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To: Mayor and City Council
From:._ City:Staff_
Santa Monica, California August 3, 1981
Subject:.- GRDUNDWATER PRODUCTION, SANTA MONICA WELLS #2, -3; 4
Introduction
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Since the discovery of trace amounts of Trichloroethylene (TCE) in some locally
produced groundwater, investigations into the problem have been conducted. This
report describes the current situation, transmits the final report of Pacific
Soils Engineering Company, (a consulting firm hired to conduct an underground
7CE survey) and makes recommendations regarding use of the affected wells.
Background
Neither of Santa Monica's two available sources of drinking water are. ideal.
Groundwater from local wells is rather hard, and one of the City's best producing
underground aquifers contains traces of TCE. When softened, aerated and blended
at the treatment plant, the water delivered to the consumer is moderately hard
and meets all Federal and State Nealth standards and regulations. Imported
water purchased from the. Metropolitan Water District of Southern California is
also hard, contains. relatively high levels pf Trihalomethanes (THMS), and con ,
tains. asbestos fibers ranging from 1 - 25 million fibers per liter. The content
of THMs is within the. Federal limitations. No limitation on asbestos fibers has
yet been established by health authorities but 0..5 mialion fibers-per liter has
been sugges ed 6y the. U.S. Environmental Protection Agency.
Of the two wells in which TCE has been detected, SM #2 contains less than the
limitiation imposed by California State Health Department, and draws- water from
an aquifer separated 6y a major geological discontinuity from SM #3, which. was
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the major contributor of TCE to the water supply. is /® ~.~/
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QCT 2 7 1981'
Subject: Groundwater Production, Santa Monica
Wells #2,.3,.4
Page 2 3
Returning the affected well (SM ~3) to service and the drilling of a hew well
(SM #4) at a location .1000 feet west of the affected well are treated-in the
conclusions-of the consultant's report bf underground survey. Those conclusions
are:
1. In the area of Santa Monica: Well #3, there are at least two aquifers,
separated vertically. Santa Monica Well #3 withdraws water from the
lower aquifers below 200 feet.
2. TCE contamination is localized in the upper aquifer between 35 to 85
feet.
3. There may be an interconnection between the upper and lower aquifers.
4. Assuming there is an interconnection, TCE content at the well site
proposed for Santa Monica Well No. 4 is expected to 6e negligible; as
pumping of S.h1. #3 would tend to contain the TCE within its area of
influence.
5. Aquifer sampling is recommended for Santa Monica Well No. 4.1
6. water from Santa Mohica Wells: 3 and 4 can be aerated and/or blended
with non-contaminated waters in order to reduce TCE contamination (to
levels below limits established 6y the StateJ.
ANALYSIS OF THE. SITUATION
The TCE content in the City's well water can be treated to a level wi hin Federal
and State parameters using existing facilities and would appear to be less
hazardous than, importing equivalent amounts of replacement imported water contain%ng
1. Aquifer sampling i,s a technique uti ize~i during the drialing of a well i;n which.
each aquifer is sealed off from the rest of the well and the water therein is
tested for .contaminant content. Such a proecedure is not recommended by Staff
because of its unreliability, the fact that additional power is required for
pumping water throughout the life of the well due to the "plugging" effect of
the sealant used, and because of the additional initial cost (approximately
$55,000).
Subject: Groundwater Production„,Santa Monica. Page 3
,;Wells #2, 3, 4
THM and asbestos. As previously reported, the City faces the situation of using
imported ~1WD water containing about 80 ppb of THM or using water from wells #2
and #3 containing-from 5_to 40 ppb of TCE. The Staff believes that the water
containing the. least. amount of organic contaminants should be used.
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1: The TCE contamination is localized at rather shallow depths near the
intersection of Centinela and Olympic Boulevard.
2 The TCE concentrations in delivered water can easily be controlled and
limited to satis.fiy State and Federal guidelines. This was proven prior to
closing the wells last year.
3. The levels of TCE in the wells will be closely monitored on a continuing
basis and should there be a change, the pumps can easily be shut off.
4. TCE concentrations are much less in the groundwater than are the THM
and asbestos concentrations in the imported water. `
5. TCE cannot be easily completely removed from the groundwater, but the
levels can be reduced substantially by aeration and blending.
6. THM levels (.in the imported water) can be reduced by aeration, but since.
the levels are higher to start with, the resulting delivered water can-
not be made as pure with existing treatment facilities as can the City's
groundwater. '
7. Asbestos in minute quantities can not be removed from the water.
Recommendations
Based on all of the facts and information gained over the past 9 months, it'is
recommended that Council authorize:
1. That State and Federal requirements be followed in determining water
quality parameters,
~. That manta t+lonica Wells No. 2 and 3 be returned to service utilizing
Subject: Groundwater Production, Santa Monica Page 4
k!ells. #2, 3, 4
existing treatment techniques including aeration and blending.
3.. That Santa Monica U(eil No. 4 be drilled at the proposed location since
this is 'the best location when both quantity and quality are considered.
Prepared by: Stan Scholl
Ed Lash
John Johnson
Jack Hoagland