2010-04-16_PERMIT FILE - C1996083A (11)

Home Browse Search

2.04.7 Hydrology Description • Electrical conductance and total dissolved solids values from Mesaverde sources are typically a factor of ten higher than similar parameters measured from colluvial, near surface water sources (2,000 to 8,000 umhos v.s.200-800 umhos, respectively). The notable difference in water quality clearly separates the groundwater systems and suggests the longer residence time (and lower transmissivity) of the water within the bedrock Mesaverde (refer to Groundwater Monitoring results). ~" Potential recharge to the Mesaverde Formation occurs within the major stream drainages, while flowing, (Brooks,1983). Additional recharge of much smaller magnitude could occur at the outcrop, yet the near vertical exposures and sporadic precipitation precludes any large scale infiltration. Upper Perched Water Zone and Rollins Sandstone The interpretation of the groundwater presence in the Mesaverde Formation is based on the observation of water presence during the exploration drilling, water level measurement during the geophysical well logging, and water level measurements in the monitoring wells. The results of this interpretation are shown on Maps 10 and 11. These maps show the perched water bearing areas within the water bearing zones and also areas where the data points show these zones to be dry. This interpretation indicates that the recharge area into the perched water zones is near the outcrop of the sandstone subcropping underneath the local drainages. The general groundwaterflow in the Mesaverde • perched water zones is toward north, following the basin structure. The water probably originates in the colluvium or colluvial water recharges of the shallower Mesaverde Formation lithologies. The alternating lenticular channel sandstone and enclosing overbank claystone lithologies within the upper Mesaverde Formation has the potential to create perched water table conditions within the permit area. These conditions, which are a function of the deltaic fluvial depositional environment, are characterized by confined, saturated horizons of localized lateral and vertical extent within low porosity, unsaturated intervals. These perched, confined horizons may exhibit artisan conditions; however, flowing conditions were not observed within the permit area. The erratic location of these perched groundwater occurrences, low transmissivity and permeability, and the absence of development and exploitation diminishes the possibility of being used as a groundwater resource in the foreseeable future. colluvial Near Surface Storage Within the permit boundary area, there are several colluvial deposits. These deposits are contained in the mixtures of clay, sand, and silt with some large rock fragments. These strata were formed by slow downslope movements of near surface materials, locally reworked by fluvial processes. The lateral extent of • these strata is shown on Surficial Geology Map 05, where the quaternary deposits have a symbol "Qas" at the head of Freeman, Sheep Corral and Dove PR-10 A PP~eovE9 2.04 - 29 - 10/08 7f~2.y/fig