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In the greater part of the coastal zone of the Long Beach-Santa Ana area, which includes parts of Los Angeles and Orange Counties, Calif., virtually all water wells yielded water of excellent quality until the late twenties, but at that time certain wells near the coast began to yield salty water and subsequently a number of wells were abandoned. Native salty waters have existed west of the Dominguez Gap and south of the Dominguez Hill, beneath the Long Beach Plain and a narrow zone extending southeast along the coast nearly to Huntington Beach, and locally in the Irvine tract east of the Santa Ana River. However, areas of inferior water that existed as of 1945 within the Dominguez Gap west of Long Beach, in the Santa Ana Gap west of Newport Beach, and on the Huntington Beach Mesa had resulted from progressive depreciation of water quality during the preceding 15 years. Available data include about 5,600 comprehensive chemical analyses and 9,000 partial analyses by several agencies. In downward succession the area contains (1) a body of unconfined water at shallow depth, which is essentially continuous from the oc-san through the five gaps between the coastal hills and mesas, and far irland; (2) a principal body of naturally fresh water which is confined at most places and which occurs chiefly in the lower division of the Recent alluvium, in nearly all deposits of Pleistocene age, and in the upper division of the Pico formation; and (3) a body or bodies of saline connate water. The unconfined water is extensively of inferior quality and locally is grossly contaminated. The principal water body is tapped by wells as much as 1,655 ft deep and is the source of nearly all the very large withdrawal of ground water. Over most of the area its chloride content is from 5 to 40 ppm, hardness from 11 to 300 ppm, and dissolved solids from 160 to 450 ppm. The connate waters underlie all the area; their salinity ranges from 25 to 100 percent of that of ocean water. To depths ranging from 250 to 750 ft, the confined waters are largely of the calcium bicarbonate type, with hardness from 115 to 300 pr»m. Below, in the lower part of the San Pedro formation and in the upper division of the Pico formation the native fresh waters are of the sodium bicarbonate type, with hardness from 11 to 100 ppm, but commonly no more than 50 ppm. Native waters of inferior quality are widespread in the unconfined shallow body and are of diverse chemical character; those of poorest quality occur near the coast and are sodium chloride waters whose greatest known concentration is 160 percent of that of ocean water. Those in the principal 2 GROUND WATERS LONG BEACH-SANTA ANA AREA confined body include waters high in sulfate content and are common at moderate depth along the inland margin of the coastal plain. Sodium chloride and sodium sulfate waters also occur along the coast and loci.lly near the Palos Verdes Hills and the Newport Mesa. Those near the coast contain as much as 18,000 ppm of dissolved solids, but farther inland th^y commonly contain no more than about 6,250 ppm. Other than ocean water, the potential saline contaminants are the connate waters in the rocks of Tertiary age, oil-field brines and oil-refinery wastes, and fluid industrial wastes. The connate waters are sodium cl loride brines ranging about from 10,000 to 39,000 ppm of dissolved solids. They have been tapped by several thousand oil wells but there is no evidence that they have moved upward into any fresh-water body. As oil-field waste, the connate brines formerly were discharged rather promiscuously onto the land surface locally in the Dominguez field and generally in the Long Beach and Huntington Beach fields. As of 1945 they are still so discharged to some extent in the Huntington Beach field, but with this exception they now are largely piped to the ocean or to central disposal works. As of 1945, effluent from such works is discharged into the San Gabriel River within a mile of the ocean, into the Los Angeles River about 4 miles inland, and into the Dominguez Channel at several places throughout its reach. Owing to former promiscuous discharge onto the land surface, oil-field brines have accumulated locally beneath the flank of the Dominguez Hill, probably rather extensively beneath the Signal Hill uplift, and rather widely beneath the Huntington Beach Mesa. Tho^e accumulations definitely are the source of contaminating brines which have invaded the fresh water at certain places, and they will remain as potential sources of contamination almost indefinitely. In the western part of the area, brinedisposal works which serve the Long Beach oil field coincide with a focal area of intense contamination in a water body that natively was of excellent quality. Industrial wastes of diverse chemical character have been discharged into the Los Angeles River at several places, but so far as is known these have been less concentrated and less voluminous than the oil-field brines. As of 1945, oil-refinery wastes, commonly similar in chemical character to the oil-field brines, are discharged in part into the Dominguez Channel and thence to the ocean. Many of the contaminated waters have been profoundly modified in chemical character after admixture of the contaminant, especially by baseexchange substitution of calcium and magnesium for sodium Thus, the slightly contaminated or moderately contaminated waters commonly contain calcium and chloride as their dominant constituents; from t^eir ordinary constituents it is usually impossible to discriminate between contamination by ocean water and that by oil-field brine or connate water. Determinations of iodide or borate are reported in but few of the available chemical analyses, and only to that extent aid in discriminating the source of contamination. It is suggested that these two minor constituents, together with barium, be determined in future analyses of contaminated waters. Areas in which the fresh ground water has been contaminated are described in detail the Santa Ana Gap, Huntington Beach Mesa, in and near the Alamitos Gap, and the northeast part of the Newport Mesa, all in Orange County; also, the Dominguez Gap, a part of the Torrance Plain, and the southwest flank of Signal Hill, all in Los Angeles County.

Native and contaminated ground waters in the Long Beach-Santa Ana area, California