs in collected samples will be considered potential waste impacts. Sodium and chloride results will be used to help assess if a release has occurred. A trip blank will be used in order to help evaluate potential sample cross contamination. CDPHE must be notified and analytical samples collected within 7 days of discovery. Analytical results must be reported to CDPHE within 7 days of sample analytical results receipt. CDPHE shall be notified in order to determine appropriate corrective actions followed by a a status report within 60 days. Stormwater retention pond monitoring documentation shall be maintained in the Operating Record. In the event that petroleum constituents are identified in collected samples, one of several remedial options will be considered including the following. • In the event that samples exhibit residual petroleum constituent concentrations below the groundwater standards, retention pond stormwater will be allowed to evaporate. • If initial sample results exhibit petroleum constituents above the groundwater standards, the pond will be emptied by spraying (misting) atop an active cell and /or transported to an approved disposal facility within 7 days following sample analytical results receipt. Following retention pond emptying and petroleum constituent source(s) identification and mitigation, additional samples may be collected and analyzed in order to determine post mitigation petroleum concentrations in accordance with the mitigation plan developed to specifically address petroleum impacts of the pond. 4.8.5 Methane and VOCs Methane is odorless and colorless and can easily ignite and explode. Methane vents from soil into air through voids and can accumulate to hazardous levels especially in low lying areas. Therefore, special attention should be taken in any low lying and /or semi - confined areas where methane gas could accumulate. By regulation, the lower explosive limit (LEL) of explosive gas may not exceed 100% LEL (5% methane by volume) at the facility boundary. In the event that explosive gas is detected at 100% LEL (5 % methane by volume) at the COD boundary, CDPHE shall immediately be notified. All operations should cease, ignition sources should be extinguished, and all persons immediately leave the area. Monitoring should be conducted periodically in order to ascertain if methane levels have subsided. Because the landfill cells are remotely located, no action may be required. Acceptable methane and VOC levels in working areas should be conservative in order to protect public and personnel health. Methane levels at working areas (i.e., cells, working face) should not exceed 25% of the NWCC, Inc.