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In areas where freezing is a potential problem, <br /> the top of the seal may be below Sround surface but in no <br /> case more than 4 feet (1.2 metres) below ground surface. ANNULAR $FAtif ANKH-Alt 5PAGf <br /> Sealing Conditions. Following are -equire- — - <br /> meats to b, observed in sealing the annular space: SOIL _ =} SOIL <br /> 1. Wells situated in unconsolidated, caving ERt11X1T:S:EAL ;5' f, SANG a GRAVEL <br /> material. An oversized hole, at least 4 inches (100 milli- = TEMPORARY CASING <br /> }, fNirh�ra�n as sea3 <br /> metres) .greater in diameter than the production casing, shall _ ;; ;} p4cadl CLAW <br /> be drilled and a conductor casing installed to the depth of GROUT SEAL s <br /> seal specified in Part A of this section. The space between <br /> the conductor casing and the production casing shall be CASlNr� SAND <br /> filled with sealing material. The conductor may be withdrawn <br /> as the sealing material is placed (see Figure 4A). <br /> CdS�NG CLAY <br /> 2. Wells situated in unconsolidated material <br /> stratified with significant clay layers. If a clay formation <br /> is encountered within 5 feet (1.5 metres) of the bottom of SANDS CLAY <br /> the seal described in Part A of this section, the seal should h11 <br /> be extended 5 feet (1.5 metres) into the clay formation (thus III <br /> the depth of seal could be as much as another 10 feet or III PERFORATIONS SCREEN- <br /> 3 metres). An oversized hole at least 4 inches (100 milli- OR SCREENSANG b GRAVEL <br /> metres) greater in diameter than the production casing, shall III <br /> be drilled and the annular space filled with sealing material III <br /> (see Figure 4B). A. WELL DRILLED IN UNCONSOLIDATED 8. WELL IN UNCONSOLIDATED STRATIFIED <br /> If caving material is present, a conductor casing CAVING MATERIAL FORMATIONS <br /> shall be installed and the annular space sealed as described <br /> in 1, above. <br /> 3. Wells situated in soft consolidated forma- <br /> tions (extensive clays, sandstones etc.). An oversized hole, F�ROU7 <br /> CE <br /> at least 4 inches (100 millimetres] greater in diameter than <br /> the production casing, shall be drilled to the depth of seal WL <br /> specified in Part A of this section and the space between the <br /> production casing and the drilled hole shall be filled with <br /> sealing material (see Figure 4C). CLAY <br /> If a conductor casing is to be installed (to <br /> establish a foundation for the construction of the remainder <br /> of the well) the oversized hole shall be at least 4 inches <br /> (100 millimetres) greater in diameter than the conductor BOREHOLE <br /> SANDSTONE CASING <br /> Defined here as those areas in which the mean length of <br /> freeze-free period as described by the National Weather <br /> Service s le8s than 100 days, i.e., temperatures at or <br /> below 32 (0 C) are likely to occur on any day during a III <br /> period of 265 or more days each year. In general I I1 PERFORATIONS <br /> geographic terms, these areas are the northeastern part of III <br /> the State (parts of Modoc, Lassen, and Siskiyou Counties), <br /> the north Lahontan area (essentially the eastern slopes of C. WELL IN SOFT CONSOLIDATED FORMATIONS <br /> the Sierra Nevada and subsidiary valleys north of Mount <br /> Whitney and Mono Lake) and at Lake Arrowhead in the <br /> San Bernardino Mountains. <br /> 1 Methods of sealing are described in Appendix B. Figure 4. SEALING CONDITIONS FOR UPPER ANNULAR SPACE- <br /> UNCONSOLIDATED AND SOFT,CONSOLIDATED FORMATIONS <br />