Agenda - Public Works Committee - 01/16/2018

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November 10, 2017 Page 3 From this data, the PWS number can be identified in the PWS file for each community of interest and used to identify wells listed in the Facility file for the communities of interest. Well data from the Facility file is selected for primary wells only, excluding emergency wells, and a count of the number of wells per community is determined. Screening Criteria The screening process began with data from the Inventory file. CDM Smith added four newfields to the database: Municipal System (yes or blank) Groundwater (yes or blank) Percent Residential by Volume (residential delivered/total delivered) Residential GPCD (residential delivered/population served) Only records for systems that are municipal systems were selected for further screening. The screening also excluded systems that relied on purchased water. Note that the City of Medina has three permit numbers and White Bear Township has two permit numbers. The data, by permit number, were merged for each of these communities. Each municipal system has from 1 to 4 records for the years 2013 to 2016. The values for population served, total delivery volume, and residential delivery volume were averaged across all available years for each municipal system. The percent residential volume and the residential GPCD were calculated from the averages for each system. There are 100 municipal systems that meet the criteria of municipal systems on groundwater. Those that provide wholesale water to other systems were excluded leaving 94 systems as potential communities. (A list of known interconnections among systems is included at the end of this memo.) The data for these 94 systems were sorted by percent residential and residential GPCD to identify communities that best meet the first two selection criteria. The percent residential by volume ranges from 99 percent to 23 percent. The residential GPCD ranges from 124 to 27 GPCD. The second step was to analyze the Monthly water use data. A table was created from the Inventory data that included the permit number and name of the 94 selected systems. This table was used as a lookup table to pull out the monthly water use records for these systems. In the prior analysis using this database with respect to water billing rates, only the data since the year 2000 was used. This same assumption was applied to the current analysis, which reduced the number of records representing water withdrawals by withdrawal point (well) for the 94 systems. The monthly water withdrawal volumes by withdrawal point (well) were summed for each system for each year. This resulted in 17 annual records for most of the systems. For the two systems with less than 17 years of data, both had at least eight years (2009-2016) of data available. The water withdrawals by month were averaged by month across all available years for each system. From these monthly averages, the following data were calculated: