clear solution – Sacramento State civil
engineers help preserve a national treasure
Tahoe’s Emerald Bay and Fannette Island.
Will Hart Photo courtesy of Lake Tahoe Visitors Authority
tourist draw Lake Tahoe is considered one of the clearest large lakes in the
world, but it has been steadily losing clarity over the last 40 years. With
the help of Sacramento State civil engineering professor John Johnston and Office
of Water Programs research engineer Dipen Patel, the California Department of
Transportation (Caltrans) has been developing award-winning technology to reverse
Since 2001, Johnston, Patel
and others have been helping Caltrans carry out a program to identify, test
and evaluate potential treatment methods to clean up storm water runoff.
“Runoff from highways,
local roads, parking lots and even residences contains phosphorus—which
causes algae growth—and small particles—which cloud the lake water,”
says Johnston. “Caltrans owns and maintains 68 miles of roadway in the
Tahoe Basin, and even though it is a minor part of the whole problem, Caltrans
has invested heavily in this program.”
Office of Water Programs designs experiments, sets the research questions and
interprets the results of the storm water and algae treatment studies for Caltrans.
“The effluent, or
pollution, limits for storm water runoff into Lake Tahoe are extremely stringent—more
so than for most city wastewater treatment plants,” says Johnston. “In
the beginning, we didn’t have the technology to meet those requirements,
especially technology that could operate on the side of the road without power
With oversight from the
Office of Water Programs staff, consulting engineering teams collected storm
water samples at various locations around the lake and tested a variety of treatment
systems to clean the water, which involved small-scale tests with combinations
of filters and chemicals. “This was basically adaptations of drinking
water treatment technologies,” says Patel.
Based on those results,
Caltrans constructed and tested six full-scale pilot filters using novel filtering
media. This approach to storm water treatment is unique in the nation.
“Through this research,
we’ve been able to develop efficient storm water treatment techniques
that others can adopt,” Patel says.
Johnston, “we’re contributing to the preservation of a unique natural
Last week, the Sacramento
Section of the American Society of Civil Engineers recognized their efforts
in giving Caltrans the Outstanding Engineering Project of the Year Award (water
ASCE Award entries are judged
by a volunteer group of civil engineers, as well as journalists covering civil
engineering issues. The awards recognize contributions to the well-being of
people and communities, resourcefulness in planning and solving design challenges,
pioneering in use of materials and methods, and innovations in construction
and impact on the physical environment.
California State University, Sacramento Public
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