Rosemont Copper Project Dual Phase Heap Leach Facility

Transcription

1 Rosemont Copper Project Dual Phase Heap Leach Facility Technical Specifications Prepared for: 4500 Cherry Creek South Drive, Suite #1040 Denver, Colorado Phone: (303) Fax: (303) Prepared by: 3031 West Ina Road Tucson, Arizona Phone: (520) Fax: (520) Tetra Tech Project No February 2012

2 TABLE OF CONTENTS 1.0 SCOPE AND REQUIREMENTS Work Scope Definition of Terms General Technical Requirements Submittals MOBILIZATION AND DEMOBILIZATION Mobilization Contractor s Workshops, Stores, and Offices Sanitation Construction Roads Drainage Demobilization EARTHWORK Clearing, Grubbing, Stripping, and Stockpiling Removal of Existing Infrastructure Well Abandonment Excavation Subgrade Preparation Borrow Development General Fill Placement Procedures Compaction Equipment Site Grading Fill and Liner Bedding Fill Material Requirements Placement Test Fills Pipe Backfill Material Requirement Placement Overliner Drain Fill Material Requirement Placement Anchor Trench Fill Material Requirement Placement Riprap Material Requirement Placement GEOSYNTHETICS Geomembrane (HDPE and LLDPE) General Tetra Tech February 2012 i

3 4.1.2 Geomembrane Manufacturer s Experience Submittal of Engineering Data Delivery, Storage and Handling of the Geomembrane Material Requirement Conformance Testing Installation Field Quality Control Repairs Quality Assurance and Acceptance Drainage Layer (Geonet and Agru Drain Liner) Material Requirement Geonet Installation Geosynthetic Clay Liner (GCL) Material Requirement Shipping, Handling and Storage Installation Geotextile Definitions Performance Requirements Submittals Delivery, Storage, and Handling Material Construction PIPEWORK (Corrugated and Non-Corrugated HDPE Pipe) Corrugated PE Pipe HDPE Pipe Installation CAST-IN-PLACE CONCRETE Concrete Materials Workmanship Placement Concrete Testing Concrete Reinforcement Tetra Tech February 2012 ii

4 1.0 SCOPE AND REQUIREMENTS 1.1 Work Scope The work scope associated with these Technical Specifications includes the requirements and procedures necessary to complete the construction of all earthwork, geosynthetics, and drain pipework for the Rosemont Copper Heap Leach Facility (HLF) in Pima County, Arizona. Any alternatives or exceptions to these Technical Specifications shall be submitted in writing to the Owner and shall require approval in writing from the Owner prior to implementation of the Work. The Work associated with construction of the Rosemont Heap Leach Facility generally includes: site preparation, fill placement, geosynthetics installation, and pipework installation. Process solution pumping/piping and ore delivery and heap stacking equipment, including all associated appurtenant items and structures, are not part of these Technical Specifications. Specific features of the work scope include, but are not limited to, the following: Mobilization/demobilization of all equipment and material required for the work; Installation of temporary diversions for surface water control; Clearing, grubbing, and stripping in required areas; Excavation in required areas; Development of borrow areas within and outside the HLF limits; Construction of temporary and permanent access roads; Foundation preparation for Site Grading Fill and liner placement; Fill placement and compaction; Installation of geosynthetic materials for liner, drainage, and leak collection systems; Installation of leach pad gravity flow drain pipework (solution collection piping); Concrete (drainage swale); Placement of Overliner Drain Fill; and Furnishing and installing all materials and constructing all items appurtenant and incidental to the above. The construction plans and the quality of the constructed leach pad and associated ponds are important aspects of this project. All earthwork and geosynthetic construction Quality Assurance/Quality Control (QA/QC) test locations and results shall be summarized in an as-built report, a copy of which shall be kept in the Owner s files. Tetra Tech February

5 1.2 Definition of Terms Owner is defined as an authorized representative of (Rosemont). The Owner owns, and is responsible for, the facility. Engineer is defined as a representative appointed and authorized by the Owner. The Engineer shall be a Registered Professional Engineer in the State of Arizona, or shall be a designated Site representative under the supervision of a Registered Professional Engineer. The Engineer is responsible for the design, Drawings, and Technical Specifications for the earthwork and any geomembrane and/or related geosynthetics. Contractor is defined as the party which has executed a contract agreement with the Owner for the specified Work. Earthwork Contractor is defined as a Contractor specifically retained to perform earthwork pertaining to the HLF. The Earthwork Contractor is responsible for the quality of the Work as outlined in the construction documents such as earthworks, concrete works, drain pipework installation, and the preparation of the soils, including clearing, the installation of underdrains, and Overliner Drain Fill. The Earthwork Contractor shall also prepare the subgrade on which the geosynthetics are placed and the trench in which the geosynthetics are anchored. Geomembrane Installer is defined as a Contractor specifically retained to perform Work pertaining to geosynthetic materials associated with the HLF. The Geomembrane Installer is responsible for field handling, storing, placing, seaming, ballasting (loading against wind), and other aspects of the geosynthetics installation. The Geomembrane Installer may also be responsible for transportation of these materials to the Site and for the preparation and completion of anchor trenches. The Geomembrane Installer may be a division of the Geomembrane Manufacturer, or an approved installer of the Geomembrane Manufacturer's products. Geomembrane Manufacturer is defined as a manufacturer of geosynthetic materials purchased for the HLF. The Geomembrane Manufacturer is responsible for the production of the geomembrane and possibly some prefabricated appurtenance components. Technical Specifications is defined as this document, prepared by Tetra Tech, including all supplemental addenda as appropriate. Drawings are defined as the Drawings, provided in Appendix A of the report titled Rosemont Heap Leach Facility Final Design Report (2012) Rosemont Copper Project prepared by Tetra Tech and dated February Work is defined as the entire completed construction, or the various separately identifiable parts thereof, required to be furnished under the Contract Documents. Site is defined as the project area where the Work is to be performed. Contract Documents are defined as the Agreement, Addenda, Contractor's Bid (when attached as an Exhibit to the Agreement), Bonds, General Conditions, Special Conditions, Technical Specifications, Drawings, and all modifications issued after execution of the Agreement. Modifications are defined as changes made to the Technical Specifications or the Drawings that are approved by the Owner and Engineer in writing after the Technical Specifications and Drawings have been finalized for construction. Tetra Tech February

6 1.3 General Technical Requirements The general technical requirements specified herein shall apply to all activities and operations relating to carrying out the Work or as required by the Owner or Engineer. In the event of a contradiction between the Technical Specifications and the Drawings, the Contractor shall refer all questions to the Engineer for clarification. Work associated with the contradiction shall not be performed until the contradiction is remedied or clarified by the Engineer. In all cases, the decision of the Engineer is final. 1.4 Submittals Any alternatives or exceptions to these Technical Specifications shall be submitted in writing to the Owner. The Contractor shall provide the Owner and Engineer with the procedures and equipment to be used for surveying and construction, including material specifications. This is required for review and approval prior to the Work being allowed to commence and the materials brought to the Site. Tetra Tech February

7 2.0 MOBILIZATION AND DEMOBILIZATION 2.1 Mobilization The Contractor shall mobilize to the Site sufficient labor, materials, and equipment to allow commencement of the Work. The Contractor shall bring onto the Site, as and when necessary, any additional equipment, labor, and materials which may be required to complete the remainder of the Work in the time specified in the Contract Documents. 2.2 Contractor s Workshops, Stores, and Offices The Contractor shall erect, in the area designated by the Owner, adequate workshops, offices, and other buildings and structures for the completion of the Work as designated in the Contract Documents. Such workshops, offices, etc., shall be maintained in a neat and tidy condition throughout the duration of the Work to the satisfaction of the Owner. 2.3 Sanitation The Contractor shall provide and maintain adequate sanitary facilities for the personnel at the Site, including the Contractor's offices and Engineer's offices, as needed, in compliance with local health regulations and to the satisfaction of the Owner. 2.4 Construction Roads All temporary construction roads, which the Contractor may require to complete the Work, shall be constructed at the Contractor's expense. The location of any temporary roads, or portions thereof, on the Site shall be subject to the Owner's and Engineer s approval prior to construction. Unless otherwise approved by the Owner, all temporary roads shall be reclaimed at the Contractor's expense upon completion of the Work. 2.5 Drainage Adequate drainage facilities in the form of ditches, culverts, or other conduits shall be installed as necessary to protect the Work and to maintain temporary construction or access roads. These temporary drainage facilities shall be constructed to the satisfaction of the Owner and Engineer. 2.6 Demobilization Upon completion of the Work, the Contractor shall remove all Contractor equipment and materials from the Site. The Site shall be left in a clean and tidy condition to the satisfaction of the Owner. All waste and refuse shall be disposed of in a manner acceptable to the Owner. Tetra Tech February

8 3.0 EARTHWORK 3.1 Clearing, Grubbing, Stripping, and Stockpiling The natural ground surface shall be cleared, grubbed, and stripped of all organic and objectionable materials by the Earthwork Contractor to the limits shown on the Drawings or as required by the Owner or Engineer. The limits of stripping shall generally be ten (10) feet outside of the Work areas shown on the Drawings. All usable topsoil shall be properly stockpiled in locations designated by the Owner. Clearing and grubbing shall mean the removal of vegetation and roots. Stripping shall mean the removal of topsoil, which is defined as soil of any gradation or degree of plasticity that contains significant quantities of visually identifiable vegetable matter, sod, roots, or humus as determined by the Engineer, or that can be used as growth medium. The depth of topsoil to be removed shall be determined by the Engineer based on the character and thickness of material encountered. Clearing, grubbing, and stripping may be conducted as a single operation. Prior to stripping, the topsoil may require moisture conditioning to the satisfaction of the Engineer in order to prevent the loss of fines and to maintain dust control. The Earthwork Contractor shall allow sufficient time after pre-wetting for the moisture to be evenly distributed throughout the topsoil layer prior to removal. The topsoil may need to be ripped prior to moisture conditioning to allow the moisture to be evenly distributed throughout the topsoil layer. The decision of when to rip the topsoil, and how often for the purpose of moisture conditioning, shall be determined by the Engineer. Additional moisture conditioning may be required on stockpiled materials as determined by the Engineer. Stripping shall be carried out by the Earthwork Contractor using methods acceptable to the Engineer. Any stripping beyond ten (10) feet of the Work areas shown on the Drawings shall be subject to the approval of the Owner or Engineer. Unapproved stripping may be subject to remediation at the sole expense of the Earthwork Contractor. Following stripping operations, the ground surface shall be treated as specified on the Drawings or in these Technical Specifications. This activity may involve trimming and shaping the surface, scarifying, moisture conditioning, or placing fill material. The Engineer shall inspect the surface prior to any surface treatment. 3.2 Removal of Existing Infrastructure Existing Infrastructure which has not been designated on the project plans to remain, except for those structures and obstructions which are to be removed and disposed of under other items of work, shall be wholly removed from the site and disposed of in a satisfactory manner. Materials removed and not designated to be salvaged or incorporated into the work shall become the property of the contractor. Existing structures and other existing improvements which are to become an integral part of the planned improvements shall remain even though not specifically noted. Blasting or other operations necessary for the removal of an existing structure or obstruction, which may damage new construction, shall be completed prior to commencing the new work. Holes, cavities, trenches and depressions resulting from the removal of structures or obstructions, except in areas to be excavated, shall be backfilled with suitable material which shall be moisture conditioned to within plus or minus two (2) percent of the optimum moisture content, and recompacted to a minimum of 95 percent of the maximum dry density (ASTM D 698), as directed and approved by the Engineer. Tetra Tech February

9 3.3 Well Abandonment Wells obstructing construction shall be abandoned in accordance with the requirements of Arizona Administrative Code R Well casings shall be removed to an elevation a minimum of 20 feet below the land surface. Wells shall be sealed in a manner acceptable under A.A.C. R that provides sufficient volume, density, and viscosity to prevent fluid communication between the surface and underlying aquifers as well as between multiple underlying aquifers. 3.4 Excavation Excavation shall consist of excavating to the lines and grades shown on the Drawings and hauling materials to designated fills, stockpiles, or waste areas. Excavation methods, techniques, and procedures shall be developed by the Earthwork Contractor with due consideration of the nature of the materials to be excavated and shall include all precautions necessary to preserve, in an undisturbed condition, all areas outside the lines and grades shown on the Drawings or required by the Owner or Engineer. The work shall be carried out by methods that produce acceptable end results as determined by the Engineer. No excavation beyond the lines and grades shown on the Drawings, or as required by the Engineer, shall be done without the prior written approval of the Owner. If such additional excavation is done without the prior written approval of the Owner and, in the opinion of the Engineer, requires backfilling in order to satisfactorily complete the Work, such backfilling may be completed at the Earthwork Contractor's expense. All backfilling shall be subject to approval by the Engineer. Pockets of unsuitable materials found within the limits of an excavation shall be removed and disposed of as directed by the Owner or Engineer. Unsuitable materials may include, but not be limited to, ash, boulder or gravel zones, soft saturated zones, highly organic zones, drilling mud pits, and other deleterious material. As required by the Owner, topsoil and waste stockpiles shall be leveled, trimmed, and shaped to prevent the occurrence of ponding or concentration of surface runoff and to provide a neat appearance. Slopes of the topsoil stockpiles shall be graded to 2.5H:1V (horizontal: vertical) and all surface water run-off shall be directed to existing surface water management structures. 3.5 Subgrade Preparation After clearing, grubbing, stripping, and excavating, the exposed subgrade surface shall be inspected and evaluated by the Engineer for the presence of loose or soft areas or unsuitable material prior to fill placement or installation of geosynthetics. Evaluation methods will depend on the prevailing field conditions, the location of the subgrade, and the materials that will be placed over the subgrade. Evaluation methods may include proof-rolling with a loaded dump truck or similar pneumatic-tired equipment to ensure that the surface is firm and smooth. Probing with a metal rod may also be performed. Soft or yielding areas delineated by the evaluation that cannot be stabilized by re-compacting shall be removed and replaced with acceptable Site Grading Fill. Unsuitable materials shall also be removed and replaced with acceptable Site Grading Fill as directed by the Engineer. The subgrade shall be prepared to the satisfaction of the Engineer. Stripped rock subgrade surfaces and rock outcrops shall be cleared of loose rock fragments greater than two (2) inches in size and wetted in preparation for Site Grading Fill or Liner Bedding Fill. Fill shall be placed in varying thicknesses as shown on the plans or as required by field conditions to support the leach pad/pond liner systems. The fill shall be placed and Tetra Tech February

10 compacted as specified in Section 3.7 General Fill Placement Procedures within these Technical Specifications. Soil subgrade surfaces receiving fill shall be scarified to a minimum depth of six (6) inches, moisture conditioned to within plus or minus two (2) percent of the optimum moisture content, and recompacted to a minimum of 95 percent of the maximum dry density (ASTM D 698). Natural soil subgrade areas receiving geosynthetics shall be prepared such that the final surface is smooth and free of protruding rocks, vegetation, or any other materials or objects deemed unsuitable by the Engineer. Rocks larger than 1.5 inches in the upper six (6) inches of the natural soil receiving geosynthetics shall be removed. In areas where rocks larger than 1.5 inches are protruding, the rocks shall be removed and replaced with compacted Liner Bedding Fill material. Placement of the Liner Bedding Fill material may also be placed in other areas as needed to produce a relatively smooth surface suitable for installation of the geosynthetics. The Contractor shall modify (smooth) the existing contours such that the finished subgrade surface, i.e., natural cut surface or surface receiving Liner Bedding Fill, approximately conforms to the contours shown on the Drawings. While exact contours are not required, the Contractor shall maintain positive drainage and ensure that there are no abrupt changes in grade that would prohibit placement of, or create stress in, the overlying liner systems. No fill shall be placed until the stripped and reworked areas have been inspected and approved by the Engineer. 3.6 Borrow Development The majority of the Site Grading Fill will consist of local excavated materials that will generate quality Gila Conglomerate (unconsolidated). The Contractor shall also excavate, haul, place, and compact site grading cut materials from required excavations within the limits of the HLF which includes the leach pad and ponds as shown on the Drawings. In addition, the Owner will designate borrow areas outside the HLF, as needed, for the Contractor to excavate fill materials. The Owner plans to stockpile crushed ore materials adjacent to the pad limits for the Contractor to haul and place as Overliner Drain Fill above the pad liner or other areas as needed. The Contractor may select and use any Owner/Engineer approved borrow area for obtaining construction materials, provided the materials meet the requirements in these Technical Specifications for their intended use. Representative tests shall be conducted by the Engineer on the borrow materials in the field or at an off-site laboratory to determine the materials suitability for use as fill. It shall be the Contractor's responsibility to notify the Engineer of any changes in the borrow source consistency in advance of development to allow time for representative testing without unduly interrupting construction activities. Should a borrow material prove to be unsuitable for fill, a new borrow source shall be designated by the Owner, or the Contractor's processing operations shall be adjusted to produce acceptable fill material meeting these Technical Specifications. The Contractor shall coordinate with the Owner, as needed, to schedule and coordinate the production and/or stockpiling of acceptable borrow materials from on-site and off-site sources for the execution of the Contractor's work. Acceptable borrow areas shall be cleared, grubbed, and stripped in stages, as approved by the Owner/Engineer, to minimize ground disturbance. Each stage of stripping shall be sufficient in extent for the Contractor to operate conventional earthwork equipment for conditioning and excavating materials acceptable for fill placement. Moisture conditioning in preparation for fill placement, if required, shall be done in the borrow area(s) as much as practical. Tetra Tech February

11 The final surfaces of all borrow areas developed by the Contractor shall be left in reasonably smooth, even conditions and graded to drain for long-term stability. Final surface grading shall be by dozer or grader blade operations, as approved by the Engineer. Final cut slopes shall be no steeper than 2H:1V unless approved by the Engineer. The Contractor shall replace stripped topsoil cover over the final borrow cuts, unless otherwise approved by the Owner. 3.7 General Fill Placement Procedures All materials used for fill shall be loaded and hauled to the placement site, dumped, spread, and leveled to the specified layer thickness, moisture conditioned as required, and compacted to form a dense integral fill in accordance with these Technical Specifications and to the approval of the Owner and Engineer. Under most conditions, the fill shall be constructed in near horizontal layers with each layer being completed over the full length and breadth of the zone before placement of subsequent layers. Each zone shall be constructed with materials meeting the specified requirements and shall be free from lenses, pockets, and layers of materials that are substantially different in gradation from the surrounding material in the same zone as determined by the Engineer. All fill placed shall be free from organic debris, frozen soil, ice, or other unsuitable materials. All oversized material shall be removed from the fill material either prior to it being placed or after it is dumped and spread but prior to compaction. All particles that have dimensions that will interfere with compaction in the specified layer thickness, as determined by the Engineer, shall be removed from the zone in which they were placed either prior to or during compaction. As approved by the Engineer, fill may be compacted by routing the hauling and spreading equipment approximately parallel to the long axis of the fill. The hauling equipment shall be routed in such a manner that they do not follow the same paths but spread their traveled paths evenly over the surface of the fill. Moisture conditioning is the operation required to increase or decrease the moisture content of material to within the specified limits. If moisture conditioning is necessary, it shall be carried out by whatever method the Earthwork Contractor deems suitable, provided it produces the moisture content specified in these Technical Specifications or designated by the Engineer. The moisture shall be distributed uniformly throughout each layer of material being placed immediately prior to compaction. Measures shall be adopted, as needed, to ensure that the designated moisture content is preserved after compaction and until the succeeding layer is placed. Should the surface of the fill become rutted or uneven subsequent to compaction, it shall be regraded and recompacted before the next layer of fill is placed. To permit suitable bonding with the subsequent layer, the surface material shall be loosened by scarifying or disk harrowing as needed and as approved by the Engineer, and if necessary, it shall be moisture conditioned before an additional layer is placed. Compaction of each layer of fill shall proceed in a systematic, orderly, and continuous manner approved by the Engineer to ensure that each layer receives the specified compaction. The rolling pattern for compaction of all zone boundaries or construction joints shall be such that the full number of roller passes required in one of the adjacent zones, or on one side of the construction joint, extends completely across the boundary or joint. Fill shall not be placed on frozen soil or when air temperatures drop below 32 F unless otherwise approved by the Engineer. Tetra Tech February

12 3.7.1 Compaction Equipment Sufficient equipment shall be provided as necessary for compaction of the various fill materials. Compaction equipment shall be maintained in good working condition at all times to ensure that the amount of compactive effort obtained is a maximum for the equipment. Before commencing Work with the proposed compaction equipment, the Owner and the Engineer shall be provided with a list of each piece of equipment to be used together with the Manufacturer's specifications. If alternative equipment different from what was initially proposed is to be used, a submittal shall be made to the Engineer for approval of the equipment. The submittal shall give complete details of such equipment and the methods proposed for its use. The Engineer's approval of the use of alternative equipment may be dependent upon completion of suitable test fills, to the satisfaction of the Engineer, to confirm that the alternative equipment will compact the fill materials to the specified density. The use of mine haul trucks or scrapers as compaction equipment shall be acceptable provided that test fills confirm the fill materials can be adequately compacted with the proposed equipment. The following compaction equipment and specifications may be considered Smooth Steel Drum Vibratory Roller Smooth steel drum vibratory rollers shall be equipped with a suitable cleaning device to prevent the accumulation of material on the drum during rolling. Each roller shall have a total static weight of not less than 10 tons at the drum when the roller is standing on level ground. The drum shall be not less than five (5) feet in diameter and 6.5-feet in width. The vibration frequency of the roller drum during operation shall be between 1,100 and 1,500 vibrations per minute, and the centrifugal force developed by the roller, at 1,250 vibrations per minute, shall not be less than 19 tons. The power of the motor driving the vibrator shall be sufficient to maintain the specified frequency and centrifugal force under the most adverse conditions, which may be encountered during the compaction of the fill Tamping Foot Roller The tamping foot roller shall be a self-propelled, fully ballasted, standard tamping foot design developing 24 tons per linear foot of width at rest on level ground, or equivalent, as approved by the Engineer Special Compactors Special compactors and compaction measures shall be used to compact materials that, in the opinion of the Engineer, cannot be compacted properly by the specified roller because of location or accessibility. Such special compactors and measures may include hand-held vibratory compactors or other methods approved by the Engineer to compact fill in trenches, around structures, and in other confined areas that are not accessible to a larger vibratory roller or tamping foot roller. All compaction shall be to the specified density. 3.8 Site Grading Fill and Liner Bedding Fill Site Grading Fill and Liner Bedding Fill shall be placed within the limits of the HLF to achieve the desired final grades as shown on the Drawings. Tetra Tech February

13 3.8.1 Material Requirements Material for compacted Site Grading Fill may consist of any material which, when compacted, is suitable for use in the various parts of the Work. Site Grading Fill material may have a wide range of Unified Soil Classifications and may contain significant variations in gradation and compaction properties. Materials that contain or are contaminated by organic matter are not suitable for use as Site Grading Fill. Site Grading Fill shall be placed in areas where the material is not required to be of uniform character and engineering properties. The Site Grading Fill may be obtained from several sources, including areas from required excavation or regrading activities within the HLF limits (leach pad and ponds) and from borrow areas as necessary. Site Grading Fill shall be used to fill the valleys and the toe areas of the leach pad to the lines and grades shown on the Drawings. Site Grading Fill shall also be used to construct the collection pond embankments. Site Grading Fill shall have a maximum rock particle size no more than two-thirds the loose thickness of the fill lift. Site Grading Fill shall generally have a one (1) foot maximum rock particle size and oversized rocks larger than one (1) foot shall be removed to the exterior fill slopes. Rocks larger than one (1) foot may be incorporated in thicker fill lifts provided the rocks do not protrude from the lift surfaces after compaction, and the required lift compaction is proven achievable by a test fill. Liner Bedding Fill shall generally include inorganic soils with less than about 30 percent particles larger than 0.75 inches and a maximum 1.5 inch particle size. Soft, weathered rock, that breaks down during excavation, hauling, and processing operations to essentially form a soil and compacts without excessive voids, may be used as Liner Bedding Fill, as approved by the Engineer. Oversized materials shall be removed from the fill Placement The surface upon which Site Grading Fill or Liner Bedding Fill is placed shall be prepared as specified in Section 3.5 Subgrade Preparation within these Technical Specifications. Liner Bedding Fill material shall be placed and spread in the fill to form lifts which shall not exceed a one (1) foot loose thickness unless otherwise specified by the Engineer, and the placement method is proven to achieve the specified compaction in a test fill. The actual lift thickness may need to be less than one (1) foot in loose thickness to meet the compaction requirement. Cobbles and boulders that are large enough to interfere with the construction of the designated lift thickness shall be removed and disposed of in areas specified by the Owner or Engineer. Site Grading Fill material shall also be spread in individual lifts and shall be conditioned, placed, and compacted according to the method specifications derived from the results of a test fill, as appropriate. The Site Grading Fill lifts shall generally not exceed 1.5 feet in loose thickness unless otherwise specified by the Engineer, and the placement method is proven to achieve the specified compaction in a test fill. The actual lift thickness may need to be less than 1.5 feet in loose thickness to meet the compaction requirement. Test fill procedures are outlined in the Section 3.8. After spreading, the Site Grading Fill or Liner Bedding Fill material shall be moisture conditioned, if necessary, by sprinkling and disk harrowing until a uniform distribution of moisture is obtained. Material that is too wet may be spread on the fill area and permitted to dry, assisted by disking and harrowing if necessary, until the moisture is reduced to an amount within the specified limits. Immediately prior to compaction, the Contractor shall utilize all measures necessary to achieve a moisture content for the Site Grading Fill or Liner Bedding Fill that is within plus or minus two (2) percent of the optimum moisture content and that is distributed uniformly throughout the lift of material being placed. The Contractor shall utilize Tetra Tech February

14 whatever measures necessary to ensure that the designated moisture content is preserved after compaction until the succeeding lift is placed. The Engineer may specify deviation from the moisture content limits provided the required compaction is achieved. Each Site Grading Fill or Liner Bedding Fill lift shall be compacted to a minimum of 95 percent of the maximum dry density (ASTM D 698). Materials which are non-proctorable by ASTM D 698 shall be placed in accordance with methods developed during the test fills Test Fills Test fills associated with the Site Grading Fill, as needed, shall be conducted according to the US Army Corps of Engineers standards to establish the specifications for the proper placement and compaction of Site Grading Fill having more than 30 percent particles larger than 0.75 inches. Test fills shall also be conducted if circumstances arise where they are deemed necessary by the Engineer, such as in order to determine if greater or lesser lift thicknesses are appropriate for certain soils to still meet the compaction specification. The type of compaction equipment, number of passes, maximum particle size, and loose lift thickness to be used in the Work shall be approved by the Engineer in writing based on an acceptable test fill performance. The Contractor shall outline the proposed procedures for moisture conditioning and fill placement and submit them to the Engineer for review and approval. Test fills shall be constructed within the limits of the Work and shall be conducted to determine the compactive effort required to be applied to a particular material or to an increased lift thickness. The test fill shall be sufficiently wide to support the compaction equipment. The proposed compaction equipment shall be used in the test fill. The number of compaction equipment passes shall be counted, and, at certain numbers of passes, in-place density tests shall be performed by the nuclear gauge method (ASTM D 2922) or sand cone method (ASTM D 1556). This process shall be repeated until a curve representing the number of passes of a select piece of equipment versus the density of a particular material is generated. This information will allow the Engineer to evaluate the optimum density of the fill and the corresponding number of passes. This will establish a guideline for the compaction procedure required during construction. The data to be collected from the test fill shall include the following: Lift thickness of 1, 2, and 3 feet (minimum of three (3) test fills to establish the optimum lift thickness); Amount of settlement after every two (2) equipment passes to a maximum of 25 passes; Gradation and moisture content of the in-place material; and In-place fill density at completion of the test fill by nuclear gauge method (ASTM D 2922) or sand cone method (ASTM D 1556), as approved by the Engineer. A curve showing the change in fill lift settlement versus the number of compaction equipment passes shall be produced from the data. The minimum number of passes to achieve an acceptable compaction will be the number required to achieve 80 percent of the total settlement obtained after no fewer than ten (10) complete passes of the compaction equipment. The lift thickness and minimum number of passes with the specified compaction equipment shall be approved by the Engineer after review of the test fill data. Upon completion of each test fill, a test fill report shall be generated that must include all appropriate documentation pertinent to the test fill, including but not limited to, field and Tetra Tech February

15 laboratory test results, graphics displaying the aforementioned curves, photographs, and a written narrative of the test fill and results. 3.9 Pipe Backfill Material Requirement Pipe Backfill shall meet the requirements of Overliner Drain Fill and extend to one (1) foot over the top of pipe. Pipe Backfill greater than one (1) foot above the top of pipe shall meet the requirements of Site Grading Fill. Backfill material shall be placed in six (6) inch lifts and compacted to a minimum 95 percent of the maximum dry density per Standard Proctor (ASTM D 698) Placement Extreme care should be taken when heavy construction equipment loads cross the pipe trench during construction. If the passage of construction equipment over an installed pipeline is necessary during construction, compacted fill in the form of a ramp shall be constructed to a minimum elevation of five (5) feet over the top of the pipe. Any damaged pipe shall be replaced at the contractor s expense Overliner Drain Fill Overliner Drain Fill shall be used as cover fill over the heap leach pad, as drain rock in the process pond leak detection sumps, or used in underdrain systems as shown on the Drawings. The Overliner Drain Fill material shall be produced from crushing and/or screening operations of approved ore and/or mine waste, and/or from screening of approved sand and gravel aggregate from borrow sources. The Owner shall provide the Overliner Drain Fill material for the leach pad area in stockpiles near the crusher site and/or other stockpile areas as needed. The material shall be free of organic matter and soft, friable particles in quantities objectionable to the Engineer Material Requirement The Overliner Drain Fill for the leach pad liner cover fill shall consist of free-draining, granular material derived from durable, non-reactive rock sources (as approved by the Engineer) with 1.5 inch maximum particle size and a maximum of five (5) percent fines passing the No. 200 ASTM sieve size (0.075 mm). Material testing specific to the heap leach pad liner cover has been performed using Quartz Monzonite Porphyry (QMP). This material gradation and type is also specified for the construction of underdrains. Select Overliner Drain Fill shall be used in constructing the process pond leak detection sumps. The select Overliner Drain Fill shall consist of free-draining, granular material derived from durable, non-reactive rock sources (as approved by the Engineer) with 0.5 in maximum particle size and a maximum of three (3) percent fines passing the No. 200 ASTM sieve size (0.075 mm). The Overliner Drain Fill shall have an operational permeability of 3.3x10-5 ft/sec (1x10-4 m/sec) or higher as determined by ASTM D Placement The Overliner Drain Fill material shall be placed in such a manner as to reduce segregation and construct the zones in accordance with the details and to the lines and grades shown on the Drawings, or as specified by the Engineer. Methods shall be developed on-site for placing the Tetra Tech February

16 material in a manner that will protect the geomembrane and/or pipework from damage and keep compaction of the material to a minimum. The Contractor shall submit an Overliner Placement Plan for approval by the Engineer prior to placement of any materials. Any Overliner Drain Fill material that has received too much compaction shall be scarified to a loose condition without damage to the underlying geomembrane and/or pipework. Overliner Drain Fill placed on the heap leach pad liner shall be placed in a single three (3) foot minimum lift thickness by suitable dozer and truck equipment, as approved by the Engineer, in accordance with the procedure outlined in Appendix G. A thicker layer, minimum of 54 inches, shall be placed over the heap leach pad liner in areas trafficked by haul trucks with a payload capacity of 40 tons or less. A minimum thickness of 36 inches of Overliner Drain Fill shall be placed over the collector and header pipes. No moisture conditioning or compaction of the Overliner Drain Fill is required. Haul truck speeds, braking, and turning during Overliner Drain Fill placement on the heap leach pad liner shall be strictly controlled by the Contractor to prevent damage to the underlying geomembrane and pipework. The thickness of the Overliner Drain Fill shall also be increased in concentrated traffic areas or across collector pipes, as required, to prevent damage to the geomembrane and pipework. Haul traffic on the Overliner Drain Fill surface shall be spread out as much as practical to prevent over-compaction in localized areas. Select Overliner Drain Fill used to construct the process pond leak detection sumps shall be placed in a single lift thickness with no moisture conditioning or compaction. The top surface of the select Overliner Drain Fill material shall be hand leveled in preparation for the top liner system. Any loose particles spilled outside of the backfilled sump area shall be removed from the pond s bottom geomembrane surface to prevent geomembrane puncture Anchor Trench Fill Material Requirement Anchor Trench Fill shall be 3/8 inch minus, well-graded, crushed, or non-crushed granular fill material Placement Anchor Trench Fill shall be moisture conditioned to within plus or minus two (2) percent of the optimum moisture content, placed in the anchor trench in nominal (six) inch lifts and compacted to a minimum of 95 percent of the maximum dry density (ASTM D 698). Compaction shall be accomplished by the use of hand-operated compactors. Care shall be exercised to avoid damage to the geomembrane. The final fill surface shall be graded to drain away from the facility or as directed by the Engineer Riprap Riprap may be required, as needed, for protection against erosion. Riprap shall meet the size gradations and placement procedures provided herein Material Requirement Riprap shall be hard, angular, durable, and reasonably well-graded rock resistant to weathering and to water action, and free of potentially acid-generating material, shale, soil, organic, deleterious, or other objectionable material. The more competent and durable rock encountered on-site during required excavations and mine overburden stripping shall be selected for use as Tetra Tech February

17 riprap. The quality of the material must be approved by the Engineer prior to removal from the processed stockpile. The maximum particle size for the different size riprap shall be equal to the layer thickness and all riprap material shall, in general, contain no fines passing the No. 200 ASTM sieve size as determined by visual observation by the Engineer, or by ASTM D 422. The D50 designation for riprap material refers to the average rock size. Processing may be required to produce the specified material. Los Angeles abrasion tests may be specified by the Engineer on proposed riprap material if the quality of the riprap material is questionable. The minimum abrasion number for riprap material shall be 40 percent. In general, the riprap shall conform to the following gradation requirements; however, minor deviations from these requirements may be acceptable for specific cases, subject to the Engineer s approval. Rock Size D50 = 3 in D50 = 4 in D50 = 6 in D50 = 9 in D50 = 1 ft (% passing) (% passing) (% passing) (% passing) (% passing) 2 foot foot foot inch inch inch inch inch inch inch Placement The Contractor shall haul riprap from the stockpile, spread, and level the riprap to the lines and grades specified on the Drawings, or as specified by the Engineer or Owner at the time of construction. Riprap shall be placed in a manner that minimizes segregation and produces a reasonably well-graded mass of rocks with a minimal practical percentage of voids, as approved by the Engineer. The material shall be placed and distributed such that there are no large accumulations of either large or small rock sizes. Hand placing or rearranging of individual stones by mechanical equipment may be required to achieve this result. Riprap shall be placed in an upslope direction to the sizes and thicknesses shown on the Drawings. Tetra Tech February

18 4.0 GEOSYNTHETICS 4.1 Geomembrane (HDPE and LLDPE) General This section covers the installation of linear low density polyethylene (LLDPE) geomembrane and high density polyethylene (HDPE) geomembrane for the leach pad and ponds associated with the Heap Leach Facility. The geomembrane shall be manufactured in the largest widths and lengths possible to minimize the number of field seams. The Geomembrane Installer shall install the geomembrane materials and appurtenant items in accordance with the Manufacturer's recommendations. The areas to be lined are shown on the Drawings. The exact locations may vary to suit field conditions, as approved by the Engineer. Direct vehicular contact with the geomembrane shall not be allowed in order to prevent geomembrane damage. Motorized equipment will not be allowed directly on the geosynthetics. However, All Terrain Vehicles with tire pressures less than about eight (8) psi are acceptable provided they do not turn sharply, accelerate, and/or brake suddenly. They must not be operated on a liner containing wrinkles that can be folded over. Ultra-violet (UV) sensitive geomembrane (LLDPE) shall be protected from exposure to sunlight until placement. After placement, the LLDPE geomembrane shall be covered within three (3) months of placement, unless otherwise approved by the Owner and warranted by the Manufacturer. The Installer shall notify the Engineer for written acceptance of the completed geomembrane installation prior to covering the leach pad s geomembrane with Overliner Drain Fill and prior to covering the process pond s bottom geomembrane with a geosynthetic. i.e., geonet or top liner. The geomembrane materials installation and testing shall be in accordance with the following sections and shall generally conform to the Geosynthetic Research Institute (GRI) standards GM-13, GM-17 and GM-19, or an equivalent approved by the Engineer Geomembrane Manufacturer s Experience The Geomembrane Manufacturer shall have previously demonstrated the ability to produce the specified geomembrane by having successfully manufactured a minimum of 25 million square feet (sf) of similar geomembrane for hydraulic lining installations. A list of similar containment projects completed in which the manufactured material has been successfully used shall be submitted and is subject to approval by the Engineer Submittal of Engineering Data The Geomembrane Manufacturer is responsible for supplying engineering data and results of QC testing of the geomembrane materials. The Manufacturer shall allow sufficient time in the production schedule to perform the specified QC testing outlined in these Technical Specifications. The results of all required testing shall be supplied at least seven (7) days prior to shipping the materials to Site. The Geomembrane Manufacturer shall furnish the following engineering data prior to construction: QC certificates on the resin used to manufacture the geomembrane. The data submitted on the resin shall include production dates and the results of conformance tests. The resin submittals shall also include a statement that no reclaimed polymer was used. The edges of geomembrane that are trimmed during the manufacturing Tetra Tech February

19 process are not considered reclaimed polymer. All resin shall be of the same type and quality; QC certificates on each geomembrane roll. Each certificate shall be customized for the Project and shall include but not be limited to: the roll and resin batch numbers, production date of the roll, a listing of the QC tests, test method numbers, values specified for the Project, and the QC test results. All tests shall be performed prior to submittal of the QC certificates to the Engineer. Test results for each property specified shall be provided on the QC certificate; and Certification that the geomembrane and extrudate rod or beads are made from the same resin type and have the same properties. The Geomembrane Installer shall furnish the following engineering data prior to construction: Shop drawings with panel layouts and appropriate details along with a time schedule for the geomembrane installation; and An instruction manual which includes the proper storage, handling, deployment, and seaming of the geomembrane. This manual shall be in compliance with these Technical Specifications and any conditions of warranty Delivery, Storage and Handling of the Geomembrane The Geomembrane Manufacturer shall be responsible for shipment of geosynthetic materials. At the discretion of the Owner, conformance testing and a plant audit may be performed by the Engineer and/or Owner prior to shipment. In the event that conformance testing is to be performed, the Manufacturer shall not arrange for transport of the geomembrane until such testing is complete. The Installer or Manufacturer shall provide the Engineer and Owner a schedule for manufacturing the materials at least 14 days prior to manufacturing so that testing and travel arrangements can be arranged. This schedule shall remain firm throughout the duration of the Project. Any proposed changes to the production schedule shall be approved by the Owner. The Engineer shall notify the Manufacturer at least seven (7) days in advance of the intention to perform conformance testing or a plant audit. The geomembrane shall be shipped such that it is not damaged in transport and shall be offloaded in the presence of the Owner or Engineer. The Geomembrane Installer shall be responsible for unloading and storing the geomembrane. Any damage to the geomembrane during the offloading process will be documented by the Owner or Engineer. All damaged rolls shall be separated from undamaged material. The final disposition of the damaged rolls shall be determined by the Owner with input from the Engineer. The Geomembrane Manufacturer shall be responsible for replacing any unacceptable geomembrane at no additional cost to the Owner. Once the geomembrane rolls have been offloaded, they shall be stacked on a prepared surface no more than three (3) rolls high. The surface shall be prepared such that the geomembrane is not subjected to rocks or sharp objects, water, oil, or other deleterious conditions. The geomembrane rolls shall not be placed on pallets. The Geomembrane Installer shall use appropriate equipment to transport the geomembrane from the storage area to the deployment area. This equipment may include a spreader and roll bars and shall not damage the geomembrane or subgrade. Any damage shall be repaired by the Geomembrane Installer to the satisfaction of the Engineer. Tetra Tech February