2013-03-12_HYDROLOGY - M1977439 - Laserfiche WebLink

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Site Name T X W S Home Office Pit 160,000 1,000 6,500 0.2 Overland Ponds Pit 160,000 2,000 3,000 0.2 North Taft Hill Expansion Site Pit 160,000 1,600 2,900 0.2 Mr. Heintz and Ms. Wynne Upper Poudre Combined SWSP March 12, 2013 — AWAS LAGGING PARAMETERS Page 3 Substitute Supply Plans for Sand and Gravel Pits, subtracting the pro -rata amount of the effective precipitation for that period. Pursuant to § 37- 90- 137(11)(b), C.R.S. and 2009CW49, a gravel pit operator or property owner does not need to replace depletions that occur due to evaporation from ground water exposed prior to January 1, 1981 (Pre -81) as a.result of open mining of sand and gravel, regardless of whether mining continued after December 31, 1980 (Post -80). This SWSP recognizes a total of 100.0 acres at the Home Office Pit as being a Pre -81 exposure. Of the 100, 22.1 acres are within the Partners Lamb A pond as reflected in the Partner's SWSP for their portion of the Home Office Pit. Therefore, for MMM's SWSP 77.9 acres are recognized as Pre -81. The Pre -81 exposure locations have previously been set and are not allowed to be relocated to other areas of ground water exposure within the gravel pit boundary. There are no recognized pre -81 areas at the Overland Ponds or the North Taft Hill expansion site. Locations for the pre -81 areas are shown on Figure 1. A stream depletion model using the Glover method was used to calculate the lagged depletions to the Cache La Poudre River. The alluvial aquifer model uses four aquifer input parameters for each site as follows: 1) X- distance from well to river, 2) W- distance from the aquifer boundary through the well to the river channel, 3) T- transmissivity of the alluvial aquifer (in gallons per foot/day) between the well and the river, and 4) S- specific yield - 0.2 was used for all wells. The following parameters for each site listed in the table below were used in the model: As of January 2011 the Partners are augmenting their portion (125.5 acres in Treiber A & B, and Lamb B & C lakes) assuming a steady state condition, thereby accounting for lagged depletions from past evaporation. Therefore, these areas were not included in the determination of lagged depletions to be replaced through this SWSP. The estimated consumptive use and lagged stream depletions due to evaporation and operational losses are 113.13 acre -feet as shown on the attached Table 5. The three sites are assumed to have been continuously dewatered and to be in a steady state condition where dewatering accretions equal the lagged depletions. Lafarge previously estimated that the sites are dewatered at a rate of 800 to 1,000 gpm for approximately 12 hours per day. All dewatering is directed to the Overland Ponds site where a single pump then directs water to the river. During 2012, MMM installed a totalizing flow meter on this pump and will report monthly meter readings on submitted accounting. As long as the dewatering operations are constant the site may continue to operate assuming steady state conditions. Once dewatering ceases or is reduced in its flow, lagged depletions will immediately hit the river. At least three years prior to a modification in dewatering operations, the Applicant must provide a plan showing how lagged post - pumping depletions will be replaced in the proper time and amount. The post pumping analysis shall use the meter data from the dewatering totalizing flow meter. Replacement Replacements for this combined plan will come from credits associated with eleven (11) Taylor and Gill Ditch shares. MMM owns a total of 15.175 shares of the Taylor and Gill Ditch. Under previous SWSPs 5.75 Taylor and Gill Ditch shares were used for replacement purposes and the remaining 9.425 were leased for irrigation. In the event that the yield from the 11 shares is less than