1978 



Limestone in the Coast Ranges 



31 



FMC Corporation (Food Machinery and Chemi- 

 cals Corponnion; Wcsrvaco (Chlorine Products Com - 

 panv; California i'hcmical (Corporation). Westvaco 

 Chemical Division (now known as Inorganic Chemi- 

 cals Division) of FMC^ Corporation and its predeces- 

 sors purchased oyster shells to manufacture lime at 

 their N'euark plant from 1931 to about 194S. Most of 

 the lime \^ as used to react with seawater bittern to 

 precipitate magnesium hydroxide — a basic raw 

 material used extensively in the chemical and basic 

 refractories industries. Some lime and hydrated lime 

 made from shell also were sold commercially — per- 

 haps as late as 1950. in addition, small amounts of shell 

 were sold as poultry feed. 



The shells were purchased from Captain L. H. 

 Beck, who dredged in the southern arm of San Fran- 

 cisco Bay (see Pioneer Shell Company). Although 

 Westvaco formerly owned shell-bearing land, the 

 deposit was never developed. The land eventually was 

 acquired bv the Airport Authority for extension of 

 runways of San Francisco Airport. Recovery of shells 

 by Captain Beck was by suction dredging. The shells 

 were washed free of mud aboard Captain Beck's 

 dredge and transferred by barges, via Newark Slough, 

 to the plant at Newark. Here, the shells were burned 

 in a gas-fired rotary kiln 315 feet long by IVi feet in 

 diameter. In order to obtain a quality quicklime, the 

 kiln had a basic refractory lining and was operated at 

 temperatures as high as 1,600°C (Seaton, 1931, p. 641; 

 1942, p. 23). Capacity of the lime plant was about 

 12,000 tons per year. The lime product was reported 

 to contain less than 0.5% SiO;, around 0.2% Fe,()„ 

 0.2% Al,(), and about 1.0% MgO. A detailed discus- 

 sion of the reaction of quicklime uith bittern and 

 other processing data are given by Seaton (1942). 



From 1947 to 1968, magnesian lime made from cal- 

 cined dolomite was used instead of high-calcium lime 

 to take advantage of the magnesium available in dolo- 

 mite. The dolomite was obtained from the company's 

 Westvaco deposit in San Benito County (see Westvaco 

 deposit under Cjabilan Range District) and calcined at 

 the Newark plant until operations ceased in .August 

 1968. 



Other references: Logon, 1947, p. 205; Davis, 1950, p. 298-300; Ver- 

 Plonck, 1957, p. 319, 322; Bowen and Groy, 1959, p. 37; Goldman, 1967, 

 p. 24-25. 



Ideal Cement Company (Pacific Portland Cement 

 Company). Ideal Cement Company (420 Ideal Ce- 

 ment Building, Denver, Colorado 80202) owns and 

 leases about 35,000 acres of tide and submerged land 

 in south San Francisco Bay. Large shell deposits with- 

 in this area provide the principal raw materials used 

 at the company's cement plant located at the Port of 

 Redwood City.* 



Pacific Portland Cement Company constructed a 

 Portland cement plant at Redwood City in 1924 — ap- 

 parently to supplant the production from its (dement 

 Hill plant in Solano County, which was largely im- 

 porting limestone. It was planned to utilize oyster 

 shells and associated mud of San Franciscf) Bay as a 

 basic resource at the new plant, (^)ntrol of the princi- 

 pal shell deposits of San Francisco Bay was attained 

 when the cement company acquired the holdings of 

 the Morgan Oyster Company. The latter company not 

 only owned a large acreage of oyster beds on both 

 sides of the Bay between Millbrae and Alviso, but also 

 leased 4,730 acres from the State of California in 1923 

 for the purpose of dredging shells. I'his lease also was 

 taken over by Pacific Portland Cement Company. In 

 1958, the lease expired and a new renewable lease 

 (Public Resources Code 1850.1) was issued to Ideal 

 Cement (-ompany (successor to Pacific Portland Ce- 

 ment Company in 1952) for the same area. I he lease 

 area is situated just north of the San Mateo Bridge 

 causeway in T. 3 S., R. 3 W., T. 4 S., R. 3 W., and T. 

 4 S., R. 4 W., M.D. The oyster shell deposits so ac- 

 quired have been the sole source of lime since 1925, 

 when production began, and the mud associated with 

 the shells has provided the principal source of silica, 

 alumina, and iron oxide. 



Since the expansion of the plant in 1927, when ce- 

 ment production capacity was raised to 5,000 barrels 

 per day, there has been no extensive expansion of the 

 Redwood C-ity plant. However, certain plant changes 

 between 1927 and 1966 have increased production 

 capacity about 40%. By assuming that production has 

 been close to capacity and that shells are the sole 

 source of lime in cement manufacture, it is estimated 

 that approximately 25 million tons of shell (excluding 

 mud) have been produced since 1925. Practically all of 

 this was used to manufacture cement, although small 

 amounts of shells were washed and processed consist- 

 ently from 1927 to 1950 for use in soil conditioning 

 and livestock feed. Ihe latter products were marketed 

 under the "Fmpire Brand" name. It is further estimat- 

 ed that at least 6 to 7 million tons of mud was produced 

 with the shells during 1925-1967. Most of the mud 

 produced was u.sed in the manufacture of cement. 



Land controlled by Ideal Cement includes most of 

 the shell deposits of southern San Francisco Bay, 

 shown in figure 2 and described above. All of Ideal's 

 recent production and perhaps most of the past pro- 

 duction has come from a 4- to 15-foot thick shell layer 

 in the vicinity of the San Mateo Bridge causeway (Sto- 

 ry et al., 1966, p. 48). Shells and associated soft bay 

 mud (silty clay) arc obtained by one of two dredges 

 (one is kept on standby), each of which is fitted with 

 a 15- or 16-inch suction pipe and cutter head (Davis, 



• Ideal Cemenc Company ceased shell dredging operations and cement manu- 

 facture at Its Redwood City plant at the end of 197(V On NovemlxT 20. 

 1970, the company announced plans to close the plant because of the high 

 capital cost of bringing the old and inefficient plant up to air pollution 

 control standards set bv the State of California. (Plans to close the com- 



pany's San Juan B.uitista plant, announced concurrently, were later re- 

 scinded ) It uas planned to continue to use the facility as a distribution 

 terminal for cement manufactured at Ideal's new cement plant in Seattle, 

 Washington. 



