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Open-File Report 2014–1087

Prepared in cooperation with the Water Replenishment District of Southern California

Characterization of Potential Transport Pathways and Implications for Groundwater Management Near an Anticline in the Central Basin Area, Los Angeles County, California

By Daniel J. Ponti, Brian J. Wagner, Michael Land, and Matthew K. Landon

Thumbnail of and link to report PDF (7 MB)Abstract

The Central Groundwater Basin (Central Basin) of southern Los Angeles County includes ~280 mi2 of the Los Angeles Coastal Plain and serves as the primary source of water for more than two million residents. In the Santa Fe Springs–Whittier–Norwalk area, located in the northeastern part of the basin, several sources of volatile organic compounds have been identified. The volatile organic compunds are thought to have contributed to a large, commingled contaminant plume in groundwater that extends south-southwest downgradient from the Omega Chemical Corporation Superfund Site across folded geologic strata, known as the Santa Fe Springs Anticline. A multifaceted study—that incorporated a three-dimensional sequence-stratigraphic geologic model, two-dimensional groundwater particle-tracking simulations, and new groundwater chemistry data—was conducted to gain insight into the geologic and hydrologic controls on contaminant migration in the study area and to assess the potential for this shallow groundwater contamination to migrate into producing aquifer zones. Conceptual flow models were developed along a flow-parallel cross section based on the modeled stratigraphic architecture, observed geochemistry, and numerical model simulations that generally agree with observed water levels and contaminant distributions. These models predict that contaminants introduced into groundwater at shallow depths near the Omega Chemical Corporation Superfund Site and along the study cross section will likely migrate downgradient to depths intercepted by public supply wells. These conclusions, however, are subject to limitations and simplifications inherent in the modeling approaches used, as well as a significant scarcity of available geologic and hydrogeochemical information at depth and in the downgradient parts of the study area.

First posted May 5, 2014

For additional information, contact:
Director, California Water Science Center
U.S. Geological Survey
6000 J Street, Placer Hall
Sacramento, California 95819
http://ca.water.usgs.gov

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Suggested citation:

Ponti, D.J., Wagner, B.J., Land, M., and Landon, M.K., 2014, Characterization of potential transport pathways and implications for groundwater management near an anticline in the Central Basin area, Los Angeles County, California: U.S. Geological Survey Open-File Report 2014-1087, 75 p. and appendix, http://dx.doi.org/10.3133/ofr20141087.

ISSN 2331-1258 (online)



Contents

Abstract

Introduction

Geologic and Hydrologic Framework

Groundwater Sampling and Geochemistry

Groundwater-Flow and Particle-Tracking Model

Discussion and Conclusions

References Cited


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