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Below the Parachute Creek.Member is the Garden Gulch Member, where the oil shale is characterized as clay rich, roughly 60% clay and 40% carbonate, in contrast to the carbonate -rich Parachute Creek oil shale, which is roughly 60% carbonate and 40% clay. The oil shale Interval within the Parachute Creek and Garden Gulch Members is further subdivided lithologically into seventeen alternating rich (R) and lean (L) oil shale stratigraphic zones. Shell has targeted a zone in the R4 Seal within the Parachute Creek Member for shale oil recovery. The Garden Gulch Member underlies the Parachute Creek Member and is more than 100 feet thick - in the RDD Lease area. Like the overlying Parachute Creek Member, the Garden Gulch Member can be subdivided into rich and lean oil shale zones. The uppermost zone is designated the LI zone, and the contact between the L1 and the overlying R2 is called the `Blue Marker.' The L1 zone is composed of clay -rich lean oil shale and claystone and is about 17 feet thick. The L1 zone is underlain by the R1 zone, which is about 130 feet thick and composed of clay -rich oil shale. Below the R1 zone is the LO zone. It ranges in thickness from 20 to 30 feet and has low -grade oil shale. The LO zone has a distinct influence on geophysical logs (density and resistivity). Early workers referred to this geophysical "kick" as the "Orange Marker." Below the LO zone is the lowermost continuous interval of oil shale in the Green River Formation, the RO zone. It is similar to the R1 zone and is composed of clay -rich oil shale and in one drill core it was found to be about 127 feet thick. ' Below the RO zone additional thin beds of clay -rich oil shale are present, though they are interbedded with considerable quantities of sandstone, siltstone and lacustrine shale. • Hydrogeologlc Setting The primary water - bearing zones that exist in this area are within the Uinta, Green River and • Wasatch Formations. The first encountered groundwater in the RDD Project Site Is approximately . 300 feet below ground surface In the Uinta Formation. The general groundwater flow pattern is from the outer perimeter of the basin, where most recharge occurs, toward the center of the basin where there is discharge to the perennial streams, more active evapotranspiration, and a greater frequency of springs. The Uinta Formation extends downward generally from ground surface and is moderately transmissive due to its relatively low permeability. At the basin scale, the Uinta Is conceptualized as an unconfined aquifer, with stratigraphic heterogeneity that imparts varying degrees of confinement to the deeper strata. "Tongues" of low permeability, kerogen - bearing strata exist in the lower portion of the Uinta and these provide confinement to underlying stratigraphic units. Historically, the Green River Formation has been conceptualized as a sequence of relatively transmissive lean zones (i.e., less kerogen), which are each confined by overlying and underlying rich zones (i.e., more kerogen) having very low permeability. Within the Parachute Creek Member of the Green River, the Dissolution Surface Is a post - depositional subsurface dissolution feature and represents the lowermost penetration of circulating groundwater into the Parachute Creek Member. Above the Dissolution Surface, nahcolite and halite have been largely dissolved away by migrating groundwater, leaving an array of collapse breccias, nodular leach cavities, and otherwise permeable rock wherein pore spaces have derived by the dissolution of nahcolite and halite. Nearly all groundwater in the Green River formation flows through the secondary porosity fractures and dissolution/collapse features as the fine- grained porous matrix is nearly impermeable. The lean zones tend to be more brittle, contain a higher degree of fracturing, and are thus much more permeable than the rich zones. Permit CO32210-00000 S riNAL P!_RM1T Statement of Basis