2013-01-18_REVISION - C1981008 - Laserfiche WebLink

Home Browse Search

for dust control. Following is an analysis to determine which of these potential sources accounts for the observed increased salinity. A conservation of mass water balance approach was utilized to determine if the application of water from the mine pit could possibly be responsible for the increase in soil salinity. In this approach the total unit weight salt increase in the soil stockpiles isassumed to be equalto the unit weight basis of salt added to the soil stockpiles through the application of mine pit water. The following assumptions areused to estimate total quantity of mine pit water required to increase the soil salinity compared to native conditions.  All applications follow conservation of mass.  No runoff occurred from the water trucks.  EC of the mine pit water did not change throughout the duration of applications to the soil stockpiles. EC = 5,000 umhos/cm o  To convert EC(umhos/cm) to Total Dissolved Solids(TDS)(mg/L): EC x 0.64(Soil Improvement Committee, 2002 and Thorup, 1984) o  Soil porosity of 50%.  Soil was applied in uniform lifts to the soil stockpiles.  Water application was uniform on each lift and across the entire surface of the soil stockpile.  Entire increase in soil salinity was due to the application of mine pit water.  Volume of soil within the individual soil stockpiles are: Lift A = 225,000 cubic yards o Lift B = 348,000 cubic yards o Mixed A and B= 132,000 cubic yards o Lift Amaterial has an average soil ECeof 3.7 dS/m, based on soil testing conducted with the DRMS and OSM. The ECeof the Lift A baseline data indicates that the baselinesoil ECewas 2.9 dS/m. These data indicate that the soil ECehas increased by approximately 0.8 dS/m or 256 mg TDS/kg. This equates to an increase of approximately 121,300 pounds of TDS in the Lift A soil stockpile. To add this quantity of TDS to thatstockpile using mine pit water approximately 4.5 million gallons would have had to be applied to the stockpile. That is the equivalent of 1.4- water trucks(9,000 gallon capacity) per day for 365 days. Using the same methodology, theLift B soil stockpile increased from 2.7 to 3.7 dS/m. This increase would require an additional approximately 8.8 million gallons of mine pit water or the equivalent of 2.7 water trucks per day for 365 days. The Mixed A and Bstockpile increased from 2.8 to 4.1 dS/m and this would have required 4.3 million gallons of mine pit water, equivalent to 1.3 water trucks per day for 365 days. Based on conversations with the New Horizon Mine the use of the water trucks for dust control is limited and only used when required to eliminate fugitive dust. The highest use of water for dust control is during the summer when little or no natural moisture is present and dusty conditions exist.The water truck is only used on soil stockpiles when the soil is being stripped 6 {00136879.1 }