Resolution No. 4793 - Laserfiche WebLink

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MWMC FACILITIES PLAN FIGURE 5.1.3-4 Wet Weather Maximum Week Effluent Concentration Requirements Based on Existing Mass Load Limitations and Projected Flows MWMC Facilities Plan, Eugene-Springfield 50,0 I 190 45.0 Current TS$ Effluent Concentrahon Limit -- -- 175 40.0 Current CBOD Effluent Concentrabon L~mlt _ 1.6 s 160 35.0 l- ~ -145 ~00 ~~ -~ 130 26 3 25.0 ~2g 115 8~ ~ 21.5 20.3 20,0 - 2z.o 19,6 ~ 17,4 18,4 15,0 ~ - ' 85 10,0 .... 66.0 -- __~ 70 620 - 58.1 54 2 ~ 5.0~ ......... ~ 55 2005 2010 2015 2020 2025 ~ear -~ CSOD Concentra~n~ TSS Concen~Jt~ Max Week Wet Weather Flow ~Average Wet Wea~he~ Ammonia The current NPDES permit (issued in 2002) includes a requirement for dry weather nitrification. Current Oregon water quality criteria drove previous reasonable potential findings amd the justification for a dry weather average month and maximum day effluent ammonia concentration limit of 12 milligrams per liter (mg/L) and 22 rog/L, respectively. If Oregon were to adopt EPA's 1999 update of water quality criteria, as recommended by the Triennial Review Policy Advisory Committee, there may be a relaxation of the acute and chronic criteria. However, in the absence of adoption of that criterion, aa~d based on the premise that it will be difficult to relax the current effluent ammonia requirernents, it is assttmed that the current ammonia effluent limitations will be implemented in future permits. The result is that the biological process at Eugene-Springfield will need to be modified to accommodate more sustainable nitrification, and thus de-nitrification will be reqttired to address the alkalinity deficit currently experienced during nitrification. Excess Thermal Load Under the 1996 Oregon Temperature Standard (Oregon Admh-fistrative Rule 34041-0026), the WPCF was required to prepare and implement an approved Temperature Management Platt for the following reasons: 5-8 MWMC_50_REV8 DOC