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Tom Hatton Page 2 <br />February 14, 2011 <br />December 31, 1980. The area exposed prior to 1981 is shown on the attached map. The <br />exception to the requirement to replace evaporative depletions for the pre-1981 area is tied to <br />the location identified on the map and may not be applied to other areas of ground water <br />exposure within the gravel pit permit boundary. <br />In accordance with the letter dated April 30, 2010 (copy attached) from the Colorado <br />Division of Reclamation, Mining, and Safety ("DRMS"), all sand and gravel mining operators <br />must comply with the requirements of the Colorado Reclamation Act and the Mineral Rules <br />and Regulations for the protection of water resources. The April 30, 2010 letter from DRMS <br />requires that you provide information to DRMS to demonstrate you can replace long term <br />injurious stream depletions that result from mining related exposure of ground water. The <br />DRMS letter identifies four approaches to satisfy this requirement. If the information you are <br />providing to DRMS is included under the approaches numbered 1 - 3, a copy of that <br />information needs to also be provided to this office (the Division of Water Resources). <br />If the information you are providing to DRMS is pursuant to approach no. 4, you will <br />need to provide additional documentation to this office that specifies what water rights or <br />other permanent water source will be dedicated to the SWSP to assure that all permanent <br />depletions from either an unforeseen abandonment of the site by the Applicant or as a result <br />of long term ground water exposure after completion of mining and reclamation will be <br />replaced so as to prevent injury to other water rights. <br />This information must be provided to this office by April 30, 2011. If the requested <br />information is not provided to the Division of Water Resources, any future SWSP may limit <br />the mining operation so that additional ground water cannot be exposed, beyond that <br />specified in this SWSP. <br />Depletions <br />As mentioned above the total exposed surface area at this site is 42.5 acres of which 36.2 <br />acres of water surface was exposed prior to January 1, 1981. This results in 6.3 acres of exposed <br />surface area that require replacement for evaporation losses. Net evaporative depletions were <br />calculated using a gross annual evaporation of 38 inches from the exposed ground water surface, <br />with a credit of 10.3 inches for effective precipitation. The net depletions of ground water due to <br />evaporation from the 6.3 acres of the Kauffman #1 Pit exposed after December 31, 1980 totals 14.5 <br />acre-feet per year, as shown on the attached Table 1. The total annual consumptive use of water at <br />the site is 17.0 acre-feet, which consists of 14.5 acre-feet of evaporation from the 6.3 acres of <br />exposed pond area and 2.5 acre-feet for dust control (see attached Table 2). The mining operation <br />has continuously dewatered directly back to the Big Thompson River since 1990. Due to the long <br />period of continuous dewatering, you have assumed the dewatering at this site has reached a state <br />of equilibrium with the Big Thompson River and there is no longer a net accretion to the river from <br />the dewatering operation. <br />The monthly depletions to the Big Thompson River were lagged from the pit site using the <br />AWAS program developed by the IDS Group at Colorado State University. The parameters used in <br />the model were an estimated distance from the exposed water surface area to the Big Thompson <br />River (X) of 250 feet, an estimated distance from the site to the no flow aquifer boundary (W, <br />measured perpendicular to the point of impact) of 4,000 feet, an aquifer transmissivity (T) of 50,000 <br />gallons per day per foot, and a specific yield (S) of 0.2. According to the Applicant, the distance