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Cheryl Signs, P.E.
<br />Durham Combined SWSP
<br />April 15, 2013
<br />Computation of evaporation from the 1 -acre pond was reduced during the ice covered period. You
<br />have assumed the ice covered period to occur during the months of January, February and December,
<br />based on the average temperatures of 27.0 °F for January, 30.8° for February and 28.8 °F for
<br />December; taken from the Longmont weather station. However, for the purpose of this SWSP, the
<br />Applicant shall replace the net evaporation depletions from the exposed ground water surface area that
<br />may occur during the assumed ice covered period (the months of January, February and December) for
<br />any time that the pit is not completely covered by ice. Computation of the net evaporation during any
<br />time that the 1 -acre pond is not completely covered by ice shall be determined as the pro -rata amount
<br />of the monthly gross evaporation rate distribution amount identified in the State Engineer's General
<br />Guidelines for Substitute Supply Plans for Sand and Gravel Pits, subtracting the pro -rata amount of the
<br />effective precipitation for that period.
<br />Western Sugar Pit
<br />This combined SWSP now covers depletions associated with VCI's Western Sugar Pit. You have
<br />provided a monthly breakdown of the annual depletions made up of 37.84 acre -feet of net evaporative loss
<br />(from 15 acres of exposed ground water), 17.07 acre -feet of water lost with the mined product (which
<br />represents 580,000 tons of mined product), and 2.80 acre -feet of water used for dust control.
<br />Gross evaporation is estimated to be 42.12 inches per year. With an annual effective
<br />precipitation amount of 9.99 inches per year the net annual evaporation is estimated to be
<br />approximately 2.68 acre -feet per acre (32.13 inches). Computation of evaporation under this SWSP
<br />was also reduced during the ice covered period. You have assumed the ice covered period to occur
<br />during the months of January and December, based on the average temperatures of 26.0 °F for January
<br />and 27.4 °F for December; taken from the Greeley weather station (053533). However, for the purpose
<br />of this SWSP, the Applicant shall replace the net evaporation depletions from the exposed ground
<br />water surface area that may occur during the assumed ice covered period (the months of January and
<br />December) for any time that the pit is not completely covered by ice.
<br />Computation of the net evaporation during any time that the pond is not completely covered by
<br />ice -shall be determined as the pro -rata amount of the monthly gross evaporation rate distribution
<br />amount identified in the State Engineer's General Guidelines for Substitute Supply Plans for Sand and
<br />Gravel Pits, subtracting the pro -rata amount of the effective precipitation for that period.
<br />Lagged Depletions
<br />The monthly depletions to the river were lagged from the pit site using the AWAS program
<br />developed by the IDS Group at Colorado State University. The parameters used in the model are as
<br />follows:
<br />*Based on the USGS Water Supply Paper 1662D
<br />Page 3
<br />The analysis took the depletions to a steady state condition. Therefore the lagged depletions
<br />equal the consumptive use on an annual basis at a monthly rate as shown in Table 11. In total, this
<br />SWSP is required to replace 125.62 acre -feet per year.
<br />Replacement
<br />The proposed source of replacement for this pit is 48.7 acre -feet per year (93.18 acre -feet of
<br />headgate deliveries and 44.5 acre -feet of return flow obligations) of historic stream depletions from the dry-
<br />Distance to river
<br />Aquifer Boudary
<br />Transmissivity
<br />Specific Yield
<br />(X), ft
<br />(W), ft
<br />(T), gpd /ft
<br />Durham Pit
<br />1,100
<br />2,600
<br />100,000
<br />0.2
<br />Feit Well
<br />1,100
<br />2,600
<br />100,000
<br />0.2
<br />Dakolios Pit
<br />550
<br />3,500
<br />100,000
<br />0.2
<br />Western Sugar Pit
<br />1,350
<br />2,600
<br />100,000
<br />0.28*
<br />Cheryl Signs, P.E.
<br />Durham Combined SWSP
<br />April 15, 2013
<br />Computation of evaporation from the 1 -acre pond was reduced during the ice covered period. You
<br />have assumed the ice covered period to occur during the months of January, February and December,
<br />based on the average temperatures of 27.0 °F for January, 30.8° for February and 28.8 °F for
<br />December; taken from the Longmont weather station. However, for the purpose of this SWSP, the
<br />Applicant shall replace the net evaporation depletions from the exposed ground water surface area that
<br />may occur during the assumed ice covered period (the months of January, February and December) for
<br />any time that the pit is not completely covered by ice. Computation of the net evaporation during any
<br />time that the 1 -acre pond is not completely covered by ice shall be determined as the pro -rata amount
<br />of the monthly gross evaporation rate distribution amount identified in the State Engineer's General
<br />Guidelines for Substitute Supply Plans for Sand and Gravel Pits, subtracting the pro -rata amount of the
<br />effective precipitation for that period.
<br />Western Sugar Pit
<br />This combined SWSP now covers depletions associated with VCI's Western Sugar Pit. You have
<br />provided a monthly breakdown of the annual depletions made up of 37.84 acre -feet of net evaporative loss
<br />(from 15 acres of exposed ground water), 17.07 acre -feet of water lost with the mined product (which
<br />represents 580,000 tons of mined product), and 2.80 acre -feet of water used for dust control.
<br />Gross evaporation is estimated to be 42.12 inches per year. With an annual effective
<br />precipitation amount of 9.99 inches per year the net annual evaporation is estimated to be
<br />approximately 2.68 acre -feet per acre (32.13 inches). Computation of evaporation under this SWSP
<br />was also reduced during the ice covered period. You have assumed the ice covered period to occur
<br />during the months of January and December, based on the average temperatures of 26.0 °F for January
<br />and 27.4 °F for December; taken from the Greeley weather station (053533). However, for the purpose
<br />of this SWSP, the Applicant shall replace the net evaporation depletions from the exposed ground
<br />water surface area that may occur during the assumed ice covered period (the months of January and
<br />December) for any time that the pit is not completely covered by ice.
<br />Computation of the net evaporation during any time that the pond is not completely covered by
<br />ice -shall be determined as the pro -rata amount of the monthly gross evaporation rate distribution
<br />amount identified in the State Engineer's General Guidelines for Substitute Supply Plans for Sand and
<br />Gravel Pits, subtracting the pro -rata amount of the effective precipitation for that period.
<br />Lagged Depletions
<br />The monthly depletions to the river were lagged from the pit site using the AWAS program
<br />developed by the IDS Group at Colorado State University. The parameters used in the model are as
<br />follows:
<br />*Based on the USGS Water Supply Paper 1662D
<br />Page 3
<br />The analysis took the depletions to a steady state condition. Therefore the lagged depletions
<br />equal the consumptive use on an annual basis at a monthly rate as shown in Table 11. In total, this
<br />SWSP is required to replace 125.62 acre -feet per year.
<br />Replacement
<br />The proposed source of replacement for this pit is 48.7 acre -feet per year (93.18 acre -feet of
<br />headgate deliveries and 44.5 acre -feet of return flow obligations) of historic stream depletions from the dry-
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