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Show and Farmington Bay are both shown with salinities of 3- 6 percent. Bear River Bay is generally fresher than Farmington Bay. Bear River Bay is separated from the main body of the lake by IMC Kalium Ogden Corp.' s dike and the Bagley Fill which was constructed about 1900 and extends eastward from Promontory Point to Little Mountain. Construction on the northern railroad causeway began in 1956 and was completed in 1959. This rock- fill causeway separates the main body of the lake between Promontory Point to Lakeside and was known as the Southern Pacific Railroad Causeway. This causeway includes the Rambo and Saline Fills which were constructed about 1900. This created a separation between Bear River and Gunnison Bays from the main body of GSL. With the completion of the causeway, the main body of GSL was now divided into two parts, the south and north arms. Even with the engineered permeability of the causeway and the incorporation of two 15- foot- wide by 20- foot- deep box culverts through the causeway, brine mixing was greatly diminished. Since 1960, the two main arms of the lake have developed different physical and chemical characteristics which vary as the lake level changes, and as changes are made to the structure. Farmington Bay was part of the main body of the south arm of GSL until it was isolated by the construction of two earthen causeways. The first causeway ( southern fill) was built from the south end of Antelope Island southeastward to the mainland in 1952. This structure inhibited water exchange between the main body of the lake and the bay at the south end of the island, and channeled the full flow of the Jordan River into Farmington Bay. The second causeway ( Davis County) extending from the north end of Antelope Island eastward to the mainland, was constructed in 1969. With the construction of this causeway, Farmington Bay was essentially isolated from the main south arm of the lake, with the exception of two bridged openings, and mixing between the two bodies of water was severely restricted ( Gwynn, 1998a). Farmington Bay Farmington Bay is isolated from the main body of GSL when its level is below the top elevation of the Davis County Causeway and the Antelope Island southern causeway fill. Because of the inflow of freshwater from the Jordan River and groundwater inflows, the lake brines tend to be " flushed" from the bay through openings in the Davis County Causeway. Periodically, denser brines from the main body of the lake flow back into Farmington Bay underneath the lighter, fresher brines from the bay. This phenomenon is known as " bi- directional flow," and prevents the waters of Farmington Bay from becoming completely fresh. Bi- directional flow occurs through the Davis County Causeway's bridged openings, and through a narrow culvert to the east which was installed in 1992. Bi- directional flow through these two openings is illustrated in Figure 9 and describes a similar dynamic occurring through the northern railroad causeway. When the lake's elevation is below 4208 feet, the salinity of Farmington Bay is approximately half or less than that of the main body because of freshwater flows of the Jordan River into the bay. When the lake's elevation rises above 4208 feet and the causeway is over topped, the 43 |