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Clay Aquitard - report


Thanks to CEC staff query one results for obtaining significant parts of the 1986 Dames & Moore "Hydrogeologic Assessment Report" of the project site. This 1986 report references data (image below) from earlier Dames & Moore (1946a, 46b, 47, 52) hydrogeologic reports for the project site. A request is for a copy of those complete four original 1946-52 reports.

The goal is to try and solve the oldest mystery in the land. The project site was a famous source of the salt and fresh water. Exactly how the place worked as a natural resource is still an open scientific question. Scrutinizing the oldest Dames & Moore reports could help solve the mystery. An hypothesis to explore is - the source of the salt was oil field brine.

The key to understanding the mystery may be the clay bottom of the original lake. An 1890 state geologist report (transcribed below) describes several aspects of the hydrogeology of the project site including mentioning the bottom of the lake was clay, the salt water not from the open ocean, and the fresh water wells surrounding the salt lake.

The 1986 Dames & Moore describes in more detail this same clay bottom feature as an unnamed aquitard. The following are highlights from the 1986 Dames & Moore assessment report related to the aquitard. The hope is the original 1946, 1947 and 1952 Dames & Moore reports will provide more data about the original hydrogeology of the site.


Dames & Moore
Hydrogeologic Assessment Report
Redondo Generating Station
January 27, 1986
Prepared for Southern California Edison
Download: 1986 Dames & Moore report , (PDF, 10.3 MB), see pages 1-77

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1890, "Lake Salinas, Los Angeles County", by E. B. Preston, Assistant in the Field, California State Mining Bureau, Report X, (p. 281), California Geological Survey Library:

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Lake Salinas

Within the town site of Redondo Beach is a small salt-water lake, about three hundred yards from the ocean, and about five feet above the high-water mark, that does not receive its water supply from the ocean, having an entirely different combination of salts, and has about it and its immediate surrounding features that make it of interest to the geologist and chemist.

The lake is about a half a mile long, and from four to six feet deep. At the south end is a large shallow basin connected by movable gates with the main lake, which is used for evaporating the water by the heat of the sun. The banks are low, gradually sloping up; a sand dune intervenes between the ocean and the lake; the bottom of the lake is a bed of clay. Around this lake on both sides, about thirty wells have been bored to an average depth of twelve feet into the clay that forms the bottom of the lake, and these all yield a good, soft drinking water. Between these sweet water wells next to the ocean, and the ocean itself, near the top of the dune a well has been sunk to a depth of twenty-six feet, which has passed through the clay for a distance of ten feet. The water obtained in this well is claimed as having medicinal qualities; it certainly tastes bad, if that is an criterion of its medicinal value.

The lake water is a much stronger solution of salts than the water from the open ocean, containing a very much greater proportion of chloride of magnesia; but the statement as made by the parties on the spot to the writer, that the water was ten times as saturated as the sea water, is evidently erroneous, as such a solution would pass the point of saturation. How to account for the presence of these different qualities of water in their relative positions, is not plainly to be seen. The salt water could be accounted for in several ways, as there are beds of saliferous shales and sandstones in the neighborhood; also, there are magnesian rocks on the flanks of the mountains surrounding the plain; but the fresh water in the wells surrounding the lake interferes, from the fact that these wells, terminating in the clay, compel the assumption that the water in them is drainage water from the near vicinity. To solve the question satisfactorily would require a closer investigation into the position of the different strata than the limited time at disposal afforded.

South of the town of Redondo Beach about three miles, the bluffs facing the ocean are composed largely of sandstones and shales, with a large bed of diatomaceous earth resting thereon; underlying these and running out to sea are beds of bituminous sandstones, showing natural bitumen in places. These continue in a southwesterly course out to sea as a reef for a distance of two and one half miles, at which point oil is seen coming to the top of the water in considerable quantities.

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