2021-09-22 EMC testimony - (09-19) - Demoruelle, Sandra - DEM July 23, 2021 Correspondence to EPA Attachment A

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Mr. Jelani Shareem Ms. Kate Rao July 23, 2021 The proposed approach will include the following minor changes. 1. Phased capacity implementation: The mechanical treatment approach will allow a phased capacity implementation approach to reduce the initial capital cost. The initial capacity will be sufficient to provide service to the developed parcels within the service area, and a modest amount of growth. The initial WWTP capacity needs will be developed using historic potable water use data from the developed parcels. The WWTP will be designed to be readily expandable to the full capacity as described in the FEA (i.e., 190,000 gallons per day average dry weather flow) when needed to accommodate additional community connection or growth. 2. Preliminary treatment: Preliminary treatment within a headworks will be needed upstream of the mechanical treatment processes, an additional grit removal process that is not required upstream of aerated lagoons. The proposed headworks will have one fewer automatic screen than described in the FEA to compensate for the footprint added by the grit removal process. 3. Secondary treatment: As described above, the preferred MBR process will produce a higher quality effluent than the aerated lagoon/subsurface flow constructed wetland process described in the FEA. A mechanical plant will have a significantly smaller footprint than the aerated lagoon/subsurface flow constructed wetland, requiring less site footprint than one of the aerated lagoons. The tanks will also be shallower than the aerated lagoons, requiring less excavation. The net benefit of the change is significantly reduced risk of construction delays and costs associated with subsurface voids and cultural resources that may be contained within. In addition, it will allow more of the site to be used for effluent disposal purposes. Mechanical treatment technology was evaluated in the PER for the project, which was included in the final EA as an appendix. 4. Effluent disposal: While the method of effluent disposal will remain as slow rate land treatment, the application method and intended vegetation will change. Subsurface drip irrigation will be used to apply water to the existing macadamia nut orchard, rather than grading the site into basins for surface irrigation of native trees. The benefit of this change is significant reduction of the number of macadamia nut trees that will require removal for the project, and significantly less ground disturbance as a result of the reduced need for grading at the site. Preliminary Comparison of Environmental Impact Table 1 is a preliminary comparison of the environmental impacts of the proposed approach compared to the project as defined in the FEA. As shown in the table, the minor project changes are anticipated to result in reduced or similar environmental impacts to the project as defined in the FEA, and no greater impacts. Additional environmental assessment will be required to support a use of prior exemption filing with OEQC. 9