ROSEMONT-12 T. Meyer Power Point Presentation APP Hearings APP Hearings Rosemont Copper Project Rosemont Copper Project By Troy Meyer, P.E. By Troy Meyer, P.E.
WITNESS ISSUES AND TESTIMONY WITNESS ISSUES AND TESTIMONY ISSUE REFERENCE SUBJECT/TESTIMONY Pima County argues that the Attachment F, There was an oversight/error in the technical provisions in § 3.6.1 of the HLF Item #4 specifications. The Issue For Construction (IFC) plans Technical Specifications (Volume I) will include revised specifications excluding the following are contradictory. text “The maximum particle size in the fill shall be no larger than two-thirds the fill compacted lift thickness, In Attachment A2, Pima County unless otherwise approved by the Engineer.” found in alleges that ADEQ erred by the section related to Liner Bedding Fill. approving contradictory technical specifications for liner bedding fill below the Heap Leach Pad (HLP) and that ADEQ erred by approving incomplete Construction Quality Assurance (CQA) plans for the Heap Leach Facility (HLF). Heap Leach Facility Heap Leach Facility
WITNESS ISSUES AND TESTIMONY WITNESS ISSUES AND TESTIMONY ISSUE REFERENCE SUBJECT/TESTIMONY Pima County claims that Attachment F, 1) The statement that “Soil particles coarser than 1 cm (3/8 ADEQ erred in approving an Items #2 and 3 inch) should never be placed directly on a incomplete CQA Plan and geomembrane without first placing a suitable nonwoven associated technical needlepunched geotextile as a protection layer” is taken specifications regarding the from a general geosynthetic design guideline developed base liner system application, by a geosynthetic manufacturer (GSE) and is not deployment and specific to heap leach applications. documentation for the Heap 2) Placement of a geotextile over a heap leach Leach Facility. geomembrane is never done (we are not aware of any heap leach pads constructed in this way) because the resulting geotextile/geomembrane interface shear Pima County claims that a strength would be very low (below 10 degrees) and “geotextile protection layer is would cause the ore pile to be physically unstable. This needed directly on top of the must obviously be avoided to ensure the integrity of the geo-membrane liner” liner containment system (eg, if the ore pile slumps or fails, the liner would be damaged resulting in possible uncontrolled release of process fluids). Heap Leach Facility Heap Leach Facility
WITNESS ISSUES AND TESTIMONY WITNESS ISSUES AND TESTIMONY ISSUE REFERENCE SUBJECT/TESTIMONY Pima County claims that ADEQ Attachment F, 3) Protection of the liner system from puncture is erred in approving an incomplete Items #2 and 3 ensured in the following ways: CQA Plan and associated technical specifications regarding the base •Laboratory testing of the liner system has been liner system application, completed to simulate ore loading to 150% of the deployment and documentation for maximum ore pile height and provides for an effective the Heap Leach Facility. minimum factor of safety (FoS) against liner puncture of 1.5. The testing results indicated satisfactory performance of the proposed liner system. Pima County claims that a “geotextile protection layer is •A test fill program will be developed and conducted needed directly on top of the geo- prior to construction of the heap leach liner system to membrane liner” simulate placement of the overliner gravel and haul truck traffic on the overliner. The CQA Engineer will provide oversight and document the results of the test fill and develop final procedures for overliner placement to ensure protection of the liner during leach pad construction. The test fill is required by the technical specifications Section 3.7.2 which reads in part “Methods shall be developed onsite for placing the material in a manner that will protect the geomembrane and/or pipework from damage” Heap Leach Facility Heap Leach Facility
WITNESS ISSUES AND TESTIMONY WITNESS ISSUES AND TESTIMONY ISSUE REFERENCE SUBJECT/TESTIMONY Pima County argues that Attachment F, The heap leach pad liner system design includes anchor (i) “CQA Plan and Technical Item #5 trenches along the perimeter of the pad. Details of the Specifications should discuss the anchor trenches are provided on Drawing 080-CI-923. need and preliminary design for The placement of overliner gravel on the geomembrane anchor benches/trenches within the will provide interior anchoring against wind uplift. The interior of the heap leach pad areas geomembrane liner will not be left exposed but will be …;” immediately covered by the overdrain gravel. Heap Leach Facility Heap Leach Facility
WITNESS ISSUES AND TESTIMONY WITNESS ISSUES AND TESTIMONY ISSUE REFERENCE SUBJECT/TESTIMONY Pima County argues that Attachment F, Section 4.3.1 of the technical specifications clearly states the (ii) “the technical Item #6 material requirements of the GCL and states that “The GCL specifications are insufficient material shall be sampled and tested in accordance with the by not specifying Manufacturer’s approved QC Manual.” Section 9 of the CQA Geosynthetic Clay Liner plan states “Conformance of the GCL to the Technical information relating to Specifications shall be verified by the CQA Consultant. manufacturer, installer Individual test methods shall be clearly stipulated and experience, delivery, and communicated to the parties involved with testing” conformance testing, among other things;” Section 4.3.2 of the technical specifications provides detailed installation instructions for the GCL including subgrade acceptance, deployment, covering and protection, seam orientation and overlaps, and repairs. Deployment of GCL does not require any special contractor qualifications as it does not involve specialized equipment or skills. The General (Earthwork) Contractor typically can complete this task, with observation and documentation (panel surveys, photos, as-built drawings, etc.) provided by the CQA Engineer. This section of the specifications also states “GCL shall not be covered prior to inspection and approval by the CQA Engineer.” Heap Leach Facility Heap Leach Facility
WITNESS ISSUES AND TESTIMONY WITNESS ISSUES AND TESTIMONY ISSUE REFERENCE SUBJECT/TESTIMONY Pima County argues that Attachment F, Section 4.3.2 of the technical specifications provides detailed (iii) the Technical Item #7 installation instructions for the GCL including the following Specifications failed to statement “Panels shall be positioned with the seam overlap not specify “how a proper less than six (6) inches after shrinkage for longitudinal seams determination of GCL seam and two (2) feet after shrinkage for end-of-panel seams”. The overlap is performed on a wording of this requirement suggests that the overlap does not daily basis during account for hydration shrinkage, when in fact it does. According deployment;” to the manufacturer of the specified GCL, the minimum acceptable overlap is 6 inches. This is consistent with recommendations in ASTM D 6102 “Standard Guide for Installation of Geosynthetic Clay Liners” which accounts for research related to hydration shrinkage of GCL panels. A potential industry-wide concern for GCL shrinkage was identified by Thiel and Richardson based on observed problems at several sites worldwide. All of the known problems were for installations where an exposed geomembrane/GCL composite installation was left unballasted (that is, with no overlying cover soil) for an extended time. It has generally been accepted in the industry that a minimum of 12in. of cover soil will preclude further GCL shrinkage and that ballast should be added within 30 days. Since industry standards have not provided specific guidance to address this issue and it is currently unknown how long the liner will be left unballasted at Rosemont, we are proposing that the specification be modified to include heat tacking of the GCL seams to mitigate against shrinkage gaps developing following gemembrane deployment and prior to ballasting with overliner material. This approach has been used Heap Leach Facility Heap Leach Facility with proven success at several sites, including Carlotta heap leach in Arizona.
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