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Mr. Mike Grochala <br />January 21, 2016 <br />Page 4 <br />leads to a weekly irrigation depth of 0.84 inches, resulting in a total water depth of 1.6 inches <br />applied to the turf on a weekly basis, including precipitation. Studies conducted by the <br />University of Minnesota indicate that this irrigation rate is likely slightly more than necessary <br />given the soils and precipitation. A small overestimation of the irrigation rate is desired so that <br />the model is conservative. <br />Option 1: Irrigating Public Spaces with Storm Water <br />Option 1 resulted in a daily irrigation rate of 42,000 gallons on days in which irrigation occurred <br />(days in which precipitation was less than 1 /7 -inch). The water balance model indicates that the <br />storage can sufficiently supply water for irrigation of the public spaces with minimal effect on <br />storage levels. Evaporation and irrigation combined resulted in maximum storage level <br />fluctuation of 36.8 million gallons (MG), or 4 feet in elevation change. Option 1 is feasible in <br />terms of water supply. <br />Option 2: Irrigating Public Spaces and Townhomes with Storm Water <br />Option 2 resulted in a daily irrigation rate of 88,000 gallons on days in which irrigation occurred. <br />The water balance model indicates that the storage can sufficiently supply water for irrigation of <br />the public spaces and townhome properties with minimal effect on storage levels. Evaporation <br />and irrigation combined resulted in maximum storage level fluctuation of 37.0 MG, or 4 feet in <br />elevation change. Option 2 is feasible in terms of water supply. <br />Option 3: Irrigating all of the Mattamy Development with Storm Water <br />Option 3 resulted in a daily irrigation rate of 547,000 gallons. The storage cannot supply enough <br />irrigation water to support this option. The model showed that storage levels will reach <br />approximately two feet in depth during the summer if irrigating at this rate. A protective <br />elevation can be set, such that at a certain storage depth the irrigation system does not run. <br />Depending on the elevation chosen, the system will turn off for different time ranges. If, for <br />example, the protective elevation is 896 feet (corresponding two an eleven foot depth), the <br />system would run off of potable water an average of 22 days per summer. Given the system and <br />operating cost, Option 3 is not feasible in terms of water supply. <br />Please contact me at (763) 287-8319 with any questions. <br />Sincerely, <br />WSB & Associates, Inc. <br />Erin Heydinger <br />