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ENMAX Power Corporation No. 5 Substation Post Construction Comprehensive Sound Level Survey, AUC Decision 26165-D01-2021

Link to Decision Summarized

Compliance


In this decision, the AUC approved a request by ENMAX Power Corporation (“EPC”) for a Class A2 adjustment for the nighttime permissible sound level (“PSL”) at a noise receptor (“R1”) close to the ENMAX No. 5 Substation. The AUC further confirmed that the associated post-construction comprehensive sound level (“CSL”) survey had been conducted as required by Rule 012: Noise Control. The AUC found that the ENMAX No. 5 Substation (the “Substation”) was compliant with Rule 012 and that Condition 5 of Permit and Licence 26133-D01-2020 was satisfied.

Post-Construction CSL Survey

As required by Condition 5 of Permit and Licence 26133-D01-2020 for the Substation, EPC conducted a CSL survey. It conducted the CSL survey at the Bell Block building (“R1”) as this was consistent with the latest noise impact assessment (“NIA”) prepared for the Substation.

To calculate CSL at R1, EPC performed an isolation process to exclude invalid or abnormal data from the measured sound levels. Following a review of the audio recordings, EPC determined that sources from the ENMAX No.5 Substation were inaudible during the CSL survey.

To assess Rule 012 compliance for the Substation, EPC compared measured CSLs to PSLs from the 2010 NIA. The comparison revealed that the measured daytime sound level was within the daytime PSL. However, the nighttime sound level exceeded the unadjusted nighttime PSL.

EPC submitted that the measured CSL exceeded the unadjusted nighttime PSL because the assumed nighttime ambient sound level (“ASL”) was not representative of the actual ASL at R1. EPC noted the assumed ASL did not adequately account for dominant sound sources in the area (e.g., road traffic and rail traffic) and that it was too low to be representative of the ambient sound environment at R1. Because the unadjusted PSL was established with reference to the assumed ASL (i.e., the unadjusted PSL was five dBA greater than the assumed ASL), EPC submitted the unadjusted nighttime PSL was also too low.

Based on the analysis within a traffic noise study prepared for the area surrounding R1, EPC submitted that an A2 adjustment should be applied to the nighttime PSL to account for the urban soundscape effecting R1.

Class A2 Adjustment

Because it was not possible to measure the ASL directly at R1 in the absence of energy-related facilities (i.e., it was not feasible to shut down the Substation for the purposes of collecting noise measurements), EPC used a computer model to predict the noise contribution from the Substation at R1 in the absence of other sources, and then subtracted this value from the measured CSL to estimate the representative ASL.

A comparison indicated that once the PSL was adjusted, the Substation was compliant with Rule 012, because the measured nighttime CSL at R1 (60.3 dBA) was less than the A2-adjusted nighttime PSL (61 dBA)

AUC Findings

The AUC accepted EPC’s CSL survey and the associated results as EPC had met all the requirements of Rule 012 in completing the survey.

The AUC agreed that the assumed nighttime ASL was not representative of the soundscape at R1. Rule 012 stated that A2 adjustments may be applicable in areas where non-energy activity influences the ASL. Accordingly, the AUC determined it was reasonable for EPC to apply for an A2 adjustment.

An A2 adjustment was to be determined based on the representative ASL, which needed to be established without the noise contribution from energy-related facilities. The AUC accepted that it was not feasible to shut down the Substation for the purposes of measuring the ASL at R1 and that EPC therefore had to make use of an alternative method to establish the representative ASL at that receptor.

The AUC also determined that EPC used reasonable methods to determine the representative nighttime ASL at R1 and EPC used procedures required by Rule 012 when establishing an A2 adjustment for R1. The AUC was further satisfied that relevant stakeholders had been consulted as required and that now concerns had been raised. Following Section 4.2 of Rule 012, the AUC found that it was reasonable for EPC to establish the representative ASL at R1 by modelling the noise contribution from the ENMAX No. 5 Substation and then subtracting this modelled contribution from the measured CSL.

The AUC approved the five dBA A2 adjustment proposed by EPC and determined that the applicable nighttime PSL at R1 was 61 dBA.

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