2013-05-30_HYDROLOGY - M1983090 - Laserfiche WebLink

Home Browse Search

Mr. Andy Rodriguez Poudre Pits Aggregate Mine SWSP May 29, 2013 Page 3 with Bestway Concrete and Aggregates as well as submitted pump specifications and data showing the 100 gpm is a more accurate estimate than the previously accepted 500 gpm. Mark Johnson described the recharge operation as occurring simultaneously with dewatering in that the operator would discharge the water into an adjacent, previously mined, cell. Once the cell being recharge exceeded its hydraulic capacity the water would then be diverted directly to the river. This type of a recharge program is projected to occur in 2013. The 2012 SWSP required meters to be installed on all dewatering operations starting April 2012. The operator has confirmed that meters were installed at the Firestein/Tigges site by this deadline. However, the dewatering operation that began in April 2012 at the North la Poudre site did not have meters installed. As a result, it is assumed that April 2012 through December 2012 saw the same 100 gpm projected dewatering rate but no recharge credit is given per condition # 12 of the 2012 SWSP. The operator installed meters at this site by January 2013 and starting January 2013 the actual meter readings are used in the dewatering analysis. For the duration of this SWSP and future approvals, actual monthly meter readings must be used to determine the true dewatering rate, and to determine how much water was recharged versus being directly returned to the river. Dewatering has occurred in different phases at the Firestein/Tigges /Roberts Pit. Dewatering operations at the Firestein Pit occurred from January 1996 through June 2001. With the stated recharge that occurred, the lagged depletions to be replaced in 2013 equal 0.22 acre -feet. Dewatering operations at the Tigges Pit occurred from June 2005 through March 2012. Dewatering operations may begin at the Tigges Pit this year but to be conservative no dewatering is projected in this SWSP. With the stated recharge that occurred, the lagged depletions to be replaced in 2013 equal 8.14 acre -feet. Dewatering operations at the Roberts Pit occurred from July 2001 through June 2006 when the reservoir was lined. With the stated recharge that occurred, the lagged depletions to be replaced in 2013 equal 1.28 acre - feet. Combined, the dewatering operations at the Firestein/Tigges /Roberts Pit have resulted in a lagged depletion of 9.64 acre -feet that must be replaced in 2013. See Table 5b for the monthly distribution of these lagged depletions. Dewatering has occurred in different phases at the North la Poudre and La Poudre Sites. At the North la Poudre Site, dewatering operations occurred from September 2002 through March 2003. Dewatering started up again in May 2012 and lasted through December 2012. Small incidental dewatering has occurred in January and February of 2013 (0.047 acre -feet total) but dewatering is not expected to continue throughout 2013. The 2012 dewatering was not metered and so no recharge credit was given. Instead all dewatering was assumed to be discharged directly to the river creating no lagged accretions. Combining the lagged depletions and net accretions from the stated recharge (prior to 2012), the past dewatering activities will create a net depletion of 37.80 acre -feet during 2013. Dewatering operations at the La Poudre Pit occurred from January 1995 through December 2002. With the stated recharge that occurred, the lagged depletions to be replaced in 2013 equal 0.81 acre -feet. Combined, the dewatering operations at the North la Poudre and La Poudre pits will result in a net depletion of 38.61 acre -feet. See Table 5a for the monthly distribution of these lagged depletions. Table C below sums up the dewatering impacts from the different pits.