Item A - PH on MWMC/Metro Plan - Laserfiche WebLink

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Regarding Commissioner. Mordson'S question on What frequency does the historical data bump up against the dry season 49 mgd and wet season 75 mgd, Mr. Noesen said that the information was mailed to the Commissioners earlier in the week. A statistical analysis was done to look at what percent of the time the historical flows were above the 49 mgd rating and 43.8 is the current utilized capacity in the SDC methodologY. When you 10ok at that, 2.1% of the time the historical data was above the 49 mgd and looking at the number used for the current utilized capacity, 12.5% of the time historical data was above. Looking at the wet season; which is 75 mgd, 21.1 % of the time the historical data was above that value. Com~ on CBOD (carbonaceous biochemical oxygen demand), Mr. Noesen said this r of fluid strength coming into the treatment facility. It does not capture ammonia, another parameter pollutant that is now in the NPDES permit and which does use bit of existing and available capacity. Looking at Total Suspends Solids capacity is 2.5% of the time of the historical period is greater than the rated the time in the current rated capacity. Commissioner Inge asked if "cOntrol'' tnt would never have Mr. 'Noesen said the draft Facilities Plan is not 3o that the never exceedances. This is a topic being discussed with percent of exceedances would be acceptable. Commissioner Meyer larding fi. e standard in Oregon for summer is one in 10-year storm, and if the storrr than of ;ry 10 years, it is considered an unusual condition. In the winter, it is one standard in the Water Regulations for the State. Mr. Noesen agf a letter stating that the capacity of the based on maximum flows and not based on Mr. Ruffler ded that ti' form the basis for the permit limit and established at by are based on Federal guidance that basically targets a one chronic toxicity criteria. The Federal standards an eve three years, which equates to .09% rate on to the ~ments submitted, Mr. Noesen indicated that one letter was an en. ment of the SDCs. The second letter had a series of issues and questic ed. Mr. address some of those issues brought up in the letter from the 3uilders (cc ~ letter and comments attached). He said a key issue brought up by HBA was Lring the Master Plan capacity assessment to the capacity assessment associated witt Facilities Plan and SDC methodology. Other issues HB^ mentioned were and the alternatives evaluation and what technologies_were looked at. Regarding the comparison of the 1997 Master Plan and the 2004 Facilities Plan, Mr. Noesen said there are significant differences in the two analyses. For dry season flow, there is an 11% difference in population as well as a 9% decrease in per capita values that go into projecting flows. Mr. Noesen also commented on the use of maximum month instead of average in assessing capacity. The DEQ letter (attached) states that maximum flows (monthly, weekly, and daily) need to be looked at when assessing capacity, which is what has been done in the 2004 4-58