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1. Well wholly situated in unconsolidated material in an unconfined ground water zone (Figure 9A). If the ground water supplies are within 50 feet (15 metres) of the surface, the upper 20 feet (6 metres) shall be sealed with impervious material and the remainder of the well shall be filled with clay, sand, or other suitable inorganic material (see item D, this section). - 2. Well penetrating several aquifers or q formations. In all cases the upper 20 feet (6 metres) of the 4 : r y EXISTING GROOJT SEAL . .'.;- well shall be sealed with impervious material. 2d M""` r y gp Ew10t€ ' 20'min. In areas where the interchange of water between F. —SEALIIIS YpiER��1L `:;+� �. ' ► =?- aquifers will result in a significantV deterioration of the ° Q quality of water in one or more aquifers, or will result in a loss of artesian pressure, the well shall be filled and sealed so .as to prevent such interchange. Sand or other CX$ING suitable inorganic material may be placed opposite the producing aquifers and other formations where impervious FILLER sealing material is not required. To prevent the verticalRSk�LIHG movement of water from the producing formation, impervious material must be placed opposite confining formations above iIITEJiIIkL and below the producing formations for a distance of 10 feet (3 metres) or more. The formation producing the deleterious � RAVEL py water shall be sealed by placing impervious material opposite the formation, and opposite the confining formations :* for a sufficient vertical distance (but no less than 10 feet ' or 3 metres) in both directions, or in the case of "bottom" A" SHALLOW WELL Ill UNCONSOLIDATED waters, in the upward direction. (See Figure 9B.) TERJ ! In locations where interchange is in no way detri i:'. _:'o- I': mental, suitable inorganic material may be placed opposite the formations penetrated. When the boundaries of the ExiSiING n I-' AQUIFER T4 various formations are unknown, alternate layers of ACKFILt impervious and pervious material shall be placed in the well. I r}r RFNE T101�8 #'.�.: � I. SE,S�Ep-pFFI 5, Max Determining the significance of interchange of waters 4 Mfl'�tIN whose qualities vary and of the loss of artesian pressures, Ap ' .` .:*'. 'requires extensive knowledge of the ground water basin in . '. FALLER T question. The Department of Water Resources has over the '�"' ;.' r:: years, and frequently in cooperation with agencies such as a GR SEALING the U. S. Geological Survey, undertaken a number of r ' SEALING MATERIAL MATERIAL water studies and amassed considerable information and ` " 1 CASlFiG Ex15TIMG � data about the subject. Although much is known about the :: .' . ERFORATION$ ! M State's ground water supplies, detailed studies suffi- ciently accurate to define interchange problems have been EXrSTIIfG GROUT I I made only in certain areas. In still other areas, there _ ; ' is only partial definition of the problem. Examples of '• ExL I r areas where definition has been made are the coastal plain UPPER J$EALfN� FEATURES g DEEP WELL WITH AQUIFER SE r of Los Angeles County and the eastern part of the Santa URBAN AREA WELL Clara Valley in Alameda County. An excellent example of a "bottom" water is the saline connate water underlying the Central Valley at varying depths. Figure 9. PROPERLY DESTROYED WELLS