--> Abstract: Impacts Assessment of Coastal Well Field Operations, City of Morro Bay, California, by T. S. Cleath and M. D. Powers; #90992 (1993).

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CLEATH, TIMOTHY S., and MICHAEL D. POWERS, Cleath & Associates, San Luis Obispo, CA

ABSTRACT: Impacts Assessment of Coastal Well Field Operations, City of Morro Bay, California

The community of Morro Bay has depended upon ground water from two alluvial valleys for more than 30 yr as their sole source of water supply. Seawater intrusion in these valleys during the past few years has made it increasingly evident that some source of emergency water supply should be obtained which would be noninterruptible. Seawater desalination was selected as that source.

Coastal wells were chosen instead of an offshore intake pipe to provide feed water for the treatment plant because of potential problems with turbidity and organisms in unfiltered seawater and because of the lower cost and lesser regulatory requirements of the coastal well field facilities. The issue addressed during our study of the new well field was the impact that this new groundwater extraction facility would have on upstream users in terms of groundwater levels and water quality.

The groundwater basin was characterized in terms of physical and dynamic parameters prior to using the U.S. Geological Survey ModFlow groundwater flow model to simulate operating scenarios. The extent of individual aquifers in the basin and the area of subsea outcrop were found to be different from was previously thought.

The flow simulation determined the quantities of fresh groundwater and seawater which would be extracted by the new facilities and the resulting basin groundwater levels. The option of using the existing potable city wells in the basin for brackish water production was found to result in lowered water levels and seawater intrusion.

AAPG Search and Discovery Article #90992©1993 AAPG Pacific Section Meeting, Long Beach, California, May 5-7, 1993.