Locating, Investigation, and Defining the Pawnee Aquifer, Northeastern Colorado
Presented on Tuesday, May 6, 2014
Theresa Jehn-Dellaport, P.G., Quantum Water & Environment, Lakewood, CO
The Cheyenne Basin in northeastern Colorado has been explored and exploited for oil and gas reserves. Due to the numerous oil and gas wells that have been drilled in this basin, there is a proliferation of geophysical logs that has provided a wealth of information that enabled locating and defining an unexplored aquifer. The aquifer is defined through geophysical logs, test holes, production wells, cores, and outcrop data. The aquifer is a fine sandstone, siltstone and is continuous throughout northeastern Colorado.
The Pawnee aquifer is overlain by the Laramie-Fox Hills aquifer which is overlain in some locations by Quaternary eolian and alluvial deposits. The Pawnee aquifer is located in the upper portion of the Pierre Shale and ranges in saturated thickness from 600 to 800 feet. The Pierre Shale was deposited in the deeper waters of the Cretaceous Interior Seaway. The upper units are comprised mainly of shale with the upper several hundred feet containing persistent layers of saturated siltstone and fine grain sandstone, known as the Pawnee aquifer.
MODFLOW modeling of the aquifer indicates that the withdrawal of groundwater is nontributary to the stream system, based on 100 years of continuous withdrawal. A digital model of the base of the South Platte River alluvium was acquired and used for the model.
The Pawnee aquifer is an unexplored deep aquifer that can provide water to local municipalities especially in time of drought.
Theresa Jehn-Dellaport, P.G.
Quantum Water & Environment, Lakewood, CO
Theresa Jehn-Dellaport brings more than 26 years of experience in groundwater and surface water evaluations, feasibility studies, large municipal water well design, aquifer storage and recovery, surface and groundwater rights studies, plans for augmentation, substitute supply plans, surface water hydrology studies, aquifer pump test analysis, monitoring well and water well design, construction and testing, and specification preparation for large municipal and domestic water supply wells. She also has extensive experience in directing large multidisciplinary technical staff, subcontractors, and consultants.
