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SYSTEM DEVELOPMENT CHARGE METHODOLOGY <br /> <br />Current average flow (presented as DSMM) = ((129 x 217,737 x 1.5)/1,000,000) + 1.7i = 43.8 <br /> Where: <br /> <br /> 129 is the average gallons per capita per day (gpcd) of the dry season values from <br /> 1990 to 2002 <br /> <br /> - 217,737 is the population served in 2002 <br /> <br /> - 1.5 is the selected peaking factor to convert average dry season flow to maximum <br /> month dry season flow (based on 1990 to 2002 data) <br /> <br /> - 1.7i is the current industrial flow in mgd <br /> <br />The available capacity in terms of average flow is 5.2 mgd (49 - 43.8). <br /> <br />The projected 2025 average flow is determined as follows: <br /> <br />Projected 2025 average flow (presented DSMM) = ((129 x 297,585 x 1.5)/1,000,000) + 1.7 = <br />59.3 mgd <br /> <br /> Where: <br /> <br /> - 129 is the average gpcd of the dry season values from 1990 to 2002 <br /> <br /> - 297,585 is the proiected population to be served in 2025 <br /> <br /> - 1.5 is the selected peaking factor to convert average dry season flow to maximum <br /> month dry season flow (based on 1990 to 2002 data) <br /> <br /> 1.7 is the projected industrial flow in mgd (it has been assumed that the <br /> industrial flow will remain constant over the study period) <br /> <br /> The total required capacity to meet the needs of growth in terms of average flow is 15.5 mgd <br /> (59.3 - 43.8). <br /> <br /> Peak Flow <br /> A summary of the peak flow breakdown is presented in Table C-2. The existing capacity in <br /> terms of peak flow is not defined in the NPDES permit, but the plant was originally <br /> designed for a peak flow of 175 mgd, and therefore that is defined as the existing capacity. <br /> MWMC does not currently have the collection and treatment capabilities to accommodate <br /> the existing peak flow (which is greater than 175 mgd), and therefore the current peak flow <br /> loading (required capacity) cannot be explicitly measured at the WPCF. Using a computer <br /> model of the collection system MWMC is able to estimate the current peak flow. DEQ <br /> defines the peak flow as the peak hour or peak instantaneous flow that occurs during the <br /> 5-year, 24-hour storm (3.9 inches of rainfall). Under these rainfall conditions, the model <br /> predicts a current flow of 264 mgd. Therefore, there is no available capacity in terms of peak <br /> flow. Since the current average flow is 43.8 mgd, the current wet season I/I is 220.2 mgd <br /> (264 less 43.8). <br /> <br /> Using the projected future 2025 population and land use, the model predicts peak flows of <br /> 294 mgd without I/I reduction efforts outlined in the 2000 WWFMP and 277 mgd with I/I <br /> <br /> SEA31003271388(DG).DOC/041040034 <br /> <br /> <br />