Performance evaluation of a dust-dispersion model for haul trucks

R computer model named rhe "Dynamic Compon~nr Program" (DCP) was specifically designed for. predicting the dispersinn nf dust from haul trucks ut surface mines. Validation of the DCP was completed 1~y compasir~~ its re. ~ults with rfrc results ~f the ISC3 modef and wifh octual dusi measurements faken from m o operaifrr~ mine sites. Comparisons of rhe field measuremetlrs, predicrions of the JSC3 model and rke predicrions of the DCP d~monsrrare thut the resulrs from the DCP represent, on average, an 85% improvement over the ISC3 dusr dispersion model resula. Introduction Controlling dust emissions at surface mining operations is an ongoing battle. Methods for controlling dust include applying water or chemicals to the dust source and collecting and filtering the dust from the source. Identifying the dust sources and modeling of the dust dispcrsion are also important tools in dust controI that allow for the identification of potenliaIly hazardous areas. As part of the permitting process for a mining operation. pollutant modeling can be required if the mine operation emits an amount of any pollutant above certain threshold limits. This modeling is used to determine potential impact arcas. Dust is the mist prevalent pollutant f& surface mining operations.and the most common model used by mining companies for modeling dust is the ISC3 model created by the U.S. Environmental Protection Agency ( U.S. EPA). However, this model has been shown to overpredict dust dispersion from actual mining operations by a factor of two to five (Cole and Zapen, 1995: U.S. EPA, Phase 111.1995). A possihlc cause of this overprediction has been identified as the inabi tity of the TSC3 model to accurately predict dispersion from mobile source emissions (Reed et al,, 2002: Reed, 2003). Recently, the ISC3 model was modified to accommodate dust dispersion from mobile haul trucks at surface mine sites. This model, titled the DCP, has been discussed in detail in previous research publications (Reed et at ., 2002; Reed. 2003). Testing of this model with actuat Field dara was completed at two surface mine sites a stone quarry in Virginia and a coal mine preparation plant in Pennsylvania. Field studies Gravimetric and instantaneous dust samplers were used to measure respirable, thoracic and total dust concentrations with the thoracic size range being the primary interest. The respirable portion of dust measured had a median size of 4.0 pm (Lippmann, 1995). The thoracic portion of dust is equivalent to the particulate rnattet I 10 pm (PMIII) size definition derermincd by the U . S. EPA, which has a median size range of 10.0 pm (Lipprnann, 1995). The median size of 50 pm was measured for total dust (MIE Inc., 2000). I n addition, the size range of 1.5 to 2 1.3 pn was sampled usingcascade Impactors. The sampling equipment used For these studies consisted of MIE personal data RAMs, MSA Escort ELF personal sampling pumps, 10-mrn Dorr-Oliver cyclones and BGI GK2.69 cycIones. Samples were collected on 37-mm filters. To measure respirable dust. Escort ELF persanal sampling pumps were fitted with 10-rnm Dorr-Oliver cyclones. The pumps were set to run at 1.7 Umin (Banley et a1 ., 1994). The MIE personal data RAMs were used to collect instantaneous dust concentration measurements. They recarded dust concentrations every 2 seconds. The MIE personal data RAMs were fitted with 10-mm Dam-Oliver cyclones and were operated at I . 7 Llmin. Thoracic dust was measured using Escort ELFpersonal sampling pumps fitted with I361 GK2.69 cyclones. The sampling pumps for the thoracic portion were operated at 1.6 Llmin (Maynard. 1 999). Total dust concentrations were measured by attaching 37-mm filters directly to the Escort ELF personal sampling pumps.which were set to operate at 1.7 Llrnin. The Cascade Impactors contained six stages and were connected to Escort ELF personal sampling pumps operating at 2.0 Llrnin. This flow rate aIIowed for the measurement of dust concentrations for the cut-off si7.e ranges of 21.3. E4.8. 9.8,6.0, 3.5 and 1.55 Krn (Andersen Instruments Inc., 2002). The dust samplers were arranged as shown in Fig. 1. The grid layout of the stations was 15 m (50 ft) between each