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g. ENVIRONMENTAL REPORT Mitigation Wetland losses would be mitigated following U.S. Army Corps of Engineers (USACE) and Oregon Division of State Lands (DSL) guidance, and could involve direct or indirect mitigation. Direct mitigation includes options such as creating replacement wetlands on site or off site, or preserving existing wetlands in the project area. Indirect mitigation activities include purchasing "credits" from a wetland mitigation bank (credits are used to preserve the wetland area at which the bank is established), or conserving other wetland areas. 9.4.4 Air 0uality, Odor, and Noise Compared to System Alternative 1, System Alternative 5 will have a beneficial impact on odor. However, System Alternative 5 will result in temporary, negative impacts to air quality and noise during the construction period. Because of increased treatment capacity, air quality and noise impacts m~der System Alternative 5 are expected to remain essentially unchanged during the operational period from the impacts described under System Alternative 1. In general, the proposed changes will improve odor control by capturing more fugitive odors and using odor-reducing technologies. Construction Period Odor. Odor emissions during construction are not anticipated to change. Construction work on expansion to the liquids processes will not affect the odor control processes. Air Ouallly. Air quality impacts from engine and dust emissions would occur during the construction period. However, these emissions would be temporary and limited to hours when construction activities occur. NOiSO. Noise impacts to nearby residential neighborhoods and commercial areas from construction traffic, engines, and construction activities would occur during the construction period. However, these impacts would be temporary and limited to hours when construction activities occur. Operational Period Odor. The proposed changes to the WPCF will increase the capacity of the wet weather treatment processes. Changes to wet weather processes will have minimal impacts on odor because odor emissions are largely driven by dry weather conditions such as low flows and high temperatures. However, modifications to the system will improve odor control during dry weather conditions. Proposed changes involve increasing the odor control by covering existing and new process areas. Proposed odor control technologies will also improve the efficiency of the odor control system. Using bio-scrubbers will greatly improve odor control because of the increased odor reduction and the increase in mixing/dilution capacity of the bio-scrubber tower. MWMC_9.0_REV14.DOC 9-13