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Home My WebLink About20101425.tiff Varra Companies, Inc. Office of Special Projects 1431 East 1e Street Greeley, Colorado 80631 Telephone(970)353-8310 Fax(970)353-4047 Friday 2 July 2010 11 2`43 ut -2 p Weld County Clerk to the Board 2 ft 91510`h Street,3"i Floor Greeley, Colorado 80632 • Subject: Varra Companies, Inc. - Firestone Project(Pit 112) - Regular Impact(112) Technical Revision Application - Permit M1984-079 Materials submitted to the Colorado Division of Reclamation Mining and Safety (CRMS) - Office of Mined Land Reclamation (OMLR): • Correspondence of 2 July 2010 and attachments. ATTACHEMENTS: • Correspondence -C.G.R.S. dated 1 July 2010. Your signature below acknowledges receipt of the above referenced material, as attached. The material should be added to the above referenced Application, as originally submitted to the Weld County Clerk to the Board,and made accessible for public review. Received On , 2010 By: Office of the Weld County Clerk to the Board of County Commissioners UC IStV'I r1 2010-1425 Varra Companies, Inc. FIRESTONE PROJECT(PIT 112) OMLR Techncial Revision M1984-079 2 July 2010 Varra Companies, Inc. Office of Special Projects 8120 Gage Street Frederick,Colorado 80516 Telephone(970)353-8310 Fax(970)353-4047 Friday 2 July 2010 To: Jared Ebert, EPS Colorado Office of Mined Land Reclamation 1313 Sherman Street, #215 Denver, Colorado 80203 From: Varra Companies, Inc. -Bradford Janes, Professional Forester C a 9 Y Subject: M-1984-079 Firestone Pit 112—Reply to the Colorado Office of Mined Land Reclamation (Office) Preliminary Adequacy Review correspondence of 27 April 2010. Dear Jared: For greater continuity and ease of reference, we have iterated your comments by item in a graphical box, with our comments in blue following: Narrative: 1. Under Item #2 of the Technical Revision you requested additional time to complete all the steps of reclamation for the area around the lined pond. The Division approves this request, the Operator will be required to grade, topsoil and seed the site by March 20`h, 2011. The Division understands it may take several growing seasons and some site maintenance for the vegetation to establish. The Operator acknowledges the approval. 2. Item #4 of the Technical Revision indicates Area 2 of the site displayed on the submitted maps will not be re-soiled and re-vegetated and will continue to be used for agricultural and commercial purposes. The issue was discussed during the original permitting process in 1984. In accordance with Rule 6.4.5 (2) (b), if a site is to be reclaimed for industrial use, this post- mining land use must be reasonably assured. Please submit evidence this parcel is zoned for industrial commercial use. If it is not, this site must be re-soiled and re-vegetated in accordance with the approved plan. The Town of Firestone designates on its zoning map that the location is considered RC Regional Commercial (provides goods and services regionally). The Town zoning and land use maps is viewable at the town website at: http://www.ci.firestone.co.us/Mapping/mapping.html. The specific land use is identified by quarter section legal description and should support our understanding of the zoning of the permit area. Varra Companies, Inc. correspondence of 18 May to the Colorado Office of Mined Land Reclamation(Office) 1 in reply to Office correspondence of 27 April 2010—Firestone Pit— M-1984-079. Varra Companies, Inc. Office of Special Projects 8120 Gage Street Frederick, Colorado 80516 Telephone(970) 353-8310 Fax(970) 353-4047 Reclamation Plan Maps: 3. The maps submitted are very accurate depictions of the current state of the operation and future proposed activities at the site. The narrative submitted with the Technical Revision indicates the soil stockpile depicted on the map north of the southeast portion of Area 5 will be used to re-soil designated areas. However, there are stockpiles of material depicted in Area 2, Area 3 and land adjacent to the Oil and Gas Operation Area A. The Division assumes these stockpiles will be removed during final reclamation. However, it is unclear; please indicate what will be done with remaining stockpiles on the site. All stockpiles will either be removed by sale or trade, or otherwise utilized on-site during development as market conditions warrant. 4. Please indicate what contour interval was used to create the topographic lines? Contours are shown at one foot intervals. Hydrologic Balance: 5. Since the Operator installed the clay liners for the two basins prior to the Division's approval, no analysis has been submitted to the Division in regards to the possible impacts the clay liners may have on the surrounding hydrologic balance specifically for mounding and shadowing affects. The Division has observed clay liners, slurry walls and backfilled pit excavations impede the flow of ground water ad cause mounding impacts to land adjacent to these nearly impervious basins. Was any ground water elevation monitoring conducted at the site for lands adjacent to the clay liners prior to their construction? Please determine what impact the installation of these clay liners and the backfilling activity may have on the surrounding ground water levels. Determine how ground water levels will be monitored to determine if a mounding problem is occurring and how the Operator will mitigate possible mounding problems. Please refer to correspondence of C.G.R.S., dated 1 July 2010, as included with this submittal. Attachments: 1 Proof of Placement of this material with the Weld County Clerk to the Board. 2 Correspondence -C.G.R.S. dated 1 July 2010. Varra Companies, Inc. correspondence of 18 May to the Colorado Office of Mined Land Reclamation(Office) 2 in reply to Office correspondence of 27 April 2010— Firestone Pit—M-1984-079. CGENVIRONMENTAL &iQMD©R July 1, 2010 Mr. Garrett Varra Varra Companies, Inc. 8120 Gage Street Frederick, Colorado 80203 Re: Water Impoundment Hydrology CGRS No. 1-135-10807ab Dear Garrett: This letter and attachments address comments presented by Colorado Division of Reclamation, Mining and Safety regarding mounding and shadowing related to water impoundments. Any impoundment or pond that holds water at an elevation above the surrounding water table will have the potential of increasing the water table elevation (mounding) at some distance from the pond, which is determined by the total groundwater-pond head difference. For ponds that are large in areal extent the distance to no influence on the upstream side is usually less than the downstream side as the head difference will be less based on the water table's hydraulic gradient. The influence imposed by the pond can be estimated by one dimensional unconfined flow solutions presented by McWhorter and Sunada, 1977. Numerical models can be used but we have found model results generally agree well with analytical solutions. An example calculation using a one dimensional unconfined flow equation is presented as Attachment A. In most unconfined flow regimes we consider the distance to no influence (or measurable influence) generally to be on the order of 600 feet. For your operations it appears the pond and groundwater head difference is on the order of five feet. Given this scenario at 100 and 300 feet from the pond the resulting mounding would be four and two feet, respectively. We advise that great care be given when constructing water impoundments (lined or unlined) within 100 feet of any subsurface structures. We have evaluated the affects of impermeable barriers on groundwater hydrology by using the analytical model TWODAN. We simulated a uniform flow field using aquifer properties typically associated with sand and gravel deposits. We then simulated an impermeable barrier within the flow field. The results indicate that the groundwater hydrology is modified but only severely in very close proximity to the barrier. Upstream of the barrier the hydraulic gradient will increase and will decrease downstream of the barrier. Hydraulic gradient changes of between one and two feet are observed within 15 feet of the barrier wall but are negligible at any significant distance from the hydraulic structure. A P.O. Box 1489 Fort Collins,CO 80522 T 800-288-2657 F 970-493-7986 www.cgrs.com Mr.Garrett Varra July 1,2010 Page 2 oft graphical output depicting the barrier wall simulation is provided in Attachment B. We also ran simulation in ModFlow, which yielded similar results. If you have any questions regarding this letter, please contact me at 970-493- 7780. Sincerely, CGRS, Inc. Y . Adams. P.G. Principal/Hydrogeologist REFERENCES McWhorter, D. and Sunada, D. K., 1977. Groundwater Hydrology and Hydraulics. Water Resource Publications, Littleton,Colorado,pp 146-148. ATTACHMENT A UNCONFINED FLOW ANALYSIS Spreadsheet Calculates One Dimensional Head Distribution (Unconfined) h =s hie+X2(H2—hie) H Head at no influence(ft) 740158 h Head at point of interest(calculated) , , hi Head at retention pond X Distance from pond to point of interest(ft) 300 L Distanct to no influence(ft) B00' ATTACHMENT B BARRIER WALL MODEL RESULTS I r a -- 86 - _—_ _—_ _—_ _—_— —_ - _—_—- 88 _ -— —_— —_—_ _— —_ - _ _—_ - 8! 90 - _ _—_ _—8 , _—__ _— •r A _ 8 —- ' _. 8: 96 -—_ —_— —_—_ __ _— —_ _—-—7 9 100 1( —-—-—- Approximate Gradient Line in Uniform Flow X span:0 to 800 Y span:0 to 800 Impermeable Barrier Solution Vera Companies Hello