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Blade Runner: How to Measure Noise at Wind Facilities

In Mingo v. Morrow County, __ Or LUBA __ (LUBA Nos. 2011-014, 2011-016, and 2011-017, June 2011), LUBA considered the Department of Environmental Quality’s (DEQ) noise control regulations in OAR chapter 340, division 35.  The case involved Morrow County’s conditional use approval for a wind energy facility in 2005 which required that the facility comply with DEQ’s noise control regulations.

 The facility, Willow Creek Wind Energy Center, began operations in 2008.  Before and after the center commenced operation, noise complaints were filed with the county.  The planning department initiated a public process before the planning commission and a battle of the experts began regarding sound level increases at four properties near the facility. Ultimately, the County Court decided that the Williams’ residence suffered from excessive noise impacts, but none of the other three residences were affected.  The parties appealed to LUBA.  OAR 340-035-0035(1)(b)(B)(i) provides that wind facilities may not “increase the ambient statistical noise levels, L10 [six minutes in one hour] or L50 [30 minutes in one hour], by more that 10 dBA (decibels) in any one hour.”  For wind energy facilities, the allowable 10 dBA increase can be measured in two ways:

The increase in ambient statistical noise levels is based on an assumed background L50 ambient noise level of 26 dBA or the actual ambient background level.  The person owning the facility may conduct measurements to determine the actual ambient L10 and L50 background level.”  OAR 340-035-0035(1)(b)(B)(iii)(I). 

 In Mingo, LUBA was only concerned with the L50 ambient statistical noise level.*  Under the OAR 340-035-0035(1)(b)(B)(iii)(III), the L50 ambient noise level with the wind turbines in use must not exceed 36 dBA (26 + 10), if the assumed background ambient noise level of 26 dBA is used.  Alternatively, the rule explains that the ambient noise level with the wind turbines must not exceed the sum of 10 dBA and the actual L50 ambient level without the turbines.

One hurdle for LUBA in making its analysis was that the regulations were drafted and adopted by DEQ and the rule assumes that DEQ would administer and enforce the rule.  However, since 1991 there has been no DEQ funding to administer and enforce the noise rule, and DEQ has not administered or enforced OAR chapter 340, division 35 for the past 20 years.  Nonetheless, Morrow County incorporated and adopted OAR chapter 340, division 35 as its noise regulation, and administration and therefore, LUBA found that enforcement responsibilities fell to the county.

Mingo and others complained to the county that Invenergy, owner of the wind facility, was in violation of the noise regulation.  In fashioning a remedy for the violation (and potential violations that could be found on remand), the question arose whether Invenergy had to elect to choose one method of measuring the L50 noise levels

1) elect to apply the 36 dBA scale; or

2) measure the actual noise level and add 10 dBA.

According to the petitioners, Invenergy would have to choose one method for all testing.  However, LUBA looked to the language of the rule and found no such limitation imposed.  Instead LUBA found that Invenergy could use either the measured, actual background ambient noise level or the assumed 26 dBA background ambient noise level at individual measurement points when seeking approval for the proposal, and when required to prove that its operating facilities complies with the rule’s requirement that the wind energy facility increase background ambient noise levels by no more than 10 dBA. 

 On remand, the battle of the experts will continue.

 * LUBA did not address the inconsistency in OAR 340-035-0035(1)(b)(B)(i) and (iii)(I) switch from “L10 or L50” to “L10 and L50.”  However, LUBA did note that the L10 typically represents the loudest and shortest noise events occurring in the environment, such as nearby car and truck pass-bys or aircraft flyovers.  Since the L10 compliance was not challenged LUBA had no reason to resolve the language shift.

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