Agenda - Public Works Committee - 01/16/2018

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November 10, 2017 Page 4 The maximum month volume The winter average volume (average of October – April) The ratio of maximum month volume to the winter average volume Note that these calculations of the peak month ratio are based on a longer time period (2000-2016) than the time period (2013-2016) used in the computation of the percent residential volume and residential GPCD. A comparison calculation of the peak month ratios was conducted using only the 2013-2016 period and found that in general the ratios were lower. Further investigation revealed that many of the system peak month volumes occurred during a period from about 2003 to 2008. Therefore, the peak month ratios from the 17-year data were used in the analysis. The peak month to winter ratio of each system was matched to the summary data from the Inventory file by permit number. This information allows the 94 communities to be sorted by the peak month to winter ratio with respect to the third selection criteria. One system (the City of Lexington in Anoka County with an average population served of 2,062) has a peak ratio of 68. Review of the monthly withdrawal data for this system indicates that Lexington purchases water from Blaine and only uses its well to supplement water for higher summer demand. Thus, the winter average used to calculate the ratio was extremely low. With the exception of this one system, the peak ratios of the systems range from 4.1 to 1.3. The third step in the process was to identify the future population growth percentage for the 94 systems. The population data is by municipality rather than by water system. The data are organized by county and then municipality. Some municipalities are partially listed in two counties. For these municipalities, the two populations were combined to represent the entire municipality. The municipality names in the population data were matched with the municipal water system names from the MPARS data. The population values for 2010 and 2040 were used to calculate the population growth for each of the communities. The growth ranged from 59,032 (St. Paul Regional Services) to -126 (City of Lakeland). The fourth step in the process was to approximate the number of new wells each community would need by 2040. The MDH well data was used to derive the current number of active wells (excluding emergency wells). The population served by each community was divided by the number of wells to estimate the ratio of population served per well. The change in population from 2010 to 2040 was divided by this ratio to estimate the number of future new wells needed for each community. This assumes that the ratio of population per well remains the same, and that all new water supply will be provided from new wells. The resulting estimate of new wells needed was rounded to the nearest integer. Almost a third (30) of the communities do not appear to need new wells in the future. Two communities (Lake Elmo and Dayton) may need as many as 9 new wells by 2040 given their current ratio of population per well and projected population growth.