CWEA Wastewater Professional :: April 2014 March 2014 Volume 2 | Page 15

Feature Article | CWEA’s First “Plant of the Year” Award, 1929

Members of California Sewage Works Association on Sprinkling Filter at University of California Farm, Davis,
April 21, 1930
The Award Winning U.C. Davis Sewage Treatment Plant
What type of treatment plant was the 1929 “Plant
of the Year?”The 1930 CSWA film clip is just over a
minute long and shows three of the main features
of the U.C. Davis sewage treatment plant – a pump
house, an Imhoff tank and sprinkling filters (a form
of trickling filter). The film is very short but it did
provide just enough information to help the CWEA
History Committee track down more detailed information about the plant. Knowing that the U.C. Davis
plant was the subject of a conference tour, the 1930
conference minutes and papers were the first documents to be reviewed by the History Committee.
The 1930 spring conference minutes provide the
details of the tour of the U.C. Davis Sewage Treatment Plant and a photograph (below) of the CSWA
tour attendees posing on the plant’s sprinkling filter
structure with the Imhoff tank in the background.
The photograph matches the scene in the film and
confirms that the film was taken on April 21, 1930.
Regarding the U.C. Davis Sewage Treatment Plant’s
design and process, the minutes and conference papers also gave us the following information:
The U.C. Davis Sewage Treatment Plant was
constructed in 1926, along with a sewage collection
system, at a cost of $50,000 (approximately $660,000
in current dollars). The plant was designed by H.B.
Foster, U.C. Engineer, and consisted of two pumping
and screening plants, an Imhoff tank, sprinkling filter,
two secondary clarifiers, a sludge bed and irrigation
checks to utilize the effluent for summer irrigation.
The treatment system was designed for handling

the sewage of a population of 700 persons plus a
large volume of manure and milk/creamery wastes
from the U.C. Davis farm. The average flow to the
plant was 0.175 MGD, but it was noted that the plant
was occasionally subject to peak flows with a population equivalent of 20,000 people during club gatherings and special campus events.
At the time of construction in 1926 the U.C. Davis
plant was located 2.5 miles from the campus center
and the travel time for the sewage from campus to
the plant was approximately 2 hours and 20 minutes.
The combination of domestic sewage, dairy/creamery
wastes and barn wastes (with the dairy/creamery
wastes representing approximately one-quarter of the
total flow to the plant) created a very strong sewage
thanks to the high BOD of the milk wastes, so odor
control was a priority for pumping stations and treatment plant O&M program.
1930 CSWA Award Publicity & Students Program
The League of California Municipalities (the predecessor of today’s League of California Cities) and
the CSWA held joint annual conferences during the
1930’s. The League also published Pacific Municipalities, a monthly magazine that provided a “review of
municipal problems and civic improvements” as well
as covering activities for both the California and Oregon Leagues of Municipalities.
The U.C. Davis sewage treatment plant was
given a “starring role” by being featured on the April
1930 cover of Pacific Municipalities along with an
article on the April CSWA conference. Future CSWA
president John Jacobson is also highlighted in the
Wastewater Professional April 2014

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