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1988 `4TNERAL LAND CLASSIFICATION, STOr' T0 '-t.ODI 15
<br /> Mendota Canal.Table 9 shows the total quantity of reserves and Eighty-three percent of the available resources in the P-C region
<br /> resources used in calculating the life expectancy of PCC-grade are contained in this one deposit.
<br /> aggregate in the Stockton-Lodi P-C Region.
<br /> l Sector A has three active sand and gravel operations,Teichert
<br /> One MRZ-2 area immediately downstream of the Camanche Aggregates,Lone Star Industries, and Granite Construction Co.
<br /> Dam on the Moke]umne River,has not been included as a re- The aggregate in this deposit extends to a depth of at least 200
<br /> source sector(Plate 3). A major portion of this zone encompas- feet(cross-sections A-A', B-B', and C-C',Plate 24),but mining
<br /> ses Van Assen Park. Dedicated parklands are not sectorized; is usually permitted only to the water table which occurs approx-
<br /> therefore this material is considered unavailable for mining(see imately 95 to 120 feet below the surface.Mining is feasible 40 to
<br /> Resources within Parks). 50 feet below the water table without the use of a dredge.Only
<br /> Lone Star Industries is currently permitted to mine 40 to 50 feet
<br /> Resource sectors A-1,A-2,A-3, A-4 (collectively called Sec- below the water table. Both Teichert Aggregates and Granite
<br /> for A),B and C are located on the eastern flanks of the Diablo Construction Co. are restricted by permit to mine only to the
<br /> Range just south of Tracy. Streams flowing northeastward have depth of the water table. Another limiting factor is the existence
<br /> developed a succession of lobate-shaped alluvial fans at the base of a 20 to 30 foot-thick clay layer between 70 to 120 feet(aver-
<br /> of the mountains.These fans are composed of San Luis Ranch age 90 to 100)below the surface. Since all three operators ex-
<br /> alluvium and Los Banos alluvium(Bartow, et. al., 1985)which tract from the same deposit, the high clay content(15 to 50
<br /> contain reworked sediments derived from older alluvial fan de- percent)is a factor that impacts all competitors equally,result-
<br /> posits.These units are approximately the same age as the late ing in aggregate prices that are competitive.
<br /> Pleistocene Modesto and Riverbank Formations located across
<br /> the valley on the eastern flank of the Sierra Nevada Mountains Many portions of Sector A are now unavailable for mining due
<br /> (Plate 23).A thin veneer of Holocene Patterson alluvium over- to rapid urbanization of the City of Tracy. The land zoned MRZ-2
<br /> lies these fans (Figure 10 and Plate 22). Resource Sectors A, B which contains Sector A encompasses 8.0 square miles. Only
<br /> and C are identified,respectively, as the Corral Hollow Creek, half of the MRZ-2 area(4.5 square miles)contains available
<br /> Lone Tree Creek and Hospital Creek alluvial fans on Resource PCC-grade aggregate, of which 1.3 square miles are currently
<br /> Sector Maps(Plates 19, 20 and 21)and Mineral Land Classifi- permitted for mining.Therefore, approximately 3.2 square miles
<br /> cation Maps(Plates 14, 15 and 17). of available aggregate are not permitted for mining and could be
<br /> lost to urbanization as the City of Tracy grows.
<br /> All three fans are very similar in age,lithology and source
<br /> area.The coarse casts are large]y composed of metagraywacke, Within this v1RZ-2 area are small islands of land classified
<br /> chert,and quartz. Smaller amounts of quartzite, schist, sand- MRZ-I and MRZ-3. The areas classified MRZ-1 contain lands
<br /> stone, basalt and andesite are present. Most of the cobbles are previous]),mined and backfilled with silt and clay.Toward the
<br /> subrounded to subangular, consistent with the relatively close center of the MRZ-2 area,tw•o portions are classified MRZ-3.
<br /> source area.The maximum clast diameter is 10 inches, with 40 These lands have been previously mined to a depth of 30 to 60
<br /> percent estimated to be +I inch.The fans contain an abnor- feet, but are not backfilled. These lands could contain potential
<br /> mally high amount of clay,and silt for PCC-grade deposits. sources of minable aggregate,but it is unknown whether it
<br /> Aggregate producers in these alluvial fans process materia] would be economically feasible to extract from them. At this
<br /> containing 10 to 50 percent clay,usually dependent upon depth. depth, a thick clay lens commonly occurs and could be the rea-
<br /> The upper 30 to 60 feet of the Corral Hollow Creek alluvial fan son that mining originally ceased. At the southeast corner of the
<br /> deposit(Sector A)usually contains significantly less clay than MRZ-2 area, land is classified MRZ-3 because it contains aeere-
<br /> deeper sections.The sand fractions consists mostly of quartz gate with such high clay,content that it may not be economic
<br /> and rock fragments. to mine.
<br /> Sand and gravel is currently being mined from Sectors A and The Corral Hollow Creek alluvial fan is divided into four
<br /> C.Just south of Tracy on the Corral Hollow Creek alluvial fan sectors:A-], A-2,A-3, A-4. These sectors represent areas with
<br /> (Sector A),three aggregate companies—Lone Star Industries, differing percentages of PCC-grade material. The percentages
<br /> Teichert Aggregates, and Granite Construction—are producing range from 85-50 percent PCC-grade aggregate. Sector A-1 con-
<br /> PCC-grade aggregate from three pits. Aggregate has been ex- tains the highest percentage of PCC-grade material and Sector
<br /> tracted from this fan since 1906(Clark, 1955). Hospital Creek A--f contains the lowest percentage. The non-PCC-grade per-
<br /> alluvial fan(Sector C)is approximately 12 miles south of Tracy. tentage reflects the clay content in each sector.
<br /> Sector C was mined in the early 1970's, probably for the con-
<br /> struction of Interstate Highway 5 or the California Aqueduct, SECTOR A-1
<br /> but no information on the actual product or destination is avail-
<br /> able. Brown Sand,Inc. has recently started mining sand and Sector A-1, which has been divided into 17 subsectors, is Io-
<br /> gravel from this sector for use as PCC-grade aggregate. To our cared at the southwest corner of the Corral Hollow Creek allu-
<br /> knowledge, no mining has occurred on the Lone Tree Creek al- vial fan just northeast of Highway 580. This sector contains the
<br /> luvial fan(Sector B), which is located between Sector A &C. highest percentage of PCC-grade aggregate (85 percent)in this
<br /> production district. Granite Construction Co. and Lone Star In-
<br /> SECTORS A-1,A-2,A-3,A-4— dustries,Inc. hold mining permits in this sector. Major urban
<br /> CORRAL HOLLOW CREEK ALLUVIAL FAN development surrounds these aggregate mines—two canals(the
<br /> California Aqueduct, and the Delta-Mendota Canal),one airport
<br /> Sector A(Corral Hollow Creek alluvial fan deposit)contains (Tracy Municipal Airport), and a water treatment plant.
<br /> the most valuable deposit of PCC-grade aggregate in the Stock-
<br /> ton-Lodi P-C Region. Sectors A-], A-2, A-3, and A-4 contain a Generally,alluvial fans are composed of finer sediment to-
<br /> total of 497 million tons of PCC-grade aggregate resources. wards the distal ends of the fan apron and coarser material near
<br />
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