2009-06-11 - New rock samples could reveal details about water supply, drought risk
Chico, California, June 09, 2009 -- Core samples taken from drilling groundwater monitoring wells in the Skyway Homes Subdivision area are providing important information about the geology in the Chico vicinity.
What is known about the geological history of the area was compiled through the review of existing literature, examination of material brought to the surface as a result of the rotary drilling of wells and other borings that cut into the soil and rock, and the examination of rock and sedimentary formations, such as the hilltop cliff located in Upper Bidwell Park.
With sonic drilling technology, a continuous core is recovered intact from the bore hole as it was formed through the millennia, layer upon layer. The core samples recovered by ABB go down 250 feet, although sonic drilling can go as deep as 500 feet.
Sarah L. Raker, a geologist and MACTEC Consulting’s on-site project manager for ABB, said, “These core samples might help geologists determine the relationship between rock formations and local aquifer systems to identify potential drought-related implications.”
ABB, realizing the potential research value of these cores, made them available to California State University – Chico, California Department of Water Resources, Department of Toxic Substances Control and California Regional Water Quality Control Board.
Comparing the cores removed from the monitoring wells with the hilltop cliff in Upper Bidwell Park has helped geologists identify a distinct rock unit that is present at the well drilling locations, the Tuscan Formation (3.3 to 2 million years ago). The Tuscan Formation is mainly derived from the Mt. Yana volcanic center.
According to geologist Todd Greene, an assistant professor at California State University – Chico, “The Tuscan Formation, sheets of volcanic fragmented rocks, dive under the town of Chico and serve as the city’s main groundwater supply.” He said if the Tuscan Formation can be better understood, then more realistic groundwater models will be able to map the flow paths and storage volumes of Butte County’s water supply, for which little is known.
New information from the cores may be revealed after the samples are examined. Greene plans to use the core samples for a student project to determine the distribution of the rock types, how they are related and how far they extend. The cores may also add to the understanding of the structure and quality of these rocks in holding water and the amount of water that travels through them. “This is the first step,” Greene added. “There are many more to go before we are able to come to any conclusions.”
Echoing Greene’s comments on the scientific significance of extracting continuous cores, Department of Toxic Substances Control veteran geologist and project manager for the Skyway Subdivision plume Don Mandel said, “I could not believe the complete cores this technology delivered. The correlation of the cores to bedrock outcrops that can be observed directly at the Earth’s surface is incredible.”
ABB’s monitoring well drilling activities are part of the groundwater investigation to determine the extent of the Skyway Subdivision plume of groundwater containing trichloroethylene. The company recently hooked up 68 residential homes with wells containing chlorinated solvents to municipal water as a permanent solution to the problem.
ABB (www.abb.com) is a leader in power and automation technologies that enable utility and industry customers to improve performance while lowering environmental impact. The ABB Group of companies operates in around 100 countries and employs about 120,000 people. Headquartered in Zurich, Switzerland, ABB had revenues of $34 billion in 2008.
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For more information, contact:
Ron Kurtz
Director of Community and Media Relations
ABB Inc.
501 Merrit 7
Norwalk, CT 06468
Don Mandel, P.G.
Project Manager, Skyway Subdivision Plume
Dept. of Toxic Substances Control
8800 Cal Center Drive
Sacramento, CA 95826
(916) 255-3667
Todd J. Greene, PhD
Assistant Professor
Dept. of Geological and Environmental Sciences
California State University – Chico
400 West 1
st Street, PHSC 111
Chico, CA 95929-0205
(530) 898-5546
Sarah L. Raker, P.G., CHG
Principal Geologist
MACTEC Engineering and Consulting, Inc.
5341 Old Redwood Highway, Suite 300
Petaluma, CA 94954
(707) 793-3841