SALT LAYDOWN PROJECT
- BONNEVILLE SALT FLATS
1997-99 Progress Report
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SALT LAYDOWN PROJECT
- BONNEVILLE SALT FLATS |
LAYDOWN FACILITY DESCRIPTION The Laydown facility (Figure 2) is comprised of brackish-water supply wells, about 11 miles of collection ditches and associated pumps, a 921-acre bedded salt deposit (Primary Pond #4 - PP#4), and a brine-distribution manifold. Because the collection-ditch system and brine-distribution manifold actually traverse about 13 miles on very flat ground, the biggest challenge is to move water from one end of a table-like flat area to the other end. The following mental Awalk through@ tour of the facility shows how this water movement is accomplished by the key components of the Laydown Facility.
Brackish water [11] is supplied to the system from seven alluvial-fan wells on the south flank of the Silver Island Range. The combined pump rate from these seven wells is approximately 7,700 gpm. [12] The brackish water is pumped from these seven wells into a series of collection ditches that move water south towards Interstate Highway 80 (I-80). By the time the brackish water flows south from the wells and passes under I-80 (a distance of about 4.5 miles), the water has slowed because of the nearly flat gradient of BSF and friction between the water and the walls of the collection ditch. To keep the brackish water flowing, a 6,000 gpm pump designated as Brackish-water pump #1 (BW#1) has been installed in the collection ditch south of I-80. By lifting the brackish water at Brackish-water pump #1, the brackish water can flow further south (about 1.5 miles) where the water is again lifted by Brackish-water pump #2 (BW#2). At BW#2, brackish water is pumped at a rate of about 6,000 gpm through a 24-inch diameter discharge pipe into the northwest corner of Primary Pond #4 (PP#4). A 35-day period of pumping (at 6000 gpm) is the minimum amount of time required to flood the 921-acre pond to a depth of 1 foot (assumes no loss from seepage or evaporation). This initiates the salt dissolution process. PP#4 is an old solar evaporation pond that was used to precipitate sodium chloride (as the mineral halite) from potassium-bearing brine during the economic mineral-recovery process. The 921-acre halite deposit is approximately 3 to 4 feet thick, and is estimated to contain about 8 million tons of sodium chloride. Once PP#4 is filled, approximately 15 days are required to move the freshly-pumped brackish water through PP#4 from its northwest corner to its southeast-corner outlet (a straight-line distance of 1.8 miles). During this transit time, the brackish water dissolves as much as 2 lbs of salt per gallon, and the density of the resulting brine approaches 1.2 g/mL (sodium chloride saturation).
The north-trending discharge pipe passes under I-80 and discharges brine into the west end of a brine-laydown manifold. The laydown manifold is an east-west trending, 1.5-mile long, 30-foot wide shallow canal that has been constructed between west-bound I-80 and a parallel frontage road. Using a brine-density range of 1.14 to 1.18 g/mL, an average brine flow rate of 6,678 gpm would deliver a salt load [13] of about 350 to 485 tons per hour (tph) [14] to the brine-laydown manifold. Brine flows north from the manifold and onto BSF through twelve culverts that are uniformly spaced along the manifold =s length. A period of about 8 hours is required for the brine volume in the laydown manifold to be completely exchanged. See Appendix 7 for calculations of brine transit time from 1) southeast corner of PP#4 to BP#3, 2) BP#3 to the west end of the laydown manifold, and 3) west end to the east end of the laydown manifold.
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