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Inc <br />Mr. Thomas A. Schreiner <br />May 16, 2001 <br />Page 2 <br />The following information including flood frequency, water surface crest elevation and discharge <br />data, is from Engineering Professionals, Inc.'s Floodploin Lformation Report. North St. Vrain <br />orrd St. Yrain Creeks, Boulder Co~uery, Colorado. Information for the 2-, 5- and 25-year <br />frequency flood events was not available. A hydraulic study for the proposed mining area will be <br />completed in conjunction with the FHDP. <br /> 10-Year Flood 50-Year Flood 100-Year Flood 500-Year Flood <br />Stream Crest Peak Crest Peak Crest Peak Crest Peak <br />Bed Elev. Discharge Elev. Discharge Elev. Discharge Elev. Discharge <br />Elevation (cfs) (cfs) (cfs) (cfs) <br />5050.70 5054.08 3090 5055.64 6807 5056.11 9536 5057.28 19716 <br />2. Tree preservation plan: <br />The applicant has been monitoring the groundwater levels monthly for approximately four years. <br />Certified Engineering Geologist Tom Hesemann, R.G., C.E.G. and Ecoplanner Kaia Anderson <br />strategically sited twelve monitoring wells to obtain groundwater information. Please refer to the <br />attached map for the approximate locations of the wells. This data will be correlated with the <br />flows in the river to establish a relationship between the groundwater and the river stages. If, <br />during mining, the groundwater falls more than 1 to 2 feet from baseline levels the applicant will <br />flood irrigate the trees as necessary to provide supplemental water. <br />Aggregate has committed to installing 250 trees and 650 shrubs as part of the reclamation plan. <br />This will more than replace any tree mortality that results from the mining operation. Please note <br />that trees currently die and replant as part of the normal life cycle of the riparian corridor. <br />3. Please refer to the Mining Plan Map for the locations of the settling ponds and discharge points <br />and the cross section of the pit excavation and dewatering trench. <br />4. The operator anticipates that the maximum volume of overburden to be stockpiled a[ any one <br />time will be 150,000 cubic yards. <br />The operator is willing to be bonded for a maximum disturbance of both Phases 5 and 6 and the <br />processing site. <br />