Orru effects

6th International Conference on Sustainable Development in the 577 Minerals Industry, 30 June – 3 July 2013, Milos island, Greece Possibilities for mitigating negative effects of noise and dust caused by extraction of sand, gravel and peat

M. Orru and H. Milvek Department of Mining, Tallinn University of Technology and Geological Survey of Estonia, Estonia A. Anepaio, S. Vendla and I. Valgma Department of Mining, Tallinn University of Technology, Estonia ABSTRACT The Estonian legislation requires an environ-mental impact assessment prior to issuing a permit for extracting mineral resources. Extrac-tion of sand, gravel and peat involves dust and noise, their amount depending on the used tech-nology.

Usually, the average noise level in the peat fields is 58.2 dB. The content of fine peat dust (<10 μm, PM10) usually ranges between 0.002 and 0.448 mg/m³ per 30 minutes during opera-tions (Orru et al., 2012b).

Measurements in sand and gravel pits show that the content of fine dust (<10 μm, PM10) in the ambient air averages 0.011 mg/m³ per 60 minutes during pit operation. Modelling shows that noise in the sand and gravel pits dies away below 40 dB before reaching residential build-ings.

An important alleviating measure is preserv-ing the surrounding forest. Precise models of the extent of dust and noise impact have to be com-piled.

1. INTRODUCTION In order to obtain a mining permit, an environ-mental impact assessment is needed, which should include an assessment of diffused noise and dust spread. In this article we observe the extent of diffusion of noise and dust from ex-ploited gravel and sand deposits to surrounding areas. Accordingly, we present and analyse po-tential mitigation measures. The study areas are Vinni and Tatramäe deposits in Estonia (Fig. 1).

2. MATERIAL AND METHODS Extraction of sand, gravel and peat involves dust and noise, their amount depending on the applied technology. Environmental impact as-sessment should include measuring, modelling and analysis of the extent of the diffusion of dust and noise in the environment.

2.1 Peat

2.1.1 Dust measurement The main proportion of peat dust emerges dur-ing peat production (milling and collection). In order to find out the exact amount of dust, peat dust measurements were carried out on the San-gla and Varudi peat fields during the summer of 2011 (Lehtmets et al., 2012, Fig. 2).

Fine particle PM10 measurements were car-ried out following the Ambient Air Protection Act (RT I, 31.12.2010, 31). Fine particle PM10 was measured using the Dust Trak II HC dust analyzer for 60 min at the 1.5 m level on a tri-pod.

Figure 1: Locations of study areas.

578 6th International Conference on Sustainable Development in the Minerals Industry, 30 June – 3 July 2013, Milos island, Greece

2.1.2 Noise measurement Noise levels were measured following the noise measurement method (RTL 2002, 38, 511) and each point was measured with noisemeter TES 1254 for 60 minutes.

2.2 Sand and gravel Since the sand and gravel deposits are not being mined at the moment, modelling is needed to complete the environmental assessment.

2.2.1 Dust modelling Dust modelling was done with the CadnaA 4.1 + APL software and the following aspects were taken into consideration: fieldwork results, im-pact of forest, wind direction and speed (CAA), and size and location of spoils.

Field measurements were used for creating a model assuming that in the active equipment in the pit include an excavator, a mobile crusher

and a truck. Modelling results show that already 300 meters away the dust level will be reduced below the upper limit of allowed levels (Fig. 5).

2.2.2 Noise modelling Noise modelling was done with the CadnaA 4.1 software and the following aspects were taken in consideration: noise of the machinery, impact of forest, transport noise, and size and location of spoils.

One excavator (80 dB), one mobile crusher (90 dB) and a dump truck (70 dB) were placed in every pit in the model. Modelling results show that the noise from the pit dies away be-low 40 dB before reaching inhabited areas (Fig. 3). The model indicates that pit noise will be marginal. The main sources of noise are the highway and other surrounding roads (Orru et al., 2012a).

3. RESULTS

3.1 Peat Measurements of peat dust (fine particles less than 10 micrometer, PM10) diffusing in the am-bient during an operating period of 30 minutes gave results between 0.002 and 0.448 mg/m³.

Diffusion of dust is inversely proportional to the distance from the source and the spreading distance itself is in exponential dependence. Therefore, critical quantities of dust spread only close to the source.

Based on the acquired knowledge, it is cer-tain that the annual amount of peat dust will not cause a health hazard to the surrounding popula-tion.

3.2 Noise Noise caused by peat transport from the peat production areas was measured during the summer of 2011. A peat production area had the average noise level of 40 dB.

3.3 Sand and gravel

3.3.1 Vinni gravel pit - predicted cumulative noise together with a neighbouring race track Since the Vinni gravel pit is not being exploited, modelling was used to determine noise levels in

Figure 2: Measuring peat dust in the Sangla peat field.

Figure 3: The Vinni gravel pit and race track noise model.

6th International Conference on Sustainable Development in the 579 Minerals Industry, 30 June – 3 July 2013, Milos island, Greece

the pit and in neighbouring residential areas (Fig. 3).

The Estonian Minister of Social Affairs set the noise levels tolerable for life (4 March 2002, Regulation No. 42 "Standard Noise Levels for Residential and Recreational Areas, Residential and Public Buildings, and Noise Measurement Techniques"). This regulation permits noise lev-el below 40 (35) dB during the day and below 30 dB at night.

3.3.2 Tatramäe II, Kruusa and Audevälja gravel pits predicted cumulative effects model Measurements and modelling results indicate that when Tatramäe II, Kruusa and Audevälja gravel pits are simultaneously operating, the noise level increases by 10 dB (Orru et al., 2013, Fig. 4).

3.3.3 Cumulative dust model Dust from the Tatramäe II, Kruusa and Audevälja gravel pits spreads up to 300 meters away. As the Tatramäe II gravel pit is located 300 m away from the Kruusa and Audevälja pits, it is considered as separate dust source (Fig. 5).

4. MITIGATING METHODS

4.1 Peat dust An important alleviating measure is preserving the surrounding forest (preferably to a width of at least 50 m). The width of a protective forest zone should be comparable to the height of the

trees. Peat transportation machinery must ensure that the load is well enough closed to minimise the impact of dust to the environment. Also, for the protection of employees’ health, peat mining machinery booths have to be impervious to dust. In order to reduce the overall amount of dust during dry and windy periods, pit roads should be moistened regularly and the maximum speed of transporting vehicles limited to 30 km/h.

4.2 Peat noise The most important aspect in peat noise minimi-sation is the preservation of neighbouring for-ests, which ideally should be at least 50 meters wide.

5. CONCLUSIONS The results of this study show that the usual av-erage noise level in the peat fields is 58.2 dB. If residential houses are at some distance from the production area and separated by a protective forest the noise level there will be low (35-40 dB). The average content of fine peat dust (<10 μm, PM10) is usually 0.002-0.448 mg/m³ per 30 minutes during pit operation.

Measurements in sand and gravel pits show that the average content of fine dust (<10 μm, PM10) in ambient air is 0.011 mg/m³ per 60 minutes during pit operation. The permitted dai-ly average limit is 0.5-2 mg/m3 for the working environment and 0.05 mg/m³ for the living envi-ronment.

An important alleviating measure is preserv-ing the surrounding forest (50 m). The width of

Figure 4: Proposed Tatramäe II gravel pit as a major noise source.

Figure 5: Cumulative effect of the dust modelled.

580 6th International Conference on Sustainable Development in the Minerals Industry, 30 June – 3 July 2013, Milos island, Greece

a protective forest zone should be comparable to the height of the trees. Precise models of the ex-tent of dust and noise impact have to be com-piled. If other extraction fields exist in the vicin-ity, cumulative models need to be constructed.

REFERENCES Orru, M., R. Ramst and H. Milvek, (2013). Tatramäe II

kruusakarjääri mäeeraldise kasutuselevõtuga seotud keskkonnamõju hindamise (KMH) täiendatud ja parandatud aruanne (Environmental impact assess-ment of exploitation of the Tatramäe II gravel pit claim, improved and amended report, in Estonian). Tallinn: OÜ Eesti Geoloogiakeskus.

Orru, M., K. Lehtmets, R. Ramst and H. Milvek, (2012a). Vinni, Vinni II, Vinni III kruusakarjääri mäeeraldiste kasutuselevõtuga seotud keskkonnamõju hindamise aruanne (Environmental impact assessment of exploi-tation of the Vinni, Vinni II and Vinni III gravel pit claims, in Estonian). Tallinn: OÜ Eesti Ge-oloogiakeskus.

Orru, M., R. Ramst and H. Milvek, (2012b). Varudi II turbatootmisala kasutuselevõtuga seotud keskkon-namõju hindamise (KMH) aruanne (Environmental impact assessment of exploitation of the Varudi II peat extraction field, in Estonian). Tallinn: OÜ Eesti Ge-oloogiakeskus.

Lehtmets, K., M. Orru and R. Ramst, (2012). Sangla II turbatootmisala kasutuselevõtuga seotud keskkon-namõju hindamise täiendatud ja parandatud aruanne (Environmental impact assessment of exploitation of the Sangla II peat extraction field, in Estonian). Tal-linn: OÜ Eesti Geoloogiakeskus.