Doing Business with OSE/ISC
ADMINISTRATIVE STANDARDS
To achieve the above objectives, quantitative standards as deemed reasonable by the state engineer must be selected which define allowable impacts from existing and proposed wells within the Alamogordo-Tularosa administrative area. These standards, and their basis, where applicable, are as follows:
A. The average annual water level decline rate of 2.50 feet per year or less due to the exercise of existing water rights will be considered acceptable. This level of mining has been selected for other mined basins in the state and was deemed reasonable for the Alamogordo-Tularosa administrative area. In areas where the freshwater thickness is less than 400 feet, acceptable average annual decline rates will be controlled by paragraph C below to extend the life of the freshwater zone.
B. Total dissolved solids (TDS) in groundwater is adopted as a measure of groundwater quality. Freshwater is defined as containing less than 1,000 mg/l TDS (Orr and Myers, 1986). Degradation of water quality from less than 1,000 mg/l TDS to 1,000 mg/l TDS or greater will be considered unacceptable. Two different methods will be used to provide protection to the freshwater zone. These are 1) a volumetric approach to allow a certain portion of the aquifer to be de-watered and 2) the use of a solute transport model to predict which areas will degrade to TDS concentrations of 1,000 mg/l or greater. Based on studies for the Hueco Basin (Papadopulos, 1987), it is assumed that water quality in the freshwater zone will remain fresh if drawdowns do not exceed one- half of the freshwater thickness estimated for the aquifer of the 1980s. The SEO has also developed a two-dimensional finite difference flow and solute transport model to simulate the effects of pumping on water levels and TDS concentration (Morrison, 1989). Future pumping by existing wells were simulated with a low, medium and high scenario. Unless the results of the solute transport simulations indicate that the water quality conditions will degrade to TDS levels of 1,000 mg/l or greater, it will be assumed that recoverable freshwater is one-half of the initial freshwater thickness estimated for the aquifer of the 1980s (Figure 2).
C. At least one-half of the recoverable freshwater will be reserved for use beyond the 40-year planning period for areas in which it is anticipated to remain fresh (Figure 2).
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