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<br />TETRA TECH Page 2 of 3 <br />Mr. Peter Hays <br />June 6, 2011 <br />Poudre River adjacent to this site results in erosive headcutting on one bank of the river or the other. <br />So, using the UDFCD's Technical Review Guidelines for Gravel Mining Activities within or Adjacent to <br />100-year Floodplains as a guideline, Tetra Tech advised Lafarge on where erosive headcutting is on <br />the pit side of the river. In these areas, the mine limits will be set back 200 feet from the top of bank. <br />Where the erosion forces are predominately on the opposite bank of the river, erosion is much less of <br />a concern and the setback will remain 100 feet from the top of bank. In addition we recommended <br />inflow and outflow spillways be installed in conjunction with site reclamation to control the manner in <br />which high river flows impact the site. The recommendations made by Tetra Tech are in accordance <br />with the best practices per Urban Drainage and Flood Control District (UDFCD) guidelines and <br />Lafarge agreed to modify the mining and reclamation plans as recommended by Tetra Tech. <br />Attached are updated versions of Exhibits C, D, E and F (Attachments A-D) to reflect changes <br />associated with holding a larger mining setback from the river in some areas and constructing the <br />inflow and outflow structures at the time of reclamation. <br />17. Please clarify if the conveyor structure foundation at the bike path conveyor crossing will be anchored <br />to the ground with rebar. <br />As shown on the details for the bikepath conveyor crossing, the conveyor structure foundations will <br />be recessed into the ground which will essentially anchors the above ground conveyor bridge <br />structure to the ground; these foundations will not need to be further anchored to the ground with <br />rebar. <br />19. The Applicant did not revise the seed mix for topsoil/overburden piles listed in Exhibit C to match <br />Exhibit E and F. Please clarify if the Applicant intended to revise the seed mix to correspond with the <br />seed mixture for Upland Areas. <br />The seed mix on Exhibit C (Attachment A) has been changed to match the seed mixture for upland <br />areas as listed in Exhibits E and F. <br />23. Please provide the Division with a signed and notarized letter from Mr. and Mrs. Iverson stating they <br />are aware of and accept the potential vegetation and ground water well impacts related to mine <br />dewatering on their property. <br />Attached please find a notarized letter from Mr. and Mrs. Iverson (Attachment Q. <br />31. Comment from First Adequacy Review letter: <br />The Division will estimate the cost to reclaim the site based on the information submitted once the <br />Applicant addresses the concerns noted in this letter. <br />In addition, the Division will include costs to comply with the Office of the State Engineers <br />requirement for out-of-priority groundwater depletions. The reclamation plan proposes 44.1 acres of <br />open ground water will remain after the site is reclaimed. Lafarge or the landowner must obtain a <br />court approved augmentation plan from the Office of the State Engineer. The Division is required to <br />set the financial warranty at a level which reflects the actual current cost of fulfilling the conditions of <br />the Reclamation Plan per Rule 4.2.1(1). Therefore, without an augmentation plan in place the <br />financial warranty must be set at an amount which accounts for the exposed groundwater. The <br />Division has identified several options for determining the amount of the financial warranty. The <br />Applicant must choose one of the following options to be included in the financial warranty <br />calculation: <br />a. Backfill all of the pits to two feet above the groundwater level. <br />b. Install a slurry wall or clay liner. <br />c. Provide the Division with documentation from SEO, which demonstrates the Applicant owns a <br />sufficient amount of shares of water to cover the evaporative losses from the exposed <br />groundwater and the said shares have been committed to the SEO should the financial warranty <br />forfeited and the permit revoked. <br />If the Applicant obtains an augmentation plan prior to final release, then the financial warranty will be <br />adjusted accordingly.