First Advisor

A.G. Johnson

Term of Graduation

Fall 1986

Date of Publication

12-8-1986

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Geology

Department

Geology

Language

English

Subjects

Groundwater flow -- Washington (State) -- Hanford, Seepage -- Washington (State) -- Hanford, Aquifers -- Washington (State) -- Hanford

DOI

10.15760/etd.5574

Physical Description

1 online resource (2, ix, 120 pages)

Abstract

Intercommunication has been identified between the unconfined and uppermost confined aquifer systems underlying a portion of the U.S. Department of Energy's Hanford Site. Erosional thinning and fracturing of the basalt confining layer within the study area allows physical contact between the two aquifers, but the vertical hydraulic gradient (a required driving force) is small. To better conceptualize the distribution and volume of the leakage occurring between the aquifer systems, this study investigates the confined Rattlesnake Ridge Aquifer flow system, which appears to be more sensitive to the vertical leakage than the overlying unconfined aquifer.

The flow system of the Rattlesnake Ridge Aquifer is poorly understood. The flow direction of this aquifer in the study area is difficult to define because most of the wells used to obtain data are concentrated in one area. The complexity of the flow in the study area makes extrapolation from these data points difficult.

Several scenarios are formulated to describe plausible hydrogeologic settings that could produce the confined flow pattern observed. These scenarios include recharge to the aquifer derived from leakage from the overlying unconfined aquifer and the underlying deep confined aquifer system. Leakage amounts were computed from estimations of vertical head differentials between the unconfined and confined aquifer and from hydraulic conductivity data of the basalt confining layer. The hydraulic conductivity values of the basalt are controlled by vertical fractures.

Results of modeling show that the observed flow configuration can be simulated as the westward flanks of a ground-water mound produced from leakage between the unconfined and confined aquifers. This implies that leakage through vertical fractures and erosional windows in the basalt can play an important role in the interpretation of the Rattlesnake Ridge Aquifer's flow system and in our understanding of aquifer intercommunication in the study area.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Comments

If you are the rightful copyright holder of this dissertation or thesis and wish to have it removed from the Open Access Collection, please submit a request to pdxscholar@pdx.edu and include clear identification of the work, preferably with URL.

Persistent Identifier

https://archives.pdx.edu/ds/psu/20718

Download

Share

COinS