purposes using the method presented in Chapter 3. Vehicle speed on the road leading to the plant area was set to 60 km/h, and closer to the gate, to 20–30 km/h.
In the operational phase, the most significant sound sources at the nuclear power plant will be the transform- ers, the steam turbine, the generator, and the turbine hall ventilation system. While the transformers will generate a narrow-band, humming-type sound, they will generally not be very loud. For the calculation, the free-field sound level of the transformer noise source was assumed to be 80 dB(A) at the distance of one meter from the source. The narrow-band nature of the transformer sound source was taken into account in the noise model by adding +5 dB to the assumed sound power level value. The noise level of the turbine was assumed to be 85 dB(A). This assumption is based on a scenario in which the turbine is operated without separate acoustic lining inside a hall with walls made of sound-reflecting concrete elements. The noise level of the turbine hall fans and the ventilation open- ings was assumed to be 75 dB(A) including the effect of fan-specific silencers.
Noise modeling was carried out separately for industrial noise and road traffic noise in accordance with the Ministry of the Environment noise modeling guidelines (Ympäristömi- nisteriö 2007) and the calculation results were compared with the guideline values for each noise source group.
7.9.3 Construction phase impacts
According to the results of noise modeling, the average daytime sound level LAeq in the recreational residence sites located outside the plant area on the Hanhikivi headland will be approximately 40 dB(A) during the noisiest phase of construction. This value falls well below the 45 dB(A) guide- line value for recreational residence areas. The noise may occasionally be impulsive, in which case the noise level may momentarily exceed 40 dB(A). (Figure 7-32)
The noise level in the nearest nature conservation areas (the meadow in the northwestern part of the Hanhikivi headland and the Siikalahti seashore meadow) may, accord- ing to the modeling results, be approximately 50–53 dB(A). This value exceeds the 45 dB(A) daytime guideline value for nature conservation areas. Since these nature conserva- tion areas are not regularly used for observation of nature or hiking, the guideline values are not considered to apply to these areas. The impacts on the nature conservation areas and the birdlife in the area are assessed in Section 7.6.6.
The areas affected by noise at 50 and 55 dB(A) gener- ated by traffic during the most active period of construc- tion period will be rather limited, and no residences will fall within their scope. The 45 dB(A) noise zone created by daytime (7 a.m. – 10 p.m.) traffic noise will extend to the distance of slightly under 250 meters from the road on both sides of the road (Figure 7-33). At the nearest residential
Figure 7-32. The industrial noise dispersion map for the most active period of construction. The black arrow indicates the nearest residence.
170 7 Assessment methods, the present state of the environment and the assessed environmental impacts
buildings, the noise level will fall well below the 55 dB(A) guideline value for residential areas.
The new road leading to the power plant will run through the Hietakarinlahti–Takaranta FINIBA area at its most narrow point. The Takaranta nature conservation area (the Takaranta seashore meadow and sand dune) will extend to the north from the road. The 45 dB(A) noise zone will extend a short distance inside these nature areas. The use of the areas for observation of nature or hiking is rather limited and mainly occurs close to the shoreline where the noise impact is not significant. The impacts on the nature conservation areas are assessed in Section 7.6.6.
According to the modeling results, the contributory impact of night-time road traffic noise will remain small during the construction phase (Figure 7-34). The 45 dB(A) noise zone will extend to the distance of approximately 65 meters from the centerline of the road. It will not extend to any residential site. Small parts of the nature conservation area and the important birdlife area will be enclosed within this noise zone.
7.9.4 Operation phase impacts
During the operation of the nuclear power plant, the direc- tion of the most significant noise sources will be to the north as well as to the southeast and northwest. Consequently, the impact on the recreational residence sites located to the south
of the plant will remain small. According to the results of noise modeling (Figure 7-35), the average noise level LAeq in recreational residence sites will be under 30 dB(A), which falls well below the daytime and night-time guideline values of 45 dB(A) and 40 dB(A), respectively. In the nearest nature conser- vation areas, the maximum noise level will be 35–40 dB(A).
The figures 7-36 and 7-37 show modeling results based on the daytime and night-time road traffic noise calcula- tions for the operation phase. According to the modeling results, the 40 dB(A) noise zone caused by traffic to and from the plant will extend to the distance of approximately 100 meters from the road to both sides of the road in the daytime. Correspondingly, the 45 dB(A) zone will extend to the distance of approximately 60 meters. The noise level will be lower in the night time. In the night time, the 40 dB(A) zone will extend to the distance of approximately 50 meters from the road. At the nearest residential buildings, the noise level will fall below the daytime and night-time guideline values of 55 dB(A) and 50 dB(A), respectively.
In the daytime, the 45dB(A) noise zone will extend a short distance inside the nature conservation area (the Takaranta seashore meadow and sand dune), the boundary of which is located near the road, and the important birdlife area (Hieta- karinlahti) located to the south of the road. In the night time, the noise zone will be smaller in size. The areas used for observation of nature or hiking is rather limited and mainly
Figure 7-33. The road traffic noise dispersion map for hours between 7 a.m. and 10 p.m. during the construction phase. The black arrow indicates the nearest residence.
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