SALT LAYDOWN PROJECT
- BONNEVILLE SALT FLATS
1997-99 Progress Report
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SALT LAYDOWN PROJECT
- BONNEVILLE SALT FLATS |
METHODS Monitoring Well Sampling and Analyses BLM collection of annual BSF groundwater-brine samples was initiated in 1994. The samples were taken during an August-September period [3] from 20 monitoring wells in the shallow-brine aquifer [4]. These 20 wells were selected because of their proximity to the International Track and the federal-lease collection ditch and are shown in Figure 1 (see Appendix 1, tables A1.1 and A1.2 for a listing of wells sampled by BLM during 1994 and 1996). To date, samples have been collected during Fiscal Year [5] 1994, 1996, and 1997 (FY94, FY96, and FY97). Although the 20 selected wells were sampled during FY94 and FY97, only 16 of the 20 wells were sampled during FY96. No explanation for this departure in number of wells sampled was given. Because BLM funding available for the project was limited during 1997, only FY94 and FY96 samples were analyzed for chemical constituents. BSF-groundwater samples were collected from the selected monitoring wells with a 3-foot long, 1.6-inch O.D. polyethylene bailer, and stored in 8-ounce (237 mL), low-density polyethylene (LDPE) sample bottles. Density measurements and chemical analysis for specific ions were determined for BLM =s BSF-groundwater samples by Chemical and Mineralogical Services (CMS), Salt Lake City, UT. Sodium and potassium concentrations were determined by flame photometry using an Instrumentation Laboratories Model 343. Calcium and magnesium were determined by inductively-coupled plasma argon spectrometry (ICP) using a Perkin-Elmer ICP Model 6500. Sulfate (SO4) was determined gravimetrically by barium chloride precipitation, and chloride was determined by silver nitrate titration using the Mohr method. Sample TDS were calculated by summation of cation and anion concentrations.
Mason and others (1995, pp. 46-51, Table 4) have also listed analytical values for BSF groundwater-brine samples collected by USGS during 1992-1993. The USGS samples are from a larger suite of monitoring wells that include 9 of the same wells sampled by BLM in FY94, FY96, and FY97 (see Appendix 2, Table A2.1 for a listing of the 9 wells sampled by USGS during 1992-93). Salt Crust Thickness Measurements During a 3-year period (September 1994 and 1995, and October 1997), BLM excavated a total of 10 test pits along a 7-mile segment of the International Track, within 1 mile of the track centerline (see Figure 1). This segment extended from mile post #4 to mile post #11 (original 1960-1974 locations). The 10 pits were located adjacent to 6 reference BSF monitoring wells (blm-42a, blm-43c, blm-46, blm-60/usgs-2, blm-93, and usgs-9). The first few pits were excavated with a variety of hand tools (i.e., screwdriver and geologic pick). [6] A chainsaw was much more efficient in excavating the later pits. Successive salt and gypsum strata comprising the salt-crust thickness exposed at each pit site were described and their respective thicknesses measured (see ABLM Test-Pit Studies@).On August 17, 1998, BLM excavated another test pit to determine if any visible changes in salt-crust strata thickness had occurred since the start of the Laydown project (November 1997). The 1998 pit is located approximately 95 feet NW of blm-93 (see Figure 1), and is approximately 2 feet NE of a BLM test pit which was excavated October 14, 1997. A chain saw was used to excavate the 1998 test pit, and a 21-inch wide, 24-inch long, 13-inch deep pit resulted. Successive salt and gypsum strata exposed in this pit were described and their thicknesses measured. Laydown Brine Sampling and Analyses Reilly-Wendover During the pumping periods of November 1, 1997-April 30, 1998, and November 1, 1998-April 30, 1999, Reilly collected brine samples daily (Monday through Friday) from Brine pump site #3 (BP#3). Brine-pump hour-meter readings were recorded concurrently with sample collection. Density measurements and chemical analysis for specific ions were determined for each sample in Reilly =s Wendover Plant laboratory. Sodium and potassium concentrations were determined by flame photometry using an Automatic FP 1L943 [7]. Calcium plus magnesium concentrations were determined by Disodium Ethylenediaminetetraacetate (EDTA) titration using Calmagite as an endpoint indicator. Sulfate (SO4) was determined gravimetrically using barium chloride precipitation. Daily sample sodium, magnesium, and potassium concentrations (g/L) were converted to their respective chloride salts in units of weight percent and tons, based on sample mole balance and density. Analytical results for daily samples collected November 1, 1997-April 30, 1998, and November 1, 1998-April 30, 1999 are listed in Appendix 3, Tables A3.1-A3.13.BLM-Salt Lake Field Office To provide independent verification of Laydown-brine quality, BLM collected triplicate samples of Laydown brine from sample sites at key facility locations. These samples were collected during the pumping periods of November 1, 1997 - April 30, 1998, and November 1, 1998 - April 30, 1999 (FY98 and FY99 pumping periods). Sample triplicates were identified as AA@, AB@, and AC@, and attached to a sequential number (i.e., A-1, B-1, C-1; A-2, B-2, C-2; etc.). The AA@ triplicates were submitted to Reilly, AB@ triplicates were retained by BLM to be analyzed by Chemical and Mineralogical Services (CMS - BLM=s contracted analytical laboratory), and the AC@ triplicates were submitted to University of Arizona, Department of Chemistry (U of Az - STS=s contracted analytical laboratory).The key-facility sample sites include the concrete vault at Brine pump site #3 (BP#3), and the west and east end of the Laydown manifold (LDM-W and LDM-E); see figures 2 and 3. These sample sites were selected because they comprise the primary Laydown-brine distribution system which directly affects the BSF. Additionally, a lag in brine travel time exists between BP#3 and LDM-E, and these sample sites provided easily-accessible check points to more closely monitor changes in brine quality. Brine-density measurements using a CL-USA #458438 hydrometer were determined in the field for each sample. Hour-meter readings were recorded concurrently with sample collection at Brine pump site #3. Chemical analyses and density measurements for AB@ triplicates were determined by CMS, Salt Lake City, UT. Sodium and potassium concentrations were determined by flame photometry using an Instrumentation Laboratories Model 343. Calcium and magnesium were determined by inductively-coupled plasma argon spectrometry (ICP) using a Perkin-Elmer ICP Model 6500. Sulfate (SO4) was determined gravimetrically by barium chloride precipitation, and chloride was determined by silver nitrate titration using the Mohr method. Sample TDS were calculated by summation of cation and anion concentrations. Sample sodium, magnesium, and potassium concentrations (g/L) were converted to their respective chloride salts in units of weight percent and tons, based on sample mole balance and density.FY98 Pumping Period - BLM collected 24 samples composed of 72 triplicates (A-1, B-1, C-1, through A-24, B-24, C-24). These samples were collected on January 15, 23, and 26, March 2, 10, and 27, and April 9 and 27, 1998. The AA@ triplicates were submitted to Reilly the day of collection (see Appendix 3, tables A3.15 - A3.20 for complete analyses). Rather than delaying the Laydown-sample analyses until the end of the 6-month pumping period (i.e., April 30, 1998), BLM submitted 17 of the 24 AB@ triplicates to CMS in two different sample sets, B-1 through B-9, and B-10 through B-24. Set B-1 through B-9 was collected during the January 15-26 period, and analyzed by CMS on February 12, 1998. Sample set B-10 through B-24 was collected during the March 2 - April 27 period, and 8 of these 15 samples were analyzed by CMS on May 4, 1998. CMS analytical results for BLM=s FY98 AB@ triplicates are listed in Appendix 4.FY99 Pumping Period - BLM collected 31 samples comprised of 93 triplicates (A-25, B-25, C-25, through A-55, B-55, C-55). These samples were collected on the following dates: November 6 and 17, and December 3, 1998; January 14 and 22, February 19 and 25, March 12 and April 19-20, 1999. Samples collected on February 25, March 12, and April 20, 1999 also include samples from the Federal-Lease collection ditch (sample site is where the ditch brine flows under the west-bound lane of I-80). Sample triplicates collected by BLM for Reilly were delivered to Reilly on the day of sampling. BLM and STS sample triplicates will be submitted to CMS and U of Az for analyses at the end of April 1999. University of Arizona, Department of Chemistry During the FY98 Pumping Period, BLM submitted a total of 24 AC@ sample triplicates for chemical analyses to M. Bonner Denton, Ph.D., Department of Chemistry, University of Arizona. Nine AC@ sample triplicates were submitted on February 12, 1998, and 15 AC@ sample triplicates were submitted June 5, 1998. After dilution, the samples were analyzed for sodium (Na), calcium (Ca), potassium (K), and magnesium (Mg), using a Thermo Jarrell Ash IRIS-HR inductively coupled plasma (ICP) emission spectrometer. The spectrometer was calibrated using solutions made from pure salts.Analyses for samples C-1 through C-9 were reported as g/L Na, Ca, K, and Mg. Analyses for samples C-10 through C-24 were reported as g/L NaCl, CaCl2, KCl, and MgCl2. To compare U of Az analytical results with CMS analyses, chloride salt concentrations reported for samples C-10 through C-24 were converted to their respective Na, Ca, K, and Mg concentrations. Because U of Az did not report chloride and sulfate (Cl and SO4) concentrations, CMS values for Cl and SO4 from matching sample triplicates were used to derive mole balance for each sample (see Appendix 4, Tables A4.1 - A4.2). U of Az analytical results for BLM =s FY98 AC@ triplicates are listed in Appendix 5.Laydown Brine Flow-rate Measurement Reilly-Wendover Individual flow rates for the two pumps (# =s 1 and 2 - see Figure 3) at Brine-pump site #3 were estimated from pump curve number AP 1406 (dated March 1988) supplied by Cascade Pump Company. A flow rate of 6000 gpm was selected based on matching this pump curve with the pump's horsepower rating and a total dynamic head of 11.2 feet (distance between the average brine level in the collection ditch and the pump-discharge outlet in the concrete vault). Reilly used the 6000-gpm flowrate value for its initial brine-production calculations. [8]BLM-Salt Lake Field Office Doppler-Ultrasonic Flowmeter Demonstration - Two different models of Doppler-ultrasonic flowmeter (each from a different manufacturer) were tested separately at Reilly =s BP#3 on January 26, 1998. After the twin transceivers for each flowmeter were mounted on the 18-inch I.D. pump-discharge pipe and the flowmeter instrumentation was turned on, the pipe I.D. was entered into the flowmeter via the instrument touch pad. Readings in gallons per minute (gpm) were taken from each model over a 15-minute period, and the following gpm ranges were obtained from the two flowmeters:
Both Doppler-ultrasonic flowmeters produced lower gpm readings than the 6000 gpm estimated from the pump curves. Several reasons may have contributed to the lower than expected readings: 1) areas of non-laminar flow may have been present in the section of pipe being tested; and 2) the HDPE pipe that connects the pump to the concrete vault is Aegg-shaped@ in its cross section, which would introduce a difference in the actual pipe I.D. (i.e., slightly greater or less than 18 inches) and consequently affect transceiver readings. Therefore, both flowmeters require calibration. This calibration can be accomplished through adjustments in the instrument software. [9]Hand-held Flowmeter Demonstration - Reilly and BLM tested a hand-held 2100-LX flowmeter [10] at Brine-Pump Site #3 where the #2 pump discharges into the concrete vault through a 16-inch I.D. section of pipe. The test was conducted so that brine flow rates onto the Salt Flats could be routinely measured and compared with company-supplied flow-rate estimates from pump curves. The measurable flowrate range of the 2100-LX flowmeter is from 0.1 to 25 feet per second (fps). Readings in fps were taken by moving the impeller-tipped probe of the flowmeter from the outside edge of the discharging brine-flow cross-section to its center and averaging the results presented on the instrument =s digital display. To determine the actual pump-generated gpm from the fps recorded by the 2100-LX hand-held flowmeter, a range of 3000 to 9000 gpm was converted to fps and plotted as an X-Y plot so that the field fps reading could be converted directly to gpm. Plots of fps vs gpm for 16, 18 and 24-inch I.D. pipe sections are shown in Appendix 6, figures A6.1 - A6.3, and the calculations used to derive the plots are summarized at the beginning of Appendix 6.Separate flowrate readings were taken on April 27, November 6, and December 3, 1998 and closely match each other. The measurements produced by the 2100-LX flowmeter are listed below for their respective dates and are expressed both as fps, and as gpm (in parentheses):
Rather than continuing to use pump-curve flowrate estimates, Reilly and BLM decided to use actual measured flowrate values provided by the 2100-LX flowmeter. The gpm range measured in April (6650 to 6725 gpm) was averaged to produce a value of 6688 gpm, which was subsequently used to calculate the monthly chloride-salt tonnages presented in Appendix 3, Tables A3.1 - A3.6 and A3.8 - A3.13. The flowrate range from which the average value was derived has remained consistent into the second year of the Laydown Project (Nov and Dec, 1998 flowmeter readings).
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