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Logan Wash Mine TR No. 8 2.0 Background Information The Logan Wash Mine is an inactive oil shale mine that operated between 1972 and approximately 1991. The mine began the first of several significant reclamation phases in 2004 when the remaining open portals were sealed and the mine dumps and upper bench areas were reseeded. Two types of mine water continue to discharge from the mine through constructed piping systems. The first type is referred to as retort water which is groundwater that has come in contact with spent (previously retorted) oil shale areas (retorts). Retort water drains by gravity through constructed piping and is conveyed to a non - discharging evaporation pond located several miles west of the mine site. The second type of water discharging from the mine is referred to as non - retort water, or simply mine water, which is groundwater that infiltrates the general open mine workings. At the main Logan Wash Mine, mine water accumulates in a French drain located in the lower (L -1) portal area and is conveyed in a 2 -inch HDPE pipe from the mine to a discharge point on the surface in Dry Gulch, about 900 feet to the west of the sealed portal. The mine water that drains from the I. -1 portal is referred to as Outfall 001 and is designated the 001 discharge under National Pollutant Discharge Elimination Systems (NPDES) or CDPS Permit No. 000048816. The Outfall 002 mine water is conveyed in a buried 4 -inch diameter polyvinylchloride (PVC) pipe extending from the Research Mine portal to the Lower Bench Vault and then several hundred feet further to its discharge point near the top of a riprapped storm water channel. Mine water originating in the Research Mine is designated the 002 discharge under the CDPS permit. Mine water discharge from the Research Mine can be controlled by valves in a vault near the portal. However, mine water occurrence is intermittent in the Research Mine and if present, generally occurs in the spring during snowmelt. No discharge has occurred from Outfall 002 since the Research Mine portal was sealed in 2004. 3.0 Project Rationale The termination of the CDPS permit at Logan Wash Mine is of interest to OOSI because it will reduce the number of regulatory agencies currently involved with the mine while still maintaining adequate surface water and groundwater regulatory protection requirements through DRMS. All surface water and groundwater standards, as promulgated by CDPHE - WQCC, will remain applicable at the mine site after the proposed infiltration trench is constructed and operating. The proposed activity is consistent with the intent of the MOA between CDPHE and DRMS. The mine water discharging from the mine has a chemistry that reflects its groundwater origin. Under the current CDPS permit, effluent limits have been established based on receiving surface waters in the region, not groundwater standards. Mine water discharging from the L -1 portal at Outfall 001 infiltrates quickly into the colluvium materials that make up the shallow surface of Dry Gulch; water may flow only 2 or 3 feet beyond the end of the discharge pipe before it completely infiltrates into the ground surface, ultimately recharging the unconfined aquifer downgradient of the mine. By relocating the discharge point to a location on top of the Lower Western Water & Land, Inc. 2