Wind Power Plant Application –Noise Impact Assessment – Rule 12 – Class C2 Adjustment
In this decision, the AUC considered the following applications:
(a) facility applications from Power Renewable Energy Corporation (“PRE”):
(i) to construct and operate the 120-megawatt Jenner Wind Power Plant (the “Wind Power Plant Application”), and
(ii) to construct and operate the Halsbury 306S Substation and transmission line 949L;
(b) a needs identification document application from the Alberta Electric System Operator (the “AESO NID Application”); and
(c) a facility application from AltaLink Management Ltd. to alter the Jenner 275S Substation.
AESO NID Application
The AUC found that the AESO’s assessment of the need to be correct and that approval of the proposed developments, including the Preferred Route of transmission line 949L, was in the public interest, having regard to the social and economic effects of the project and its effect on the environment.
The AUC approved the AESO NID Application.
Jenner Wind Power Plant Noise Impacts
PRE retained RWDI Consulting Engineers & Scientists (“RWDI”) to prepare a noise impact assessment (“NIA”) for the project.
The AUC noted that this proceeding was the first time it considered an application utilizing a Class C2 adjustment (to address noise issues related to wind masking).
The AUC explained that AUC Rule 012: Noise Control (“Rule 012”) allows project proponents to apply for a Class C2 adjustment to the permissible sound level (“PSL”) at a residence if the proponent can demonstrate that the ambient wind sound level at a particular dwelling is higher than an assumed ambient sound level. In other words, the Class C2 adjustment accounts for “wind masking,” which can occur when the sound of the wind at a residence “drowns out” the sound of the wind turbine. The maximum available Class C2 adjustment under Rule 012 is 10 dBA.
The AUC went on to explain that to qualify for a Class C2 adjustment, the project proponent must complete an ambient wind sound level survey to determine the difference between the ambient sound level set out in Rule 012 and the measured ambient sound level.
The AUC first assessed the NIA without the requested Class C2 adjustment. The AUC found that:
• the NIA met the requirements of Rule 012; and
• the cumulative sound level predicted by the NIA met the daytime and nighttime PSL at all receptor locations assessed.
The AUC noted that PRE’s rationale for applying for a Class C2 adjustment was driven primarily by concerns about meeting the nighttime PSL when conducting post-construction noise monitoring. The AUC found that:
• PRE demonstrated that the wind in the area would likely result in an ambient sound level greater than the assumed ambient sound level (i.e., wind masking) at receptors R3 and R7; and
• the methodology used to conduct the ambient wind sound level survey in aid of its requested Class C2 adjustment was acceptable and met the requirements of Rule 012.
However, the AUC did not accept the NIA’s conclusion that a Class C2 adjustment allows for a broad adjustment to the nighttime PSL. The AUC found that Rule 012 provides for a Class C2 adjustment to the PSL for a specific wind speed and wind direction when that wind speed and direction is present near the applicable dwelling (i.e. receptor). The AUC noted that in this case, the NIA was unable to collect sufficient data for many of the wind directions. In particular, the NIA did not collect sufficient data for the wind direction relative to the nearest turbine to receptor R4, for which PRE was applying for a Class C2 adjustment.
The AUC found that:
(a) because PRE had not applied for a Class C2 adjustment at receptor R7, it could not apply for a Class C2 adjustment at receptor R4 based on measurements at receptor R7; and
(b) the clause regarding dwellings with acoustically similar environments was intended to refer to groupings of houses, such as receptors R2 and R3, and was not meant to allow for measurements at two or more receptors that are not grouped or in immediate proximity to each other.
For those reasons, and having regard for the fact that the project would be in compliance with the PSL without a Class C2 adjustment at receptor R4, the AUC denied the request for the Class C2 adjustment at receptor R4.
With respect to the applied for C2 adjustment at Receptor R3, the AUC found that the receptors R2 and R3 were within sufficiently close proximity to each other and acoustically similar. The AUC therefore approved the applied for Class C2 adjustment for those receptors of +4dBA for a nighttime PSL of 44 dBA for a wind direction of 150 degrees, +/- 15 degrees at a wind speed of 4 m/s or higher for receptors R2 and R3.
Wind Power Plant Approval
With respect to the other aspects of the Wind Power Plant Application, the AUC found that:
(a) the technical, siting, environmental and noise requirements for the power plant comply with the requirements prescribed in Rule 007; and
(b) the participant involvement program undertaken by PRE was satisfactory and met the requirements of Rule 007.
The AUC concluded that the adverse effects of the wind power plant, including noise and impacts to the environment, could be mitigated to an acceptable degree. The AUC therefore considered the project to be in the public interest in accordance with Section 17 of the Alberta Utilities Commission Act.
